With all these pollutants, mentioned in the previous post, at the Great Barrier Reef, how are the organisms being impacted by them?
It is incredibly important to ask what the impacts of our pollution are. After all, the Reef supports, critical habitats for threatened animals like dugongs and turtles while being a nursery for juvenile fishes.
However, when the detergents, sewage and fertilisers containing a myriad of chemicals are discharged from our homes and industries into the ocean, a lethal process called eutrophication begins. Eutrophication occurs when the presence of excess nutrients leads to an algal bloom, thereby reducing water quality, water clarity and dissolved oxygen. Submerged plants will die from lack of light (McGowan et al., 2005). This in turn leads to a further drop in dissolved oxygen as decomposers will use up oxygen rapidly. Very quickly, hypoxia occurs and a dead zone is created (Gerlach, Youngblood and Messele-Wieser, 2013).
The algal bloom feeds juvenile crown-of-thorns starfish (COTS), resulting in more reaching maturity at a faster rate. COTS feed on coral and occur naturally on reefs. Under normal circumstances, COTS are important for a healthy reef as they eat corals which grow faster, thereby allowing the slower growing corals to catch up in population size. This maintains coral diversity in the reef. The algal bloom due to fertiliser pollution has led to an outbreak of COTS (Brodie, Fabricius, De’ath and Okaji, 2005).
Many farmers are resistant to change and continue to follow traditional methods of herbicide application. This leads to an overapplication of herbicides which gets washed off due to rain and floods. Herbicides are applied on farms to kill weeds by inhibiting growth pathways (Duke, 1990). However, when they are washed into the Reef, these herbicides indiscriminately inhibit the growth of non-target plants like seagrasses which are important food sources and habitats for dugongs, fishes and turtles.
While it is undeniably true that climate change is the bigger cause of coral death in the Great Barrier Reef, the impacts of our chemical pollution are most certainly not negligible. Once these pollutants reach the ocean, the reef’s delicate ecosystem will be thrown into disarray. Furthermore, it becomes incredibly difficult to clean up once our pollution has entered the wide, wide ocean. We should instead focus on cleaning up our waters that flows from land by reducing the introduction of pollutants into water systems as well as set up mechanisms to remove these pollutants. Doing so would reduce pressure on the Great Barrier Reef and give it a chance to recover.
What do you think? Is it too late to do something about the Great Barrier Reef? Should the focus be on the removal of COTS or on farmers? What can be done to convince farmers to use less chemicals like fertilisers and herbicides? Please share your thoughts in the comments below!
Reference:
Brodie, J., Fabricius, K., De’ath, G. and Okaji, K., 2005. Are increased nutrient inputs responsible for more outbreaks of crown-of-thorns starfish? An appraisal of the evidence. Marine Pollution Bulletin, 51(1-4), pp.266-278.
Duke, S., 1990. Overview of herbicide mechanisms of action. Environmental Health Perspectives, 87, pp.263-271.
Gerlach, S., Youngblood, R. and Messele-Wieser, S., 2013. Marine Pollution. Berlin: Springer Berlin.
McGowan, S., Leavitt, P., Hall, R., Anderson, N., Jeppesen, E. and Odgaard, B., 2005. Controls of algal abundance and community composition during ecosystem state change. Ecology, 86(8), pp.2200-2211.
