Estrutura e dinâmica do fitoplânctone bacterioplâncton em cultivos de camarão no Rio Grande do Norte-Brasil: impacto sobre o ambiente natural

This work aimed to study the structure and dynamic of Phytoplankton and Bacterioplankton in a complete cycle of shrimp cultivation (Litopenaeus vannamei) and determine the environmental factors responsible for the structural changes of these communities. The study was realized in a saltwater shrimp farm (Macaíba, RN), between September/2005 and February/2006, and in a freshwater shrimp farm (Ceará Mirim, RN), between May/2007 and September 2007. The samplings were collected weekly in saltwater farm and every fifteen days in freshwater farm. Total phosphorus, chlorophyll a and environmental parameters (pH, dissolved oxygen, salinity, temperature, depth and water transparency) were measured. Qualitative and quantitative analysis of the phytoplankton and bacterioplankton were carried out. The Shannon-Wiener ecologic indexes of diversity and the Pielou equitability indexes were calculated to the phytoplankton. Bacterial density was determined by epifluorescence microscopy. The data were statistically analyzed by Pearson correlation and t-Test. Chlorophycea were predominat in salt water and in the captation/drainage point (24 to 99%). Diatoms had higher wealth. The species Choricystis minor had the highest occurrence (100%) and dominance (90-100%), thus showing its adaptation to the high temperatures, salinity and low water transparency conditions. Filamentous Cyanobacteria like Oscillatoria sp., Pseudoanabaena sp. and Phormidium sp. had constant levels. The negative correlation between chlorophycea and water transparency, and the positive correlation between chlorophyll a and salinity, showed that the phytoplankton was well adapted to the low transparency and to the high salinity. The bacterioplankton was negatively correlated with the total phosphorus and salinity. In freshwater, Cyanobacteria were predominant (>80%), presenting some producers of toxins species like Microcystis sp., Aphanizomenon sp., Cylindrospermopsis raciborskii e Anabaena circinalis. Cyanobacterial density and total phosphorus and chlorophyll a concentrations exceeded the maximum value allowed by legislation. The means of total phosphorus varied from 264 to 627 Wg.L-1 and the means of chlorophyll a oscillated between 22 and 182 Wg.L-1. The phytoplankton species were selected by low availability of the light, high pH, temperature and high availability of total phosphorus. The bacterioplankton showed high densities (5,13 x 107 to 8,50 x107 Bac.mL-1). The studied environments (ponds and rivers) presented a high level of trophic state based on the high concentrations of chlorophyll a and total phosphorus and cyanobacteria dominance. The composition of species in the ponds and rivers was similar, as well as high concentrations of total phosphorus and chlorophyll a, highlighting the pollution caused by the discharges of the farms in natural environment

Influência dos fatores abióticos sobre a variação espaço-temporal de paralonchurus brasiliensis (Steindachner, 1875) (pisces, sciaenidae) componente da fauna acompanhante da pesca de camarões no litoral Norte de São Paulo

Knowledge of the environmental factors influence on the spatial-temporal variation of fishes is important to fisheries management and conservation. Thus, the aim of this work was to analyze the influence of the abiotical factors on the spatial-temporal distribution of Paralonchurus brasiliensis (Pisces, Sciaenidae) caught by-catch with the shrimp fishing of Ubatuba and Caraguatatuba regions, north coast of São Paulo State. The fishes were captured every month from January to December 2002. Samples were collected by otter trawl at 5, 10, 15, 20, 25, 30 and 35m depths. The temperatures (surface and bottom), salinities (surface and bottom), sediment features and organic matters were verified for each depth. During all period of the study 12.642 specimens of P. brasiliensis were captured at Ubatuba and 17.166 at Caraguatatuba, which totalized the biomass of 267 for the first and 339kg for the other region. The females outnumbered males in fish population. The greatest values of biomass and number of individuals were registered at the summer and autumn seasons, while the lowest values were observed at the winter and spring seasons. The greatest abundances were found from 15 to 25m depth. In this study, it was verified that P. brasiliensis is a coastal waters associate species. The spatialtemporal distribution of P. brasiliensis is affected by intrusion of SACW and depth for the coastal region and by depth and sediment in sheltered areas such as Caraguatatuba

Potencialidades de cultivo de macroalgas no litoral do Rio Grande do Norte (NE, Brasil): uma perspectiva de integração de dados ambientais em sistemas de informação geográfica (SIG)

Since centuries ago, the Asians use seaweed as an important source of feeding and are their greatest world-wide consumers. The migration of these peoples for other countries, made the demand for seaweed to increase. This increasing demand prompted an industry with annual values of around US$ 6 billion. The algal biomass used for the industry is collected in natural reservoirs or cultivated. The market necessity for products of the seaweed base promotes an unsustainable exploration of the natural banks, compromising its associated biological balance. In this context, seaweed culture appears as a viable alternative to prevent the depletion of these natural supplies. Geographic Information Systems (GIS) provide space and produce information that can facilitate the evaluation of important physical and socio-economic characteristics for the planning of seaweed culture. This objective of this study is to identify potential coastal areas for seaweed culture in the state of Rio Grande do Norte, from the integration of social-environmental data in the SIG. In order to achieve this objective, a geo-referred database composed of geographical maps, nautical maps and orbital digital images was assembled; and a bank of attributes including physical and oceanographical variables (winds, chains, bathymetry, operational distance from the culture) and social and environmental factors (main income, experience with seaweed harvesting, demographic density, proximity of the sheltered coast and distance of the banks) was produced. In the modeling of the data, the integration of the space database with the bank of attributes for the attainment of the map of potentiality of seaweed culture was carried out. Of a total of 2,011 ha analyzed by the GIS for the culture of seaweed, around 34% or 682 ha were indicated as high potential, 55% or 1,101 ha as medium potential, and 11% or 228 ha as low potential. The good indices of potentiality obtained in the localities studied demonstrate that there are adequate conditions for the installation of seaweed culture in the state of Rio Grande do Norte