Introduction to Freshwater Ecosystems

Sec 1-1 Why Study Freshwater Ecosystems? Over 70% of the earth’s surface is covered by water. Only 3% of the water on earth is fresh water. All but 2% is frozen in icecaps. Leaving 1% for us to protect and use.

Importance Drinking water Irrigating food crops Habitats for fish we eat Places of recreation Return water to atmosphere for water cycle

Water usage In the 1900’s: 2400 liters/day/person In the 1990’s: 9000 liters/day/person Today: 16,562 liters/day/person

Ways we use water Drinking Bathing Agriculture Industry

World water use 70% agriculture 22% industry 8% domestication

Industrialization and irrigation Reasons for increase of water usage

Humans are removing freshwater faster than the water cycle can replace it.

Freshwater ecosystems are: Dumps for domestic sewage and industrial wastes Being polluted by agricultural runoff Being depleted by overuse

Section 1-2 Types of Freshwater Ecosystems

Aquatic Ecosystems Freshwater Saltwater

Freshwater Ecosystems Standing waters (lentic) Flowing waters (lotic)

Standing waters LENTIC * Ponds and lakes (all aquatic) * Marshes, carrs, swamps, fens, bogs and sloughs -partially terrestrial -referred to as WETLANDS

Limnology- study of freshwater Limnologist-person who studies freshwater

Pond Shallow body of water Light can reach the bottom in most places Large amounts of vegetation, most of which are submerged.

Lake Deeper than a pond Too deep for light to reach the bottom in many places No vegetation in deeper areas of water.

Marsh Very shallow area with no large open areas of water. Contains soggy land areas or ‘islands’ Mostly vegetation like cattails, reeds, and grasses

Carr Very shallow area Has drier ‘islands’ Dominated mostly by shrubs

Swamp Similar to a carr The difference is the ‘islands’ have trees on them

Bog Waterlogged area, also known as peat Contains acidic water Vegetation is primarily moss

Fen Waterlogged area Contains neutral or basic water Vegetation is primarily sedges, grasses, and mosses

Slough Small lake or pond Nutrient-rich Located in low areas of prairies

Sec 1-3 Types of Lotic Waters

Ecologist classify lotic waters by a system called Stream Orders

Streams with NO tributaries are First Order Streams When 2 first order streams join they form a Second Order Stream When 2 second order streams join they form a Third Order Stream

Low order streams are often much cooler than higher order streams (on the same river system)

Reasons: First order streams originate in hilly country (slope is high = stream speed is high) turbulence causes evaporation of water = cools the stream Low order streams are small (overhanging trees and plants shield stream from the heat of the sun) Low order streams get much of their water from springs, sub-surface runoff and the water table (these sources usually contain cool water)

Stream Orders and Ecology Two main things usually happen as the stream order increases. 1. The water becomes warmer 2. The stream speed decreases These two changes cause a gradual change in ecology of the stream.

Stream Order Stream speed (m/s) Stream T (C°) Stream bottom Oxygen conc. (mg/l) Fish 1st2.212cobble11trout 5th0.627sand5carp

*As you move from the headwaters (source) to the mouth, ecological factors change. Ecological factors: 1. Geophysical 2. Chemical 3. Biological Gradually along the stream = Environmental Gradient

Sec 1-4 Lentic and Lotic How they differ….

Lentic- standing (pond, lake, wetlands) Lotic- flowing (streams and rivers)

1. Source of oxygen (s) photosynthesis (f) aeration 2. Source of food (s) autotrophic food chains (f) detritus food chains (twigs, leaves and grass) heterotrophic food chains (insects, sm land critters) 3. Adaptations of organisms ( s) critters stick in the bottom (f) hold on to rocks in fast water (benthic macroinvertebrates, mayflies, stoneflies etc)