University Place

Okay, my name is Reesa Evans. I will be moderating most of the ecology stream for the next couple days. I'm going to introduce Buzz Sorge, who I don't have a written introduction for, but I've known him a long time, so... Buzz is the lake manager for the West Central Region, which is where I am, and he has been an innumerable resource for me through the years as I've learned lake science. So when I have a question, I go to Buzz, and when he retires, I'll be in big trouble. Thanks, Buzz, go ahead. Well, good morning, everybody. Thanks for coming in this morning. How many people understand what the term limnology means? Well, limnology is the study of fresh water ecosystems, and it incorporates an understanding of the biological, physical, and chemical factors that influence our rivers and lakes and streams. So what we're going to be talking about this morning is the basics of lake health. What makes a lake a lake? So when we start thinking about this, we have to think about Wisconsin as a state. Well, how did we get all this fresh water in our state? Well, it's really a product of the periods of glaciation that came through the state and we really have what we estimate as somewhat over 15,000 natural lakes and tens of thousands of miles of rivers and streams. And so as the glaciers came through this country, they gouged out portions of the earth and created these basins then in our natural lake ecosystems that filled with water and created those lakes we love to recreate on. So when we think about the history of these lakes across the state, you know our lakes are 10,000+ years old, so what has been our impact on them? We really started impacting our lakes in Wisconsin about 150 years ago, just before the cutover, when we took the pine off the northern parts of the state and the woods off, and as Europeans colonized. So some of our earliest lake users and development on lakes goes back to the mid-1800s, and that's when the forests were clear cut. But then really, most of the development started on Wisconsin's lakes post-World War II, when we had those resources in our economy to enjoy those systems out there. So I'll talk more about that later with that type of development, and then redevelopment really came significantly as a lot of those cabins were upgraded to the second homes and first homes in the 1990s. How do we value our lakes? And lakes do provide services to us as a society, they provide ecosystem services, I mean, we love to be near our lakes. We are a creature that just loves to be near water, and so the cultural and societal values we have for lakes, but these ecosystems services, the wildlife, the clean water they provide, are very valuable to us, especially in the Upper Midwest and Minnesota and Wisconsin. But our lakes are changing faster than ever. Some of these are indexed by more frequent algal blooms. How we've developed our shoreland areas has really impacted in lake habitat, and aquatic invasive species. These are the three main stressors that we see on Wisconsin's lakes today that we are working on. If we think about this, I don't know how many folks have had a chance to look at this report, but it's Wisconsin's Changing Climate report, it was published in 2011, and really gave us some insight, so what we can expect to see, especially how it impacts our water resources. Some of these major drivers of climate change on our water resources are simply thermal impacts. We're a bit warmer. That means ice on for a shorter period of time. It comes on later, goes off earlier in the spring. Definitely, I think folks who live in, especially north central and northwestern Wisconsin, the drought we went through 6, 7 years ago. We're kinda out of that, but it really impacted lake levels up there. We had many lakes that really had significant impacts on their lake levels, and then in many other areas of the state we've seen increased storm densities. In western Wisconsin when I worked, 2014 and 2013 especially we had some incredibly intense early summer storms that leave 5 inches, 6 inches of rain in a few hours. And we had multiple storms like that come through our area. Some of these key water resource impacts

associated with these changes

in those wetter areas we definitely see increased flooding. And in our reservoir ecosystems, this is a big problem for them. Increased frequency of harmful algal blooms in some of these systems, with those increased flooding comes increased pollutant load to those systems. And then, these warmer summer temps. I think if you think back, especially to 2014. In August we were seeing surface temps in our lakes pushing 90 degrees, that's very abnormal for Wisconsin lakes. Conflicting water use concerns, when we get into some of these drier areas, especially in more of our agricultural areas, we have that competition for that ground water especially to grow our commodities, and then we're seeing impacts on lake levels and stream flows associated with that. Changes in water levels, I talked a bit about that, especially in the north when we're in the drought period. Increased sediment and nutrient loading, this is very much associated. We put more water on the land, we got the ability to transport more pollutant loading to our lake resources. And increased spread of aquatic invasive species. As we're changing these water temps, we're changing the characteristics of these lakes that can support new species. And it's very common for somebody to be fishing either on the Mississippi River, the Great Lakes, or on another state, and then the next day, be on a northern Wisconsin or southern Wisconsin lake. So we have the vector transport because of how mobile we are in society today. This is just some examples of some of those things I was just chatting about. Be it a very high level of nuisance, blue-green algal growth, or increased sediment loading. That's a shot on Lake Mendota with a stream coming in carrying a very high sediment load. So as we kinda flip the switch a bit, what makes a lake a lake? So