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My name is Jeffrey M. Reutter. I have been doing research on Lake Erie, studying this wonderful resource, and teaching about it since 1971. I am the Director of the Ohio Sea Grant College Program (part of NOAA), the F.T. Stone Laboratory (the oldest freshwater biological field station in the country), the Center for Lake Erie Area Research (CLEAR), and the Great Lakes Aquatic Ecosystem Research Consortium (GLAERC). I have held these positions since 1987. I am here today to speak to you about the area of hypoxia or anoxia in the middle of Lake Erie, the so-called “Dead Zone,” to discuss its history, the current status of the lake, and to make a few recommendations for future action. To do this I need to tell you a little about all of the Great Lakes, how Lake Erie differs from the other Great Lakes, and a little basic limnology so you can understand the problem. I will build on my testimony before this committee in July 2002 and discuss current efforts and needs. We have also developed a poster describing this problem with I will leave with Senator Voinovich.
While this is a very complex issue, the take-home message from my testimony is simple. Due in part to changes brought about by invading species, zebra and quagga mussels, reduced water levels, and global warming, I am concerned that we are seeing indications that Lake Erie is heading back to the conditions of the “dead lake” years in the 1960s and early 70s. We must determine if that assessment is accurate, and if accurate, we must identify actions and management strategies to minimize the damage. Finally, we must recognize that the Central Basin of Lake Erie, because of its very unique morphometry, is the best indicator in all of the Great Lakes of larger stresses and problems.
Solving these problems will require coordination and collaboration on the research front, the management front, and the outreach front. Consequently, I am a strong supporter of recent funding from NOAA Sea Grant to the Great Lakes Commission and the Northeast-Midwest Institute to develop a Great Lakes Restoration Plan. I also strongly support Senator Voinovich’s efforts to sponsor the Great Lakes Environmental Restoration Act and an amendment to include the Great Lakes in the Harmful Algal Bloom and Hypoxia Act. I have also recently been appointed to the Steering Committee for the Global Ocean Observing System (GOOS) and strongly encourage everyone to support the development of an Integrated Ocean Observing System (IOOS) that includes the Great Lakes. We need a string of monitoring buoys around all of the Great Lakes.
Background and History
The Great Lakes hold 20% of all the freshwater in the world and 95% of the freshwater in the United States. The US shoreline of the lakes is longer than the Atlantic Coast, Gulf Coast and Pacific Coast, if we leave out Alaska. Approximately 30% of the US population lives around these lakes.
Lake Erie is the southernmost and shallowest of the Great Lakes. As a result, it is also the warmest. It also provides drinking water to 11 million people each day. The other Great Lakes are all in excess of 750 feet deep, and Lake Superior is 1,333 feet deep. The deepest point of Lake Erie is about 210 feet in the eastern basin, off Long Point. As a result, Lake Erie is the smallest of the lakes by volume, and Lake Superior is 20 times larger than Lake Erie. The watersheds around the other four Great Lakes are all dominated by forest ecosystems. The watershed around Lake Erie is the home to 14 million people and is dominated by an agricultural and urban ecosystem. As a result Lake Erie receives more sediment and more nutrients than the other Great Lakes. Now, if Lake Erie is the southernmost, shallowest, warmest, and most nutrient enriched of the lakes, we should expect it to be the most productive of the Great Lakes. It is. In fact, we often produce more fish for human consumption from Lake Erie than from the other four lakes combined.
Lake Erie has gone from being the poster child for pollution problems in this country to being one of the best examples in the world of ecosystem recovery. A little over 30 years ago, 1969, the Cuyahoga River burned and Lake Erie was labeled a dead lake. Nothing could have been further from the truth. In reality the Lake was too alive. We had put too many nutrients into the Lake from sewage and agricultural runoff. These nutrients had allowed too much algae to grow, and that algae, when it died and sank to the bottom, had used up the dissolved oxygen in the water as the algae was decomposed by bacteria. This sequence is a natural aging process in lakes called eutrophication, but man had accelerated the process by 300 years by putting in too much phosphorus. It is very similar to what we are seeing today in the Gulf of Mexico, but the problem in salt water is nitrogen.
Scientists divide Lake Erie into three basins based on significant differences in shape and depth. The Western Basin is the area west of Sandusky and has an average depth on only 24 feet. The Eastern Basin is the area east of Erie, Pennsylvania and contains the deepest point in the Lake. The Western and Eastern Basins have irregular bottoms with a lot of variation in depth. The Central Basin is the large area between Sandusky and Erie. The average depth of this basin is about 60 feet and the bottom is quite flat. Unfortunately, it is this shape that causes this basin to be the home of the Dead Zones.
