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09   effects on freshwater systems-1
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09 effects on freshwater systems-1

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  • 1. Effects on Freshwater Ecosystems
    • Freshwater ecosystems are particularly vulnerable to change because they tend to be individually small, and relatively isolated.
    • Affected in several ways, but primarily through temperature and stream flow.
  • 2. Freshwater Ecosystems – Temp.
    • Temperature changes can influence freshwater ecosystems in many different ways.
    • All organisms have a preferred temperature range.
  • 3.
    • Warming climate influences not just the organism itself, but also it’s prey and predators.
    • Thus entire food web dynamics are affected.
  • 4. Freshwater Ecosystems – Temp.
    • If temperature changes, organisms will migrate towards their preferred temperature – if they can .
  • 5. Freshwater Ecosystems – Temp.
    • With warming, organisms will migrate upstream towards higher elevations (cooler).
    • Less habitat area upstream!
  • 6. Freshwater Ecosystems – Temp.
    • With warming, organisms will migrate deeper (cooler).
    • Less habitat area at depth!
  • 7. Freshwater Ecosystems – Temp.
    • Decreased habitat results in unhappy fish – they don’t reproduce as much.
    • Trout habitat could shrink 30-40%, and for some species of salmon by as much as 50%.
  • 8. Freshwater Ecosystems – Temp.
    • For organisms that can’t migrate, increased temperature causes increased metabolism.
  • 9. Freshwater Ecosystems – Temp.
    • For organisms that can’t migrate, increased temperature causes increased metabolism.
  • 10. Freshwater Ecosystems – Temp.
    • Increased metabolism comes with other demands – food!
  • 11. Freshwater Ecosystems – Temp.
    • Changing water temperatures can also change the sex ratio of reptiles, amphibians, fish, and insects.
  • 12. Freshwater Ecosystems – Temp.
    • Increased metabolism increases the uptake of toxins that bioaccumulate.
  • 13.  
  • 14. Freshwater Ecosystems – Temp.
    • Temperature changes can cause indirect biologic effects as well.
    • Eutrophication.
  • 15. Freshwater Ecosystems – Temp.
    • Surface warming causes surface water to become less dense – harder to mix downward.
    • Warmer water also holds less dissolved oxygen to begin with.
  • 16. Freshwater Ecosystems – Stream Flow
    • Warmer temperatures will increase transpiration causing plants to uptake and release more water.
    • Less is available for runoff or groundwater input to lakes and streams.
  • 17. Freshwater Ecosystems – Stream Flow
    • Even though precipitation is expected to increase at mid-latitudes, it is thought that increased transpiration due to warming may offset the increase.
  • 18. Freshwater Ecosystems – Stream Flow
    • More runoff at high latitudes as more precipitation as rain than snow.
    • Remobilization of sediments.
  • 19. Freshwater Ecosystems – Stream Flow
    • Increased fluvial erosion at high latitudes.
  • 20. Freshwater Ecosystems – Stream Flow
    • Mid- and low-latitude streams and lakes likely to have less available water.
    • - more winter precipitation as rain (more will runoff than be stored).
    • - less precipitation and/or greater evaporation during summer result in lower water levels.
    • - altering of lake chemistry by ion concentration.
  • 21. Freshwater Ecosystems – Sea Level
    • Sea level rise will stress coastal wetlands.
  • 22. Freshwater Ecosystems – Sea Level