Aquatic Biodiversity

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Chapter 6

• Aquatic Biodiversity

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Core Case StudyWhy Should We Care About Coral
Reefs?

• Coral reefs form in clear, warm coastal waters of
  the tropics and subtropics.
• Formed by massive colonies of polyps.

Figure 6-1
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Fig. 6-1a, p. 126
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Fig. 6-1b, p. 126
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Core Case StudyWhy Should We Care About Coral
Reefs?

• Help moderate atmospheric temperature by removing
  CO2 from the atmosphere.
• Act as natural barriers that help protect 14 of
  the worlds 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 earths surface

Figure 6-2
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AQUATIC ENVIRONMENTS
Figure 6-3
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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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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.

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SALTWATER LIFE ZONES

• The oceans that occupy most of the earths
  surface provide many ecological and economic
  services.

Figure 6-4
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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
  worlds ocean area but contains 90 of all marine
  species.
• Provides numerous ecological and economic
  services.
• Subject to human disturbance.

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The Coastal Zone
Figure 6-5
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Marine Ecosystems

• 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. 6-6, p. 130
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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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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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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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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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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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Threats to Coral ReefsIncreasing Stresses

• Biologically diverse and productive coral reefs
  are being stressed by human activities.

Figure 6-11
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Threats to Coral ReefsIncreasing Stresses
Figure 6-12
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Biological Zones in the Open SeaLight Rules

• Euphotic zone brightly lit surface layer.
• Nutrient levels low, dissolved O2 high,
  photosynthetic activity.
• Bathyal zone dimly lit middle layer.
• No photosynthetic activity, zooplankton and fish
  live there and migrate to euphotic zone to feed
  at night.
• Abyssal zone dark bottom layer.
• Very cold, little dissolved O2.

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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
  worlds coastal areas.

Figure 6-13
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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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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

• 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.
• What causes this overturning?

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Lakes Water-Filled Depressions
Figure 6-15
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Effects of Plant Nutrients on LakesToo Much of
a Good Thing

• Plant nutrients from a lakes environment affect
  the types and numbers of organisms it can support.

Figure 6-16
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Effects of Plant Nutrients on LakesToo Much of
a Good Thing

• Plant nutrients from a lakes 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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Effects of Plant Nutrients on LakesToo Much of
a Good Thing

• Cultural eutrophication
• Human inputs of nutrients from the atmosphere and
  urban and agricultural areas can accelerate the
  eutrophication process.

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Freshwater Streams and RiversFrom 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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Case StudyDams, 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 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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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 worlds 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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Impacts of Human Activities on Freshwater Systems

• These wetlands have been ditched and drained for
  cropland conversion.

Figure 6-19