Science 8: Unit E: Fresh and Saltwater Systems

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Science 8 Unit E Fresh and Saltwater Systems

• Topic 5 Living in Water

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Biodiversity in Aquatic Ecosystems

• Biodiversity variety of different kinds of
  species in an ecosystem.
• Large bodies of water have different layers or
  zones with each having its own biodiversity.
• Some organisms live in only one zone, while
  others live in all three.

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Zones in Lakes and Ponds

• Upper Zone area of a lake from the shore down
  to where the aquatic plants stop growing. Species
  you will find here include water lilieis, small
  fish, clams, insects, frogs.
• Middle Zone open water area that still has
  light reaching the bottom. Species you will find
  here include phytoplankton, fish.
• Deep Zone No light reaches the bottom, so no
  plant growth here. Food for organisms living here
  comes from dead organisms/waste from higher
  zones. Species you will find here include deep
  water fish (larger fish).

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Zones in Rivers and Streams

• Streams usually alternate between areas where
  water is calm (pools) and areas where water is
  moving rapidly (riffles).
• Organisms often attach themselves to rocks as
  their habitat.

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Zones in Oceans

• I. Estuary Where freshwater washes into the
  saltwater (at river mouths) forming brackish
  water. Makes for very diverse ecosystems.
• II. Inter-tidal Zone shoreline of ocean.
  Animals here must be able to withstand pounding
  of waves.
• III. Continental Shelf Warmer water in area
  with full light penetration. Contains
  phytoplankton and many fish and plants.
• IV. Oceanic Zone little light penetrates here
  so no plant growth.

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Aquatic Adaptations

• Adaptation physical or behavioral
  characteristic of a species that increases the
  species chances of survival in their ecosystem.
• Many aquatic organisms have adapted to being able
  to filter their food from the water.

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Aquatic Adaptations Contd

• There are five key ecosystem factors that aquatic
  species must adapt to, or die out.
• I. Temperature Species must be adapted to the
  temperature of the surrounding water. Certain
  species actually have a form of antifreeze in
  their blood to keep it from freezing in cold
  waters.
• II. Lights Levels Most species need light. Some
  animals in the ocean floor can produce their own
  light (bioluminescence).

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Aquatic Adaptations Contd

• III. Pressure Skeletal and muscular tissues are
  adapted for pressures/forces a species must deal
  with in their habitat zone. They will die if
  moved.
• IV. Salinity Because of osmosis animals have
  been adapted to specific concentrations of salt
  in the water.
• V. Water Movement Animals are adapted to deal
  with water movement and for moving through water.
  (streamlined shape of shark)

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Aquatic Plants

• Two types those that float freely
  phytoplankton, and those that attach themselves
  to ocean/lake floor.
• Stomata are specialized cells in plants that open
  and close to allow in carbon dioxide for
  photosynthesis (making sugar) or oxygen
  (consuming their sugar)
• Plants need phosphate and nitrate nutrients. They
  get these in the oceans from detritus.

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Temperature Mixing

• When temperatures cool in the fall, the surface
  water becomes denser, sinking to the bottom,
  allowing nutrients to resurface. This increases
  the phytoplankton growth. Cold water holds
  dissolved gases better than warm water meaning
  higher oxygen levels in the surface waters in the
  fall.
• The level of nutrients and salts in oceans is in
  a steady balance. Not only does it get added to
  the water as described earlier, but it is also
  taken out of the water.

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Nutrient Pollution

• Too many nutrients can cause problems in aquatic
  environments. An increase in algae growth (algal
  bloom) covers the surface of the water, blocking
  out the light. As the algae dies, they are
  decomposed by bacteria, which use up all the
  oxygen.
• This cycle continues until a balance is achieved
  again.

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Population Changes

• Population a group of organisms of the same
  species living in the same ecosystem.
• There are three types of population changes
• I. Seasonal Change Populations swell in the
  summer and disappear in winter. The disappearance
  of a population may mean survivors are dormant,
  or hibernating in the winter months.
• Breeding cycles can also cause seasonal changes
  in populations.

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Population Changes Contd

• II. Short-Term Changes take place over a
  relatively short period of time and don't last
  very long. They happen irregularly and may be
  part of a natural event, or caused by human
  activities.
• III. Long-Term Changes result from natural
  events or human activities. A landslide can
  change the course of a river or stream. Addition
  of a new species (zebra mussels introduced by
  accident) to an area (the Great Lakes) may result
  in overpopulation of that species because there
  are no natural enemies.

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Humans and Aquatic Species

• Over-fishing, dumping of toxic chemicals and
  fertilizers into aquatic ecosystems, as well as
  the use of pesticides have all negatively
  affected populations of aquatic species.
• Biomagnification Residues from human produced
  chemicals can find their way into ground water
  and bodies of water. As the chemicals move up the
  food chain, they become more and more
  concentrated in the tissues of the organisms.