Vernal sedimentation trends in north Norwegian fjords:Temporary anomaly in 234 Th particulate fluxes related to Phaeocystis pouchetii proliferation

• Main Authors: Schmidt, Sabine, Belviso, Sauveur, Wassmann, Paul, Thouzeau, Gérard, Stefels, Jacqueline
• Format: Book Part
• Language: English
• Published: Springer Netherlands 2007
• Subjects: Th; fjord; Northern Norwegian shelf waters; Particle flux; Phaeocystis; Sediment trap; Balsfjord; Malangen; Norway; Northern Norway
• Online Access: https://hdl.handle.net/11370/c60c0f6b-746d-4ff7-b454-e99181f93849; https://research.rug.nl/en/publications/c60c0f6b-746d-4ff7-b454-e99181f93849; https://doi.org/10.1007/978-1-4020-6214-8_17; http://www.scopus.com/inward/record.url?scp=84892227339&partnerID=8YFLogxK

We report data of a naturally occurring radionuclide, 234 Th, an in situ tracer, to investigate vertical export of biogenic matter during a vernal bloom of Phaeocystis pouchetii in the fjords of northern Norway. To optimise sampling of different stages of the bloom, three fjords with increasing oceanic influence (Balsfjord, Malangen fjord and Ullsfjord, respectively) were investigated in April 1997. Contrasting situations were encountered between the three fjords: the proliferation of P. pouchetii in Ullsfjord surface waters coincided with a drastic reduction of particulate 234 Th fluxes in traps, although particulate organic carbon (POC) and dimethylsulphoniopropionate (DMSP) were exported and 234 Th was available in surface waters. When large colonies make up a significant fraction of the vertical flux, as observed in Ullsfjord in April 1997, there may be a large and rapid change in the POC/ 234 Th ratio, further complicating the use of 234 Th as a tracer for POC export. The results suggest that the proliferation of Phaeocystis pouchetii during vernal bloom could temporary increase OC/ 234 Th ratio of particles and delay the particulate export of 234 Th, and probably of other particle-reactive species, from surface waters.