ACUTE TOXICITY of SODIUM SELENITE and SODIUM SELENATE TO TILAPIA, Oreochromis niloticus, FINGERLINGS

Selenium is an essential nutrient for many organisms, including fish. It can be released in the water by natural processes of dissolving rocks and minerals, and by the wastewater from industries and agricultural activities, which can increase its concentration in the environment, leading to toxic effects to the aquatic biota. Median Lethal Concentrations (LC(50-96h)) of two forms of selenium were estimated to fingerlings of Nile tilapia Oreochromis niloticus, focusing on estimating indicators for future environmental risk assessments in aquatic ecosystems contaminated with those elements, particularly for evaluate sources of water quality suitable for rearing tilapia. The results were: LC(50-96h) of sodium selenite (Na(2)SeO(3)) = 4.42 mg Se(4+) L(-1), and LC(50-96h) of sodium selenate (Na(2)SeO(4)) = 14,67 mg Se(6+) L(-1). According to those data, it was possible to classify sodium selenite as highly toxic and sodium selenate as moderately toxic to fingerlings of tilapia.

Acute and chronic toxicity of sediment samples from Guanabara Bay (RJ) during the rainy period

A Baía de Guanabara é um ambiente marinho-estuarino de grande relevância ecológica e sócio-econômica, e sujeita a uma ampla gama de impactos ambientais. O sedimento é o principal destino para a maioria das substâncias introduzidas nos corpos d'água, podendo fornecer uma medida integrada da qualidade ambiental, a qual pode ser avaliada por várias abordagens. Neste projeto, a qualidade de sedimentos da Baía de Guanabara foi por uma abordagem ecotoxicológica, por meio de testes de toxicidade aguda de sedimento integral, utilizando Tiburonella viscana, e testes de toxicidade crônica de água intersticial, elutriato e interface sedimento-água, utilizando embriões de Lytechinus variegatus. Os sedimentos foram coletados em 14 estações de amostragem. Nos testes crônicos houve efeitos significativos na maioria das amostras, enquanto os sedimentos coletados nas estações 1, 2, 3, 6, 8, 10, 11, 12 e 15 apresentaram também toxicidade aguda. Houve grande concordância entre os resultados dos diferentes testes, e sua integração mostrou que os sedimentos analisados encontram-se inadequados à vida aquática, indicando degradação ambiental na baía da Guanabara. Nesse contexto, o controle das fontes poluidoras e o gerenciamento dos múltiplos usos da baía devem ser implementados, no sentido da melhora da qualidade ambiental.

Sediment toxicity assessment of Guanabara Bay, Rio de Janeiro, Brazil.

Guanabara Bay (GB) comprises of estuarine and marine environments of high ecological and socio-economic relevance, together with port, industrial and urban areas. The anthropogenic activities produce environmental impacts, including the aquatic pollution. The sediment quality assessment is important to evaluate the effects of contamination, once sediments are a repository for most of the contaminants. In this Study, the quality of sediments from GB was evaluated, in rainy and dry periods, throughout the employment of acute toxicity tests with the amphipod Tiburonella viscana, and chronic bioassays with embryos of the sea-urchin Lytechinus variegatus. In the dry period, acute toxicity was found in the sediments from stations 1, 2 3 (NW) and 7 (near Guapimirim Environmental Protection Area). The bioassays with liquid phases showed effects, but were strongly influenced by the unionized ammonia levels, which were high in this period. In the rainy period, acute toxicity was found in sediments samples from stations 1, 2, 3, 6, 8, 10, 11, 12 and 15. Chronic toxicity could be clearly detected, as ammonia concentrations tended to be low in the most part of the samples. The results showed that the sediment toxicity is influenced by precipitation rates, which increase the input of contaminants to the Bay, and also allowed subdividing GB in three main zones: northwest (stations 1, 2, 3, 5), northeast (stations 6, 7, 8, 9) and centre-south (stations 10, 11, 12, 13, 14, 15). Results also showed that the quality of GB sediments is poor, and that toxicity tests could determine the combined effects of pollutants.

Acute lethal and sublethal effects of neem leaf extract on the neotropical freshwater fish Prochilodus lineatus

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 It LC(50) of neem leaf extract for juveniles P lineatus was estimated as 4.8 g L(-1); the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L(-1) or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L(-1) and 5.0 g L(-1) neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L(-1). Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species. (c) 2006 Elsevier B.V. All rights reserved.

