Phytoplankton, Trophic State and Ecological Potential in reservoirs in the State of São Paulo, Brazil

Abstract This study evaluated the ecological potential of reservoirs in the Brazilian state of São Paulo, having phytoplankton as a biological quality element. Integrated water column sampling was carried out in the dam, and in the intermediate and fluvial zones of the Igaratá, Atibainha, Paiva Castro, Rio Grande, Itupararanga, Broa, Barra Bonita, Guarapiranga and Salto Grande reservoirs in July 2015. Physico-chemical and biological parameters were analyzed in all environments. The phytoplankton was analyzed under an inverted microscope, and measurements of density, diversity, equitability and dominance were determined. The data was ordered using PCA and CCA analysis. The ecological potential of the reservoirs was determined through the evenness index. The electrical conductivity, nitrate, nitrite and orthophosphate were higher in the more eutrophic reservoirs: Salto Grande, Barra Bonita, Guarapiranga and Rio Grande. A trophic gradient was observed among the sampling points, suggesting a conservation spectrum. There was dominance of cyanobacteria in the eutrophic reservoirs associated with low diversity and high dominance. The total density was correlated with TP, TN, and pH. A divergent relationship between the trophic state index and the evenness index was observed. The Atibainha, Itupararanga, Broa, Barra Bonita and Salto Grande reservoirs were classified as water bodies of very poor ecological quality (Bad). The evenness index seems to be a good alternative to the biomonitoring of the studied reservoirs.

摘要 本研究以浮游植物作为生物质量评价指标，评估了巴西圣保罗州各水库的生态潜力。2015年7月，对伊加拉塔（Igaratá）、阿蒂拜尼亚（Atibainha）、帕瓦·卡斯特罗（Paiva Castro）、里奥格兰德（Rio Grande）、伊图帕拉兰卡（Itupararanga）、布罗阿（Broa）、巴拉博尼塔（Barra Bonita）、瓜皮兰加（Guarapiranga）以及萨尔托格兰德（Salto Grande）共9座水库的坝区、过渡带及河流带开展了水体柱体综合采样。所有采样环境均测定了理化参数与生物学参数。采用倒置显微镜对浮游植物进行分析，并测定其密度、多样性、均匀度与优势度。采用主成分分析（PCA）与典范对应分析（CCA）对数据进行排序分析。通过均匀度指数确定各水库的生态潜力。富营养化程度更高的萨尔托格兰德、巴拉博尼塔、瓜皮兰加与里奥格兰德水库，其电导率、硝酸盐、亚硝酸盐及正磷酸盐浓度均更高。采样点间呈现出营养梯度，暗示存在保护光谱。富营养化水库中蓝藻占据优势，且伴随多样性偏低、优势度偏高的特征。浮游植物总密度与总磷（TP）、总氮（TN）及pH值呈显著相关。研究发现营养状态指数与均匀度指数间存在相悖的关联关系。阿蒂拜尼亚、伊图帕拉兰卡、布罗阿、巴拉博尼塔及萨尔托格兰德水库被归类为生态质量极差（劣）的水体。均匀度指数或可作为本次研究涉及水库的生物监测的优良替代指标。