Ducks, sundews, yellowlegs, and…

dragonflies, gentians, leaf beetles, and a yellowlegs encounter too

On a hot, sunny day, I sat with some friends on a big log, looking across Berners Bay toward Lion’s Head. The tide was out, exposing some big rocks off to one side. A female merganser with four half-grown ducklings cruised around, eventually disappearing behind one of those rocks. Suddenly two of the young ones came hurriedly splashing around to the near side of the rock. Hmmm, something was clearly awry! They then went behind the rock again but soon reappeared, with at least one of their siblings, on one end of the rock. There they all settled down into what a friend once called “a little pile of cuteness”. What caused the commotion and the retreat to the top of the rock? We blamed a seal, whose head surfaced next to the rock, looking intently where the duck family had been.

What about the female merganser? As she drifted between her resting brood and the shore, an eagle swooped down on her from behind. A narrow miss for the eagle, as the duck quickly dove down. An exciting day for the duck family.

We were staying in the Cowee Meadow cabin and found entertainment on our doorstep. A red-breasted sapsucker regularly visited the logs of the cabin walls, peering around at us on the deck, almost as if it were hoping for handouts. Later, a sapsucker went down to the ground by the fire-pit and picked up several woodchips, filling its bill and taking off with them. Why would a woodpecker scavenge chips when it could make its own, and what did it want with them, anyhow?

The front of the cabin was patrolled by a large dragonfly that flew back and forth between the creek on one side and the nearby trees on the other. A sudden flash of blue emerged from the trees and made a grab for the dragon, but I think the jay missed its mark; soon thereafter a large dragon was again patrolling the front of the cabin.

A few days later, still in the hot sun, Parks and Rec went to up to Cropley Lake. Great expanses of meadow were spangled with thousands of small white stars: swamp gentians. This annual plant is probably pollinated by flies (rather than bees), but there has been very little study.

bog-gentian-by-bob-armstrong
Swamp gentian. Photo by Bob Armstrong

A little lower down in the meadow vegetation, we found many tiny, white, five-petalled flowers of the round-leaf sundew. These small insectivorous plants were so common in some areas that they almost made a carpet, although not all were flowering. Experimental studies, comparing sundew plants with lots of captured insects to those with few captures, revealed that well-fed sundews grow better and make more flowers. The flowers have no nectaries, so they have little reward for pollinators; they are capable of self-pollination. However, insects, mostly flies, do visit the flowers at times. So flies can be pollinators but they are also prey for this plant. That seems self-defeating! However, they are likely to be different kinds of flies, as shown for the closely related long-leaf sundew.

On a walk out toward Nugget Falls one morning, I noticed that the cottonwood leaves had been severely damaged. So of course I looked more closely, and I found lots of small black larvae of leaf beetles. They had munched up the surface layers of both top and underside of the leaves, leaving nothing but a delicate network of leaf veins. Adults of these leaf beetles overwinter in the leaf litter and lay bunches of eggs in spring. The larvae pass through several molts as they munch and grow; the early stages (called instars) are often colonial, feeding in gangs; later instars are more independent. Some trees had been much harder hit by these beetles than others, but is that because some trees are just more susceptible, less well protected, or because of chance events when female beetles were laying their eggs?

A friend and I walked up to a meadow on the Spaulding trail to see if the long-leaf sundews were flowering yet. No, but we had an exciting time nevertheless. There were fair-sized shorebird footprints in the mud of the drying ponds and a shorebird was calling persistently from the top of a dead pine. As we turned to go, we got dive-bombed from behind—a close pass ruffled my hair. Then a second attack, accompanied, as before, by loud cries. (OK, OK, we are leaving anyhow…). Those greater yellowlegs were clearly defending something important, and at last we saw it (there might have been more, somewhere)—a big, tall chick, still fuzzy and flightless, sneaking through the sedges. So we went quietly on our way, leaving them in peace.

A group of five mallards in female plumage come to my home pond that same day. They foraged all around the edge, nibbling here and there. Then they went over to the bank on the far side and I expected them to climb up and settle down for a nap, which is what usually happens. But this time, the naps were delayed and the birds were almost hidden in the brush. The blueberry bushes started twitching and jumping, and I could see that the birds were reaching up to !!pick blueberries!! They cleaned out the berries on those bushes and finally settled in for a nap. I wonder how they learned that blueberries make fine snacks—so different from their usual fare.

Geothermal springs

the unusual ecology of a unique habitat

This essay takes me rather far afield from my normal trails, but there are so many fascinating aspects to these springs, and so many things still to be discovered, that I could not resist trying to write about them.

