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Water is Essential to Life
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Importance
Leonardo da Vinci said that “Water is the driver of nature.” Without water, the other nutrient cycles would not exist in their present forms, and current forms of life on earth could not exist.
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Water’s Unique Properties There are strong forces of attraction between
molecules of water. Water exists as a liquid over a wide
temperature range. Liquid water changes temperature slowly. It takes a large amount of energy for water to
evaporate. Liquid water can dissolve a variety of
compounds. Water expands when it freezes.
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Attraction Between Molecules
The strong forces of attraction between molecules of water.
Hydrogen bondsResult in many distinctive properties
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Liquid state
Exists in liquid state over wide range of temperatures:
32° F to 212° F
Without water’s high boiling point,oceans would have evaporated long ago
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Heat CapacityWater changes temp very slowly because
it can store heat. This protects living organisms from the shock of abrupt temperature changes.
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Heat CapacityAlso moderates earth’s climateWater warms & cools slower than
surrounding land
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Universal Solvent:
Water can dissolve a many substances.
• Carry nutrients• flush wastes• distribute particles• facilitate other cycles
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Universal Solvent
Water can dissolve a wide variety of compounds. This means it can easily become polluted by water-soluble wastes.
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Water CycleWater moves through
ecosystems transporting trash and other pollutants
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Expansion When Frozen
Ice has a lower density than liquid water. Thus, ice floats on water.
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Capillary action
Long narrow columns of water rise through roots to leaves
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Surface tension Surface behaves
like an elastic membrane
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Chapter 6
Aquatic Biodiversity
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Coral Reefs
Coral reefs form in clear, warm coastal waters of the tropics and subtropics. Formed by
massive colonies of polyps and algae
Figure 6-1
Among the oldest, most diverse, most productive ecosystemsMarine equivalent to tropical rain forests
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Coral Reefs Help moderate atmospheric temperature by
removing CO2 from the atmosphere.
Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms.
Provide habitats for a variety of marine organisms.
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AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones
cover almost three-fourths of the earth’s surface
Figure 6-2
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AQUATIC ENVIRONMENTS
Figure 6-3
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‣ Abiotic (physical) factors are the influences of the non-living parts of the ecosystem.
Examples include pH, salinity, temperature, turbidity, nutrients, wind speed and direction, humidity, precipitation, water pressure, and light intensity and water quality.
‣ Biotic factors are the influences of the living parts of the ecosystem. Producers and consumers interact as competitors, parasites, pathogens, symbionts, and predators.
Factors Affecting Aquatic Ecosystems
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What Kinds of Organisms Live in Aquatic Life Zones?
Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms. Plankton: important group of weakly swimming,
free-floating biota.• Phytoplankton (plant), Zooplankton (animal),
Ultraplankton (photosynthetic bacteria) Necton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds
(mostly bacteria).
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Phytoplankton & Zooplankton Phytoplankton are an
autotrophic group of weakly swimming, free-floating biota that are producers that support most aquatic food chains. These organisms provide much of the oxygen in the Earth’s atmosphere and include:
Phytoplankton (plant-like organisms and cyanobacteria
Different types of phytoplankton
Krill are one of the most important organisms in aquatic food chains especially for whales.
‣Zooplankton are herbivores that feed on plankton and are, in turn, the food stock for larger consumers like whales. These organisms include:
Krill and small crustaceans
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Nekton and Benthos Nekton are larger, actively
swimming consumers usually the top consumers in the aquatic ecosystems and include:
Fish, whales and turtles Benthos are bottom-
dwelling creatures that may be primary consumers or decomposers. These highly diverse organisms may live in tide pools, shelves or the abyss and include:
Barnacles, oysters, lobsters and sea anemones
Sharks and Turtles are nektonic species
Benthos or “depths of the sea” are organisms that live on the ocean floor
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Life in Layers
Life in most aquatic systems is found in surface, middle, and bottom layers.
Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth. Euphotic zone (upper layer in deep water
habitats): sunlight can penetrate – photosynthesis.
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Ocean Zones Coastal and Euphotic
Zone: Lots of light. From 0 - 200 meters. Photosynthesis takes place here
Bathyal Zone: The dimly lit part of ocean. From 200 - 1500 meters.
Abyssal Zone: Completely dark. Extends to a depth of 4000 to 6000 meters (2.5 to 3.7 miles). Water here is very cold & has little dissolved oxygen.
Benthic Zone(Ocean Floor): Bacteria are common & can survive down to 500 meters below ocean floor.
