Patterns in macroinvertebrate assemblages at different spatial scales. Implications of hydrological connectivity in a large floodplain river.

ZILLI FLORENCIA; MARCHESE MERCEDES ROSA

HYDROBIOLOGIA

SPRINGER

Año: 2011 vol. 663 p. 245 - 257

0018-8158

The habitat heterogeneity generated andsustained by the connectivity of floodplain habitats,the seasonal flood pulse, and the variability of thephysical structures typically found in floodplains oflarge rivers results in a variable space?time mosaic ofwater sources that results in a high biodiversity of theriver-floodplain system. In order to assess the implicationsof natural connectivity and the heterogeneityon the patterns of macroinvertebrate assemblages atdifferent spatial scales, monthly samplings in sixdifferent mesohabitats (lakes with different hydrologicalconnection and secondary channels with permanentlyand intermittent flow) of the Parana´ Riverfloodplain were performed from April 2005 to March2006. The mesohabitats had different granulometryand detritus composition of their bottom sediments.They also had different conductivity, transparency,and depth in relation to the different connectivitydegrees. Mesohabitats differed in the abundance ofmacroinvertebrates of different taxonomic groups anddiversity. The environmental variables were correlatedto the patterns of macroinvertebrate abundance, withdominance of different species of annelids and mollusksat the patch, mesohabitats, and island scales. Analpha diversity gradient from the isolated lake (65taxonomic units) to the secondary channels (25taxonomic units) was obtained. The analyzed mesohabitatsshowed a high taxa turnover, with high valuesnot only among the mesohabitats located in thedifferent islands, but also among the mesohabitats inrelation to different connectivity degrees. The mesohabitatsshowed negative co-occurrence of macroinvertebrateassemblages. The spatial heterogeneity,sustained by the connectivity degree, played a key rolein structuring benthic assemblages at different scales,positively influencing the regional diversity.