Much of the garbage that is at the roadside or thrown out of car windows is eventually washed into drains and thence to the sea. Tourism and the use of resources by locals also contribute to land based pollution, by virtue of increased populations in many coastal areas of Trinidad. In areas like Chaguaramas, a significant increase in population is causing a direct increase in the volume of sewage to the system, which is already overloaded. The old sewage systems located in this area are non-functional and result in raw or untreated sewage entering the sea. Marine organisms may be adversely affected directly by chemicals and solid wastes and as a result some species may die out.
Sewage can act as a fertilizer leading to eutrophication and prolific algal growth and red tides.
This may overwhelm marine organisms by causing oxygen depletion, or by actual physical clogging of the gills, resulting in massive fish kills, as have been documented for areas in the Gulf of Paria. The destruction of mangrove swamps and wetlands eliminates the breeding and nursery grounds of many commercially important fish and shellfish. The destruction of coral reefs, as has occurred at Buccoo in Tobago, affects the natural breeding and nursery grounds of young reef fish, such as groupers, angelfish and some sharks. Human health may be directly or indirectly affected by these contaminants. Swimming in contaminated seawater may result in similar problems as well as skin and eye infections.