An east and west coast plankton monitoring site in Scotland are compared.

The spring diatom bloom begins earlier at the Loch Ewe site on the west coast.

A higher biomass of phytoplankton, zooplankton grazers and carnivores are observed at the Loch Ewe site on the west coast.

Comparisons with other time series suggest the plankton community are responding to large scale environmental influences.

Differences at the lower trophic levels show the need for regional criteria to assess the status of the marine ecosystem.