Assessing Nitrogen Carrying Capacity for Blue Hill Bay, Maine: A Management Case History

Abstract

As net-pen aquaculture in coastal waters grows, regulatory agencies must consider the potential for localized eutrophication. To avoid excessive nutrient concentrations, Maine sees value in dispersing farms over larger regions. Often, little environmental baseline information exists in these new areas on which to base a risk assessment. This case history attempts to convey the process by which a permitting decision was made using a weight-of-evidence approach. By drawing on readily available sources of information, simple models, and basic water quality monitoring data, the effect on Blue Hill Bay by an existing salmon farm was analyzed and the potential effect of a proposed net-pen aquaculture was predicted. In the process, a range of carrying capacities was developed, depending on temporal and spatial scale. The exercise has potential value to regulatory scientists and policy makers by identifying new research, monitoring, and compliance issues. In the end, the exercise demonstrates that neither aquaculture nor carrying capacity should be viewed as static and in isolation from other stressors.