Marine producers, consumers and climate change: From an ecological stoichiometry perspective

participantEcological stoichiometry is a rapidly expanding research field investigating how the elemental composition of organisms affects ecological processes. Owing to the fact that the ratios of carbon (C) :nitrogen (N) : phosphorus (P) are different among aquatic organisms, their recycling nutrients may thus affect the supply and the stoichiometry of C, N and P in the ocean. In contrast, the changing ocean (e.g. by climate change and human perturbation) may also affect the C:N:P stoichiometry of the ocean, and eventually the C:N:P of those organisms living in the ocean. Here, we investigated the impact of consumer-driven nutrient recycling (CNR) on oceanic primary production and the distribution of nitrogen (N) and phosphorus (P) in the deep ocean. For this purpose, we used and extended two existing models: a 2-box model of N and P cycling in the global ocean (Tyrrell, 1999), and the model of Sterner (Sterner, 1990) which formalised the principles of CNR theory. The resulting model showed that marine herbivores may affect the supply and the stoichiometry of N and P in the ocean, thereby exerting a control on global primary production. The predicted global primary production was higher when herbivores were included in the model, particularly when these herbivores had higher N:P ratios than phytoplankton. The potential impacts of climate change on the C and nutrient availability in aquatic ecosystems, its consequences for the C:N:P stoichiometry of plankton communities, and its implications for the structure of aquatic food webs are briefly discussed