Abyssal Zone
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Fig. 6-5, p. 130
Dar
knes
sTw
iligh
tPh
otos
ynth
esis
Sun
Continental shelf
Estuarine Zone
High tide
Low tide
Coastal Zone
Bathyal Zone
Euphotic Zone
Abyssal Zone
Sea level
Open Sea
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Marine Ecosystems The oceans that occupy
most of the earth’s surface provide many ecological and economic services.
Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems.
Figure 6-4
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Fig. 6-4, p. 129
Natural Capital
Climate moderation Food
Animal and pet feed
Pharmaceuticals
Harbors and transportation routes
Coastal habitats for humans
Recreation
Employment
Oil and natural gas
Minerals
Building materials
CO2 absorption
Nutrient cycling
Scientific information
Marine EcosystemsEcologicalServices
EconomicServices
Genetic resources and biodiversity
Habitats and nursery areas
Reduced storm impact (mangroves, barrier islands, coastal wetlands)
Waste treatment
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The Coastal Zone: Where Most of the Action Is
The coastal zone: the warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf.
The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species. Provides numerous ecological and economic
services. Subject to human disturbance.
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Reefs Reefs:
Reefs are Marine Protected Areas like national parks and wildlife refuges and have significant economic value because of tourism. Calcium carbonate living systems in warm shallow water where light penetrates, reefs are the habitat for many species.
Loss of reefs removes habitats. Reefs are the food source for marine life, breeding grounds for fish and bird species, and shelter and hiding place for many species.
The loss of biodiversity or richness could cause the extinction or decrease in populations of marine organisms.
Reefs serve as a buffer and protection for coastal areas from waves and storms, which could lead to destruction of coastal habitats or the erosion of shoreline habitats.
Reefs are a major carbon sink in the ocean and this carbon storage would be lost.
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Sea Grass and Kelp Kelp (Seaweed):
Brown algae groups that provide habitats and food for many organisms. Overfishing leads to the degradation of kelp forests as the herbivores are released from the potential predators. (Sea otter and the urchin.)
Kelp is being considered as a renewable resource because it is fast growing and yields large amounts of methane. The fast growing algae has been the topic of renewable energy talks because of the lack of an irrigation requirement.
Seagrass:Seagrass is highly adaptable and serves as a producer for many marine ecosystems. Seagrass can reduce erosion and increase sedimentation through roots that stabilize the seabed.
These coastal seagrass zones provide shelter for organisms, wave protections, oxygen production and carbon storage.
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Estuaries
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Estuaries: Definition
A partially enclosed area of coastal water where sea water mixes with freshwater.
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Estuaries and Coastal Wetlands: Centers of Productivity
Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones.
Figure 6-7
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Estuaries Estuaries are a partially enclosed
area of coastal water where sea water mixes with freshwater and are constantly changing.
Salinity, temperature, suspended solids, storms (precipitation), and tidal cycles fluctuate with the time of year.
The organisms that live in this unique habitat must be able to tolerate these conditions.
Nutrients that are transported from rivers brings a high amount of nutrients.
This allows a place of breeding for many ocean species and thus makes estuaries highly productive and fertile supporting complex food webs.
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Estuary Ecosystem Services Estuaries serve as a carbon sink by absorbing large amounts of
CO2 (sink) and they also serve as filters for pollutants by trapping sediments and pollutants.
They act as sponges as they absorb water recharging groundwater stores and controlling flooding by slowing flow of water.
Economically wetlands are important as well:Provide employment and recreational income through fishing, recreation, and photography.Allow for protected waterway passage between rivers and oceans.Protect property by buffering shores form flow of water and erosion.Treat sewage and storm water that would otherwise be paid for by the local community.
Coastal ecosystems can easily be affected by rising sea levels, storms, temperature change, and rate of water cycling.
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Estuaries and Coastal Wetlands: Centers of Productivity
Estuaries and coastal marshes provide ecological and economic services. Filter toxic pollutants, excess plant nutrients,
sediments, and other pollutants. Reduce storm damage by absorbing waves
and storing excess water produced by storms and tsunamis.
Provide food, habitats and nursery sites for many aquatic species.
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Salt Marshes The ground here is saturated with water and
there is little oxygen, so decay takes place slowly. It has a surface inlet and outlet, and contains many invertebrates. It is also the breeding ground for many ocean animals. Ex. crabs and shellfish.
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Mangrove Forests
Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions.
Figure 6-8
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Mangrove Forests These are along warm, tropical
coasts where there is too much silt for coral reefs to grow. It is dominated by salt-tolerant trees called mangroves (55 different species exist). It also helps to protect the coastline from erosion and provides a breeding nursery for some 2000 species of fish, invertebrates, and plants.
