TESTIMONY OF
JEFFREY M. REUTTER,
Ph.D., DIRECTOR
OHIO SEA GRANT COLLEGE
PROGRAM,
F.T. STONE LABORATORY,
CENTER FOR LAKE ERIE
AREA RESEARCH (CLEAR), AND
GREAT LAKES AQUATIC
ECOSYSTEM RESEARCH CONSORTIUM
THE OHIO STATE
UNIVERSITY
At a Field Hearing before
the
United States Senate
Committee on Environment and Public Works
Cleveland, Ohio
5 August 2002
“The Dead Zone in Lake
Erie: Past, Present and Future”
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 anoxia in the middle of Lake Erie, the
so-called “Dead Zone.” 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.
But first, 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, 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 corrective actions and take them.
Finally, we must recognize that Lake Erie may be a model for many other
bodies of water in this country, and we must transfer the knowledge we gain
from this lake to prevent the same thing from occurring in other locations in
this country.
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 212 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 the Lake 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 between 60 and 80 feet and the bottom is very 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 around September or October.
In Lake Erie, the thermocline usually forms
around 45-55 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.
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 anoxia, 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.
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 they are currently funding 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.
We believe the oxygen problem is real and
that it is growing. We believe it is
caused by excess phosphorus, but we also believe zebra mussels and quagga
mussels are having an impact because they appear to alter the way phosphorus
cycles through the system. I also wish
we had better loading estimates for phosphorus, because it is possible that
loads are increasing.
Finally, I must mention global warming and
climate change because that is also exacerbating the dead zone problem in Lake
Erie. When I first started working on
this lake, water levels were increasing and we often said, “dilution is the
solution to water pollution.” This is no
longer the case. Since 1997 the water
level has gone down by 3-4 feet. We are
currently near the long-term average water level for Lake Erie, but we are
lower than we have been for over 30 years.
This is important because this reduction comes primarily from the
hypolimnion (the cold bottom layer).
Therefore, as the water level goes down, the volume or thickness of the
hypolimnion is reduced, the oxygen reservoir in the hypolimnion is reduced,
and, as a result, the area of anoxia will increase and last longer each
year. This will hurt fish populations,
the charter and commercial fisheries (Lake Erie supports the largest freshwater
commercial fishery in the world), our boating and tourism industries, and
public health.
As for my predictions for this year, I hope I
am wrong, but I fear that this could be a very bad year. We had a very wet spring. This means we probably received large
loadings of phosphorus from agricultural runoff and from sewage treatment
plants—many of our systems still have combined storm and sanitary sewers
allowing untreated sewage and the nutrients it carries to enter the Lake every
time we have a storm. Water levels have
remained very low so the hypolimnion will not have a large reservoir of
oxygen. Together these things mean we
could experience a very large dead zone.
We need your support to rapidly do the
necessary research to confirm our beliefs about this situation. The current GLNPO study should be expanded
and continued for at least two more years.
We also need to accurately measure phosphorus loading to all of the
Great Lakes on a continuing basis. We
need research to determine how best to reduce phosphorus loading. We need to prevent future introductions of
aquatic nuisance species. We need to
determine if there is a link between the dead zone and the botulism problems we
are observing in the Eastern Basin. We
need to do the best we can to solve these problems with our current
technologies, but we also need support for research on new technologies
to: address the oxygen problem, control
zebra mussels and other aquatic nuisance species, remove nutrients at sewage
treatment plants, reduce agricultural runoff, etc.
I believe Lake Erie is the sentinel and we
should develop models to extrapolate our results to other bodies of water that
contain mussels so they can be prepared for the problem and take preventative
action before it occurs.