Taxonomic diversity and structure of the molluscan fauna in Oualidia lagoon (Moroccan Atlantic coast)

Abstract

The spatial distribution of the molluscan fauna of Oualidia lagoon (Moroccan Atlantic coast) was studied during winter 2013. Samples were collected from 43 stations over the whole of the lagoon. Twenty-eight taxa (19 species of gastropods, 7 species of bivalves, 1 species of polyplacophora, and 1 species of cephalopod) were listed, 21 of which are newly reported for Oualidia lagoon. Four taxa, Hydrobia sp. (78.29%), followed by Abra alba (13.99 ), Nassarius pfeifferi (5.07%), and Cerastoderma edule (1.32%), were accounted for 98% of the total abundance. A classification analysis used to characterize the lagoon on the basis of molluscs showed the existence of three main clusters from downstream to upstream: a Nassarius pfeifferi community, a Hydrobia sp.-Abra alba community and a Hydrobia sp.-Cerastoderma edule community.

Macrofaunal spatial distribution and community structure in a lagoon without a river discharge (the Oualidia lagoon, NW Morocco)

“…In this study, environmental variables did not all vary as gradients (gradual variations) between up‐ and downstream areas. Only salinity and temperature showed obvious decreasing and increasing gradients, respectively, towards upstream in accordance with the statement of El Asri et al (). Both salinity and temperature gradients resulted from the ocean‐continent gradient correlated with the position of stations across the lagoon.…”

“…This species is promoted by the amount of particulate organic matter, but it could be also encountered on bare sediments with decreasing salinities and increasing temperatures (negative and positive correlations, respectively). The lower and upper parts of the lagoon supported low diversity with respect to the middle section as it was stated by El Asri et al (, ). This might be due to the decreased heterogeneity of habitats available and the unconstancy of abiotic factors.…”

“…The inconspicuous environmental gradients particularly those of OMC and silt content are mainly influenced by the pronounced seawater renewal and the lack of significant fluvial inputs (direct freshwater sources). Moreover, sediment and salinity distributions in this lagoon were typical of estuarine systems (El Asri et al, , , ; Zourarah et al, ).…”

“…Both salinity and temperature gradients resulted from the ocean‐continent gradient correlated with the position of stations across the lagoon. Moreover, El Asri et al () imputed the former to several underground freshwater sources located in the upstream region and the latter to the influence of the cold ocean waters at the lagoon entrance and the decreased depth upstream, which promotes the fast warming of waters. General decreasing trends of the median grain size and pH and increasing trends of organic enrichment and silt content were detected with the increasing distance from the lagoon entrance.…”

“…Apart from studies of Azirar and Bayed (), Chbicheb (), El Asri, Zidane, Maanan, Tamsouri, and Errhif (), and El Asri et al (), macrozoobenthic communities of this transitional water system are scarcely studied and warrant further research. Here, we attempt to contribute towards filling this gap in our current knowledge through a baseline study conducted on the intertidal soft‐bottom‐inhabiting macrofauna of the Oualidia lagoon.…”