Threats: Chemical Pollution

What is Chemical Pollution?
Chemical pollution occurs when unwanted chemicals are released into the environment where they can damage the ecosystem. Chemical pollution can come from many sources, including industrial discharge and runoff, sewage, spills at sea, agricultural runoff, seepage from waste disposal sites and domestic runoff.  In the past people believed that the ocean could dilute these chemicals to safe levels. Now it is understood that the chemicals do not mix evenly into the water, instead they accumulate in high concentrations in certain areas of the ocean where these dangerous chemicals are attracted to certain types of organic matter or small particles. In addition to this, the volume and variety of chemicals entering the oceans are far greater than in the past and are continually increasing over time.

How does Chemical Pollution affect cetaceans?
Sometimes the polluting chemicals accumulate around food for animals such as plankton or small fish; both the chemical and food are eaten by these tiny animals which are eaten by larger fish, which are then eaten by some of the top ocean predators: birds, sharks, humans and cetaceans. At each stage in the food-chain the amount of the toxic chemical increases (as bigger animals eat many of the small animals which ate the polluted food), resulting in the top predators being highly contaminated.

In some cases, the animals are not able to excrete or breakdown the pollutants in their bodies and the toxins are bio-accumulated (the chemical is stored in the organism in higher concentrations than in the environment). Many of these chemicals are fat-soluble and are stored in the fatty-tissue and the blubber of cetaceans. Some of the most well known fat-soluble pollutants (pesticides and PCBs) disrupt the reproductive and immune systems of animals causing big, sometimes fatal, problems for individuals and the continuation of the population itself.

One big concern is the fact that these chemicals can be passed from mother to fetus and calf through the placenta and mother’s milk respectively. In some areas a dolphin’s first calf usually does not survive past its first year as the majority of the pollutants accumulated in the mother’s blubber (the source of milk-fats) over her life, is consumed by this first calf through the milk. This toxin load is usually fatal to the calf. Subsequent calves have a higher chance of living as the milk produced after the initial calf, has fewer toxins.

In some cases whales and dolphins are so contaminated with toxic chemicals that they have to be disposed of as hazardous waste.

Level of this threat locally
The water's around Trinidad and Tobago are constantly exposed to chemicals which are washed directly off the land or are brought there by polluted rivers. Sources of this pollution include agricultural and domestic run off, industrial discharge and improperly disposed waste. More research needs to be done in this area to clarify the level of this threat.

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