The Process of Eutrophication and Coastal Eutrophication Problem - Term Paper Example

Eutrophication Introduction Eutrophication is a complex process which occurs in both fresh and marine waters, due to excessive development if certain type of algae which disturb the aquatic ecosystems and becomes a threat for animal and human health. Its primary cause is the excessive concentration of plant nutrients which originate from agriculture and sewage treatment. Eutrophication leads to algal blooms, increased growth of macro algae, increased sedimentation and oxygen consumption, oxygen depletion in the bottom water and sometimes the death of benthic animals and fish. The Baltic Sea near Europe shows the effect of eutrophication by the presence of the harmful blue green algae dangerous for both human and marine life. The Eutrophic waters favor quickly developing plants and algae's. These long living species cannot resist competition and develop into oligo or mesotrophic waters which make these waters of less interest in terms of biodiversity and ecological quality. Thus they die of indigestion. The process of eutrophication is clearly described by the following figure; Cause High nutrients Supporting factors: - Top layers Direct effect High phytoplankton Supporting factors: - Bottom layer Indirect effect Oxygen depletion, flora/fauna changes (Eutrophication and health, WHO, 2002) The main cause of eutrophication is large input of nutrients to the water body and its effect is on imbalance of the food web which results in high levels of phytoplankton biomass in stratified water bodies. This can lead to algal blooms. The direct consequence is an excess of oxygen consumption near the bottom of the water body. Additional factors supporting this process are 1. Those depending on nutrient dispersion and the phytoplankton growth, 2. And those to the oxygen cycle near the bottom of the water body. Along with carbon, oxygen and hydrogen which plants get from water they also need nitrogen and phosphorous which are necessary for the development of aquatic life thus during eutrophication the concentration of nutrients in the water changes, phosphorous is usually a limiting factor for phytoplankton in fresh water, large marine areas have nitrogen as limiting nutrient especially in summer. Intermediate areas such as river plumes are often phosphorous limited during spring. Ecosystem disturbance: Phases of eutrophication Once eutrophication is detected in the water body it is considered sensitive under the European Union Urban waste water treatment directives and is declared nitrate pollutant according to the Nitrate directive and is an indicator of disturbed ecosystem. A healthy ecosystem is the ecosystem that functions well and is able to resist or recover from disturbance. The organization of the ecosystem refers to the food web and the biodiversity; ecosystem resistance is the non-response, up to a certain extent, of impacts such as nutrient enrichments. The ecosystem elasticity refers to the ecosystem ability to survive through the applied pressures. Although all these ecosystem characteristics contribute to the ecosystem health and integrity, they induce a non-linear response to the ecosystem which complicates the quantification of the assessment. The initial effects from eutrophication are negligible as they are below the carrying capacity: any measurable effects are less pronounced than seasonal fluctuations and therefore, any assessment seems to be uncertain. As the phenomenon of eutrophication is getting established, changes in mean nutrient and chlorophyll concentrations as well as changes in the community structure become obvious. This stage can be the early warning for the ecosystem quality. Causes Human activities are main cause of eutrophication all around the world; the three main sources are, 1. Runoff 2. Erosion and leaching from fertilized agricultural areas 3. And sewage from cities and industrial waste waters. The European Environmental agency also claims that the main source of nitrogen pollutant is run off from agricultural lands, and phosphorous pollution from household and industries. Further studied that nitrogen pollutant is gathered from; (European commission report, implementation of the nitrates directives, 2002) Few other activities which result in eutrophication are; Aquaculture development The increase in aquaculture will lead to discharge of unused animal foods and excreta of fish into the water. Transportation The transportation of foreign species by the ballast of big ships, toxic algae, cyan bacteria and nuisance weeds which carry them from widespread areas to uncontaminated ones which may become favorable habitant for them to diffuse and grow. Reservoirs in arid lands Large reservoirs are constructed to store and mange water all around the globe; they collect drainage water through huge hydrographic basins. Erosion leads to the enrichment of the waters of these reservoirs by nutrients such as phosphorus and nitrogen. Consequences of eutrophication The major consequence of eutrophication will be the oxygen availability as the oxygen will be absorbed by the bacteria and organic matter formed beneath the water body thus all life will disappear, apart from this other consequences will be; Changes in algal population Changes in zooplanktons Partly health of both human and animals would be affected by being exposed to these waters and would result in various illnesses. "Algal blooms were observed in 1638 by fishermen in north west of Iceland. Fjords were reported to be stained blood red and during the night produced a kind of phosphorescence. The fishermen thought that the colors could be due to the blood of fighting whales or to some marine insects or plants. The first scientific report of domestic animals dying from poisoning as a consequence of drinking water that was affected by a blue/green algae bloom was in 1878 in lake Alexandrina, Australia".