AQUATIC ECOLOGY CHAPTER 7b

FRESHWATER ENVIRONMENTS

I. FRESHWATER:-Water with dissolved salt concentrations less than 1% by volume.Classified as…

A) STANDING (Lentic)B) FLOWING (Lotic)

A. Standing (Lakes and ponds)- Large bodies of water that are created by…

*Glaciation- form KETTLE LAKES

*Crustal Displacement due to earthquakes

*Volcanic Activities

II. Zones within an LakeA. 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

III. 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 bottomEutrophic Lake

-Somewhere in-between the two extremes

-Category under which most lakes fall

C. MESOTROPHIC:

Secchi Disk Comparison

OligotrophicEutrophic

IV. Seasonal changes within lakes

THERMAL STRATIFICATION - Layering of water

SUMMER: three distinct layers EPILIMNION- high temp

THERMOCLINE- temp changes as go down, moderate

HYPOLINMION- low temp

ThermoclineHypolimnion

Epilimnion22˚

20˚

8˚6˚

5˚

4˚C

Summer

FALL: -Surface waters cools and sinks, the

Thermocline disappears. -Nutrients from the bottom, come up and

oxygen from the top goes down. -Process is called… FALL OVERTURN -Stratification disappears and all water is

about the same temperature.

Fall Overturn

4˚

4˚4˚

4˚

4˚C

Winter:-Cold Temperatures again cause the water

to split into different layers.

4˚C4˚C4˚C

4˚C2˚0˚

SPRING:

-Strong vertical currents mix surface and deep waters

-Temperature and oxygen levels about the same

-Process called… SPRING OVERTURN

Spring Overturn

4˚

4˚4˚

4˚

4˚C

How did the Great Salt Lake get so salty?

• Streams leading to it deposited salt picked up from the land.

• The Lake has no outlet besides evaporation.

-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

B. FlowingRivers, 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:Headwaters converge

-Stream bed of rock, pebbles, some silt- Water slows-Water Warms- Various fish with different oxygen requirements

**High fish populations are least likely to have a negative effect on D.O. concentration as opposed to Organic pollution, Algae blooms, and Thermal pollution.

C. Floodplain Zone

- 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

Rivers and Streams

2. Stream Order-A measure of the relative size of streams

First-Third Order:Headwaters

Fourth-Sixth Order: Medium Streams

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

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)

http://www.mostreamteam.org/macroinv/cranefly.jpg

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

Types of Wetlands

Roles of Wetlands

• Provide food and habitat• Improve water quality• Reduce flooding and erosion• Keep down levels of carbon dioxide• Provide recreation

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.

Wetlands and People