Efeito da sazonalidade e das fases do cultivo do camarão Litopenaeus vannamei (BOONE, 1931) na composição das assembleias fitoplanctônicas de um tributário do Baixo São Francisco

Abstract

Phytoplankton assemblages are formed by organisms with high morphological, ecological and phisyological variabilities, being constituted by unicelular, filamentous and/or colonial microalgae that inhabits the water column space near the surface. Environmental changes, depending on frequency and intensity, may cause alterations in these assemblages structure. In addition, to understand the phytoplanktonic composition of shrimp ponds is substantial to identify the microalgae groups that are presente and achieve a farming system that is balanced. In this sense, this research aimed to evaluate the influence of seasonality ando f the different Litopenaeus vannamei shrimp farming phases of the Brejo Gramde – SE region on the phytoplanktonic assemblages structure. The sampling occurred during dry and wet seasons from July 2019 July to August 2021. A phytoplankton net was used to capture phytoplanktonic species and the samples were carried to te Laboratório de Ecologia Vegetal for taxon identification. Statistical analyses were realized in the R environment. A distance based linear model (DistLM) built with the Vegan package was implemented to test the effects of seasonality, sampling year and farming phase, an indication value analysis (IndVal) was applied to identify which taxons were responsible for the differences found in the DistLM. A total of 121 taxons distributed in 7 divisions, 39 families and 59 genera was found. The divisions that beared the higher species richnesses were Cyanobacteria, Chlorophyceae and Bacillariophyta. Our data showed nor seasons or farming phases had any effects on the microalgae assemblage variation. The sampling year, however, presented influence on the assemblage structure, and 2021 presented a different phytoplanktonic assemblage when compared to 2019 and 2020. The probable main driver for this variation is the substitution of shrimp farming to rice cultivation in the sampling regions.