This paper was written as part of the 2011 Alaska Oceans Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.

The Impact of Eutrophication on Marine Ecosystems and Its Relation to Village Life


Jacinta Matthias
Mary Okitktm
Deanna Hunt
Ariel Williams
Elizabeth Strongheart

Team LYSD's Atomic Sea Ice

Kotlik School
PO Box 20129
Kotlik, AK 99620


We probed into environmental problems and issues that have caused damages to oceanic life, such as red tides, algal blooms and eutrophication (something we never heard before) that massively kills marine organisms. We then focused this study on the impacts of eutrophication. Eutrophication is one of the main problems caused by an overuse of fertilizers and an excess of manure and sewage. These wastes enter the ecosystem and generally leach away from residential, business, and agricultural sites. The first part of eutrophication is the hyper-acceleration of aquatic life growth. The second part is their death. In the process of decay, oxygen is used up causing hypoxia (low oxygen), and eventually anoxia (depleted oxygen with toxic chemical byproducts). Consequently, mass aquatic death results in mass loss of oxygen. This further causes loss of biodiversity and the formation of oceanic dead zones. A new image of NASA (2008) reveals the extent of the world's marine dead zones found to be doubling every decade. At that time, 415 dead zones had been identified worldwide. Dead zones are regions of the oceans where dissolved oxygen has fallen to such low levels that most marine species can die, the largest dead zone recorded is in the Gulf of Mexico, about 7,000 square miles or the size of New Jersey. The consequences of eutrophication are red tides, algal bloom, water turbidity and death of dominant species. Our villages, Kotlik and Sheldon Point are apparently experiencing eutrophic conditions of the Yukon River draining down to the Bering Sea, which is our main source of subsistence. Identified major causes are the system of waste disposal and the honey bucket lagoon.


Over the last century mankind has transformed the sea from a clear-water ecosystem into a eutrophic (nutrient-rich) marine environment. Today it is highly contaminated with nutrients that cause eutrophication, algal blooms, red tides, dead zone and a range of related serious problems for the ecosystem and for the people living around and earning a living from it. Eutrophication has been silently happening all over the world and it is a big environmental issue. Algae blooms, seen in a July 2005 satellite image (Figure 1), have created the world's largest dead zones in the Baltic Sea.

Here are some fcts that marine scientists recorded as evidences of this global problem:

Fact I: In 1976, a single hypoxic event in the New York Bight that covered about 1000 km2 caused mass mortality of demersal fishes and benthos and blocked the northward migration of bluefish (Milstein, 1979).

Fact 2: Many other systems experience episodic hypoxia such as in the northern Adriatic, Pomeranian Bay, and the German Bight.

Fact 3: Low annual production and no benthic fauna due to hypoxia are realities of the Baltic Sea. Estimates of the missing biomass in Baltic dead zones that are now persistently hypoxic are about 264,000 metric tons of carbon (MTC) annually and represent about 30% of total Baltic secondary production. (Karlson, 2002)

Fact 4: In the northern Gulf of Mexico, the occurrence and extent of the severe hypoxia are tightly coupled with freshwater discharge from the Mississippi River, which delivers large quantities of nutrients from U.S. agricultural activities. During years with low river flow, the area of hypoxia shrinks to less than 5000 km2, only to increase to greater than 15,000 km2 when river flow is high. (Rabalai, 2007)

Fact 5: The Exxon Valdez oil spiII was one of the worst oil spills. It occurred because it ran off the coast of Southern Alaska on March 24, 1989, and went into the 2of water and polluted at least 1,100 km of the coastline. It also killed over 34,000 seabirds, 10,000 otters, and 16 whales. Chemical detergents were one method of removing the oil. It was used in the past, but it is a problem because it doesn't remove the oil. It just releases chemicals into the sea. The detergents contain toxic ingredient that can kill and be very dangerous to sea birds and marine life, especially fish. (Figure 2)

Fact 6: Severe algal blooms can change the seawater to various colors, often called "red tides". The water can turn: red, green, yellow, or brown. Often red tides appear throughout southeastern Asia. Figure 3)

What is eutrophication?

