The effects of Eutrophication Essay

The effects of Eutrophication


            Eutrophication refers to a process by which the water bodies such as rivers, estuaries streams lakes receives excess nutrients. These nutrients usually stimulate excessive plant growth i.e. the algae, water weeds, periphyton e.t.c .This excessive growth is referred to as algal bloom. The major sources of these nutrients are chemical fertilizers from agricultural practices, golf courses, suburban lawns, the deposition of nitrogen from atmosphere, soil erosion from rich organic soils, sewerage disposals. This process results to rise in several ecological effects which are discussed below

            The Coral reefs are water plants that are found in circum-tropical shallow tropical waters along the shores of continents and islands. Their substrate is composed mainly of calcium carbonate which is obtained from the living and the dead scleractinian corals. Within the corals ecosystem there lives many invertebrates, vertebrates, and plants which have a tight resource coupling and recycling, thus allows the coral reefs to have an extremely high productivity and biodiversity. They have even gone to an extent of being referred to as the tropical rainforests of the oceans.

The effects of Eutrophication on Coral reefs

            The first effect is on the individual organisms of the coral reefs ecosystem. Here In corals, the zoox coral symbiosis is interfered by through disturbed by the high levels of nutrient concentrations. For instance when these corals are kept in aquariums in presence of high ammonium concentrations for some days, the zoox usually multiples very strongly and there then the growth of corals stops. This is because the zoox depends on the energy from photosynthesis for their growth instead of giving it to the corals. Thus we can say that elevated nutrient concentrations on coral reefs ecosystem are very unfriendly.

            Secondly increase in levels of nutrients leads to space competition within the ecosystem. This is where the plants which are the primary producers (coral reefs) competes for space occupation with macro algae as their bottom surface area is very limited usually about 1 m2 . Here they all try to seek enough space to attach themselves into since they cannot grow on top of each other. Thus if there was low nutrient concentrations the corals would had otherwise been able to keep algae away and overgrow them. But for this case, the high nutrient concentration levels poses the algae to a competitive advantage thus they overgrow the corals. Since that the algae do not calcify coral reefs growth is usually reduced.

             Eutrophication on a complex ecosystem can easily lead to an increase in phytoplankton, bacteria and their consumers in the water columns. This is due to the availability of many particles in the water column and bio-eroders, e.g. the boring sponges and mussels which uses the extra food in the ecosystem. This then leads drilling of holes in the coral reefs skeleton thus weakening them if their skeletons aren’t strong enough. This finally results to their break off especially during the events of storms

            The increase in nutrient concentration has favored the aquatic life especially of fish leading to their increase in population due to availability of enough food from the phytoplankton. This has then led to continuous overfishing over time on many worldly water bodies. The reduction of fish due to overfishing on them has led to the replacement of coral reefs by the macro- algae and the sea weed since the fish that consume them are not many thus leaving these algae’s and weeds to multiply. This has also been facilitated by the various diseases that usually wipe out many sea urchins.

            Sewerage deposal to water bodies also leads to massive loss of coral reefs as this practice of deposal leads to enormous growth of macro-algae thus they over occupy the corals thus displacing them. In addition the process of eutrophication also leads to Sedimentation which might result from runoff and from artificial beaches, toxicity of chemicals in sewages, practices of overfishing, and various types of pollutions.

            There is also decrease in biodiversity i.e. of the coral reefs as the increase of nutrients in this ecosystem leads to the reaping of the ecosystem benefits by the available plants that is the corals and the micro-algae. But for this case since this process increases the amount of micro-algae’s, this favors them as there are many in numbers leading to them limiting the sunlight that reaches the bottom dwelling organisms thus even causing wide swings in amount of dissolve oxygen. This limitation result to suffocation of aquatic life. In addition other features  such as anaerobic conditions enhances growth of bacteria’s like Clostridium botulinum which produces toxins which are very harmful to the coral reefs, fish, water mammals, birds e.t.c

            Eutrophication also contributes to zooxanthellae loss but indirectly through causing secondary adverse effects for example reduction of coral resistance and susceptibility to various diseases, through its nutrient concentrations e.g. ammonia and nitrates which increases rise in densities of zooxanthellae

                Industries disposal has organic compounds such has polychlorinated biphenyls and other types of pesticides. These organic compounds and pesticide accumulate in the tissue of coral reefs then to the marine mammals when they feed the coral reefs. This result to increase in concentration of substance on sea animals by a process referred to as bioaccumulation. An example of this is at St Lawrence River which ended up draining great lakes after accumulation of large amounts of organic chlorines which amassed in the tissue of a certain type of species of coral reefs known as beluga. This effects has caused suppression of immune response to marine mammals

             Eutrophication has been observed to have positive indirect effects. Numerous growth of the coral reefs has been seen to be of  great important since they provide food and water to the wide range of aquatic life such as  fish, turtles ,manatees etc .The growth of these coral reefs and the macro algae do usually  offer habitat for sea mammals by providing not only food but also shelter.

            Coral bleaching may be the other effect that may arise; in this case the corals end up losing their colour due to changes in water chemistry. This is due to increased segmentation or an increase in turbidity which then decreases the amount of light reaching the corals reefs thus resulting to bleaching effect which in turn transforms the colour of corals to turn complexity white in colour

            To add on, the little increase of nutrients above the near zero level are very beneficial to coral reefs, as it only takes very small increases for net effect to turn negatively. This is not because the high nutrients harm corals directly, but it’s due to that corals are quickly overgrown by the quick growing algae which require higher nutrients levels than corals. Thus very little excess nutrients are required for turning the healthy coral reefs into waving fields of algae which smoother and kill corals instantly. According to various surveys it has been noted that Coral reefs go eutrophic at the very minimal levels of nutrients in any aquatic ecosystem. Therefore when nutrient levels are regarded as very low in any of the marine or freshwater habitat, this will result to dyeing of coral reefs.


            Solutions to the eutrophication problems can only be achieved through connecting households which includes all major man daily activities such as conservation activities, usage or organic manure instead of chemical fertilizers, and the industrial effluences, by calling upon them to practice the treatment of wastes before releasing them to water bodies so as to remove the present nutrients. It might seem expensive it terms of cost and time, but this is the only available best solution.

            To add on, the practices of use of secondary treated sewage water for irrigation can be an alternative towards nutrient reduction in a tertiary treatment step. Thirdly, industries through the government can be forced to live up to environmental standards policies because as long as they are present they remain sources of nutrients and toxic chemicals which pollute the water bodies.

            Finally to deal with sedimentation, basins with vegetation should be developed whereby the available sediments in the runoff can sink into before allowing the water to enter the sea. Artificial beaches should also be abolished since according to the surveys every reef in an artificial beach is seen as a desert.


 Martin C. Scholten & Edwin M. (2005). Eutrophication Management and Ecotoxicology.Published by Springer Verlag Ltd: London