Avaliação da toxicidade de florações naturais e de cultura de cianobactérias: efeitos sobre Ceriodaphnia silvestri (Crustacea, Cladocera)

The incidence of toxic cyanobacterial blooms is one of the important consequences of eutrophication in aquatic ecosystems. It is a very common phenomenon in reservoirs and shrimp ponds in the State of Rio Grande do Norte (RN), Brazil. Cyanobacterias produce toxins which can affect aquatic organisms and men trough the food chain. Aiming to contribute to the studies of cyanobacterias in RN, we propose: a) to evaluate the toxicity of isolated cyanobacterias in important fresh-water environments; and b) to verify the effects of both natural and cultured blooms occurred in reservoirs for human supply and in the cladoceran Ceriodaphnia silvestrii. This study was carried out using samples of natural blooms occurred between March and October of 2004 in Gargalheiras Dam (08º L e 39º W), in July of 2004 in Armando Ribeiro Gonçalves Dam (06o S e 37o W) and in commercial shrimp ponds (Litopenaeus vannamei) located in fresh-water environments. The samples were collected with plankton net (20µm.) for identification, isolation and obtaining of phytoplanktonic biomass for liophilization and later toxicity bioassays. The toxicity of cultured samples and natural blooms was investigated through bioassays in Swiss mice. Quantification of cyanobacteria in samples was conducted following the Ütermol method, with 300mL samples fixed with lugol. The toxicity test with Ceriodaphnia silvestrii followed ABNT, 2001 recommendations, and were accomplished with natural hepatotoxic bloom s samples and cultured samples of both non-toxic and neurotoxic C. raciborskii. In this test, five newborns, aged between 6 and 24 hours, were exposed to different concentrations (0 a 800 mg.L-1) of crude cyanobacterial extracts during 24 and 48 hours. Three replicates were used per treatment. The pH, temperature and dissolved oxygen at the beginning and after 24 and 48hours from the test were measured. We estimated the CL50 through the Trimmed Spearman-Karber method. The blooms were constituted by Microcystis panniformis, M. aeruginosa, Anabaena circinalis, Cylindrospermopsis raciborskii and Planktothrix agardhii, producers of mycrocistin-LR confirmed with HPLC analysis. Samples of hepatotoxic blooms registered toxinogenic potential for C. silvestrii, with CL50-24h value of 47.48 mg.L-1 and CL5048h of 38.15 mg.L-1 for GARG samples in march/2005; CL50-24h of 113,13 mg.L-1 and CL5048h of 88,24 mg.L-1 for ARG July/2004; CL50-24h of 300.39 mg.L-1 and CL50-48h of 149.89 mg.L-1 for GARG October/2005. For cultured samples, values of CL50-24h and CL50-48h for C. raciborskii toxic strains were 228.05 and 120.28 mg.L-1, respectively. There was no mortality of C. silvestrii during the tests with non-toxic C. raciborskii strain. The toxicity test with C. silvestrii presented good sensitivity degree to cyanotoxins. The toxicity of natural hepatotoxic blooms samples (microcystins) and cultured neurotoxic saxitoxins producer samples analyzed in this study give us strong indications of that toxin s influence on the zooplanktonic community structure in tropical aquatic environments. Eleven cyanobacteria strains were isolated, representing 6 species: Anabaenopsis sp., Cylindrospermopsis raciborskii, Chroococcus sp., Microcystis panniformis, Geitlerinema unigranulatum e Planktothrix agardhii. None presented toxicity in Swiss mice. The strains were catalogued and deposited in the Laboratório de Ecologia e Toxicologia de Organismos Aquáticos (LETMA), in UFRN, and will be utilized in ecotoxicológical and ecophysiological studies, aiming to clarify the causes and control of cyanobacterial blooms in aquatic environments in RN. This state s reservoirs must receive broader attention from the authorities, considering the constant blooms occurring in waters used for human consumption

Avaliação ecológico-econômica do manguezal de Macau/RN e a importância da aplicação de práticas preservacionistas pela indústria petrolífera local

