Benthic foraminifera and brachiopods from a marine cave in Spain: environmental significance

Sediment samples from a marine cave of the Murcia region (Eastern Spain) were analysed for grain size, total benthic Foraminifera and dead Brachiopoda, obtaining environmental information through physical and ecological data, in order to improve the knowledge about the benthic communities of cave environments and their ecological significance. A total of 100 foraminiferal and 7 brachiopod species were classified, highlighting the first occurrence in the Western Mediterranean of Gwynia capsula (Jeffreys, 1859). Statistical analysis, applied to foraminiferal data, allowed the identification of three assemblages characterized by decreasing species diversity along the cave, corresponding to the same separation recognizable through changes of brachiopod species abundance and well-fitting with cave morphology. The relative abundance of epifaunal clinging-attached foraminifera and the rate between cave and sciaphilic/coralligenous Brachiopoda, considered as representative of degree of separation from marine conditions, were found highly correlated, increasing towards the inner cave. Our hypothesis was that, in spite of different lifestyle of these two groups, the strict correlation of environmental factors (i.e. light, nutrients, sediment texture, water parameters) changing along the cave, determine a comprehensive environmental gradient causing the increase of environmental stress, with similar effects on the different taxonomic groups.