Phytoplankton metacommunity predictors: which ones not to rule out in floodplain rivers

DEVERCELLI M; GIRI F; SOININEN J

Maringá

Congreso; XV Congresso Brasileiro de Limnologia; 2015

Associação Brasileira de Limnologia

Metacommunity is an appropriate framework to find out the factors that take place in phytoplankton assembly in floodplain rivers. The aim of this work is to analyse to what extent environmental, spatial and temporal predictors explain phytoplankton assembly in the system of the Middle Paraná River, and to compare their importance during different hydrological phases. Phytoplankton biovolume (um3ml-1) from 7 environments, sampled between 1974 and 2004 (n=429) were used. Variance partitioning (VP) was applied to dissect the relationships among environmental, spatial and temporal sets of variables, and to partition their explained variation. Spatial and temporal predictors were derived from the geographical positions and Julian days, respectively, by the method of principal coordinates of neighbour matrices (PCNM) with forward selection to select the significant PCO. We found that the VP analyses explained between 19 and 27 of the species variation. During drought periods, the importance of environmental filtering was lower than during flood, whereas spatial factors were more important during drought. Temporal predictors explained a similar fraction during both hydrological phases. The spatial constraint during drought could be an evidence of dispersal limitation, whereas the environmental filtering may be acting with more strength in the more homogenised scenario of flood periods. In addition, stochastic processes may be hidden in part of the spatial and unpredictable fractions but with the performed tools we are not able to discriminate its effect. The variable importance of each set of predictors evidences that the system has oscillating behaviour. We can simplify and establish a hierarchy of predictors, but we cannot dispense of any of them to understand phytoplankton assembly.