Wednesday, September 30, 2020

Algae Impersonators at Smoyer Park Pond

For most, perhaps all of the summer, open water was only a memory at Smoyer Park's pond. In its place was a layer of green, molded into static swirls that blotted out what in previous years had been a play of light and wind on water. It's like closing the curtain on a stage.

Though I'd seen a pond in North Carolina similarly coated shore to shore, the disappearance of open water in Smoyer Park came as a surprise. What was it, and had it happened before? One regular walker in the park said it had never been as bad as this year. 

An older photo from early September, 2014 shows just a little algae or algae-like growth accumulated along the shore, offering more evidence that this year is different. 

I mention "algae-like" because not all accumulations of green growth on ponds are algae, as became more evident as we took a closer look at this year's green growth in Smoyer Park's pond.

The closer look was prompted by a link in a Sustainable Princeton email to an NJ Spotlight article about the increasing number of lakes in NJ beset by harmful algal growth, and the likely link to nutrient pollution flowing into waterways from fertilized lawns, farm fields, and pavement. We tend to think of nutrients like nitrogen and phosphorus as beneficial, but excess nutrients in nature tend to cause harmful chain reactions. In a waterway, they can lead to blooms of algae, which then die and decompose, sucking up the dissolved oxygen needed by fish. Some species of algae produce toxins, such as those alleged to have recently killed hundreds of elephants in Africa.

I contacted Jenny Ludmer, who lives near the park and takes a great interest in local nature, and suggested the possibility that a new algae might be causing the excessive coverage in Smoyer Park. As an example of recent changes, a strange algae has shown up in early spring in one of my backyard miniponds the past couple years. I also looked up the once pristine lake of my childhood, Lake Geneva in Wisconsin, and found that algal growth stimulated by rising temperatures and nutrient pollution, plus an invasive plant named starry stonewort, are now interfering with boating and swimming.

Jenny and I discussed whether the green was duckweed or algae. She took another look and sent this photo that made it look like the duckweed had been coated in a layer of green goo. Concerned about the potential for toxins, she also sent some photos to the state DEP, which promptly dispatched someone to take a sample. It sure looked like algae, and yet the state report showed "HAB not present," meaning no harmful algal bloom. They found a little Cylindrospermopsis--a cylinder-shaped blue-green algae--and not much more.

Finally, I returned to the coated waters of Smoyer Park for a closer look. Was it algae that was cheating us of any reflection of the sweetgums now turning glorious colors on the far shore?
A closeup of the surface showed scattered duckweed, but something else as well, much smaller and much more numerous. 
The small green particles were gritty to the touch. The internet, as usual, offered an instant answer: watermeal, in the genus Wolffia, which includes what wikipedia calls "the smallest flowers on earth."

It's a native species, but can be expansionist in its behavior. Warming waters and runoff from chemical fertilizer used on lawns in the small watershed that feeds the pond are some potential causes of this year's "over the top" growth. 

Smoyer Park's is not the only pond having this problem. Brooklyn Botanic Garden included a small pond in a stream corridor they carved into their grounds a few years ago. Their pond's first two years of existence were marred by rampant algal growth, but this year, its watermeal that has moved in. They are hoping that over time, nature's checks and balances will take hold. But the example of an older pond like Smoyer Park's suggests that time is no longer the mender it once was.

For anyone wanting to report potentially toxic algae outbreaks, there's a form at this link.

Tuesday, September 22, 2020

Autumn Clematis and the Really Big Show

Even now, as the flowers begin to fade, 

autumn clematis makes this lamppost look like it's wearing a voluminous fur coat. 
It's been a good year for autumn clematis, whose big floristic show revved up in these parts nearly a month ago, caught in a photo where a cascade of flowers-to-be was piggybacking on a neighbor's fenceline. 

There is great appeal in the blooms, and yet this vine should come with a warning sign.

In my mind, though not in the garden, I pair the nonnative Autumn clematis (Clematis terniflora) with the native virgin's bower (Clematis virginiana), which also has white flowers and a sprawling habit. An easy way to tell the two apart is the leaves, which are toothed in the native, rounded in the nonnative. The native's flowering comes earlier in the summer and lasts a week rather than a month.

Together they tell a familiar story, in which the native has become comparatively rare. Years back, I took this rarity to mean that the native was less aggressive, but in fact the native when planted in the garden has proven just as hard to control as the introduced species. While sending up vines that grow over other plants, as you'd expect of a vine, both also spread underground, popping up in all sorts of places where you had other plans. 

Why is it the nonnative that can be seen covering a whole side of an abandoned parking lot in Montgomery north of Princeton? 
or lining the road to Cape May Point State Park? 

There are books that claim that nonnative invasive species are somehow superior to the natives, and that we should embrace these "winners" rather than counter them. Hopefully that dubious premise has faded into obscurity, unlike so many other dubious premises that now strut their stuff on the national stage.

