August 13, 2007
By Syed Akbar
Hyderabad, Aug 12: After playing havoc on land, pollution has now extended its fangs to the sea, killing scores of oceanic species including fish. Water quality in the entire sea coast in the State from Srikakulam to Nellore districts, particularly between Visakhapatnam and Kakinada, is badly affected upsetting the delicate marine ecology.
According to a study by the National Institute of Oceanography and a report by the city-based Environment Protection Training and Research Institute, the impact of anthropogenic or human interference, agricultural effluents and industrial wastes have led to deterioration of water quality, causing mass mortality of fish due to asphyxiation. It has also caused harmful plankton to grow in large numbers reducing the oxygen content in sea water.
"The coastal environment is being altered at ever-increasing rates, often without looking ahead at future consequences. This is due to a multitude of human activities. The coastal zone receives a vast quantity of sewage waste, dredge spoils, industrial effluents and river runoff. These markedly affect the composition and quality of coastal environment, causing marine pollution," points out the EPTRI report.
Bay of Bengal has a unique feature in that its water is always balanced. But pollution along the coast has affected even this well-balanced system. The total precipitation over the bay which exceeds evaporation by about 1500 cubic metres and the discharge of over 2000 cubic km of fresh water per annum from major river systems from the adjoining countries lead to a positive water balance in the Bay of Bengal.
Visakhapatnam harbour and Kakinada Bay are emerging as hotspot areas in the Andhra coast. Besides industrial and domestic wastes, port-related operations in Visakhapatnam and Kakinada and intensive aqua culture along the coast are the potential sources of coastal pollution.
Industrial units discharge effluents to the extent of 77.76 crore metres cube per day into inner harbour in Visakhaptnam along with a part of the domestic sewage (2.43 crore metres cube per day).
The land-locked nature of inner harbour its connection to the open sea through entrance channel and the outer harbour, inhibits to a significant extent, the circulation and tidal flushing of anthropogenic inputs into the open sea.
Some of the important observations in the studies include mass mortality of fish believed to be due to asphyxiation, periodic outbursts of blooms (harmful plankton) and near eutrophication conditions due to accumulation of high levels of nutrients and organic matter compiled with inadequate tidal flushing.
In addition, high levels of chlorophyll, primary production, particulate organic carbon, dissolved and particulate trace metals were observed in inner Vizag harbour. Rapid changes in composition and taxonomic diversity of phytoplankton, species diversity and zoonplankton and benthic fauna abundance, high pollution load indices were also reported in the inner harbour.
There were periodic outbursts of phytoplakton, notably Skelatonama Costatum and other species, leading to high values of chlorophyll and dissolved oxygen. Benthic conditions have also changed and only certain pollution tolerant species (Capitalla capitata) inhabited the bottom sediments that contained a heavy load of organic matter.
According to the report, increased pollution in the harbour led to the disappearance of stenoecious species and their replacement with other forms known for their tolerance to pollution.
Pollution load index in terms of trace metals in the inner channels of Visakhapatnam harbour are considered to be highly polluted while Kakinada bay is considered to be moderately polluted zone. Visakhaptnam region is dominated by industrial and domestic discharges while the Godavari and Kalingapatnam regions are influenced by agriculture and anthropogenic inputs from the adjacent river runoff.
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