Many of you have probably experienced swimming in a pond and noticed that the deep water was much colder than the surface water. This layering with warm water on top because it is less dense and lighter, and cold water on the bottom because it is heavier, is very common in the Great Lakes. The warm surface layer is called the epilimnion. The cold bottom layer is called the hypolimnion. The line of rapid temperature change between the layers is called the thermocline. In Lake Erie, these layers form in the late spring and break up in the fall when the surface layer cools to the temperature of the bottom layer—normally in September or October.
In Lake Erie, the thermocline usually forms around 50 feet. Based on the depths of the three basins, this means the Western Basin is too shallow to have a thermocline except on rare occasions, the Eastern Basin will have a thermocline and there will be a lot of water below it in the cold hypolimnion, and the Central Basin will have a thermocline but there will be a very thin layer of cold water under it in the hypolimnion.
At the time the thermocline forms, there is plenty of dissolved oxygen in the hypolimnion. However, due to its depth, there is often no way to add oxygen to the water in the hypolimnion until the thermocline disappears in the fall. Therefore, throughout the summer the oxygen that was present when the thermocline formed is used by organisms living in this area, including bacteria, which are decomposing algae as it dies and sinks to the bottom. If large amounts of algae are dieing and sinking, then large amounts of oxygen will be required for the decomposition process. It should then seem logical that if we could reduce the amount of algae, we could reduce the amount of oxygen that would be required to decompose the algae. It should also seem logical that if the hypolimniom was thicker (if the lake was deeper) it would have a larger reservoir of dissolved oxygen.
Because the Western Basin seldom has a thermocline, this is not a problem there. And, because the Eastern Basin is so deep, there is a large reservoir of oxygen in the hypolimnion—enough to last through the summer until the thermocline disappears in the fall. The Central Basin, however, does not have a large reservoir of water or oxygen in the hypolimnion because the basin is not deep enough. As a result, loss of all the oxygen, or hypoxia (levels below 2.0 ppm) or anoxia (no oxygen), can be a serious problem in the bottom waters of the Central Basin. Areas of anoxia were first observed as early as 1930, and by the 1960s and 1970s, as much as 90% or the hypolimnion in the Central Basin was becoming anoxic each year. This is why Lake Erie was labeled a “dead lake.” When an area becomes anoxic, nothing but anaerobic bacteria can live there. Also, this water creates severe taste and odor problems if it is drawn in by water treatment plants servicing the population surrounding the Lake.
To reduce the amount of algae in the Lake, we needed to reduce the amount of the limiting nutrient. By “limiting nutrient,” I mean the essential nutrient that is in the shortest supply. Without this nutrient algae cannot grow and reproduce. In freshwater this nutrient is phosphorus. In 1969, we were loading about 29,000 metric tons of phosphorus into Lake Erie each year. Our models told us that in order to keep dissolved oxygen in the Central Basin, we needed to reduce the annual loading of phosphorus to 11,000 metric tons. This was accomplished and the recovery of the Lake has been truly remarkable. The walleye harvest from the Ohio waters jumped from 112,000 in 1976 to 5 million in 1988 and the value of this fishery exceeds the value of the lobster fishery in the Gulf of Maine. Small businesses associated with charter fishing increased from 34 in 1975 to about 900 today, and Lake Erie became the “Walleye Capital of the World.”
Then on 15 October 1988, we documented the first zebra mussel in Lake Erie. Recognizing the significance of this discovery, Ohio Sea Grant initiated a research project on 15 November to document the expansion of the mussels. One year later, the densities in the Western Basin had reached 30,000 per square meter. Their impact was so great that in 1993 I addressed the International Joint Commission and asked them to create a special task force to try to understand the huge changes that were occurring in Lake Erie. I was asked to be US Co-Chair of the Lake Erie Task Force for the International Joint Commission from 1994-1997 as we developed models to better understand the impact of the zebra mussel on the ecosystem of the Lake.
In 1998 I formed the Phosphorus Group, a group of about 50 scientists from the US and Canada to discuss phosphorus levels to determine if they might have gotten too low and were harming the fishery—at that point the walleye fishery had been reduced by about 60% and the smelt population had been decimated. This group concluded that based on changes in the system caused by zebra mussels, adding more phosphorus would create more zebra mussels and more inedible, blue-green algae.
At the end of 1998, Drs. Jan Ciborowski (University of Windsor), Murray Charlton (National Water Research Institute of Canada), Russ Kreis (US EPA) and I formed the Lake Erie at the Millennium Program to continue to lead discussions and focus attention on the huge changes that were occurring in Lake Erie. We have documented a number of new invaders to the Lake, including the round goby, and have observed the gradual transition from zebra mussels to quagga mussels, a relative of the zebra mussel, but a species we know much less about.
