Dinoflagellate cyst production on the southern Namaqua shelf of the Benguela upwelling system

Abstract

To study dinoflagellate cyst production in the southern Benguela, a sediment trap was deployed for a period of 3.5 years at a single station located downstream of the Cape Columbine upwelling cell on the southern Namaqua shelf. The cyst assemblage of surface sediments below the trap was also investigated. Twenty-nine different cyst types were recorded of which 25 were from the sediment trap, and 22 from the surface sediments. The flux of cysts followed a clear seasonal trend with an initial peak in spring followed by a major peak in autumn; with a mean flux for the entire period of deployment of 1.4 × 106 cysts m−2 day−1. Of the cysts recovered from the trap, those of heterotrophic dinoflagellates were six times more abundant than those of autotrophic dinoflagellates. The study also revealed the presence of cysts of species previously unrecorded in the plankton of the southern Benguela, specifically the toxic dinoflagellate Lingulodinium polyedrum.