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- DIEL PARTIONING OF THE EFFECTS OF VERMETID GASTROPODS ON CORAL GROWTH
- Series Title:
- Annual UF Undergraduate Research Symposium
- Farrell, Morgan
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- Conference Abstract
- Subjects / Keywords:
- Coral reef ecology
- Coral reefs are vital ecosystems that provide ecological and economic benefits, but are threatened by a variety of natural and anthropogenic factors. For example, coral growth, survival, and production of new polyps are negatively affected by vermetid gastropods; however the mechanism is unknown. It may be possible to gain insights about the mechanism by determining if effects of vermetids arise during the night, when corals are feeding (by competition for food) or during the day, inhibition of photosynthesis (by reducing light availability). To determine if the coral response to vermetids depends on the time of exposure, we conducted a field experiment by manipulating the time of exposure and vermetid densities. We placed coral fragments on coral bommies, where all bommies were paired: one with ambient densities of vermetids (V+) and one we removed all vermetids (V-). We then implemented four exposure treatments 1) always exposed to vermetids 2) never exposed to vermetids 3) exposed during day, and 4) exposed during the night. In this experiment, we did not observe the severe effects of vermetids on corals that were seen in past studies. There were no significant differences in any of the two-way ANOVAs, indicating limited effects of vermetids on corals. A secondary two-way ANOVA was conducted using coral life stage (juvenile vs. adult) crossed with three vermetid treatments: No exposure, Partial vermetid exposure (day only combined with night only), and Full exposure (both day and night). Tissue biomass was greater in V+ treatments, possibly due to polyps consuming nets. Marginal budding was slightly higher with no vermetid exposure, which is consistent with previous studies. Overall, juveniles budded less than adult corals, which could have been a consequence of morphology. Finally, the large disparity in effects of vermetids from this study versus past studies, and the importance of coral declines, suggest that further research is needed.
- Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Morgan Farrell.
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- General Note:
- Center for Undergraduate Research
- Poster presented at the 2015 UF Undergraduate Research Symposium
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- University of Florida Institutional Repository
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- University of Florida
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- Copyright Morgan Farrell, Lianne Jacobson, Elizabeth Hamman, Craig Osenberg. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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Surveys Surveys were conducted to determine when corals feed and when vermetids cast nets Hourly, we observed vermetids and corals in tanks for several days, and recorded: if coral polyps were extended (which indicates corals were feeding) the spatial coverage of vermetid nets Field Experiment We conducted a field experiment in Moorea, French Polynesia, to evaluate if the effect of vermetids on corals depended on the timing of exposure. Small j uvenile and adult corals (of the Massive Porites complex) were exposed to vermetids during the day ( blue ), during the night ( orange ), during both day and night ( red ), or not at at all ( green ). We quantified changes in: calcification, biomass, marginal budding, and interior budding. Data were analyzed using separate two way ANOVAs (+/ day exposure x +/ night exposure) with block as a random factor. Introduction Sessile vermetid gastropods reduce coral survival, skeletal growth and marginal tissue production (1) The mechanism behind this is not yet known (2) It may be possible to gain insight about this mechanism by determining if the effects of vermetids primarily: Arise during the day (when the coral symbiotic algae are, photosynthesizing), or Arise during (when the corals are feeding) (3,4) Results Surveys Tentacle extension was greater during the night, but net casting was relatively constant throughout Field Experiment There were no significant differences in any of the two way ANOVAs, indicating limited effects of vermetids on corals. A secondary two way ANOVA was conducted using coral life stage (juvenile vs. adult) crossed with three vermetid treatments: No exposure, Partial vermetid exposure (day only combined with night only), and Full exposure (both day and night)(Fig. shows means +/ confidence intervals) ; Tissue thickness increased with vermetid exposure (p=0.046 ); adults had thicker tissue than juveniles (>0.001) Calcification of was slightly higher in treatments lacking vermetids. Interior budding was greater in adults than in juveniles, with Partial slightly higher in juveniles (but there were no obvious patterns for adults). Marginal budding was greater in adults than juveniles, and the greatest budding observed in the No Exposure treatments (but there were no obvious patterns for juveniles). Diel Partitioning of the Effects of Vermetid Gastropods on Coral Growth Morgan Farrell 1 Lianne Jacobson 1 Elizabeth Hamman 1,2 Craig Osenberg 1,2 1 University of Florida, 2 University of Georgia Methods The severe effects of vermetids on corals that were documented in past studies were not found here. As a result the partitioning of effects into day time vs. night time effects was not possible. There were a few trends, however, which warrant further evaluation: Tissue biomass was greater in the +vermetid treatments. This result contrasts with past studies, but may have arisen if polyps consume nets (or the organisms trapped on the nets). Marginal budding was slightly higher in no vermetid exposure treatments, which is consistent with previous studies (1,2) Overall juveniles budded less than adult corals, which could have been a consequence of morphology. Finally the large disparity in effects of vermetids from this study vs. past studies, and the importance of coral declines, suggest that further research is needed that explores the environmental factors that may ameliorate or exacerbate the effects of vermetids on corals. Discussion References 1 Shima, J. S., C. W. Osenberg and A. C. Stier "The Vermetid Gastropod Dendropoma Maximum Reduces Coral Growth and Survival." Biology Letters 6.6 (2010): 815 18. 2 Shima Jeffrey S., Nicole E. Phillips, and Craig W. Osenberg "Consistent Deleterious Effects of Vermetid Gastropods on Coral Performance." Journal of Experimental Marine Biology and Ecology 439 (2013): 1 6. 3 Gagern, A., T. Schrg Nk Michiels G. Schulte, D. Sprenger and N. Anthes Behavioural Response to Interference Competition in a Sessile Suspension Feeder." Marine Ecology Progress Series 353 (2008): 131 35. 4 Kappner I., Sm Al Moghrabi and C. Richter. "Mucus net Feeding by the Vermetid Gastropod Dendropoma Maxima in Coral Reefs." Marine Ecology Progress Series 204 (2000): 309 13. Experimental Block (n=8) V+ V 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 Percent Net Cover Hours 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 Polyp Extension Day Night Y N