Maria do Carmo Calijuri

Limiting factors for phytoplankton growth in subtropical reservoirs: the effect of light and nutrient availability in different longitudinal compartments

Abstract Limited information is available on the interactions between environmental factors and algal growth in tropical and subtropical aquatic systems. We investigated the relationships between algal biomass (measured as chlorophyll, Chl-a) and light, total phosphorus (TP) and total nitrogen (TN) in longitudinal zones of subtropical reservoirs. We studied the seasonal variation of water variables in Itupararanga Reservoir (Brazil) and compared the results with 16 other subtropical lakes and reservoirs. The longitudinal zones in Itupararanga Reservoir were considered statistically different (p < 0.05, MANOVA). From the riverine zone to the dam region of the reservoir, Spearman Correlation Test suggested that light limitation and TP limitation tended to decrease and increase, respectively. Although nitrate concentrations were high (>400 μg/L), the Spearman coefficients between Chl-a and TN and the TN:TP ratios (11:1 < TN:TP < 35:1) indicated that nitrogen may be co-limiting algal growth in the studied water body. Putting Itupararanga in a regional context allowed assessment of potential influences of land use on trophic state. Within the subtropical dataset, TP explained a greater percentage of variance in Chl-a (R2 = 0.70) than TN (R2 = 0.17). The main land use type within the reservoirs drainage area significantly influenced the concentrations of TP, TN, and Chl-a (p < 0.05, MANOVA), with different relationships between nutrients and chlorophyll in forested (R2 = 0.12–0.33), agricultural (R2 = 0.50–0.68) and urban (R2 = 0.09–0.64) watersheds. Comparisons with literature values and those from reservoirs with less altered watersheds indicated that Itupararanga Reservoir is reaching the mesotrophic–eutrophic boundary, and further nutrient enrichment could cause water quality degradation.

Algal biomass production and wastewater treatment in high rate algal ponds receiving disinfected effluent

Algal biomass production associated with wastewater is usually carried out in high rate algal ponds (HRAPs), which are concomitantly used in the treatment of such effluent. However, most types of wastewater have high levels of bacteria that can inhibit the growth of algal biomass by competing for space and nutrients. The objective of this study was to assess the influence of ultraviolet (UV) pre-disinfection on the performance of HRAPs used for wastewater treatment and algal biomass production. Two HRAPs were tested: one received effluent from an upflow anaerobic sludge blanket (UASB) reactor – HRAP – and the second received UASB effluent pre-disinfected by UV radiation – UVHRAP. Physical, chemical and microbiological parameters were monitored, as well as algal biomass productivity and daily pH and dissolved oxygen (DO) variation. The UVHRAP presented highest DO and pH values, as well as greater percentage of chlorophyll a in the biomass, which indicates greater algal biomass productivity. The average percentages of chlorophyll a found in the biomass obtained from the HRAP and the UVHRAP were 0.95±0.65% and 1.58±0.65%, respectively. However, total biomass productivity was greater in the HRAP (11.4 gVSS m−2 day−1) compared with the UVHRAP (9.3 gVSS m−2 day−1). Mean pH values were 7.7±0.7 in the HRAP and 8.1±1.0 in the UVHRAP, and mean values of DO percent saturation were 87±26% and 112±31% for the HRAP and the UVHRAP, respectively. Despite these differences, removal efficiencies of organic carbon, chemical oxygen demand, ammoniacal nitrogen and soluble phosphorus were statistically equal at the 5% significance level.

Seasonal variation of phytoplankton functional groups in the arms of a tropical reservoir with multiple uses (SP, Brazil)

The assessment of phytoplankton functional groups may help water resource management, considering the multiple uses of this resource type. This research investigated the seasonal variation of these groups in the Itupararanga Reservoir (SP, Brazil). Four arms of the reservoir were sampled to determine the water temperature, pH, underwater Photosynthetically Active Radiation (PAR), turbidity, total phosphorus, nitrate and total suspended solids (TSS), besides qualitative and quantitative aspects of the phytoplankton community and meteorological data. The study was carried out in August and October 2009, and in February 2010, and suggested there is seasonal variation of phytoplankton groups (p* 1000 µE m-2 s-1) were relevant in the summer. Considering the environmental variability of the arms of the reservoir (derived from the influence of tributaries), and the dominance of phytoplankton groups typical of eutrophic environments, we recommend continuous monitoring of this area so that different water uses can continue, particularly for supply and recreation.

Biogeochemical processes and the diversity of Nhecolândia lakes, Brazil

The Pantanal of Nhecolândia, the worlds largest and most diversified field of tropical lakes, comprises approximately 10,000 lakes, which cover an area of 24,000 km(2) and vary greatly in salinity, pH, alkalinity, colour, physiography and biological activity. The hyposaline lakes have variable pHs, low alkalinity, macrophytes and low phytoplankton densities. The saline lakes have pHs above 9 or 10, high alkalinity, a high density of phytoplankton and sand beaches. The cause of the diversity of these lakes has been an open question, which we have addressed in our research. Here we propose a hybrid process, both geochemical and biological, as the main cause, including (1) a climate with an important water deficit and poverty in Ca(2+) in both superficial and phreatic waters; and (2) an elevation of pH during cyanobacteria blooms. These two aspects destabilise the general tendency of Earths surface waters towards a neutral pH. This imbalance results in an increase in the pH and dissolution of previously precipitated amorphous silica and quartzose sand. During extreme droughts, amorphous silica precipitates in the inter-granular spaces of the lake bottom sediment, increasing the isolation of the lake from the phreatic level. This paper discusses this biogeochemical problem in the light of physicochemical, chemical, altimetric and phytoplankton data.

