A place for lake lovers

What are you doing April 23-25? If you love your lake, you might want to consider attending the 2015 Wisconsin Lakes Partnership Convention, or at least a part of it.

I’ll attend this year for the fifth time, and I wish I had started long ago. It’s an inspiring event. You spend a couple of days surrounded by scientists, communicators, lake association leaders, advocacy group representatives and others all interested in one thing: making lakes better.

For a few days you shed your political affiliation, forget what you do for a living and just learn, in hands-on workshops, field trips, lecture sessions, poster presentations, an exhibit hall, and casual break-time and lunchtime conversations.

Sessions cover all manner of subjects: aquatic invasive species, wetland protection, fishery surveys, nutrients and algae, shoreland zoning and other government policies and, perhaps most important, how to get involved in improving the lakes you care most about.

My all-time favorite session, during my first trip to the convention, was a half-day workshop on aquatic plants. There were slide presentations followed by hands-on exercises examining specimens of common and less common plants and using what’s called a taxonomic key to identify them by name. I’m a fisherman by avocation, but now when I’m out on the water, I am much more attuned to the greenery below and on the surface – it’s no longer just “weeds.”

Also of note are the plenary (whole-group) sessions, which generally feature inspiring speakers. This year, the keynote speaker is Marion Stoddart, a citizen leader and grassroots organizer who is largely responsible for the conversion of New England’s Nashua River, once among the nation’s most polluted rivers, into a candidate for the National Wild and Scenic Rivers System.

I can’t wait to hear her talk. I know I haven’t done as much as I could for lakes, including my own, and her words may help nudge me into more action.

The convention will be at the Holiday Inn Convention Center in Stevens Point. That’s not so far away, and the registration fees are affordable. There’s a good chance that one or more leaders of your lake group plans to attend. If you’re interested in doing more for your lake, you might want to consider going along.

I know I appreciate lakes more deeply, and feel better qualified too advocate for them, because I’ve gone to this event. 

Eutrophic lakes: It’s a process

Mention a “eutrophic lake” and many people will picture a stagnant pool, matted with algae, murky, bad smelling, and generally unpleasant to be around.

It really isn’t that simple. A eutrophic lake by definition is at a fairly advanced stage of a process called eutrophication, whereby the lake accumulates high levels of plant nutrients, chiefly nitrogen and phosphorus. But the mere fact of being eutrophic does not mean a lake is “dirty” or “polluted” or otherwise undesirable – although that can be and often is the case.

Nitrogen and phosphorus are necessary for plant growth. Your lake, whether eutrophic, oligotrophic (few nutrients) or mesotrophic (in between), contains these nutrients. Otherwise there would be no lily pads, no fish-attracting cabbage weeds, and no tiny algae that form the base of the food chain.

The problem comes when the amounts of nitrogen and phosphorus become excessive. Blame for that often gets placed on human sources – uncontrolled stormwater runoff from city yards and streets, runoff from over-fertilized farmland, poorly maintained septic systems, and others.

But nutrients also come from natural sources as, for example, when a shallow lake is surrounded by and receives runoff from land with fertile soils and abundant organic matter. That is to say, some lakes are naturally eutrophic, and no amount of water-quality regulation or watershed management will change that.

Of the two main nutrients, phosphorus is the one that – here in Northern Wisconsin and in most regions of inland lakes – controls the pace of eutrophication. Some of the nitrogen in lake water exists as nitrate – an atom of nitrogen and three atoms of oxygen (NO₃). Over time, biological processes convert this nitrate to nitrogen gas (N₂), which then escapes to the atmosphere. So there is to some extent a natural “brake” on the buildup of nitrogen in lakes.

It’s different with phosphorus – it accumulates in lakes, and when present in excess it can cause explosive growth of algae. Darby Nelson, in his brilliant book, “For Love of Lakes,” explains with great clarity how this works.

