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By C. Kohn Agricultural Sciences, Waterford WI

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1 By C. Kohn Agricultural Sciences, Waterford WI
Water Pollution By C. Kohn Agricultural Sciences, Waterford WI

2 Aquatic Ecosystems Aquatic ecosystems include oceans, lakes, rivers, streams, estuaries, and wetlands. These ecosystems are easily distressed by pollution. Surface water ecosystems are those found in rivers, wetlands, and lakes. All precipitation eventually finds its way into a surface water ecosystem. The area of land from which a body of water gets its water is known as a watershed. Surface water ecosystems are critical to the survival of other kinds of ecosystems found on dry land.

3 Surface Water Ecosystems
Surface water ecosystems are vital for land-based animals. Wildlife depends upon surface water ecosystems for food, shelter, and breeding. They also can provide much needed water for birds and wildlife. Surface water ecosystems are also important to the watershed connection. They capture rainwater as it flows over the ground, reducing erosion and flooding. By holding stormwater, ponds allow nutrients and other chemicals to be filtered from the water by plants and animals before it moves into rivers and lakes. Source:

4 How Aquatic Ecosystems Work
Plants are vital to a functioning aquatic ecosystem. At the base of the food chain are small aquatic algae called phytoplankton. These algae use sunlight to convert CO2 and H2O into sugar. Tiny animals in the water, called zooplankton, use phytoplankton as a food source. Zooplankton are consumed by aquatic insects called macroinvertebrates. Larger animals such as fish, use zooplankton and macroinvertebrates as a food source. Source:

5 Aquatic Ecosystem Health
Discussion: How can you tell if a body of water is healthy? What signs indicate whether or not an aquatic ecosystems is affected by a disturbance? Visible signs of pollution, odor, dead fish, and poor taste (for drinking water) are all signs that a body of water has been affected by a disturbance. Often, indications of pollution are much more subtle and require more testing than simply observing the water. When determining if a body of water is affected by a pollutant, we cannot wait until the signs of are obvious and visible before we take action. To wait this long could put the aquatic ecosystem at risk of irreparable damage. Sometimes signs of a pollutant are not obvious even at dangerous levels. For example, we cannot see, smell, or taste toxic levels of mercury.

6 Water Pollution Pollution is defined as the introduction of a substance into a natural environment that causes instability, disorder, or harm to the ecosystem Aquatic pollutants can be divided into two categories: Point Source Pollution – this is pollution that originates from a single source This could be a factory, failing sewage treatment plant, or a damaged sewer pipe. Non-point Source Pollution – this is pollution that cannot be traced to a specific point because it comes from many individual places over a large, widespread area. Agriculture is the largest source of non-point water pollution. Parking lots, suburban lawns, and roads also are common sources of non-point pollution.

7 Biomagnification Some pollutants are more of a concern because of the process of biomagnification. Biomagnification: the process in which pollutants become more and more concentrated in living tissue. Biomagnification enables a pollutant that is found in small amounts in the environment to become highly concentrated in the tissues of large organisms. This can cause those organisms to become adversely affected by what may seem like a small problem in the environment.

8 Biomagnification Biomagnification occurs because the pollutant will become stored in the bodily tissue of every organism that consumes it. A toxin will first be absorbed in small amounts by phytoplankton. Species at the bottom of the food chain (like zooplankton & aquatic insects) will eat large amounts of this phytoplankton. Small fish will eat large amounts of these zooplankton & macroinvertebrates (insects), and these small fish will be eaten by larger game fish.

9 Biomagnification Biomagnification increases with every step in the food chain. Macroinvertebrates & zooplankton will eat many, many phytoplankton. Many of these insects, which have eaten many, many phytoplankton, will be eaten by small fish. All of the pollutants absorbed by the phytoplankton were trapped in the tissue of the insects and are now in the bodies of the fish. All of the pollutants trapped in these fish will become trapped in the bodies of larger fish and other large predators (including mammals, birds, and humans).

10 Biomagnification Three characteristics are necessary in order for a pollutant to biomagnify: 1. The pollutant must be long-lived – if the pollutant breaks down too quickly, it would pass out of the tissue of living organisms 2. The pollutant must be concentrated in organisms at the base of the food chain – usually biomagnification starts with a photosynthetic organism or an animal that is widely consumed by other animals. 3. The pollutant must be fat-soluble – this allows it to be stored in the tissue of living organisms. Water soluble substances are passed out of animal bodies when they urinate. Only fat soluble substances can be stored in the body and accumulate.

11 Biomagnification Each time a toxin goes up a level in the food chain, it becomes more and more concentrated in the tissues of living organisms. Because humans are at the top of the food chain and live long lives, we are most susceptible to fat-soluble toxins. These are toxins that are able to be stored for long periods of time in body fat and tissue.

