introduction to freshwater ecosystems. sec 1-1 why study freshwater ecosystems? over 70% of the...
TRANSCRIPT
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 EcologyTwo 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
1st 2.2 12 cobble 11 trout
5th 0.6 27 sand 5 carp
*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 LoticHow 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)