ABSTRACTthe annual variability of the photosynthetic production (PP) by phytoplankton in the lacustrine zone of the Jurumirim reservoir (São Paulo, Brazil) was evaluated in a three-year study to identify recurrent patterns and their causes. Variability in PP was measured daily during two periods of the year (the dry and rainy seasons). An analysis of the PP data failed to identify a recurrent pattern, since the PP values showed no correlation with hydrological factors (rainfall, water level and discharge, and washout) nor, apparently, with the water's nutritional conditions. A principal component analysis revealed that the PP and assimilation ratio were higher when the Po 4 3-and n-nh 4 + contents were low and the z eu /z miX ratios were at their highest. Areal primary productivity can be predicted based on the ratio between the maximum volumetric productivity and the coefficient of vertical extinction of light. however, the biomass integrated for z eu was a poor predictor of areal primary productivity. no correlation was found between water temperature and areal and maximum volumetric productivity. thus, the three-year PP study indicated that the variability pattern is typically chaotic. As for the short-term measurements, the PP was found to be higher in the dry season than in the rainy, although both seasons showed an areal PP variability of 35 to 40%. this pattern was attributed to the daily variation in the nutritional conditions and the magnitude of light penetrating through the water, combined with the mixing of phytoplanktonic cells. A comment about the relationship between primary production by phytoplankton and fish yield is also briefly discussed here.Keywords: primary productivity, phytoplankton, variability, reservoir, light, nutrients. RESUMOVariabilidade anual e de curto prazo na produtividade primária pelo fitoplâncton e fatores abióticos correlatos na Represa de Jurumirim (São Paulo, Brasil)A variabilidade anual da produção fotossintética (PP) pelo fitoplâncton na zona da barragem da represa de Jurumirim (São Paulo, Brasil) foi medida após um estudo no período de três anos sucessivos, com o objetivo de identificar padrões recorrentes e suas causas. medidas da variabilidade da PP em escala diária foram obtidas em dois períodos do ano (estações seca e chuvosa). nenhum padrão recorrente foi verificado nos dados de PP, visto não haver relação de sua variabilidade com nenhum fator hidrológico (precipitação, nível e vazão de água e washout) nem, aparentemente, com as condições nutritivas da água. A análise de componentes principais revelou que a PP e a taxa de assimilação foram mais elevadas na época do ano em que o conteúdo de Po 4 3-e n-nh 4 + foi mais baixo e quando as razões z eu /z miX foram mais elevadas. A produtividade primária/área pode ser estimada pela razão entre a produtividade volumétrica máxima e o coeficiente de extinção vertical da luz. entretanto, a biomassa integrada na z eu foi um pobre preditor da produtividade primária/área. nenhuma correlação foi encontrada entre a temperatura d...

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Reservoirs located in urban areas suffer specific pressures related to human activities. Their monitoring, management, and protection requirements differ from reservoirs situated in non-urbanized areas. The objectives of this study were: (a) to determine the concentrations of select pesticides and emerging pollutants (EPs) present in an urban reservoir; (b) to describe their possible spatial distributions; and (c) to quantify the risks for aquatic life and safeguard drinking water supplies. For this purpose, the Guarapiranga reservoir was studied as an example of a multi-stressed urban reservoir in a tropical region. A total of 31 organic compounds (including pesticides, illicit drugs, pharmaceuticals, and endocrine disruptors) were analyzed twice over a period of one year, together with classical indicators of water quality. The physical and chemical data were treated using principal component analysis (PCA) to identify possible temporal or spatial patterns. Risk assessment was performed for biota and drinking water use, comparing maximum environmental concentrations (MECs) with the predicted no-effect concentrations (PNECs) or drinking water quality criteria (DWC), respectively. The results demonstrated the presence of pesticides and EPs, as well as pollution by high levels of nutrients and Chlorophyll a (Chl. a), during the study period. The nutrients and Trophic State Index (TSI) showed gradients in the reservoir and regional distributions, while the pesticides and EPs only clearly showed this pattern in the dry season. The concentrations and distributions of the pesticides and EPs therefore showed seasonality. These findings suggested that the two groups of pollutants (EPs+pesticides and nutrients) possessed different sources and behavior and were not always correlated in the reservoir studied. In the studied period, no risk was observed in raw water for drinking water use, but carbendazim, imidacloprid, and BPA showed risks for the biota in the reservoir.

Water quality in reservoirs is often compromised in many regions worldwide by nutrients and trace metals. This demands continuous monitoring; however, analyses of large data sets collected during regular monitoring remain a difficult task. Multivariate techniques offer a fast and robust approach for interpreting complex results. The objective of this study was to check the efficacy of selforganizing maps (SOMs) as a tool to investigate biogeochemical processes. This tool can also help to illustrate influences of land use patterns on the water quality of reservoirs. Here we use the Itupararanga Reservoir in Brazil as a subtropical example. Vertical profiles were sampled from seven sites in the reservoir in a total of seven campaigns over 24 months. Next to physicochemical parameters in the water column (dissolved oxygen, Eh, pH, and temperature), levels of nutrients (NO 3 − , NH 4 + , and PO 4 3− ), transition and trace metals (Al, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn), and chlorophyll-a (Chla) were measured. These variables were correlated with land use using SOM. With this technique samples were classified into 17 distinct groups that showed distinct influences of spatial heterogeneity and seasonality. The analyses helped to reveal a seasonal stratification period, where Fe, Mn, and P were released from sediments. Nutrients and some metal inputs (Al and Fe) were related to agricultural, urban, and grass/pasture areas around the reservoir. Our approach also helped to explain physical and biogeochemical seasonality in the reservoir.

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.

The analysis of heavy metals in sediments, associated with geochronology, can identify the historical accumulation of these contaminants that occurred over time as a result of anthropogenic activities. A study was conducted at Paiva Castro Reservoir, a tropical reservoir in Brazil, to (1) establish baseline values for the metals Cd, Cr, Cu, Ni, Pb, Zn, Mn, Al and Fe; (2) investigate the history of heavy metal accumulation through geochronology using 210 Pb; and (3) identify the main variables that differentiate the sampled regions. A gravity corer was released twice in three reservoir areas. Each core was sliced at intervals of 2 cm and stored in a sealed plastic bag. One core was used for the determination of metals and for dating using the 210 Pb technique. The other core was used for the determination of organic matter and particle size. The baseline values for heavy metals were calculated according to the mean bottommost samples of the three core analysed. In terms of the levels of heavy metals, the greatest impacts in the region occurred during periods prior to the period of reservoir operation. In surface sediments, Cu exceeded several times (97.0 mg kg-1) the background (24.0 mg kg-1). This result may be a consequence of the application of copper sulphate for controlling algal blooms. A canonical discriminant analysis indicated that the variables that significantly differentiated the three sampled areas were related to the elements Al, Fe, and Mn and to particle size. These data indicate that the main differences are due to lithological variations and to the dynamic operation of reservoirs that provide a larger particle size fraction in the area where the uptake of water for the public water supply is located and in the area upstream from Paiva Castro, where there is higher flow energy. Evidence of the degradation of Paiva Castro Reservoir is already being reflected in the sediments. It is necessary that public policies are actually applied to counteract the degradation of this important ecosystem; otherwise, the reservoir's 'good quality' will be at risk.

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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.