Aquatic Ecosystems Chapter 7

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Aquatic EcosystemsChapter 7
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• Aquatic ecosystems have the same things going on
  as terrestrial ecosystems, just under water
• photosynthesis (must be in upper levels of
  water)
• communities
• food chains and food webs
• predator-prey interactions
• diversity
• decomposition
• cycling of nutrients (carbon, oxygen, nitrogen,
  phosphorus)
• succession

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• Two types of aquatic ecosystems
• Freshwater lakes, ponds, rivers, streams,
  swamps, marshes, wetlands (limnology is the study
  of these)
• Marine ecosystems estuaries, salt marshes,
  mangroves swamps, coral reefs, oceans (marine
  biology and oceanography)
• What is the difference? Salinity the amount of
  dissolved salts in the water

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Freshwater Ecosystems
Ponds
Rivers
Lakes
Swamps
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Lakes

• Worlds deepest lake
• Lake Baikal, Russia (1620 m or 5371 ft. deep)
  holds 20 of the worlds freshwater
• Worlds largest freshwater lake (area)
• Lake Superior (83,300 sq. km), one of the U.S.
  Great Lakes
• Worlds largest salty lake
• Caspian Sea (about 1/3 as salty as the ocean),
  371,000 sq. km, southeast Europe/southwest Asia
• Worlds highest altitude lake
• Lake Titicaca (12,507 ft.), border of Bolivia
  and Peru

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Origins of Lakes

• Where do lakes come from? Can you name some ways
  they are formed?

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Rift lakes

• Caused by shifts in earths tectonic plates,
  forms very deep lakes
• Examples deepest - Lake Baikal (Russia), 2nd
  deepest - Lake Tanganyika (Africas rift valley)

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Volcanoes

• Forms a depression called a caldera that fills
  with water
• Example Crater Lake, Oregon

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Glacier Action
The Seven Rila Lakes, Bulgaria

• In mountainous areas, glaciers can leave series
  of basins that fill with water
• When mountains are near the sea, it can form deep
  fjords

Geirangerfjord, Norway
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Solution Lakes

• Formed in areas where soluble rock is dissolved
  by water, usually very circular, also called
  sinkholes

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River action

• Oxbow Lakes formed when river changes course
  and cuts off a small curved lake

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Wind action

• Playa Spanish word meaning beach, very
  shallow, ephemeral lakes that are only present
  after heavy rains

Playas in Texas
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Animals

• Beaver dam

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Human Activity
Hoover Dam and Lake Mead, Nevada and Arizona
Wilson Dam and Reservoir, Alabama
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What is the difference between a lake and a pond?

Size Depth Inflow and outflow
Lakes larger Deeper Rivers and streams flow in/out
Ponds smaller More shallow, sun reaches bottom throughout May not have any inflow or outflow
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Habitats in Lakes and Ponds

• Surface film due to the chemical nature of
  water water molecules are attracted to each
  other forming a film over the surface of the
  water that can support small objects, such as
  insects and floating plants

Duckweed (Lemna gibba)
Water strider
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Habitats in Lakes and Ponds

• Littoral zone
• extends out as far as rooted plants can grow
  (therefore stops where the water is too deep to
  allow light to penetrate for photosynthesis)
• area of greatest diversity of both plant and
  animal life

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Habitats in Lakes and Ponds

• Limnetic zone or open water-
• fewer living things can survive in this
  plant-free zone
• inhabited by tiny free-floating plankton large
  swimming animals (nekton)

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Habitats in Lakes and Ponds

• Benthic zone
• bottom of the lake or pond
• inhabited by decomposers, worms, insect larvae,
  clams, snails

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Categories of plants in lakes and ponds

• Emergent vegetation such as cattails
• Floating vegetation such as water lily (rooted
  on bottom) and duckweed (not attached to bottom)
• Submerged vegetation such as coontail

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Thermal stratification in lakes

• Water has different densities at different
  temperatures it is most dense at 4C
• In summer, warmer waters are at the surface due
  to the suns energy and cooler waters are at the
  bottom of lakes
• In winter, surface waters may drop below freezing
  and turn to ice while deeper waters do not
  freeze this allows fish to survive even when
  lakes freeze over

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Thermal stratification in lakes
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World Rivers
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Rivers

• Rivers begin at higher elevations with
  precipitation falling and forming small streams,
  called headwaters

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Rivers

• Smaller streams (tributaries) gather into larger
  streams and rivers
• The floodplain of a river is the area adjacent to
  it that periodically floods, the river deposits
  sediment in the floodplain making it very fertile

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Rivers

• Rivers flow down to a lake or ocean, where
  sediments can form a delta

Mississippi River delta
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Rivers

• The geographic area drained by a river is called
  a watershed

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Rivers

• Important water quality characteristics for
  rivers include
• Temperature
• Oxygen content
• Flow rate
• Nutrient/pollution content nitrates and
  phosphates

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Rivers

• Water quality changes down the river
• Headwaters are colder, have more oxygen, are
  faster flowing
• Further downstream, water is warmer, contains
  less oxygen, slower moving

Mississippi River at New Orleans
Headwaters of the Mississippi
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Wetlands

• Areas covered with water at least part of the year

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Wetlands

• Important functions of wetlands
• Water purification
• Flood control
• Buffer coastlines from storms
• Spawning grounds for fish and shellfish
• Habitat for many plants and animals
• Recreation areas for people

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Two main categories of wetlands 1. Marshes

• Found on low, flat land
• Non-woody plants reeds, rushes, cattails
• Benthic zones are very rich in nutrients
• Supports much wildlife, important to migratory
  waterfowl
• Ex Everglades

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Two main categories of wetlands 2. Swamps

• Occur in flat, poorly draining areas
• Dominated by woody species, including cypress
  trees in the southern U.S.
• Supports much wildlife, including amphibians,
  birds, reptiles and fish

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