Don’t P in your lake

OK, I borrowed that headline from a very clever campaign in Town of Meredith, New Hampshire. It’s a public education campaign to encourage people to help keep phosphorus (chemical symbol P) and pesticides out of local lakes. It’s also a good bit of advice to follow on your lake.

Phosphorus is a nutrient that in excessive amounts can cause algae blooms, which degrade water quality and in extreme cases may kill fish and lead to pileups of foul-smelling (and toxic) blue-green algae.

Phosphorus is found in some lawn fertilizers. Here in Wisconsin there are restrictions on the sale of such fertilizers; they definitely should not be used on lakefront properties. Runoff from lawns fertilized in this way will carry phosphorus into the water – along with traces of any weed killers and other pesticides that have been applied.

Another source of P (the phosphorus kind) is a faulty septic system that doesn’t adequately treat household wastewater and instead releases it to the environment. If you’re not maintaining your septic system regularly, you would be well advised to contact a local septic service provider and get on a regular program of inspection and pumping.

And since you must be wondering, yes, doing the other kind of “P” in the lake does add phosphorus. So for the good of your lake, don’t do it. There’s a reason why you have a septic system (or sewer connection). In our household we also take care to used phosphate free detergents and dish soaps. We have a new and properly functioning septic system, but why add more phosphate to the environment if we can easily avoid it?

OK, that’s your sermon for the week.

Thin soup

A business acquaintance once asked if I would join him for an evening meal. When I accepted, he said, “Good. Then I’ll call mama [his wife] and have her put a little more water in the soup.” Not exactly cooking the fatted calf (fortunately he was kidding).

Thin soup may not be very nourishing to us humans, but in reality your lake is a thin soup that has plenty to eat for creatures that live in it. The meat and vegetables in your lake’s broth are plankton, of two basic kinds: plant (phytoplankton) and animal (zooplankton).

Books could be (indeed have been) written about plankton – it is an incredibly rich and important source of food in a lake’s ecosystem. It is also incredibly interesting to observe under a microscope. The little zooplankton creatures are fascinating, and the phytoplankton (mainly algae) are amazing in their variety, symmetry and, yes, beauty.

There is much more to write on this very large topic. For now, suffice it to say your lake’s water is loaded with plankton. Just how loaded depends on where your lake falls on the nutrient scale – from oligotrophic (nutrient poor) to eutrophic (nutrient rich). But then, that’s a whole other subject.

If you were to take a long net with an extremely fine mesh and drag it behind your boat for perhaps 1,000 yards, you would collect a sample of your lake’s plankton. In fact, by knowing the size of the net’s frame and the distance you traveled, you would be able to calculate the density of plankton in the water. Of course that calculation involves a little lab work, too. You would have to dilute the captured plankton in a known volume of water, take a sample of that, and under a microscope, count the numbers of phyto and zoo pieces, and crunch some numbers. It’s a process, but the math isn’t all that complicated.

The point for now is that when you look down into your lake, you are looking not just at water but through a liquid full of life-giving food. Plankton form the base of any lake’s food chain – or perhaps more correctly, the anchor points for the lake’s food web. It’s plankton that tiny fish fry eat when they are too small for anything else. Bigger fish then eat the fry, they get eaten by still bigger fish, and so on all the way up to the mighty muskellunge. So, in the end, no plankton, no musky.

If big oaks from tiny acorns grow, then in a somewhat different sense, trophy fish grow from tiny plankton. It’s a neat concept to dwell on.

Whose lake and whose land is it, anyway?

If you live on a lake, what do you think of shoreland zoning laws? There are a couple of schools of thought on this subject. One says that if I buy lake property, it’s my land and I should be able to do what I want with it, free of interference. Another says restrictions on lake lot development are needed to protect water quality and aesthetics because lakes (at least here in Wisconsin) belong to the public, according to the state constitution.

I fall into the latter school. I write about this now because there is a move afoot here to roll back some of the shoreland zoning protections that were passed a few years ago after long debate and extensive compromise among many interests.

