Things That Grow Around Ponds

I have 2 more posts I want to do about Maine- this one on aquatic freshwater plants* and then one on memory. It’s been tough to crank them out this week as I’m down in Brazil on business. If I get time this week I may do a completely off-topic random- observations-about-this-place-type-post, but in the meantime I’ll just share this one snippet of Sao Paulo street life. If any Portuguese-speaking reader can tell me what this guy’s saying**, they get a WatcherSTICKER.

*Yes I know, not the most exciting topic for the non-plant-lover. But as I’ve mentioned before, I have a list of things I feel I need to cover in this project, and watery weeds are on it.

**Is it just me, or does he seem tense? I feel as though he could use a stiff drink, a massage, or perhaps some aromatherapy. Maybe all 3.

The Post

This post is about ponds and plants, but first let’s talk about something else: snorkeling.

I love snorkeling. When I go on tropical vacations, it’s one of my favorite things to do. You put on a mask, look down and see this whole other world below you. With a good breath of air and a few strong kicks, you’re down 10 or 15 feet below the surface, peeking at fish, echinoderms and all sorts of cool creatures hidden among the rocks and coral. I also enjoy scuba, and certainly the world opened up by scuba is even more fantastic than that sampled by the casual snorkeler. But snorkeling has a relaxed, low-risk casualness about it that somehow captures the essence of vacation: Start and stop when you want, do it with friends or alone, minimal gear, hassle and safety checks, and if you’ve had a beer or two already, well, no big deal.

So a few years back, as we were getting ready for a Maine vacation, I thought, “I like snorkeling, and I’ve always wondered what’s down on the bottom of the lake below the drop-off*. Why don’t I bring snorkel and fins along to Maine?”

*The “drop-off” is sort of the generic term we use for “when the water gets over your head.” In many parts of the 5 Kezar Ponds there is a distinct true drop-off: the lake depth goes from about 2 feet to >10 feet in a horizontal span of only ~6 feet. But in front of our cabin there no true drop-off, just a gradual, steady deepening till you can’t touch.

So our first day at the cabin, I donned snorkel and fins and waded in. I kicked out to about 15 feet of depth and dove down to the bottom. I did so about a dozen more times, moving a few hundred feet along the shore then swam back, walked out of the water, and left the snorkel & fins indoors for the rest of the vacation. There was pretty much nothing to see. Hold that thought.

A few weeks ago I posted about Lily Pads up in Idaho, which led to my learning about Floating Pondweed. Canoeing around the ponds this year I kept an eye out for it and quickly located it in plenty (pic right). But in doing so I finally paid attention to something I’d mostly ignored over close to 4 decades of canoeing, sailing and swimming in the ponds- the stuff that grows in them.

When I was younger I found weeds and pads and such growing in the water sort of icky, and always favored sandier areas, or shorelines of exposed granite, where pond-plants didn’t grow. What I didn’t realize then is that these areas are the “deserts” of ponds, relatively poor in life (including fish). Aquatic plants are a sign of a healthy lake or pond, and their presence helps to keep the pond cleaner.

Tangent: When I was a teenager, acid rain was a big worry in the Northeast. One of the side effects of acid rain is to make it difficult for freshwater aquatic plants to live, leaving “bare” lakes and shorelines. At the time, being pretty much enviro-clueless, I actually thought, “Hey that doesn’t sound so bad…” I’m even more embarrassed to admit that around that same time I first heard the idea of global warming, and thought, “Oh that sounds nice, these New England winters kind of suck…”

How Ponds Are Like Mountains

On land, the types of plants that grow are largely determined by altitude. Here in the Wasatch as you move up from ~5,000 to 11,000 feet, you pass through Sagebrush and Rabbitbrush, to Scrub Oak and Maple, to Aspen and Douglas Fir, to Subalpine Fir and Engelman Spruce, clear up to alpine tundra. What’s cool about plants in ponds is that they work sort of the same way, but in reverse, and on a way smaller scale.

Water depth impacts aquatic plants in a few ways, probably the most important of which is that it blocks sunlight from reaching the bottom. When the amount of sunlight reaching the bottom of the pond gets down to around 1% of that at the surface, plants can no longer photosynthesize effectively. The depth at which this occurs varies depends on the lake in question and the clarity of its water, but in most lakes and ponds in Western Maine it’s probably somewhere around 12 or 15 feet.

Extra Detail: Parts of Lake Superior near Duluth are clear enough to support photosynthetic algae down at over 80 feet deep. Lake Tahoe supposedly used to claim the same down to over 300(!) feet, though shoreline erosion and other human-induce factors have decreased that depth over the past half-century.

The zone between the water’s edge and this 1%-of sunlight-at-the-bottom cutoff is called the Littoral Zone, and that’s why you see things like lily pads around the edges of ponds, but not out in the middle, unless the pond is really shallow. Within the Littoral Zone are 3 distinct plant “sub-zones”, which are pretty easy to pick out from a canoe.

