Experimental analysis on the impact of climatic warming on lake plankton communities.

对木崎湖、三铃湖和田沟湖的枝角水蚤冬季种群动态进行了调查，其中两个湖（三铃湖和田沟湖）被冰覆盖。研究发现，木崎湖和三铃湖冬季水蚤以自由生活个体的形式存活下来，这表明低水温（<4℃）不会对水蚤种群造成严重损害。然而，水蚤个体没有卵，因此冬季种群生产力低下。实验室实验表明，低水温和低食物丰度不会杀死水蚤，而是抑制其繁殖，但如果温度和食物密度增加，水蚤就会迅速开始繁殖。这可能是水蚤种群度过冬季并在春季与其他浮游动物物种竞争的策略。气候变暖必须提高冬季水温。人们认为，气候变暖导致冬季湖水温度升高可能会扰乱水蚤的策略。诹访湖的实地观察表明，桡足类棘突龙和始突龙表现出明显的季节演替：前者在春季占优势，后者在夏季占优势。为了评估温度对其季节演替的影响，将浮游动物群落维持在实验室的中生态系统中，控制温度，并分析浮游动物群落结构的变化。随着春季水温的变化，棘突眼虫大量出现在中层环境中，而随着夏季水温的变化，棘突眼虫则不大量出现。另一方面，Eodiaptomus 在春季和夏季水温下都占主导地位。结果表明，诹访湖棘突眼虫种群的季节动态直接受晶片温度控制，而始甲鱼种群的季节动态则通过温度介导的生物相互作用间接控制。

The winter population dynamics of the cladoceran Daphnia were investigated in Lakes Kizaki, Misuzu and Tamizo, of which two lakes (Misuzu and Tamizo) were covered with ice. It was found that Daphnia survived as free-living individuals during winter in Lakes Kizaki and Misuzu, suggesting that the low water, temperature (<4℃) does not give serious damage to the Daphnia populations. However, the Daphnia individuals had no eggs and therefore the populations had low productivities in winter. Laboratory experiments have shown that low water temperature and low food abundance do not kill Daphnia but suppress their reproduction, but that the Daphnia start reproduction rapidly if temperature and food density increases. This may be a strategy of the Daphnia populat ions to survive winter and competition with other zooplankton species in spring. Climatic warming must increase water temperature in winter. It is considered that the increased lake water temperature in winter due to climatic warming may disturb the Daphnia's strategy.Filed observation in Lake Suwa has demonstrated that the copepods Acanthcyclops and Eodiaptomus show clear seasonal succession : Dominance of the former in spring to that of the latter in summer. In order to assess the impact of temperature on their seasonal succession, zooplankton communities were maintained in mesocosms in the laboratories, where temperatures were controlled, and changes in the zooplankton community structure were analyzed. Acanthcyclops appeared abundantly in the mesocosms with the spring water temperatures while did not with the summer water temperatures. On the other hand, Eodiaptomus became dominant both under the spring and summer water temperatures. The results have suggested that seasonal dynamics of the Acanthcyclops population in Lake Suwa are controlled directly by wafer temperature, while that those of the Eodiaptomus population are done indirectly through biological interactions mediated by temperature.