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AQUATIC ECOLOGY CHAPTER 7b
FRESHWATER ENVIRONMENTS
I. FRESHWATER:I. FRESHWATER:
-Water with dissolved salt concentrations less than 1% by volume.
Classified as…
A) STANDING (Lentic)
B) FLOWING (Lotic)
A. Standing Water (Lakes and ponds)- Large bodies of water that
are created by…
a. Glaciation-
form KETTLE LAKES
b. Crustal Displacement due to earthquakes
c. Volcanic Activities
Kettle Lakes
• http://www.guardian.co.uk/environment/video/2011/oct/11/lake-imja-climate-change
1. Zones within a Lake
A. LITTORAL ZONE- Shallow sunlit waters near the shore.
B. LIMNETIC ZONE- Open, sunlit waters. From surface to depth of last sunlight.
C. PROFUNDAL ZONE- Deep open water, below level of sunlight
D. BENTHIC ZONE- Bottom, low oxygen level
Sunlight
Paintedturtle
Greenfrog
Pondsnail
Blue-wingedteal
Muskrat
Plankton
Northernpike
BloodwormsYellowperch
Divingbeetle
Littoral zone
Limnetic zone
Profundal zone
Benthic zone
2. Classification of Lakes- Classification of lakes is according to
nutrient content and primary productivity.
-Lakes are classified into three main types…
a. OLIGOTROPHIC:
• Deep, clear water• Few minerals• Steep sides• Low Primary
Productivity• Low, large fish
populations
Sunlight
Limnetic zone
Profundal zone
Sand, gravel,rock bottom
Oligotrophic Lake
Sparce fish population
Low concentration ofnutrition and plankton
Narrowlittoralzone
Steeplyslopingshorelines
Little shorevegetation
• Shallow, murky water• High Primary Productivity• Large Fish Populations
b. EUTROPHIC:
Sunlight
Much shorevegetationMuch shorevegetation
High concentrationof nutrition and plankton
Widelittoralzone
Limnetic zone Dense fish population
Gently slopingshorelinesSalt, sand,
clay bottom
Eutrophic Lake
-Somewhere in-between the two extremes
-Category under which most lakes fall
c. MESOTROPHIC:
Secchi Disk Comparison
OligotrophicEutrophic
3. Seasonal changes within lakes
-Water is most dense as a liquid & least dense as ice (why ice floats on water)
a. Properties of water cause THERMAL STRATIFICATION in deep lakes in temperate areas.
In the SUMMER lakes form three distinct layers:
1. EPILIMNION- upper layer of warm water
2. THERMOCLINE- temp changes as go down
3. HYPOLINMION- lower layer of colder, denser water
ThermoclineHypolimnion
Epilimnion22˚
20˚
8˚6˚
5˚
4˚C
Summer
b. FALL:
1. Surface waters cools and sinks, the Thermocline disappears.
2. Nutrients from the bottom, come up and oxygen from the top goes down.
3. Process is called… FALL OVERTURN
-Stratification disappears and all water is about the same temperature.
Fall Overturn
4˚
4˚
4˚4˚
4˚C
c. Winter: 1. Cold Temperatures again cause the water to
split into different layers.
4˚C4˚C4˚C
4˚C2˚
0˚
d. SPRING:
1. Strong vertical currents mix surface and deep waters
2. Temperature and oxygen levels about the same
3. Process called… SPRING OVERTURN
Spring Overturn
4˚
4˚
4˚4˚
4˚C
-In PA all IMPOUNDMENTS (lakes and ponds) fall under the jurisdiction of the Pennsylvania Fish and Boat Commission (PFBC)
-Ponds are less than 50 acres of surface area and run an average of 12-15 feet. (250 in state managed by PFBC)
-Lakes are defined as bodies of water with greater than 50 acres of surface area and range in depth from 15-5000 feet. (124+ in state managed by PFBC) (Conneaut Lake)
-Reservoirs are defined as having surface areas greater than 500 acres. (31 in state managed by PFBC) (Pymatuning and Kinzua)
http://sites.state.pa.us/PA_Exec/Fish_Boat/lakes.htm
How did the Great Salt Lake get so salty?• Great Salt Lake is the remnant of Lake Bonneville; a great ice
age lake that rose dramatically from a small saline lake 30,000 years ago.
