Despite the rapidly changing winter conditions in temperate ecosystems, little attention has been devoted to the effects of these changes on lake ecology. Few studies on the seasonal changes in abundance and biomass of the major groups of the metazooplankton community (i.e,. rotifers, cladocerans and copepods) in northern oligotrophic lakes include data from the ice-covered winter months. This study reports monthly variation in zooplankton abundance and biomass from June 2010 to October 2011, including winter, in an oligotrophic, subalpine lake in southeastern Norway (Lake Atnsjoen). Changes in rotifer, cladoceran, copepod, and total zooplankton abundances and biomass were related to seasonal variation in water temperature and phytoplankton biomass by means of ordination analysis. The zooplankton abundance and biomass were much lower in winter than during the open water season. However, an underice phytoplankton bloom occurred during the final winter months, when snow cover and ice thickness were reduced and (presumably) light penetration increased, leading to an increase in abundance of copepod nauplii. Winter zooplankton abundance was dominated by copepods and rotifers, while winter zooplankton biomass was dominated by copepods and cladocerans. Both phytoplankton and zooplankton had two biomass peaks in 2010 and one peak in 2011. Rotifers dominated zooplankton abundance with a peak in August and total zooplankton abundance followed a similar pattern. In contrast, cladocerans dominated zooplankton biomass with a peak in July and total zooplankton biomass also peaked at this time. Rotifer and total zooplankton abundance and rotifer biomass were most closely correlated to water temperature. However, cladoceran biomass and total biomass were most closely correlated with phytoplankton biomass, but also appeared to be dependent on other carbon sources. Estimates of non-phytoplankton particulate organic carbon indicated that this part of the carbon pool could be an additional food source for zooplankton particularly in early and mid-winter. The longer growing season in 2011 than in 2010, owing to earlier ice-off in 2011, may have contributed to higher phytoplankton and zooplankton biomass in 2011. With climate warming, this is an expected change in temperate lake ecosystems.

中文翻译：

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亚高山贫营养湖 Atnsjøen（挪威东南部）浮游动物丰度和生物量冬季减少

尽管温带生态系统的冬季条件迅速变化，但很少有人关注这些变化对湖泊生态的影响。很少有关于北部贫营养湖泊中浮游动物群落主要群体（即轮虫、枝角类和桡足类）丰度和生物量季节性变化的研究包括来自冰雪覆盖的冬季月份的数据。本研究报告了 2010 年 6 月至 2011 年 10 月（包括冬季）在挪威东南部一个贫营养亚高山湖泊（阿特斯乔恩湖）中浮游动物丰度和生物量的月度变化。通过排序分析，轮虫、枝角类、桡足类和浮游动物总丰度和生物量的变化与水温和浮游植物生物量的季节性变化有关。冬季浮游动物丰度和生物量远低于开放水域季节。然而，在最后一个冬季，冰下浮游植物大量繁殖，此时积雪和冰层厚度减少，（可能）光线穿透增加，导致桡足类无节幼体丰度增加。冬季浮游动物丰度以桡足类和轮虫为主，而冬季浮游动物生物量以桡足类和枝角类动物为主。浮游植物和浮游动物在 2010 年和 2011 年都有两个生物量峰值。轮虫主导浮游动物丰度，在 8 月达到峰值，浮游动物总丰度遵循类似的模式。相比之下，枝角类占主导地位的浮游动物生物量在 7 月达到峰值，浮游动物总生物量也在此时达到峰值。轮虫和浮游动物总丰度以及轮虫生物量与水温的相关性最密切。然而，枝角类生物量和总生物量与浮游植物生物量最密切相关，但似乎也依赖于其他碳源。对非浮游植物颗粒有机碳的估计表明，这部分碳库可能是浮游动物的额外食物来源，尤其是在初冬和中期。2011 年的生长季节比 2010 年更长，因为 2011 年冰消期提前，这可能导致 2011 年浮游植物和浮游动物生物量增加。随着气候变暖，这是温带湖泊生态系统的预期变化。枝角类生物量和总生物量与浮游植物生物量最密切相关，但似乎也依赖于其他碳源。对非浮游植物颗粒有机碳的估计表明，这部分碳库可能是浮游动物的额外食物来源，尤其是在初冬和中期。2011 年的生长季节比 2010 年更长，因为 2011 年冰消期提前，这可能导致 2011 年浮游植物和浮游动物生物量增加。随着气候变暖，这是温带湖泊生态系统的预期变化。枝角类生物量和总生物量与浮游植物生物量最密切相关，但似乎也依赖于其他碳源。对非浮游植物颗粒有机碳的估计表明，这部分碳库可能是浮游动物的额外食物来源，尤其是在初冬和中期。2011 年比 2010 年更长的生长季节，由于 2011 年更早的冰期，可能导致 2011 年浮游植物和浮游动物生物量增加。随着气候变暖，这是温带湖泊生态系统的预期变化。