Distribution of organic-walled dinoflagellate cysts in surface sediments of the southern Caribbean and the eastern tropical Pacific and its environmental implications

Abstract

Little is known about the marine palynology of the neotropical oceans. Here, we present the first comprehensive study of organic-walled dinoflagellate cyst assemblages in 52 surface marine sediment samples from the southern Caribbean (SC) and the eastern tropical Pacific (ETP) and explain how these assemblages relate to sea-surface parameters. Multivariate analyses show that of the several environmental parameters considered, sea-surface salinity (SSS), phosphate concentrations, and nitrate concentrations best explain the relative abundances and the geographic distribution of dinoflagellate cysts in the studied area. Consistent with regional differences in marine productivity, dinoflagellate cyst concentrations were markedly different in the SC (1979 ± 1053 cysts/g) and the ETP (3105 ± 1956 cysts/g). Sediments of the SC are characterized by high relative abundances of the Spiniferites spp. group, cysts of Protoceratium reticulatum, and the presence of rare dinocyst taxa. The dinocyst assemblages from the ETP are characterized by higher relative and absolute abundances of Bitectatodinium spongium, Brigantedinium spp., and Echinidinium aculeatum. This pattern is explained by the more eutrophic nature of the ETP compared to the highly saline and oligotrophic SC. Average values of the Shannon Index (H′) from the ETP are higher compared to the SC, demonstrating that dinocysts respond to the greater climatic variability that characterizes the ETP. Brigantedinium spp. abundances are negatively correlated to H′ diversity supporting its dominant character within the dinocyst community. This work fills a gap in our knowledge on modern dinocyst distribution in neotropical oceans and provides a modern reference for interpreting down core dinocyst variations and paleocenographical reconstructions in the region.