Evaluation of coastal waters receiving fish processing waste: Lota Bay as a case study

Liquid wastes from the fish meal and oil processing industries produce serious environmental impacts in coastal embayments on the coasts of Chile and Peru. This article presents an analysis of an environmental monitoring program at Lota Bay, a shallow coastal indentation in central Chile (37 degrees S) exposed to industrial fishing activity. The study of the environmental impact produced by waste effluents permitted making an evaluation of the bay's capacity for seasonal recovery from this impact. Seasonal cruises were carried out during 1994 and in 1996, 1997, and 1998. Variables analyzed included salinity, temperature, dissolved oxygen, ammonium concentration and surface oil and grease. The hydrographic regime of Lota Bay follows a seasonal pattern, where, typical of most SE pacific embayments, waters from subsuperficial oxygen minimum zones moved into the bay. The percentages of dissolved oxygen were critical in the area of organic waste discharge. The impact of wastewater is related to the type and status of the fishery, including: (i) overloads of plant production lines, (ii) maintenance and cleaning of installations, and (iii) degree of shipboard fishing conservation. Major alterations were observed in summer, when the highest discharge of organic load occurred. In winter, an improvement in the re-aeration conditions reduced the impact. Remedial measures implemented beginning in 1997 arose from the monitoring program and had to be separated into two recovery factors including (a) internal management of plants and (b) treatment of plant effluents.