Cleber Palma-Silva

Crescimento e fator de condição na fase juvenil de Farfantepenaeus brasiliensis (Latreille) e F. paulensis (Pérez-Farfante) (Crustacea, Decapoda, Penaeidae) em uma lagoa costeira tropical do Rio de Janeiro, Brasil

The growth relations of the shrimps Farfantepenaeus brasiliensis (Latreille, 1817) and F. paulensis (Perez-Farfante, 1967) were evaluated at Imboassica lagoon, Macae, Rio de Janeiro State, between June 1995 and September 1997, in four periods after events of sandbar opening. This sandbar separated the lagoon from the Atlantic Ocean. Through the evaluation of the weight/length relationships for the two species, significant differences in each interval after the sandbar openings were observed, as much among males and females as among all individuals of the same species. The results indicated that both species presented negative allometric growth in most of the studied occasions. The frequency and abundance of the two species in the lagoon is linked to many factors, among them the season of the sandbar opening, the span of time in which the sandbar remains opened, and the presence of a reproductive stock of adults close to the area when the sandbar is open. Through the analysis of the relative condition factor (Kr), it was verified that usually the conditions inside the lagoon are favorable to the development of both species, with the exception of the occasions when the sandbar opening events happen quickly and close to each other, allowing to conclude that the sandbar openings have an influence on the growth rates and in the general status of the organisms.

Macrófitas aquáticas como indicadores da qualidade da água em pequenos lagos rasos subtropicais, Sul do Brasil

Abstract: Aims: We evaluated the potential of aquatic macrophyte communities as bioindicators in six small shallow lakes. Methods: The sampling was conducted monthly for one year, during which all macrophytes were surveyed, and the water temperature, dissolved oxygen, pH, conductivity, total alkalinity, chlorophyll- a , suspended matter, total nitrogen (Nt) and total phosphorus (Pt) were measured. Results: In total, forty-three species were recorded, and there were significant differences in the species richness and limnological conditions among the lakes studied. A canonical correspondence analysis showed that the concentration of nutrients (Nt and Pt), chlorophyll- a , suspended matter, dissolved oxygen and pH were the most important predictors of the distribution of macrophytes. Some emergents were related to the high concentration of nutrients, chlorophyll- a , and suspended matter. Moreover, the most submersed species were associated with environments with low nutrient concentrations and the lowest values chlorophyll-

Field evidence of the influence of aquatic macrophytes on water quality in a shallow eutrophic lake over a 13-year period

AIM: The main objective of this work is to describe the changes in water characteristics of a shallow subtropical lake, in periods with and without growing of macrophytes, related to periods of clear-macrophyte dominance and turbid-phytoplankton dominance states. METHODS: The study was conducted in Biguas Lake, in the south coastal plain of Brazil (32° 04 43 S and 52° 10 03 W). Samplings were carried out monthly between October 2000 and November 2013. The limnological variables measured in the water column were dissolved oxygen (DO), water temperature, pH, electrical conductivity (EC), chlorophyll-a, total nitrogen (TN), total phosphorous (TP) and suspended material (SM). Data were grouped according to periods with macrophyte growth dominance (MD) and without macrophytes, with phytoplankton dominance (PD), and applied t- tests among TP, TN, Chlorophyll-a and SM. During macrophyte growth we estimated the coverage (%) and biomass variation of plants. RESULTS: Over the 13 years, the lake was well oxygenated, alkaline, and with a temperature variation according to subtropical seasonality. The lower values of all of the limnological variables were verified during periods of macrophyte growth, characterizing periods of clear and turbid waters. CONCLUSIONS: The influence of aquatic macrophytes in improving water quality in this shallow lake during the studied period, reducing nutrient concentrations, chlorophyll-a and suspended material in water, favoring the maintenance of a clear water state, was verified.