Dinâmica de nitrogênio em um sistema de lagoas de estabilização na região do Vale do Ribeira (São Paulo - Brasil)

This research had as main objective to investigate the involved processes in the transformations of nitrogen in a system of waste stabilization ponds. In nictemeral sampling (24 hours) strong thermal stratification was observed during most of the showed cycle which conditioned two vertical compartments and the chemical stratification in the two lagoons, making possible the analysis of the processes of segmented form for PCA (Principal Components Analysis) that was a very useful statistics tool in the characterization of the processes. The protein degradation was observed with subsequent generation and accumulation of ammoniacal nitrogen, beyond the possible excretion of protein or amino acids for phytoplanktonic organisms in the surface of the ponds. The probable occurrence of nitrification in the surface layer of the anaerobic pond evidenced the necessity of improving the operation parameters of the system in order to reach a greater nitrogen removal through the denitrification, process probably inhibited by significant high concentrations of oxygen dissolved registered in superficial layers, particularly during the day.

Nutrient reference concentrations and trophic state boundaries in subtropical reservoirs.

Nutrient criteria as reference concentrations and trophic state boundaries are necessary for water management worldwide because anthropogenic eutrophication is a threat to the water uses. We compiled data on total phosphorus (TP), nitrogen (TN) and chlorophyll a (Chl a) from 17 subtropical reservoirs monitored from 2005-2009 in the São Paulo State (Brazil) to calculate reference concentrations through the trisection method (United States Environmental Protection Agency). By dividing our dataset into thirds we presented trophic state boundaries and frequency curves for the nutrient levels in water bodies with different enrichment conditions. TP and TN baseline concentrations (0.010 mg/L and 0.350 mg/L, respectively) were bracketed by ranges for temperate reservoirs available in the literature. We propose trophic state boundaries (upper limits for the oligotrophic category: 0.010 mg TP/L, 0.460 mg TN/L and 1.7 μg Chl a/L; for the mesotrophic: 0.030 mg TP/L, 0.820 mg TN/L and 9.0 μg Chl a/L). Through an example with a different dataset (from the Itupararanga Reservoir, Brazil), we encouraged the use of frequency curves to compare data from individual monitoring efforts with the expected concentrations in oligotrophic, mesotrophic and eutrophic regional systems. Such analysis might help designing recovery programs to reach targeted concentrations and mitigate the undesirable eutrophication symptoms in subtropical freshwaters.

Relationship between space distribution of the benthic macroinvertebrates community and trophic state in a Neotropical reservoir (Itupararanga, Brazil)

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. Sediments 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.

Análise probabilística de ocorrência de incompatibilidade da qualidade da água com o enquadramento legal de sistemas aquáticos - estudo de caso do rio Pariquera-Açu (SP)

Embora relativamente comuns no Brasil, programas de monitoramento da qualidade da agua frequentemente nao transformam os resultados em elementos que norteiem o poder publico para a recuperacao dos sistemas aquaticos. Assim, a presente pesquisa teve por objetivo discutir a utilizacao das curvas probabilisticas de incompatibilidade da qualidade da agua com o enquadramento legal dos corpos de agua como ferramenta complementar ao monitoramento. As probabilidades de inconformidade com a resolucao CONAMA 357/05 (Classe 2) para o rio Pariquera-Acu (SP) em 2007 foram de 35, 8, 44, 1, 0, 0 e 0%, respectivamente para oxigenio dissolvido, turbidez, fosforo, nitrogenio amoniacal, nitrito, nitrato e clorofila-a. Concluiu-se que o grau de condensacao de informacoes gerado pelas curvas probabilisticas representa uma contribuicao para a gestao da qualidade de agua.

Resolução CONAMA 357/2005: análise espacial e temporal de não conformidades em rios e reservatórios do estado de São Paulo de acordo com seus enquadramentos (2005-2009)

The CONAMA Framework Resolution 357/2005 fixed the conditions for establishing water quality categories in Brazilian aquatic systems. We assessed the levels of non-conformity among the water quality in rivers and reservoirs from Sao Paulo State (SP, Brazil) and their framework. We analyzed data (n=43,897) from total phosphorus, dissolved oxygen, nitrate, turbidity and Biochemical Oxygen Demand of 360 sampling sites within the 22 UGRHI (Water Resources Management Units) in SP from 2005 to 2009. The situation was unsatisfactory for total phosphorus and dissolved oxygen, mainly in the industrial UGRHI. There was no significant water quality improvement in relation to some of the studied variables within these five years, which indicates the need for directing investments on tertiary domestic wastewater treatment and mitigation of non-point pollution loads.

Field investigations of the 2013–14 drought through quali-quantitative freshwater monitoring at the headwaters of the Cantareira System, Brazil

ABSTRACT Integrating seasonal patterns of water availability and land-use/land-cover change is crucial in watershed planning. Often, these are not considered under hydrological extremes affecting decision making. This article presents results from a multi-site, nested catchment experiment carried out during a dry period in the Cantareira Water Supply System, South-East Brazil, linking quali-quantitative freshwater monitoring to land-use/land-cover change. Results from 17 catchments show regional behaviour for nitrate loads and drainage areas (0.66–925 km2). An inverse correlation between forest cover and water yield was observed. Despite forest growth in spatial extent, nutrient loads showed potential hazards for water security.