I see shoreland protection from two sides. For most of my 60 years I was a lake visitor and greatly appreciated the northwoods scenery on lakes where development was somewhat restrained – where most property owners left the native trees intact, refrained from planting lawns, kept piers unobtrusive, and generally went easy on the land. Now I own lake property (I live here on Birch Lake near Harshaw in northern Wisconsin) and my feelings about lake development haven’t really changed.

Our shoreland zoning here in Oneida County says that if we want to we can clear trees from a “viewing corridor” 30 feet wide. We have not done it nor do we intend to. We have a lovely “filtered view” of the water from atop a hill. You can hardly see our place from the lake. That's good for our neighbors and lake visitors, and for us, because the trees help confer privacy. 

What concerns me most about the proposed changes to the shoreland protection rules is a rollback of limits on impervious surfaces. We have a small lot potentially subject to such restrictions. I support them – for the simple reason that too much runoff, from our property and others, is a direct threat to the water quality in the lake. Shouldn’t I be willing to invest a little more for stormwater control, if doing so helps protect the lake, which is integral to my property and its value? Why would I want, in effect, to soil my own nest?

On one level I can understand those who say, “I paid a lot for this property and no one should be able to tell me what I can build on it, or where, or how much.” On the other hand, we have such things as zoning laws and, in certain subdivisions, architectural codes, because we’ve decided that life is much better if we use land in coordinated ways. In the very simplest sense, observing zoning laws and shoreland protection rules amounts to being a good neighbor. With the force of law, mind you, but nonetheless.

Our lakes are precious. I don’t believe I have the right to expose “my” lake to the risk of pollution just because I believe I can do what I want with “my” land. So I am all for shoreland protection. And if compliance costs me extra money and some inconvenience, so be it, because it is going to help protect the values – scenic, environmental and economic – of the lake I love.

The best five minutes of the day

Sunsets on a lake are great to watch, except when the sky is mostly cloudless. In that event it hurts to look west, the glare painful and you wait for the sun to touch the treetops across the water. Then begin the best five minutes of the day.

Five minutes is (very roughly) how long it takes for the sun to sink from treetops to oblivion. In that time, the entire scene changes, as if a hand slowly, slowly turned a celestial dimmer switch. The west takes on a brilliant glow, the glare less oppressive with each minute. The far shore of the lake, rendered almost featureless black by the intense backlighting, gradually takes on definition. When the sun is gone the whole scene bathes in mellow light. Now any clouds take on a rosy tint against the sky’s soft blue.

By this time of course, the wind has died, the lake’s surface mostly still, the small, smooth waves just enough to lend a dreamy motion to the sky’s reflection. Things also seem to quiet with the sun’s departure, as if the overpowering light had created a subliminal noise, now silenced.

Now comes a restful hour as slowly daylight fades, a perfect time to reflect or just let the day’s stress seep away. All brought on by those decisive five minutes as the treeline snuffed out the oppressive sun.

“I’m a helpless mother duck. Come and get me.”

One of lake life’s little pleasures is seeing families of ducks paddle past the pier. Usually on our lake it’s mother mallards with their clutches. Last evening it was (as best I can tell from a retrospective look at a field guide) a hooded merganser mama with her brood.

As I stepped from the trees onto the pier, carrying my tackle box, half a dozen little ones scooted off to the left along the bulrushes. The ruddy-crested mother, meanwhile, made certain I noticed her, paddling frantically off to the right, a classic maneuver meant to lure a predator away from the young.

When I simply stood watching, she came back and repeated the maneuver, the brood by this time well out of sight, probably up in the shoreline brush. Still not satisfied, mama swam around and once more tried to engage me in a chase. She continued her act while I untied the boat, stepped in and started the outboard, whereupon she scooted some 50 yards on an acute angle out from shore. As I backed out from the pier, now directly between her and where the young had gone, she swam a tight circle, watching me. Only after I had traveled well out onto the water did she lift off and, in a flicker of wings, skim the waves to rejoin her brood.