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Importance of Estuaries
Just one acre of estuary provides $75,000 worth of free waste treatment, and has a value of about $83,000 when recreation and fish for food are included.
Prime Kansas farmland has a top value of $1,200 and an annual production value of $600.
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Mouth of river carrying erosion
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‣ Ocean margin plants, e.g. intertidal seaweeds and mangroves, must cope with high salt content in the water and changing tidal conditions.
‣ Sea level rise may change these areas, leading to a loss in species.
‣ Construction, building, roads and other residential, commercial, and industrial projects may have a negative impact.
Ocean Margin Plants
Some mangrove species take in brackish water and excrete the salt through glands in the leaves.Seaweeds
growing in the intertidal zone tolerate exposure to the drying air every 12 h.
Mangrove pneumatophores
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Rocky and Sandy Shores: Living with the Tides
Organisms experiencing daily low and high tides have evolved a number of ways to survive under harsh and changing conditions. Gravitational pull by moon and sun causes tides. Intertidal Zone: area of shoreline between low
and high tides.
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Rocky and Sandy Shores: Living with the Tides
Organisms in intertidal zone develop specialized niches to deal with daily changes in: Temperature Salinity Wave action
Figure 6-9
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Fig. 6-9, p. 132
Rocky Shore BeachSea star Hermit crab Shore crab
AnemoneSea urchin
Sculpin
Nudibranch
Low tide
Monterey flatworm
Kelp Sea lettuce
Barnacles
Mussel
Periwinkle
High tide
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Fig. 6-9, p. 132
Barrier Beach
Peanut worm
Beach flea
TigerBeetle
DwarfOlive
Clam
High tide
GhostShrimpMole
Shrimp
Sandpiper
Moon snailSand dollarWhite sand
macoma
Blue crab
Low tideSilversides
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Barrier Islands
Low, narrow, sandy islands that form offshore from a coastline.
Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea.
Figure 6-10
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Effects of Human Activities on Marine Systems: Red Alert
Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas.
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Threats to Coral Reefs:Increasing Stresses
Biologically diverse and productive coral reefs are being stressed by human activities.
Figure 6-11
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Fig. 6-12, p. 135
Ocean warming
Soil erosion
Algae growth from fertilizer runoff
Mangrove destruction
Bleaching
Rising sea levels
Increased UV exposure
Damage from anchors
Damage from fishing and diving
Natural Capital Degradation
Coral Reefs
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Bleached CoralBleached coral reef that has lost most of its algae because of changes in the environment (such as cloudy water, too warm temperatures, acidification). With the algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other algae species fill the abandoned niche, the corals die.
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Ocean Acidity The ocean acts as a CO2 sink, absorbing much of the CO2
produced by the burning of fossil fuels. CO2 reacting with water forms carbonic acid through the
chemical reaction: CO2 + H2O H2CO3
An increase in carbonic acid levels is causing the pH of the oceans to fall. This has major implications for marine life.
50510152025
8.4
8.3
8.2
8.1
8.0
7.9
7.8
7.7
7.6
pH o
f oce
an s
urfa
ce
Time (millions of years before present)
8.3
8.2
8.1
8.0
1850 1900 1950 2000 2050 2100
7.8
7.9
Possible pH range
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Effect of Ocean Acidification
Atmospheric carbon dioxide
CO2
Carbonic acidH2CO3
Water H2O
+Bicarbonate
ionsHCO3-
Hydrogen ionsH+
Carbonate ions from the sea
CO32-
+
Deformed shells
Dissolved carbon dioxide
CO2
‣ Because the oceans are naturally alkaline,acidification will not produce acid waters.
‣ Shells will not dissolve but organismswill find it more difficult to gain the CO3
2- ionsneeded to make shells.
‣ Shell making organisms are able to useCO3
2- but cannot use HCO3-.
‣ Acidification lowers the amount of CO32- available.
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Ocean pH pH is a logarithmic scale, so even a small pH change
represents a large change in H+. Thus a pH of 5 is 100x more acidic than a pH of 7.
Some areas are affected by pH change more than others. Changes may be due to:
higher human activity, e.g. sea traffic in the North Seanatural processes that affect CO2 uptake, e.g. underwater eruptions
Image: Plumbago using GLODAP data
Amount of change in ocean surface pH since 1900
-0.12 - 0.1 - 0.08 - 0.06 - 0.04 - 0.02 0 (or no data)
Change of -0.07 pH units
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Effects Oceans and seas are now being affected by an increase in global mean atmospheric temperature which can cause a rise in sea level.