Tangent: I’ve been mentioning canoes a lot, because that’s how I usually poke around on the ponds. Canoes are quiet and aquadynamic*, cutting through the water gently and easily, which is nice not only because it makes paddling easier, but it creates minimal water disturbance, which is good for looking down at stuff underwater, like weeds and fish and turtles.

*Is that a word? Because if it isn’t, it totally should be.

Nested Tangent: One of my pet peeves BTW is people who can’t paddle a canoe. You know, they do 2 or 3 strokes on the left, then 2 or 3 on the right, over and over again to keep the thing going in a straight line. What’s up with that? Paddling a canoe correctly- via the J-stroke- requires about as much coordination as buttering a piece of toast. You twist the paddle away from the hull of the canoe at the end of each stroke. (Oddly, paddling a canoe is the only thing I do left-handed.)

Kayaks are even better for poking around, as they’re even more aquadynamic plus you sit lower to the water. But my favorite way to get around on the ponds is by sailing. My parents keep an old (30+ years) Sears Roebuck sunfish-type clone up at the cabin that only I ever break out. Winds on small ponds are gusty and fickle, and sailing them requires a sort weird sort of patience. You have to be willing to inch along, becalmed or with the slightest of breezes, lazing back with a sort of Zen-like calm. But when a gust kicks up, you have to snap to life, aggressively tacking upwind to get into hard-to-reach spots. Middle Pond is my favorite- long and narrow, with prevailing length-wise winds and an island* in the middle to mix it up. On a good day I can sail clear upwind to the falls, tacking at the end every 15 or 20 feet. I love it.

*Where the Loons nest.

The most amazing, counterintuitive thing about sailing is that you can sail into the wind. Doesn’t that seem like it shouldn’t work? Like you’re cheating somehow? I think the lateen sail is one of my all-time favorite human inventions. Not just because it changed the course of history*, but because it was an innovation of such significance that required no advancements in materials science or other enabling technologies; they just starting cutting sails differently, Makes you wonder what other “lateen”-type ideas are sitting right in front of us, waiting to be discovered…

*It arguably did, enabling the European age of worldwide exploration, expansion and dominance.

The Plants, Already

The first plant sub-zone is the Emergent Plants sub-zone. Here plants are typically rooted on the lake bottom, but grow up and flower above the water’s surface. An example right on our beach is Rushes. I explained the differences between Grasses, Sedges and Rushes last month up in Idaho, and as you can see, these rushes are round in cross-section. I think these may be Common Rush, Juncus effusus, which is widespread across North America. They grow just above or just below the shoreline; their bases don’t have to be underwater, but the soil/sand they grow in has to be nearly water-logged.

Moving out just a few feet from shore is a much more prominent emergent plant- Pickerelweed, Pontederia cordata (pic below, left). Like rushes, Pickerelweed is a monocot, and is native throughout the Western hemisphere, ranging from Canada to Argentina. It has thick, waxy leaves and succulent stems. But the easiest way to pick it out is by its stem spike of blue flowers. Blue-flowered plants are unusual in North American lakes, ponds and waterways, so when you see a spike of blue flowers, it’s likely you’re looking at Pickerelweed.

Side Note: The other common blue-flowered freshwater plant you’ll see, particularly in the Southeast, is Water Hyacinth, Eichornia crassipes, (pic right, not mine) (a member of the same family, Pontederiaceae) which is not native to North America but has been introduced from South America and is a pesky invasive.

The blue flowers are usually busy with Bumblebees, who collect both the pollen and the nectar, and are visited by other bees as well, including one monolectic species*. P. cordata also grows vegetatively via root-cloning, and so when you see a patch, it’s likely one big clone. Although the individual flowers last for only a couple of days, a given stand/clone will flower throughout most of the summer. Pickerelweed is native, but can be a pest both here in North America and in other parts of the world where it’s been introduced, clogging waterways and crowding out other plants. But it plays an important positive role in keeping lakes and ponds clean, filtering pollutants out of the water.

*Doufourea novangliae.

Extra Detail: Sunfish seem to love Pickerelweed on 5 Kezar Ponds. Cast your line into a stand of the stuff, and a sunfish is the only thing you’re pulling out. Pickerelweed stands also seem to be the favored locale for extensive green algal colonies, probably because the stems help make still waters even stiller, by blocking currents. These colonies always grossed me out as a kid; I swam in constant, low-level dread of sticking a foot in one*. Interestingly, down at a single-celled level, most ponds go through an annual succession of peak-bloom cycles of diatoms, algae and cyanobacteria. Another day, another post.

*Though not as much as I dreaded getting bit by a leech. I never did get bit, though I saw friends and siblings get nailed. Interestingly, Brother Phil noted this year that none of us have spotted a leech for several years. Wonder why that is?

The next sub-zone, starting at ~ 3 or 4 feet deep on our ponds, is the Floating Plant sub-zone, dominated by Waterlilies, and- as I was pleased to notice- Floating Pondweed. The Pondweed leaves are much smaller, which may be part of the reason I never noticed them before.

