cc >> I've been doing aquatic
science for a number of years. And every once in a while,
we get opportunities to speak to the public and often
the attendance is fairly low. But I have discovered over the
last year or so, that if you really work on an issue
like stinky algae, you do get much better attendance
for your talk. ( laughter )
And it's gratifying. Thanks for your invitation
to speak. The title of the talk is,
"Nuisance Algae in Lake Michigan,
and What Makes It Grow." What you'd probably rather see
for the title is what makes it not grow, because that's really
one of our objectives. But I think by understanding
what makes the nuisance algae grow in Lake Michigan,
we can also get at the issue of how we might be able to
reduce that growth and make the problem a little bit
more tolerable. ( inaudible )
Can everyone hear me okay? Is this volume okay?
As most of you know, there's a number of problems associated
with Cladophora. The one that most people
are aware of is the aesthetic problem.
Here's an example here, closer to Milwaukee, it looks terrible
and once it starts rotting, it smells terrible.
There's other problems associated with it as well.
It can clog water intakes, a number of power plants, both
here on Lake Michigan and other parts of the Great Lakes have
actually had to be shut down because of having their
water intakes clogged with Cladophora.
And we're also starting to see botulism in the Great Lakes.
It's been in Lake Erie for a number of years.
It's starting to become a problem in some parts
of Lake Michigan now. We're not sure, but
the hypothesis is that it's ultimately linked to Cladophora,
which can promote anoxic conditions in the sediment,
which promotes the production of the botulism bacteria.
And it's also a nuisance when you go dive, because stuff
tends to get snagged up. When we started looking
a number of years ago at the Cladophora problem, we said,
well, let's look at what Cladophora needs to grow, and
look at the history of those environmental factors and see
if we can figure out what has changed over the last
10-15 years that may be causing the excess Cladophora
that we're seeing now. So if we consider what
Cladophora needs to grow, it needs a hard substrate.
And on this side of the lake in Wisconsin, we're either blessed
or cursed, whichever way you want to look at it, with lots of
rocky bottoms. The Michigan side of the lake
doesn't have nearly as much, and therefore Cladophora isn't
nearly as big a problem there. You need nutrients.
And in Lake Michigan, there's excess of all nutrients
except phosphorous. Phosphorous is at very low
concentrations in Lake Michigan, so that's the nutrient that
controls the growth of most algae in Lake Michigan.
And like for any plant, you need light.
Then the optimum temperature, which for the Cladophora is in
the 13-17 degrees Celsius range. So our research started
by looking at these factors in Lake Michigan, and how they
currently control Cladophora, and how they may have changed
in the past. So two key questions that are,
what are the roles of nutrients, light and temperature in
controlling Cladophora growth; and how have those changed
in the last 10-15 years in a way that may have caused the
increase that we're now seeing. And the way we did this, was
we did research both in the lake and in the laboratory.
In the lake, we did a lot of monitoring of those conditions,
light, temperature, nutrients, and monitoring of Cladophora
itself, to see how Cladophora nutrient status and
Cladophora growth changed in time
in relation to these variables. And one thing we were trying
to do is to develop a model that links Cladophora growth
to those variables of phosphorous loading,
and light and temperature. This is a conceptual diagram
of the model. Those three variables determine
the dissolved phosphorous concentration in the lake,
which then becomes stored phosphorous within
the Cladophora algae itself. And that, combined with light
and temperature ultimately determine the growth and
the biomass of the Cladophora in the lake.
Now this is a model that a professor at Michigan Tech
developed for Lake Huron back in the 1980s, when
Cladophora was a problem there. We're taking that model now,
and trying to make it work for Lake Michigan working
with that professor who's still at Michigan Tech.
One difference is that when this difference was first
developed, there were no mussels in the Great Lakes.
And now we have lots of mussels. And mussels may influence this
model, because they are a source of phosphorous.