This work presents the results of a survey in oil-producing region of the Macau City, northern coast of Rio Grande do Norte. All work was performed under the Project for Monitoring Environmental Change and the Influence of Hydrodynamic forcing on Morphology Beach Grass Fields, Serra Potiguar in Macau, with the support of the Laboratory of Geoprocessing, linked to PRH22 - Training Program in Geology Geophysics and Information Technology Oil and Gas - Department of Geology/CCET/UFRN and the Post-Graduation in Science and Engineering Oil/PPGCEP/UFRN. Within the economic-ecological context, this paper assesses the importance of mangrove ecosystem in the region of Macau and its surroundings as well as in the following investigative exploration of potential areas for projects involving reforestation and / or Environmental Restoration. At first it was confirmed the ecological potential of mangrove forests, with primary functions: (i) protection and stabilization of the shoreline, (ii) nursery of marine life, and (iii) source of organic matter to aquatic ecosystems, (iv) refuge of species, among others. In the second phase, using Landsat imagery and techniques of Digital Image Processing (DIP), I came across about 18,000 acres of land that can be worked on environmental projects, being inserted in the rules signed the Kyoto Protocol to the market carbon. The results also revealed a total area of 14,723.75 hectares of activity of shrimp production and salting that can be harnessed for the social, economic and environmental potential of the region, considering that over 60% of this area, ie, 8,800 acres, may be used in the planting of the genus Avicennia considered by the literature that the species best sequesters atmospheric carbon, reaching a mean value of 59.79 tons / ha of mangrove

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.

Efeitos do enriquecimento com nutrientes (N e P) em diferentes condições de luz sobre o crescimento do fitoplâncton em um reservatório eutrófico no semi-árido brasileiro

The increasing of pollution in aquatic ecosystems in the last decades has caused an expansion of eutrophication and loss of water quality for human consumption. The increase of frequency and intensity of cyanobacteria blooms have been recognized as a major problem connected to water quality and eutrophication. The knowledge of environmental factors controlling these blooms is a key step towards the management for recovering aquatic ecosystems from eutrophic conditions. Primary productivity in aquatic ecosystems is dependent on light and nutrients availability. In the present work we evaluated the relative importance of the concentration of major nutrients, such as phosphorus and nitrogen, and light for phytoplankton growth in the main water reservoir of Rio Grande do Norte State, named Engenheiro Armando Ribeiro Gonçalves (EARG), which is an eutrophic system, dominated by potentially toxic cyanobacteria populations. Limitation of phytoplankton growth was evaluated through bioassays using differential enrichment of nutrients (N and/or P) under two light conditions (low light and high light) and monthly monitoring of chlorophyll-a and nutrients (total nitrogen and phosphorus) concentrations, and water transparency (Secchi depth) at the pelagic region. Our results confirm that EARG reservoir is an eutrophic system with a low water quality. Results of bioassays on the growth of phytoplankton limitation (N or P) were conflicting with the results predicted by the TN:TP ratios, which indicates that these ratios were not a good indicator of algal growth limitation. Nitrogen was the limiting nutrient, considering both frequency and magnitude. Light and hidrology affected phytoplankton response to nutrient enrichment. The extreme eutrophic conditions of this reservoir, dominated by cyanobacteria blooms, demand urgent managing strategies in order to guarantee the multiple uses for this system, including water supply for human population. Although nitrogen is the limiting nutrient, an effective management program must focus on the reduction of both phosphorus and nitrogen input

Influência da matéria orgânica dissolvida alóctone e autóctone sobre o balanço de carbono em sistemas aquáticos: um experimento em mesocosmos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Superação de dormência de sementes de Ceratophyllum demersum

Dentre as várias plantas daninhas aquáticas imersas que proliferam nos reservatórios de usinas hidrelétricas, destaca-se em importância Ceratophyllum demersum, devido à sua grande capacidade de reprodução e produção de biomassa. Contudo, apesar de problemática, estudos relacionados com o mecanismo de propagação e persistência dessa espécie em ambiente aquático são bastante escassos no Brasil. Dessa forma, o objetivo deste estudo foi avaliar diferentes métodos de superação de dormência em sementes desta planta daninha aquática coletadas na Lagoa Vírgula, localizada no rio Tietê-SP. As sementes coletadas foram divididas em dois lotes, sendo um constituído por sementes acondicionadas em um recipiente contendo água destilada e o outro por sementes acondicionadas em sacos de papel em condições de câmara fria (16,8 ºC). Após 650 dias da coleta das sementes, foram realizados os testes de superação de dormência, utilizando os seguintes tratamentos: escarificação manual; imersão em ácido sulfúrico concentrado (98%) por 5, 15, 25 e 35 minutos; imersão em água quente (98 ºC); e testemunha A, constituída pelo lote de sementes acondicionadas em um recipiente contendo água destilada, e uma testemunha B, constituída pelo lote de sementes acondicionadas em saco de papel. Os resultados demonstraram que a espécie C. demersum produz sementes férteis e podem permanecer viáveis no sedimento por vários anos após a fecundação. A escarificação das sementes foi o método mais eficaz na superação da dormência, sendo significativamente superior aos demais tratamentos e apresentando 65,0% de germinação aos 79 DAT. Ficou evidente a necessidade de realização de mais estudos para determinação de uma metodologia mais adequada à avaliação de dormência em sementes de C. demersum.

Longitudinal distribution and seasonality of macroalgae in a subtropical stream impacted by organic pollution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Os reservatórios eutrofizados da região tropical semiárida atuam como emissores ou como sequestradores de dióxido de carbono?

The aquatic ecosystems can play a role as carbon-dioxide-source or carbon-dioxide-sink systems due to the high predominance of heterotrophic or autotrophic metabolism. The primary production can strongly affect the carbon balance (CO2) through the consumption of carbon dioxide in the photosynthesis, especially in eutrophic environment, acting as a carbon sink. The present study tested the hypothesis that the eutrophic reservoirs in tropical semi-arid region are carbon dioxide-sink systems due to the high primary productivity presented in these systems. Five Brazilian reservoirs from the semi-arid in the northeast region were monitored monthly during four years (2010 to 2013) with a prolonged drought event identified during the study. The results showed an increasing level of eutrophication over the period of prolonged drought, with the predominance of autotrophy. Significant negative correlations were observed between the partial pressure of CO2 (pCO2) (p<0,001) and chlorophyll-a in the Boqueirão, Passagem das Traíras, Dourado and Gargalheiras reservoirs, showing a pattern of the carbon dioxide-sink systems. However, this pattern was not found in Cruzeta reservoir. In summary, in the tropical semi-arid region, hydrological and morphometric variables can lead to different behaviors of the water-supply reservoirs on the carbon metabolism. The eutrophic reservoirs evaluated showed a negative relationship between pCO2 and Chl-a, which suggests that these water bodies show an autotrophic metabolism and behave as carbon dioxide- sink systems

Qualidade de água como tema para a socialização do conhecimento científico em região semi-árida brasileira

During the dry and rainy periods, in the Piranhas-Assu river hydrographic basin, variations in bacterioplankton and trophic state indexes were studied in the lotic and lentic environments. The means of total bacterial density wavered in the order of 107 organisms. mL-1 and they were higher in the rainy period. Cocci bacteria were numerically predominant in all sampling points, influencing the total abundance of bacterioplankton. Total bacterial biomass varied from 659 to 1997,3 µgC.L-1 due to the high values of filaments cellular volume. Total phosphorus amounted 108 µg.L-1 and it had a positive correlation with chlorophyll a (r = 0,94; p < 0,05) during dry period, when these variables presented higher concentrations. There wasn t a high spatial variation. The low transparency of water and the phosphorus and chlorophyll concentrations indicated eutrophic or hipereutrophic levels in studied points of reservoir. These variables, associated with high density and biomass values found, alert to the necessity of a constant monitoring of the semi-arid aquatic ecosystems, where the quality of water is affected by dry occurrence

Usos e qualidade da água em região semi-árida do nordeste brasileiro: percepção ambiental de professores e alunos

Density and biomass of bacterioplankton in parts of the Marechal Dutra reservoir were studied in periods of dry and rainy season. The averages of the total bacterial densities oscillated in the order of 107 organisms/ mL of sample. The cocci cells were numerically predominant, influencing considerably the total abundance of the bacterioplankton. The total bacterial biomass, was considered raised and varied from 2.431,82 to 2.739,01 μgC.L-1, in function of the high values of biovolume of the filaments forms, and showed no marked spacial fluctuation. These high values of density and biomass alert for the necessity of a frequent monitoring of aquatic ecosystems of semi-arid region, where the quality of the water is affected by the occurrence of extensive dry periods, influencing considerably the quality of life of its population

