The carrying capacity of the Ichetucknee Springs and River

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Title:
The carrying capacity of the Ichetucknee Springs and River
Physical Description:
xii, 176 leaves : ill., map ; 28 cm.
Language:
English
Creator:
DuToit, Charles Hill, 1947-
Publication Date:

Subjects

Subjects / Keywords:
Stream ecology -- Florida -- Ichetucknee River   ( lcsh )
Rivers -- Recreational use -- Florida   ( lcsh )
Ichetucknee River   ( lcsh )
Ichetucknee Springs State Park (Fla.)   ( lcsh )
Botany thesis M.S
Dissertations, Academic -- Botany -- UF
Genre:
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis (M.S.)--University of Florida.
Bibliography:
Bibliography: leaves 139-141.
Statement of Responsibility:
by Charles H. DuToit.
General Note:
Typescript.
General Note:
Vita.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 023298531
oclc - 06401514
System ID:
AA00018865:00001


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THE CARRYING CAPACITY OF THE ICHETUCKNE2 SPRINGS AND RIVER


BY

CHARLES H. DUTOIT

























A THESIS -PFESENTED TO THE GRADUATE COUNCIL OF THE
UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE





UNIVERSITY OF FLORIDA


1979














ACKNCWLEEGEMENT.S


I would like to thank my committee members, Dr. Frank

Nordlie and Dr. Ariel Lugo, for their help and interest in

the research, as well as Dr. Gordon Godshalk, who reviewed

the manuscript.

This research was a result of the concern and prelimi-

nary wcrk of Dr. John Ewel, my chairman. Dr. Ewel's guidance

was fundamental to the design of the study, its implementa-

tion, and write-up.

The Florida Department cf Natural Resources, the agency

which administers Ichetucknee Springs State Park, not only

provided a comfortable working atmosphere, but also directly

assisted in the study by constructing fenced exclosures and

cages. I greatly appreciate Major Hardee's cooperation, and

am grate-ful to Captain Krause and CaDtain Barret, as well as

the entire staff, for installing the underwater structures

and helping me in innumerable ways. T thank Lt. Don Younker

for arranging and participating in visits by university and

DNR personnel.
A number of University of Florida students assisted in

the research. I thank Joe Vargo and Bob Rice for the hours

they spent in the water, and Ellen Kane for the hours she

spent at the planimetry table. I was also ably assisted in








both the field and lab by the following students: Charner

Benz, Karen Hokkanen, Doran Pace, David Sample, Barbara

Harris, John Goelz, Patty Kohnke, Robert Somes, and Brian

LaPointe.

I was short of help on several occasions. I am grate-

ful to those individuals who assisted at such times; Dennis

Ojima, a fellow graduate student, and the following members

of the Gainesville chapter of the Sierra Club: Ken Watson,

Steve Dalton, Kathy Haseman, William Girnat, Otho Peterman,

and Tim Pollack.

Alma Lugo and Gary Daught drafted the figures, Joan

Crisman typed the manuscript, and Marilyn DuToit prepared

the plant communities mnap.

The research contained in this thesis was supported

by a research grant to the University of Florida: "Carrying

Capacity of the Ichetucknee Springs and River System,"

P. 0. 10638, J. Ewel, Principal Investigator.















CONTENTS


ACKNOWLEDGE:IMETS . . . . . .

LIST OF TABLES . . . . . . .

LIST OF FIGURES . . . ......


II


. . . . vii
* . . v L


LIST OF COLOR PLATES.

ABSTRACT . . ..


* . . . . . . x


. . xi


INTRODUCTION . . . . . . ..
Geology . . . . . . ..
Hydrology . . . . . . ..


Water Quality . . . ...
Morpholigy of the Ichetucknee
Vegetation . . . . .
Natural History. . . . ..
Cultural History . ......
History of Recreational Use. .
Profile of Park Users . ....
The Carrying Capacity Concept.


River.


1

3
5

7-
7
9
I0
i1
!3


OBJECTIVES.


METHODS . . . . . . .
Base Map . . . . .
Standing Crop. . . . ..
Plant Damage Survey. ......
Plant Resistance . . .
Changes in Plant Cover . .
Plant Recovery . . . .
Response to Repeated Cutting
Fauna Survey . . . .


RESULTS . . . . . .. .....
Base Map ...... ...............
Types and Amounts of Recreational Use
Plant Damage Survey . . . ..
Plant Resistance . . . . .
C-hanes in Plant Cover . . . ..
Experimental Plots ... ..........
EXciosures . . . . . . .
Blue Hole Cages. ..............
Response to Repeated Cuting .
Fauna Survey . . . . . .


20
20
21 -

24
2 L
24
31


S. . . 34
S. . . 34
S. . . 35
. . . 37
37




S79
. . . 31 /











(Continued)


DISCUSSION . . . . . . . .. .
Impact of Recreation on the Plant Communities
of the Headsprings Reach . . . ..
Impact of Recreation on the Plant Ccmmunities
of the Rice Marsh and Floodplain Reach .
Impact of Recreation on the Animals of
the River . . . . . . . .
The Carrying Capacity for Recreation . ....


. 88

. 88

* . 112

S. 124
* ]--4 -


LITERATURE CITED

APPEND I CES


. 139


A. METHODS OF INDIRECT MEAL 7F_: Z;fT . . . .. .142

A-i. PERCENTAGE DRY WE- .. OF
NETTED PLANTS, PLANT DAMAGE SURVEY,


SUMMER, 1973. . ....


. . . . 2


A-2. RELATIO;;3-HI? OF CLUMP BIOHASS AND
LENGTH OF LONGEST LEAF,
Sagittaria kurziana . . . .

A-3. RELATIONSHIP OF LEAF WEIGHT
2AND LEAF LENGTH,
Sagittaria kurziana . . . .

A- NDRPECT AND DIPECT MEA SUREMENT
OF PLANT 3IOLASS IN
EXPERIMENTAL PLOTS . . . ..

B. AMOUNTS OF HOURLY USE AND DAMAGE,
BY SPECIES, PLANT DAMAGE SURVEY,
SUMMER, 1978 . . . . . . .

C. BIOMASS O ACUATIC PLANTS OF THE
ICHETUCKNEE RIVER . . . . . .

D. STA.IDING CROP OF AQUATIC PLANTS IN THREE
REACHES OF THE ICHETUCKNEE RIVER. . .


LANT COMMUNITIES OF THE ICHETUCKNEE RIVER.

BIOGRAPHICAL SKETCH. . . . . I . . . .


. . 1 4



. .. 145


I li 7


147
S. .156 -
. 156 -


* 157 -

1 !76













LIST OF TABLES


Table


1. Water quality of the Ichetucknee Springs ..... 6

2. Common species of the plant communities
of the Ichetucknee Springs State Park . . . 8

3. Regrowth of aquatic plants following
cutting or uprooting . . . . . . ... 57

4. Plant biomass and the number and weight
of invertebrates sampled in three areas
subject to varying degrees of recreational
disturbance . . . . . . . . .. 82

5. Types and numbers of fish in disturbed
(First Dock area) and undisturbed
(Headsprings Exclosure) sections of the
Headsprings Reach . . . . . . . .. 35

6. Recommended carrying capacities . . . .. .128













LIST OF FIGURES


1. Map of Ichetucknee Springs State Park ..... 2

2. Annual park attendance, 1973-74 to 1977-78 . 12

3. Location of netting stations and
experimental plots . . . . . . . 23

4. Location of fenced exclosures, map-remap
sections, and fauna survey sites . . . .. .25

5. Location of cages in the Blue Hole . . .. 29

6. Types and amounts of recreational use,
January-August, 1978 . . . . . . . 3

7. Winter plant damage related to total number
of users and to number of divers .. . . .. .. 8

8. Damage, by species, related to number of
divers, Winter, 1977-78 . . . . .... 40

9. Percent total damage and percent of total
standing crop of species netted in
Winter, 1977-78 . . . . .. . . . 43

10. Amounts of daily plant damage and daily use
in three reaches, Summer, 1978 . . . .. 45

Ii. Amounts of hourly plant damage and use in
three reaches, Summer, 197'S. . . . .... 47

12. Number of users and fractional loss
of standing crop, for three reaches.
Summer, 1978... . . . . . . . 48

13. Percent total damage and percent total
standing crop for plant species in
three reaches, Summer, 1978. . .......... .50,


vii










LIST OF FIGURES
(Continued)


Figure


14. Resistance to tearing and uprooting . .

15. Seasonal changes in plant cover in three
sections of the Headsprings Run . . ..

16. Standing crop and recovery of Sagittaria
leaves following cutting . . . . .

17. Standing crop and clump recovery of
Sagittaria following uprooting . . .

18. Number of Sagittaria clumps counted in
quadrats following uprooring, and standing
crop (no. of clumps) in undisturbed quad-
rats sampled in February and June, 1978.

19. Standing crop and regrowth of Mvyriophylum
following cutting . . . . . ..


20. Change in plant cover, Site A, Headsprings
Exclosure, 6-12-78 to 8-24-78 . . . ..

21. Change in channel profile, Site B, Headsprings
Exclosure, 8-3-78 to 10-12-78 . ......... .

22. Change in plant cover, Second Dock
Exclc3ure '7-25-78 to 10-26-78 . . . .

23. Growth of Zizania and Chara, Second
Dock Exclosure . . . . . . . .

24. Characteristics of Sagittaria leaves sampled
both inside and outside of Jug Cage . . ..

25. Sagittaria colonization and characteristics
of leaves sampled inside and outside of
the Run Cage . . . . . . . . .


26. Sagittaria leaf recovery in plots
subjected to repeated cutting .


27. Amounts of daily use and plant damage,
Headsprings Reach, Summner, 1978 . . . ..


viii


. 1 52


53 -


51


67 -


78


. . 80










LIST OF FIGURES
(Continued)


Wgure


28. .Amounts of hourly use and plant damage
for five survey days, Headsprings
Reach, Summer, 1978 . . . . . . . 91

29. Species damage in the Headsprings
Reach, April to August, 1973 . . .. . . 98

30. Amounts of Sagittaria torn and uprooted
over varying levels of diving activity
and amounts recovered in plots experimentally
subjected to tearing and uprooting . . .. .103

31. Size distribution of Sagittaria clumps
uprooted by divers compared to the size
distribution of clumps sampled from the
Devil's Eye Exclosure, which receives no use .i0

32. Damage Index for three reaches cf the
Ichetucknee River . . . . . ... . . 115

33. Damage Index related to physical
characteristics of the river and
behavioral characteristics of use . . ... .117

34. Fractional loss and fractional recovery
rate of Sagittaria, Myriophyllum, and
Vallisneria . . . . . . . . . 121
















LIST OF COLOR PLATES


Plate


1. Headsprings Exclosure, July and
November . . . . . . . . . . .7

2. Tuber impact on thel Blue Hole . . . . 95

3. Sagittaria bed, April and August, 1973 .... . 97

4. Channel erosion in the Second Dock Area ... .. .11i








Abstract of Thesis Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of the Requirements
for the Degree of Master of Science


CARRYING CAPACITY OF THE ICHETUCKNEE SPRINGS AND RIVER


By

Charles DuToit

June 1979

Chairman: John Ewel
Major Department: Botany


A study was conducted in 1977-78 to determine the types and

amounts of recreational use that the communities of Ichetucknee Springs

and River can sustain without causing irreversible damage. I measured

the kinds and amounts of damage which result from swimming, canoeing,

diving and tubing, and monitored the recovery of aquatic communities.

A carrying capacity, defined as the rate of use at which damage is

equal to the natural ability of each plant community to recover, was

recommended for each type of use.

Tubing is, numerically, the most important form of recreation at

the Ichetucknee Springs; 3000 people per day (the present limit)

regularly float down the River on tubes on summer weekends, and week-

day use generally exceeds 1000. The reach between the Headsprings and

the Blue Hole sustains the greatest impact, both in terms oi channel

and bank erosion and in terms of percentage loss of vegetation. Tram-

pled plant beds support less shrimp and crayfish than healthy beds,

and disturbed areas contain fewer types and numbers of fish than un-

disturbed areas. The middle and lower reaches lose proportionally less

vegetation and, with some local exceptions, are not eroded by recre-









national use. Channel width and depth do not directly account for these

differences, but changes in the behavior of users, who become more

passive as they progress downstream, may be the most important factor.