Eutrophication comes from the Greek meaning "well nourished". However, eutrophication can be speeded up, and the body of water and its inhabitants eventually suffer from too much nutrients causing hypoxia (low oxygen) far beyond what the natural capacity of the body of water should be. This causes death of marine life (such as fish). This does not only affect the river, but nitrates and phosphates from disposal of wastes, or natural resources [such as plants] leaches and find its way in the ocean, developing into a dead zone which spreads and increases. Apparently eutrophication is considered to be one of the largest pollution problems globally. (Figure 4)

A more complex definition of eutrophication can be described as having too much plant growth in a river or lake cuts which down oxygen causing the suffocation and death of water animals. When dead plants leaches to the bottom, they give off nutrients to help new plants boost in growth, which can block oxygen for water creatures. The main focus and concern cause of eutrophication is nitrogen and phosphorus, but nitrogen has far more attention because it often limits primary production in estuaries and coastal waters and because the global application of nitrogen from synthetic fertilizers is far greater than that of phosphorus. The phosphates and nitrates cycles are shown to explain what their purpose is. (Figure 5)

The Natural Recyclization of Phosphates

Organisms, such as the animal shown needs phosphorus to build proteins and nucleic acid. Although they may need phosphates, they also give them off when they die and decay. The phosphates are present in rocks, fossils, bones, and soil (calcium phosphates), which dissolves in water (P043-). The phosphates from decaying organisms is absorbed by roots and plants to build organic molecules. Plants that absorbed the decaying organism's phosphates is then eaten by other organisms, consequently, they reuse the organic phosphates. (Figure 6)

The Continuous Cycle of Nitrogen

The atmosphere is about 78% nitrogen gas, but, out of that 78%, many of the organisms are unable to be used in this kind of form. The atoms in a molecule of nitrogengas is connected by a very strong triple covalent bond, that is very hard to break. However, some bacteria that have enzymes can break it. They combine nitrogen atoms with hydrogen to form ammonia, also known as nitrogen fixation. The nitrogen cycle (figure 7) is a complex process with four important stages, which are: 1) assimilation—the absorption and incorporation of nitrogen into organic compounds by plants; 2) ammonification—the production of ammonia by bacteria during the decay of organic matter; 3) nutrification—the production of nitrate of ammonia; and 4) denitrification—the conversion of nitrate of nitrogen gas. The phosphorus cycle and the nitrogen cycle above are repeating processes that happen naturally but when additional man-made chemicals like nitrates and phosphates are added—the natural cycles are distorted, in effect leading to eutrophication.

The phosphorus and nitrogen cycle above occur naturally, but eutrophication have changed the cyclic process by putting more man-made chemicals affecting the environment.

The World's Dead Zones

Dead zones are caused by agricultural runoff, especially nitrogen-rich fertilizers, as well as the burning of fossil fuels. Pollutants from these sources can cause marine eutrophication, whereby the ecosystem receives too many nutrients, triggering massive algae blooms, which eventually die and are broken down bacteria. In breaking down the algae blooms, the bacteria consume excessive amounts of oxygen, starving the marine system. Therefore the largest and most extreme dead zones occur near high populations and run-off areas for agriculture fertilizers.

A new image by NASA (figure 8) reveals the extent of the world's marine dead zones, which a study in 2008 found were doubling every decade. At that time 415 dead zones had been identified worldwide. Dead zones are regions of the ocean where dissolved oxygen has fallen to such low levels that most marine species can die.

Dead zones are not new to the world. They were around every since oceanographers started noting them during the 1970's. They increase almost every year. They are caused by increased chemical nutrients from eutrophication. More recently, dead zones have developed in continental seas, such as the Baltic Sea, Kattegat Sea, Black Sea, Gulf of Mexico, and East China Sea, all of which are major fishery areas. The Chesapeake Bay, Neuse River Estuary, Hudson River, East River, Mersey Estuary, and Thames Estuary are also on the list of spreading dead zones. Areas within ecosystems exposed to long periods of hypoxia have low annual secondary production and typically no benthic fauna.