Mussels eat the plankton, and then they excrete the
phosphorous, which in turn can become available
for Cladophora. Mussels and Cladophora
live in the same habitat, in the near shore area,
on the hard, rocky bottom. So they live in close proximity
to each other. So what we're trying to do now
is incorporate this into the model to see how mussels
are also potentially influencing Cladophora production
in the lake. Now here's an example
of a model. This is the front face
of the model. There's a number of places where
you provide input to the model, temperature, light, dissolved
nutrients, and so forth. And then this is the front
of the model, where you provide a few variables here.
And then you can run the model, and it provides graphic output
here. And you may have trouble reading
this from the back. But this is the key graph
we like to focus on. This is biomass Cladophora
and this is --. This is running right now
from around early June, up until late September
or October. These points you see here
are actual measurements in the lake.
We go out into Lake Michigan. We measure the biomass
of Cladophora. So we're comparing those points
to what the model is telling us should be out in the lake
based on light, temperature and nutrients.
And you can see that, through this growth phase from May
until around the end of July, the model does fairly well.
There's not a lot here, but the general increment in Cladophora
is simulated fairly well by the model.
Later on in the summer, the model doesn't do so well.
This is what we call a sloughing phase.
The Cladophora's breaking off now.
This is a problem time, when it's coming up on shore.
It's breaking off. The model doesn't really account
for that breaking off, because we still don't really understand
the processes that cause the Cladophora to break off.
But if you think about it from a management perspective
this is stuff that's breaking off, because it's
growing out in the lake. If we want to manage Cladophora,
we should be looking at this part here, because we want to
stop the growth of Cladophora in the first place.
And in that growth phase, the model is doing fairly well.
So right now, at least for the conditions under which we
calibrate the model, it seems to simulate growth pretty well,
so we can start using it to look at these different factors
and see how they control growth in the lake.
Well, first we look at the role of temperature.
If we look at the history of temperature in the near shore
of Lake Michigan, this is what we've seen
over the last 35 years. This is just the June to August
average temperature, so summer temperatures.
There's a lot of noise in here. But in general, the temperature
has been increasing over the last several decades.
I won't go into all the details for why that's occurring now.
It's not so much global warming, as it is a change in wind
directions over Lake Michigan. The question is, could this be
responsible for an increase of Cladophora in the lake.
So if we use the model, and we put some different
temperatures in the model, this is what we find.
At 5 degrees, 10 degrees, 15 degrees Celsius, the model
is over a 200-day period and we see biomass increasing.
But at all those temperatures, the maximum biomass
is roughly the same. And when we start to get
warmer temperatures like 20 degrees and 25 degrees,
which is essentially room temperature, we actually
see biomass coming down. And that's because at those
warmer temperatures Cladophora respires more.
And it respires more than the photosynthesizing,
so it burns itself out. The Cladophora does best
at cooler temperatures, but we're seeing this shift
in Lake Michigan from an average temperature of around
8 or 9 in the summer to maybe around 12 now.
And what this is suggesting is that within that range,
that temperature change probably isn't causing a lot
of the change that we're seeing in Cladophora.
So we don't think, even though the near shores are warming up,
we don't think that's playing a big role in the Cladophora
problem right now. What if we look at the light,
the history of light. Well, here's light at a depth
of nine meters in Lake Michigan. This is in the summer of 2006.
This dashed lined here is the line that is
the threshold for Cladophora. If you're below that, Cladophora
has a tough time growing. If you're above that,
it's happy. And what we can see
at nine meters is that in July, you're border line.
As we get into August, September, we have sufficient
light for Cladophora to keep growing.
This is again at a depth, I think it's actually nine meters
where we had this light meter. It can grow down to 10 meters,
or a little bit deeper than ten meters.
If we look at the history of light in Lake Michigan.
This is the history of a disk that we put into the water
and you just drop it till you can't see it anymore.
And so the deeper the depth, the clearer the lake is.
This is data collected over the last 12 years.
And back in the early 1990, the disk depth was around
three meters. That's steadily increased
over the last decade and a half, and this is going up to 2002.
