Reading:  http://www.epa.gov/glnpo/lakeerie/eriedeadzone.html

This is a text version of the notes presented in class.

Feel free to email the instructor (knamjesn@kent.edu) with any
comments about the format and ease of use of these online notes.

1.  Lake Erie - Inland Sea in Our Backyard
- Geologic History
- Physical Processes
- Environmental Concerns
- Looking to the Future

2. The Great Lakes are Great!
- Shoreline comparable to shoreline of continental US
- Contain about 1/5 of the world's fresh water supply
- Many biological, chemical and physical processes that occur in the ocean also
   occur in the Great Lakes

3. Lake Erie Facts
Physical:
 4th largest Great Lake
 210 miles long, 57 miles wide
 570 ft above sea level
 856 miles of shoreline
 Average depth 62 feet (maximum depth=210 feet)
Processes:
 Flushing time = less than three years
 Erie exposed to greatest impacts of urbanization and agriculture
 Warmest and most biologically productive of the Great Lakes
 Often the only Great Lake to completely freeze over in winter

4. Formation of the Great Lakes
The Great Lakes are geologically young (less than 15,000 years old); formed as glaciers
  retreated at the end of the last ice age
The lakes are still changing today - Niagara Falls has moved 7 miles upstream in the last 12,000 years
 

5. Lake Erie Bathymetry
Lake Erie contains three basins:
 Western basin - shallowest
 Central basin - largest
 Eastern basin - deepest
 

6. Seasonal Stratification and Turnover
Winter      - Water is layered by temperature, with 0 degree C near surface and 4 degree C at depth
Spring/Fall  - Temperature changes at the surface causes the lake to "turn over" as surface
  temperatures warm or cool to 4oC
Summer   - Heating causes temperature layering (warm at surface, cooler at depth) and development
 of a strong thermocline
Graphic: The Great Lakes: An Environmental Atlas and Resource Book, courtesy of US EPA and
   Environment Canada, see http://www.epa.gov/glnpo/atlas/glat-ch2.html#9
 

7. Environmental Concerns
Pollution
- "nutrient pollution"
deep water anoxia (loss of oxygen)
- pathogens
- toxins
Loss of habitat and biodiversity
"Exotic" Species
Shoreline erosion
 

8. Pollution Pathways
Graphic: Sources and pathways of pollution, The Great Lakes: An Environmental Atlas and Resource
   Book, courtesy of US EPA and Environment Canada, see http://www.epa.gov/glnpo/atlas/glat-ch4.html#2

9. Pollution in Lake Erie
By early 1970's - severe pollution
 - chemical and wastewater dumping, untreated sewage, agricultural runoff, etc.
Rivers flowing into the lake were so polluted that there were advisories against contact with the water
Economic/social impact:
- decline of fishing industry and recreational use
Graphics: (top) Photo courtesy of US EPA, (bottom) Fighting a river fire, courtesy of Cleveland
Press, see http://www-great-lakes.net/teach/pollution/water/water1.html

10. Nutrient Pollution
Eutrophication:  Excessive growth of phytoplankton caused by  excess nutrients
Eutrophication upsets the natural balance of aquatic ecosystems
Causes:
- wastewater treatment plants
- factory effluent
- accelerated soil erosion
- fertilizers

11.  Lake Erie’s Problem with Eutrophication
 Low oxygen or No oxygen conditions in the summer –seasonal anoxia
 Triggered by eutrophication in the surface water
 Kills fish below in the deep water

12.  How much do fish need?  Above 6 mg/L (milligrams per Liter).
 They can’t get this much by August in Lake Erie in the central basin.

13. Fixing the Pollution Problem
1972 - US and Canada sign Great Lakes Water Quality Agreement
- Required better sewage treatment, banned sale of phosphate detergents
- Important for reducing Erie's  phosphorous levels
Current problems:
- "Non-point source" pollution (animal waste and fertilizer runoff)
    now decreasing due to better soil conservation measures
- Chemical pollutants (PCBs, Dioxin, mercury, DDT)

14. Zebra Mussels - Ecology Out of Balance
- Entered Great Lakes via ballast water
- Adult females can produce 40,000 eggs per year
- Spreads quickly, attaches to most surfaces, outcompetes native species
- Millions of $$$ spent for cleanup and control
 

15.  Zebra Mussels - An Aquatic Invader
Zebra mussels are now found in all of the Great Lakes and much of the Mississippi River drainage system.
Graphic: Zebra mussel distribution in 1990 and 2000.  Courtesy of USGS.

16. Impacts on Fisheries
Zebra mussels influence physical properties of their environment
By filter feeding they increase water clarity and remove food for large fish
Zebra mussels have had a negative impact on Lake Erie fisheries
Graphics: (top) Zebra mussels on fine-grained sediments in Western Lake Erie, photo ourtesy of USGS,
(bottom) Walleye, an economically important native species, photo courtesy Wisc. Sea Grant, see
http://seagrant.wisc.edu/greatlakesfish/walleye.html

17. A Tangled Net - Aquatic Nuisance Species (ANS) and Pollution
Lake Erie PCBs were thought to be locked in the sediments and out of the food chain - two ANS changed this...
PCBs in the tissues of:
   Smallmouth bass - 1100-1800 ppb
   Round gobis - 200-800 ppb
   Zebra mussels - 100 ppb
2000 ppb - level at which Ohio Dept. of Health issues a "no human consumption" advisory
Graphic: Courtesy of Ohio Sea Grant and Ohio State Univ.

18. Lake Erie Water Levels - What Goes Up Must Come Down
On time scales of hours to days, lake levels can seiche due to wind
On longer time scales, lake levels are determined by river inflow and evaporation
Lake levels and wave height determine the amount of shoreline erosion
 

19. Lake Erie Shoreline
95% of Ohio's Lake Erie shoreline is eroding
Erosion rates are as high as 110 feet per year
Nearly 2500 structures in Ohio are within 50 feet of destruction
Economic losses exceed tens of millions of dollars per year
 

20. "Cleveland's Municipal Stadium Attracts New Fans"     -Ohio Sea Grant Twine Line Oct/Nov 1997
In 1997, most of the Brown's Municipal Stadium was used to build 3 artificial reefs off Cleveland's shore
- An economically and ecologically sensible use of clean fill
- Support 20-60 times more fish than adjacent areas of the lake
- Each year, reefs generate tourism dollars equal to 2.75 times their cost*
* Ohio Sea Grant evaluation.
 

21. Next Lecture, Lecture 24  The Oceans and Climate, Part 1
Reading:  Chapter 8, pgs 216-228 (Chapter 8, 187-196)
                Chapter 9, pgs 244-250 (Chapter 9, 210-217)
                Chapter 18, pgs. 523-534 (Chapter 18, 452-461)
Focus Question:  How does ENSO (El Nino-Southern Oscillation) affect global climate?