Distribution of dinoflagellate cysts in surface sediments of the northern North Atlantic in relation to nutrient content and productivity in surface waters

Analyses of dinoflagellate cyst assemblages from the surface sediments of 3 71 sites from the North Atlantic Ocean were performed in order to define re lationships with nitrate, phosphate, silica and productivity in the upper w ater layer. Statistical analyses reveal close links between dinocyst assemb lages and nitrate content in February that provide a measurement of nitrate availability. Amongst the taxa in the assemblages, Nematosphaeropsis labyr inthus, which positively correlates with nutrients, shows an eutrophic rela tionship, whereas Impagidinium aculeatum, Impagidinium patulum; Spiniferite s ramosus, Spiniferites mirabilis and Lingulodinium machaerophorum have a r ather oligotrophic relationship. On these grounds, transfer functions were tested using multiple regressions and the best analogue technique to recons truct nitrate content. Both methods yielded reasonable estimates and allow the reconstruction of the nitrate concentrations in February with an accura cy better than 1.45 mu mol m(-3). At the scale of the study area, there are also tenuous links between the dinocyst assemblages and productivity. Tran sfer functions were tentatively tested for the reconstruction of annual pro ductivity and yield estimates with an accuracy of about 26.5 gC m(-2) year( -1). These results demonstrate that dinocyst assemblages can be used for th e reconstruction of productivity and nitrates. (C) 2000 Elsevier Science B. V. All rights reserved.