Author(s):
Adão, Helena 
; Alves, Ana Sofia ; Patrício, Joana ; Neto, João Magalhães ; Costa, Maria José ; Marques, João Carlos
Date: 2008
Persistent ID: http://hdl.handle.net/10316/10154
Origin: Estudo Geral - Universidade de Coimbra
Subject(s): Nematodes; Salinity gradient; Subtidal sediments; Estuary; Feeding types; Portugal
Description
This study investigated the spatial distribution of subtidal nematode communities along
the salinity gradients of two Portuguese estuaries exposed to different degrees of anthropogenic
stress: the Mira and the Mondego.
The nematode communities were mainly composed of Sabatieria, Metachromadora, Daptonema,
Anoplostoma, Sphaerolaimus and Terschellingia species, closely resembling the
communities of Northern European estuaries. In both estuaries, nematode density and
community composition followed the salinity gradient, naturally establishing three
distinct estuarine sections: (i) freshwater and oligohaline – characterised by the presence of
freshwater nematodes, low nematode density and diversity; (ii) mesohaline – dominated
by Terschellingia, Sabatieria and Daptonema, with low total density and diversity; and
(iii) polyhaline and euhaline – where nematodes reached the highest density and diversity,
and Paracomesoma, Synonchiella, and Odontophora were dominant.
Despite the similarities in community composition and total nematode density, the
proportion of different nematode feeding types were remarkably different in the two
estuaries. In Mira, selective deposit feeders were dominant in the oligohaline section, while
non-selective deposit feeders were dominant in the other sections. On the contrary, in the
Mondego estuary, epigrowth-feeders and omnivores/predators were dominant in the
freshwater sections and in the euhaline sector of the southern arm.
Differences observed along each estuarine gradient were much stronger than overall
differences between the two estuaries. In the Mondego estuary, the influence of anthropogenic
stressors seemed not to be relevant in determining the nematodes’ spatial
distribution patterns, therefore suggesting that mesoscale variability responded essentially
to natural stressors, characteristic of estuarine gradients. Nevertheless, the proportion of
the different feeding types was different between the two estuaries, indicating that the
response of nematode feeding guilds is able to reflect anthropogenic-induced stress and
can be useful in assessing biological quality in transitional waters ecosystems.
