Water quality issues associated with aquaculture: A case study in mine pit lakes

Abandoned mine pit lakes in Minnesota are being used for intensive aquaculture, and this has resulted in real and perceived water-quality impacts. In current net pen aquaculture operations, metabolic wastes and uneaten food are dispersed into previously oligotrophic lakewater, resulting in increased levels of phosphorus and nitrogen, oxygen depletion, and increased deposition of organic matter. Conditions necessary for algal blooms have been infrequent due to light limitation from intensive artificial aeration and circulation. Highly emotional conflicts arose over the novel use of a few of these man-made water bodies by an industry commonly perceived to be relatively 'green' and heavily promoted by state and federal governments as a rapid growth industry. The combination of the industry's 'newness' on the regulatory scene, coupled with the current regulatory push toward antidegradation of groundwater and regulation of agriculture, necessitated consideration of carcinogenesis, Alzheimer's disease, and antibiotic resistance transfer in addition to more conventional considerations, such as eutrophication and wildlife impacts.