Lake Water Quality
-- phosphorus content
-- chlorophyll a content and
-- visibility through the water
Eutrophic: In lake aging pertains to an old-age lake and indicates high supply of nutrients supporting high biologic productivity.
Ecology of a lake or other body of water, containing a rich supply of plant nutrients and characterized
by seasonal periods of oxygen deficiency as a result of excessive growth of algae.
Eutrophic Pools - Two Possible States
The phosphorus content, chlorophyll a content and visibility through the water are used in the classification of lake water quality.
Mesotrophic lakes
are those normally associated with clear water conditions and a good
diversity of plant and animal life.
Hypertrophic Lakes
have high phosphorus levels leading to algal blooms, coloured water
and the loss of higher plants.
Pools found in urban areas are generally eutrophic
-- characterized by high nutrient levels, and a consequent lowering
of species diversity. Restoring pools to a mesotrophic state may be very
difficult.
Research indicates that eutrophic lakes may exist in one of two possible states:
they may either byThe depth of water, extent of surface area and type of construction (steep, shelving, etc.) have great bearing on any problems and their possible solutions.
murky and green with high levels of algae;or:
they can exist
as clear water with higher plants and a greater ecological diversity.
Site: http://www.wildlifetrust.org.uk/urbanwt/ecorecord/bap/html/uponds.htm
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Eutrophic Water | Eutrophication
Site: http://www.dragonflyireland.fsnet.co.uk/lakes_3.htm
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Site: http://www.des.state.nh.us/factsheets/bb/bb-27.htm
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Site: http://www.dragonflyireland.fsnet.co.uk/ponds_b.htm
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Dictionary: http://www.bartleby.com/61/50/E0245000.html
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Site: http://www.pku.edu.cn/academic/xb/99/_99e414.html
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Site: http://www.spatial.maine.edu/~snoox/eutrophic_lakes.htm
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Site: http://www.ukbap.org.uk/ |
Site: http://www.wildlifetrust.org.uk/urbanwt/ecorecord/bap/html/uponds.htm
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Eutrophication.
Historically, aquatic systems have been classified as oligotrophic or eutrophic.
Oligotrophic waters
are poorly fed by the nutrients nitrogen and phosphorus and have low
concentrations of these constituents. There is thus low production of organic
matter by photosynthesis in such waters.
By contrast, eutrophic waters
are well supplied with nutrients and generally have high concentrations
of nitrogen and phosphorus and, correspondingly, large concentrations of
plankton owing to high biological productivity. The waters of such aquatic
systems are usually murky, and lakes and coastal marine systems may be
oxygen-depleted at depth.
The process of eutrophication
is defined as high biological productivity resulting from increased
input of nutrients or organic matter into aquatic systems. For lakes, this
increased biological productivity usually leads to decreased lake volume
because of the accumulation of organic detritus. Natural eutrophication
occurs as aquatic systems fill in with organic matter; it is distinct from
cultural eutrophication, which is caused by human intervention. The latter
is characteristic of aquatic systems that have been artificially enriched
by excess nutrients and organic matter from sewage, agriculture, and industry.
Naturally eutrophic lakes
may produce 75-250 grams of carbon per square metre per year, whereas
those lakes experiencing eutrophication because of human activities can
support 75-750 grams per square metre per year.
Commonly, culturally eutrophic aquatic systems
may exhibit extremely low oxygen concentrations in bottom waters.
This is particularly true of stratified systems,
as, for instance, lakes during summer where concentrations of molecular
oxygen may reach levels of less than about one milligram per litre -- a
threshold for various biological and chemical processes.
Aquatic systems may change from oligotrophic to eutrophic,
or the rate of eutrophication of a natural eutrophic system may be
accelerated by the addition of nutrients and organic matter due to human
activities. The process of cultural eutrophication, however, can be reversed
if the excess nutrient and organic matter supply is shut off. This response
was demonstrated in the Great Lakes of the north central United States
which have responded to government regulations of the early 1970s aimed
at reducing phosphorus inputs (principally from detergents) into these
lakes.
Not only do freshwater aquatic systems undergo cultural eutrophication,
but coastal marine systems also may be affected by this process. On
a global scale, the input by rivers of organic matter to the oceans today
is twice the input in pre human times, and the flux of nitrogen, together
with that of phosphorus, has more than doubled. This excess loading of
carbon, nitrogen, and phosphorus is leading to cultural eutrophication
of marine systems.
