Author(s):
Alves, Ana 
; Adão, Helena ; Marques, J. C.
Date: 2008
Persistent ID: http://hdl.handle.net/10174/6538
Origin: Repositório Científico da Universidade de Évora
Subject(s): subtidal meiofauna; estuarine gradients
Description
Meiobenthos is an important benthic component of marine and estuarine
sediments. In estuarine sediments meiofauna facilitates biomineralization of organic
matter, enhancing nutrient regeneration, serves as food for a variety of higher trophic
levels and exhibits high sensitivity to environmental modification. Spatial (horizontal
and vertical) variations, temporal changes, abundance, species composition and
fluctuations of estuarine meiofauna communities are influenced by several biotic and
abiotic factors such as trophic relationships, bioturbation, oxygen, salinity, temperature
and sediment grain size characteristics.
The objective of this study was to analyse and compare the spatial distribution
of the density and composition of subtidal Meiofauna and Nematoda communities in
two southern European estuaries, exposed to different degrees of anthropogenic
stress, in Portugal: Mira, a relatively undisturbed estuary, and Mondego, a system
under sever anthropogenic impacts. Samples were collected along the salinity gradient
of the two estuaries, from freshwater (<0.5psu) to euhaline areas (>30psu). Data were
analysed in a way to describe and compare the distribution patterns of composition and
density of meiofauna taxa and Nematoda communities along the salinity gradients of
both estuaries and to identify the specific environmental factors structuring that
distribution.
In what refers to the environmental parameters, the two estuaries were
different, with the Mira estuary presenting higher proportions of silt + clay and organic
matter content and the Mondego estuary presenting higher percentage of dissolved
oxygen and phosphate concentration.
In both estuaries, meiofauna communities were characterised by the dominance
of thetaxa Nematoda, Copepoda and Polychaeta. The spatial patterns of density and
composition of both meiofauna and Nematoda communities reflected the salinity
gradient, being these assemblages structured and influenced by this natural stressor.
Besides salinity, sediment properties also influenced the communities and the
responses of the communities to both anthropogenic and natural stress could not be
easily differentiated. Nevertheless, different patterns of the trophic nematode structure
assemblages between Mira and Mondego overlapped the salinity effects and the
feeding guilds and their response could detect the anthropogenical–induced stress in
these estuaries
