7-4.1 Introduction

An oil spill is the release of a liquid petroleum hydrocarbon into the off shore and on shore environment due to human activity and is a form of serious pollution. Oil spills occur due to releases of crude oil from tankers, offshore platforms, drilling rigs and wells, as well as spills of refined petroleum products (such as gasoline, diesel) and their by-products, heavier fuels used by large ships such as bunker fuel, or the spill of any oily refuse or waste oil. Another significant route by which oil enters the marine environment is through natural oil seeps. Natural oil seeps generally occur with slow rate while due to human activity are sudden, high in volume and are thus catastrophic. Some of the effects of oil spills are discussed below:

7-4.2 Environmental effects of Oil Spill

1. Oil impairs a bird's ability to fly, preventing it from foraging or escaping from predators. As they preen, birds may ingest the oil on their feathers which causes irritation in the digestive tract, altering liver function, and causing kidney damage.
   
   
2. Oil penetrates into the structure of the plumage of birds and thus reduces its insulating ability and making them more vulnerable to temperature fluctuations and much less buoyant in the water. It can cause dehydration and metabolic imbalance in birds.
   
   
3. Some birds also experience changes in their hormonal balance including changes in their luteinizing protein.
   
   
4. Furred marine mammals exposed to oil spills are affected in similar ways as birds.
   
   
5. Animals can be poisoned, and may die from oil entering the lungs or liver.
   
   
6. It leads to interrupt the food chain on which fish and sea creatures depend, and on which their reproductive success is based.