Water quality in the lotic area of the Antas river before and after the construction of the Monte Claro hydroelectric plant, south Brazil

AIM: This study characterized the water quality of the lotic areas of the Rio das Antas (Antas River)influenced by the construction of the Monte Claro hydroelectric plant (South Brazil), a run-of-the-river reservoir. METHODS: To assess the water quality, we selected four sampling points based on the results obtained in the water-quality monitoring program performed by CERAN (the Rio das Antas Energetic Company) in the pre-filling (2002-2004) and post-filling (2005-2008) periods. The river flow was monitored during both of the periods. Seasonal samplings were conducted, and alkalinity, chlorophyll a, total and fecal coliforms, conductivity, color, BOD, COD, total phosphorus, nitrate, nitrite, ammoniacal nitrogen, dissolved oxygen, pH, total dissolved solids, suspended solids, sulfates, temperature and turbidity were evaluated. The results were interpreted according to the Brazilian Environmental Councils Water Quality Index, Trophic State Index and CONAMA Resolution 357/05. To verify the occurrence of alterations before and after the plant operation, t-tests were performed. RESULTS: Significant changes in water quality were not observed after the impoundment. The permanence of the characteristics of the natural hydrography was important for maintaining the water quality. The decline of the water quality in a stretch with reduced flow was caused by Burati stream, a tributary containing high concentrations of nutrients and fecal coliforms. CONCLUSIONS:The Monte Claro hydroelectric plant did not alter the water quality of the Antas River. The small reservoir resulting from the plant project favors the maintenance of the water quality of the river and does not favor eutrophication. Attention should be given to Burati stream, a tributary of the Antas River, regarding its high nutrient and coliform content.

Temporal variation in the biomass and nutrient status of Azolla filiculoides Lam. (Salviniaceae) in a small shallow dystrophic lake

AIM: This study determined the temporal variation of the biomass and the concentrations of carbon, nitrogen and phosphorus in Azolla filiculoides Lam. in a small (0.5 ha) shallow dystrophic lake located in the city of Rio Grande (Rio Grande do Sul State, Brazil). METHOD: Sampling was conducted monthly between November 2000 and October 2001. The macrophytes were collected randomly in three replicates with a circular collector 0.3 m in diameter and subsequently washed with tap water and oven-dried at 60 oC for determination of the dry weight and the nutrient status (i.e., carbon, nitrogen and phosphorus). Primary productivity was estimated by the variation in biomass among successive samples. RESULTS: A. filiculoides was present in the lake throughout the year and occupied between 50 and 80% of the surface area. The biomass values ranged from 34.2 g DW.m-2, recorded in May (autumn), to 170.9 g DW.m-2 in January (summer). The highest rate of primary productivity was 3.3 g DW.m-2.d-1, observed in June. The concentrations of carbon, nitrogen and phosphorus in the plant ranged between 403 and 551 g.kg-1, 13.4 and 25.7 g.kg-1 and 0.5 and 1.9 g.kg-1, respectively. The water N:P ratio ranged between 19:1 and 368:1. CONCLUSION: The coverage of the surface of the lake by A. filiculoides throughout the study period and the nutritional status of the plant demonstrate the importance of the cycling of nutrients by macrophytes in this aquatic environment. The higher N:P ratio in the water column, compared with other neighboring environments without macrophytes, shows that the enrichment of the lake may result from the biological N-fixation activity produced by A. filiculoides.

Temporal variation of phytophilous Chironomidae over a 11-year period in a shallow Neotropical lake in southern Brazil

Small and shallow lakes make up most of the lake-covered area in the world, and immature Chironomidae generally constitute the dominant group among invertebrates in these systems, exhibiting a wide distribution and tolerance to various levels of water quality. The changes in trophic features associated with the dominance of different major primary producers (macrophyte and phytoplankton) are reflected in the functioning of these ecosystems and likely in their phytophilous Chironomidae species richness and abundance. These were thus studied in a Brazilian shallow lake over a 11-year period characterized by both clear and turbid water conditions in relation to water quality and dominant macrophytes. The results revealed differences in Chironomidae composition but not in richness associated with clear and turbid waters. The Goeldichironomus genera predominated during all years and for different macrophyte types (freefloating, floating leaf, and submerged). We attribute the variability of Chironomidae assemblages to changes in macrophyte dominance and water trophic status, such as the concentration of nutrients and chlorophyll-a, during the 11-year period. Submerged macrophytes were associated with clear waters and harbored the highest diversity, which emphasized the importance of these environmental conditions for preserving the biodiversity of Chironomidae in shallow lakes.