we really have to understand these physical, biological, and chemical properties. But when they're in proper balance, that's when we are at that state of high quality lake health. And so, often our goal is to either sustain a lake in high quality lake health or restore its lake health. So let's talk a bit about the physical properties of lakes. We really have to start with physical property of water. Water is a pretty unique substance. It is a universal solvent, so lots of stuff will dissolve into water, but its physical properties are most unique because water actually weighs the most at 4 Centigrade. And that's like many other chemical constituents, when you heat them up they get lighter. Well, not so much with water. So as you cool water down, it gets lighter, and that's a very good thing, especially in Wisconsin and the Upper Midwest, cause that's what make ice float, simply. So and we don't have a lot of this fresh water on the earth's surface either, less than 1% of the water on the planet is fresh water, and then about 1/1000 th of that is actually in our earth's freshwater lakes. So these are very, very unique water resources that we have in Wisconsin. So thinking a bit about water then, you have to understand a bit about how does that water get to the lake and why does that lake have water in it? So we think about the hydrologic cycle. So in Wisconsin, we get about 30+ inches of rain a year. As that falls to the earth, some of that is intercepted by vegetation and evaporates right back up. Some of it falls on our lakes and streams and evaporates back up, and some of it that seeps into the earth, is taken up by the plants, and then evapotranspired back by plant growth. But when we think about these lake basins out there, as the glaciers did gouge these holes in the earth's surface they simply filled with groundwater. So when you see a lake, what you're really looking at is the interception of that lake surface representing the ground water table in that area. So as far as lake types in Wisconsin, we really can classify them often by their water source, and so we have seepage lakes, groundwater drainage lakes, drainage lakes, impoundments, and then oxbow lakes. A seepage lake is where an ice block was gouged into the earth's surface, created this depression in the earth's surface, and then as the glaciers receded, it simply filled with groundwater. And the major source of water to our seepage lakes is groundwater, we have no streams coming in or out, generally have groundwater coming in one side of the lake and going out the other. And so some of these lakes are some of our lakes that are most susceptible to water level fluctuations during periods of drought, because if we aren't getting that rainfall on the earth's surface, then those groundwater levels go down and that's characterized in our lake levels. The other thing that happens on these systems too when we're in drought-ier periods, the evaporation actually from the lake's surface exceeds the amount of rainfall. So if we're in a 20 inch, 20-some inch rainfall year, and our normal is like 34 inches, 32 inches, something like that, in a warm summer we might have an evaporation that exceeds 30 inches on that lake's surface. So the water budget becomes out of balance and then our lake levels go down. This is just a shot of a piece of landscape up in Chippewa County, where I work, where the glacier left many of these small ponds and lakes across the landscape. The lake in the central portion of the photo there is Round Lake. Has no inlet or out, Round Lake, and really it's just groundwater coming in largely from the north, the top of the photo and out the side, and it just represents that groundwater level in the area. Groundwater drainage lakes, these are lakes that are placed high up in the landscape but there's enough water coming to them from the groundwater that they've created an outlet. And so they definitely are dominated by groundwater coming through the system, but they also have a stream leaving them. A good example of that is Sand Lake, up on the Rusk/ Chippewa County border. This lake gathers the groundwater from the groundwater shed around it and then flows out to the Chippewa River to the north. Drainage lakes, now we're changing things up a bit. These types of lakes, where they're more dominated, their water source, by surface water, and groundwater's less influential on the characteristics of the lake. So we got a stream coming in, stream going out, and because of that we have a larger catchment, a larger watershed that's bringing water to the lake, and I'll talk more about that. And as you think about this, a seepage lake often has a very small catchment, and they tend to be our higher quality lakes. Those are most of our clear water lake systems across Wisconsin. And we get into our drainage lakes. These are a bit more productive, and often water quality is a little bit less than what we see in our seepage lakes. This lake is Long Lake up in Chippewa County. It's a pretty unique lake ecosystem, and I'll talk more about it's physical nature, but it drains a stream in from the bottom of the photograph, up into the shore of the lake, and then it goes out through another lake chain over to the Chippewa River also. It'd be a surface flow. Alright, impoundments are what we have lots of in Wisconsin, or reservoirs, they are referred to. And they're not really lakes-- they're dammed up rivers. These are often some of our more significant management challenges, because we're really taking an ecosystem function of the river, which is to transport material out of a watershed, and we're stopping that function and creating the surface water body. This is Lake Altoona on the east side of Eau Claire, Wisconsin, and it's a lake that I've been engaged with management over the last 30 years of my career. The Eau Claire River is a very high sand port, sand transport system. When we first started looking at this lake back in the early '80s, the delta had moved about a third of the way down