Naturally what makes the Great Barrier Reef so large and successful is the relatively low amounts of nitrogen and phosphorus within the water. However, this is dramatically changing as runoff pesticides and fertilisers are entering the Great Barrier Reef. Over the last 150 years, the amount of nitrogen in the water coming from farm lands has doubled to over 43,000 tonnes and the amount of phosphorus tripled to over 7100.   Naturally the large increase of these two then leads to algal blooms, the lowering of water quality and the blocking of sunlight. Consequently, because the nutrient cycle doesn’t use up the nutrients, meaning they don’t dissipate, the Great Barrier Reef ecosystem is slowly but surely taking on more and more amounts of these nutrients that are inherently harmful to the ecosystem.

 

As the water goes murkier due to pollution, some of the 51% of the sunlight that does reach underwater (not reflected by clouds or water, or absorbed by the atmospheric gasses etc) will then be scattered by the new nutrients and sediments that are polluting the water.  This is due to the sediments covering the corals blocking out their means of photosynthesis as well as the pesticides and other nutrients making the water less clear resulting in it being less penetrable by light needed for photosynthesis. This process was recently expedited by floods that carried nutrients and pesticides which are being said to float in the water blocking the sunlight reaching the producers.   The percentage of sunlight that does reach the water is also lowering due to the pollutants filling up the air which in turn absorbs some of the sunlight. Although this is not a large problem at present, it is becoming increasingly worrying to some scientists. If both these problems increase it can be expected that the number of producers decreases, whereby the food source decreases for many consumers.