In the mid-1990s, US EPA’s Great Lakes National Program Office (GLNPO) observed an increase in phosphorus levels in Lake Erie and the increasing trend has continued. They also observed areas of anoxia in the Central Basin that showed indications of growth. In 1996 we observed a bloom of blue-green algae in the Western Basin—an indication that phosphorus levels were high. In 2001 we saw more indications that dissolved oxygen levels were critically low, and we observed that mayfly larvae had been eradicated from several regions—a clear indication that oxygen had been eliminated. We also observed reduced water transparency over the artificial reefs we had worked with the City of Cleveland to produce from old Brown’s Stadium—another indication of an anoxic hypolimnion.
The above information was shared with the GLNPO and they asked me to bring together a group of Lake Erie experts for a meeting in their Chicago offices on 13 December 2001 to discuss the problems we were observing in Lake Erie and strategize about solutions. As a result of this meeting, GLNPO issued a call for research proposals in January 2002 and fund a one-year project lead by Dr. Gerry Matisoff, Case Western Reserve University, and the four scientists mentioned above from the Millennium Program, to attempt to better understand the dissolved oxygen problem in Lake Erie. This project included many scientists on both sides of the border and results have been presented in May 2003 at the Millennium Conference and at IAGLR.
Current State of the Lake
GLNPO recently completed another science cruise aboard the Lake Guardian from 14-19 August. Preliminary results from this cruise indicate that hypoxia was evident at half of the stations and only 20% of the stations showed dissolved oxygen levels about 4 ppm, the minimum level for most fish species. In June of this year, Ohio Sea Grant and Stone Laboratory placed a monitoring instrument one foot above the bottom at a station approximately seven miles north of Huron, Ohio in an area we call the Sandusky Sub-basin. This instrument, a YSI 6600, makes hourly readings of dissolved oxygen and five other parameters. This site was chosen because it is among the most productive sites in the entire lake and it was the first area to exhibit anoxia as early as 1930. This year hypoxia was first observed at this site on 4 August, and a low value of 0.2 ppm was observed on 8 August. Oxygen is not likely to return to these stations until the lake turns over during a storm this fall when the upper warm layer cools to a temperature almost equal to the cold bottom layer. It is also important to note the Microcystis sp., a harmful form of algae that produces the toxin microcystin, has been increasing in density in the Western Basin for the past two weeks and is nearing bloom levels.
I believe the oxygen problem is real and that it is growing. There are clearly a number of exacerbating conditions that are causing this. It now appears clear that Lake Erie has been gradually warming for the past 100 years, that phosphorus concentrations having been increasing since 1995, and that the water level has fallen sharply since 1997. Together, these conditions reduce the amount of oxygen available in the hypolimnion of the Central Basin and accelerate the use of the oxygen that is available. It also appears likely that zebra mussels and quagga mussels are exacerbating the problem by releasing phosphorus and allowing it to cycle more frequently through the system.
· Reduce the amount of phosphorus entering Lake Erie—difficult, but possible.
· Eliminate zebra and quagga mussels—difficult and probably not possible.
· Eliminate global warming—difficult and most people don’t even realize it is a very serious problem.
· Increase the water level of Lake Erie—currently Mother Nature holds all of the cards and models of how global warming will affect this indicate that levels are likely to go down.
The dead zone problem in the Central Basin of Lake Erie should be a wake-up call for all of us. The ecosystem in the Great Lakes cannot be taken for granted. We badly need a huge influx of federal funding on the scale of that used for the Florida Everglades to address the recovery of the Great Lakes Ecosystem from the dissolved oxygen problems to contaminated sediment and harmful algal blooms. We should all support Senator Voinovich’s efforts to sponsor the Great Lakes Environmental Restoration Act and an amendment to include the Great Lakes in the Harmful Algal Bloom and Hypoxia Act. The Senator has lead efforts in the past to improve sewage treatment capabilities. We must get behind him again to eliminate combined sewers and problems like those that occurred here in Cleveland at the sewage treatment plants during the 14 August blackout.
We badly need a coordinated plan that includes and coordinates that activities of all agencies. Some of us will be leaders and some of us must accept roles as team players. Currently, there are too many cooks in the kitchen when it comes to managing the Great Lakes Ecosystem. We need better coordination. We should all support the recent funding from NOAA Sea Grant to the Great Lakes Commission and the Northeast-Midwest Institute to develop a Great Lakes Restoration Plan.
Finally, I have also recently been appointed to the Steering Committee for the Global Ocean Observing System (GOOS) and strongly encourage everyone to support the development of an Integrated Ocean Observing System (IOOS) that includes the Great Lakes. We need a string of monitoring buoys around all of the Great Lakes so we are never caught off guard.