Phytoplanktonic composition of three cultivation systems used in Litopenaeus vannamei (BOONE, 1931) marine shrimp farms = Composição fitoplanctônica em três sistemas de cultivo do camarão marinho Litopenaeus vannamei (BOONE, 1931)

The aim of this work is to assess the different compositions of phytoplankton in three cultivation systems of marine shrimps Litopenaeus vannamei (BOONE, 1931), denominated as organic, intensive and semi intensive. The samples were done fortnightly, when phytoplankton was collected by a net for phytoplankton, 65 ƒÊm mesh, being then filtrated in a total volume of water of 100 L, and preserved in formaldehyde solution at 4% and identified according to the methodology of Cordeiro et al. (1997). The results show that the densities of Diatoms were of 16.65, 10.47 and 7.57 cel. 103 mL-1 for the organic, intensive and semi intensive cultivations, respectively. As for cyanobacteria, the average figures were 42.06 cel. 103 mL-1 forsemi intensive 17.27 cel. 103 mL-1, in the intensive cultivation and 6.11 cel. 103 mL-1 for the organic cultivation system. The dinoflagellates had the highest cellular density in the phytoplankton community analyzed with 61.9 cel. 103 mL-1 in the intensive cultivation, 0.33 and 0.03 cel. 103 mL-1 for both semi intensive and organic cultivation systems respectively. Euglenas presented the results of 4.98 and 14.86 cel. 103 mL-1 only for semi intensive and intensive cultivations. It was then concluded that all cultivations presented average rates below recommended for such studied systems.Conduziu-se esse trabalho com o objetivo de avaliar as diferentes composicoes fitoplanctonicas em tres sistemas de cultivo para o camarao marinho Litopenaeus vannamei (BOONE, 1931), denominados de organico, intensivo e semiintensivo. As amostragens foram realizadas quinzenalmente, onde o fitoplancton foi coletado atraves de uma rede de plancton, com malha de 65 ƒÊm, sendo filtrado um volume de agua total de 100 litros, que foram preservadas em solucao de formol a 4% e identificadas segundo a metodologia de Cordeiro et al. (1997). Os resultados mostram que as densidades de diatomaceas foram de 16,65; 10,47 e 7,57 cel. 103 mL-1, respectivamente, para os cultivos organico, intensivo e semi-intensivo. Para as cianoficeas as medias foram 42,06 cel. 103 mL-1 no semi-intensivo, 17,27 cel. 103 mL-1 intensivo e 6,11 cel. 103 mL-1no sistema organico de criacao. Os dinoflagelados obtiveram a maior densidade celular dentre a comunidade fitoplanctonica analisada de 61,9 cel. 103 mL-1 no cultivo intensivo, 0,33 e 0,03 cel. 103 mL-1 para o semi-intensivo e organico,respectivamente. As euglenas apresentaram densidades apenas para os cultivos semi-intensivo e intensivo de 4,98 e 14,86 cel. 103 mL-1. Conclui-se que as densidades fitoplantonicas em todos os cultivos estiveram abaixo daquelas recomendadas para os sistemas estudados