This trend has increased so that water clarity now is about
three times as much as it was back in the early 1990s.
One reason is the mussels. We had the zebra mussels
coming in in the early 1990s. Mussels are great filtering
machines. They pull all plankton
and particulate material out of the water column,
thereby clearing up the water. So the water is much clearer now
than it used to be, thanks to the zebra mussels.
And now quagga mussels, which have largely replaced
zebra mussels. Here's just an example of that.
This is just some water that I took from Milwaukee harbor.
I stuck it in two bottles. In one, there are zebra mussels.
I let it sit for 30 minutes, and took another picture.
And you can see here this jar has cleared up a little bit,
but you can see how clear the water has gotten
in this jar. That's because the mussels here
just filter the all of that stuff out of there.
And they're doing the same thing in the lake.
So if we back track, and we take that water clarity back
from the early 1990s and plug it into,
basically we take 2006 data, and say how much of that light
in 1991 would have gotten to the bottom of the lake
at nine meters. This is what we see.
Here's 2000, sorry, this is 2004.
This is 1991. In 1991, we would never have
had enough light at nine meters for Cladophora to grow.
But you do in 2004, because the lake has cleared up.
So it looks like light is potentially important factor
responsible for the increasing Cladophora that we've seen.
What if we look at the third factor, which is phosphorous.
This is total phosphorous concentrations in Lake Michigan.
This is from the EPA monitoring program.
This is from 1983-2005. And a slow decline over time.
The target set for Lake Michigan for total phosphorous
concentrations set by the Great Lakes Water Quality
Agreement is seven micrograms per meter.
And we're well below that now. This is for open waters
in Lake Michigan. So we've met the conditions of
that target, and yet we still have this Cladophora problem
near shore. If we look in the near shore
area, which is not the same as the offshore, here's
some data that I collected. I got it from MMSD, who has been
monitoring near shore around Milwaukee for a number of years.
What you see here is that it was actually declining near
shore up until the '90s, but in the last five to ten years,
there's been quite an increase in the near shore concentrations
of phosphorous. The near shore, at least now,
looks like it's a little bit above that Great Lakes Water
Quality Agreement. So the targets have been met for
offshore waters, but it looks like they're still exceeded
at least some of the time for near shore waters.
So the question is, is that increase in phosphorous
in the near shore potentially contributing
to the Cladophora problem that we're seeing now.
Now we have this history of light.
We know the temperature change over time.
And we have data on phosphorous change over time.
We can plug that data into that Cladophora model I showed
you earlier to determine how those three factors work
together to change Cladophora over time.
So this is using conditions from pre-mussel era,
from the late 1980s, using phosphorous, temperature
and light from that era. Then we say, let's put in this
increased dissolved phosphorous I've just showed you,
and see what that would do to the Cladophora biomass.
It raises this a little bit, but not a lot.
What if we just take the post-mussel water clarity,
so this is like 2006 water clarity, and put that
into the model, but keep everything else the same
as it was before the mussels. Now we see Cladophora abundance
really shooting up. So it looks like light is having
a much stronger influence than phosphorous alone.
When we put the two together, this is what we get.
So now we're getting three times as much Cladophora as we were
pre-mussels, due to this combined effect of greater
water clarity and increased phosphorous concentration
in water. Now the next question is,
can we manage this? Can we do anything about this?
Well we can't do a lot about water clarity unless somebody's
willing to fly over the lake every weekend and dump a lot of
dirt or something in the lake. It's not really
a feasible option. Really, it's the only option.
We can't do much about temperature.
The only option we have is to look at phosphorous.
And that's how the lake has been managed
for the last several decades. So if you go back to the model.
And what we want to do is to try to get this line here
to flat line. We'd like to see no increase
in Cladophora over the summer. Well, one thing you can do
in the model is that there is a phosphorous multiplier here.
And we can change that so that it takes all the input data
that we provided and multiplied it by that number.