Toxicity of the therapeutic potassium permanganate to tilapia Oreochromis niloticus and to non-target organisms Ceriodaphnia dubia (microcrustacean cladocera) and Pseudokirchneriella subcapitata (green microalgae)

Potassium permanganate is a chemical compound widely used in aquaculture for the control and removal of parasites, and in the prevention of diseases caused by bacteria and fungi. However, this compound can be toxic to fish, being a strong oxidant. Moreover, there is no consistent information in the literature about its toxicity to non-target organisms. The purpose of this study was to evaluate the acute toxicity (LC50;96h) of potassium permanganate for tilapia, Oreochromis niloticus, and to determine its toxic effects on nontarget organisms using ecotoxicological assays performed with the microcrustacean Ceriodaphnia dubia and with the green microalgae Pseudokirchneriella subcapitata. The results showed that the concentration of 1.81 mg L-1 of potassium permanganate caused acute toxic effect in tilapia fingerlings. The ecotoxicological assays demonstrated that concentrations above 0.12 mg L-1 can cause chronic toxic effects on non-target organisms, indicating possible deleterious effects on the food chain of the aquatic ecosystem that may receive the discharge of effluents released by fish cultures treated with this chemotherapy. All toxic concentrations determined in this study were below those recommended in the literature for the use of this chemotherapy in fish cultures, demonstrating that this type of therapy should be more carefully considered in order to avoid damage to the treated fish and to the environment. (C) 2011 Elsevier B.V. All rights reserved.

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Background, aim, and scope Contaminated sediments are a worldwide problem, and mobilization of contaminants is one of the most critical issues in environmental risk assessment insofar as dredging projects are concerned. The investigation of how toxic compounds are mobilized during dredging operations in the channel of the Port of Santos, Brazil, was conducted in an attempt to assess changes in the bioavailability and toxicity of these contaminants.Materials and methods Bulk sediment samples and their interstitial waters and elutriates were subjected to chemical evaluation and ecotoxicological assessment. Samples were collected from the channel before dredging, from the dredge's hopper, and from the disposal site and its surroundings.Results The results indicate that the bulk sediments from the dredging site are contaminated moderately with As, Pb, and Zn and severely with Hg, and that polycyclic aromatic hydrocarbon (PAH) concentrations are relatively high. Our results also show a 50% increase in PAH concentrations in suspended solids in the water collected from the hopper dredge. This finding is of great concern, since it refers to the dredge overflow water which is pumped back into the ecosystem. Acute toxicity tests on bulk sediment using the amphipod Tiburonella viscana showed no toxicity, while chronic tests with the sea urchin Lytechinus variegatus showed toxicity in the interstitial waters and elutriates. Results are compared with widely used sediment quality guidelines and with a sediment quality assessment scheme based on various lines of evidence.Conclusions The data presented here indicate that the sediments collected in this port show a certain degree of contamination, especially those from the inner part of the channel. The classification established in this study indicated that sediments from the dredged channel are impacted detrimentally and that sea disposal may disperse contaminants. According to this classification, the sediments are inappropriate for disposal at sea. It should be emphasized that the poor quality of fine sediments discharged from the hopper dredge in the overflow process can recontaminate the environment.Recommendations and perspectives These findings will help to underpin improved planning of management strategies for dredging operations and sediment disposal in Brazil and other countries.

Eficácia do diquat no controle de Hydrilla verticillata, Egeria densa e Egeria najas e toxicidade aguda para o Guaru (Phallocerus caudimaculatus), em condições de laboratório

No Brasil, as macrófitas aquáticas submersas, Egeria densa e Egeria najas, têm causado prejuízos aos usos múltiplos da água. Hydrilla verticillata foi recentemente introduzida, mas tem histórico como planta problemática nos EUA, no México e na Austrália. O objetivo deste trabalho foi avaliar as suscetibilidades relativas dessas três macrófitas aquáticas ao diquat e os riscos da utilização desse herbicida para o guaru (Phallocerus caudimaculatus). Para isso, foram instalados ensaios em condições de laboratório, a fim de avaliar a suscetibilidade relativa das três macrófitas por meio da manutenção de ponteiros dessas plantas em soluções contendo 0,0; 0,2; 0,4; 0,8; e 1,6 mg L-1 de diquat (Reward®) por 14 dias. A avaliação foi realizada pela variação do acúmulo de matéria fresca e do comprimento dos ponteiros no período de exposição ao herbicida. H. verticillata mostrou maior sensibilidade ao diquat em comparação com as duas macrófitas do gênero Egeria, mesmo em baixas concentrações do herbicida. Nas maiores concentrações, E. densa mostrou maior sensibilidade que E. najas. O risco da aplicação do diquat para P. caudimaculatus foi estimado pela toxicidade aguda. Alevinos de P. caudimaculatus de 0,4 ± 0,2 mg foram expostos a soluções de 0,0; 1,0; 5,0; 10,0; 15,0; 20,0; 25,0; e 30,0 mg L-1 de diquat. A concentração letal de 50% (CL(I) (50;96h)) do diquat estimada para P. caudimaculatus foi de 7,17 mg L-1. Para P. caudimaculatus, a toxicidade aguda foi superior à concentração recomendada para o controle de macrófitas aquáticas submersas, indicando risco muito baixo para esse peixe.