A limit of 100 tubers per hour is recommended.

In winter, diving groups (2 to > 50 individuals) visit the Park

to snorkel in the River and dive in the Blue Hole. Plant damage in-

creases exponentially as diving activity in the Blue Hole increases.

Crowding in the pool, poor group control, and trampling along the edge

of the Blue Hole run account for this accelerated impact. The Sagit-

taria community, which comprises 75% of the total cover in the Blue

Hole, sustains the greatest damage. Recolonization of disturbed areas

by Sagittaria is very slow in winter; the amount of regrowth in a day

is about equal to the amount of damage caused by 50 divers in four

hours. On busy days, when as many as 100 divers visit the Park, dam-

age may exceed recovery by an order of magnitude. To save the natural

ecosystems in Blue Hole, a limit of 12 divers per hour should be en-

forced.

Swimming and canoeing are minor components of recreational use at

the Park. Although swimming, and the trampling that accompanies it,

result in loss of cover and bottom erosion, this activity is largely

confined to the Blue Hole and Headsprings pool. Canoeing appears to

have little impact onr submerged plant communities; paddles cause little

stem and leaf breakage and practically no -iprccting. If the mount of

swimming and canoeing does not increase substantially, no limit need be

placed on these activities.


Ch. ai i i'
../ Chai r -an
Chairman














INTRODUCTION


The Ichetucknee Springs State Park, located in norTh-

central Florida, is one of the State's most unique resources:

a clear, spring-fed river which winds through hammock, open

marsh, and floodplain forest. The Park, comprising an area

of 910 hectares (2,250 acres), straddles southeast Columbia

County and southwest Suwanee County; the Ichetucknee Piver

forms a natural boundary between the two counties. The

land for the Park was Durchased in 1970 by the State of

Florida from a British mining firm, the Lcncala Phoschate

Company.


Geology

The Ichetucknee Sorings State Park (Fig. 1) lies in the

Coastal Lowlands, a physiographic region defined by surface

elevations less than 30 meters (100 feet) above mean sea

level and locally characterized by karst topography, evi-

dent in the numerous springs, sinkholes, and limestone out-

crops in the area. A geologic section in the area of the

Park would show a surface mantle of sand and clay overlying

a thick bed of limestone, about 915 meters (300] feet) deep,

which rests unconformabiv over Paleozoic basemen- rock. The

up-er layers of limestone seCiment. of la-te Eocene ace, are

ccl --cLively called the OcalA group, which, being highly














ICHETUCKNEE SPRINGS ~
STATE PARK 0 ETU"KE a N
Entry Do IC HE HAD
_1._ 16 KILOMETERS 2.1
0 I/2 I MILE HEADSPRINGS .
-= = ROADS 0 U S. ROUTE @ STATE ROUTE B LUAC. BUE HOLE
\POWER LINE CUT ---PARK BOUNDARY S( f H
--PATHS I
PLANT COMMUNITY KEY ISSION S,
4ANDHILL
I/EVILS EE SPRIN
H AMMOCK _i _(/
MARSH -- -- MSH-
ES SWAMP FOREST I I I
PINE PLANTATION I i.p Ns

LOOOPLAIN ~
REACH




x.I \\

i-, UPo( P ,'nt L /"Pze',Mon

*oysido IPookJ
j__ ^ i-~~and.ng ^ 3 '


Figure 1. Ma of ch-ietucknee Springs State Park.
Map was prepared frcnm aeria! photcgra-hs
i.S.D.A., a3-3)-ag ) and 'J.S.G.S. zopo-
graphic quadrangle (Hildreth, FL, !968).








permeable, forms the dominant water-bearing formation in

north-central Florida. This acuifer is overlain by Miocene

deposits, the Hawthorn and Alachua formations, which con-

sist of clay, phosphatic sand, and discontinuous beds of

limestone. A surface deposit, predominantly consisting of

unconsolidated sand, was laid down over Miocene sediment

during the interglacial periods of the Pleistocene when sea

level ranged 7.5-30 meters (25-100 feet) higher than ar

present (,Meyer 1962).

The major geologic features of the Coastal Lowlands

can be observed at the ichetucknee Springs State Park.

Ocala limestone outcrops in bluffs along the river; Miocene

deposits containing phosphatic ore are exposed in mining

pits in the hammock; and Pleistocene sands are everywhere

evident in the Sandhill community at higher Park elevations.


Hydrology

The Ichetucknee River lies in an ancient basin, he
Tchetucknee Trace, which is roughly defined by the 50 foot

contour level on U.S.G.S. topographic maps of south

Columbia County. Rose Creek and Clay Hole Creek, in the

vicinity of Lake City, form the headwaters of the basin.

Surface flow from these creeks is intercepted by sinkholes

near the town of Columbia which is located about 16 kilo-

meters (10 miles) southwest of Lake City. Here, the cap-

tured surface flow mingles with groundwater and eventua.ll.-.

emerges at the Ichetucknee Springs.








Geologists believe that the Ichetucknee Trace developed

along fracture lines associated with the uplift of the

Peninsular and/or Ocala arch (Meyer 1962).

Ocala limestone outcrops, or lies at or just below the

surface, in the Ichetucknee Trace. Ground water is dis-

charged in areas such as the Ichetucknee Springs where the

piezometric surface, or hydraulic head of the aquifer, is

higher than the topographic surface. Geologists recognize

two sources of discharge in the Ichetucknee Springs:

1. ground water from regions of higher artesian head in

northern Columbia County and surrounding areas, and 2.
local rainfall which enters the aquifer through sinkholes,

limestone outcrops, or permeable sand deposits (Meyer 1962).

The discharge of the major springs of The Park is shown

in Figure I. The average discharge of the Ichetucknee River,

measured at the Highway 27 Bridge, is 10.1 m 3/sec. (353

c.f.s.), which ranks sixth in magnitude among Florida springs.

The minimum discharge recorded over a period extending frcm

1917 to 1972 was 6.8 .3/sec. (241 c.f.s.), which is 33%

below average discharge. The maximum discharge during this

period was 16.4 m, sec. (578 c.f.s.), 611 above the average

flow (Rosenau and Faulkner 1974).

In Columbia County, groundwater rise generally lags

five months behind the period of maximum rainfall, which

occurs during the summer months (Meyer 1962). Small dis-
charge increases, of shcrT duration, result from local

recharge by rainstorms.








Water Quality

The water temperature of the Ichetucknee River remains,

year round, about 220C, which is approximately equal to the

mean annual air temperature of the region. Table i shows

the chemical characteristics of the water from a 1946

analysis (Ferguson et al. 1947). Inspection of this figure

shows that the river water is alkaline (pH 7.7) and that

calcium and bicarbonate are the two most important dissolved

mineral ions. Color was measured to be 0, indicative of the

remarkable clarity of the spring water.


Morphology of the Ichetucknee River

Three reaches can be distinguished in the Ichetucknee

River. The Headsprings, or Ichetucknee Springs, with a

discharge of 1.3 m /sec. (45 c.f.s.), is the source of the

"Headsprings Run,"1 defined as that portion of the river

between the Headsprings and the Blue Hole (Fig. 1), This

reach is relatively narrow and shallow, with an average

width of about 10 meters and depth of 1 meter, and is par-

tially shaded by hammock vegetation growing on the banks.

The section of the river between the Blue Hole and

Mill Springs, about 1.6 kilometers (1 mile) in length, is

called the "Rice Marsh." Discharge from the Jug Springs at

3,
Blue Hole (about 2.4 m i/sec.), Mission Springs ,(1. mii/sec.),

and Devil's Eye Spring considerably strengthens the river

1 The ''Heasprings Reach," a term used throughout this
report, includes the "Headsprings Run" and the
Headsprings an:d Blue -ole.










Table 1. ',ater quality of the Ichetucknimee Springs. Data
are from Ferguson et al. (1947).


iCHICAL ANALYSIS
May 17, 1946

Parts Per Million

Silica (SiO2) 9.1

Iron (Fe) .03

Calcium (ca) 58

.Mai-nes iuLm (Mg) 6.6

Sodium (Na) 3.1

Potassium (K) 3

Bicarbonate (HCO3) 200

Sulfate (SO4) 8.

Chloride (Cl) 3.6

Fluoride (F) .1

Nitrate (NO3) 1.0

Dissolved Solidsa 1 88

Total Hardness as CaC0 172

Carbn Dioxide (CC2) 6

Other Measurements

Color ) 0

pH 7.7

Specific Conductance KxlO5 at 25C) 32.9

a. In a l.92-7, analysis by U.S. Geological Survey, dissolved solids
measured 170 -g/1 (Rosenau and Faulz:er 1974).

b. Color units are not specified by Ferguson at al. Their measurement
is based on a graduated scale of colored disks and is presented here
to indicate the relative clarity of the water. Some swamp water
measures 200C or more on the colored diask scale.








flow in this reach. A short distance below Blue Hole the

river widens to about 60 meters with an extensive marsh of
wild rice Zizania auatica, bordering an open channel, which

is 15 to 20 meters wide and about 2 to 3 meters deep.

The "Floodplain Reach" is that portion of the river

between Mill Springs and the point of discharge of the

Ichetucknee River into the Santa Fe River. In this reach

the river is 15 to 20 meters wide and 1-2 meters deeD and

is bordered by floodplain forest and limestone bluffs.


Vegetation

Three life forms of vascular plants are common in che

open channel and floodplain of the Ichetucknee River:

submerged macrophytes in the open channel, emergent macro-

phytes in the marsh, and arboreal vegetation in the flood-

plain swamp. Table 2 shows the common species of the river

and the upland communities. Sandhill vegetation occupies

about 273 hectares (675 acres), or 30% of the Park area, and

grows on Pleistocene sand deposits at higher elevations o

the Park. Hammock trees grow in the rich calcareous soil of

river banks and cover about 590 hectares (1460 acres), or

65% of the total area. River plants and floodDlain forest

occupy about 5% of the Park.


Natural History

The Indian word ?T chetucknee" means "beaver ocnd."

Ironically, beaver are rarely observed in the Park, and in

fact, had not been seen for decades until the fall of 1977









Table 2. Common species of the plant communities of the
Ichetucknee Springs State Park.



Sandhill


Pinus palustris
Quercus laevis
Quercus margaretta
Aristida strict


longleaf pine
turkey oak
sand-post oak
wire grass


Mesic Hammock


Quercus virginiana
Quercus hemisphaerica
Magnolia grandiflora
Carya glabra
Persea borbonia
Ilex opaca
Acer barbatum


live oak
laurel oak
southern magnolia
pignut hickory
redbay
american holly
florida maple


Swamp Forest


Taxodium distichum
Nyssa biflora
Nyssa aquatic
Acer rubrum


bald-cypress
blackgum
water tupelo
red maple


Aquatic


Sagittaria kurziana
Vallisneria americana
Zizania aquatica
Chara sp.
Myriophyllum heterophyllum
Ceratophyllum demersugm
Ludwigia repens
Nasturtium officinale
Najas guadalupensis
Cicuta maculata
Pistia s-ratoites
Fontinalis sp.


eel-grass
tapegrass
wild rice
musk-grass
foxtail
coontai!
red ludwigia
watercress
southern naiad
water-hemlock
water-lettuce
water-moss








when one was observed in the Headsprings Run during the

early days of our research. The long absence and recent

return of the beaver is only one of the interesting features

of the natural history of the Ichetucknee Springs. A monkey

has been reported; wild turkey, bobcat, and deer are common-

ly seen in the woodlands, and a great variety of birds and

fish, as well as otter, inhabit the marshes and river.

Less conspicuous features of the Springs are Eocene

fossils of mollusks, echinoderms, and foraminifera that are

embedded in submerged limestone banks and emergent bluffs.

