ECOSYSTEM MODELS OF SCOTTISH SEA LOCHS FOR ASSESSING THE IMPACT OF NUTRIENT ENRICHMENT

A previously published model is used to assess the effects of potential disturbances on a sea-loch ecosystem. Nutrient enrichment on its own has little or no effect, and the only major consequence of enhanced or depressed Light conditions is a phase shift in the spring bloom. For the fjordic systems modelled, the most important type of disturbance is a reduction in grazing, which can result in high levels of phytoplankton biomass for much of the year. In the absence of grazing control, primary production in these systems becomes nutrient-limited, and it is concluded that the most serious threat would be posed by a reduction in grazing rate combined with an increase in nutrient loading. © 1993 Conseil International pour l’Exploration de la Mer.