Journal
ECOLOGICAL MONOGRAPHS
Volume 88, Issue 4, Pages 585-599Publisher
WILEY
DOI: 10.1002/ecm.1324
Keywords
arachidonic acid; docosahexaenoic acid; drought; egg production; eicosapentaenoic acid; freshwater inflow; nutritional ecology; red drum; reproduction; Sciaenops ocellatus; trophic transfer; trophodynamics
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Funding
- Perry R. Bass Chair in Fisheries and Mariculture endowment at the University of Texas Marine Science Institute
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Flow of essential fatty acids (EFAs) through food webs is critical for the health of individual animals, populations, and communities. Planktonic eggs may play a central role in marine systems because they are highly concentrated in EFAs, superabundant, and consumed by a variety of species. Previous research suggests that egg fatty acid composition should not be useful for trophodynamic studies because it should be tightly regulated to meet the nutritional needs of embryos. Eight years of sampling the egg boon of the teleost fish red drum (Sciaenops ocellatus) provided the opportunity to test the hypothesis that extreme climatic events differentially alter abundances of prey populations and, ultimately, egg fatty acid composition. Fatty acid composition of eggs varied significantly among years and three major patterns of interannual variation (principal components) paralleled trends in the Palmer Drought Severity Index. Each of the first three principal components was related to abundances of particular prey (blue crabs, filter-feeding fishes, and brown shrimp, respectively) during the spring and summer. Summer abundances of blue crab and brown shrimp were most strongly correlated with bay salinity 12-14 months earlier. Summer abundances of filter-feeding fishes were most strongly correlated with bay salinity 0-1 month earlier. The delayed responses of crustacean abundances to variations in bay salinity likely operate through variability in recruitment. The fast connection for filter-feeding fishes suggests a behavioral response to changing environmental conditions. The analyses revealed changes in trophodynamic flow that were associated with the phases of the climatic event. EFA content of eggs increased during drought years then decreased in the recovery years, indicating the potential for downstream effects on reproductive output, offspring viability, and tissue composition of egg consumers. Generally, nutrients move from intermediate sized consumers to a larger, higher order consumer (adult red drum). Then, trophic flow reverses when the egg boon is exploited by smaller planktivores. The analysis also revealed climate-related shifts in the degree of benthic-pelagic coupling and pelagic recycling that were mediated by the egg boons. This study demonstrates that egg boons can be a useful subject for investigations of trophodynamics in marine ecosystems.
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