The bones of terrestrial vertebrates of the Pleistocene

have been found in alluvial deposits along the Ichetucknee

River. The remains of an extinct bison were unearthed

during the construction of a canoe ramp in 1973, and the

bones of mammoths, mastodons, and a Pleistocene lion, Felix

atrox, have been recovered at the Park.


Cultural History

Anthropologists believe that the Utina Indians, a tribe

of the Western Timucuans, lived in the area of the Park in

prehistoric times. In 1950, John Goggin of the Florida

State Museum, excavating a refuse mound, unearthed evidence

of a Spanish-Indian contact on the banks of Ichetucknee

River. The recovery of both European and Indian artifacts.

including a lead cross and ceramic vessels, suggested that

a Spanish church formerly occupied this site, now known as

Mission Springs UDeagan 1972). The remains cf a grist mill








and earthworks at Mill Springs indicates more recent

occupation of the riverbanks.


History of Recreational Use

The type and amounts of use of the Ichetucknee River

and woodland has changed considerably from pre-Park days to

the present. Ferguson et al., in a 1947 publication, The

Springs of Florida, relate that the Headsprings was used

for watering stock, as well as for swimming and picnicking.

Fishermen and hunters frequented the river and uplands and

camped on the wooded river banks. The river was additional-

ly subject to unregulated use by local residents and college

students, whose beer cans were conspicuously evident prior

to a cleanup by the State. Under the administration of the

Department of Natural Resources, the Park has instituted a

number of regulations designed to limit environmental abuse,

and has developed facilities to increase access and visitor

comfort. A user now pays a 25 admission charge; parking

for cars and buses is provided at the Headsprings area, and

trails and docks provide easy access to the river. Camping

is prohibited, and visitors are not allowed to carry food

or beverages on the Ichetucknee River. A shuttle bus,

operating from the Wayside Park on Highway 27, transports

users back to the Headsprings area at the end of a run.

The Ichetucknee Springs under State ownership has

become an extremely popular resource; its facilities, clean-

liness, and recreational opportunities appeal to family








groups, community organizations, tourists, dive clubs, and

the general public. As shown in Figure 2, the amount of

Park use has increased considerably during this decade. The

amount of annual use remained fairly constant until 1976,

when there was a 35% increase (about 50,000 users) over the

previous year's attendance. On July 4, 1977, nearly 5000

tickets were sold at the main gate. This was the largest

amount of daily use ever recorded.


Profile of Park Users

In 1974 and 1975 a survey was conducted by the Florida

Department of Natural Resources at the Ichetucknee Springs

State Park to investigate the impact of crowding on a user's

enjoyment of the experience. In addition to providing infor-

mation on its primary objective, the survey furnished a

sociological sketch of Park users.

Male visitors outnumber female visitors by a factor of

two or more. Approximately 45% of the Park users are

between the ages of 19 and 26; 10% are under 18, and about

25% between 26 and 35. The city of Gainesville, which has

grown rapidly during this decade, is the largest single

source of users (35% of total), followed by Jacksonville

(about 20%), and the Fort White area (about 10%). An inter-

esting survey statistic shows that, on the average, there

are nearly nine individuals per tubing party. This fact is

likely accounted for by the large family groups, college

fraternities, and community organizations which regularly

visit the Park.














ANNUAL ATTENDANCE


1973-74 1974-75 1975-76 1976-77 1977-78

YEAR


Figure 2.


Annual park attendance, 1973-74 to
1977-78. Data are from annual attendance
records which are based on monthly use
totals from July through the following
June.


300.



250-


200-



150-



100.


50-



0






13


The Carrying Capacity Concept

The signs of environmental deterioration that have

accompanied increased use of the Park in recent years have

prompted the Department of Natural Resources to impose a

limit of 3000 users per day, as well as to sponsor research

on the "carrying capacity" of the Ichetucknee Springs and

River. The concept of a recreational carrying capacity has

become increasingly popular with resource managers; however,

it is not always clearly defined, and has been difficult to

apply. Lime and Stanky (1971, p. 175), in a review of the

development of the concept, provide a good definition:

The recreational carrying capacity is the
character of use that can be supported over a
specified time by an area developed at a certain
level without causing excessive damage to either
the physical environment or the experience of
the visitor.

In their definition, the authors emphasize the need for a

multi-dimensional concept which includes three basic consid-

erations: 1. user satisfaction, 2. environmental impact,

and 3. the objectives of resource managers. The theoretical

sources and applications of research in each of these three

areas is summarized in the following discussion.


User Sat'isfaction

The most comprehensive study to date on user satisfac-

tion is the nation-wide survey conducted by the Outdoor

Recreation Resources Review Commission (ORRRC 1962) on the

preferences and perceptions of users of State anrd National

Parks. A number of other studies on visitor attitudes have








been conducted on a regional or local scale, such as the

study by Lucas (1963) on the perception of "wilderness" by

different types of users of the Boundary Water Canoe Area in

northeast Minnesota, and locally, the survey conducted at

the Ichetucknee Springs State Park in 1974-75. Briefly sum-

marized, the results from these surveys demonstrate that

Park users vary greatly in their recreational preferences, in

their perception of environmental quality, and in their

tolerance to interaction with other recreationists.

The recreational carrying capacity, from the viewpoint

of user satisfaction, has been defined as "the maximum num-

ber of use-units (people, vehicles, etc.) that can utilize

the available recreational space at one time for some

activity while providing a 'satisfactory' experience for the

user" (Lime and Stanky 1971, p. 174). The most popular

application of this definition is the "space standard," a

concept developed by the U.S. Forest Service which defines

the amount of topographic space that a wilderness user

needs in order to have a satisfactory day of recreation.

The "space standard" for wilderness areas of National

Forests is 3 acres per person per day (Douglas 1975).

The assumptions implicit in the concept of a "space

standard" are similar to those inherent in the theory of

the carrying capacity of natural populations. According to

this theory, introduced by Verhuist in the 18th century,

and mathematically formalized by Lotka, there is a limit








to the growth of natural populations due to density depen-

dent interactions and shortages of available resources

(Krebs 1972). The concept of a carrying capacity for user

satisfaction is analogous to the concept of a growth limit

on natural populations in the sense that a "space standard"

ideally defines a level of use that an area can sustain

above which density-dependent interactions (user-user

contact) or environmental deterioration (recreational con-

sumption of the resource) strongly detract from the enjoy-

ment of the recreational experience. Although a "space

standard" based on user satisfaction is a useful concept,

it has a fundamental weakness. Lime and Stanky comment:
"space standards based on user satisfaction have generally

failed to incorporate the level of use the physical environ-

ment can tolerate over a given time before serious damage

results" (Lime and Stanky 1971, p. 175).


Recreational Impnact on the Resource

The majority of research on impact of recreational use

on natural ecosystems has been concerned with the effect of

hikers, campers, and picnickers on the vegetation and soils

of State and National Parks. Investigations of recreational

impact on lakes and rivers have been primarily limited to

studies on the environmental effect of outboard motor dis-

charge and watershed pollution (Stanky and Lime 1973).

Basically, two approaches are used in research on recreational

impact. One approach involves monitoring use levels and








measuring environmental damage in actual recreational

situations. The other measures environmental damage under

controlled levels of simulated impact, such as Wagar's

(1964) use of a tamp to simulate trampling on foot paths.

Recreational studies may be short term, such as Burden and

Randerson's (1972) study on the effect of seven days of

recreational use on a newly developed trail, or long term,

as exemplified by Lapage's (1967) three-year study on plant

cover changes at a New Hampshire campground. Historical

investigations, such as Gibbensand Heady's (1964) work at

Yosemite, use time-series photographs, naturalist writings,

survey reports, and interviews to determine environmental

change over extended periods of time.

The results of recreational impact studies have been

used by the U.S. Forest Service to formulate a Ground Cover

Index, which equates ground cover at a campsite with:

1. the amount of recreational use in the area, and 2. site

characteristics, such as slope and depth of B horizon.

A problem with recreational impact studies is the

element of uncertainty about the level of damage that a

resource can tolerate without causing irreversible deterio-

ration of a site. The consideration of this problem in*

other fields of ecology has led to the development of such

concepts as ecosystem stability, resistance, and resilience

(Bishop et al. 1974). Simply stated, these concepts are

concerned with: 1. the ability of an ecosystem to resist








perturbation, 2. the rate and direction of recovery follow-

ing disturbance (resilience), and 3. the threshold limit,

or carrying capacity, beyond which the system is unable Tc

return to its original condition.

Concepts of this nature underlie a great deal of carry-

ing capacity research and are implicitly acknowledged, if

not openly recognized, in many resource management decisions.

Wagar (1964), in his tamp experiments, found that the

"resistance" of terrestrial vegetation to trampling was

partially a function of life form; grasses and woody vines

are generally less vulnerable to trampling than dicotyledo-

nous herbs. Resource managers commonly use a variety of

techniques, such as paving heavily-used walkways and ferti-

lizing and irrigating, to increase the "resistance" of a

site (Lime and Stanky 1971). In England, Schoefield (1967)

determined the "carrying capacity" of a dune walk to be 7500

users per season. Increasing the amount of use beyond this

threshold limit resulted in soil exposure and dune erosion.

Schoefield also considered the "resilience" of this dune

system when he estimated that an eroded footpath would

recover in four years if protected from further use.


Objectives for the Management of Recreational Resources

The management objectives for a recreational area

should be ideally based on 1. user demands and preferences,

2. park philosophy, and 3. the durability of the resource.

The park manager's problem of balancing recreation with








preservation is similar to that of fisheries or agricultural

enterprises where overexploitation may deplete the resource.

The concept of "optimum sustained yield" as a management

objective for the fisheries and agricultural industries may

be just as applicable to the management of recreational

areas. The "sustained yield" concept is implicit in the

following statement by the Outdoor Recreation Resources

Review Commission (1962, p. 1) on the goal of maintaining

"site quality" in recreational areas.

site quality. .the extent to which an area
provides its intended amounts and kinds of
recreation opportunities while being main-
tained in a long term productive condition.














OBJECTIVES


The objective of this research was to determine the

amount of environmental change that results from varying

types and amounts of recreational use. Information of this

nature should greatly aid Park management in defining a

carrying capacity that is consistent with their objectives

of preserving the resource and meeting the public demand for

recreation. To fulfill the stated goal of this research,

answers to the following questions are provided.

1. What is the relationship of plant damage to:

--the number of users?

--the type of use?

--the distribution of use, both daily and

seasonally?

2. What areas of the spring system and river, and

which plant communities, are most disturbed by

recreational use?

3. What is the rate and kind of vegetation

recovery following disturbance?

4. What impact does recreational use have on the

animals of the springs and river?

5. Is the damage to plant and animal communities

reversible or irreversible?















METHODS


Base Map

The Ichetucknee River was mapped to determine the

distribution of aquatic macrophytes. The method of mapping

varied over the river, depending on the width and deoth of

the major reaches. The Headsprings Run, about 500 meters in

length, was mapped in 10-meter sections using two fiberglass

meter tapes and a meterstick. One meter tape was stretched

across the run, perpendicular to the main channel. A second

tape was stretched parallel to the first, 10 meters down-

stream. The plant beds in each section were mapped by a

wading observer who used the tapes to chart bed position and

the meterstick to measure the dimensions of the bed. Depth

was also measured in each section and the type of bot-com

sediment noted. The Blue Hole pool and run were mapped in

a similar fashion, except the tapes were 5 rather than 10

meters apart.

The portion of the river extending from the Blue Hole

outlet to the Wayside Park Landing was mapped using a boat,

as the channel was too deep to wade. A 20-meter anchor

rope, marked at 5-meter intervals, served as a position

reference by which an underwater observer charred the major

plant beds. An assistant working from the boat 7ock deozh








soundings, measured river width with extension poles, and

recorded the compass direction of the main channel in each

20-meter section.


Standing Crop

Samples of each of the major plant species were clipped

or uprooted from quadrats of varying sizes. The samples

were returned to the lab, oven dried (three days at 70C),

and weighed. The standing crop for each species was esti-

mated by multiplying its sample weight/m by its cover value
2
(m ), which was measured by planimetry of the base map.


