DATA for ''Dissolved organic matter mediates the effects of warming and inorganic nutrients on a lake planktonic food web'' DOI: 10.1002/LNO.12177

Abstract: Lakes are undergoing striking physicochemical changes globally, including co-occurring increases in dissolved organic carbon and nutrient concentrations, water color, and surface temperature. While several experimental studies of lake browning and warming have been conducted over the last decade, knowledge remains limited as to the structural and functional responses of multitrophic plankton communities, especially under environmentally relevant physicochemical conditions. Using reverse osmosis to manipulate naturally-occurring dissolved organic matter (DOM), we performed an enclosure experiment to evaluate the response of a planktonic food web (zooplankton–phytoplankton–bacterioplankton) to individual and combined increases in DOM and temperature, while accounting for changes in inorganic nutrients associated with DOM enrichment. We found that concomitant increases in DOM and temperature or inorganic nutrients elicited substantially greater biotic effects, but infrequently led to interactive effects. Overall, major plankton groups responded differently to manipulated factors, with most effects observed in standing stocks, community composition, and trophic structure, while metabolic (primary production and respiration) rates appeared to be generally less responsive. DOM enrichment had a clear stimulatory effect on phytoplankton, but weakly affected zooplankton. More specifically, DOM enrichment, alone or combined with inorganic nutrient amendments, decreased zooplankton:chlorophyll-<em>a</em> ratios, implying a reduced trophic transfer efficiency and altered trophic structure. Warming generally increased bacterial abundance and cyanobacterial dominance, especially under DOM-enriched conditions. Collectively, these results demonstrate that increasing local DOM, even by only ~2 mgC/L, can enhance plankton responses to rising temperature or inorganic nutrients in the near-surface layer of a clearwater lake, with potential implications for ecosystems facing co-occurring environmental changes.

摘要：全球范围内的湖泊正经历显著的理化变化，包括溶解有机碳与营养盐浓度、水体色度及表层水温的同步上升。过去十年间，已有多项针对湖泊褐变与增温的实验研究，但学界对多营养级浮游生物群落的结构与功能响应的认知仍较为有限，尤其是在符合环境现实的理化条件下。本研究利用反渗透技术调控天然溶解有机质（dissolved organic matter, DOM），开展原位围隔实验，以探究浮游食物网（浮游动物-浮游植物-浮游细菌）对DOM与温度单独及联合升高的响应，同时考量DOM富集所伴随的无机营养盐变化。研究发现，DOM、温度或无机营养盐的协同升高会引发显著更强的生物效应，但交互效应并不常见。整体而言，主要浮游类群对调控因子的响应存在显著差异，多数效应体现在现存量、群落组成及营养结构上，而代谢速率（初级生产与呼吸作用）通常响应较弱。DOM富集对浮游植物具有显著的促进作用，但对浮游动物的影响较弱。具体而言，单独或联合添加无机营养盐的DOM富集处理会降低浮游动物与叶绿素a的比值，这意味着营养传递效率下降且营养结构发生改变。增温通常会提升细菌丰度与蓝藻的优势度，在DOM富集的条件下这一效应尤为显著。综合来看，本研究结果表明，即使仅提升约2 mgC/L的原位DOM浓度，也能增强清水湖泊近表层水体中浮游生物对温度上升或无机营养盐升高的响应，这对面临多重环境变化的生态系统具有潜在的生态学意义。