RESUMODentre as diversas atividades desenvolvidas no entorno de corpos de água, a poluição por agroquímicos e o lançamento de efluentes acarretam a carga excessiva de nutrientes que contribuem para o processo de eutrofização artificial e degradação destes ecossistemas. Neste contexto, os objetivos deste trabalho foram: determinar a heterogeneidade sazonal e espacial nas águas superficiais do reservatório Itupararanga e verificar a influência dos usos do entorno sobre a qualidade da água do reservatório localizado na cidade de Ibiúna, São Paulo, Brasil. Analisou-se o Índice de Estado Trófico (IET) e variáveis limnológicas em duas estações distintas -período seco e chuvoso de 2013. Os dados foram comparados com mapa de usos do solo e com parâmetros estabelecidos pela resolução CONAMA n° 357 de 2005. Os resultados demostraram que o fósforo total não esteve em conformidade com as especificações CONAMA. O reservatório apresentou heterogeneidade sazonal e espacial em relação ao IET e às variáveis limnológicas. Por meio da análise de agrupamento com os dados de qualidade de água e uso e ocupação dos solos foi comprovada a heterogeneidade espacial. A análise de agrupamento indicou que a cobertura florestal é um importante fator para a contenção da entrada de sólidos em suspensão. Indicou também que o uso agrícola é a principal fonte de nitrogênio para o meio enquanto que os rios formadores contribuem, principalmente com cargas de fósforo. Assim, por se tratar de uma área de importância social e econômica, medidas de preservação devem ser tomadas a fim de mitigar os avanços das atividades potencialmente impactantes.

Anthropic eutrophication is one of the most widespread problems affecting water quality worldwide. This condition is caused by excessive nutrient inputs to aquatic systems, and one of the main consequences is accelerated phytoplankton growth. Eutrophication can lead to damage to human health, the environment, society, and the economy. One of the most serious consequences of eutrophication is the proliferation of cyanobacteria that can release toxins into the water. The aim of this research was to evaluate the trophic condition of a tropical reservoir over the course of time, using a database extending over 15 years to investigate relationships with environmental conditions, considering spatial heterogeneity and seasonality, as well as inter-relations between trophic state indicators. Data for chlorophyll-a, total phosphorus, and total nitrogen were collected from 2000 to 2014, and cyanobacteria abundance was determined from 2004 to 2014. The trophic state index was also calculated. The results demonstrated the existence of two distinct compartments in the reservoir: one lotic and the other lentic. No relationship was observed between chlorophyll-a and phosphorus. The results suggested that phytoplankton growth was mainly controlled by nitrogen concentrations. These conditions favored cyanobacteria predominance, resulting in increasing abundance of these potentially toxic bacteria over time. The model obtained indicated hypereutrophic conditions, with high phytoplankton biomass and cyanobacteria abundance during the next years likely to affect the uses of the water of the reservoir.

The purpose of this work was to verify the benthic macroinvertebrates community responses through environmental factors along a headwater tropical reservoir. Samplings were taken with a Van-Veen grab along the reservoir in littoral and profundal regions and in the headwater, next to the dam and the middle of the reservoir. Samples were taken during both wet and dry seasons. Dissolved oxygen concentrations, electric conductivity, temperature and pH near the sediment have been performed in situ, at every sampling station by using a multiprobe and Secchi disc. Total water phosphorus and chlorophyll a concentrations were analyzed to determine the trophic state index. Sediment's organic matter, total phosphorus, nitrogen concentrations and granulometric composition were measured. In order to verify which environmental variables would have more influence over the benthic macroinvertebrates community, a canonical correspondence analysis (CCA) was performed. The total number of recorded taxa was 28. Among them, the family Chironomidae (Diptera) was the richest group (19 taxa). It can be proposed that the benthic macroinvertebrates community may be influenced by environmental conditions such as nutrient and organic matter availability, as well as dissolved oxygen concentration. Macroinvertebrates are adequate bioindicators of water quality due to their sensibility to environmental changes mentioned before. Chironomus sp, Limnodrilus hoffmeisteri and Branchiura sowerbyi comprises a group that can be considered bio-indicators of eutrophic conditions. A second group can be considered as indicator of mesotrophic conditions. The presence of two or more members from that group which comprises Tanytarsini spp, Fissimentum sp, Pelomus sp and Goeldichironomus sp, like predominant taxa, may indicates mesotrophic conditions.

The Jundiaí-Mirim watershed supplies the Jundiaí city and it is located between two metropolitan regions: the Campinas metropolitan region and the São Paulo metropolitan region which are the two most populous regions in São Paulo state. In this region some problems such as hydric resources scarcity, as well the water quality; conflicts between the water users and hydric pollution are part of the reality faced by the management agencies and government. The trophic state index (TSI) allows the water bodies classification according to the nutrients entrance into the system. That contribution artificially stimulates the algae and macrophytes proliferation and may causes a number of problems which includes: toxic algae proliferation, fish kills and disagreeable odor. The benthic macroinvertebrates are one of the most widely and recognized bioindicators in the aquatic environments reacting to impacts in water column, sediment and margins. The objective of the present research was to assess the environmental quality of the Jundiaí Mirim basin based on the trophic state index and the benthic macroinvertebrates community. Samplings were performed for TSI calculation and benthic macroinvertebrates rapid analysis at four samplings stations along the Jundiaí-Mirim river basin (Jundiaí, SP, Brazil). The data obtained reveals a worrying situation of the basin which is suffering a eutrophication process resulting in a poor quality of its waters and sediments. Moreover, it was recorded the presence of the exotic mollusk Corbicula fluminea, one of the freshwater exotic species of main concern in the world. It is recommended the development of an action project comprising short, average and long term marks in order to promote the recovery of the environment and to avoid environmental, social and economic problems. A rapid analysis index using the benthic macroinvertebrates was proposed.