Humans can have a significant impact of the biology of the ocean where
we alter its chemical composition. Some of the ways human activities
influence ocean chemistry are explained below, including sewage and
trash, storm drain and river run-off, and oil spills.
Sewage and trash- All over the world (including the USA),
sewage and trash
are dumped into the sea. This ranges from raw, untreated sewage, to
partially treated sewage. Chemically, sewage acts like fertilizer and can
be responsible for toxic plankton blooms. Another possible effect is
deoxification which kills marine life because there is not
enough oxygen in
the water to breathe.
Sewage may also introduce diseases and unhealthy chemicals like heavy
metals and carcinogens into coastal waters. Although the ocean is good at
ridding itself of pollutants by chemical processes and dilution, as coastal
populations grow, so do the human impacts on the marine environment.
Storm Drain and River Run-off- These sources of marine
pollution may begin
far away from the coast. The term for this is non-point source
What goes down the gutter in your neighborhood? Looking out my window, I
see a styrofoam coffee cup, oil and gasoline, soap from washing cars, a
candy wrapper, water from fertilized lawns, cigarette butts, and some dog
Fertilizers, soap, and organic wastes will increase plankton and bacteria
levels in the ocean the same way sewage does. Oil and gasoline are toxic in
both freshwater and saltwater. Debris like trash can entangle or be eaten
by birds, fish and mammals which can be very harmful (and it looks
Oil spills- Yuck! Pictures of birds and seals covered with oil
themselves for this human impact. Oil floats on the surface of sea water,
so when oil spills occur, the oil tends to end up on the shore where it
negatively impacts coastal wildlife and humans. It can hurt wildlife by
matting down bird feathers, sticking to fish gills, disrupting breeding, and
by poisoning animals and plants. Humans are affected when beaches are
closed and seafood cannot be harvested.
Once an oil spill occurs, chemicals can be used to disperse the oil, but
these chemicals may also be toxic to marine life. To clean up a spill with
minimum impact to the environment, bioremediation may be used.
process, nitrogen and phosphorous-rich fertilizers are added to contaminated
beaches to promote the growth of bacteria that essentially "eat" the
This completes The Chemistry of Human Impacts on the Sea
Return to the beginning of the Ocean