Hypoxia tends to be overlooked until higher-level ecosystem effects are manifested. For example, hypoxia didn't become a prominent environmental issue in the Kattegat until several years after hypoxic bottom waters were first reported and fish mortality and the collapse of the Norway lobster fishery attracted attention. Usually observed data about the impact of eutrophication lagged for about 10 years before they are taken seriously as causing the spread of the dead zones. In the northern Gulf of Mexico, the occurrence and extent of the dead zone are tightly coupled with freshwater discharge from the Mississippi River, which delivers large quantities of nutrients from U.S. agricultural activities.

Dead zones caused by eutrophication are all over the world and are continuing to spread as reported by marine scientists, oceanographers and other environmental study groups.

Consequences of Marine Eutrophication

The consequences of marine eutrophication is very simple to explain. The quiet unseen changes of the body of water caused by algae and plants suffocates many of the organisms as we said before. Not only does eutrophication kill other species but the organisms that happen to survive in the water with few oxygen change. Their bodies that were originally used of their surroundings evolve and adapt to the low oxygen level. They were once edible to eat, but as their body changes, so does the human reactions toward it. Many of the fishes that change, they become poisonous to our bodies causing either weakness, blurred vision, burning muscles, difficulty breatlting, memory loss, organ damage, and even death. Here are other consequences:

  1. Red tides, water discoloration and foaming—such as that caused by the colonial flagellate Phaeocystis Pouchetii in the southern North Sea (Lancelopt et aI., 1987)
  2. Increased biomass, which may give rise to extra Biological Oxygen Demand (BOD) and hence increased removal of oxygen, in enclosed waters. These include sea-lochs such as Striven (Tett et aI., 1986) and the Baltic Sea (Larrson et al., 1985)
  3. Increased algal blooms—Algae are simple plants, which contain chlorophyll as their primary photosynthetic pigment. Algae are found in fresh and marine waters and vary in size from large kelps (meters in length) to microscopic organisms. In low numbers, most algae are harmless and are an essential part of any healthy ecosystem because they produce oxygen and are a source of food for other aquatic animals. However, excessive algae growths or blooms can cause serious water quality problems including unpleasant tastes and odors. This causes a blockade to pump and filters. In addition, dead or decomposing algae kills oxygen in the water body that kills fish and the death of other water animals.
  4. Decrease in the transparency of water—Light is essential for the growth of green plants and sunlight provides the energy for photosynthesis. The penetration of sunlight into a body of water determines the depth and quantity of algae and other underwater plants. Water transparency decreases as color, suspended sediments and algae increase.
  5. Development of hypoxic and anoxic conditions (low oxygen levels)—The level of dissolved oxygen in surface and near surface water is an important measure of the state of the health of the aquatic environment. Dissolved oxygen levels become depressed as a result of the inability of natural processes to supply oxygen at the rate demanded for the oxidation of organic matter or reduced chemical substances. Dissolved oxygen deficiency may be particularly acute in the cases of eutrophication, discharge of sewage and the discharge of organic industrial, agricultural and aquacultural effluents. Extreme oxygen deficiencies (e.g., anoxia) can result in the elimination of all higher life forms. Anoxic conditions, especially in sediments, can also lead to the liberation of less reactive forms of metals from particles into aqueous phases. Under anoxic conditions anaerobic bacteria flourish. Anaerobic bacteria often produce foul smelling compounds such as hydrogen sulphide (H2S), thioalcohols (RSH) and ammonia (NH3).
  6. Loss of habitat (e.g. Sea grass beds)—Pressures exerted on biodiversity can generally be divided into ecosystem loss, fragmentation, degradation and modification. This has resulted in the loss or extinction of many species of plants and animals. If sufficient amounts and types of suitable habitat cannot be maintained wildlife can be put at risk.