Plant Damage Survey

The one-way flow of a river provides a researcher with

an opportunity to directly measure the impact of trampling

on aquatic vegetation. The relationship of plant damage to

the amount of use can be estimated by counting users and

collecting river drift simultaneously. This method was used

throughout the study to measure the amount of damage to

river plants over varying types and levels of recreational

use.


Winter Survey

The impact of winter recreation was measured by sampling

plant damage both on busy weekends and quiet winter weekdays

over a period extending from December, 1977, to March, 1978.

On sampling days, the researcher and his assistant collected








drift for a four-hour period from a point in the river

located just below the Blue Hole outlet (Station 1, Fig. 3).

Handnets were used to retrieve plant clumps and fragments,

and recreationists entering Blue Hole or passing the collec-

tion station were counted and categorized according to type

of use (scuba diver, snorkler, cancer, tuber, or swimmer).

The netted material was returned to the lab, sorted accord-

ing to species and type of damage (torn or uprooted), oven

dried (three days at 70C), and weighed.


Summer Survey

During the summer (April through August), when recre-

ationists range over the entire springs system and river,

plant damage was sampled one day each month from three

different stations situated at the downstream end of each

major reach. At Station 1, located just below Blue Hcie Run

(same station used in winter survey), plant material was

netted by two wading assistants, while a third counted and

categorized users. At Stations 2 and 3, located at Mill

Springs and just below Wayside Park Landing respectively,

drift was netted from either canoe or raft, as the depth of

the channel prohibited wading. To assess the impact of rate

of use (number of users per unit time), plant material was

netted and the number of users recorded on an hourly basis

throughout a sampling day.

At the end of a survey day, all the collected plant

material was returned to the lab, and, as was done in the




















HEADSPRING REACH

Station






RICE MARSH




Station 2


Spring
Cedar Head Spring


Blue Hole Spring



SMission Sprnqs

Ceviis Eye Soring
SagittOria


M'll Spring


FLOODPLAIN REACH


Slotion 3


Charo


Figure 3. Location of netting stations and
experimental plots. The three netting
stations are identified by number, the
experimental plots by genus name.








winter survey, sorted according to species and type of

damage. As the available drying ovens could not accommodate

the large volume of vegetation, the sorted plants were

spread on screens and drained for an hour before taking a

fresh weight. Several small samples (a handful) of each

species were oven dried (three days at 70C) to determine

a dry weight equivalent for the fresh weight measurements.


Plant Resistance

A simple experiment was devised to test the ability of

a species to resist tearing or uprooting. One end of a

nylon string was tied to a plant stem just above the soil

surface. The other end was secured to a spring aligned with

a meterstick. Resistance was measured as the maximum amount

of spring stretch (in cm) at the point of tearing or

uprooting.


Changes in Plant Cover

To determine seasonal changes in plant cover, three

sections of the Headsprings Run (Fig. 4) were mapped in

November-December, 1977, remapped in April, 1978, and mapped

again in August, 1978. The method was the same as was used

in preparing the base map of the Headsprings Run: tapes,

10 meters apart, were stretched across the run, and plant

bed positions and dimensions charted on graph paper.


Plant Recovery
Several methods were used to assess the rate of vege-

tation recovery following disturbance. One method involved















Mt
HkIEADSPRING RUN


M.S.Q M SR


HEADSPRING
POOL


5ECONO


THIRD DOCK


METERS
0 5 10


Figure 4.


Location of fenced exclosures, map-remap sections, and fauna survey sites.
The exclosures are indicated by dashed lines (---), and the map-remap areas
by solid lines (--), with M.S. H, M.S. Q, and M.S. R identifying the
specific map sections. The fish survey sites are indicated by lines with
terminal bars ([--- ), and the invertebrate survey sites by the letters
X, Y, and Z. Also included are the location of the i2 quadrats in the
Second Dock Exclosure, and the areas in the Hleadsprings Exclosure (sites
A and B) where channel closure was measured.








monitoring the recovery of sample plots which were experi-

mentally subjected to injuries similar to the kinds of

damage (tearing, uprooting) caused by recreational use. A

second method involved the measurement of plant regrowth in

trampled beds, which were protected from further disturbance

by fenced exclosures. A third way was to monitor plant

growth in cages situated in areas of heavy recreational use.


Experimental Plots

Basically, two types of treatment were used to simulate

the types of injury which result from trampling: 1. Plant

stems and leaves lying in the water column above a quadrat

were cut back to the substrate level. 2. All rooted Dlanr-s

lying within the boundaries of a staked quadrat were pulled

from the substrate. Appendix A-4 describes the methods used

to measure the regrowth of a number of plant species used in

this experiment.


Exclosures

The Park staff constructed two fenced exclosures in the

Headsprings Run (Fig. 4). One exclosure, situated between

the Headsprings pool outlet and the First Dock, protected

an area that had been previously subjected to a moderate

degree of trampling. A second exclosure was erected on the

eastern side of the run opposite the Second Dock. Prior to

fencing, the riverbed in this area had been extensively

trampled by wading tubers.








Headsprings Exclosure. Vegetation recovery was moni-

tored in two sections of the reach protected by the Head-

springs Exciosure. At Site A (Fig. 4), a 5-meter-long

section of the run lying immediately above the downstream

fence, the dominant plant beds were mapped on June 12, 1978,

and on August 24, 1978. An open grid was laid out to provide

a fixed reference for measurement of the beds. Nylon strings,

marked at meter intervals, were stretched above the channel

between pipes which were aligned in opposite pairs, one

meter apart, along the banks. The position of plant beds

was measured by running a plumb bob perpendicularly from the

marked strings down to the submerged beds.

A second section of the Exclosure, Site B (Fig. L.) was

used to measure channel closure. A meter tape was stretched

underwater from a pipe sunk in the channel floor to a second

pipe sunk 10 meters downstream. Channel width was measured

with a marked rod, which was held perpendicularly to the tape

at each meter interval over this section. Measurements were

taken on August 3, 1978, and October 12, 1978.


Second Cock Exclcsure. A heavily-trampled river bed,

protected from further disturbance by the Second Dock

Exclosure, was sectioned into eight I m units to facilitate

detailed measurement of plant cover changes (Fig. 4). In

each unit, stakes were fitted tightly into the corners of
L
a 1 m quadrat and sunk permanently in the underlying

substrate. Cover was measured on July 25, September 6, and









October 26, 1978, by positioning the quadrat, which was sub-

2
divided into one hundred 0.01 m units, over the stakes and

mapping the areas occupied by the constituent species in

each quadrat.

In a separate section of the exclosure, the same method

was used to monitor the recovery of Zizania plants in a 1 m2

quadrat (Fig. 4). In addition to mapping cover, plant size

was noted by measuring the length of the three longest leaves

of each Zizania plant in the quadrat.


Cages

Two cages were installed in the Blue Hole (Fig. 5).

One cage, secured to the bottom in late May, was situated

in the channel 10 meters downstream from the Jug, the spring

water outlet in the Blue Hole. A second cage, installed in

June, was situated about 5 meters from the Jug, on the sou-cth

side of the Blue Hole pool. Both cages were made of hurri-

cane fencing and had the same dimensions: 1 x 1 x 1.75

meters.


Run Cage. The cage in the channel, designated Run Cage,

enclosed an area that was vegetated in part by Sagittaria,

the remainder being open sand. On May 29, shortly after

installation, the channel-ward edge of the Sagittaria bed'

was marked with stakes to provide a reference for future

measurement of vegetation outgrowth. Substrate level was

measured on the stakes, which had been marked off at

centimeter intervals.









THE BLUE HOLE
AUGUST, 1978


Figure 5. Location of cages in the Blue Hole.








On July 6, about five weeks after installation, the

bottom of the Run Cage was photographed to determine changes

in plant cover. The substrate level was also measured to

determine how much sediment was deposited during this period.

At the end of the summer, the Sagittaria growth that

had colonized the open sand area during the recovery period

(May 29 to September 12) was mapped and then harvested

(whole plants) to determine the net increment of Sagittaria

cover and biomass in the Run Cage. Additionally, samples

of Sagittaria leaf blades were clipped from two quadrats,

one placed inside, the other outside the Run Cage.

In the lab, the harvested Sagittaria plants were

measured and oven dried (70C) to constant weight. The

leaves from the inside-outside samples were counted, measured,

and then oven dried.


Jug Cage. The cage situated on the south side of the

Blue Hole Pool, called Jug Cage, covered a portion of a

Sagittaria bed that had been subject to heavy disturbance

prior to protection. On July 6, about a week after the cage

was installed, leaf blades were clipped from quadrats placed

inside and outside the cage. Two months later (September

11), two new quadrats were cut to determine changes in commu-

nity structure (plant height and biomass) in both disturbed

and caged sections of the Sagittaria bed. Leaves sampled in

July were oven dried (70 0C) to constant weight. Leaves from

the September samples were counted and measured prior to dry

weight determination.









Response to Repeated Cutting

Sagittaria kurziana, the most abundant plant in the

Ichetucknee River, was used for an experiment on the effect

of repeated disturbance on plant growth. Three replicate

plots were used for each of three treatments applied to

Sagittaria plants growing in a protected bed within the

Devil's Eye Exclosure. All nine plots were subjected to the

same kind of disturbance: the blades of all Sagittaria
2
plants rooted within a quadrat (0.125 m ) were cut back to

the substrate level. The variable treatment factor was the

number of times a set of plots was cut during a four-month

interval extending from February 20 to June 13, 1978. One

set was cut every two to three weeks, a second set was cut

every four to six weeks, and the third was cut only once,

at the start of the experiment. On June 13, all nine sample

plots, representing three treatments, were recut. The

subsequent regrowth was harvested approximately five weeks

later on July 21 and oven dried (70C) to constant weight.


Fauna Survey


Invertebrates

On August 5, 1978, a survey was conducted to determine

the numbers and biomass of invertebrates inhabiting both

disturbed and undisturbed plant beds. Figure 4 shows the

location of three sampling sites in the headwaters area of

the Headsprings Run. The first site, located inside the

Headsprings Exclosure, had been protected from trampDling for









more than two months prior to sampling. The second site,

in the Second Dock Exclosure, had been undisturbed for about

three weeks prior to sampling. The third site, located just

downstream from the Third Dock, was an area that had been

subjected to trampling right up to the time of sampling.

To minimize environmental variability, other than the

degree of recreational disturbance, all sampling was done

in Chara beds growing at shallow depths (less than 1 meter)

along the edge of the channel. A stove pipe (diameter =

15.8 cm) was used to extract two sample plugs of plant

material at each of the three sites. The pipe, sharpened

before use, was thrust down through a Chara bed into the

sediment below. The sample plug, containing plants, animals,

and sediment, was lifted from the substrate with a flat-

bottomed shovel and transferred to a fine-mesh net. The net

was agitated in the water to remove fine silt and debris,

then inverted into a plastic bag and returned to the lab.

In the lab, the sample material was placed in white

enamel pans, and all animals visible to the naked eye were

picked out and sorted into species. The animals were pre-

served in 5% Formalin, and the plant material was refriger-

ated until the sorting of all sample material was complete.

The plant material was then oven dried (700C) to constant

weight, and the animals drained and air dried ( hour)

prior to counting and weighing.









Fish

To assess the impact of recreational trampling on the

fish populations of the Headsprings Run, a survey was con-

ducted on August 10, 1978, and October 13, 1978, to deter-

mine the types and numbers of fish in: 1. a disturbed area,

the reach below the first dock; and 2. a protected area, the

Headsprings Exclosure (Fig. 4). At each study site, a 20-

meter rope was secured to an immovable object (dock piling

or fence) and floated downstream. An observer, with face

mask and underwater slate, slowly pulled himself upstream

along the rope, recording in his progress all fish seen

along the run. Both the protected area and disturbed area

were surveyed twice, in alternate runs, on each survey day.

The presence of other conspicuous organisms, such as cray-

fish or turtles, was also noted.