the lake. The lake had filled about a third full with sand. Its sedimentation rate was tens of thousands of yards of sand every year. We estimated that as high as 70,000 yards of sand a year were being deposited in this system. It's a huge management challenge. It comes down to, how much does society value this lake? Is this lake going to be sustained as part of the greater Eau Claire community? And the people that lived around the lake have a lake management district, and in concert with Eau Claire County have found the resources. This has just finished another dredging project literally a couple of weeks ago, and it was like the third time it's been dredged, so they're dredging almost once a decade and they took almost 200,000 yards of sand out of this system. And that is just to sustain it as a lake basin. Another interesting lake we have in our area north of Eau Claire, this is Lake Hallie in the village of Hallie. This lake is an Oxbow Lake, it was part of the Chippewa River one time, and at the time of the cutover, when a lot of the water, the timber was coming out of the Chippewa River basin, this lake was used for log storage. And so they put a dam on this system and it's what we refer to as a raised lake. So this lake only has a mean depth of about 9 feet in average depth. But the uniqueness about this lake, up until the mid-1990s it had very, very, high levels of groundwater flow into it. So it's a very shallow ecosystem, we would think it'd be very warm, but it had such high groundwater inputs, we could sustain trout in this lake year round, because on the far end of the lake near the bottom of the photograph, we had very high spring flow into this system and it would keep the water cool enough where it would sustain a stocked trout fishery for the community. And the other thing that that high groundwater flow did in to this system, was it's warm water in the winter. Groundwater's about 50 degrees as it comes in to lake ecosystems, and it kept the upper 20 acres of this lake open all through the winter, no matter how cold it got. Well, as we've developed its groundwater shed, here on the left side of the photograph, a couple of things have gone on. We've put some high capacity wells in to provide water supply for the community. But we've put a lot of impervious surface down, and that impervious surface now is running water off that used to infiltrate into the ground. And we lost our groundwater flow. And the consequences of that have been we are no longer able to, say, net trout, to keep this lake as a put and take trout fishery in the summer so the lake has lost that ecosystem service to the community. Because we have less groundwater coming in we don't keep the lake open anymore in the winter. And in the mid-'90s, when some fishermen were out there, we got some calls in the office and said, "The fish are dying in Lake Hallie." And, sure enough, now this lake, we have to sustain the fishery in the lake through a winter aeration system because we don't have that open water area out there. And I'll talk more about why that occurs in lakes like this. So as we think now more about, that's the lake types we have, we have these physical characteristics that impacts lakes, and we'll talk about mixing and stratification, why lake depth's important, how long water stays in a system, retention time or flushing rate, and watershed or drainage basin area to lake area ratio, where this lake is positioned in the landscape, and influences of watershed runoff. So when we think about mixing and stratification, most lakes in Wisconsin, we call them dimictic. That's simply a term that means our lakes mix, top to bottom, twice a year. So if we think why does this happen, as I was talking about earlier, water is most dense at four degrees, so in the spring where the ice is off, what we see when we're--let's start with winter. As we're coming out of winter, and we have zero degree water virtually on the surface. So that's the lightest water in the lake at that time, that's why that ice is floating. And then as that ice melts, that lake water warms to about four degrees, and once it's the same temperature top to bottom, or what we call isothermal, that lake easily is mixed. So if we put wind energy with our spring wind events onto a lake's surface, then we get the spring mixing event. And we call that spring turnover. And that really rejuvenates the lake, so then our water chemistry in this system is the same top to bottom. It's just like kinda putting a blender into the lake, it mixes top to bottom. So as we come out of spring here, as we approach that time period in a month or so from now, that summer condition begins to set up. As that surface water warms, as that lake temperature warms, that water now becomes lighter water, and it sets up a stratification is what we call it. The lake actually layers into three distinct layers as we go into the summer. So that top layer over there on summer is called a epilimnion, and it's a fancy term for the top layer of the lake, and that layer is really dependent somewhat on the depth of lake, but how warm or cool the summer is. So in most lakes in the summer, that top layer is anywhere from, it could be as little as six feet, or two meters, on some lakes that are very protected that do not get much wind energy on them, to up to ten meters or approximately 30 feet. And then below that is the transitional layer, we call that the thermocline, and any people who love to swim or dive, when you swim down into the lake you'll feel that great temperature change, and that happens very, very quickly. Then our coolest water, our most dense water, stays on the bottom of the lake. So then as we move into fall, as that top layer then begins to cool again, once it reaches four degrees centigrade or 39 degrees Fahrenheit, it becomes the most dense water in the lake so what's it do? It simply sinks. And then causes this fall mixing period that will continue on until ice up. And then again we rejuvenate that whole lake ecosystem. So let's