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Environment
Oil Spills: Perils
of Development
by VK
Joshi
The invention
of the wheel added speed to human development. It brought comfort and
convenience of transport of goods and people. One invention led to
another and today Petroleum has become an essential fuel for growth.
Despite the information about the perils of hydrocarbon gases released
by burning of fuel and increase of green house effect, routine life
remains paralyzed without petrol.
The hydrocarbon gases add to the green house effect in the atmosphere,
which in turn adds to the rise in temperatures. It is kind of
suffocating. Fortunately we are not marine organisms. The suffocation
felt by them, as a petrol tanker grounds or pipe-line carrying crude
begins to leak or leakage from any other source cuts their oxygen supply
off by a thick film of oil on the surface. They are just choked to
death. Apart from being a vital part of the eco-system, the marine fauna
is an important part of the human food chain too. While the sea surface
remains covered with an oil slick, the helplessness experienced by the
fauna (and of course flora too) must be similar to that of our faces
being covered with a plastic bag and both hands tied behind!
The demand of oil and gas is growing faster by the day and as such a
large chunk has to be imported. Most of the petroleum products including
oil are produced in the West Asian countries and transported to the rest
of the world via Indian Ocean; therefore, the Indian coasts (especially
west coast) are exposed to the hazard. As per a publication of National
Institute of Oceanography (NIO), Goa, between 1982 and 2005 there have
been 70 cases of Oil spills along the Indian coast between Gujarat and
Vishakhapatnam. Most of the spills were of crude, fuel or heavy oil,
though there were sporadic incidents of Petrol, K Oil and even lube oil
spills. Barring one incident of leakage in the pipeline of ONGC between
Jawahar Dweep and Trombay; the rest have been spills from the ships.
The data available from the NIO covers only the spills from the ships.
However, their report says that only 10% of the global incidents of oil
spills take place when an oil tanker breaks close to the shore and often
the remaining oil slicks are either due to leakages or used mud from the
off shore drilling operations slips out of control.
The world's demand for petroleum products has been estimated to go up
from 84 million barrels per day in 2005 to 116 million barrels per day
say S. Sivadas, A. Gregory and B. Ingole of N I O in the August issue of
Current Science. Due to an increase in the maritime trade, especially
the west coast of India has become more vulnerable to oil-spills say the
researchers. In case of an oil spill, the bottom dwelling organisms or
the benthic community are the worst affected.
It was on 30 May 2006, a Panamanian Ship MV Ocean Seraya carrying some
650 tonnes of fuel oil and 40 tonnes of diesel ran aground over the
rocks off Karwar coast. As the ship broke, an oil slick was formed on
the surface of the sea and it spread fast. By 2nd June it had reached
Polem beach on Goa-Karnataka border. Monsoon winds soon carried it as
far as Palolem and Canacona, 20 km on the south Goa coast.
It was this slick that prompted Sivadas et al to study the impact on the
bottom dwelling marine organisms or the benthic community, specially the
community living between the high and the low tides. They followed a
systematic method of statistical analyses to establish the diversity and
density of larger fauna. In addition with the help of various chemical
analytical techniques they also correlated the relationship between the
fauna and the sediments-the residences of the organisms! A large variety
of bottom dwelling biota was found to be present in the area studied by
them. Chemically, petroleum hydrocarbon content (PHC) values were high
in the sediments closes to the Spill site, i.e. Polem. Here lies the
catch. The spill may not affect the biota immediately, but PHC laced
sediments continue to poison the benthic community for years to come.
Marine organisms like lobsters, crabs, shrimps, krill, and barnacles,
belong to the group of aquatic insects, the crustaceans. Majority of
them are marine and an important part of the human and other marine
organism's food chain. Incidentally they are hyper-sensitive to oil
spills. As the hydrocarbon content of the sediments is continuously
released over a period of years, these are the organisms that suffer the
maximum set-back. In case the population of PHC sensitive species is
more, the long term impact of pollution is more.
After a ship MV Sea Transporter was grounded off the Goa coast, some
scientists carried out the impact of spill on the smaller bottom
dwelling (meiobenthos) organisms of the intertidal zone. The impact on
this community of organisms including foraminifera etc was so powerful
that they were wiped out. The meiobenthos incidentally form a part of
the food chain for macrobenthos. Whether sea or land one organism is
food for the other; that is why an ecological balance is important.
Hydrocarbon, no doubt is important for our growth and development but
the marine fauna is often essential for our survival.
A good feature in case of MV Sea Transporter spill was that a strong
wave action on the beach and manual cleaning operations launched by the
local administration helped to reduce the impact of PHC considerably.
The meiobenthos recovered early.
Grounding of vessels, accidents etc are normal reasons of oil spills. In
addition during routine operations like loading, discharging and
bunkering at oil terminals spills occur quite often. In case of a spill
the lighter fraction gets evaporated over a period of time while the
heavier part settles down and forms tarballs. Wind and the current drive
these balls to the beaches and they get deposited there. Their frequency
is more during the monsoon. Usually these balls last for 33 to 58 days
in the sea. However, their fate is not known on the beaches. It is
estimated that each year about 40 tonnes of tarballs are deposited along
the beaches. Tarballs and PHCs are a prolonged source of marine
pollution.
Globally the picture has improved. Despite increased consumption of
hydrocarbons the accidental oil spills have shown a decrease. Most of
spills are from the tankers. In contrast to the global scenario the
number of tanker spills/accidents has increased along the Indian coast.
Of the total spills 70% were reported from the west coast of India say
Sivadas and his co-workers. Unfortunately the majority of spills
occurred during the SW monsoon period. Based on historical data it has
been found that during monsoon shore surface currents develop an
easterly shoreward component. This makes the west coast more vulnerable
to any oil spill during the monsoon because then waves carry it straight
to the coast. Monsoon also coincides with the spawning of majority of
marine organisms and a spill ensures that the spawns never hatch.
Oil spill is bad for the marine environment. For the beaches of Goa it
is worse because apart from the marine fauna, the tarballs and oil
pollution spoils the fun for nearly two million tourists who visit Goa
each year. Tourism is one of the major employment generators in Goa. Oil
spills spell doom for the eco-system and spoil the ambience of the
beaches for which Goa is famous.
Transporting hydrocarbon products is okay, but it is time that the
government introduces a strict control about the safety measures so that
Spills due to negligence are avoided.
December 27, 2008
Image showing An oil slick
and water plants on Deal Island in Alaska's Valdez area.
under license with Gettyimages.com
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