• Streams leading to it deposited salt picked up from the land.
• The Lake has no outlet besides evaporation.
B. Flowing Water (Rivers, Streams, Wetlands)
- Created by surface water runoff
- Runoff for a particular area is called WATERSHED or DRAINAGE AREA. (6 major watersheds are found in PA)
- Most streams/rivers start in mountains or hilly areas.
Which watershed is Jefferson Hills located in?
OHIO:
Second largest in state
Covers nearly 16,000 miles of the state
Most waterways empty into the Ohio River
Ultimately dump into the Mississippi
SUSQUEHANNA:
Largest in state
Covers 46 percent of the state
*Ultimately dumps into the Chesapeake Bay
POTOMAC:
About 1500 square miles
Drains to the Potomac River even though it is not in the state.
DELAWARE:
Third largest in state
Covers nearly 6,500 miles of the state
Most waterways empty into Hudson Bay
ERIE:
Small part of Great Lakes Basin
Drains into lake Erie
GENESEE:
Small part of Great Lakes Basin
Drains into lake Ontario
1. Streams/River Characteristics
a. Source Zone (HEADWATERS)
- Cold, Clear
-Many large rocks as base material, waterfalls
- High amounts of dissolved oxygen
- Algae and Moss are predominant and adapted to attach to rocks
- Fish ,especially Trout, and organisms that require higher D.O. levels.
b. Transitional Zone (middle):
- Headwaters converge
- Stream bed of rock, pebbles, some silt
- Water slows
- Water Warms
- Various fish with different oxygen requirements
c. Floodplain Zone (bottom)
- Streams join into wider and deeper rivers that meander across broad flat valleys.
-Stream bed silty, few rocks
- Low oxygen levels
- Higher water temps.
- Murky water
Rain and snow
Water
Sediment
Lake Glacier RapidsWaterfall
TributaryFlood plain
Oxbow lakeSalt marsh
Delta
Ocean
Depositedsediment
Source Zone
Transition Zone
Flood-Plain Zone
2. Stream Order
-A measure of the relative size of streams
a. First-Third Order: Headwaters
b. Fourth-Sixth Order: Medium Streams
c. Seventh Order -Larger: River
-Runoff from PA is delivered to other states through three main rivers.
-PA has 11 main rivers that run through three drainage basins (Ohio, Susquehanna, Delaware)
-Rivers stretch over 1,200 miles and cover 145,000 acres.
-Historical threats to rivers: AMD, coal mining, logging, Siltation, Sewage, agriculture.
PENNSYLVANIA FACTS
3. COLDWATER STREAMS
-Water temp. rarely over 68 degrees ”typically the maximum temp.”
-High amounts of oxygen
-Classified as LIMESTONE and FREESTONE
-Usually considered to be headwaters or first-order streams.
• Cooler temperatures in headwater stream are due to the higher altitude, narrower channel, and higher water velocity.
-Stonefly, Caddisfly,Craneflies (larvae)
-Top consumer is Trout. (Brook, Brown, Rainbow)
3. WARMWATER STREAMS
-Water temp. over 68 degrees
-Lower amounts of oxygen
-Usually considered to be first-order or second –order streams.
-Diving beetles, Dragonflies, caddisflies, whirligigs, damselfly…
-Forage fish like shiners, fallfish, minnows
-Top consumer vary – bass, sunfish, pike, walleye, muskie, eels, carp, catfish, pickerel, gar
C. Wetlands
• Defined as lands covered with fresh water all or part of the time.
• Include…–Marshes–Swamps–Bogs– tundra
1. Roles of Wetlands
• Provide food and habitat• Improve water quality• Reduce flooding and erosion• Keep down levels of carbon dioxide• Provide recreation
2. Human Impact on Wetlands
• Estimated that 150 square miles of wetlands are lost each year in the U.S.
• Lost to development, agriculture, mining, forestry, oil/gas extraction, and highways.