12 Biomagnification Many pollutants that biomagnify interrupt the ability of an organism’s body to function. Lead, mercury, and heavy metals all can biomagnify and can cause nervous problems, infertility, and birth defects. Hunters should never use lead-based ammunition, and lead sinkers should never be used by fishermen because of these concerns. This may not seem like a big deal because the amount of lead lost by these objects may seem small and insignificant. However, even a small amount of lead will bioaccumulate over time (such as in this bald eagle dying of lead poisoning).

13 Mutagenic Pollutants Other pollutants can be mutagenic and interfere with a living organism’s DNA. DNA is basically the instruction manual for a living organism’s cells. When a mutagenic pollutant is present, it can interfere with the instructions given by DNA, causing birth defects, cancer, and other adverse health effects. If the instructions for your cells to operate are changed, your cells will not function normally. This is exactly how a mutagen and can cause tumors, infertility, developmental problems, and other serious issues in both humans and animals (such as the 5th leg on this frog).

14 PCBs PCBs are a good example of a mutagenic pollutant.
They were used because they were not flammable, were very chemically stable, did not melt easily, and were great insulators for electrical wiring. They were widely used in paints, plastics, rubber products, dyes, and many other industrial applications. PCB’s were manufactured from 1929 until they were banned in 1979. Despite being banned in 1979, PCBs still enter the environment due to improper disposal of old equipment, leaking hazardous waste sites, and the burning of wastes. Once released, PCBs break down very slowly and are easily carried all around the world by rain, snow, and water.

15 PCBs If ingested in high enough levels, PCBs can cause cancer, weaken the immune system, reduce birth weights, lower fertility, and cause neurological problems. PCB levels in top predators such as bald eagles, lake trout and humans can be millions of times those found in surface water. Every time a large predator consumes their prey, they increase the concentration of toxins in their bodily tissue if they are in an area affected by biomagnification. As a student in Wisconsin, you too are a large predator in an area such as this!

16 PCBs Because PCBs can be stored in body fat, they stay can build to harmful levels over time. This can have a major impact on children because they are still developing. This is why children and pregnant women are advised to minimize their consumption of large fish. 30 years after they were banned, PCB’s are a major concern even today. E.g. as recently as October 19th, 2009 dredging of the Fox River in Green Bay was halted to prevent the spread of PCBs. However, if the Fox River cannot be dredged so that ships can easily pass through, it may seriously affect the 650 jobs and $75 million that shipping on this river contributes to Green Bay. The impacts of water pollution are economic as well as environmental and health-related.

17 Eutrophication A substance does not have to be toxic or mutagenic to be a pollutant. Fertilizers are a major source of water pollution and are not nearly as toxic or mutagenic as some more commonly known pollutants. Agricultural fertilizers are a concern because they can cause an ecological problem that other pollutants cannot – eutrophication Eutrophication is the process in which the levels of water nutrients become too high, eventually causing dissolved oxygen levels in the water to become too low.

18 Eutrophication The process of eutrophication involves a complex series of steps. In a way, eutrophication is sort of like a set of falling dominoes. When dominoes fall, it is because of a chain reaction, with one domino causing the fall of another. Similarly, high levels of nutrients cause oxygen levels to become too low due to a serious of steps and interactions. These steps can seem unrelated but can ultimately cause the destruction of an aquatic ecosystem.

19 Eutrophication Step 1: The levels of nutrients become too high.
This could occur for a number of reasons but is most commonly caused by runoff. For example, if fertilizer is spread on a field, rain water may carry soil and the fertilizer’s nutrients into a nearby body of water. This will raise the levels of nitrogen and phosphorus. These nutrients stimulate plant growth. Excessive nutrient levels can come from a variety of sources including… Over-fertilized fields Poorly built feedlots Over-fertilized yards and lawns Overwhelmed sewage treatment plants

20 Eutrophication Step 2: The nutrients from the fertilizer cause plants and algae to grow rapidly and excessively. Fertilizers work in water just like they do in land. Step 3: The rapid growth of algae enables a thick mat of algae to form on the surface of the water. Light cannot penetrate this mat of algae. Because there is no light, plants cannot photosynthesize under the water. Because plants can’t photosynthesize, they can’t produce oxygen, and oxygen levels begin to drop.

21 Eutrophication Step 4: Plants without light begin to die. Algae, with its short lifespan, also begins to die. As these organisms die, they decompose. The process of decomposition requires oxygen As decomposition increases, oxygen levels continue to decrease. With two factors reducing oxygen (low light and high decomposition), dissolved oxygen levels in the water begin to drop to dangerously low levels. Step 5: Low levels of oxygen reduce many kinds of desirable organisms, including game fish and the macroinvertebrates (insects) they prey upon. The balance of the food web is upset by the loss of these species.

22 Eutrophication The aquatic ecosystem becomes less and less suitable for native species. To make matters worse, the risk of invasive species (including carp and invasive species of cattails) increases as native species decrease. The invasive species are often more competitive in low-oxygen conditions and out-compete the native species. As plant matter accumulates (due to the explosive growth caused by high nutrient levels), these aquatic ecosystems become shallower over time. This too reduces the ability of that habitat to sustain native species.


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