go into, you know, why does lake depth matter? Deep lakes, definitely we'd use this term, they layer up, they stratify, and shallow lakes stay continuously mixed so there's a couple of things going on here that really can influence lake characteristics, especially in the summer and in the winter. In our deep lakes, what's going on, and in our shallow lakes, you think of our lakes again, they're 10,000 years old, right? So we've been growing plants and algae in these systems for 10,000 years, and we've accumulated all this really rich, organic sediment on the bottom of these lakes. Well what happens when you put organic matter and oxygen together, you grow bacteria. Same thing happens in your compost pile in your yard, you're decomposing that, well, that same process is virtually occurring on the bottom of every lake in the state and it goes on 24/7, 365. Well, now does that bottom portion of the lake maintained as habitat or not? Well it may or may not, it depends upon the volume of it and the rate at which those bacteria are consuming that oxygen out of the bottom of the lake. So in our state we only have a handful of lakes where the oxygen concentration remains high enough to sustain a fishery in that portion of the lake as a trout fishery. So that's why we have Trout Lake, Green Lake, are a couple of the more common lakes, that still have lake trout in them. But we also need that oxygen down there for many of our cool water species, especially our walleye fisheries because there's a fish species named cisco that lives down there and they need that cool water place for the cisco to live. That is a very important resource for sustaining many of our walleye fisheries. It doesn't need it in all lakes, but some lakes. So if we've changed the characteristics of the lake, where we've increased the rate of that organic material being produced by putting more nutrients into that system, we increase the rate at what oxygen depletes. If we don't have enough oxygen stored in that portion of the lake because of this high rate of sediment decomposition, that area goes without oxygen, we call that anoxia, and then fish species and other aquatic life can't really live down there. Some invertebrate species can, that can sustain really low oxygen levels, but the things we might relate to can't live in that portion of the lake. So conversely, in a shallow lake, that same process is going on. And as long as that lake stays continually mixed we're fine, but the whole chemistry changes when we go without oxygen in the bottom of the lakes down there and lakes start to release nutrients back into the water column. Well, that's not a problem up in our deep lake, where those nutrients stay down there on the bottom of the lake and aren't available for algal production through the growing season, but in some of our shallow lakes, which one I'm gonna show you shortly, that can be extremely problematic, cause we call that internal loading, or the ability of the lake to self-fertilize itself from its lake sediments. And in some of those lake ecosystems, we have approximately 200 of these lakes, we call them polymictic, or they mix many times per summer, and every time they mix after a period of anoxia or when that sediment water interface has gone without oxygen for several days, you get a pulse of nutrients buildup there, boom, the lake mixes, where does that nutrients go, it goes up in the water column, it becomes available. The other issue with shallow lakes, especially lakes, let's say, shallower than maybe 12, 13 feet and shallower, when that ice layer goes on in the winter time that creates a barrier now between the atmosphere and the lake. Well, as long as sunlight is getting through that ice layer the lake still sustains a relatively high amount of dissolved oxygen to sustain a fishery in there. But when we put the snow on that ice, we turn the lights out, when we turn the lights out, we turn off the algal production, the ability of that lake to produce its own oxygen. Then that fishery becomes at the mercy of the amount of oxygen that's stored in that water. And so, if you hear the term "winter-kill lakes," well, what's really gone on in that system is the lake, simply because of the bacterial decomposition in the sediments, has used up all the oxygen in the lake, and the fish die. So lake depth definitely does matter and impact. This is a lake that I've worked on for many years now. Now, folks, if you have your own lakes, and you want to get like an average depth of your lake, this is Cedar Lake, it's up in Polk and St. Croix Counties. This is a polymictic lake. Well, if you look at that darker gray center where the words Cedar Lake are, that's the only portion of the lake that's about 25 feet or different. The wind fetch on this lake is north to south, it's almost two miles long, and what happens with Cedar Lake is that 25 foot from really about 18 feet and shallower, when we go to quiescent periods, not much wind during the summer, Cedar Lake will set up and stratify, but has very enriched bottom sediments. Those bottom sediments are releasing phosphorus into that lake water and then when we get a thunder storm or a large wind event that comes through, the lake will mix top to bottom and we'll end up with an algal bloom. But one of the things I wanted to show you here with this slide was, you can simply calculate your mean depth of your lake very easily, and it's simply the volume of water in the lake, which in this lake it's about 20,000 plus acre feet, divided by the number of acres, and that gives us your mean depth of 18. So you can do this in cubic meters, and square meters on top, but this information is usually available to you on any of your lake maps. Retention time and flushing rate, this is very important. Algae need times to get off many generations to live, and pollutant flushing is also dependent on this. So when we use the term retention time, that is simply, if you drained your lake down, how long would it take it to refill? The inverse of that is flushing