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

Abstract

Abstract. In this study 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 (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. This higher primary production was triggered by a low N:P resupply ratio, which, in turn, favoured the Plimited N 2 -fixation and eventually the N-limited non-fixers. Conversely, phytoplankton with higher N:P ratios increased herbivore yield until phosphorus became the limiting nutrient, thereby favouring herbivores with a low P-requirement. Finally, producer-consumer interactions fed back on the N and P inventories in the deep ocean through differential nutrient recycling. In this model, N deficit or N excess in the deep ocean resulted not only from the balance between N 2 -fixation and denitrification, but also from CNR, especially when the elemental composition of producers and consumers differed substantially. Although the model is fairly simple, these results emphasize our need for a better understanding of how consumers influence nutrient recycling in the ocean.

Global nutrient cycling by commercially-targeted marine fish

“…Even though taxonomy, diet, ontogeny, and body nutrient content also influence fish recycling (e.g., Vanni and McIntyre, 2016;Allgeier et al, 2015;El-Sabaawi et al, 2016; Fe cycling computed from the weighted spatial variation between the low and high Fe:C values of zooplankton, and the weighted spatial variation between the averaged Fe:C ratios of phytoplankton in Fe-poor and Fe-rich conditions. Moody et al, 2015;Pilati and Vanni, 2007;Nugraha et al, 2010) these were not included in our study apart from the uncertainty on zooplankton nutrient content (Table 1). Finally, fish movements also allow the transport of nutrients and constitute a sink of nutrients where the fish forage and a source of nutrients where the fish excrete, egest or die (Vanni et al, 2013;Francis and Côté, 2018), an effect we do not explicitly include here.…”

Comment on bg-2021-251

“…Even though taxonomy, diet, ontogeny, and body nutrient content also influence fish recycling (e.g., Vanni and McIntyre, 2016;Allgeier et al, 2015;El-Sabaawi et al, 2016; variation between the averaged Fe:C ratios of phytoplankton in Fe-poor and Fe-rich conditions. Moody et al, 2015;Pilati and Vanni, 2007;Nugraha et al, 2010) these were not included in our study apart from the uncertainty on zooplankton nutrient content (Table 1). Finally, fish movements also allow the transport of nutrients and constitute a sink of nutrients where the fish forage and a source of nutrients where the fish excrete, egest or die (Vanni et al, 2013;Francis and Côté, 2018), an effect we do not explicitly include here.…”

C, N and P stoichiometric mismatch between resources and consumers influence the dynamics of a marine microbial food web model and its response to atmospheric N and P inputs

“…Several reasons suggest that stoichiometric constrains within food web can influence the response of marine microbial food webs to nutrient addition from dust. First, there are accumulating evidences that nutrient cycling mediated by consumers could determine the limiting nutrient for producer growth in the ocean (Le Borgne, 1982;Hjerne and Hansson, 2002;Steinberg et al, 2008;Pitt et al, 2009;Nugraha et al, 2010). Second, natural mortality rates of small marine prokaryotes and eukaryotes are primarily driven by either viral lysis or grazing (Calbet, 2001;Landry and Calbet, 2004), which results in a rapid turnover of chemical elements at the surface of the ocean.…”