Water pollution effects on marine life are a trending issue in terms of environmental concerns. Water pollution affects humans. It affects terrestrial organisms. It affects marine organisms. Today’s post focuses on the impact of water pollution on marine organisms including sharks. Although Twitter is rife with comments slamming the scientific integrity of Discovery Channel’s Shark Week, I have enjoyed their footage of these ancient creatures 😳 and just try to keep perspective. They are bringing some positive publicity to these creatures at least 😉
How Water Pollution Affects Marine Life
Marine organisms are affected by pollution in many ways but the most profound, long-term damage comes from the bioaccumulation of toxins such as metals, pesticides, herbicides and pharmaceuticals that make their way to the ocean.
Bioaccumulation – a general term for the accumulation of substances, such as pesticides (ddt is an example), methylmercury, or other organic chemicals in an organism or part of an organism.–biology online
Most of these toxins can’t be removed from the body and are stored in organs and muscle tissue. These toxins begin in low levels in microorganisms such as plankton which filter-out these toxins. Small fish eat hundreds of these plankton also ingesting the toxin and accumulating much more. Big fish consume a large number of small fish accumulating an even larger concentration of the toxins until you reach apex predators — you get the picture!
Most marine mammals and sharks are at the top of their food chains and toxins accumulate in their fatty tissues and the breast milk of mammals. Bioaccumulation of toxins affects marine life in many ways:
- their endocrine systems (affects hormone production) may suffer damage
- young many experience deformations
- juveniles may experience growth and developmental issues including skeletal problems, weakened immunity and neurological problems
- cases of cancer in marine organisms increases
Particularly sharks and marine mammals at the top of their food chains experience heavy metal accumulation:
- cadmium constricts blood vessels, increases heart rate and kills sperm
- mercury interferes with salt secretion and kills sperm
- zinc impairs gill function
- copper increases blood pressure
Sheltered bays which are often used as breeding and mating grounds by large marine organisms have lower water exchange resulting in the accumulation of toxins to dangerous levels. DDT, mercury and organochlorines have been found in higher levels in sharks and marine mammals found in closer proximity to human populations.
Water pollution also affects marine life in more immediate ways:
- lost or abandoned fishing gear can penetrate or wrap around gills or body parts causing more immediate death or a slow, painful death due to infection or slow strangulation
- plastic wrapping straps get caught around the gills of young sharks cutting into flesh also causing slow, painful death.
Top 10 Toxic Organisms
Bob Bohle of BlueVoice.org has compiled a list of the organisms containing the highest amounts of toxins accumulated from their environments.
- Bottlenose Dolphin
- Risso’s Dolphin
- Harbor Seal
- Beluga Whale
- Mediterranean Monk Seal
We are tied to the ocean. And when we go back to the sea, whether it is to sail or to watch – we are going back from whence we came. – John F. Kennedy
- Common Dolphin
- Gray Seal
- Polar Bear
- Stellar’s Sea Eagle
Bohle, Bob. The Effects of Ocean Pollution on Marine Mammals. 2007. BlueVoice.org
Martin, R. Aiden. A Place for Sharks. 2003. Biology of Sharks and Rays at ReefQuest Centre for Shark Research. August 13, 2014.
Shark Savers. Other Threats Facing Sharks. 2014. WildAid. August 13, 2014.