Biological Productivity of Rio Doce Valley Lake System, Brazil

1987年6月至7月进行了研究，目的是澄清多塞河谷湖泊在旱季的湖泊特征。浮游植物的氮源大部分是氨。浮游植物优先利用氨和尿素。含氮营养物的再生形式对湖泊生光层浮游植物的氮源具有重要作用。基于脂肪酸组成研究了Dom Helvecio湖和Amarela湖大量沉积有机质的成藏机制。在表层沉积物中，陆源贡献约为90 mg C/g，而Dom Helvecio湖和Amarela湖的本地贡献分别约为50和110 mg C/g。测定了半应生植物天葵的生物量。平均出芽期为8.7 ~ 11.0 d。叶片寿命的平均值估计为70 ~ 74天。蒸汽的寿命估计为2年零4个月。研究了多姆·赫尔维西奥湖（Dom Helvecio Lake）潮鸟的日、日羽化规律。其中一颗超牛座显示出最高的捕获率，达到了总体的96%，这主要出现在新月之夜。在日出之前，物种的出现较为活跃。该物种在月循环下的生长同步性很强。调查期间共捕获11科16种260余条鱼类。与1985年的结果相比，除阿马雷拉湖外，其他湖泊的物种多样性和鱼类相对丰度均有所下降。作者认为，卡里奥卡湖鱼类群落的剧烈变化是由1985年引进的土库纳鱼（Cichla ocellaris）的捕食效应引起的。

The study was carried out from June to July 1987 to clarify the limnological feature of the Rio Doce valley Lakes in dry season.1. The greater part of the nitrogen source for phytoplankton was ammonia. The phytoplankton preferentially utilized ammonia and urea. the regenerated forms of nitrogenous nutrients played significant role as nitrogen source for phytoplankton in the euphotic layer in lakes.2. The accumulation mechanism of large quantities of sedimentary organic matter in Lakes Dom Helvecio and Amarela were studied based on the fatty acids composition. In both the surface sediments, about 90 mg C/g dry sediment was derived from terrigenous sources, and the autochtonous contributions in Lakes Dom Helvecio and Amarela were about 50 and 110 mg C/g dry sediment respect-ively.3. The biomass production of a semi-emergent plant Eichhornia azurea Kunth was determined. The mean rate of leaf emergence was 8.7 to 11.0 days. The mean value of the life span of leaves was estimated as 70 to 74 days. The life span of the steam was estimated as 2 years and 4 months.4. Diurnal and diel emergence patterns of chaoborids were investigated in Lake Dom Helvecio. One of Chaoborus showed the highest catch up to 96 % of the overall, which emerged largely on the night of a new moon. Emergence of species occureed actively before sunrise. The synchronization of growth of this species under the luner cycle is stronglyh suggested.5. More than 260 fish belonging to 16 species (11 families) were obtained during the survey period. Comparing with results in 1985, both species diversity and relative abundance of fish were decreased in all the lakes except Lake Amarela. The authors concluded that the drastic change observed in the fish community of Lake Carioca was caused by the predation effect of the Tucunare (Cichla ocellaris) introduced in 1985.