Daily vertical migrations in the epifauna associated with Posidonia oceanica meadows

Abstract

To estimate the importance of the vertical daily migrations in the structure of the community of the epifauna associated with the leaf stratum of Posidonia oceanica, we compared to the vagil epifauna abundance in respect to the period of the day and the height of the sediment. The study was developed in the P. oceanica meadow of El Campello (Alicante, south-east Spain), during May of 1996, to a depth of 12 m, repeating the samplings in four sites to obtain a correct spatial interpretation. Three main behaviours were detected. Decapods, amphipods, isopods, mysids, ostracods and polychaetes showed a nocturnal increase in the leaf stratum of P. oceanica. By contrast, copepods showed a nocturnal decrease in the leaves and gastropods did not show any temporal change. Chaetognaths and acari did not show statistical differences because of the considerable spatial heterogeneity. These vertical migrations have an extreme importance in the configuration of the structure of the epifauna associated to P. oceanica, in addition to the diverse response of the different taxa.