Running Head: Spatial Aggregations Regulate Community
Kelly Benoit Bird, Oregon State University
The importance of spatial pattern in ecosystems has long been recognized. However, incorporating patchiness into our understanding of forces regulating ecosystems has proven challenging. We used a combination of continuously sampling moored sensors, complemented by shipboard sampling, to measure the temporal variation, abundance, and vertical distribution of four trophic levels in Hawaii's nearshore pelagic ecosystem. Using an analysis approach from trophic dynamics, we found that the frequency and intensity of spatial aggregations, rather than total biomass, in each step of a food chain involving phytoplankton, copepods, mesopelagic micronekton, and spinner dolphins (Stenella longirostris) were the most significant predictors of variation in adjacent trophic levels. Patches of organisms had impacts disproportionate to the biomass of organisms within them. Our results are in accordance with resource limitation - mediated by patch dynamics - regulating structure at each trophic step in this ecosystem, as well as the foraging behaviour of the top predator. Because of their high degree of heterogeneity, ecosystem-level effects of patchiness like this may be common in many pelagic marine systems. Long-term deployments of similar, moored technologies at several sites around the globe (the Ocean Observing Initiative) will help determine the role of heterogeneity in marine systems. However, because most marine ecosystems are not tightly coupled to geography, new approaches to sustained mobile sampling of plants and animals will be a critical component of understanding ecological processes in the ocean.
Background Review Article:
Witze, A. "Marine science: Oceanography's billion-dollar baby." Nature 501.7468 (2013): 480-482.