So it allows us just to theoretically reduce
the phosphorous concentration and see what would happen
to the Cladophora biomass. So here we've run it at 1.0,
using real data for 2006. We can reduce that to .75
to see what it does to Cladophora biomass.
What you see is that it starts to come down, but it still
does continue to grow. Now remember this is all at
a depth of nine meters, because that's where we
collected most of our data for. Now if we reduce this to .5,
that's the point where, at least at nine meters,
we see biomass flat line. There's no growth or increase
in Cladophora over the summer, because phosphorous is too low
for it to grow very much. So at nine meters, if we
reduce phosphorous by 50%, we could pretty well stop
the growth of Cladophora at nine meters.
But you have to look at the whole near shore area.
Cladophora grows from close to shore to a depth
of about 11 and 12 meters. And we have to consider
that whole zone when we're thinking about how Cladophora
is going to respond to changes in phosphorous.
So here is a graph from two meters down to 10 meters,
of how Cladophora would change in response to these reductions
in phosphorous. So here's 100%
of this 2006 data. Here's 75%, 50% and 25%.
If we look just at our reference depth of nine meters,
here's what we're calling the preferred Cladophora abundance.
Now this is not, we haven't put a lot of work into saying what's
the ideal Cladophora biomass. But this is a number the
Michigan Tech professor chose when he was doing work
on Lake Huron back in the 1980s. And so if we use that for now.
He said 50 grams per square meter would be
a nice target to shoot for. Well, at nine meters, if we
were to reduce phosphorous concentration by 50%,
we get down to that level. You can see at shallower depths,
even if you reduce by 50%, this will still be well above
that level. In other words, one thing
to remember here about models. A famous statistician
who started at England and actually finished his career at
UW Madison, he said all models are wrong,
some models are useful. The reason for that is
no mathematical model can ever really account for
the complexity of the natural environment.
There's a lot of things going on out there that may influence
Cladophora growth, but we don't include them in the model,
because it's just too difficult to account for everything.
And so we have to be careful when we use these models
to look into the future, or to understand Cladophora ecology.
And one example is looking at this depth distribution
of Cladophora that is put out by the model.
In reality, we may see something like this.
Because as you get into shallower waters, there's more
wave action. There's more turbulence.
This Cladophora is broken off the rocks more frequently.
That doesn't happen out at these depths,
but it may at these depths. And some evidence for that
is a few years ago, we did depth profiles of Cladophora
in the lake. Here's a depth of ten meters,
which is close to our model depth.
Here's five meters. The model says we should have a
lot more biomass at five meters. But in fact, we didn't.
It was almost the same as ten meters.
That's somewhat encouraging, because then if we go back to
what I just showed you, maybe the results that we're seeing
here, as a result of phosphorous reductions, maybe we also
see them at shallower depths, as well.
But we have to do a bit more work at shallower depths to see
how well this model will work at shallower depths right now.
But that's just a precautionary note, that you always have to be
careful using these models. Nothing beats real data
from the environment. So now, we've looked at
some possible effects of reducing phosphorous.
If we want to reduce phosphorous in the lake, then we have to
ask ourselves, where is it coming from?
Could we actually reduce phosphorous concentrations
in Lake Michigan. There's a few possible sources.
It may be coming from rivers, from the land being
washed into the lake. Or within the lake,
you've got the mussels. Mussels are eating particular
phosphorous in the form of plankton and other particulate.
And a lot of that is excreted out as dissolved phosphorous,
which is the form that Cladophora needs.
Mussels also may be providing the phosphorous that's needed
for Cladophora growth. So what we did was say, let's
take these rates for a certain stretch of Lake Michigan.
Let's take the stretch between Fox Point and Wind Point, and
let's look at the phosphorous excretion by mussels
in that area. Let's look at the uptake
of phosphorous by Cladophora in that area to see how it
balances. Let's also look at
the phosphorous input from the river and compare those
three numbers to see what's the most important.
