Dinoflagellate cyst distribution in surface sediments from the Arabian Sea (northwestern Indian Ocean) in relation to temperature and salinity gradients in the upper water column

Surface sediment samples from the Arabian Sea (Indian Ocean) have been investigated for their dinoftagellate cyst content. To obtain information about the environmental affinity and potential palaeo-environmental significance of the cyst species, their distribution is compared with the environmental characteristics of the overlying water column. Using detrended correspondence analysis and canonical correspondence analysis, the distribution patterns of individual species are compared with temperature and salinity gradients over four seasons. The main variation in cyst association appears to be related to variation in those gradients affected by the SW and NE monsoons. On the basis of this relationship four groups of species can be recognised: (1) central Arabian Sea species; (2) SW monsoon upwelling species; (3) NE monsoon eutrophic species; (4) species with no distinct relationship with monsoon-related gradients. The downcore occurrences of species from groups 1, 2 and 3 have potential as indicators for palaeo SW and NE monsoon strength.