He first describes the ingredients in his wife’s blueberry muffins and how, if she happens to have only two teaspoons of baking powder, she can only make one batch – no matter how much flour and sugar and how many eggs she may have on hand. Then:

“In lakes, except in unique circumstances, the ‘tin’ of phosphorus usually empties first. Compared to demand, it is phosphorus that is available in least supply, the bottleneck to alchemy. Little phosphorus in lake water begets few cyanobacteria, algae and aquatic plants. Lots of phosphorus begets lots of blue-green algae, or aquatic plants, or both.”

So if we want to forestall eutrophication in our lakes, the best thing we can do is take measures to keep phosphorus out.

The Goldilocks of trophic states

I’ve been writing about lakes as classified by trophic state: Oligotrophic (few nutrients), eutrophic (abundant or excessive nutrients) and mesotrophic (those in between).

No one of these trophic states is inherently “better” than the other. It’s to some extent a matter of personal preference, except that an extremely eutrophic (hypereutrophic) lake likely has serious water-quality issues. However, if I can be allowed an editorial opinion, I prefer to live on a mesotrophic lake, like our own Birch Lake at Harshaw.

Why? Because in many respects it mesotrophic is the best of all worlds – it is “just right.” A mesotrophic lake never gets seriously choked with weeds, nor does it typically see obnoxious late-summer algae blooms that cloud the water of eutrophic lakes. It is not as crystal clear as an oligotrophic lake, but it is reasonably clear, enough so to allow decent snorkeling, especially in June and July.

In general, mesotrophic lakes support more diverse plant, fish and other aquatic life than lakes in the other two trophic states. You won’t find cold-water fish like lake trout in mesotrophic lakes because the deep, cold water gets depleted of oxygen by late summer. However, these lakes can support excellent fisheries with panfish, largemouth and smallmouth bass, walleyes, northern pike and muskies (in varying proportions that depend on a host of other factors).

The trick with mesotrophic lakes is keeping them that way – that is, making sure that excessive nutrients (nitrogen and especially phosphorus) don’t get in and start tipping the scale toward the eutrophic side.

Nutrients get into lakes in various ways, and that in itself is not a bad thing. A creek flowing into your lake (as in the case of Birch Lake) almost certainly carries nutrients from decaying plants in the forests, marshes and fields through which it flows. That’s part of nature. The thing to avoid is needless nutrient enrichment from human sources.

Our mesotrophic lakes here in the north are typically surrounded by homes and cottages. Ideally, the property owners don’t dump fertilizers on their lawns and landscapes in excess amounts that run off into the water. And any fertilizers used should be phosphorus-free. So should any laundry or dish soaps the get discharged into septic tanks and ultimately dispersed through the soil.

Speaking of septic systems, they should be inspected regularly (a requirement here in Oneida County) to make sure they are functioning properly and not sending nutrients into ground or surface waters. Once excessive phosphorus gets into a lake, it is not readily flushed from the system. And then that lake is started on the path toward the eutrophic state. About which, more in a future column.

Where it all begins

Conventional wisdom has it that from the time any lake forms it is slowly dying. It receives nutrients that feed algae and plants that die and decompose; it steadily accumulates more nutrients until it gets choked with weeds and slowly fills in.

That’s an overly simple description of a process called eutrophication, in which lakes proceed from oligotrophic (few nutrients) to eutrophic (rich in nutrients). The reality is that most lakes here in our Northwoods started life as oligotrophic: They were formed from glaciers and were surrounded by infertile land, so nutrient inputs were severely limited.

However, not all lakes become eutrophic – or at least in some the process is exceedingly slow. Some of our area lakes remain in an oligotrophic condition. You can make a pretty good assessment on whether a lake is oligotrophic just from some simple observations.

From a distance, oligotrophic lakes appear a rich blue-green. That’s because the clear water allows blue wavelengths of light to penetrate deep. On these lakes you can see the bottom at a considerable depth – anglers often refer to them as “gin clear.”

