Influence of consumer-driven nutrient recycling on primary production and the distribution of N and P in the ocean

[摘要] In this study we investigated the impact of consumer-driven nutrientrecycling (CNR) on oceanic primary production and the distribution ofnitrogen (N) and phosphorus (P) in the deep ocean. For this purpose, we usedand extended two existing models: a 2-box model of N and P cycling in theglobal ocean (Tyrrell, 1999), and the model of Sterner (1990)which formalised the principles of CNR theory. The resulting model showed thatmarine herbivores may affect the supply and thestoichiometry of N and P in the ocean, thereby exerting a control on globalprimary production. The predicted global primary production was higher whenherbivores were included in the model, particularly when these herbivoreshad higher N:P ratios than phytoplankton. This higher primary production wastriggered by a low N:P resupply ratio, which, in turn, favoured theP-limited N₂-fixation and eventually the N-limited non-fixers.Conversely, phytoplankton with higher N:P ratios increased herbivore yielduntil phosphorus became the limiting nutrient, thereby favouring herbivoreswith a low P-requirement. Finally, producer-consumer interactions fed backon the N and P inventories in the deep ocean through differential nutrientrecycling. In this model, N deficit or N excess in the deep ocean resultednot only from the balance between N₂-fixation and denitrification, butalso from CNR, especially when the elemental composition of producers andconsumers differed substantially. Although the model is fairly simple, theseresults emphasize our need for a better understanding of how consumersinfluence nutrient recycling in the ocean.

[学科分类] 地球化学与岩石