T2a

Th activity, k is the decay constant of Th (=0.0288 day-1), P is the net removal flux of 234ThP, and V is the sum of the advective/diffusive fluxes (Savoye et al. 2006 and references therein). Measurements of both dissolved and particulate 234Th allow us to calculate rates of exchange between dissolved and particulate phases, removal fluxes and particle residence times. By assuming steady state and negligible advective/ diffusive terms, particulate 234Th flux, P, must balance the measured deficit relative to AU. Particle residence times with respect to removal from surface layer are given by the ratio 234ThP/P.

Results

Hydrography, Phaeocystis and DMSP distribution in the three fjords

The differences in temperature, salinity and density indicated no major exchange of water masses throughout the cruise. Salinity was lowest in Balsfjord (33.5-33.7), and highest in Ullsfjord (34.2-34.5) (Reigstad et al. 2000).

The development of the Phaeocystis bloom was different between the three fjords (Fig. 2). The lowest cell numbers were observed in Balsfjord, with contributions of Phaeocystis cells to total phytoplankton cells of less than 12% throughout the study period; diatoms dominated in Balsfjord. On the other hand, Ullsfjord, with open access to coastal waters, presented a well-developed vernal bloom, with the highest Phaeocystis abundances; this alga dominated the phytoplankton community (in numbers of cells) in April. The abundance of Phaeocystis in Malangen fjord waters was relatively low and intermediate between the two other fjords.

DMSP in surface waters, produced primarily by Phaeocystis, paralleled the distribution of this a

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