Heavy metals, depending on their oxidation states, can be highly reactive and, as a consequence, toxic to most organisms. They are produced by an expanding variety of anthropogenic sources suggesting an increasingly important role for this form of pollution. The toxic effect of heavy metals appears to be related to production of reactive oxygen species (ROS) and the resulting unbalanced cellular redox status. Algae respond to heavy metals by induction of several antioxidants, including diverse enzymes such as superoxide dismutase, catalase, glutathione peroxidase and ascorbate peroxidase, and the synthesis of low molecular weight compounds such as carotenoids and glutathione. At high, or acute, levels of metal pollutants, damage to algal cells occurs because ROS levels exceed the capacity of the cell to cope. At lower, or chronic, levels algae accumulate heavy metals and can pass them on to organisms of other trophic levels such as mollusks, crustaceans, and fishes. We review here the evidence linking metal accumulation, cellular toxicity, and the generation of ROS in aquatic environments.

The ability of phytoplankton to cope with oxidative stress is one of the main factors that influence its survival in the marine environment, when senescence conditions prevail. In a first attempt to investigate the antioxidant strategies of different phytoplanktonic groups face to oxidative stress, the superoxide dismutase (SOD; EC 1.15.1.1) activity and photosynthetic pigment content along the growth curves of the dinoflagellate Lingulodinium polyedrum (Stein) Dodge, the prasinophycean Tetraselmis gracilis (Kylin) Butcher and the diatom Minutocellus polymorphus (Hargraves and Guillard) Hasle, von Stosch and Syvertsen were evaluated in batch-cultures. Total SOD activity was determined by an indirect method involving the inhibition of cytochrome c reduction. The contents of photosynthetic pigments were analysed by HPLC using a reverse phase column (RP-18), based on a ternary gradient. A peak of total SOD activity was detected at the beginning of the T. gracilis and M. polymorphus exponential growth. In L. polyedrum and M. polymorphus, SOD activity increased approximately three times by day 17 of growth, compared to the values obtained on day 3 (exponential phase) of the growth curve. All three species of microalgae had reduced SOD activity at the end of their growth. The levels of peridinin in L. polyedrum increased about 60% by day 17 of growth compared to the values obtained at exponential phase. Tetraselmis gracilis exhibited a remarkable increase (approximately 85%) in beta-carotene concentration after 10-14 days of growth whereas the beta-carotene levels in M. polymorphus decreased about 85% along its growth curve. These findings suggest that the antioxidant response during senescence in batch-cultures differ according to the species. Induction of SOD activity may occur either in the early exponential or stationary growth phases, which is important to prevent oxidative stress triggered by a number of factors that affects growth, such as nutrient and light availability.

No abstract

Algal growth potential was used to quantify the degree of eutrophication of three coastal regions in São Paulo, Brazil which are subject to sewage disposal. Surface water was collected in Praia Grande, Santos, Guarujá and São Sebastião during two surveys (low tourist season—October 1997 and high tourist season—March 1998). Water was filtered and used in chlorophyll-a and nutrient analyses and in bioassays. Samples were inoculated with the diatom Phaeodactylum tricornutum Bohlin, and then subdivided into seven replicates. During a ten days experiment, in vivo fluorescence was performed and algal growth potential was calculated. Values were expressed as absolute in vivo fluorescence, as well as with a ratio of in vivo fluorescence of sample in relation to the fluorescence of control sea water for each treatment which defines the trophic status. The results of these bioassays showed a growing degree of eutrophication among regions: Praia Grande ∼ São Sebastião → Guarujá → Santos. It also identified sewage disposals and estuarine discharges as the main sources causing eutrophication. This bioassay technique is an important tool for environmental pre-monitoring studies, giving useful results in a short time.

No abstract

No abstract

. Abstract: The liquid eftluent from an oil maritime terminal, with produced water as the main component, had its toxicity evaluated through toxicity tests with the diatom Skeletonema costatum. Two previously treated eftluent samples (eftluents A and B), were provided by PETROBRAS for the experiments. Both samples presented high salinity (67%0for eftluent A and 62%0for eftluent B) and low pH values (6.2), whereas total sulphide, phenol and nutrient content, dissolvedldispersed petroleum hydrocarbon concentration, BOD and COD values were quite different from each other. During the toxicity experiment, three replicate flasks with samples for each treatment were exposed to a light radiation of 266).tEm-2S-Iand maintained under a 10 h/l4 h light/dark cycle, at a temperature of 24 :t 2°C. The ECSOvalues could not be accurately estimated for eftluent A: 60 h and 132 h afier starting the experiment they were below 3% and between 3-6% eftluent concentration, respectively. Synergistic effects between eftluent toxicity and salinity on the growth of S. costatum were detected. The eftluent B showed higher toxicity: the ECSOvalues were 0.17% and 0.40% of eftluent concentrations, afier 48 h and 96 h, respectively. These results evidenced the deleterious effects of residual organic compounds contained in the aqueous eftluents from the oil terminal under the present pretreatment on S. costatum. ln the light of the present data, the direct disposal of these eftluents into São Sebastião Channel waters might be very hazardous to its indigenous biota.. Resumo: A toxicidade do efluente líquido do "Outos e Terminais Centro-Oeste São Paulo" (OTCS)terminal marítimo de petróleo da PETROBRAS, em São Sebastião (SP, Brasil), cujo principal componente é a água de produção, foi avaliada através de testes de toxicidade com a diatomácea Skeletonema costatum. Amostras de dois efluentes (A e B), previamente tratados pela PETROBRAS, foram utilizadas nos experimentos. As duas amostras apresentaram alta salinidade (A=67%0;B=62%0)e baixo valor de pH (6,2), enquanto que as suas concentrações de sulfetos, fenóis e hidrocarbonetos de petróleo dissolvidos/dispersos, bem como os seus valores de OBO e OQO, foram bastante distintos. Nos experimentos de toxicidade, os frascos experimentais, em triplicata, para cada tratamento foram expostos à radiação luminosa fluorescente de 266 Ilm-2S-I e mantidas em um ciclo luz/escuro de 10 h/l4 h, a uma temperatura de 24 :t 2°C. Os valores de CEso não puderam ser determinados com precisão para o efluente A: após 60 h e 132 h do início dos experimentos esses valores estavam abaixo de 3% e entre 3-6% da concentração de efluente, respectivamente. Foi observado sinergismo entre a toxicidade e a salinidade do efluente sobre o crescimento de S. costatum. O efluente B apresentou uma toxicidade mais elevada: os valores de CEso foram 0,17% e 0,40% da concentração do efluente, após 48 h e 96 h, respectivamente. Estes resultados evidenciaram claramente os efeitos deletérios dos compostos orgânicos residuais contidos no efluente l...

No abstract