The cross-shore distribution of plankton and particles southwest of Iceland observed with a Video Plankton Recorder

• Decaying organic matter was a very significant component.
• Diel variability in depth distribution of the copepods was not evident.
• Calanus finmarchicus stayed generally shallower than egg carrying Pseudocalanus spp.
• Jellies and fish larvae were mainly seen above ~50 m depth on the landward half of the transect.
• Populations of C. finmarchicus off the south coast may be partly retained in the region.

The high resolution distribution of plankton and particles along a transect extending from the coast and across the shelf southwest of Iceland was studied in relation to hydrographic features and chlorophyll a fluorescence in late May 2010–2013 with a Video Plankton Recorder. The different groups of plankton and particles showed distinctive distributional pattern. Decaying organic matter (marine snow) was a very significant component of the system. Calanus finmarchicus stayed generally shallower than egg carrying Pseudocalanus spp. Diel variability in depth distribution of C. finmarchicus was not evident. Ctenophores, jellies and fish larvae were most abundant above ~50 m depth. Ctenophores were relatively abundant across the whole transect, while jellies and fish larvae were mainly seen on the landward half of the transect. The data on distribution of copepods (mainly C. finmarchicus) were combined with the results of a numerical circulation model (CODE), thus obtaining an estimate of fluxes of copepods in the area. The results show that C. finmarchicus may be transported by currents both eastwards and westwards along the south coast, while retention on the bank is also possible. Based on the results of the synthesis of the distributional data and the CODE model, it is hypothesized that the populations off the south coast are at least partly self-sustained in the region.