Vertical distribution and cyst production of Peridiniella catenata (Dinophyceae) during a spring bloom in the Baltic Sea

Abstract

Vertical distribution and cyst production of the chain-forming, spring dinoflagellate Peridiniella catenata were studied throughout the spring season of 2000 in the coastal Gulf of Finland. Numbers of cells were monitored in the water column, and cyst sedimentation was recorded using multiple sediment traps moored at three discrete depths. At the onset of the spring bloom, most of the population was situated in the euphotic zone. When the bloom progressed, the population was more evenly dispersed throughout the water column. Coinciding with the decline of the spring bloom, after nitrogen depletion, a general reduction of cell size of P. catenata and a break-up of chains were observed. Resting cysts started to appear shortly after the peak of the bloom, in sedimentation traps moored at 30 and 40 m depth. Cysts were only retrieved from the uppermost sediment trap on three of the six sampling occasions, constituting only a small proportion of all cysts produced by P. catenata during spring. Our results suggest that cyst production of this vertically migrating organism takes place to a large extent in deep water layers and emphasizes the necessity of whole water column monitoring in studies aiming to understand in situ life-cycle transformations of vertically migrating dinoflagellates. © The Author 2006. Published by Oxford University Press. All rights reserved.