Melting glaciers, continental ice caps, and melting ice sheets (Greenland and Antactica) causes the amount of water in the ocean to increase.
Thermal expansion of the ocean causes the warm water molecules to move farther apart, increasing the volume of the ocean.
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Nutrients, Oxygen & Upwelling Ocean currents are the result
of upwelling and water density. The Grand Banks of the North
American continental shelf. The shape of the deep sea-floor causes nutrient rich water to well up to the surface and the relatively shallow plateau allow a huge range of fishes to proliferate.
The Grand Banks have been fished since the fifteenth century but continual over fishing has devastated many fish stocks.
Nova S
cotia
Newfoundland
Grand Banks
Labrador Current
CANADA
Stre
am
Gulf
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Freshwater Ecosystems
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FRESHWATER LIFE ZONES
Freshwater life zones include: Standing (lentic)
water such as lakes, ponds, and inland wetlands.
Flowing (lotic) systems such as streams and rivers.
Figure 6-14
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Natural Capital
Fig. 6-14, p. 136
Food
Drinking water
Irrigation water
Hydroelectricity
Transportation corridors
Recreation
Employment
Climate moderation
Nutrient cycling
Waste treatment
Flood control
Groundwater recharge
Habitats for many species
Genetic resources and biodiversity
Scientific information
EconomicServices
Freshwater SystemsEcologicalServices
Natural Capital
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Thermal Stratification
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Lakes: Water-Filled Depressions
During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake
bottom and nutrients from the bottom are brought to the top.
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Definition
The temperature difference in deep lakes where there are warm summers and cold winters.
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Lakes: Water-Filled Depressions
During summer and winter in deep temperate zone lakes the become stratified into temperature layers and do not mix
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Thermocline
The middle layer that acts as a barrier to the transfer of nutrients and dissolved oxygen.
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Overturn
Happens in fall and spring Waters at all level mix
This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake
bottom and nutrients from the bottom are brought to the top.
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Causes
During the summer, lakes become stratified into different temperature layers that resist mixing because summer sunlight warms surface waters, making them less dense.
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Fall Turnover
As the temperatures begin to drop, the surface layer becomes more dense, and it sinks to the bottom. This mixing brings nutrients from the bottom up to the surface and sends oxygen to the bottom.
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Spring Turnover
As top water warms and ice melts, it sinks through and below the cooler, less dense water, sending oxygen down and nutrients up.
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Upwelling: Spring and Fall During summer and winter in deep
temperate zone lakes and oceans become stratified into temperature layers. The thermocline allows exchanges nutrients and temperatures and this exchange is called upwelling or turnover and occurs because of the different densities of water.
The equalizing temperature occurs at all depths so that there is a distribution of heat
During the nutrient exchange, oxygen is brought from the surface of the lake or ocean to the bottom and cold nutrient-rich water from the bottom will rise to the surface.
Spring and Fall Turnover
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Lakes: Water-Filled Depressions
Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of: Littoral zone (near shore, shallow, with rooted
plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for
photosynthesis). Benthic zone (bottom of lake, nourished by dead
matter).
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Lakes: Water-Filled Depressions
Figure 6-15
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Fig. 6-15, p. 137
Pond snail
Benthic zone
Profundal zone
Limnetic zone
Sunlight
Blue-winged teal
Muskrat
Plankton
Bloodworms Northern pikeYellow
perch
Diving beetle
Littoral zone
Painted turtleGreen
frog
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Effects of Plant Nutrients on Lakes:
Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Oligotrophic (poorly nourished) lake: Usually
newly formed lake with small supply of plant nutrient input.
Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth.
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Oligotrophic Lake
Newly formed lake Nutrient poor Deep, steep banks Glacier & mountain stream fed Crystal clear water Low productivity Small pop of fish & and
other life
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Eutrophic Lake Over time sediments, organic matter, & inorganic
nutrients wash into the lake Nutrient rich Murky water, poor visibility Shallow High productivity Lots of plant/fish life
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Effects of Plant Nutrients on Lakes:Too Much of a Good Thing
Cultural eutrophication: Human inputs of nutrients from the
atmosphere and urban and agricultural areas can accelerate the eutrophication process.
This can cause algae blooms, decreased productivity, decreased dissolved oxygen, and fish kills when the algae die and decompose
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Flowing Water Ecosystems
Because of different environmental conditions in
each zone, a river is a system of different ecosystems.
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Fig. 12-11, p. 267
• Deliver nutrients to sea to help sustain coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
Natural Capital
Ecological Services of Rivers
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Freshwater Streams and Rivers:From the Mountains to the Oceans
Water flowing from mountains to the sea creates different aquatic conditions and habitats.
