Extreme weather events strongly influence chironomid structure even in an artificially regulated reservoir

Interest in climate change-related water level fluctuations and their effects on aquatic communities has increased. Chironomids are reliable indicators of extreme conditions, yet whether climate-induced compositional changes occur in lakes with artificially regulated water levels, such as Lake Tisza, is unclear. We studied the direct and indirect effects of hydrological extremes and climatic factors on chironomid assemblages from 2009 to 2022, hypothesising that extremes drive compositional shifts and reduced diversity, with indirect effects more pronounced. Results confirmed this hypothesis, revealing a remarkable assemblage change over 14 years. Flooding during the growing period significantly altered habitat diversity, causing notable structural changes in chironomid assemblages. Compositional variability was more closely linked to environmental variables than to discharge or climatic variables. Oligotrophication emerged as the main driver of long-term trends. Diversity responded to environmental changes, declining after summer floods, but recovery was rapid, with no lasting diversity loss despite structural shifts. Projected increases in climate extremes suggest further alterations in chironomid composition and diversity. These processes may ultimately affect the food web and compromise the lake’s conservation function.

学界对气候变化相关水位波动及其对水生生物群落的影响愈发关注。摇蚊（Chironomids）是极端环境条件的可靠指示生物，但在蒂萨湖（Lake Tisza）这类受人工调控水位的湖泊中，是否会出现气候驱动的群落组成变化，目前尚不明确。本研究于2009年至2022年间，探究了水文极端事件与气候因子对摇蚊群落的直接与间接影响，提出假说：极端事件会推动群落组成发生偏移并降低多样性，且间接影响更为显著。研究结果验证了上述假说，揭示出14年间摇蚊群落发生了显著变化。生长期内的洪水显著改变了生境多样性，导致摇蚊群落结构出现明显变化。群落组成变异性与环境变量的关联度，显著高于径流或气候变量。寡营养化（Oligotrophication）成为长期变化趋势的主要驱动因子。群落多样性对环境变化存在响应：夏季洪水过后多样性出现下降，但恢复速度较快，尽管群落结构发生了改变，但并未出现持久性的多样性损失。气候极端事件的预计增加趋势，预示着摇蚊群落组成与多样性将发生进一步变化。上述过程最终可能会影响湖泊食物网，并损害其生态保护功能。