rate, and that would give you, in time, how many times per year your lake would flush. So when we think about a lake like Long Lake, that is relatively high up in the landscape, it's a deep lake, it's a large lake, without a lot of water coming into it. If we drained Long Lake out totally it would take seven years for that lake to fill up. So water stays in that lake at least seven, but when we think about a mass of pollutants coming in to a system, it takes about three of these flushing times, or the lake has to fill, empty, fill, empty, three times before we move the pollutant on. So it can have an impact for a long time, so if we get a big storm event, would bring a lot of pollutant loading or phosphorus into Long Lake, it would be potentially impacting water quality for a couple of decades. That's opposed to Lake Altoona which I showed you earlier, where they have a large river coming into that system, it's a relatively shallow basin. The average time water stays in Lake Altoona is 22 days, but when we get into a high flow event, it may be only in there less than a day, a few hours, during a flood event. So we can take a lot of pollutant loading and flush it through a system like that. The other impact on lakes when we think about that is how much land physically drains to each acre of lake. When we have lakes that have less than ten acres of land, ten acres of watershed to each acre of lake, those tend to be our higher water quality systems. There just isn't enough land mass out there to produce enough inputs of sediments and nutrients to impact water chemistry that much. And that's opposed to some of our lake ecosystems, and I'll talk about that, or reservoirs, where we may often have two, three thousand acres of land draining to every surface acre in a reservoir ecosystem. So landscape position, simply think about the land of Wisconsin on a tilt, or your watershed a bit on a tilt. Those lakes high up in the system near the top of the hill, so to speak, those are our seepage lakes. The ones highest up, often don't even have a lot of groundwater in flow to them so drought can produce extreme effects on them. We have lakes up in the Chippewa County forest and the Chippewa marine that their lake levels still have never recovered totally since the '88, '89 drought. So we're that many decades out. And as you move down through the system, you're accumulating more water all the time and you have higher groundwater inputs and surface water input. So those ones higher up, smaller watersheds, less runoff, tend to be where you find your higher quality lake ecosystems. The Sand Lake I showed you, the Long Lake, both very, very high quality systems. They're very high on the landscape. Lake Altoona, very low on the landscape. It's right near almost where the Elk River dumps into the Chippewa. Large land mass that drains to it, has a much poorer water quality and sedimentation issues. So let's switch over now a little bit to think about, so that's kind of the physical nature of this lake and how their function, it's mass of water coming in, mass of water in the basin, those types of things. But what are the characteristics of that water? How is it influenced? That ultimately will influence the biological characteristics of the lake. So if we had just distilled water in our lakes, we wouldn't have any life in our lakes, right? So we all need a mix of nutrients in our life. We have micronutrients, which are made of the elements on the side of the lower graphic. Some lakes are harder, softer. That's simply the amount of dissolved ions in the lake ecosystem. And dissolved oxygen is obviously incredibly important in our lakes. I talked a bit about winter-kill. To maintain a viable warm water fishery, our dissolved oxygen concentration needs to be 5 or above to sustain all life stages of that fishery and that system, that is our water quality standard for a warm water fishery. What I really wanna focus on are nutrients a bit, especially the ones we can manage. So when we really think about the primary nutrients in lake ecosystems, there's carbon, nitrogen, and phosphorus. It's that ratio especially of how they relate to one another. But when we think about the nutrients we may have some ability to impact. We really can't impact carbon, we really can't impact nitrogen, that much of the atmosphere is full of it. But we can impact this element called phosphorus. So phosphorus really is a major driving in ecosystem health in most of our lakes in Wisconsin. We need phosphorus in these systems. It's a critical component in all forms of life. It's part of our DNA, our RNA, our energy metabolism for us to sustain ourselves or any other living thing. But a little bit of phosphorus can go a long way at producing algae in a freshwater ecosystem. 1 pound of phosphorus can magnify itself into 500 pounds of algae. That's a huge ratio. It, naturally, in Wisconsin, because of our parent soil materials, we did not have a lot of natural phosphorus. Our lakes in a pre-settlement condition were very, very low for the most part in phosphorus. It leads us to this concept of limiting nutrient principle. That simply is that the nutrient in least supply in that lake ecosystem or freshwater system, will control the amount of plant or algae growth, and we often relate this just to algae. So if we only have about 10 times as much nitrogen as we do phosphorus in the lake, then we say the lake is nitrogen limited, but when we're in 15 times more nitrogen than phosphorus, then really phosphorus is doing, it's that gray area in between. But this was really not well understood really until the 1970s and there was great debate. You think back 40, 50 years ago, why was that important because we just take for granted that we can deal with this. Back in those days, all of our cleaning solutions across the world, phosphorus was a major constituent in them. And the soap and detergent industry really wanted to protect that ability to maintain phosphorus and we hadn't really gotten into this understanding