A role of thermocline on biological activities in Lake Biwa.

温跃层对琵琶湖生物活动的作用。

• 批准号: 06304048
• 负责人: NAKANISHI Masami
• 金额: $ 11.14万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Co-operative Research (A)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06304048/
• 关键词: thermocline; water shortage; precipitation; plankton; nutrients; matter transport; Lake Biwa; biological activities; 植物プランクトン; 生物生産; 分解; 再溶出; PH

Vertical distribution of chlorophyll a differedl in the pattern between September 1994 when it was extraordinarily water shortage and September 1995 when it was a usual rain. In 1994, chlorophyll a was extremely low in the epilimnion and showed a peak in the thermocline. Phytoplankton growth was interrupted in the epilimnion because of nutrients deficiency due to shortage of river inflow. As a result, solar radiation available for photosynthesis could penetrate sufficiently into the thermocline. Nitrate-N was gradually supplied by the upward diffusion from the hypolimnion to the thermocline and phosphate-phosphorus was supplied continuously by release of phosphate from the phosphorus adsorbed with ferric iron and alminium in the turbid water transperted from share-bottom into the thermocline. In 1995, river water including rich nutrients inflowed just above the thermocline and supplied nutrients to the epilimnion. As a result, phytoplankton growth was enhanced in combination with photosynthesis in the epilimnion. Vertical distribution pattern of chlorophyll a seems to be determined by whether or not nutrients are supplied from river to the epilimnion.

叶绿素垂直分布在1994年9月极度缺水至1995年9月常雨期间的格局中变化不大。1994年，叶绿素a在表层极低，在温跃层出现峰值。浮游植物生长中断的上层，因为营养缺乏，由于河流入流不足。因此，可用于光合作用的太阳辐射可以充分穿透到温跃层。硝态氮由下层向温跃层的向上扩散逐渐提供，而磷-磷则由底层向温跃层输送的浊水中的三价铁和三价铝吸附的磷释放而不断提供。1995年，含有丰富营养盐的河水流入温跃层上方，为上层提供营养盐。因此，浮游植物的生长与光合作用相结合，在上层得到加强。叶绿素a的垂直分布格局似乎取决于营养盐是否从河流供应到表层。

项目成果

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Kenji Okubo、Yoshio Muraki、Hiroshi Morikawa：“琵琶湖水温和浊度波动的机制”京都大学防灾研究所年度报告 37. 405-419 (1994)。

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