Cladophora uptake, we estimated that around 119 milligrams
of phosphorous per square meter. The river input
is around the same number. Theoretically, there's enough
coming from the river to support this, but the Cladophora
isn't 100% efficient. It's not going to grab
all of the phosphorous coming into the river.
A lot of it gets out into the open lake.
We know that mussel excretion, at 506 milligrams
per square meter. This is the relative importance
of phosphorous flowing from the river to the near shore region.
And that importance changes as you move away from the river.
When you're really close to the river mouth, obviously
the river is an important source of phosphorous.
As you move away from the river mouth, mussels start to become
more dominant. So when you get 20-25 kilometers
away, less than 10% of the phosphorous in that area
would be coming from the river, and over 90% would be coming
directly from mussel excretion. So a lot of the parts of the
lake fit into this category. If you're not close to any
major river, mussels are going to be the dominant source
of phosphorous. Why is that?
We're not sure, but there's a couple of possibilities.
You see here in May and June of 1996-2001, we don't have data
beyond that yet. But we had higher phosphorous
concentrations in the spring of this area
than we did previously. So we're getting a spring
slug of phosphorous. If we look at river discharge,
we're seeing the same thing. In May and June of this
most recent era, there's more water from the phosphorous
concentration. So we're getting this big
slug of phosphorous coming into the lake during the spring,
just due to weather conditions over the last few decades.
What's another possible cause of increased input from rivers?
It may be phosphorous in the soils.
This is phosphorous content of soils through Wisconsin
cropland. Just going up to '99.
What you can see is that the steady increasing trend.
This is higher than what most crops need.
But because of fertilizer and the newer applications,
our croplands are continuing to increase in phosphorous
concentration. This is the soil
storage change. What this is, is just the input
minus the output. When this reaches zero,
that means we've got a balance. But as of 1995, we were still
putting more into the soils than we were taking out of them.
Just to show you, I showed you earlier the phosphorous trend
for the Milwaukee River. Here's the trend
for the Manitowoc River. It came down until
the mid-1970s. It hasn't done much since then.
It's stayed pretty steady, averaging around .2 or .25,
which is higher than the Milwaukee River.
The Milwaukee River now, even with that increase,
is more around .15. So fairly high concentrations
of total phosphorous in the Manitowoc River.
We've got particulate phosphorous
and dissolved phosphorous entering our rivers.
That dissolved phosphorous can be taken up directly
by the Cladophora. The particulate phosphorous,
they can't use, or if it's fed on by mussels, they're going
to excrete some of that as dissolved phosphorous,
which is available to the Cladophora.
We also have what I'm calling the offshore loop.
A lot of this phosphorous can just bypass the near shore zone
and go right out into the open waters.
This is dissolved phosphorous where it becomes taken up
by plankton. Eventually that plankton may
come back to the near shore, where it's fed on by mussels,
and then made available to the Cladophora.
And what we want to know is the relative importance
of these two loops here. This is important to consider,
because there's a huge mass of phosphorous in Lake Michigan.
There's much more phosphorous in Lake Michigan
than what enters the lake on annual basis from the rivers.
So there's potentially a huge amount of phosphorous from here
that could be promoting Cladophora growth, if it's being
funneled in by feeding from mussels.
And it's important to know the relative importance of these
two loops, this offshore loop and this near shore loop,
because if we reduce phosphorous inputs into Lake Michigan,
if we were, by some magic, able to reduce phosphorous
by 50% in all of the rivers entering the lake tomorrow,
then if the near shore loop was dominant, this is
what would happen to phosphorous concentrations
in the near shore zone. Within a year, they would drop
down and we would get that 50% that we would like to shoot for.
It would happen very quickly. But if that phosphorous is
flushing out into the open lake, and we've got a way for that
phosphorous to be reduced in the open lake,
we're going to have to wait a much longer time.
Because, as I said, there's a huge pool of phosphorous
in the open lake. It's going to take a long time
for that respond to any decrease in phosphorous
coming from the rivers. This is the time span
we're looking at there. We're looking at a ten year
time span to get lake concentrations down by 50%.
