Ecology Notes Part #3

Ecology Notes Part #3 - I) Aquatic Habitats 1) Types of...

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I) Aquatic Habitats 1) Types of Aquatic Habitats a) Streams (i) A stream is water and sediment moving downhill under the influence of gravity. The force of gravity acting on the water (which flows readily) produces power that can be used to do work. The “work” that a stream does is to transport sediment moving it generally downstream, but also rearranging it within the stream. A natural stream is fed sediment and water by its entire watershed, and the sediment and water supplies are in balance through time. A stream is connected frequently to the land along its banks (riparian zone) by flooding, and the river and floodplain exchange nutrients. An estimated 2-4% of the potential energy of the water in streams is used to move sediment. Streams move billions of tons of sediment to the oceans annually. Sediment supply vs. water supply In a natural river system, the amount of water and the amount of sediment are in balance ° If one changes, the other must change ° If either changes the stream character may change Even though balanced, the stream system exists in a state of “dynamic” balance. (ii) Stream systems Difficult to study just a single stream or stream section Individual streams are part of larger stream systems Headwaters Middle reaches Downstream reaches
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Streams are hierarchical Streams flow downhill Stream systems are highest in the headwaters and move progressively downward. Thus, streams at higher elevation feed streams at lower elevation Stream systems are also higher to either side of the stream than in the stream itself; in fact, a stream runs at the lowest elevation in any given area (iii)Large woody debris Erosion brings in large woody debris Woody debris can also cause obstructions that divert flow in streams, and therefore they affect the distribution of sediments and current speeds, and build islands and shoreline sandbar (iv)Streams vary predictably with season Most streams have predictable, alternating seasonal patterns of flooding and low flow “Flood pulse” concept Provides regular access to floodplain by river species Nutrient exchange b) Lakes, reservoirs, and ponds c) Freshwater wetlands d) Tidal wetlands e) Shallow marine habitats
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Open seas and oceans 2) Streams vary predictably with season a) Most streams have predictable, alternating seasonal patterns of flooding and low flow b) ‘Flood pulse” concept (i) Provides regular access to floodplain by river species (ii) Nutrient exchange 3) What are the three scales at which we can make improvements in this stream? a) Watershed (i) What are the opportunities? (ii) What are the limitations? b) Reach (i) What are the opportunities? (ii) What are the limitations?
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Ecology Notes Part #3 - I) Aquatic Habitats 1) Types of...

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