RESULTS


Base Map

The Base Map (Appendix E) shows the plant cover in each

of the three reaches of the Ichetucknee River. Although

an average of 25% of the channel in the Headsprings Run

is vegetated, there is great variation in the amount of

cover over the course of this reach. In areas subject to

heavy recreational trampling and/or shading, plant cover may

be as low as 1%. In open, less disturbed sections, cover

values measured as high as 80%. Chara sp. and Zizania

aquatica are the dominant plans in the Headsprings Run,

each comprising about 25% of the total plant cover in this

reach.

Aquatic plants cover approximately 40% of the bottom in

the Blue Hole pool and run. Sagittaria kurziana is the

dominant species in this area, accounting for S0% of the

extant cover. Sagittaria is notably absent at Ichetucknee

Spring and comprises only 3% of the plant cover in the

Headsprings Run.

In the Rice Marsh, about 60% of the channel bottom is

vegetated. Over small stretches of this reach, however,

cover may vary from 25% to G0%. Sagittaria is the dominant

plant in the Rice Marsh, accounting for 55% of the total









plant cover. Zizania and Chara cover less area, each com-

prising about 15% of total cover. The remaining vegetated

areas are comprised of Myriophyllum and Vallisneria, each of

which accounts for 5% of plant cover, and Ludwigia and

Nasturtium, which form small patches along the edge of this

deep reach.

The average amount of plant cover in the Floodplain

Reach, measured over 66 map sections, is 22%, which is simi-

lar to the average for the Headsprings Reach. The varia-

bility of cover in this lower reach is, however, much less

than that of the Headsprings Reach. In the Floodplain Reach,

the lowest cover in one section is 14% (lowest cover in the

Headsprings Reach is 1%). The maximum amount of cover is

32% (maximum cover in the Headsprings Reach is 80%).

Myriophyllum and Chara are the two most common plants of the

Floodplain Reach, accounting for 37% and 30% of total cover,

respectively. As the Base Map shows, Sagittaria (20% cover)

and Vallisneria (10% cover) grow along the edge of the chan-

nel in this reach.


Types and Amounts of Recreational Use

Figure 6 shows the types and amounts of monthly recre-

ational use from January-August, 1978. It is evident that:

1. weekend use is much greater than weekday use, usually by

a factor of three or more and 2. the number of visitors

increases substantially during the warm summer months. On

the average, about 150 people visited the Springs on a














[] Weekend use L0 Weekdoy use
3000 A 1
W





8o
(A

2000
L
00U








[] oi., ']o. .:. !~me.DT
0. Ell.
90
S10 0O 1 '' .





,n 40 V:^




Fiue6 ye n aont of reretin l use Jur-uut
20
JanuAory I Februory I March I April I I Moy June Jul Augusi







Dier [] -Canoe s E Swmmr In Tuer

Fiur 6. Tye an amut of reratoa use daur-u






1978. A. Amounts of use based on park attendance
I8 0- s,











records. a B. Percent of -total use foJ each type of

recreational activity. Data are based on user counts
from the plant damage survey, o.








winter weekend day in January. By April, average weekend

use had risen to nearly 1000 visitors per day. By midsummer,

the number of weekend visitors consistently reached 3000 per

day, the present Park limit on recreational use.

Figure 6B shows that divers constitute about 85% of the

total number of winter users. Canoes account for about 10%,

and swimmers and tubers comprise 5% of the total winter use.

The onset of warm weather in April signals the start of

the tubing season. The proportion of tubers jumped from 10%

of total use in March to 60% in April, and continued to

increase during the spring. By June tubers accounted for

95% of total recreational use. This level of tubing activity

was sustained throughout the summer months.


Plant Damage Survey


Winter Survey

The relationship of winter plant damage to: 1. total

number of users (includes all types of recreationists) and

to 2. number of divers (includes only scuba divers and

snorklers) is shown in Figure 7. Examination of this figure

shows that the relationship of damage to rotal number of

users is not consistent. This lack of relationship, in

effect, is best explained by the observation that canoeists,

who were included in the determination of total amounts of

use, generally have very little impact on the submerged

plant communities of the river. Underwater assistants on








700-

600-

500-

400-

300-

200-

100-

01
0


DIVERS (no./day )


. Figure 7.


Winter plant damage related to total number of
users and to number of divers. Relationship of
plant damage (y) to number of divers (x) is
described by the exponential equation,
y = 4.4e004x (r2 = 0.39).
The notation "J.7" indicates the data point
for January 7 which is mentioned in the text.


* 0


40 60 80
ALL USERS (no./day)


= 700

S600

> 500

400
0
u 300

^ 200

100.
z

a. 0


J. 7
*


I00


120


100


120








a number of occasions, watched canoes pass over plant beds.

Although paddling stirs the surface of the beds, it results

in very little stem or leaf breakage, and practically no

uprooting. On days when canoeists constitute a large pro-

portion of total use, as occurred on January 7 (66 canoeists,

24 divers, 15 tubers, and 4 swimmers) plant damage was expec-

tedly very light.

The relationship of damage to number of divers (Fig.

7), shows that plant damage predictably increases as winter

diving activity increases. As the number of divers increases,

the amount of tearing and uprooting increases exponentially.

Less than 50 dry grams of plant material was netted on days

when less than 40 divers were counted. On busier sampling

days, when the number of divers ranged from 60 to 100, the

weight of the netted material ranged from 200 to 500 dry

grams, a disproportionate increase relative to the amount

of use.


Species damage. Figure 8 shows the amounts of species

damage over varying levels of diving activity. One species,

Sagittaria kurziana, accounted for 40% of the total weight

of plant material collected during the winter survey. The

relationship of Sagittaria damage tc the number of divers is

similar to that of total plant damage and divers in that

impact accelerates when more than S0 divers use the resource.

Damage to the other species is less predictable over varying

levels of diving activity. WThen the amounts of damage to













WINTER 1977-78
Soagietanro nu anO

A



0'


0_---


* Totalo damag(--)
0 Torn t-)
A Uprooted --)


/
/
/ 0


0 20 40 60 80 100


DIVERS (no./day)


Figure 8.


Damage by species, related to number of divers,
Winter, 1977-78. For Sagittaria kurziana, the
relationship of damage (y) to number of divers
(x) is described by an exponential equation:

number of clumps uprooted, y = 50.7e 03x (r2 =0.83);

torn fragments, y = i.5e 006x (r =0.74); uprooted

clumps, y = 2.7eO0.4x (r2=0.86).


-J

U 600-
I.-


2 00o


zi
0 400i

2 0
z


o



*o
400

C


^ 300.
c
.U
0
Lu
4
t 200-
4
C














SPECIES DAMAGE-WINTER
120 LJqwiqmgio repeni
Ziona aquatlca

100 ---- -- C mauoro
100 ----- Cicufa moculolda


0
*0
4 80



c 60
0
0
o
(9
<{ 40
5
<[


20



0


40 50 60 70 80 90

DIVERS (no./day)


0 10 20 30 40 50 60 70 80 90


DIVERS(no./aooy)


Figure 8. Damage by species, related zo number of
divers, Winter, 1977-73 (continued).


0 10 20 30


120



100 -



S80



60 -



40 -



20 -


Ceratophitlum demersum
- Nsturtium otficinoal
- - Myrirpayllum heterophyllum













-

"4".
.- \ -
,I \ v '









these species is considered collectively, however, it is

again evident that when the number of divers exceeds 60,

there is a marked increase in the amount of tearing and

uprooting of river plants.

Figure 9 shows, for each species, the percentage of

total damage and the percentage of total standing crop. It

is important to note that both damage and standing crop

values are estimates. The amount of plant drift netted is

undoubtedly less than the amount of plant material actually

torn or uprooted, and standing crop estimates are based on

a limited number of samples. The figure suggests that for

most species the amount of damage is proportional to

standing crop.

Chara appears to be an outstanding exception to this

assumption, in that the small amount netted is not propor-

tional to its large standing crop. This disproportion is

likely due to the difficulty of collecting this species.

Unlike other plants, Chara rolls on the bottom of the

channel, making it especially difficult to spot and retrieve

on busy days when the water turns nearly opaque with sus-

pended sediment.

Ludwigia and Myriophyllum also appear to be exceptions

to the assumption that damage is proportional to standing

crop. As both Ludwigia and Myriophyllum could be netted

fairly efficiently, it appears that they may be selectively

damaged. Ludwigia accounted for 15% of the total weight of








HEADSPRINGS REACH-WINTER


40-


30-



20-


0 o 1 1
Sagittaria


E] Percent of Standing Crop
E] Percent of Total Netted In Winter
1977-78


r-2


2fl


r-F


- I ...i .1 ~ ..& I I -~ I 4-4


Chra Cicuta ZzanMyriophyllumNsturtum
Chara Zinania Nasturtium


rj"~


Ludwigia
Ceratophyl lum


SPECIES


Figure 9.


Percent total damage and percent of total standing crop (total
weight of plants in the Headsprings Reach) of species netted in
Winter, 1977-78.








plant material netted during the winter damage survey.

However, the standing crop of Ludwigia comprises less than

1% of the total standing crop of the Headsprings Run and

Blue Hole area. Myriophyllum comprised 7% of the total

damage, but like Ludwigia, accounts for about 1% of the

total standing crop.

Although Sagittaria accounted for 40% of the total

damage, it also accounted for 35% of the total standing crop.


Summer Survey

Figure 10 shows the relationship of plant damage to the

amount of daily recreational use in the three reaches of the

Ichetucknee River. The largest amounts of drift were netted

from the Rice Marsh reach. Similar amounts of vegetation,

about 2000 dry grams, or 45 Ibs. fresh weight, were netted

on May 21 and June 14, when 1500 and 500 people, respectively,

were counted. On July 9 and August 5, when 2200 and 2700

users were counted, the amounts of damage more than doubled;

about 4500 dry grams, or 100 ibs. fresh weight, was collected

on each of these days.

The amount of drift netted from the Floodplain Reach

was much less than the amounts netted from the Rice Marsh.

On June 14, 810 users were counted and about 1000 grams

netted. On May 21 and July 9, at use levels of 2024 and

2056, 2744 and 2322 grams of plants were netted. The plant

drift collected on August 5, when over 3000 users were




















PLANT DAMAGE- SUMMER


A Heodsoringqs Reqch (---)
o Riice Marsh (---)
* Floodplain Reach (-)


0 t
j,


E


0 t
--"
t /


1000-


-4----


2000
USERS (no./doy)


Figure 10.


Amounts of daily plant damage and daily use in
three reaches, Summer, 1978. Relationship of
damage (y) to users (x) for each reach is de-
scribed by a linear equation: Headsprings

Reach, y = 307.5 + 0.53x (r = 0.57); Rice

Marsh, y = 1000.1 + 1.32x (r = 0.35); Floodplain

Reach, y = 1250.0 + 0.43x (r' = 0.55).


5000 -


0



Lo
S4000


S3000
C
a
0
LL I
o
^ 2000

I


1000


3000


4000


6000








counted in this reach, weighed 2637 grams, an amount similar

to that netted during the 2000-user days in May and July.

The amounts of vegetation netted from the Headsprings

Reach generally weighed less than the drift collected from

the other two reaches. Figure 10 shows that in the 500 to

1500 user range, plant damage consistently increased with

use. However, the amount of drift netted on the two 3000-

user survey days varied greatly. On Sunday, July 9, ,2851

users were counted, and about 2400 grams collected. On

Saturday,August 5, the amount of use (2864) was similar,

yet the amount of drift collected, 1083 grams, was less than

half the amount netted on July 9.

Figure 11 shows that, for all three reaches, the amount

of plant damage generally increased over increasing levels

of hourly recreational activity. However, the variability

of the results makes it difficult to predict the amount of

damage for a specified level of use. Despite this variabil-

ity, it is evident that over similar amounts of hourly use,

plant damage in the Rice Marsh was greater than the damage

in the Floodplain Reach or Headsprings Reach.

Figure 12 is similar to Figure 10, but describes

damage in each reach as a fraction of the total standing

crop of that reach. This figure clearly shows that recre-

ational use generally removes a much larger fraction of the

standing crop of the Headsprings Reach than it does in the

middle and lower reaches. One notable exception occurred
























PLANT DAMAGE- SUMMER


2000 r


* Headsprinqs Reach
O Floodplain Reach
0 Rice Marsh Reach












0
0 0
o

0 3 0

0 0

.00


o 0


500 750 1000 125


USERS (no./hr.)


