富营养化湖泊中鱼类对碳循环的影响机制

Impact Mechanisms of Fish on Carbon Cycling in Eutrophic Lakes

摘要: 富营养化背景下，鱼类通过摄食、代谢排泄与底质扰动三条途径调控湖泊碳循环，其协同与拮抗共同决定净效应。滤食性鱼类控藻抑制碳固定，杂食性鱼类经营养级联改变碳的固定与传递，排泄的碳、氮、磷协同促进浮游植物生长与微生物矿化，再悬浮与生物灌溉改变沉积碳埋藏与温室气体产生并抑制产甲烷。三条途径的权重随营养状态偏移，贫营养水体偏碳汇，富营养水体偏碳源。净效应受营养盐负荷、群落结构与生物量、热力分层、沉积物性状及时间尺度共同调控，并呈尺度依赖性。在此基础上构建了三类功能群影响组合的概念模型。针对效应分离、尺度扩展、过程量化与功能性状数据四方面不足，提出了原位围栏与室内模拟互验、野外对比叠加长期观测、界面通量与电子受体剖面同步测定的研究路径，为富营养化湖泊治理与碳汇提升提供依据。

Abstract: Under eutrophic conditions, fish regulate lake carbon cycling through feeding, metabolic excretion and sediment disturbance, whose synergy and antagonism jointly determine the net effect. Filter-feeding fish suppress carbon fixation by grazing phytoplankton, omnivorous fish reshape carbon fixation and transfer through trophic cascades, the excretion of carbon, nitrogen and phosphorus synergistically promotes phytoplankton growth and microbial mineralization, and resuspension and bioirrigation alter sediment carbon burial and greenhouse gas production while suppressing methanogenesis. The weights of the three pathways shift with trophic state, oligotrophic waters tending towards carbon sinks and eutrophic waters towards carbon sources. The net effect is jointly regulated by nutrient loading, community structure and biomass, thermal regime, sediment properties and time scale, and is scale dependent. A conceptual model of the effect combinations of the three functional groups is developed accordingly. To address the deficiencies in effect separation, upscaling, process quantification and functional-trait data, a research framework is proposed that cross-validates in situ enclosures with laboratory simulations, combines field comparisons with long-term observations, and measures interfacial fluxes and electron acceptor profiles synchronously, providing a basis for eutrophic lake management and carbon sink enhancement.