The hydrography and phytoplankton ecology of Loch Ardbhair: A small sea-loch on the west coast of Scotland

The hydrography and phytoplankton ecology of Loch Ardbhair, a small sea-loch on the northwestern coast of Scotland, was studied between January 1981 and July 1982. Tidal exchange was the dominant hydrographie feature of the loch and the exchange time was estimated to be between 1 and 2 days. In 1981 seasonal changes in phytoplankton biomass and species succession were similar to other sea-lochs, although the spring peak, and summer levels of, phytoplankton biomass (3.0 and 1.0 mg chlorophyll · m^-3 respectively) were lower than might have been predicted from winter levels of nitrate. Chlorophyll levels in Ardbhair were much higher in July 1982 (up to 3.5 mg · m^-3) compared to July 1981 (0.7 mg · m^-3) and the phytoplankton was dominated by dinoflagellates rather than microflagellates and diatoms. It is suggested that rapid exchange limits in situ growth of phytoplankton in Ardbhair and that phytoplankton biomass and species composition in Ardbhair closely resembles that of Eddrachillis Bay with which the loch exchanges. The importance of these results concerning the risk, to loch-based fish farms, from ichthyotoxic blooms is discussed.