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Water Quality Management In
Lakes
Dr. Philip Bedient
Control of Phosphorus in Lakes
Phosphorus is usually the limiting
nutrient
 Control of cultural eutrophication must
be accomplished by reducing the input
of phosphorus to the lake
 Phosphorus concentration is reduced as
it is buried in the sediment
 Sources of phosphorus:
 Weathering of rocks
 Human activity such as municipal and
industrial wastewaters, seepage from
septic tanks, and agricultural runoff
that contains phosphorus fertilizers
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Municipal and Industrial
Wastewaters
Both municipal and industrial
wastewaters contain phosphorus from
human excrement
 The only way to reduce this is by
advanced waste treatment processes
 Major source of phosphorus used to be
laundry detergent
 These detergents were banned to help
reduce phosphorus input into lakes

Septic Tank Seepage
If the capacity of the soil to adsorb
phosphorus is exceeded, all additional
phosphorus is sent to the lake
 The time for phosphorus to reach the
lake depends on:
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Type of soil
Distance to the lake
Amount of wastewater generated
Concentration of phosphorus in wastewater
To prevent phosphorus from reaching
lakes, the tile field must be put far
away from the lake so that the
adsorption capacity of the soil is not
exceeded
Agricultural Runoff
Phosphorus is an
important ingredient in
fertilizers
 Phosphorus bound to
soil particles is carried
to lakes by soil erosion
 To help stop this:
 Farmers can fertilize
more often with
smaller amounts
 Actions can be taken
to stop soil erosion

Acidification of Lakes
Pure rainwater is slightly acidic with a
pH of 5.6
 Acid Rain- precipitation with a pH less
than 5.6
 Acid rain has caused:
 Complete eradication of some fish
species
 Acidification of more than 1350 midAtlantic Highland streams
 Acidification of about 580 streams in
the mid- Atlantic Coastal Plain
 Acidification of more than 90% of
streams in the New Jersey Pine
Barrens

Acid Rain
Low pH levels are caused by emissions
of sulfur and nitrogen oxides from the
combustion of fossil fuels
 Acid decomposition-term for acid rain
because it can be deposited in both a
wet and dry form
 Fish are often killed by low pH levels
and high aluminum concentrations

Aluminum Concentrations
At conventional pH levels, aluminum
rarely exists
 Acid deposition can cause stress effects
on aquatic organisms such as:
 Failure to reproduce
 Gill damage resulting in respiratory
problems
 Failure of eggs to hatch
 Interference with Ca uptake
(molluscs)

Acidification of Lakes
Lakes have a carbonate
buffer system
 If the buffer capacity of
the lake is not
exceeded, pH of the lake
will not be affected by
acid rain
 Calcareous soil- contains
large quantities of
calcium carbonate
(CaCO3)
 Lakes formed in this
type of soil resist
acidification

Acidification of Lakes Cont.
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Factors that affect susceptibility of a
lake to acidification:
 Depth of soil
 Make up of bedrock
 Slope and size of watershed
 Type of vegetation
Water Quality in Estuaries
Estuary- formed along
the coastline where
freshwater from rivers
and streams flows into
the ocean
 Water transitions from
fresh to salty
 Estuaries are:
 Partially enclosed by
land
 Influenced by tides
 Protected from the
ocean’s wind,
waves,etc.

Estuaries Cont.
Also referred to as bays, lagoons,
harbors, inlets, or sounds
 Complex and specialized ecosystems
form out of a cycle of wetting and
drying, and the submersion and
reappearance of aquatic organisms
 There is an abundance of life-giving
nutrients
 Many different species and habitats
exist here

Functions of Estuaries
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Estuaries:
 Provide sanctuary to nesting and
spawning animals
 Filter water of its sediments and
pollutants and make it clean
 Absorb floodwaters and dissipate
storm surges
 Help prevent erosion
 Make shorelines more stable
Estuaries and Wildlife
Estuaries have recently experienced:
 Declines in fish and wildlife
 Introduction of invasive species
 Deterioration in water quality
 Reduction in overall ecosystem health
 Too many nutrients can cause:
 Fish disease
 “Red and brown tides”
 Algae blooms
 Low dissolved oxygen
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Estuaries and Pathogens
Pathogens are harmful to swimmers,
surfers, divers, and seafood consumers
 Sources of pathogens include:
 Urban and agricultural runoff
 Illegal sewer connections Faulty or
leaky septic systems
 Sewage treatment plant discharges
 Combined sewer overflows
 Boat and marina waste
 Waste from wildlife
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Estuaries and New Species
With the global transportation system
came the introduction of nonnative or
exotic species
 The introduction of exotic species has:
 Modified nutrient cycles of soil fertility
 Increased erosion
 Interfered with navigation
 Helped develop agricultural irrigation
 Introduced sport and commercial
fishing
 Increased boating and beach use
 The Chesapeake Bay Agreement and
the National Estuary Program (NEP)
were created to protect ecosystems
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4 Aspects of an Estuary
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In order to understand an estuary, the
following issues must be studied:
 Salinity
 Nutrients
 Wildlife, Fish and Shellfish
 Toxicants
Salinity in Galveston Bay
There has been a decline in the bay’s
salinity
 Most bayous are experiencing an
increase in flow due to:
 Increase in development
 Increased return flows of wastewater,
including groundwater
 Salinity dynamics in Galveston are now
more obscure, complex,
and intractable
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Nutrients in Galveston Bay
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60% of wastewater in Texas flows to
Galveston Bay
Much of the upper watershed consists
of cultivated and urban lands with high
nutrient runoff potential
There has been a decline in the loading
of nutrients into the bay
There has been a reduction of point
source loadings
The problem now is urbanized
tributaries where fish kills and dissolved
oxygen problems suggest nonpoint
source problems
Galveston’s Wildlife, Fish and
Shellfish
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There has been a loss in
emergent wetlands
The leading cause of
habitat loss is converting to
open water and barren flats
Urban development is
responsible for less than
10% of wetland loss
There was a decline for
only 2 out of 14 finfish and
shellfish species that were
analyzed
Has a great effect on birds
Toxicants in Galveston Bay
Toxic contamination poses a risk to
individual recreational or subsistence
seafood consumers
 The highest concentrations of toxicants
are usually in the upper bay
 There is much need for:
 Development of sediment standards
 Improvement of analytical techniques
 Improved risk analysis
 Communication of risks to
the seafood-consuming public
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Galveston’s Habitats
Habitats are being destroyed by human
activity
 Much wetland loss is due to conversion
to open water or mud flats
 Many aquatic vegetation beds
(especially seagrass) have been lost
due to:
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 Subsidence
 Hurricane Carla
 Shoreline development
 Wastewater discharges
Dredging
Chemical spills
Boat traffic
 Loss of habitat poses a threat to
seafood productivity and the ability for
the bay to be a healthy ecosystem