Figure 11.


Amounts of hourly plant damage and use in
three reaches, Summer, 1978.


1500




3 1200

C
>8

0
0
u 800
<
0


400




0





























* Heodsprinnqs Reach
0 Rice Marsh
A Floodplain Reach


0 0


1000


2000

USERS (no./doy)


Figure 12.


Number of users and fractional loss of
standing crop, for three reaches, Summer,
1978.

Fractional loss =


total damage/day (oven dry wt., grams)
standing crop (oven dry st., grams)

The letter "a" indicates data points for
June 14 which is mentioned in the text.


2.0-



in
10
- 1.5-
4





VI
-

0
. 0.5-
u
4


30o00


4000








on June 14, the only weekday sampled, when the damage was

low, and about the same, for all three reaches.


Species damage. Figure 13 shows the percentage damage

and percentage standing crop of each of the major species

in the three reaches of the Ichetucknee River.

In the Headsprings Reach, the amount of damage to a

species was generally proportional to the size of its,

standing crop (see Sagittaria, Zizania, Myriophyllum,

Ludwigia, and Nasturtium). A few species, however, sus-

tained disproportionate amounts of damage. The percent

Cicuta damage (22%) was twice as large as its percent

standing crop (11%). In contrast, the percent Chara damage

(8.1%) was less than half its percent standing crop (25%).

As previously stated, the data for Chara reflect the diffi-

culty of netting this species.

For most Rice Marsh species, the amounts netted were

generally proportional to their standing crops. Chara was,

again, an exception (1% damage, 20% standing crop).

Vallisneria was another, but the amount netted (25% total

damage) was disproportionately large relative to its

standing crop (5% standing crop).

In the Floodplain Reach, percent total damage was

similar to percent total standing crop for most species

except Myriophyllum and Sagittaria. Whereas Mlyriophyllum

appears ro be selectively damaged (37% damage, 16% standing

crop), Sagittaria appears to sustain relatively little

impact in this reach (16% damage, 30% standing crop).


I








HEADSPRINGS REACH


RICE MARSH


E7z Percent of standing crop
D7 Percent of total netted in
summer, 1978


L__i;7nq41_____


FLOODPLAIN REACH


Sagittaria Myriophyllum Valisnerio Nasturtium Ceratophyllum
Zizania Chara Ludwigia Cicuta


SPECIES


Percent total damage and percent of zotal standing
crop (total weight of plants in each reach) for
plant species in three reaches, Summer, 1978.


I--
z
w 30-
0 i/

W 20 /
10-
A..
I0 //


70

60-

50-

40-

30-


Figure 13.







Plant Resistance

Figure 14 shows the average amount of spring force

required to tear or uproot the stems of several aquatic

species common to the Ichetucknee River. The large species,

Zizania and Sagittaria, offered considerable resistance: 1C

and 6 pounds(4.5 and 2.7 kg) of pull, respectively, were

required to dislodge these plants. In contrast, the stems

of Chara, Ludwigia, and Nasturtium tore under a light pull

equivalent to about 0.3 pounds (0.1 kg) of spring force.

Myriophyllum stems were moderately resistant, tearing at

0.5 pound (0.2 kg) of pull.

Figure 14 also shows a large variability among the in-

dividual plants tested for each species. Resistance measure-

ments on several different-sized plants showed that smaller

and/or shallow-rooted Zizania and Sagittaria plants pulled

free from the substrate much more readily than plants which

were buried under a layer of sediment. In fact, stems

buried at depths greater than 10 centimeters could not be

dislodged. Under increased pull the leaf clusters of deeply

buried plans tore free at the soil surface, leaving the

perennial stems intact below.


Changes in Plant Cover

Figure 15 shows the changes in plant cover in three

sections of the Headsprings Run over two successive seasons

(.winter and summer) of recreational use. It is evident that

a substantial amount of vegetative regrowth occurred between

NIovember-December, 1977, and April, 1978, and that over the










Zlzanla aquatlca (5)


SagIttarla kurzlania (6)


Myriophyllum
heterophyllum (3)

Ludwigla repens


Chara sp.


Nasturtium officinale


II


ZZ~i


iJ-~


0 2 4 6 8 10 12 14 16 I
0 2 4 6 8 I0 12 14 16 18


RESISTANCE


Figure 14.


(spring force, Ibs.)


Resistance to tearing and uprooting. The resistance of
several species was measured as the amount of spring stretch
required to tear, or uproot a plant. Bars show mean response
and lines ( ---| ) show standard deviations for species
subjected to several trials, the number of which are shown
in parentheses. A pound of resistance is equal to 0.45 kilo-
grams of spring force.




MAP J--7T: H
11-18-77


4-4-78


9-21-78


Ceratophyllum

E Nasturtium
SHvdrococvl
/ Shr-jbs
SLobelia


Figure 15.


g Myriophy
U4a
[:j*j Ludwigia

E[ Chara
e Zizania
E Open are


'l!um


,as


Seasonal changes in plant cover in three
sections of the Headsprings Run. Section
H, 5 meters in length, is located itnedi-
ately downstream of the First Dock.
Sections Q and R, each 10 meers in length,
are ccntiguous and are located opposite
and just below the Third DoCx.








MAP SECTION Q

12-12-77


9-21-78


Figure 15. Continued.






MAP SECTION R
12-2-77


9-21-78


Figure 15. Continued.









following summer these same sections sustained a heavy loss

of plant cover.

Map sections Q and R show the winter recovery and

summer loss of Chara and Zizania cover in the Third Dock area.

Planimetric measurements showed that Chara cover in section

R increased about 12 m2 over the winter, but decreased about

Sm over the following summer. Zizania cover, almost non-

existent in section Q in December, 1977, increased greatly

in this area over the winter. However, this new growth was

trampled back during summer 1978 ro about the same level as

was originally mapped the previous November.

Hydrocotyle and Ceratophyllum, two minor species com-

ponents of the Headsprings Run, showed a large amount of

growth in section H between November, 1977, and April, 1978.

The increased coverage of these two species, as well as that

of Zizania, resulted in a narrowing of the open channel

floor from about 4 meters in November to about 2 meters in

April. Nearly all of the Ceratophyllum winter growth, as
well as a considerable amount of Zizania, was trampled out

the following summer, resulting in an enlargement of a

channel width to about 3 meters by September, 1978.


Experimental Plots


Sagitaria

Two trends are apparent in Table 3 and Figures l-l,

which show the results of the Sagittaria growth experiment







Table 3. Regrowth of aquatic plants following cutting or uprooting. In cut plots, all stem
and leaf material was clipped back to substrate level. In uprooted plots, all rooted
plants were pulled from the substrate. The biomass values represent the mean sample
weight (g/m2) and standard deviation of: 1. the above ground material that was
recovered by vegetative regrowth in cut plots; 2. both the above and below ground
(rhizomes, roots) material that was recovered by colonization in uprooted plots.
Both harvest and indirect methods (Appendix A) of biomass measurement were used to
determine these values. The growth rate (g/m-/day) was determined by dividing
biomass change between successive sampling dates by the length (days) of the
sampling interval.


Biomass Growth Rate
Number (Oven Dry Wt.) (Oven Dry Wt.)
Species of Plots Treatment Time g/m1 g/m2/Day

Sagittaria kurziana 3 Uprooted 2-20-78 0.0
3-21-78 10.8 + 0.5 0.03
4-30-78 16.9 + 9.] 0.40
6-31-68 193.7 7 72.8 4.02

3 Uprooted 6-18-78 0.0
7-28-78 34.0 + 8.9 0.85
8-28-78 154.5 T 29.4 3.88

3 Cut 2-20-78 0.0
3-22-78 13.9 + 5.8 0.46
4-30-78 50.9 T 6.9 1.24
6-13-78 278.9 + 34.5 3.52

3 Cut 6-18-78 0.0
7-28-78 119.2 + 14.8 2.98

3 Cut 7-28-78 0.0
8-28-78 99.2 + 11.3 3.20
~-3







Table 3. Continued.


Treatment


Time g/m g/m2/ Day


Biomass
(Oven Dr Wt.)
g/m3


Growth Rate
(Oven Dry Wt.)
g/m2/Day


Myriophyllum hertophyll um











Chara sp.


Cut


Cut


Cut


Cuta


Cut


Cut


Cut


Cut


Uprooted


Vallisneria americana


2-22-78
3-23-78

3-30-78
5- 6-78

5- 6-78
7- 7-78

6-12-78
4-25-78

2-25-78
3-25-78

3-25-78
5- 6-78

5- 6-78
7- 7-78

8-10-78
9- 6-78

8-15--78
9-26-78

8--15-78
9-26-78


0.0
98.4 +

0.0
183.2 +


0.0
200.8

0.0
222.4

0.0
371.2

0.0
519.2


3.7


39.3


+ 49.8


+ 116.5


0.0
480.0 + 208.2

0.0
124.8 + 83.7


27.2


50.0 + 36.8


Species


Number
of Plots


3.39


4.95


3.23


5.05


13.25


12.36


7.74


4.6


0.65


1.19


Time










Table 3. Continued.


Treatment


Time


Biomass
(Oven Dry Wt.)
g/mn


Growth Rate
(Oven Dry Wt.)
g/m2/Day


Zizania aquatica


Cut


6-12-78
7-25-78


24.6


aCut from a bed in the Headsprings Exclosure.
bA second uprooted plot, which failed to produce any new plants, is omitted from this table.


Species


Numbn er
of Plots


0.61











EXPERIMENTAL PLOTS
Soaqittaria kurziono


800


JE
-S
600
3



-2400

W
o
U
W
W 200
4-
L.J
..


0 Leaf toMding crop
* Cut plots
V Time of cutting


MONTH


Figure 16. Standing crop and recovery of Sagittaria leaves
following cutting. Bars show standard deviations
of means based on three replicate plozs (0.125 m2).


EXPERIMENTAL PLOTS
Sogitfaria kurziona


F


....1________


March I April I


8 i2
8(-^
4

January o Feor



V rime of uprooting


February March I April


May I June I July August


ruary i
I

7
V


May i June I


Figure 17. Standing crop and seasonal recovery of Sagittaria
clumns following uprooting. Bars (-- show
standard deviations of means based on three
replicate plots (0Q.25 m2).


Z 1000
U E
z"-
CD -
Z
500

a.J
0 0
F
300



200
0-
U -
W3

^:100
Z o
_j


ebruary I
r


F


r% -


A


MONTH


July August


i II II

























0 Starnding crop
* Uorooted ploit


so
40
4AP4 FES


';' Boo-
E

00


z
1-
Z
<[
a.

S400
4
I-

00
200



0 ----
February






Figure 13.


MONTH


Number of Sagittaria clumps counTced in
quadrats following uprooting, and
standing crop (no. of clumps) in
undisturbed quadrats sampled in February
and June, 1978.









conducted at the Devil's Eye Exclosure: 1. The rate of

regrowth following disturbance is much greater in summer

than winter. 2. Plots in which only above-ground parts

(leaf blades) were cut regrew more rapidly than plots in

which all plant material (leaves, stems, and roots) was

removed from the substrate.


Winter growth. Inspection of Table 3 shows the

differences in winter growth rates between cut plots and

uprooted plots. On March 21, about one month after the

initial disturbance (Feb. 20), the uprooted plots contained,
O
on the average, about 1 gram of biomass/m'. Over the same

period, the cut plots had produced about 13 grams of new

leaves. On June 13, nearly four months after the plots were

first disturbed, leaf material harvested from cut plots
0
weighed about 300 grams/m', while whole clumps, harvested
2
from uprooted plots, weighed about 200 grams/m2.

These results indicate that, following an initial lag

period (Feb.-March), clump production proceeded relatively

rapidly, reducing the magnitude of biomass differences

between the uprooted and cut plots.


Summer growth. The growth of Sagittaria clumps in

uprooted plots is much more rapid in summer than winter.