Figure 6-17
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Fig. 6-17, p. 139
Source Zone
Rain and snow
Lake GlacierRapids
WaterfallTributary
Flood plain Oxbow lake
Salt marshDelta Deposited
sedimentOcean
SedimentWater
Floodplain Zone
Transition Zone
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Freshwater Streams and Rivers Watershed or drainage basin
Area that supplies runoff Small streams join to form rivers Begin in higher elevation – mountains Rain or melting snow
Three Zones Source Transition Floodplain
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Source Zone: Headwater A narrow zone of cold, shallow, clear, swiftly flowing water
with waterfalls and rapids. Turbulent, large amounts of dissolved oxygen Cold water fish are also present. Ex. trout. Low nutrient, phytoplankton, & productivity Fish & animals flat, muscular, live under rocks, fight current Plants & algae attach to rocks
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Transition Zone Streams merge to form wider, deeper Gentle slopes with fewer obstacles lower dissolved oxygen Supports more producers (phytoplankton) Cloudy Slower flow Warmer
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Floodplain: Downstream Wide, deep rivers flow across broad, flat valleys. Rich farm land Higher temp Provide habitat Less dissolved O2
Slow moving water Absorb flood water Large pop of plants & algae Erosion & runoff cause murky water with high levels of
suspended particulates (silt) Mouth of river divides into many channels – Delta –
built up as silt is deposited
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Case Study:Dams, Wetlands, Hurricanes,
and New Orleans Dams and levees have been built to control
water flows in New Orleans. Reduction in natural flow has destroyed
natural wetlands. Causes city to lie below sea-level (up to 3
meters). Global sea levels have risen almost 0.3 meters
since 1900.
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Freshwater Wetlands
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Freshwater Inland Wetlands: Vital Sponges
Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats.
Figure 6-18
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Freshwater Inland Wetlands: Vital Sponges
Filter and degrade pollutants. Reduce flooding and erosion by absorbing
slowly releasing overflows. Help replenish stream flows during dry
periods. Help recharge ground aquifers. Provide economic resources and recreation.
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Inland Wetlands Inland wetlands are defined by their water quality, soil
type, and species composition.
Wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. They also filter and degrade pollutants.
Wetlands replenish stream flows during dry periods and recharge ground aquifers. If ground water is being depleted then saltwater intrusion may occur.
Freshwater W
etlandWetlands provide many ecosystem services
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Marshes
An area of temporarily flooded, often silty land beside a river or lake.
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Swamps
A lowland region permanently covered with water.
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Hardwood Bottomland Forest
An area down by a river or stream where lots of hardwoods, like oaks, grow.
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Prairie PotholesThese are depressions that hold water out
on the prairie, especially up north in Canada. It is a very good duck habitat.
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Peat Moss BogA wet area that over time fills in (the last
stage of succession is peat moss). It can be very deep. In Ireland, they burn peat moss for wood.
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Importance of freshwater wetlandsThey filter & purify water.Habitat for many animals and
plants.Since 1600s, over half of US
wetlands have been drained & converted to farmland
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Historical Aspects Developers and farmers want Congress to
revise the definition of wetlands. This would make 60-75% of all wetlands unavailable for protection. The Audubon Society estimates that wetlands provide water quality protection worth $1.6 billion per year, and they say if that wetlands are destroyed, the U.S. would spend $7.7 billion to $31 billion per year in additional flood-control costs.
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Impacts of Human Activities on Freshwater Systems
Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats.
Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers.
Flood control levees and dikes alter and destroy aquatic habitats.
Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.
Many inland wetlands have been drained or filled for agriculture or (sub)urban development.
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Human Effects on Aquatic Systems
Most water used by humans comes from rivers, lakes, & aquifers.
Damming rivers for electricity affects water flow downstream as seen in the James Bay project in Quebec with over 600 dams blocking 19 rivers.
Irrigation and diversions for drinking water displace vast amounts of the water for these resource stores.
Pollution from fertilizers, waste, an sewage can have paralyzing effects on rivers, lakes, and oceans.
These actions can have dramatic effects on the habitats and can cause loss of biodiversity.
Irrigation can move move millions of liters of water from rivers and aquifers, affecting land down stream.
Damming and diverting rivers lowers the availability of water downstream and stops annual floods that
replace soil nutrients.
Dams, locks and other obstacles make it very difficult for migratory fish to find their way to breeding grounds.
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Impacts of Human Activities on Freshwater Systems
These wetlands have been ditched and drained for cropland conversion.
Figure 6-19