( (Eutrophication and health, p.9 ). A few cyan bacteria produce toxins which are dangerous to human beings, people would be exposed to them consumption of contaminated drinking water, direct contact with fresh water or inhalation of aerosols. They damage cells, tissues and the organs in both animals and humans. It affects the nervous, digestive and cutaneous systems. Other symptoms may be fatigue, headache, diarrhea, vomiting, sore throat, and fever and skin irritations. The table below shows the cases of toxic cyanobacterial blooms reported in drinking water; Location and date consequences USA, 1931 No data USA, 1976 62% of population fed by the network became ill. Australia, 1979 141 hospitalizations Australia , 1981 No data Brazil, 1988 2000 people affected and 88 died Sweden, 1994 121 people affected Brazil, 1996 166 affected and 60 died The table below shows the cases of toxic cyanobacterial blooms reported in recreational water; Location and date consequences Canada, 1959 30 people affected UK 1989 20 people affected and 2 hospitalizations (Eutrophication and health, p.11) The toxins can accumulate in shellfish and seafood which are dangerous for human and animal health. The table shows the cases of intoxication due to seafood consumption Intoxication Country date Consequences Paralytic shellfish poisoning Philippine 1983 300 cases 21 deaths United Kingdom 1968 78 cases Spain 1976 63 cases France 1976 33 cases Swiss 1976 23 cases Germany 1976 19 cases Diarrhoeic shellfish poisoning Japan 1976-1982 1300 cases France 1984-1986 4000 cases Scandinavia 1984 300-400 cases Venerupin shellfish poisoning Japan 1889 81 cases , 51 deaths Japan 1941 6 cases , 5 deaths Norway 1979 70 cases Amnesic shellfish poisoning Canada 1987 153 cases, 3 deaths Neurotoxic shellfish poisoning Florida 1977 ND (Eutrophication and health, p.13) Green tides formed by microalgae proliferation are observed many times at bays, this is directly related to nitrogen enrichment of water. In the Brittany region of France many tons of macro algae are deposited on beaches every year which make recreational activities impossible and dangerous in these areas. Fishing is also affected by these algae and bacteria's, they produce compound toxic which induce fishnet clogging and resulting in breakages and losses. They disturb the ecosystem, navigation and recreational use of river and lakes. Affect on diversity of algae Phytoplankton provides the basis for the whole marine food chain. These microscopic organisms are common in coastal areas, all the way from the Polar Regions to the Equator, and multiply through cell division. If cells are present in the water mass in large numbers an algal blood develops which today is a recurrent problem in Swedish seas and along Swedish Coasts. Baltic Sea (An example) Baltic Sea is slowly destroying due to Eutrophication. The reasons are inputs from sewage treatment plants and industries, atmospheric deposition and riverine inputs including agricultural losses, atmospheric deposition, natural erosion and leakage of nutrients from areas without much human activity. Agriculture plays a role in nitrogen input; the main source of nitrogen inputs in Baltic Sea is agricultural discharge via rivers, deriving from: 1. Soil cultivation 2. Fertilizer use 3. Use of manure 4. Intensive and uncontrolled agriculture Solution The major step would be to reduce nutrients input in waters to the level that does not favor the eutrophication. Integrated management strategies should be set up which should put pressure on all water bodies to develop a coherent approach to deal with the pressures in a cost effective manner. Recommendations limit the amount of organic matters present in the water before final chlorination Ensure that there is free chlorine available at the distribution point ,chlorination itself can ensure the destruction of most of the toxins released by fresh water blue/green algae blooms and is necessary for bacteriological safety Reduce the use of chemicals based on nitrogen and phosphorus Advanced treatments of wastewaters before their discharge into the environment. All measures should be taken by local authorities in order to make such monitoring mechanisms available which allow implementation of the necessary protective measures to be taken in good time. As a consequence public health will be protected more efficiently than if waiting until a crisis occurs. Literature citation Cloern, J., Our evolving conceptual model of the coastal eutrophication problem, Mar. Ecol. Prog. Ser., 210, 223-253.[ISI], 2001 Dr Gunter Klein, Prudencio Perera, World health organization regional office for Europe, eutrophication and health, ISBN 92-894-4413-4, 2002 European commission report, Implementation of the nitrates directive, COM 407, 2002 Helcom, Andersen, J and Pawlak, J, Nutrients and Eutrophication in the Baltic Sea; Effects, Causes, Solutions. Baltic Sea Parliamentary Conference, 2006. Read More