More likely, the autumn clematis's capacity to grow unhindered is due to its unpalatability to deer and other wildlife. That would explain why the native virgin's bower is rare in local nature preserves while it runs rampant in my garden in town, where deer seldom venture. 

Periodically, I head down the great eastern piedmont from Princeton to North Carolina, where I've been involved with saving some rare habitat known as piedmont prairie. This small remnant on the outskirts of Durham, NC contains a clematis that will seem odd to anyone accustomed to clematis being a vine. This one, called curly top, Clematis ochroleuca, grows a foot or two tall in full sun and special soils formed from the underlying diabase rock. Princeton has lots of diabase rock along its ridge, which also hosts rare species, though not the same ones as in NC. 

The name "curly top" might come from the way the flowers curl downward, or from the curly seedheads that are also characteristic of the more common kinds of clematis. 
Another clematis in the piedmont prairies of NC is leatherflower, Clematis viorna, a small vine whose flower also points downward. 

Witness a high quality piedmont prairie, and you'll see how rich and diverse an intact native habitat can be. Though cheated of the periodic fires that used to sustain them, prairie remnants have persisted here and there, mostly under roadside powerlines where trees were not allowed to shade them out. I've rescued plants from a few that were being lost to development, and marveled at how each shovelful would contain four or five species. Nature was demonstrating how co-evolution moves towards a rich coexistence. Presumably, each species is limited in some way, most likely by herbivory, from running roughshod over the others. 

Witness that, and a monoculture of autumn clematis will look both showy and disturbing. 

Friday, September 04, 2020

A Monarch Butterfly Status Report

Around mid-summer, I begin wondering how the monarchs are doing. Last summer, in 2019, they were more numerous than usual in the Princeton area, and as I googled for news of their numbers in 2020, it was with the expectation that their population was on the upswing. Surprisingly, their overwintering numbers in the mountains west of Mexico City were down dramatically. The count comes out in March, just before they begin their journey north, and was down by half compared to the winter of 2018/19. 

The low count this past winter was due in part to less than favorable migration weather last fall. Warm weather in the north delayed migration southward, and a drought in Texas left little nectar for the monarchs as they funneled through Texas on their way to Mexico. From Princeton, that flight is about 2500 miles, powered by the liquid sunlight of nectar.

This summer, I saw one every few days. Here's a male visiting Joe Pye Weed in our backyard. 

You can tell it's a male by those two spots on the back wings. 

The monarch has a delicate look, but a powerful flight. A single beating of the wings sends it rocketing forward at unexpected speed. 

One of summer's finest moments can be spent watching a monarch navigate a garden. In our backyard, masses of variously sized wildflowers form a kind of mountain range with peaks and valleys that the monarch masterfully navigates just above. Turning on a dime, coasting, darting this way and that, the monarch's flight can seem like whimsy, or an incredibly efficient and complete survey of a garden. 

Sometimes a monarch visits every section of our garden without landing, then heads off. What was it looking for? A mate? A milkweed to lay eggs on? Clearly not nectar that other more predictable insects are busy feasting upon. Oftentimes, the monarch's motivations are an enigma.

One time this summer, I witnessed a monarch whose intent was very clear. In the "Veblen Circle" of wildflowers at the botanical garden we're creating next to the parking lot at Herrontown Woods, there's a mix of purple and common milkweeds in sufficient numbers to satisfy a monarch caterpillar's voracious appetite. Yet until this summer, I had never seen a female monarch land on one.

August 7, however, a monarch came along and perched on the side of a leaf, then bent its abdomen around and under to lay an egg on the underside. All I had was an iPhone to record the moment, and didn't dare get close enough for a good photo, lest the monarch be distracted from its mission.

Though we can witness, appreciate, and take small steps to support any monarchs that come along, our capacity to influence their destiny is limited. As Monarch Watch Director Chip Taylor explains on his highly detailed blog, "High numbers in the northeast do not translate to high overwintering numbers." In other words, we can support monarchs by planting milkweed and other wildflowers, but their fate is largely being determined by weather and land management playing out elsewhere.

A 2019 New Yorker article with a less than auspicious title, "The Vanishing Flights of the Monarch Butterfly," quotes Chip Taylor describing how a banner year in 2018 was largely due to the favorable weather the monarchs experienced at various stages in their migration. With humanity still on its climate-radicalizing fossil fuel treadmill, and massive misuse of herbicides killing milkweed in farm country, the cards are increasingly stacked against monarchs getting lucky with the weather. The "inland hurricane" that swept through Iowa in August seemed an example of the increasing extremes the monarchs face.

Still, there is the delicate, improbable power of their flight, and the promise of an egg. Nature is incredibly resilient if given a chance. There are raingardens to plant and milkweed to propagate. Common and purple milkweeds spread underground, making it easy to dig one up and start a new planting that will soon expand on its own. So much tears at the foundations of our world. Let the odds be what they may, to care and to act defines who we are. 

The best source I've found thus far for updates on monarch status, and potential for participating in a larger effort, is the Journey North website: