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By C. Kohn
Agricultural Sciences,
Waterford WI
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* 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.
beavercountyconservationdistrict.org
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* 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: http://www.marine.usf.edu/pjocean/packets/f00/nwq1.pdf
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* 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: http://www.marine.usf.edu/pjocean/packets/f00/nwq1.pdf
tutorvista.com
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* 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.
svsu.edu
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* 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.
azine.noaa.gov
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* 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.
web.bryant.edu
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* 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.
*
* 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).
mhhe.com
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* 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.
*
* 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.
*
* 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).
raptoreducationgroup.blogspot.com
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* 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).
cgee.hamline.edu
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* 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.
chem.unep.ch
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* 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!
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* 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.
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* 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.
*
* 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.
*
* 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
*
* 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.
*
* Step 4: Plants without light begin to die.
lifespan, also begins to die.
Algae, with its short
* 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.
*
* 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.