Intertidal meiofauna communities along an estuarine gradient in a protected area (Ria de Foz, north-west Spain)

The northern Galician rias provide important economic and social services from fisheries, shellfish harvesting and recreational activities. Consequently, these rias have been included in the Nature 2000 Network as a Special Conservation Zone. The aims of this study were to describe the meiofauna spatial structure in terms of diversity and abundance of major taxa, as well as its relationship with the environmental characteristics in the Ria de Foz nature reserve. For this aim, environmental gradients and distribution patterns of intertidal meiobenthic communities at the Ria de Foz nature reserve were studied using multivariate methods. Ria de Foz showed to be a complex transitional habitat with significant changes in its environment along the estuarine gradient. An abundant and rich meiofauna community was reported at Ria de Foz. A total of 21 higher taxa of meiofauna were found. The most common taxa were nematodes, copepods, ostracods and turbellarians. Three clear different meiobenthic communities were defined. These three communities showed a clear spatial distribution pattern along the estuarine gradient. Moreover, a high degree of similarity between distribution patterns of meiobenthic communities and previously studied macrobenthic communities was found. Regarding the role of environmental factors shaping meiobenthic community distribution patterns distance to the river mouth was the environmental variable that best explained meiobenthic community structure and distribution. Therefore, changes on hydrodynamics that affect environmental factors related to the estuarine gradient will change the distribution pattern and diversity of benthic communities. This work provides the first information about meiobenthos diversity and structure in the Ria de Foz nature reserve and should be useful for future management and conservation plans on this and other similar protected areas.