A comunidade planctÃnica como indicadora da qualidade da Ãgua em viveiros de cultivo de camarÃes no nordeste do Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

A disease of unknown origin is occurring in marine shrimp (Litopenaeus vannamei) ponds causing a decrease in the survival rate of cultured organisms. The disease named Idiopathic Abdominal Necrosis (IAN) have been confirmed in ponds from 14 farms located in PiauÃ, MaranhÃo, Cearà and Rio Grande do Norte states, Northeastern Brazil. In order to contribute to the knowledge of this disease and its relation to the performance of the shrimps in the ponds, the plankton from 14 farms was studied from october/2003 to november/2003. The ponds were categorized in high stocking density (>30 PL/m2). In each farm sampling were made in tree stations (intake water point; pond 1 â without viruses indicia; pond 2 â with viruses indicia). Water samples for phytoplankton were collected with a 100 mL plastic bottle and samples preserved with 1% Lugolâs iodine solution. Zooplankton samplings at each station was conducted with a standard plankton net with 1 m length, 30 cm mouth diameter and mesh size of 50 micrometers; 3 minutes horizontal subsurface hauls were made at each site. Samples were preserved in a 4% buffered formalin/seawater solution. Phytoplankton consisted of 51 infrageneric taxa with concentrations ranging from 365,218  416,615 cell.mL-1 to 1,961,675  3,160,172 cell.mL-1. Diatoms contributed to almost 70% and high densities resulted from Cyanophyta blooms, mainly Pseudanabaena cf limnetica. Forty zooplankton taxa were registered and essentially composed of typical marine euryhaline species and suspension-feeders. Zooplankton varied from 972  209 ind.m-3 to 4,235  2,877 ind.m-3.Copepoda dominated (45%) followed by Protozoa (18%), Rotifera and Mollusca larvae (with 12%, each). Enhanced nutrient input affected plankton density and composition. Diatoms and copepods dominance were replaced by cyanobacteria, protozoan and rotifers as nutrient concentrations increased with the cultured period, indicating that plankton structure was affected by eutrophic conditions. Although environmental quality ponds was poor the plankton community indicates that the environment is resilient being possible to return to a better condition, since good management practices will be employed.

ASSUNTO(S)

zooplankton aquaculture brazil aqÃicultura fitoplÃncton litopenaeus vannamei zooplÃncton camarÃo, litopenaeus vannamei, brasil shrimp phytoplankton oceanografia

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