Biogenic particles and nano/picoplankton in water masses over the Scotia-Weddell Sea Confluence, Antarctica

We studied the particle composition in the ocean surface layer (20–100 m), in terms of non-living versus living particles (< 20 μm), along a transect over the Scotia Sea/Weddell Sea transition. The data are related to characteristics of the phytoplankton community and used in a Principal Component Analysis to differentiate between water masses. There was a striking change in particle community characteristics from Scotia Sea to Weddell Sea waters, especially clear at shallow depths (20 m). Total particle concentration decreased greatly moving south over the Confluence but the proportion of living particles increased enormously. This paralleled a change in the composition of the phytoplankton community, from a bloom to a regenerating system, with a striking reduction in the prominence of non-living particles. Densities of auto- and heterotrophic nanoflagellates and bacteria reached maximal values towards the southern end of the transect (8.0 × 103cm−3,4.6 × 103cm−3,1.0 × 106cm−3). The PCA based on particle characteristics and chlorophyll a, POC and PON values, distinguished Scotia from Weddell Sea waters and separated shallow from deeper stations.