Eutrophication can cause serious effects to living resources or their habitats. Marine or estuarine systems with biogenically structured habitat, such as coral reefs or seagrass beds, are especially vulnerable to eutrophication. Bays, lagoons, enclosed seas, and open coastal waters can also be affected. The accelerated increase in the input of nutrients to the marine system represents a serious threat to the integrity of marine ecosystems and the resources they support.

Eutrophication Concerns of Two Villages: Kotlik and Sheldon Point, Alaska

The effects of eutrophication spread through the water medium, from lakes, ponds, rivers and lagoons draining down to the oceans and consequently killing organisms that maintain a balance ecosystem and the web of life. Scientific evidences have shown the reduction of the diversity of organisms. Our villages, being a part of the world are not exceptions to this phenomenon. As we tried to identify some environmental problems in our areas, we focused our study on the "honey bucket" lagoon, the garbage disposal system and the safety of the source of water (the Yukon River) used for domestic and industrial purposes, all of which are leading factors to eutrophication.


The village of Kotlik is located in the southern part of Norton Sound along the north tributary of the Yukon Delta fan. It is approximately 165 air miles northwest of Bethel and about 115 miles south of Nome. Kotlik is located near both the Yukon River and Kotlik River, which drains out to the Bering Sea. This gives barges an advance to travel here throughout the mighty Yukon and the Bering Sea.

Kotlik has a runway for which planes come through to deliver mail, freight and other supplies our village needs. These two transportation technologies make it easy for Kotlik to connect to other places of Alaska, U.S. and the world. The village has streets and sidewalks (boardwalks) that connect the whole village together. There are rarely any dirt roads due to a swampy landscape. Also Kotlik is a flat plain land formed village.

Nunam Iqua (SXP)

The City of Nunam lqua is located on the south fork of the Yukon River approximately nine miles south of Alakanuk and 18 miles southwest of Emmonak. It is the Yukon Kuskokwim Delta.

Nunam Iqua sits at the mouth of the Yukon River where Kwemeluk Pass runs to the Bering Sea. This location affords easy access by boat and barge approximately five months per year. Major barge lines deliver shipments of fuel and other bulk supplies to the city several times each summer.

Because of soft marshy ground, four wheeler travels within the community is generally limited to the boardwalks. Residents use snow machines for local travel during the winter.

The State of Alaska Demographer's Certified Population Estimate 2005 estimate is 204. The U.S. Census calculated the population of Nunam Iqua in 2000 at 201 residents.

Common Environmental Problems of Kotlik and Sheldons Point

Kotlik and Sheldon's Point (Nunam Iqua) are both Yupik Native, villages located in rural Alaska, which undergoes similar environmental issues such as waste disposal, source of water for domestic and business purposes, which are not unique to bush villages that are known as Second Class cities.

Among the environmental issue that we look to the research is how the sewer is dumped into the honey bucket lagoon. It is part of our findings that locations like this would threaten the quality of the environment and foremost would cause eutrophication.

So the consequences of eutrophication are the problem ofleeching the polluted and hypoxic conditions down the soil to the river and estuaries ending in the Bering Sea. This causes dead zones.

Concluding Statements

Our next plan:


algae bloom in the Baltic Sea

Figure 1. Algae bloom in the Baltic Sea

oil slick as a result of the exxon valdez oil spill

Figure 2. Massive oil due to the Exxon Valdez spill in AIaska.
Source: Google Images

algae blooms

Figure 3. Algae blooms resulting in red tides
Source: Google Images

Eutrophication cycle

Figure 4. Eutrophication cycle

Eutrophication cycle

Figure 5. Eutrophication cycle

phosphate cycle

Figure 6. Phosphate cycle
Source: Google Images

nitrogen cycle

Figure 7. Nitrogen cycle
Source: Google Images

the world's dead zones

Figure 8. Created by satellite, the red circles on this map show the location and size of many of ollr planet's dead zones. Black dots show where dead zones have been obselved, but their size is unknown. Darker blues in this image show higher concentrations of particulate organic matter, an indication of the overly fertile waters that can culminate in dead zones.



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