Organic matter partitioning and stoichiometry in response to rising water temperature and copepod grazing

Marine Ecology Progress Series

Antje Biermann¹  Aleksandra M. Lewandowska¹  Anja Engel¹  Ulf Riebesell¹ 

关键词: Climate change;    Ocean warming;    Phytoplankton spring bloom;    Copepods;    Mesocosm study;    Organic matter;    Transparent exopolymer particles;    TEP;    Nutrient recycling;   

DOI  :  10.3354/meps11148

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: Rising ocean temperature is expected to change the balance between production and degradation of organic matter due to different temperature sensitivities of auto- and heterotrophic processes. Copepods are the most prominent zooplankton group, and elevated temperature increases their growth and grazing rates. So far, it is unknown to what extent copepods affect the partitioning and stoichiometry of organic matter in a warmer surface ocean. We therefore conducted a mesocosm experiment with 3 copepod densities and 2 temperature scenarios to determine effects on the pools of dissolved and particulate organic matter and their C:N:P ratios. Here we show that particulate organic C (POC) concentrations decreased with increasing copepod abundance. This effect was more pronounced at elevated temperature, yielding a decrease in the POC to particulate nitrogen ratio (POC:PN) from 26 to 13 and in the POC:particulate organic phosphorus (POP) ratio from 567 to 257, from low to high copepod density. Dissolved organic carbon (DOC) accumulation was positively affected by temperature. However, increasing copepod abundance decreased the accumulation of DOC at elevated temperature. Copepod grazing and egestion enhanced the recycling of N and P, thereby increasing the availability of these nutrients for autotrophs. In concert with temperature-induced shifts in the phytoplankton community composition and size, changes in copepod abundance may therefore have contributed to altering the elemental composition of seston. Our findings suggest combined effects of zooplankton grazing and temperature on the composition and recycling of organic matter that should be taken into account when simulating biogeochemical cycles in a future ocean.

【 授权许可】

Unknown