of well, we should be morphing our products into more healthy things that help us live our lives. So there was great debate going on all across the country. There was a camp saying it was carbon, another camp of scientists saying it was nitrogen, and then there was a group talking about phosphorus, so this was really put to rest in the early 1970s by a Canadian researcher named Dave Schindler as a young graduate student or young professor, up doing his work in Laurentian Shield in Canada, and with lakes, they simply did was took this lake, it was Lake 227, put a plastic curtain there across the middle of the lake that goes all the way to the bottom, and he fertilized both sides of the lake with nitrogen and carbon, so there was plenty there to sustain algae. And so then what he simply did is then augmented one side of the lake with phosphorus, and that was the response Dave got and it got kinda put the whole issue to bed. It is, most of our lakes, phosphorus does control algal growth in most of our lakes and we feel that in Wisconsin, over 90% of our lakes are phosphorus limited. So it's the one we're really concerned about. How we manage that on the land and in the lake will control the amount of algae and the type of algae you'll get in your lakes. So soon after that, there was many, many people across the world and the country, started trying to figure more of these relationships out, and this is a very basic relationship and it simply is, as you put more phosphorus into a lake ecosystem, you will drive more algae growth and this is a log-log scale, so people that understand math, this is a lot of noise around here. We have many, many mathematical simulations and variations of that, that really help us determine how far do we need to reduce those phosphorus levels in lakes to restore ecosystem health. So we spent a lot of time on this. When I was originally hired to work for the DNR, back in the early '80s, it was one of my jobs to understand these relationships in streams and people were working on this in lakes. So, we finally got to developing water quality criteria for lakes in Wisconsin, 30 years later in 2011. So why do we develop criteria? Well, it's when we have obvious water quality problems and we know they're caused by excess nutrient loading, we need to know how clean is clean, where do we need to manage that system back to, and those goals that then directly relate to them. We have numbers that we know can protect recreational fish and aquatic life uses and those things, and also EPA said this would be a good thing for all the states to do. And these are our criteria for lakes in Wisconsin. So those two-story fishery lakes where we wanna maintain the integrity of that dissolved oxygen, and those deep lakes below that thermocline, that stratified layer, they are very sensitive to phosphorus. We'll give them a very low number, 15 micrograms per liter. To maintain those stratified lakes, those deeper ones, those higher quality lakes that I talked about, that's 20 micrograms per liter. These are very, very low numbers. These are parts per billion, so if we had a billion ping pong balls in this room, to maintain integrity of a stratified lake, only 20 of them could be represented as phosphorus molecules, so these are very, very low numbers. And so, as the lakes become less sensitive to phosphorus, as we get up into those reservoir systems, those numbers we have developed are 40 micrograms per liter which is twice as much as what would be in a seepage lake. So let's think about now, how does this impact the biology of the system, right? So what we really want to have, we gotta create this food web through the system. And so what we want are the high quality algae species in the system that can go up into our invertebrate population, that little guy in the middle there is called a zooplankton. We have many, many species of those in our lakes, and they're the guys that are the energy transformers. They're taking those algae cells, turning them into meat protein, and then they will be harvested by fish that eat them, often our panfish or some of our minnow species is a good example. So we have all this biology going on in our lake ecosystems. So what does that primary function of that algae? Well one of the first things it is, is that energy source for our invertebrate community, those filter feeders, we call them. But they also produce oxygen. We surely need oxygen in our systems to sustain us. But it's the type of algae we have. As long as we stay with these types of algae over in the lower type, these are smaller-celled algae, our lakes' ecosystem health remains in a high quality state. But when we put too many nutrients into this system, we shift from this algae population dominated to a blue-green algae population, so we call those cyanobacteria, blue-green algae. As you increase the phosphorus concentration in our lakes, we increase that lake's capability, we make that nutrient more available, we want all those other algae, different genera of algae to be in our lakes that are smaller cellular algae. They don't create the nuisance algal blooms. But you can see there's a transition right there in many lakes around that 20 microgram per liter number. Soon as you get above 20 micrograms per liter, you start to create a situation where blue-green algae dominate in our lake ecosystems. These are both pictures that have come from-- Picture on the left is an algae bloom on peat oil flowage. That's one of my co-workers on the right, that is in Tainter Lake, over near the city of Menomonie. These lakes have the ability to produce very, very high levels of blue-green algae. And what blue-green algae, some species at some times during their life stage, we're trying to figure out what trips us, they can produce toxicity. That's what probably killed that goose in the left. But these toxins can be harmful to us, our pets, if we get to these high levels. When these cells die, they release the toxins into the water. These are just some of the characteristics