Dissolved organic matter (DOM) is an important component of nutrient cycling, but the role of different organisms controlling the processing of autochthonous DOM remains poorly understood. Aiming to characterize phytoplankton-derived DOM and the effects of complex pelagic communities on its dynamics, we incubated natural plankton communities from a temperate mesohaline estuary under controlled conditions for 18 days. The incubations were carried out in contrasting seasons (spring and autumn) and changes in the planktonic community (phytoplankton, bacteria and microzooplankton), nutrients and DOM were assessed. Our results highlight the complexity of DOM production and fate in natural planktonic communities. Small changes in DOM composition were observed in the experiments relative to the orders-of-magnitude variations experienced in the phytoplankton assembly. We argue that the tight coupling between microbial processing and DOM production by phytoplankton and grazers stabilizes variations in quantity and characteristics of autochthonous DOM, resulting in apparently homogeneous semi-labile DOM pool throughout the experiments. However, seasonal differences in the production and processing of DOM were observed, reflecting differences in the nutrient regimes and initial DOM characteristics in each experiment, but also likely influenced by changes in the successional status of the pelagic community. Acknowledging that characteristics of the DOM derived from phytoplankton growth can vary broadly, heterotrophic processing and successional status of the community are synergistically important factors for shaping those characteristics, and thus affecting the seasonal signature of the semi-labile autochthonous DOM pool.

溶解性有机物（DOM）是养分循环的重要组成部分，但对控制机体DOM的不同生物的作用仍知之甚少。为了表征浮游植物衍生的DOM及其复杂的中上层群落对其动态的影响，我们在受控条件下温育了温带中卤河口的天然浮游生物群落18天。在不同的季节（春季和秋季）进行孵化，并评估浮游生物（浮游植物，细菌和微浮游动物），营养物质和DOM的变化。我们的结果突出了自然浮游生物群落中DOM生产和命运的复杂性。相对于浮游植物组装体中经历的数量级变化，在实验中观察到DOM组成的微小变化。我们认为，浮游植物和放牧者的微生物加工与DOM生产之间的紧密联系稳定了本地DOM数量和特征的变化，从而在整个实验过程中产生了明显均质的半不稳定DOM库。然而，观察到DOM产生和加工的季节性差异，反映了每个实验中养分制度和初始DOM特性的差异，但也可能受中上层群落演替状态变化的影响。确认浮游植物生长所产生的DOM的特性可能有很大差异，