Jorcin A, Nogueira M G, Belmont R
Departamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brazil.
Braz J Biol. 2009 Feb;69(1):19-29. doi: 10.1590/s1519-69842009000100003.
This study is part of the limnological monitoring undertaken by the Energy Company of the State of São Paulo (CESP) during the filling up process of the Porto Primavera Reservoir (Hydroelectric Power Plant Engenheiro Sérgio Motta). This reservoir, located in the high Paraná River between the States of São Paulo and Mato Grosso do Sul, is the fourth largest in the country. The first filling up phase started in December 1998 and the second phase in March 2001. Samples for benthic community and sediment characteristics analysis were quarterly collected between August of 1999 and November 2001 and also in August of 2002 (11 sampling campaigns). Samplings were carried out at 13 stations distributed in the reservoir, and at one point located downstream of the dam. 128 invertebrate taxa were identified, being Mollusca, Annelida, Insecta and Nematoda the dominant groups during almost the whole study period. Insecta was the best represented class (9 different orders), and Diptera contributed with higher number of taxa, 63. The exotic species of bivalve Corbicula fluminea was recorded in all sampling stations showing its great capacity to colonize new habitats in the neotropical region. Noticeable variations in the fauna density were observed, considering both different periods and locations. The maximum density of organisms (mean value of 7812 ind.m-2) was recorded in the center of the reservoir, and the minimum (mean value 9 ind.m-2) in the more lacustrine area near the dam. The greatest species richness per sample (24 taxa) was observed in the reservoir upstream (fluvial zone). The maximum diversity (Shannon-Wiener Index) per station/period, 3.82 and 3.86 bits.ind-1, were calculated in the transitional river/reservoir zone during the beginning (August 1999) and in the reservoir central zones in the end (August 2002) of the filling up period, respectively. There was no clear relation between the distribution of the different faunistic groups and the sediment granulometric characteristics. However, the decrease or even total absence of organisms was observed at stations with high organic matter concentration (>40%) in a low degradation state (coarse detritus). This fact may be related to the lack of sediment deposits, which would cause difficulties to the fixation of the benthic fauna. Additionally, in those conditions more reduced chemical conditions are expected in function of the intense decomposition process of the flooded vegetation.
本研究是圣保罗州能源公司（CESP）在波多黎各普里马韦拉水库（塞尔吉奥·莫塔工程师水电站）蓄水过程中进行的湖泊学监测的一部分。该水库位于圣保罗州和南马托格罗索州之间的巴拉那河上游，是巴西第四大水库。首次蓄水阶段始于1998年12月，第二阶段始于2001年3月。1999年8月至2001年11月以及2002年8月（共11次采样活动）期间，每季度采集底栖生物群落和沉积物特征分析样本。采样在水库分布的13个站点以及大坝下游的一个点进行。共鉴定出128种无脊椎动物分类群，在几乎整个研究期间，软体动物、环节动物、昆虫和线虫是优势类群。昆虫纲是代表性最强的纲（9个不同目），双翅目贡献的分类单元数量最多，为63种。双壳类外来物种河蚬在所有采样站点均有记录，显示出其在新热带地区定殖新栖息地的强大能力。考虑到不同时期和地点，观察到动物密度存在显著差异。水库中心记录到生物体的最大密度（平均值为7812个/平方米），而在大坝附近更靠近湖泊的区域记录到最小密度（平均值为9个/平方米）。每个样本中物种丰富度最高（24个分类单元）的情况出现在水库上游（河流区域）。在蓄水期开始时（1999年8月）的过渡性河流/水库区域以及蓄水期末期（2002年8月）的水库中心区域，计算出每个站点/时期的最大多样性（香农-维纳指数）分别为3.82和3.86比特/个体。不同动物类群的分布与沉积物粒度特征之间没有明显关系。然而，在低降解状态（粗碎屑）下有机物浓度高（>40%）的站点，观察到生物体数量减少甚至完全没有。这一事实可能与缺乏沉积物堆积有关，沉积物堆积不足会给底栖动物固定带来困难。此外，在这些条件下，由于淹没植被的强烈分解过程，预计化学条件会更加还原。