It was a treat not just to see the show but to find out it was (probably) a hooded merganser, smallest of the merganser family, a secretive species not seen all that often (I had never seen one before). Which varieties of ducks frequent your lake? Certainly more than just mallards. It’s nice to keep a field guide handy for identifying ducks, especially during the migrations.

Row, row row your bug...

As kids my friends and I called them “water spiders.” We were wrong linguistically and taxonomically. They were actually water striders, and they not spiders but insects -- quite amazing insects at that. For one thing, like the whirligig beetles I posted about earlier, they were (and are) nigh impossible to catch – they move on the water’s surface with incredible agility.

Most interesting, though, is how they move. They have six legs like other insects, but they use them differently. The front pair catch prey. The middle (much longer) pair act like oars, for propulsion. The hind pair provide steering (like a rudder).

But how do they stay afloat as they do, legs in contact with the water, body elevated like that of a four-wheeled crop sprayer going over a field? It has to do with my previous post about the surface tension of water. Surface tension keeps the legs from sinking below the surface. One thing you notice if you watch striders in shallow water are the four roundish shadows the front and hind “feet” cast on the bottom. Those are from the dimples the feet make in the “skin” of surface tension. The surface tension bends, but doesn't break, under the striders' weight.

Of course, closer examination has shown that striders’ high flotation is not all about surface tension. The legs are covered with microscopic hairs that trap tiny air bubbles, which provide buoyancy. Scientists say studying and replicating these hairs could lead to development of better water-resistant fabrics.

As described on the website Livescience (www.livescience.com): “Microscopic images of the insect’s legs revealed that the otherwise invisible hairs, called microsetae, are oriented in one direction and involve several layers. The needle-shaped microsetae are each less than 3 micrometers in diameter (a human hair is 80-100 micrometers wide).

“The microsetae are scored with grooves measured in nanometers, even smaller units that represent billionths of a meter. Air gets trapped in the spaces among the microsetae and nanogrooves to form an air cushion, which prevents the legs from getting wet.”

The science is interesting, but mainly it’s treat just to watch these creatures and, if your eyes are quick enough, capture the swift, sure rowing strokes by which they move. You can find water striders on almost any body of water. Look for them on your lake.

Your lake has a skin (well, OK, not really)

Now and then as you get to know your lake, it’s useful to consider the properties of water itself. One of those is surface tension, a property that will relate to the topic of my next post.

You’ve seen the rounded shape of droplets on a lakeside leaf or pier board. You’ve noticed how it’s possible to fill a glass with water to just very slightly above the brim – if the glass is kept very level and very still. In both cases, surface tension is the phenomenon responsible.

Because of surface tension, water behaves as if it had a (very thin) skin. In reality it doesn’t, of course. What we see with surface tension is the result of molecular forces, specifically the cohesive force between the water molecules.

As the U.S. Geological Survey explains it: “The molecules at the surface of a glass of water do not have other water molecules on all sides of them and consequently they cohere more strongly to those directly associated with them (in this case, next to and below them, but not above)...The stronger cohesion between the water molecules, as opposed to the attraction of the water molecules to the air, makes it more difficult to move an object through the surface than to move it when it is completely submersed...

“Within a body of a liquid, a molecule will not experience a net force because the forces by the neighboring molecules all cancel out. However, for a molecule on the surface of the liquid, there will be a net inward force, since there will be no attractive force acting from above. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken. Thus the surface is under tension...”

How might you observe or experience surface tension? Believe it or not, it is possible to (very carefully) place a small needle on water and have it float, even though its material, steel, is several times as dense as the water.

When camping in the rain as a kid, did your parent’s ever warn you, “Don't touch the tent”? Touching the fabric will in fact cause water to leak through. Why? Surface tension in the water bridges the pores of the material, in effect creating a rain barrier. But touching the material breaks that surface tension. Drip, Drip, Drip.

Detergents in effect “make water wetter” (as an old commercial claimed), reducing surface tension so that it soaks into the fabrics more easily. Similarly, hot water is better for washing because it has lower surface tension than cold water.

On clam days around your pier, look for visual evidence of surface tension. You may find one in the incredibly cool insect my next post will describe.