The isotopic signature of planktonic foraminifera from NE Atlantic surfacesediments: implications for the reconstruction of past oceanic conditions

The stable isotope compositions of the planktonic foraminifera Globigerina bulloides, Globigerinoides ruber (white and pink varieties), Globigerinoide s trilobus, Globorotalia inflata and Globorotalia truncatulinoides (right- and left-coiling types) were examined as recorders of North Atlantic surfac e water properties based on 40 box-core surface sediments between 60 degree s and 30 degrees N. While G. ruber(while and pink varieties) and G. trilobu s mainly reflect summer surface water conditions in their oxygen isotope co mposition, G. bulloides reflects temperatures of the northward-migrating sp ring bloom, February-Mal ch in the south to May-June in the north. Our data show that G. bulloides cannot be regarded as an indicator for summer tempe ratures as deduced from Duplessy et al.'s data. Gt. inflata and Gt. truncat ulinoides (right- and left-coiling) build their shells in the coldest water s compared with the other species and reflect temperatures between 100 and 400 m water depth. The difference in oxygen isotope composition between G. bulloides and G. inflata serves as a proxy for water mass stratification. G . bulloides is the only species that gives a distinct pattern in its carbon isotopic composition showing a high correlation with the surface water pho sphate values along the transect and may serve as a proxy for palaeonutrien ts and/or productivity.