TRAÇOS FUNCIONAIS FITOPLANCTÔNICOS EM TANQUES DE PEDRA: ESTRUTURA EM ECOSSISTEMAS RASOS NO SEMIÁRIDO BRASILEIRO

Abstract

The scarce availability of water is a limiting factor to the development of the rural semi-arid . The objectives of this study were to inventory the use of stone tanks by populations and identify phytoplankton functional groups and associated environmental factors . Sampling interviews, phytoplankton (density and biovolume ) and limnological variables were peformed during the rains of 2011 in 20 tanks in Cabaceiras (Paraíba, Brazil). The transparency of the water in the tanks was low (≥ 1.5m) with water ranging from slightly acidic to alkaline. Interviews indicated reducing the transmission of knowledge between generations due to new technologies and government programs implemented in the region and preference for tanks made of " hard rock" (20 % of respondents) and deep ( Zmax ≥ 5 ) (30 %). Changes in water use between generations are indicated, being among generations use associated with various activities (50 %) and lack of alternative sources of water catchments . Regarding the structure of the communities and functional groups associated with the tanks were turbid and shallow environments dominance of cyanobacteria in 50% of cases. Group M associated with toxin -producing species Microcystis sp., Dominant in tanks near the populations (n = 2) , and K groups (Aphanocapsa sp.) and S1 (Planktolyngbya limnetica) better spatially distributed between tanks. The presence of toxic cyanobacteria registers habitat conditions compatible with surrounding development of cities, identifying two tanks in density and biomass of cyanobacteria above the limit of the Brazilian law. The transmission of knowledge management among human generations may, in the short term, lead to losses in a region whose prolonged droughts are frequent addition to potentiate toxic algal blooms, which negatively affects the health of the population in times of water scarcity .