Food chains (Ecology)

We collected, with FWC, taxa inventory and numerical abundance data at three sites, a restoration concurrent with sampling, an older completed restoration, and an unimproved reference site, from 2014 to 2018 in the Central Lake Worth Lagoon, Florida. We examined effects in response to estuary habitat restoration and water quality on nekton food web structure among sites over time. A binary matrix of plausible interactions among trophic species, classified by size, was used to produce 51 individual food webs and nine trophic structure metrices within the R: Package Cheddar. Interactions of site and restoration, i.e., pre- vs. post-restoration samples, were found to be not significant in repeated-measures ANOVAs for each food web metric. Random forest analysis only identified Secchi depth as an important predictor of food web generality. Our findings suggest that generality and Secchi depth are inversely correlated and relatively stable within the Central Lake Worth Lagoon sites.

The effect of artificial reefs on natural reefs is poorly understood. This study focused on Aquarius Reef Base (ARB), an underwater habitat offshore of Key Largo, Florida, and 14 natural reef sites spanning 4 habitats, on the surrounding Conch Reef. Food web models were created for ARB and natural reef habitats. Biomass at each habitat was quantified by fish surveys. Using Ecopath, species were organized into functional groups with supporting data from previous research for other inputs. ARB’s food web was found to have a large predator biomass with insufficient prey biomass to sustain the population, suggesting that these predators must forage on nearby natural reefs where the predator/prey ratio is smaller. Between 0.57km2 and 1.79km2 of natural reef is estimated to be a sufficient spatial subsidy for the large predatory biomass at ARB when the biomass is added as determined by the seascape around the artificial reef.

Stable carbon and nitrogen isotope ratios were analyzed to investigate the trophic linkages between primary producers and consumers in fringing mangrove ecosystems of The Bahamas and Biscayne Bay, Florida. The isotope ratios, in conjunction with stomach content analysis, were used to trace the flow of organic matter from the primary organic sources (mangroves, seagrass and macro-algae) to primary consumers and ultimately to the gray snapper (Lutjanus griseus). We found the mean delta^13C value of the primary consumers (-17.1%) to be closely related to the mean values of the macro-algal material (-16.7%) and the seagrass (-10.5%) with very little correlation to the carbon signature of mangroves (mean = -27.4%). Our results suggest the ultimate source of carbon for the primary and secondary consumers, located at our study sites, is algal and seagrass material, individually or possibly as a mixture, and that mangroves are not the sole source of carbon in these systems.