Dinocysts as proxy of primary productivity in mid–high latitudes of the Northern Hemisphere

Abstract

In order to explore the potential of dinocyst assemblages in marine sediment as a proxy for primary productivity, we analyzed a reference “modern” database including 1171 sites from the North Atlantic Ocean ( n = 483), the Arctic Ocean ( n = 401) and the North Pacific Ocean ( n = 287). We compiled two sets of primary productivity data derived from satellite observations: (1) The dataset from the Coastal Zone Color Scanner (CZCS) program applied to observations from 1978 to 1989 and (2) the data set from the MODerate resolution Imaging Spectroradiometer (MODIS) program using observations from 2002 to 2005. We performed canonical correspondence analysis (CCA) on a data matrix that included 62 dinocyst taxa and eight sea-surface parameters (winter and summer salinity, winter and summer temperature, sea-ice cover, summer, winter and annual primary productivity). CCA results show that primary productivity is a determinant parameter of dinocyst assemblages (including both phototrophic and heterotrophic taxa) in the North Atlantic, North Pacific, and at hemispheric scale. In the North Pacific, the relationship between productivity and dinocyst assemblages is particularly strong. We tested the modern analogue technique to reconstruct productivity using the North Atlantic, North Pacific, Arctic and hemispheric dinocyst data sets. With the exception of the Arctic Ocean alone, which is characterized by overall low productivity, productivity can be estimated with an accuracy (Root Mean Square Error = RMSE) of ± 11–25%. The best performance is obtained for reconstruction of winter productivity from the MODIS data. It is noteworthy that the RMSE for all estimated productivity parameters is narrower than the mean differences between productivity data derived from the MODIS and CZCS data sets. Therefore, we conclude that dinocysts can be used to reconstruct productivity with an accuracy equivalent to that of primary productivity estimated from satellite observations. Application of the approach in a sedimentary core from the northwest North Atlantic (core HU 91-045-094) revealed large amplitude variations of productivity over the last 25,000 years. The use of both MODIS and CZCS datasets indicate generally low productivity during the glacial stage, the Younger Dryas and Heinrich events, with annual productivity of less than 100 gC m − 2 . The reconstructions also suggest higher productivity during the early Holocene, especially based on the MODIS data that suggest annual values of up to 350 gC m − 2 .