They are tough to fish, partly because the fish can easily see their pursuers, and partly because there are not so many fish to be had. Lack of nutrients means the food chain is rather sparse. Although algae in such lakes tend to be diverse, their numbers are low. Since algae form the base of the food chain, there isn’t much nutrition to translate into fish flesh (although populations of large fish may be present).

The shorelines of oligotrophic lakes tend to be steep and rocky. The bottoms usually consist of clean rocks, gravel or sand, low in organic matter and also low in sediment-dwelling organisms. Rooted plants are scarce. You tend not to see big expanses of water lilies or deep beds of cabbage weeds, as you would on lakes more rich in nutrients.

Since plant life is limited, there is little organic matter to decompose and consume oxygen. That means these lakes can be rich in dissolved oxygen from the surface to the bottom all year long. As a result, if deep and cold enough, these lakes can support species like lake trout that depend on well oxygenated water.

Oligotrophic lakes are undeniably beautiful. For one thing, Realtor surveys show that water clarity ranks high among lake features that property buyers consider attractive. And if you are a snorkeler or scuba diver, a clear-water oligotrophic lake can be a paradise. But if fishing action is what you crave, a lake higher on the nutrient scale may be more to your liking.

Trophic Status – One Way to Classify Lakes

There a various ways, scientific and otherwise, to classify lakes. So, what categories include your lake?

Large versus small? Shallow versus deep? Clear water or stained? How does your lake get its water? From groundwater (seepage lake)? From a stream (drainage lake)? From rain and snow only (perched lake)?

Lakes come in many varieties, but one form of classification matters perhaps more than the others: Trophic status. That is, how rich is your lake in nutrients that support life? Typically, more nutrients – chiefly nitrogen and phosphorus – mean greater growth of algae and plants, and often by extension more fish, insects, mollusks and other life.

Scientists typically place lakes into three trophic states: oligotrophic, mesotrophic, and eutrophic. Generally speaking, it’s not hard to tell where a given lake falls on the scale.

* Oligotrophic lakes (“oligo” means “few) are poor in nutrients. They tend to be relatively deep with sandy or rocky shorelines. The water is clear (these lakes can be great for snorkeling). Weed growth is very limited. If deep and cold enough, these lakes may hold cold-water fish like lake trout and cisco. Think Crystal Lake in Vilas County, or Lake Superior.

* Eutrophic lakes, on the other end of the scale, tend to be shallower with mucky bottoms. They may become choked with weeds in summer, and the water may be murky from floating algae, sometimes the noxious blue-green type. They’re likely to hold warm-water fish like northern pike, bass and bluegills, along with bullheads and carp that tolerate low oxygen. Think Lake Erie, or Madison’s Lake Mendota.

* Mesotrophic lakes basically fall between these extremes. Many of Northern Wisconsin’s lakes are mesotrophic. The lake where I live (Birch, at Harshaw) falls quite squarely in the meso camp, at least by my reckoning.

In reality, not all lakes neatly fit one category or another; sometimes the lines get blurred. Vilas County’s Trout Lake, for example, falls by experts’ reckoning on the borderline between oligo and meso.

It’s common to think of eutrophic lakes as polluted or impaired. That’s not always so. While some lakes can be made eutrophic through runoff of farm manure, lawn fertilizer or other nutrient sources, some lakes are naturally eutrophic.

It’s also tempting to think of clearer, lower-trophic lakes as “better” than others – but that’s a value judgment. It all depends on how you want to use the lake. Some eutrophic lakes (think Winnebago) are terrific fisheries. Others, partly surrounded by marshes, are great spots for duck hunting or wildlife observation.

Trophic status is a fascinating and complex subject. It will be worth exploring in more detail in future columns. For now, think of your lake. Where does it fit? Chances are you already know enough about it to make a good stab at choosing the right category.

