09 effects on freshwater systems-1

Effects on Freshwater EcosystemsEffects 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.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp.

Temperature changes can influence freshwater ecosystems in many different ways.

All organisms have a preferred temperature range.

Warming climate influences not just the organism itself, but also it’s prey and predators.

Thus entire food web dynamics are affected.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp.

If temperature changes, organisms will migrate towards their preferred temperature – if they can.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. With warming, organisms will migrate upstream towards higher elevations (cooler).

Less habitat area upstream!

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. With warming, organisms will migrate deeper (cooler).

Less habitat area at depth!

Thermal habitat area (millions of hectares)

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Freshwater Ecosystems – Temp.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%.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. For organisms that can’t migrate, increased temperature causes increased metabolism.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. For organisms that can’t migrate, increased temperature causes increased metabolism.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. Increased metabolism comes with other demands – food!

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. Changing water temperatures can also change the sex ratio of reptiles, amphibians, fish, and insects.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. Increased metabolism increases the uptake of toxins that bioaccumulate.

Freshwater Ecosystems – Temp.Freshwater Ecosystems – Temp. Temperature changes can cause indirect biologic effects as well.

Eutrophication.

Freshwater Ecosystems – Temp.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.

Freshwater Ecosystems – Stream Freshwater Ecosystems – Stream FlowFlow

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.

Freshwater Ecosystems – Stream Freshwater Ecosystems – Stream FlowFlow

Even though precipitation is expected to increase at mid-latitudes, it is thought that increased transpiration due to warming may offset the increase.

Freshwater Ecosystems – Stream Freshwater Ecosystems – Stream FlowFlow

More runoff at high latitudes as more precipitation as rain than snow.

Remobilization of sediments.

Freshwater Ecosystems – Stream Freshwater Ecosystems – Stream FlowFlow

Increased fluvial erosion at high latitudes.

Freshwater Ecosystems – Stream Freshwater Ecosystems – Stream FlowFlow

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.

Freshwater Ecosystems – Sea LevelFreshwater Ecosystems – Sea Level

Sea level rise will stress coastal wetlands.

Freshwater Ecosystems – Sea LevelFreshwater Ecosystems – Sea Level