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Plankton surveys

CopepodMarine Scotland Science conducts monitoring and surveillance of plankton, but especially zooplankton, abundance at a number of locations around Scotland. Weekly sample collections have been carried out off Stonehaven on the east coast of Scotland since 1997, and at Loch Ewe on the west coast since 2002.

The major feature of the regular Stonehaven sampling has been a progressive freshening of the seawater and increase in micro-flagellate phytoplankton and small copepod species since 1997. The two species of Calanus both occur off Stonehaven but at different times of year:

  • Calanus finmarchicus appears in April-June, whilst
  • Calanus helgolandicus appears in the autumn and persists through the winter months until February

Population dynamics models of Calanus finmarchicus have been developed to analyse the life-stage abundance data at Stonehaven and current analysis is relating the annual carbon production to the productivity of the zooplankton and survival of sandeel larvae. Further offshore, Marine Scotland Science has been monitoring the abundance of over-wintering Calanus finmarchicus in the deep cold bottom water of the Faroe-Shetland Channel each winter since 1998, and sporadically before then since 1993. The reason for this sampling programme is that Calanus finmarchicus appears not to be able to persist in the North Sea without annual re-stocking from ocean areas beyond the continental shelf edge. The main centre of offshore abundance which supplies the North Sea, is in the Faroe-Shetland Channel.

Since the 1960s the volume of cold bottom water in the Channel, where high concentrations of over-wintering Calanus are found, has been declining due to global climate changes. Hence the supply of Calanus for restocking the North Sea has dwindled.

The surveillance programmes provide on-going data on changes in zooplankton around Scotland in more detail than is available from the CPR. However, understanding the predator-prey links between fish and zooplankton requires more intensive, focussed investigations of a research nature.