Pollution effects in Visakhapatnam harbour, India: An overview of 23 years of investigations and monitoring

Abstract

Visakhapatnam Harbour, a semi-enclosed water body on the east coast of India, is subject to a high degree of pollution caused by industrial and urban wastes. Studies carried out during the last twenty years or so at 6 selected stations in the harbour revealed appreciable hydrographic and biotic changes. Over the years, the concentration of nitrites (max. 5 mg/l) and phosphates (9.6 mg/l) has increased. Dissolved oxygen registered all-time-high values (max. 21.6 mg/l) caused by periodic outbursts of phytoplankton, notably,Skeletonema costatum and other species. Benthic conditions have also changed and only certain pollution-tolerant species (e.g.Capitella capitata) inhabited the bottom sediments that contained a heavy load (2.5%) of organic matter. In the harbour, increased pollution led to the disappearence of stenoecious species and their replacement with other forms known for their tolerance to pollution. The paper describes the major changes which have occurred in water quality and organisms in the harbour as a result of pollution increase during the last two decades.