UW Aquatic & Fishery Sciences Quantitative Seminar

Jake Allgeier

School of Aquatic and Fishery Sciences, University of Washington

Understanding drivers of variability in consumer mediated nutrient supply (fish pee) in coral reef ecosystems

Abstract

Animals are now widely regarded as important mediators of nutrients fluxes in ecosystems, providing an alternative means for understanding the ecological implications of changing animal communities and biodiversity loss. Here I discuss recent research on nutrient supply from fish communities in coral reef ecosystems and the relative importance of biodiversity in the maintenance of these processes. Fish communities are likely among the largest sources of nutrients in coral reef ecosystems. Fish-derived nitrogen (N) and phosphorus (P) are highly variable across a broad geographic range of coral reef ecosystems in the northern Caribbean, but the ratio of these nutrients is remarkably similar across reefs (N:P ~20:1). This ratio coincides with the relative proportions of N and P that are optimal for coral growth, suggesting the ratio, rather than individual nutrient concentrations may be of greater ecological relevance. Statistical analyses and simulations suggest that single nutrient input is highly regulated by the number of species and the biomass of the community, but these relationships do not explain patterns in N:P supply. Time series of fish communities on 26 reefs in The Bahamas demonstrate higher stability in supply ratio (N:P) in contrast to N or P independently. Findings generally contrast biodiversity theory suggesting that the fish community size structure is more important in the maintenance of nutrient supply ratios than the number of species present.