On July 28, 40 days after three sample plots were initially

uprooted (June 13), the mean weight of the new growth was

about 35 grams/m- (_ig. I7). In contrast, plots uprooted









in February had produced less than half this amount after

70 days of regrowth. Again, as in winter, there was a more

rapid accumulation of biomass in cut plots than uprooted

plots. Over the 40-day period mentioned above (June 13 -

July 28), the cut plots (Fig. 16) produced about 110 grams/
2
m of new leaf biomass, about three times the amount cf
2
clump biomass (35 grams/m ) produced in the uprooted plots

(Fig. 17) during the same period.


Standing crop. Results from sampling in undisturbed

plots show that the standing crop of Sagittaria is signifi-

cantly greater in summer than winter. The oven dry weight

of plants (including leaves, stems, and roots) sampled on

February 20 was 563.8 grams/m2. Plants sampled on June 18

weighed 1000.6 grams, nearly a 100% increase over the winter

weight (Fig. 17). The biomass of summer leaf blade samDles

was also significantly greater than the biomass of winter

leaf blade samples (Fig. 16). The mean weight of leaf

22
blades sampled on February 20 was 439 grams/m ; the summer

biomass was 692 grams/m2.

Interestingly, the number of clumps in sample plots

did not change seasonally (Fig. 18). On February 20,
2
sampling showed an average of 101 clumps/m On June 18

the mean number of clumps was 106/m 2, a nonsignificant

increase.









Myriophyllum, Chara, Zizania

The pattern of Myriophyllum recovery was markedly

different from that of Sagittaria. Myriophyllum plots cut

in February regrew at about the same rate as plots cut in

June (Fig. 19). Also, the relative recovery of Myriophyllum,

expressed as the ratio of biomass recovered to standing

crop, was greater than that of Sagittaria. Over a period

extending from February 22 to March 23, Myriophyllum plots

(0.125 m 2) in which all the above-ground material was

clipped to the substrate level, recovered about 98 grams/m2

of stem and leaf material, almost 60% of the original amount

cut (about 170 grams/m ). In contrast, Sagittaria plots,

clipped back to substrate level on February 20, had recovered
2
only 13 grams/mn or 3% of their original biomass (about 440
2
grams/m2 ) at the time of harvest on March 21.

Chara, like Myriophyllum, recovered relatively rapidly

following cutting (Table 3). Between February 20 and March

25, Chara plots in the Floodplain Reach produced, on the

average, 371 dry grams/m of new growth, almost 40% of the

original amount cut (961 dry grams/m ). Plots cut from a

bed in the Headsprings Reach in summer did not exhibit as

rapid a recovery as did the February plots at a downstream

site. After a 27-day period (the recovery period for the

February plots was 29 days), the Headsprings Reach plots

contained, on the average, about 125 dry grams, which was

only 20% of their original biomass (641 grams/m ).





















EXPERIMENTAL PLOTS
Myriophyium heterophyllum


Floodplain Reach
0 Standing crop
Cut plot
Headspring Reach
o Standing crap
Cut plot


Figure 19.


Standing crops and regrowth of Myriophyllum
following cutting. On February 22, March
30, and May 5, two plots (0.125 m2) were
clipped from a bed in the Floodplain Reach
and harvested after a 4-6 week recovery
period. One plot (0.125 m2) was cut on
June 12 from a bed in the Headsprings Run
and harvested on July 25. Bars show
standard deviations of sample means.


S
S300
3C
L5
C
S200

IJ~
W

J 100




0


/
/



February March
February $ March


MONTH


August









Table 3 shows the recovery of several other species

following cutting. The pattern of recovery of Zizania

aquatica exemplified the ambiguity of results obtained from

some of the test plots. In June, several Zizania plants in

a quadrat in the Headsprings Exclosure were cut back to

substrate level. A month later, none of the plants origi-

nally cut could be found, and a thick felt-like layer of

algae covered the sample area. The only macrophyte observed

in the quadrat was one Zizania clump, not one of those origi-

nally cut, which appeared to have emerged from the substrate

during the recovery period. In contrast, several Zizania

plants, cut back in the channel of the Floodplain Reach,

recovered about 16 centimeters of leaf growth over a 5-day

period in February.

Results from Vallisneria plots indicate that the

recovery of this species may be dependent on the initial

vigor of the bed. Plots which showed a relatively large

standing crop prior to disturbance (cutting or uprooting),

exhibited much more regrowth (Table 3) than did pocts having

a low standing crop.


Exclosures


Headsprings Exclosure

Figure 20 shows the change in channel profile and

shifts in the positions of the dominant plant beds in a

section (Site A) of the Headsprings Exclosure monitored over











HEADSPRINGS EXCLOSURE
JUNE 12,1978


AUGUST 24,1978


t Myriophylum
] Ludwigia
j Chara


|< Zizanio-submerged
[o- Zizania- emergent
I Shrubs


METERS
I 0
0 1 2


SBI. Gn. Algae

Figure 2C. Change in plant cover, Site A, Headsprings
Exclosure, 6-12-78 to 8-24-78.








the summer of 1978. Between June 12 and August 24, 1978,

channel closure averaged about 70 centimeters over the

length of this 5-meter section. As the figure and time-

series photographs show (Plate 1), the vegetative expansion

of several species, including Chara, Myriophyllum, Ludwigia,

and Zizania, resulted in a narrowing of the channel.

Figure 21 shows the change in channel profile of a

second exclosure section (Site B), located just upstream of

the 5-meter map section. The average amount of closure,

measured at one-meter intervals over this 10-meter section,

was about 40 centimeters over a two-month period in summer.

A notable feature, evident in both the IC and 5 meter sec-

tions, is an increase in profile irregularity as natural

forces become more important than human disturbance in

shaping the growth patterns of submerged plant beds.


Second Dock Exclosure

The change in plant cover in eight 1 m. quadrazs,

protected from recreational disturbance by the fenced exclo-

sure opposite the Second Dock, is shown in Figure 22.

Between July 24 and October 26, plant cover increased in

four of the quadrats, but showed little change in the others.

Quadrats 1, 3, and 6, which contained largely bare sand

prior to exclosure, remained in essentially the same condi-

tion over the measurement period. Small patches of blue-

green algae shifted in position, but did not increase the

olant cover in quadrats 1, 2, and 3. In fact, the only































Plate 1.


Headsprings Exclosure, July and November, 1978.
This section of the channel, lying immediately
above the downstream fence was photographed from
approximately the same position one month after
the exclosure was erected (A) and four months later
in November (B). Several changes are apparent:
the growth of individual plant patches, the closing
of the open channel, and the diversity and beauty
of a protected reach.






70



A



























B
~ % ~ t tI~k













HEADSPRINGS EXCLOSURE
Channel Profile


- 8- 3-78
--- 10-12-78


CN-


0.1


Centimeters
I . |
0 50

Figure 21. Change in channel profile, Site B,
Headsprings Exclosure, 8-3-73 to 10-12-78.




SECOND DOCK [XCLUSURE


M Myriophyllum
L J heterophyllum 6 17 is
SAlgae (blue- IMETER
green color)
1 Algae (brown color)

Z_ Chara and algae
Zizania aquatica

Figure 22. Change in plant cover, Second Dock
Exclosure, 7-25-78 to 10-26-78.









evidence of new plant growth in 1, 3, and 6, was a Zizania

seedling, which appeared in quadrat 1 at the time of the

third mapping on October 26. Quadrat 2, tucked in a quiet

shallow, appeared to be dominated by algal growth which

showed a slight decrease in coverage during the study.

The vegetative cover in quadrats 4, 5, 7, and 8 in-

creased considerably between July and October. On June 25,
2
the date of the first mapping, Chara covered about 1.1 m of

the bottom in this four-quadrat section; 43 days later, on
2
September 6, Chara cover measured 1.6 m representing an

average rate of increase of 115 cm2/day.

On October 26, Chara beds covered 2.0 m of the 4.0 m'
2
section, having grown at an average rate of 80 cm /day

since September 6.

Myriophyllum cover did not change much over a three-

month period. On July 25, Myriophyllum cover in quadrats

4, 5, 7, and 8 was 0.25 m ; on October 26, this species

covered 0.26 nm a negligible increase.

Figure 23 shows that the number of Zizania plants in a

fixed quadrat did not change between August 3 and September

26, 1978. However, the size of the individual plants did

increase. On August 3, the mean length of Zizania plants

was 66 centimeters. On September 25, mean plant length was

77 centimeters.
2
The change in plant cover observed in this 1 m quadrat

was almost entirely due to the vegetative expansion of Chara.











2nd DOCK EXCLOSURE
Zizania quadrant


8-3-78


* Zizania clumps

[] Chara
Centimeters


Figure 23. Growth of Zizania and Chara, Second Dock
Exclosure.


9-26-78








Blue Hole Cages


Jug Cage

Results from the Jug Cage in Blue Hole are summarized

in Figure 24. On June 6, shortly after the Jug Cage was

installed, the amount of Sagittaria leaf biomass in a sample

taken inside the cage (240 grams/m2) was about the same as

the amount of leaf biomass in a sample taken from the
2
Sagittaria bed surrounding the cage (220 grams/m ). On

September 11, after two months of protection, a sample of

leaf blades clipped from within the cage weighed over 300
2
grams/m whereas the biomass of a sample taken from the un-
2
protected area outside the cage was less than 200 grams/inm .

The biomass differences of the inside-outside cage

samples can be attributed to differences in the size of

individual leaves, not in the number of leaves. As Figure

24 shows, the number of leaf blades in the sample clipped

from the floor of the cage on September 11 was actually less

than the number of leaves in the sample taken from outside

the cage. The length of leaves inside the cage, however,

was much greater than leaf lengths in the surrounding bed.

Figure 24A, describing the frequency distribution of

leaf lengths, shows that the lengths of cage leaves were dis-

tributed relatively evenly over size classes ranging from

0-9 to 80-89 centimeters. In contrast, the leaf lengths of

the outside sample showed a skewed distribution with a modal

size class of 10-19 centimeters and class range of 0-9 to

50-59 centimeters.

















JUG CAGE
Sagifttoria kurziana


A 9-11-78


o Inside cage
SOutside coge


40-49 50-59 60-69 70-79 80-89 90-99 '100-109


LENGTH CLASS (cm)
400-

S300
200-

4 c100-
we
_j
0


1 1
C
0 ~


C

7"-78





.s .
ID
0


9-11-78




|R


Figure 24.


Characteristics of Sagittaria leaves sampled
both inside and outside of Jug Cage. A. Size
distribution of inside-outside leaf samples.
B. Numbers of leaves of inside-outside
samples. C. Weight of leaves of inside-
outside samples.


S1280
E
S960
S640

- 320
.-J








Run Cage

The biomass, number, and size of Sagittaria leaves

cut inside and outside the Run Cage are shown in Figure 25.

The number of leaves in the two samples were about equal,

but they differed greatly in size and biomass. After three

months of protection, cage leaves weighed about 450 grams/m ,

and were distributed over a wide range of length classes

with maximum lengths between 100 and 109 centimeters. The

Sagittaria leaves in the surrounding bed appeared to be

stunted. They averaged about 25 centimeters in length, and

measured only 60 centimeters at the maximum. The biomass
2
of the outside sample was about 300 grams/m considerably

less than the inside sample.

Over the summer (May 29 to September 12), Sagittaria

plants colonized 0.55 m2 of the open sand area in the Run

Cage (Fig. 25). The 347 new clumps produced during this

period accounted for a net biomass accumulation of 202.7

grams. As is evident in the figure, the increase in

Sagittaria cover was greater on the downstream side of the

cage than on the side facing the flow.

Another feature which distinguished the inside cage

sample from the outside sample was the color and texture of

leaf blades. Leaves cut from the cage were bright green

and smooth. Leaves from the surrounding bed were brownish

and gritty. Results from ashing showed that the organic

weight of cage leaves was about 83% of their dry weight;

















* Inside coge
S Outside cage


RUN CAGE
Sogittario kurziona

9-11-78


I 80-89 I 90-99 I 100-109


0-9 I 10-19 1 20-29 30-39 1 40-49 I 5-9 6-69 I 70-79

LENGTH CLASS (cm)


o Ash weigtil



- c





-w
0
e


1:::


Figure 25.