Avaliação do potencial mutagênico da água do açude de Lucrécia (RN- Brasil): um enfoque na relação saúde e ambiente

The water quality of many reservoirs in the world has been reduced due to percolation of contaminants to water, which can have natural or anthropogenic origin, increasing the level of genotoxic compounds in aquatic ecosystems. This fact has contributed to the reduction of environmental quality, and commitment the health of living beings that inhabit these ecosystems, including the human population. In this backdrop of reduced water quality, is the Lucrecia dam, which is a major surface water reservoirs by volume of semi-arid region of Rio Grande do Norte, and that has shown contamination by heavy metals, cyanobacteria toxic and the natural presence of Radon. The population that use this source has been showing high rates of cancer, popularly associated with the consumption of this water, with a prevalence about three times higher compared to the whole state of Rio Grande do Norte. Based on this, the present study aimed to evaluate the mutagenic potencial of surface water from the Lucrecia dam, using the Micronucleus Test in Tradescantia pallida (Trad-MN) and in human peripheral blood lymphocytes (CBMN) assay, as well as identify the concentrations of some heavy metals in this water. Water samples were collected on a dry season and a rainy season, in two distinct points. Moreover, in order to bring a completely view about the relationship of man-health-environment in this local, through the knowledge of knowing / acting environmental from residents of Lucrecia, and the use and perceptions they have about the dam of your city, a study of Environmental Perception was carried out with local residents. The results obtained for the both micronucleus test, showed significant results for the three points analyzed. The strongest mutagenic effect was observed in the dry season for both assays. Chemical analyses detected an increase of heavy metal levels in different points and season above the maximum allowed by legislation. Regarding the study of Environmental Perception with local residents, it was observed the knowledge of the environment that the residents have, as well as the strong ties and perceptions with the dam of the city. Thus, the combination of these two aspects (the genetic toxicity tests conducted in the dam together with analysis of environmental perception with the residents of Lucrecia) allowed to draw a more complete diagnosis on the local situation

Protozoários de vida livre em dois trechos da bacia hidrográfica do rio pirangi (RN): relações com a educação em ciências e preservação

The vast hidric wealth of Brazil gets its watersheds more susceptible to impacts that compromise the water quality, affecting the ecosystem stability of aquatic environments. The decrease in the quality of water resources also results in a decrease of its multiple uses, especially in tourist areas of the coast, where the continuous flow of people to these sites increases even further the probability of inappropriate behavior of both tourists and local residents. Studies regarding the microbiological communities are still scarce, especially on the free-living protozoa that play unique roles in the food chain of aquatic ecosystems. Due to the large role played by this group of microorganisms in aquatic environments, the present study aimed at identifying the genus and species of free-living protozoa present in two sections of the Pium River, east coast of Rio Grande do Norte, making an association between the its occurrence and trophic conditions of the environment in which they are, also checking the bioindicator capacity of these organisms in water quality. It also aimed to conduct a survey with students to identify the main difficulties regarding the knowledge of free-living protozoa and hydric transmission diseases in two public schools near the river studied in the Pium district, county of Parnamirim. The survey was analyzed by means of questionnaires at both schools. Students identified several activities developed Pium river, highlighting its multifunctionality and importance to the region. A total of 76 taxa of free-living protozoa was recorded, of these, 33 were ciliates, 19 flagellates and 24 sarcodia. The spatial and temporal patterns of these organisms to both points studied revealed the bioindicator potentiality of some effective species identified. However, knowledge about the free-living protozoa proved quite lagged, presenting misconceptions that show them as pathogenic organisms exclusively, totally disregarding their ecological role. In order to remedy the flaws existing in students in relation to the functional role of protozoa, workshops were planned on these microorganisms while also addressing issues related to hydric transmission diseases through lectures, recreational activities and interactive presentations. These practical activities of Science Education had the goal of bringing students the context of local water resources, aiming to promote a greater clarification regarding of the functional role of free-living protozoa in aquatic environments

Evolutionary perspectives on seed consumption and dispersal by fishes

Fishes probably were the first vertebrate seed dispersers, yet little research has examined this phenomenon. We review evidence of fruit and seed consumption by fishes, and analyze the evolution of frugivory and granivory using South American serrasalmids as a model. Frugivory and granivory are observed among diverse fish taxa worldwide, although most reports are from the Neotropics. Frugivory and granivory among serrasalmids apparently are derived from omnivory, with powerful jaws and specialized dentition appearing as major adaptations. No particular fruit traits seem to be associated with seed dispersal by fishes (ichthyochory). Recent experimental evidence of ichthyochory suggests that fishes can influence riparian vegetation dynamics. Because of deleterious human impacts on aquatic ecosystems worldwide, many critical interactions between plants and fishes have been disrupted before they could be studied. Exotic frugivorous fishes have recently become established on foreign continents, with unknown ecological consequences.

