Distribution and Geochemical Composition of Living Planktonic Foraminifera in the Caribbean Sea

Thursday, 18 December 2014
Anna Jentzen, Joachim Schönfeld and Dirk Nuernberg, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Planktonic foraminifera are widely used for paleoceanographic reconstructions of different water mass dynamics. For accurate reconstruction, it is crucial to understand the habitat, ecology and shell chemistry of single species. In this study, living planktonic foraminifera were collected with a multi closing net in the Caribbean Sea during R/V Meteor cruises M78/1 in 2009, and M94, M95 in 2013 respectively. The population structure in surface to subsurface waters was assessed and related to salinity, temperature and chlorophyll concentrations. Stable isotopes and trace elements of shell calcite are measured to improve the proxy calibration. At all stations, the highest standing stock was observed in the near-surface layer and the highest population densities in the eastern Caribbean Sea. Markedly low abundances of foraminifera were recognized in Gulf of Paria and close to the Orinoco River plume. The most frequent species in the Caribbean were Globigerinoides sacculifer, Globigerinita glutinata, Globigerinoides ruber, Globigerinella calida, and Neogloboquadrina dutertrei. Abundance maxima of G. sacculifer and G. ruber were always recorded in the surface water. The preferred habitat of N. dutertrei was the near-surface mixed layer, even though the species has been commonly referred to calcify in the thermocline. As expected, the deep dweller Globorotalia truncatulinoides (dextral) was mainly observed in upper intermediate waters, although juvenile specimens were found at shallower depths. Plankton tow data showed that shallow-living species adjusted their habitat to surface water masses, which deepened in the southern Caribbean Sea from East to West. Furthermore, intermediate to deep dwellers appear to prevail in surface or subsurface waters during the early stage of their life cycle.