Abstract
The microplankton community was studied at 9 sites (29 sampling stations) along the Salento Peninsula (SE Italy). Integrated samplings from both the water column (to collect active stages), and sediments (to collect resting stages), were carried out. More than 400 taxa were recognised in total. As for phytoplankton, 64 taxa were new records from the area. In particular, 16 of them were found only as resting stages in the sediments. A harbour, a coastal lake, and a submerged cave were investigated to understand the role of confined or sheltered environments in the accumulation of resting stages. The harbour and the lake were found to be biodiversity reservoirs, due to the abundance of resting stages in their sediments. Only few species were found both in the water column, as plankton, and in the sediments, as resting stages. Furthermore, the most abundant species in the water column were not equally dominant as resting stages in the sediments. This suggests that species other than those observed in the plankton during the present work (i.e., those found as dominant among resting stages in the sediments) dominated the plankton in the past. Furthermore, they could dominate the future plankton, with multiannual cycles, starting from sediment reservoirs. The search for resting stages in the sediment, thus, is useful to discover temporarily rare species, because species persist in the sediments as resting stages for longer periods than those spent as active stages in the plankton.
Highlights
Coastal marine microplankton is composed of species with short life cycles, strongly affected by seasonal fluctuations in abiotic conditions
(135,000 cells l-1) at T03 harbour, as “other phytoplankton” did (15,000 cells l-1), while coccolithophorids were most abundant in March (67,000 cells l-1) at T15 B
TABLE 2. – List of phytoplankton taxa/categories collected in the water column during the four oceanographic surveys (M=March, J=June, S=September, D=December 2000)
Summary
Coastal marine microplankton (both phyto- and zooplankton) is composed of species with short life cycles, strongly affected by seasonal fluctuations in abiotic conditions (see Krsinic, 1998, for SouthAdriatic area). An extreme case is the complete disappearance of species from the water column, with suspension of active life for long periods (from a single season to many years; Boero, 1994; Giangrande et al, 1994). During these periods, species are not in the water column but they are “elsewhere”. (generally in the sediments) as lethargic, or encysted forms. Such a habitat shift represents a still underestimated transfer of living matter from pelagos to benthos (Boero et al, 1996). Such a habitat shift represents a still underestimated transfer of living matter from pelagos to benthos (Boero et al, 1996). Dale’s (1983)
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