The invasion of five alien species in the Delta do Parnaiba Environmental Protection Area, Northeastern Brazil

Marine biological invasions have been regarded as one of the major causes of native biodiversity loss, with shipping and aquaculture being the leading contributors for the introductions of alien species in aquatic ecosystems. In the present study, five aquatic alien species (one mollusk, three crustaceans and one fish species) were detected during dives, shore searches and from the fisheries on the coast of the Delta do Parnaiba Environmental Protection Area, in the States of Piaui and Maranhao, Northeastern Brazil. The species were the bicolor purse-oyster Isognomon bicolor, the whiteleg shrimp Litopenaeus vannamei, the giant river prawn Macrobrachium rosenbergii, the Indo-Pacific swimming crab Charybdis hellerii and, the muzzled blenny Omobranchus punctatus. Ballast water (I. bicolor, C. hellerii, and O. punctatus) and aquaculture activities (L. vannamei and M. rosenbergii) in adjacent areas are the most likely vectors of introduction. All exotic species found have potential impact risks to the environment because they are able to compete against native species for resources (food and habitat). Isognomon bicolor share the same habitat and food items with the native bivalve species of mussels and barnacles. Litopenaeus vannamei share the same habitat and food items with the native penaeids such as the pinkspot shrimp Farfantepenaeus brasiliensis, the Southern brown shrimp Farfantepenaeus subtilis, and the Southern white shrimp Litopenaeus schmitti, and in the past few years L. vannamei was responsible for a viral epidemics in the cultivation tanks that could be transmitted to native penaeid shrimps. Charybdis hellerii is also able to cause impacts on the local fisheries as the species can decrease the populations of native portunid crabs which are commercialized in the studied region. Macrobrachium rosenbergii may be sharing natural resources with the Amazon River prawn Macrobrachium amazonicum. Omobranchus punctatus shares habit with the native redlip blenny Ophioblennius atlanticus and other fishes, such as the frillfin goby Bathigobius soporator. Some immediate remedial measures to prevent further introductions from ballast water and shrimp farm ponds should be: (i) to prevent the release of ballast water by ship/vessels in the region; (ii) to reroute all effluent waters from shrimp rearing facilities through an underground or above-ground dry well; (iii) to install adequate sand and gravel filter which will allow passage of water but not livestock; (iv) outdoor shrimp pounds located on floodable land should be diked, and; (v) to promote environmental awareness of those directly involved with ballast water (crews of ship/vessels) and shrimp farms in the region. Rev. Biol. Trop. 58 (3): 909-923. Epub 2010 September 01.

A model for the plankton system of the Broa reservoir, Sao Carlos, Brazil

In this paper a model, called ELLOBO running in STELLA II, was set to describe the plankton system of the Broa reservoir (SP). The three state variables of the model are: phytoplankton, zooplankton, and the fish Astyanax fasciatus. The forcing variables are: temperature, nitrate, phosphorus and solar radiation. The model did not consider the cycling of nutrients inside the reservoir. The results show that: temperature is the principal forcing variable in the phytoplankton dynamic and in the subsequent evolution of the whole system. The zooplankton predation was described by Odum's equation, and there is a strong random component in zooplankton grazing, which was essential for the model, because zooplankton estimates have high variance. One must collect data in a short space of time (maybe daily) to better explain the zooplankton and phytoplankton variation. Validation was performed using simple statistics (arithmetic mean, standard deviation) and the results show concordance between observed and simulated values. Overhead was used to calibrate some parameters and to validate the model. The highest overhead value (5%) imply in the better accordance between estimated and;observed state variables values. We believe this approach in Broa reservoir will provide an useful tool for future research and it could be used comparatively in other continental aquatic ecosystems. (C) 2000 Elsevier B.V. B.V. All rights reserved.