Characteristics of calcareous dinoflagellate cyst assemblages in a major upwelling region (NW Africa) Spatial distribution, fluxes and ecology

Abstract

In this comparative study, surface sediment and sediment trap samples off the NW African coast were investigated to understand the ecology, spatial distribution and fluxes of calcareous dinoflagellate cysts (dinocysts). From surface sediment samples off the Moroccan coast, relative and absolute abundances of calcareous dinocysts have been calculated, and by means of well-constrained sedimentation rates dinocyst accumulation rates were determined. Relationships with environmental properties of the (sub)surface waters have been verified, reflecting the onshore-offshore variance of the environmental parameters. By investigating time-series sediment trap material from two different water depths, cyst fluxes as well as dinocysts sinking velocities through the water column were calculated, and mechanisms of transport were revealed. Seasonal and interannual variations of dinocyst fluxes were elucidated, implying relationships with passing and waning of upwelling filaments, i.e. variations in surface water turbulence and nutrient supply.