Nutrient enrichment, grazer identity, and their effects on epiphytic algal assemblages: field experiments in subtropical turtlegrass Thalassia testudinum meadows
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Material Information

Title:
Nutrient enrichment, grazer identity, and their effects on epiphytic algal assemblages: field experiments in subtropical turtlegrass Thalassia testudinum meadows
Series Title:
Marine Ecology Progress Series
Creator:
Baggett, Lesley P.
Heck Jr., Kenneth L.
Frankovich, Thomas A.
Armitage, A R.
Fourqurean, James W.
Publisher:
Inter-Research
Publication Date:
Language:
English

Notes

Abstract:
We tested the relative importance of top-down and bottom-up effects by experimentally evaluating the combined and separate effects of nutrient availability and grazer species composition on epiphyte communities and seagrass condition in Florida Bay. Although we succeeded in substantially enriching our experimental cylinders, as indicated by elevated nitrogen concentrations in epiphytes and seagrass leaves, we did not observe any major increases in epiphyte biomass or major loss of Thalassia testudinum by algal overgrowth. Additionally, we did not detect any strong grazer effects and found very few significant nutrient-grazer interactions. While this might suggest that there was no important differential response to nutrients by individual grazer species or by various combinations of grazers, our results were complicated by the lack of significant differences between control and grazer treatments, and as such, these results are best explained by the presence of unwanted amphipod grazers (mean = 471 ind. m–2) in the control cylinders. Our estimates of grazing rates and epiphyte productivities indicate that amphipods in the control cylinders could have lowered epiphyte biomass to the same level that the experimental grazers did, thus effectively transforming the control treatments into grazer treatments. If so, our experiments suggest that the effects of invertebrate grazing (and those of amphipods alone) were stronger than the effects of nutrient enrichment on epiphytic algae, and that it does not require a large density.
General Note:
Marine Ecology Progress Series Vol. 406: 33–45, 2010

Record Information

Source Institution:
Florida International University
Rights Management:
Please contact the owning institution for licensing and permissions. It is the users responsibility to ensure use does not violate any third party rights.
Resource Identifier:
FI14082531
10.3354/meps08533 ( doi )