Individual and community level responses of benthic nematodes to the environmental estuarine gradient (Sado estuary, SW coast, Portugal)

Abstract

Nematodes are among the best candidates for ecological quality assessment due to their ubiquity and sensitivity to abiotic stressors. A background knowledge of how the complex mix of environmental conditions along the Sado Estuary sections affect nematode structural and functional distribution patterns is a prerequisite to develop future bio-assessment tools. Nevertheless, there is less knowledge on how individual species respond to the environmental estuarine gradient when compared to community responses. This study represents the first seventIMCO oral presentations T3 61 data of nematode assemblages and its functional traits (Maturity index-MI, Trophic diversity index - TDI-1) and morphometric attributes (length, weight, L/W ratio and individual biomass) in the Sado Estuary, Portugal. A strong influence of oxygen, temperature, salinity, organic matter content and % of gravel on community structural organization was identified, whereas no significant differences among different estuary “sections” were found for diversity indices, abundance and functional MI, TDI-1 indices. Morphometric attributes at the nematode assemblage level were driven by temperature, while at the individual genus level they were mainly associated to salinity, depth and gravel %. Length positively responded to salinity, whereas weight and biomass of most individual genera were positively related to % of gravel and inversely to depth. Significant differences in individual morphometric parameters were found among different estuary sections, although there were no significant differences for diversity metrics and species abundance. This finding suggests that morphometric attributes at the individual genus level better represent differences in abiotic conditions, when compared to community level indicators. These results provide important evidence to support the use of morphometric attributes at the individual genus level as indicators to assess environmental status. Keywords: Nematode genera, nematode community, estuarine gradient, morphometric attributes, functional traits seventIMCO oral presentations T3