That's based on the Lake Michigan program model
that was produced back in the '90s.
So to conclude then, the main points.
The primary factor responsible for the recent increase
in Cladophora, is the big water clarity.
There is a contribution from increased phosphorous inputs,
but the main factor is water clarity.
A secondary factor is increased phosphorous concentrations.
And mussels, appear to be the main source of phosphorous
within the near shore area. We have this increase
in water clarity. Like I said, there's nothing
we can do about it. We've got this target level
of seven micrograms per liter of total phosphorous
in Lake Michigan. And yet we still have
a Cladophora problem in the near shore waters.
What I'm suggesting is that this change in water clarity
is forcing us to reconsider this target level,
because it's not working for the near shore waters.
We may have to set a new target for the near shore waters,
because those waters are more clear now.
The greater light abundance has overbalanced our phosphorous
management strategies. The Cladophora models suggest
that at depths greater than seven meters,
50% phosphorous reduction would result in a significant
decline of Cladophora abundance. At shallower depths,
the response is less certain, because we're not sure yet
how well the model works at shallower depths.
Finally, reducing phosphorous concentrations in Lake Michigan
is a long-term process, for two reasons.
One is, as I just mentioned, the lake is this big giant.
It's going to take a while to respond to anything we do
in the watershed. The other reason, I showed you
earlier, we've been increasing phosphorous concentrations
in cropland soils. And that's this huge mass of
phosphorous where, it's a legacy that we're going
to be living with for a while. Even if we change our management
practices right now, there's a lot of phosphorous
in the soils that's going to keep coming
into the rivers and lakes over decades
and even centuries to come. And I'll finish with that.
( applause ) >> Interesting presentation.
But one piece that seems to be missing from here is sewage.
You never mention sewage. We all know about the sewage,
particularly in Milwaukee and other major cities
around the Great Lakes. They've been dumping billions
of gallons in. And we all know it contains,
it's very phosphorous laden. So why isn't that part of your
study and part of the solution? And secondly, probably a minor
part of it, those little white birds that fly over everywhere,
those two-legged poop machines, better known as seagulls,
are just out of control around the Great Lakes.
And a lot of beaches have been closed because of that, and you
haven't looked at that either. I suspect that's minor compared
to the sewage, but those two things seem to be missing here.
Right. They're both certainly issues
when we think about beach water quality,
beach closings and so forth. They're very relevant issues.
With regard to Cladophora and to phosphorous cycling
in Lake Michigan, sewage may be an important
local issue. But in the larger scheme,
even not all of Lake Michigan, but just for example,
the area I showed you from Fox Point to Wind Point.
The sewage contribution to phosphorous flowing into
that area is negligible compared to all the other
phosphorous inputs. Even if we ignore the mussels,
just the loading from the river, the majority of phosphorous
is coming from the river, from surface run-off from the land.
I intentionally don't emphasize sewage in here, because
my concern is that I think a lot of the public has been misled
over the last number of years, because the media has given
a lot of attention to sewage overflows, and that's
understandable, because there is a health threat associated
with that. But that is not contributing
to the Cladophora problem in Lake Michigan.
You can go to Manitou Islands and Sleeping Bear Dunes National
Park on the other side of the lake, which are ten miles
offshore, and their Cladophora problem is as bad as many other
parts of the lake on this side, and there's no sewage input
there. It's in-lake processes
that are causing the problem that we're seeing there.
So I'm trying to correct the perception that a lot
of the public have that sewage is contributing to
the Cladophora problem, because it really isn't.
The bird issue, again, is an obvious health issue.
And it ties into the beach closing problem.
But with regard to Cladophora, and with regard to phosphorous
increase to the lake, it's really not
an important problem. Cladophora does tie in there
in that the bacteria can come from birds or other sources.
They tend to persist longer in Cladophora, so it confounds
the whole process of trying to define water quality,
because we use those as the main indicator of water quality.