B 4"


E





0
zs




o


=
0


D Sagittaria Colonization




7,
....... -$. ,.

... -.-.....


GROWTH
EDGE OF BED
*-0 5-29-78
-- 7-6-78
0--0 9-12-78


cm
0 20


Sagittaria colonization and characteristics of leaves
sampled both inside and outside of the Run Cage.
A. Distribution of leaf lengths of inside-outside
samples. B. Weight of leaves of inside-outside
samples. C. Numbers of leaves of inside-outside
samples. D. Colonization of open cage bottom by
Sagittaria plants.


t 1600
E
s 1280

w 960
-J
LL~
0 640
tU
a 320
z n


m. 1IthrhrIiri n] H 0n1


I


I I









the organic weight of leaves sampled outside the cage was

only about 63% of dry weight. Microscopic inspection of

the residue remaining after ignition showed, for the cage

sample, a clean white ash. The residue from the outside

sample was grayish in appearance, and consisted of relatively

large sand grains in addition to ash and other mineral

matter.


Sediment Deposition

There was a considerable buildup of sediment in both

cages following installation. In the Jug Cage, sediment

depth increased 5.8 centimeters between May 29 and July 6,

1978. In the Run Cage, sediment depth increased 1.4 centi-

meters between May 29 and June 30.


Response to Repeated Cutting

Figure 26 shows the regrowth patterns of Sagittaria

plots subjected to varying intensities of cutting over a

four-month period extending from February 20 to June 13,

1978. Plots that were cut six times previous to the test

recovery period (June 13 to July 21) regrew just as

rapidly as plots that were cut three times or only once.

The figure also shows that the average growth rate (slope)

of plants cut every two to three weeks increased after each

successive cutting.

Following the first cut on February 20, Sagittaria leaf
blades grew back at an average rate of 0.48 grams/m/day
blades grew back at an average rate of 0.48 grams/m /day























400



300
3
"D
0

*o
Ic I0
S200
Cr
W
0
U
C 100
u.
W
tJ0

0


REPEATED CUTTING
Soqittaria kurzioana
A*.-- Cut ofat 4 months
0- - Cut every 4-6 weeks
*- Cut every 2-3 weeks




J.
7,
7 '


.7

S/ /\t
7"7
/-/ / "*/7


February


MONTH


Figure 26. gittaria leaf recovery in plots subjected to
reheated cutting. Three plots (0.125 m2) were
used for each of three treatments: 1. plots
cu, every 2-3 weeks, 2. plots cut every 4-5
weeks, and 3. plots cut after four months.









over the ensuing 15-day period. The same plots recovered
2
at an average rate of 3.7 grams/m /day after the last cutting

on June 13. This rate is comparable (no significant differ-
2
ence) to the rates of 3.6 and 3.8 grams/m /day measured for

plots cut three times and only once, respectively, prior to

the test recovery period. The growth rate of three new

plots, cut on June 18 and harvested July 28, was 3.0 grams/

m2/day.


Fauna Survey


Invertebrates

Mollusks. Table 4 summarizes the results of the inver-

tebrate sampling in areas subject to varying degrees of

disturbance. The table shows that one of the samples from

the Headsprings Exclosure (No. 1), which at the time of the

survey had been undisturbed for over two months, contained

more species (4) and greater numbers (about 17,000/m2) and
2
biomass (about 720 grams/m including shell weight) of

mollusks than any other sample. Each of the other five sam-

ples contained fewer species, and less than half this number

or biomass. Of these, the sample taken from the moderately

disturbed Chara bed below the Third Dock (No. 5) contained

the greatest snail biomass. The number of snails in the

other Third Dock sample site (No. 6), a badly torn Chara

bed, was similar to the number found in a sample (No. 4)

taken from a less disturbed bed in the Second Dock Exclosure.








Table 4. Plant biomass and number and weight of mollusks and arthropods sampled in three areas
subject to varying degrees of recreational disturbance. Two samples were taken from
Ohara beds at each site in August 1978. The Headsprings Exclosure had been fenced two
months, and Second Dock Exclosure about three weeks prior to sampling. The Third Dock
area was unprotected and subject to trampling prior to the sampling day. The diameter
of the pipe was 1.5 em; the area sampled was 0.0177 in2.


MOLLUSKS


Chara
Sample (Oven Dry
No. Wt., gais)


Goniobasis
Weight
No. (g)


Campeloma
We i ght
No. (g)


Physa
Weight
No. (g)


Helisoma
Weight
No. (g)


Total Mollusks
Weight
No. (g)


Headsprings
Exclosure


Second Dock
Exc] osure


Third Dock
Exclosure


9.3
18.3


10.5
8.3


10.6
1.6


214 10.26 2
86 4.57 0


48 2.45 0
97 5.00 0


0.57


7.52
3.64


1.89 1
0


0.19 0
0.02 0


0
0.11 0


.02


304 12.74
86 4.57


2.64
5.02


7.52
3.75


Palaemonetes
Weight
No. (g)


Cambarus
Weight
No. (g)


ARTHROPODS

Other
Crustaceans
Weight
No. (g)


Insect Larvae
Weight
No. (g)


Total
Arthropods
Weight
No. (g)


Headsprings
Exclosure


9.3
18.3


0.48 1
0.16 1


0.02 0
2d


0.37
0.39


Location


0.87
0.69


0.14







Table 4. Continued.


Other Total
Chara Palaemonetes Cambarus Crustaceans Insect Larvae Arthropods
Sample (Oven Dry Weight Weight Weight Weight Weight
Location No. Wt., gins) No. (g) No. (g) No. (g) No. (g) No. (g)

Second Dock
Exclosure 3 10.5 14 0.67 1 0.01 0 1e 0.36 16 1.04
4 8.3 14 0.70 0 0 1f 0.02 15 0.72

Third Dock
Area 5 10.6 7 0.29 5 0.47 0 1i 13 0.76
6 1.6 2 0.01 0 0 2 0.07 4 0.08

aFresh weight after draining preserved snails (10% Formaldehyde) for one-half hour.
bsample ; was taken from a moderately disturbed bed near the riverbank.
c
Sample 6 was taken from a badly torn bed at the edge of the main channel.
dOne was an Odonate, the other Rhagovelia sp.
eAn Odonate.
fAn Odonate.

gA Trichopteran, which was not removed from its larval case or weighed.
hBoth Odonates.








The weight and numbers of mollusks does not appear to
be related to the amount of vegetation at a site. Maximum

numbers and weight were found in a sample (Headsprings

Exclosure, No. 1) which ranked fourth in weight of plant

material. In contrast, the second sample in the Headsprings

Exclosure (No. 2) contained the most plant material, but

ranked fourth in both number and biomass of mollusks.


Arthropods. Table 4 shows that both the number and

biomass of arthropods in the sample taken from the heavily

disturbed Chara bed (Third Dock, No. 6) were considerably

lower than the number and biomass of samples taken in other

areas. This sample contained two insect larvae and two

small shrimp, which collectively weighed 0.08 grams (sampling
2 2
area 0.0177 m ) or 4.5 grams freshweight/m A second sample

taken from a less trampled portion of the same bed (Third

Dock, No. 5), contained a Trichopteran (Caddis fly) larvae.

5 small crayfish, and 7 shrimp, which collectively weighed
2
0.76 grams, or 43 grams freshweight/m The biomass of

arthropods sampled in the two fenced areas, the Headsprings

Exclosure and Second Dock Exclosure, was about the same as

that found in Third Dock, No. 5, with the exception of sam-

ple No. 3, Second Dock Exclosure, which weighed 1.04 grams.


Fish

Results of the fish survey are summarized in Table 5.

which shows the types and numbers of fish and other aquatic







Table 5. Types and numbers of fish in disturbed (First
Exclosure) sections of the Headsprings Reach.
an imunderwater observer recorded all fish seen
swim along a submerged rope)I each area.


Dock area) and undisturbed (Headsprings
On each survey day (8-10-78 and 10-13-78),
on two alternate runs (a slow upstream


HEADSPRINGS EXCLOSURE
Number of Fish
8-10-78 10-13-78

Run 1 Rim 2 Run 1 Run 2


FIRST DOCK
Number of Fish
8-10-78 10-13-78


Run 1 Run 2


Run 1 Run 2


FISH
Centrarchi dae
Stumpknocker Lepomis punctatus
Redbreast Lepomis auritus
Other Sunfish Lepomids spp.
Total Sunfish Lepomis spp.
Bass Micropterus spp.

Esocidae
Redfin Pickerel Esox americanus


Percidae
Darter Percina sp.


Poecilli dae
Mosquitofish Gambusia affinis

Cyprinidae
Chub Hybopsis harper
Sucker Moxostoma sp.
Chubsucker Erimyzon sucetta
Golden Shiner Notemigonus crysoleucas


6 2
3


0 0


0 0


9 6


1 1


2 0


+ +


6 4


0 1


0 0


5 10


1 1


]. 0








Table 5. Continued.


HEADSPRINGS EXCLOSURE FIRST DOCK
Number of Fish Number of Fish
8-10-78 10-13-78 8-10-78 10-13-78

Run 1 Run 2 Run 1 Run 2 Run 1 Run 2 Run 1 Run 2

TURTLES
Loggerhead Musk Sternothaerus minor 0 2 1 1 0 0 0 0
Yellow-bellied-- Pseudemys script 0 0 0 1 0 0 0 0
Other Pseudemys sp. 0 1 0 0 0 0 0 0

CRUSTACEANS
Crayfish Cambarus sp. 0 0 0 0 0 1 1 0

+ indicates that a species was seen, but the numbers of fish not recorded.









organisms in protected and unprotected areas of the Head-

springs Run. The majority of fish observed were represented

by two families, the sunfish family, the Centrachidae, and

the minnow family, the Cyprinidae. The table shows that

whereas only one Cyprinid species, the common chub, Hybopsis

harper, was seen in the disturbed area below the First Dock,

several members of this family, including chubs; chubsuckers,

Erimyson sucetta; suckers, "oxostoma sp.; and golden

shiner, Notemigonus crysoleucas were seen inside the fenced

exclosure. The figure also shows that two species of turtle,

the loggerhead musk, Sternothaerus minor, and yellow-bellied,

Pseudemys scripta, were observed in the exclosure. No

turtles were seen on four 20-meter runs in the area below

First Dock.

The numbers of Centrachids also differed greatly in the

two study areas. Large congregations of bass (Micropterus

spp.lj and bream (Lepomis spp.) were commonly observed in the

Headsprings Exclosure under the shelter of aquatic Dlants or

overhanging shrubbery. in the First Dock area, where much

of the vegetation had been trampled out, the few bass and

bream counted were generally observed feeding or resting

alone or in pairs. Despite heavy disturbance, crayfish were

seen near the First Dock during the survey. Although no

crayfish were seen in the exclosure during the four survey

runs, they were frequently observed in this area during work

on other aspects of the study.














DISCUSSION


In the Headsprings Reach, the loss of plant cover

resulting from recreational use is more visibly apparent

than is the loss of cover in either the Rice Marsh or Flood-

plain Reach. The data show, in fact, that the percentage

loss of standing crop in the Headsprings Reach is much

greater than the percentage loss in the middle and lower

reaches. For this reason, details of the impact of recre-

ation on the plant communities of the Headsprings Reach are

discussed first, followed by the impact of recreation on

the plant communities of the Rice Marsh and Floodplain

Reach; the impact of recreation on the animals of the river;

and the carrying capacity for recreational use.


Impact of Recreation on
the Plant Communities of the Headsprings Reach


Tuber Impact

The three sections of the Headsprings Run which were

mapped in April, 1978, and remapped in September, 1978, show

that there is a large loss of plant cover in this reach in

summer. A more detailed analysis of the data from the Dlant

damage survey reveals aspects of tuber impact which were not

shown in the figures included in the Results section.

Figures 10 and 11 in the Results section suggest that tuber




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