ABSTRACT: The Ría de Vigo is a dynamic and productive upwelling ecosystem. We measured ¹⁴C incorporation (TO¹⁴CP) and gross primary production (GPP), community respiration (DCR), net production (NCP) and size-fractioned chlorophyll a (chl a) fortnightly from May 2012 to May 2013 in the euphotic layer of the Ría. Our aim was to improve the depiction of plankton metabolism in the Ría and to test the general hypothesis that community structure determines the degree of heterotrophy in planktonic ecosystems. Higher primary production was measured after upwelling episodes and during the spring bloom, when the community was dominated by microphytoplankton (>70% chl a_>20μm). Lower primary production was observed during summer stratification periods (~65% chl a_>20μm), and during the pico- and nanophytoplankton-dominated winter (~25% chl a_>20μm). Coupling between phytoplankton photosynthesis and biomass varied seasonally, mainly driven by environmental conditions. DCR was 3 times lower and 8 times less variable than GPP, and its variability was mainly driven by the changes in chl a. The integrated metabolic balance was autotrophic most of the year, despite the negative NCP rates at depth. There was an inverse relationship between the DCR:GPP ratio and the percentage of microphytoplankton (% chl a_>20μm) only in the summer. However, DCR:GPP and DCR:chl a ratios were similar in winter and spring, despite the seasonal differences in primary production and size structure. The similar TO¹⁴CP:NCP and chl a:DCR relations in spring (>70% chl a_>20μm) and winter (~25% chl a_>20μm), and the differences in summer (>70% chl a_>20μm) confirm cell size independence in trophic functioning. We conclude that respiration variability is relevant for the metabolic balance in the Ría, and that the degree of heterotrophy is not systematically related to phytoplankton size over the scales of our study.

中文翻译：

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维阿河地区浮游植物细胞大小的季节性及其与光合作用和呼吸的关系（西班牙西北部）

摘要：维加河是一个充满活力且富有成效的上升流生态系统。我们从2012年5月至2013年5月每两周测量了富营养层中¹⁴ C的掺入量（TO ¹⁴ CP）和主要初级生产量（GPP），社区呼吸（DCR），净产量（NCP）和大小分级的叶绿素a（chl a）。里亚。我们的目的是改善Ría中浮游生物代谢的描述，并检验群落结构决定浮游生态系统异养程度的一般假设。在上涌事件发生后和春季开花期间，当该群落以微浮游植物为主（> 70％chl a _>20μm）时，测得较高的初级生产力）。在夏季期间分层观察到降低的初级生产（〜65％叶绿素一_{> 20微米}），以及在微微和浮游植物为主的冬季（〜25％叶绿素一_{> 20微米}）。浮游植物光合作用和生物量之间的耦合季节性变化，主要受环境条件驱动。DCR的可变性比GPP低3倍，可变性低8倍，其可变性主要由chl a的变化决定。尽管深层NCP速率为负值，但一年中大部分时间里，综合代谢平衡仍是自养的。仅在夏季，DCR：GPP比率与微浮游植物的百分比（％chl a _>20μm）之间存在反比关系。然而，DCR：GPP和DCR：CHL一尽管初级生产和规模结构存在季节性差异，但冬季和春季的比率相似。在类似于¹⁴ CP：NCP和CHL一：春天DCR关系（> 70％CHL一_{> 20微米}）和冬季（〜25％叶绿素一_{> 20微米}），夏季（> 70％CHL的差异一_{> 20微米}）确认营养功能中的细胞大小独立性。我们得出的结论是，呼吸变化与Ría中的代谢平衡有关，并且在我们研究的范围内，异养的程度与浮游植物的大小没有系统地相关。