Plankton Resting Stages in the Marine Sediments of the Bay of Vlor？ (Albania)

In the frame of the INTERREG III CISM project, sediment cores were collected at 2 stations in the Gulf of Vlor？ to study the plankton resting stage assemblages. A total of 87 morphotypes were identified and produced by Dinophyta, Ciliophora, Rotifera, and Crustacea. In 22 cases, the cyst belonged to a species absent from the plankton of the same period. The most abundant resting stages were those produced by Scrippsiella species (Dinophyta). Some calcareous cysts were identified as fossil species associated with Pleistocene to Pliocene sediment, although they were also found in surface sediments and some of them successfully germinated, thus proving their modern status. Total abundance generally decreased with sediment depth at station 40, while station 45 showed distinct maxima at 3 and 8？cm below the sediment surface. The depth of peak abundance in the sediment varied with species. This paper presents the first study of the plankton resting stages in the Bay of Vlor？. The study confirmed the utility of this type of investigation for a more correct evaluation of species diversity. In addition, the varying distribution with sediment depth suggests that this field could be of some importance in determining the history of species assemblages. 1. Introduction Resting stages produced by plankton organisms in temperate seas accumulate in the bottom sediments of confined coastal areas [1]. Their assemblages represent reservoirs of biodiversity which sustain the high resilience of plankton communities, providing recruits of propagules at each return of favourable conditions, in accordance with the so-called Supply Vertical Ecology model [2]. The existence of benthic stages in the life cycles of holoplankton provides a new key for understanding the role of life cycles in the pelagic-benthic relationship in coastal waters [3, 4]. Consequently, assessments of biodiversity at marine sites should take account of the unexpressed fraction of the plankton community contained in the bottom sediments by performing integrated sampling programs [5, 6]. Despite the proven importance of resting stage banks in coastal marine ecology, the issue of “resting versus active” plankters has commonly been considered for single taxa and only rarely from the whole-community point of view. This is probably due to the great complexity (compositional, functional, and distributional) of resting stage banks. Indeed, it has been demonstrated that at any given moment the species assemblages in bottom sediments (as resting stages) are quite different from the species detectable in the water