Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Copyright: © 2011 Mora et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas

The structure of subtidal food webs in the northern Gulf of St. Lawrence, Canada, as revealed by the analysis of stable isotopes

We analyzed stable isotopes of carbon and nitrogen to investigate the trophic structure of the subtidal food web around the Mingan Islands, northern Gulf of St. Lawrence, eastern Canada. All benthic consumers were enriched in 13C (mean δ13C of –17.1‰) compared to particulate organic matter (POM: –23.3‰). Nitrogen stable isotope ratios ranged from 6‰ to 14‰ and the organisms studied fell into three distinct trophic groups, primary producers, primary consumers (herbivores), and predators. The sea star Crossaster papposus and the sculpin Myoxocephalus scorpius, known to be top level predators, had slightly higher δ15N than other predators. Although the average isotope signature of the sea star Solaster endeca placed it among regular predators, the δ15N increased with sea star size and large individuals could be considered as top predators. The relatively small number of organisms located at intermediate trophic levels suggests a low level of omnivory in the Mingan Islands’ system, which contrasts with previously described benthic systems that exhibit a continuum between herbivores and predators. Low omnivory, in addition to low diversity, suggests that this ecosystem may be relatively unstable if exposed to natural and/or anthropogenic disturbances such as exploitation and climate change