Travels etched in snow

All spring, summer and fall, animals come and go across our woodland and lakefront properties, but we barely notice because they leave little evidence.

In winter, though we easily see their tracks in the snow. Your snow-covered lake is a great place to track wildlife: The trails traverse open space instead of weaving among trees and brush.

The only trouble with winter tracking is that it can be hard to identify the actual prints. The animals’ footfalls don’t leave clear impressions in powdery snow the way they would in mud or soft sand. You need to go by clues such as the track pattern, the sizes of the impressions, and the spacing of the prints.

The New Hampshire Fish and Game Department offers a free “Pocket Guide to Animal Tracks” (http://www.wildlife.state.nh.us/Wildlife/Wildlife_PDFs/Track_Card.pdf). Its detailed images of the various prints won’t help you as much in winter as in other seasons, but the guide does include the types of track pattern and the typical print sizes.

Anyway, an essential step in tracking winter wildlife is knowing who is out and about. For example, you won’t find bear tracks in snow, since the bears are denned up until spring. Beavers don’t hibernate but typically store enough food underwater to get them through the winter, so they’re not seen very often.

So how can you identify those trails in the snow? The New Hampshire guide identifies four basic track patterns. First are the hoppers, chiefly squirrels and rabbits. Squirrels leave roughly box-shaped sets of tracks, a larger pair (the hind paws) toward the front in the direction of travel. At each hop, the front paws land first, and the rear paws leapfrog past them. Rabbit track sets are similar except that the front paws fall one behind the other instead of side by side.

Then there are tracks that proceed in a nearly straight line. Foxes, coyotes, bobcats and deer share this pattern. Deer hooves commonly exert enough pressure to leave well-defined cloven marks in the snow. As for foxes and coyotes, absent clear paw impressions, track spacing can help you tell the difference: 14 to 16 inches for red foxes, 19 to 21 inches for coyotes.

Raccoons, porcupines, opossums, skunks and muskrats leave pair of tracks, one behind the other. The sizes can help you differentiate. Otters, fishers, minks and weasels leave pairs of prints side by side (and otters, as mentioned last week, leave their unmistakable slide marks).

The recent thaw has eliminated much of the tracking snow on the lakes, but more snow will come. Consider heading out (when convinced that the ice is safe) and trying to determine just who made all those trails in the snow.

Just you and the otter

If you live on a lake, one of winter’s pleasures is walking the snow-covered ice, until the snow gets too deep, after which you can walk it on snowshoes.

You soon find you’re not the only one who takes these walks – animals will have left their tracks before you. Imagine about six inches of snow on the ice and a soft snow falling, a couple of inches of new powder already down, as you embark in your insulated boots.

You stay close to shore, because it’s a bit too early in the season to trust the open ice, but also because this is where you’ll find most of the hoof and paw prints. Now and then an animal will shortcut across a bay, or across the lake proper, but mostly the tracks hug the shoreline, food and cover close by.

Not far on your walk, you come upon sausage-shaped depressions in the snow, each six to eight feet long, paw prints between. These are the slide marks of otters. You know they’re fresh because they remain well defined, the edges not even slightly softened by the falling snow.

You may not like assigning human qualities to animals, but when it comes to otters, you can’t helping thinking that here are creatures who know how to have fun. They don’t walk or trot along – they run and slide. Yes, they take a few running steps, then flop on their bellies and glide over the snow. A few more steps and glide again.

And so it goes, the tracks continuing as you walk along. The paw prints’ orientation shows you and the otter are heading in the same direction. You keep your eyes forward, hoping to catch a glimpse, since these marks can’t be more than a few minutes old. Here and there the trail heads up into the woods, then emerges again on the ice.

You never see the otter, just follow its trail halfway around the lake to where it finally enters and stays in the woods. On this day, the new snow has cleared the lake’s slate; the only tracks in evidence are yours and the otter’s. You’re glad to have shared the moment.