associated that can be how they impact us. We can get dermal reactions. We have had many folks over in the Tainter Lake system that are very prone to it, that'll get rashes. One of our staff people was loading a boat one time, by the time she got back to the lab, showered up and everything, she got home and she had this incredible rash on the lower portion of her leg, where she had been in contact with that water. Neurotoxins, when you hear of dog deaths sometimes, or cattle deaths in farm ponds, they ingest that water. It can be a very rapid death for some of those, and then we also have hepatotoxins, blood impacts, where it impacts liver function, so if you see water quality characteristics that look bad, just stay out, cause there could be blue-green algal toxicity. So let's switch here, I mean, I guess, just again show this invertebrate communities, an important part of our lake ecosystem, and it is one of those that energy transfer. This is the zooplankton, the daphnia on the left. That is lunch for "young-of-the-year" fishes, that's what they're after. And if we have a high quality algae population, high quality zooplankton, there's a lot of energy there to produce a lot of fish biomass up the food chain. Aquatic plants, incredibly valued in our lake ecosystem, as long as, again, that system is in balance. They are absolutely critical habitat for many of our aquatic species that live in lakes. They are great physical structure and are energy dissipaters and they produce oxygen. Fish, I think this is what we all kind of relate to when we think about this. As long as we have good habitat, good water quality, we tend to have high quality fisheries, and some of those highly impacted lakes, that Cedar Lake that I was talking about, we went through a period of time there where the fishery, probably 95% of the fish biomass in the lake was tied up in carp. It was also a huge impact on water quality. Our rough fish have very short gut tracts. They eat the benthos, the bottom invertebrates off the lake, and what they can do is they actually take those invertebrates and sediments from the bottom, put them through the gut tract, make many nutrients available, and they can be a source of nutrients, posing a poor water quality problem. When we looked at Cedar Lake back then, we thought about 30% of the water quality problem in the lake was simply due to the mass of carp that was in that system. They were putting thousands of pounds of phosphorus a year into the photic zone, the area where light is in the lake, to create the algal blooms. They were a big factor in that issue. So, again, all these critters need high quality habitat. These are the views and those characteristics, those services we want to maintain in those lakes. We'll talk a bit about habitat. That near shore habitat, we call the "littoral zone" is where the light penetrates deep enough into the water to allow aquatic plants to grow shoreward from that, and then up onto the lake shore. So when we just think about that littoral zone, or the area where light penetrates deep enough to stimulate the growth of aquatic plants, over 90% of the species in any given lake are dependent on that critical habitat component for at least some component of their life history. So if we can maintain the integrity of that, we often maintain the integrity of the system. And then shoreward from that, that shoreland buffer zone area is absolutely incredibly valuable for aquatic life near shore, water-dependent wildlife and water quality of the lake. So how have we developed our lakes? And how have these impacts impacted our lake ecosystems? I'll try and finish up here. Oh, sorry. As we think about this, we look at, this is what our lake shores often looked like in an undeveloped state. We had emergent vegetation out the submergent. Natural woody vegetation on the shore. As we have brought our societal values and how we live in our communities, you know, this is what we've often brought to these, and so, when we bring that type of pattern of development, we lose these natural ecosystem functions to our lakes. So how does that impact our lakes? So one of the things we've looked at, we have a compendium of literature that's been developed in the '90s and through the early 2000s in Wisconsin, but they all kind of show the same thing. With the way we develop our lake shores, once we get to about 30 homes per mile, we have lost many of the ecosystem services that that nearshore and that shallow water area provides. And this happens to be a green frog study. Once you get about to that level, there is no longer the characteristics there at a high enough level, and our green frogs are gone, but it also shows up in other areas. This is coarse woody habitat, we call it. It's wood in the lake. And this is a very valuable ecosystem function, providing diversity of habitat, diversity of refuge on that wood that's growing, and there is a thin layer of algae which has a lot of inverts growing on it which a lot of small fish come in and pick off. Big fish come in there to the prey, little fish come in there to get away from big fish. But again, when we get out around that 30 homes per mile, we lose this ecosystem service in our lakes. This is Dan Schindler's work, he happens to be the son of Dave Schindler. He was one of our grad students at the Center for Limnology back in the late '90s. And what Dan started looking at, so how does this impact fish growth if we don't have that high quality habitat in our lake ecosystems in the north? And what he really showed was fish in lakes with good woody habitat have growth rates of three times more than lakes where we've lost that. So if you turn that around, you could say one way we've developed our lakes, we've lost about a factor of three, or if we had that high quality habitat in our systems, our fisheries' production would be improved by as much as 300%. It's a huge number. So, finishing up with talking a bit about how land use impacts and watershed impacts water quality. We think about that and natural lake ecosystem, when that water falls on back to the hydrologic cycle slide, only about 10% of that water would runoff. 