Both Waterlilies and Pondweeds use the buoyancy of the water- rather than the support of their stems- to position leaves and blooms on the surface and both- as I mentioned in the Idaho-Lily post, evolved this “Lily-Pad-Schtick” independently. Waterlilies are ultra-“primitive” dicots, having branched off from nearly all the other angiosperms way early in the history of flowering plants, while Pondweeds are monocots, more closely related to the nearby Rushes and Pickerelweeds. 5 Kezar ponds BTW supports both genera of common North American Waterlilies: the white/true-petaled Nympheae and the yellow/sepals-as-petals Nuphar blooms..

As you paddle away from the shore and clear the Waterlilies, if you look down right away, before it gets too deep*, you’ll see other plants below the water. This is the Submersed Plant Sub-Zone, characterized by plants that grow and flower entirely underwater.

*Polarized sunglasses help. But if you buy your cheapie-eyewear at Maverik, using the shadow of a canoe paddle to cut the sun’s glare off the water works fairly well.

There are a number of cool submersed plants growing down in this zone. One of the more interesting is Common Hornwort, Ceratophyllum demersum. Hornworts are entirely submerged, free-floating plants, from 3 to 9 feet in “height”, rooted in mud on the pond-bottom. “Rooted” is a bit of a misnomer; the plants have no real roots, but modified leaves that anchor them to the bottom. They do well in still waters in mud/soil rich in nutrients, and provide shelter to fish-spawn and snails.

Hornworts have completely submerged lives. Not only are they “rooted” underwater, but unlike plants of the Emergent and Floating sub-zones, they flower and are pollinated underwater. Hornwort pollination is a weird analog of wind-pollination, pollen grains carried slowly through the waters in the incredible, one-in-a-zillion chance that they’ll wind up at a female Hornwort flower, which of course, a fair number of them manage to do.

Side Note: Plant People will get why this next part is Way Cool. If you’re not a Plant Person*, you may need to go back and read this post and the “Botanical Spotlight” in this post to get it.

*Oh don’t be like that. You know what I’m talking about. You’re rolling your eyes and thinking “boooring.” Let me tell you what: We Plant People see a whole world the rest of you Plant-Blind folk don’t see. Plus we make fun of the rest of you when you’re not around.

When describing plants in this blog, I usually try to mention what kind of plant it is and give some idea of what it’s related to. When describing flowering plants, part of this includes IDing the plant as dicot or monocot. But I can’t do this with Hornwort because botanists haven’t agreed on what it is. For some time it was though to be a basal offshoot of the angiosperms, similar to Waterlilies. But more recent genetic analyses have suggested that it’s a basal offshoot/sister group of either the monocots or eudicots. In other words, when the monocots/eudicots branched off from the “primitive” dicots way back over 100 million years ago, and then broke off into monocots and eudicots, Hornworts may have been part of a third branch that subsequently broke off from either the monocot or eudicot line. Today there are tens of thousands of species of both monocots and eudicots, but just 6 species of Hornworts worldwide. Isn’t that freaky? These watery weeds growing out of the muck may be the sole survivors of a 100M+ year-old line of life as ancient as monocots or eudicots.

Tangent: We’ve come across several of these “lone survivors” of ancient lines before, including Mormon Tea, Gingkoes and Cycads. These living fossils are fascinating not just in and of themselves, but because they highlight the common recent ancestry of the vast majority of living species. Think about angiosperms (flowering plants). It’s thought that they evolved once, from a common ancestor*. Today, maybe 150 million years later, they rule the world. And there are similar stories for everything from songbirds (Passerines) to bats to primates. When each of these lines got its start, there were thousands of other living things around whose lines have since dead-ended. A few dozen crucial splits/breaks have defined so much of the history of living things. And if one of those splits/breaks offshoots hadn’t worked out, or if another that almost worked out did work out, well it makes you think about how the world might have turned out. (Or how other worlds maybe did turn out.) The 6 species of Hornwort range worldwide- they’re not in obvious danger of extinction anytime son. Makes you wonder if there the last of their line, or the bridge to some future, diverse order that will dominate the world.

*Because of the pollination-weirdness described in this post.

The Hornworts and other submersed plants seem to give out at somewhere around 10 or 12 feet of depth around the ponds, marking the end of the Sumbersed sub-zone and the entire Littoral Zone. Beyond this is the Limnetic Zone, marked by a lack of higher plants on the lake bottom. But the Limnetic Zone in turn is in turn divided into 2 horizontal zones. The upper waters, extending down to the ~10- 15 foot depth of the end of the Littoral- are mark the Euphotic Sub-Zone, where photosynthesis is still carried out by free-floating algae and cyanobacteria. Below this level is the Benthic Sub-Zone, where no plants grow.

When I snorkeled down to the bottom, I was diving down to the pond equivalent of alpine tundra; the little light that reached there was too meager to support any plants. That’s why the scenery was so uninteresting. On the deep lake bottom, there is life, but it tends to be teeny things- arthropods and such- that work their way through the mud, some feeding on the detritus that falls slowly from the living world above, others on each other. It was also a bit spooky down there- dark, cold and quiet. On the deeper dives I felt out of place and unwelcome, and kept catching myself kicking quickly back up toward the growing light above.