Aquatic macrophytes of six subtropical shallow lakes, Rio Grande, Rio Grande do Sul, Brazil

The aim of this study was to document the richness of aquatic macrophytes in six shallow lakes at Federal University of Rio Grande - FURG, Rio Grande, Rio Grande do Sul, Brazil. Qualitative surveys were carried out during 2008. Specimens were deposited at the university herbarium (HURG). We recorded 44 species belonging to 35 genera and 21 families. The majority of species were present all year. The family with highest diversity was Cyperaceae (eight species). Other studies have reported approximately 170 species for wetlands in the south of Brazil. This study documented approximately 25% of these species. The flora of the area should be preserved and monitored.

Potential Carbon Gas Production in Southern Brazil Wetland Sediments: Possible Implications of Agricultural Land Use and Warming

Methane (CH4) and carbon dioxide (CO2) are greenhouse gases (GHG) important in the carbon cycle that exchanges carbon between ecosystems and the atmosphere. To determine how rice paddy fields and temperature affect the carbon budget, we experimentally estimated CH4 and CO2 concentrations and production in sediments from natural and rice wetlands over a temperature gradient. Moreover, we estimated how much GHG production rates would increase in these ecosystems, according to the IPCC projections for temperature rise caused by global warming. Our results showed that the concentrations and potential production rates of GHG showed no significant differences between natural and rice wetlands, although the accumulation of organic matter and nutrients was higher in natural wetland sediments. However, temperature elevation played a significant role in the rise of gas production rates. According to our results, projected increased atmospheric temperature may promote increases in the rates of production and concentrations of carbon gases. The potential carbon gases production in the scenario of atmospheric warming indicated that CH4 (18.91%) may be higher than CO2 (4.54%), mainly in rice wetlands. This reinforces the importance of natural wetland conservation.

Water quality of the São Gonçalo channel, urban and agricultural water supply in southern Brazil

O canal Sao Goncalo liga as lagoas dos Patos e Mirim, no sul do Brasil, possuindo um comprimento de cerca de 70 Km. E importante manancial agricola para a cultura do arroz irrigado, e urbano, para o municipio de Rio Grande, com cerca de 250 mil habitantes. Este trabalho visou obter um diagnostico da qualidade das aguas deste manancial, utilizando metricas da comunidade de invertebrados bentonicos (indice de Shannon-Wiener, abundância e riqueza de taxons), e o indice biotico BMWP, avaliacao de caracteristicas fisicas e quimicas, e aplicacao do indice de estado trofico. O indice BMWP geral para o periodo indicou aguas contaminadas ou poluidas, com maiores valores de riqueza e densidade de grupos indicadores de condicoes alteradas (Sarcodina e Hydracarina). As variaveis analisadas indicam aguas eutrofizadas, com valores de clorofila-a caracteristicos de ambientes eutroficos (> 2,9 µg. L-1), baixas taxas N:P tanto na agua como no sedimento, indicando limitacao por nitrogenio na maioria dos periodos. Estes valores sao corroborados pelos escores de indices de estado trofico, que em sua maioria indicaram condicoes de mesotrofia e eutrofia, atingindo periodos de hipertrofia. Os valores de IET mais elevados ocorreram a jusante do rio Piratini, nas coletas de abril/2009 e fevereiro/2011, atingindo valores de super e hipereutrofico, respectivamente, em periodos coincidentes com drenagem das culturas de arroz irrigado no entorno. Os resultados encontrados relativos as concentracoes de nutrientes, estequiometria de nitrogenio e fosforo e indice biotico reforcam a necessidade de avaliacoes de usos do entorno deste manancial.