50% of it would go in and contribute to sustaining ground water levels. So when we urbanize an area, especially, we flip that totally around. In an urban area, we only maybe infiltrate 15% of the rainfall and we runoff 55%. That 55% running off is a huge transport mechanism for phosphorus sediment and other pollutants. So our challenge as managers is how do we take a system like the picture up on the left, but make it function like one on the right? And we can do this, it's not that big a deal. But we have to value that function, as a society, before we can do that. So when we think about this, we have a variety of models, but when we as scientists talk about runoff or how much pollutant loading comes from a given land type, in a natural state, our landscape, that one on the lower right, that forested area or low density urban, that only loads pollutant phosphorus to a water body at about 0.1 kilograms per hectare per year. You can flip that right into pounds per acre per year, if that's easier to think about it. But by the time we get to mixed ag, or high density urban, we've increased that by an order of magnitude, by about ten-fold. This is a new tool that's out there for any of you folks. Go see Matt Diebel's talk in the next session after plenary, but what Matt has put together for us now for all lakes in Wisconsin-- That happens to be Cedar Lake down there in the bottom. And through GIS techniques and digital elevation models, we can computer generate what your water shed looks like now and the land use characteristics of it. And the reason Matt put this together for us on Cedar Lake is that, I think he's got some place here, I thought-- oh, the phosphorus load, most likely because of the amount of agriculture in there, this watershed, he estimates to be loading about 0.5 pounds per acre per year, most likely, at 13,600 pounds a year. Well, because of the farmers in this watershed have cooperated fantastically with their lake shore neighbors, this watershed only is functioning at a factor of about 0.2 pounds per acre. And it shows we can manage the runoff in these agricultural ecosystem watersheds, so their amount of phosphorus coming off the land is only two times above background. That's a phenomenally low number for an agricultural dominated watershed. And so how does that ag source area get on there? Well, we put it on there through what we've fed our cattle. After World War II, we've had a lot of our dairy cattle on enriched phosphate mineral that showed up through their manure that has been on their land for decades. Farmers have really since, I would say, the late '90s, no longer feed, we found we don't need to feed that. And then of course, inorganic fertilizers, and farmers are doing a tremendously better job of really putting on that fertilizer based on crop need and managing their land off in a way so it doesn't generate runoff. Here's just a fact from Lake Mendota. This is Elena Bennett's master's research for Center of Limnology back in the mid '90s. What Elena did was put together a mass balance for how much phosphorus did we put on the land in the Lake Mendota watershed? Well, this is 1,300 metric tons, so there's 2,200 pounds in a metric ton. That's a few million pounds of phosphorus a year. And then, how much really do we use of that phosphorus to produce the meat commodities? A little over half of that. So we were storing, back in pre-1995 conditions of Lake Mendota, we were just mass accumulating phosphorus on the landscape of over a million pounds a year, 575 metric tons. It's a huge number. So we have learned from these situations and we're doing much better today. Residential development, boy, that has impacted our lakes, especially from new channeling. How we develop property when we develop or rebuild a home, we totally destroy the soil health, the soil structure, by putting all this equipment around. We virtually eliminate often, or severely reduce the ability of that soil to infiltrate water. We fertilize our yards, we grade our yards to make them highly efficient to get that storm water run off away from the buildings. So we did a little work, John Panuska, he did this work for us when he worked at DNR. He's now over at the university. John did some modeling for us so we took an individual lake slot. We wanted to simulate a lot up on Long Lake in Chippewa County. So in a natural condition, before we did any development, John simulated that this slot would generate about 1,000 cubic feet of runoff of water, 3 hundredths of a pound of phosphorus and 5 pounds of sediment. So the first property that was built on this lake was post-World War II, where we had, this is what we were building. This happens to be the Laine Cabin, up on a lot. And so when Grandpa Laine came up on the train from Chicago in the summer, he built a cabin, built a cottage, and what was that impact? Well, that impact, he really didn't impact cause we weren't putting much impervious surface down, we weren't disturbing much of the lake life, so we maintained most of those natural hydrologic characteristics of that landscape. So things changed a bit when the Laines sold the property and the boom in the market in the '90s. This is a very modest home by those standards, but it really changed things up on that lot. So we went almost to 4,000 square feet of imperviousness. We had to get around on that lot to build that house, and so we impacted runoff, we predicted five-fold increase. In phosphorus, about a seven-fold increase. Our lakes cannot sustain these types of increased inputs if we don't manage them. Okay, so this is just a shot as we increase that imperviousness. Once we get to even as little as 15% of the lot is covered with rooftops, sidewalks, walkways, driveways, you've increased the mass loading of phosphorus from that parcel of land by a factor of six. And so, with that, I'm done. Thanks, folks. (applause)