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

研究了木崎湖、Misuzu湖和Tamizo湖的水蚤冬季种群动态，其中Misuzu湖和Tamizo湖被冰覆盖。在木崎湖和Misuzu湖发现水蚤在冬季以自由个体的形式存活，表明低水温（<4℃）对水蚤种群的危害并不严重。然而，水蚤个体没有卵，因此种群在冬季的生产力很低。实验室实验表明，低水温和低食物丰度不会杀死水蚤，但会抑制其繁殖，但如果温度和食物密度增加，水蚤会迅速开始繁殖。这可能是水蚤种群在冬季生存和在春季与其他浮游动物物种竞争的一种策略。气候变暖必然使冬季水温升高。气候变暖导致的冬季湖水温度升高可能会扰乱水蚤的生存策略。在苏瓦湖的野外观测表明，桡足类棘足目和棘足目具有明显的季节演替特征，春季棘足目占优势，夏季棘足目占优势。为了评估温度对浮游动物群落季节演替的影响，在控制温度的实验室环境中维持浮游动物群落，并分析浮游动物群落结构的变化。在春季水温条件下，棘独眼虫在中生态中大量出现，而在夏季水温条件下，棘独眼虫数量较少。另一方面，在春季和夏季水温下，Eodiaptomus都处于优势地位。结果表明，苏瓦湖棘眼目种群的季节动态受水温的直接控制，而平眼目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.