Modest increase in the C:N ratio of N-limited phytoplankton in the California Current in response to high CO2

Marine Ecology Progress Series

Jenna L. Losh¹  Francois M. M. Morel¹  Brian M. Hopkinson¹ 

关键词: CO2;    Phytoplankton;    C:N ratios;    N-limitation;    RuBisCO;   

DOI  :  10.3354/meps09981

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: In a fall 2008 cruise off the coast of California, on-deck incubations with surface seawater were conducted to compare the effect of increasing carbon dioxide (CO₂) on nitrogen (N)-limited versus N-replete (+ NO₃⁻) phytoplankton. Based on previous laboratory studies, we expected that under N-limitation C:N ratios would be more sensitive to CO₂ availability. In particular, we wanted to test whether down-regulation of RuBisCO at high CO₂ leads to an increased C:N ratio, since RuBisCO is thought to be a large pool of N in many autotrophs. In 4 out of 5 Nlimited experiments, the C:N ratio of phytoplankton biomass increased slightly from low to high CO₂, and this increase was due chiefly to an increase in particulate organic carbon (POC), with little change in particulate organic nitrogen (PON). In contrast, the N-replete experiments did not show a change in C:N ratio, but some experiments exhibited higher rates of carbon fixation and growth at high CO₂. In the one N-limited experiment that did not show a change in C:N ratio with CO₂, the ambient population had a higher proportion of cyanobacteria compared with the other experiments. The concentration of RuBisCO decreased at high CO₂ in several N-limited experiments, but this reduction only accounted for a minor proportion of the overall change in C:N ratio. An increase in C:N ratios at high CO₂ in N-limited phytoplankton could provide negative feedback to increasing atmospheric CO₂.

【 授权许可】

Unknown