Site: http://state-of-coast.noaa.gov/bulletins/html/eut_18/eut.html |
Site: http://state-of-coast.noaa.gov/bulletins/html/eut_18/national.html |
Site:
| http://www.shef.ac.uk/uni/academic/A-C/aps/level2modules/aps201/eutrophic.html |
Trophic state
Oligotrophic:
larger, deeper lakes with clear water, rocky or sandy shorelines, low phosphorus enrichment, limited rooted plant growth, low algal growth and adequate dissolved oxygen throughout.Mesotrophic:
an intermediate category with characteristics between the other two groups.Eutrophic:
smaller, shallower ponds with mucky bottoms, extensive rooted plant growth and depleted dissolved oxygen in the bottom waters; often tea-colored and sometimes murky from planktonic algal growth.Site: http://www.des.state.nh.us/factsheets/bb/bb-27.htm |
Dissolved Oxygen
This criterion can be used only for lakes that are deep enough to
develop a cold bottom layer of water (hypolimnion) during the summer. The
extent of dissolved oxygen depletion in the hypolimnion is a measure of
decomposing organic matter in the bottom waters and in the sediments, and
represents an indirect measure of the biological production in the lake.
Dissolved Oxygen (mg/L) -------------------------------
Trophic Category
> throughout the lake --------------------------------------- oligotrophic
< 1 in less than half of the hypolimnion volume ------------
mesotrophic
< 1 in more than half of the hypolimnion volume ----------- eutrophic
Site: http://www.des.state.nh.us/factsheets/bb/bb-3.htm |
Trophic state
Lake Eutrophication
What is lake aging?
Lake aging is the natural process by which a lake fills in over geologic time with erosional materials carried in by the tributary streams, with materials deposited directly through the air, and with materials produced in the lake itself. From the time that a lake is created (by glacial action), the aging or filling in process begins. Although New Hampshire's lakes have the same chronological age, they age (i.e. fill in) at different rates because of differences in runoff and watershed characteristics. The natural succession is from lake to pond, pond to marsh, marsh to meadow, and meadow to dry land. Examples of each can be seen today including areas of dry land where past lake basins can still be identified.
What is eutrophication?
Eutrophication is the process of increased nutrient input to a lake over the natural supply. This increased lake fertilization usually results in an increase in the biological production that occurs in the lake. Although the increased production may increase the rate of lake filling, it is incorrect to define eutrophication as lake aging. A lake dies not when it reaches a high state of productivity, but when it no longer exists (i.e. is filled in). Lake filling results both from production that occurs in the lake, which may increase with eutrophication, and from organic and inorganic material deposited from outside the lake, which has no relationship with lake eutrophication.
What activities cause eutrophication?
Since eutrophication is increased nutrient input, any activity in the watershed of a lake that increases nutrient input causes eutrophication. Land use changes can result in significant changes in nutrient runoff. Studies in New Hampshire have shown that phosphorus export from agricultural lands is at least 5 times greater than from forested lands, and urban areas may be more than 10 times greater. Other activities that contribute to eutrophication are lawn and garden fertilizers, faulty septic systems, washing in or near the lake, erosion into the lake, dumping or burning leaves in or near a lake, and feeding ducks.
What is meant by trophic state?
The trophic state of a lake is a hybrid concept with no precise definition. Originally, trophic referred to nutrient status. Eutrophic water was water high in nutrients and, by extension, a eutrophic lake was a lake that contained eutrophic water. Later the concept of trophic state was applied to lakes rather than water, and its precise definition was lost. Now trophic state not only refers to the nutrient status of the water, but also to the biological production that occurs in the water and to the morphological characteristics of the lake basin itself. Now a eutrophic lake may not only be a lake with high levels of nutrients, but also a very shallow pond, full of rooted aquatic plants, that may or may not have high nutrient levels.
Lakes are divided into three trophic categories: oligotrophic, mesotrophic, and eutrophic. An oligotrophic lake is typically a large deep lake with crystal clear waters and a rocky or sandy shoreline. Both planktonic and rooted plant growth are sparse, and the lake can support a coldwater fishery. A eutrophic lake, on the other hand, is typically shallow with a soft, mucky bottom. Rooted plant growth is abundant along the shores and out into the lake, and algal blooms are not unusual. Water clarity is not good and the water often has a tea color. If deep enough to thermally stratify, the bottom waters are devoid of oxygen. Mesotrophic is an intermediate trophic state with characteristics between the other two.
Trophic state
Oligotrophic:
Steep Sided, Clear WaterMesotrophic:
Low Nutrient Enrichment
Little Planktonic Growth, Low Productivity
Few Aquatic Plants
Sand or Rock Along Most of Shoreline
Coldwater Fishery
High Dissolved Oxygen Content
Moderate Nutrient EnrichmentEutrophic:
Moderate Planktonic Growth
Some Sediment Accumulation Over Most of Lake Bottom
Usually Supports Warmwater Fish Species
High Nutrient Enrichment
Much Planktonic Growth (High Productivity)
Extensive Aquatic Plant Beds
Much Sediment Accumulation on Lake Bottom
Low Bottom Dissolved Oxygen
Only Warmwater Fish Species
