Agency of Bioresources Management, Ministry of Nature Protection, Government Building 3, Republic Square, 0010 Yerevan, Armenia.
Environ Monit Assess. 2012 Nov;184(11):6647-71. doi: 10.1007/s10661-011-2449-0. Epub 2011 Dec 27.
Water levels of Lake Sevan (Armenia) were artificially lowered by nearly 20 m between 1949 and 1997. Lowered water levels, combined with increased eutrophication, were associated with seasonally anoxic conditions (lasting 1-4 months) near the bottom of the profundal zone each year during 1976-2004. In addition, the extents of the macrophyte zone and of certain substrate types were severely reduced following drawdown. Maximal depth of occurrence decreased by 2-44 m for at least for 50 species of benthic macroinvertebrates between 1982 and 2004 compared to 1937-1961. Species richness of benthic macroinvertebrates declined from 25 to three species at depths where seasonal anoxia occurred. Total biomass increased by a factor of 10 from the period 1928-1948 to 1976-1979 then declined by a factor of 3 to 4 between 1987 and 2004. Energy flow through detritivores was more than tripled during 1976-2004 compared to 1928-1971, a result of increased plankton primary production. In contrast, energy flow through herbivorous benthic macroinvertebrates decreased by a factor of nearly 5, due to reduced areal coverage of macrophytes. Energy flow through filter feeders did not change over the time period examined, but energy flow through the entire zoobenthos community was nearly tripled. The biomasses of Oligochaeta, Chironomidae, and total zoobenthos showed a delayed response to changes in primary production of 7-9, 2, and 2-4 years, respectively. These patterns may provide a basis to predict results of restoration efforts based on the abundance of the zoobenthos in future years as the level of the lake is restored and water quality improves.
塞凡湖（亚美尼亚）的水位在 1949 年至 1997 年间人为降低了近 20 米。水位下降加上富营养化加剧，导致 1976 年至 2004 年期间，每年深湖底层都会出现季节性缺氧（持续 1-4 个月）。此外，水位下降后，大型植物区系和某些基质类型的范围严重缩小。与 1937 年至 1961 年相比，至少有 50 种底栖无脊椎动物的最大出现深度在 1982 年至 2004 年间下降了 2-44 米。在出现季节性缺氧的深度，底栖无脊椎动物的物种丰富度从 25 种下降到 3 种。1928 年至 1948 年期间，底栖碎屑动物的总生物量增加了 10 倍，而 1987 年至 2004 年期间则下降了 3 至 4 倍。与 1928 年至 1971 年相比，1976 年至 2004 年期间通过碎屑动物的能量流增加了两倍多，这是浮游植物初级生产力增加的结果。相比之下，由于大型植物的面积覆盖率降低，食草底栖无脊椎动物的能量流减少了近 5 倍。在研究期间，滤食动物的能量流没有变化，但整个底栖动物群落的能量流增加了近两倍。寡毛类、摇蚊科和总底栖动物的生物量对初级生产力变化的响应分别延迟了 7-9、2 和 2-4 年。这些模式可以为基于未来几年底栖动物的丰度预测恢复工作的结果提供依据，因为随着湖泊水位的恢复和水质的改善，底栖动物的丰度可能会增加。