And if you have this reservoir of bacteria in the Cladophora
that's either in the water or sitting up on the beach,
that confounds the process of monitoring bacteria in water,
because they may be leaching out of this Cladophora
over a longer period of time than if you had no Cladophora.
Are you getting less ( inaudible )
from the mussels, because the water is clearer, and
there's less biomass available for the mussels to filter.
There will be a negative feedback there.
Eventually, they may eat themselves out of
house and home, so to speak. The measurements we have been
making over the last two years, where essentially it looked like
mussels have done everything they can in the near shore zone.
They really have cleared up the water, they've reduced
the amount of plankton there. So I think the measurements
that we're making now are representative of the conditions
you're describing, where they're doing as little as they can
right now. We don't have historic
measurements in Lake Michigan to say five or ten years ago,
where the mussels excreted more phosphorous than they are today.
But I don't think it will get any less than it is now, because
they've kind of reached that climax stage of their impact
on the near shore environment. >> In this area, most of the
phosphorous seems to be coming from the farmlands.
And what would be, to get a 50% reduction,
what exactly has to be done? >> I'm probably not the best
person to address that. Most of our work is focused on
the lake itself, and what's going on in the lake,
looking at phosphorous with an interest in the lake
and the rivers. We haven't gone much upstream
in the rivers to figure out where is this phosphorous
coming into the rivers, what are the sources,
which we need to do to really start targeting
sources that we can manage. And I'm not an expert
in that area. We do know that a lot of it
does come from non-point agricultural run-off.
Or we've done some work in the Milwaukee River
that shows that urban sources are also significant.
If you look at phosphorous concentrations as you go down
the Milwaukee River, there's a significant increase when
you get into the metropolitan Milwaukee area.
So there are sources there as well, which again,
we're guessing at now, but we're not definite
on what they are. I would just say that we still
need to be concerned about the Soil P content, which is
increasing, still going up. We need to get that
Soil P concentration down. And we obviously
need to reduce run-off. I think there's a focused way
to do this. And I know that folks
at UW Madison are working on how we can highlight the
hot spots for soil phosphorous run-off in agricultural land.
Rather than applying a strategy to all agricultural land,
try to identify the hot spots and focus your management
on those hot spots to reduce erosion and run-off
from those hot spots. >> Is there a possibility,
is there something that can take care of the mussels?
Some people have worked on that, with limited success
so far, looking at pathogens that might work on them.
There are chemical ways to control them, but in a lake
as large as Lake Michigan, those are not options.
To my knowledge, there's no promising pathogens
right now that we would put into Lake Michigan
to try to control mussels. I should mention, though,
in regard to that, that mussel numbers fluctuate
from year to year. They're still relatively new
in Lake Michigan. We may see mussel numbers change
over the next five to ten years. Gobies are becoming more
established in Lake Michigan, and they feed on mussels.
They may put a dent in the population.
Other natural mechanisms may reduce their numbers, as well.
We haven't monitored within the last couple of years,
but based on our data, it looks like there are fewer mussels
now than there were two or three years ago.
We know there are hot spots along the lake shore, where
Cladophora is a big problem. Bradford Beach is a problem.
Despite the fact that Cladophora is growing all along
the lake shore, and the reason for those hot spots, I believe,
is because of near shore hydrodynamics, which force
the Cladophora to accumulate in certain areas
along the shore. There may be some management
option there, but I think ultimately the management option
is to reduce the amount of Cladophora that's growing
in the lake. If I could just mention
one more thing. This problem is also occurring
in Lake Erie and Lake Ontario, even more so than it is here, to
the point where people have to move out of their homes
for part of the summer in New York on Lake Ontario,
because the smell is so bad. The Corps of Engineers
did a large study there in Monroe County
to look at options to manage the Cladophora.
And they were all engineering options, trying to remove it
when it came up on the beach, trying to get it even before
it came up on the beach by pumping it away.
And in the end, none of them worked.
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