The interstitial ciliate microcommunity of a Mediterranean sandy shore under differing hydrodynamic disturbances

The species assemblages of benthic ciliates from two adjacent locations at a sandy shore of the Ligurian Sea (Italy) are examined and compared. The environmental conditions are very similar, except char one location is more exposed to hydrodynamic disturbance than the other. Sediment samples (168 sandy samples from each station) for the identification and enumeration of ciliates were collected following a multifactorial sampling design under three different conditions: (1) a moderately perturbed spring-summer period; (2) an unusual one-month-long calm in spring; (3) an autumn-winter period. Both stations showed a rich and well-structured ciliate microcommunity. During the spring-summer period, characterized by highest ciliate density, 42 species, belonging to 27 genera, and 33 species belonging to 18 genera were found at the sheltered and exposed station, respectively. During this period, the exposed station harbours only a sub-set of the ciliate assemblage living in the sheltered one. The two ciliate communities differ significantly in abundance, species diversity, and patch frequency with the sheltered station yielding higher values. All such differences disappear after a month of calm conditions and during the autumn-winter period.