Short term dynamics of planktonic foraminiferal sedimentation in the Porcupine Seabight

Modern planktonic foraminifera collected with a sediment trap, and subfossil assemblages from surface sediments from the Galway Mound in the Porcupine Seabight off southwestern Ireland, (northeastern Atlantic), were studied in order to investigate recent assemblage variations. The sediment trap operated from April to August 2004 with a sampling interval of eight days and covered the spring bloom and early summer. Ten different species were recorded. Globorotalia hirsuta, Turborotalita quinqueloba and Globigerinita glutinata appeared predominately in spring. Neogloboquadrina incompta, Globigerina bulloides and Globorotalia inflata were abundant in spring and summer. Highest foraminiferal tests flux occurred in June. The faunal composition was similar to subfossil assemblages from surface sediments, but the species proportions were different. This contrast was mainly driven by the subtropical species G. hirsuta, which was frequent in 2004 but rare in surface sediment samples and in earlier plankton collections obtained from the southern Porcupine Seabight during the 1990s. The individual weight of deposited foraminifera is mainly influenced by the spring bloom, as indicated by sea-surface chlorophyll-a data. The top three-ranked species, G. hirsuta, N. incompta and G. bulloides, contributed 87 % to the foraminiferal carbonate flux at Galway Mound