Geothermal sites are scattered over North America, with concentrations in the mountainous west. Water from rain or snowmelt sinks far underground, where the very high temperatures near the center of the earth heat the water. When that water rises to the surface through weak spots in the rocks, its temperature ranges from tepid to very hot. Depending on the amount of water emerging, the spring may be a geyser (if water is under strong pressure), or a warm pool, a seep or mud puddle, or just some steam. Some springs have notable concentrations of dissolved minerals, such as sulfur and salts.

Alaska has its share of geothermal sites—at least 79 of them. Most lie on a line from the Seward Peninsula eastward or on an arc from the Aleutians over to Southeast. Southeastern Alaska is well-endowed with hot springs, whose temperatures range up to about 180 degrees.

Who lives in hot springs? Of course that depends on the temperature (as well as water chemistry and the availability of oxygen); in general, the higher the temperature, the fewer the kinds of things that can live there. If the water is merely warm, there might be algae, some small crustaceans or molluscs, along with some beetles, true bugs, or flies—even a dragonfly! A certain kind of fly (in the genus Ephydra) likes it pretty hot: up to about a hundred and thirteen degrees F. Some hot-springs critters are such specialized ‘thermophiles” (meaning heat-loving) that they live only at higher temperatures. Unfortunately, there appear to be no studies of hot-spring faunas in Alaska, although Ephydra flies have been found in one of them. An obligately thermophilic water-mite is recorded from northern B.C., and I wonder if it might occur in Alaska too.

Few vertebrates can tolerate the conditions in thermal springs, but in North America, some little fish in desert pools have become quite famous—and perilously endangered. These are two species of pupfish (of the widespread genus Cyprinodon). The desert pupfish is less than three inches long, living in springs that may get as hot as a hundred and ten degrees F., reportedly feeding on snails that also must tolerate such temperatures. The Devil’s Hole pupfish is even smaller, about one and a half inches long; it’s found in only one pool in a Nevada cavern at about ninety three degrees F., and there are very few of them left now.

The only organisms known to thrive in extremely hot springs, with temperatures over a hundred and eighty degrees F, are certain bacteria and some similar-looking micro-organisms known as Archaea. These all have metabolisms that are very different from other organisms—their enzymes obviously have to be very heat-tolerant.

Thermal springs influence the vegetation that grows around them, in part because the annual frost-free period is longer. Species such as cow parsnip can grow taller than usual. A study in central Alaska near a hot spring (temperature about a hundred forty-one degrees F) discovered three species (a grass, a fern, and a violet) living around the spring hundreds of kilometers north of their usual geographic range. (That, of course, leaves open the question of how they got there…). Soil temperatures near a spring are often warmer, maybe allowing better growth of species (such as white spruce) whose roots don’t do well in cold soil.

Geothermal springs across the continents seem to attract more public attention as places for people to bathe than as subjects for scientific study. In contrast, the geothermal vents in the deep ocean have made headlines for their rich diversity in exceptionally extreme conditions.

Deep-sea hydrothermal vents are found principally in places where tectonic plates are separating and the sea floor is spreading as new material arises from deep in the earth. They are sometimes also found where two tectonic plates collide and one plate is pushed beneath the other, creating a deep trench. Underwater volcanos create some hot vents too. Some (not all) of these hydrothermal vents spew forth water at phenomenally high temperatures—up to more than seven hundred degrees F; at the great pressures of the ocean deeps, that water doesn’t boil. As the emerging hot water meets the extremely cold water of the deep sea, minerals are precipitated out, sometimes creating tall chimneys around the vent itself.

Nothing lives at those extremely hot temperatures inside the vents, but around the vents and chimneys there is often a very rich community of organisms. The base of the food chain there is made up of bacteria and archaea that metabolize sulfur instead of oxygen (which is scarce down there). An assortment of small crustaceans, shrimp, snails, mussels, limpets, tube worms, clams, and no doubt other things can be found on the warm sides of the chimneys. Farther up the food chain, crabs of several types are predators on the others. Certain species of fish called eelpouts are known from some vent systems, where they feed on tubeworms, crabs and other crustaceans. A tiny octopus (Vulcanoctopus) in the Pacific feeds from the sides of vent chimneys on swarms of amphipods.

In 2015, a deep-sea exploration near the Galapagos discovered a cluster of egg cases of the Pacific white skate near a geothermal vent in an area where the temperature was distinctly warmer than the ambient thirty-seven degrees F. Scientists thought that perhaps the warmer temperatures would speed up the normally very slow (over four years!) embryonic development time (although faster development might require more oxygen, which is limited in supply there). We don’t, apparently, know the fates of those eggs and embryos. A cautionary note is provided, however, by observations of a certain octopus on a deep-sea lava outcrop off Costa Rica. This octopus likes to lay its eggs in the lava crevices, where the mothers tend the eggs until they hatch. But on the geothermally warm parts of the outcrop, the embryos did not develop and the mothers looked stressed, leading the scientists to wonder if all the good, cool incubation sites on the lava were already occupied, leaving no room for the stressed, failed mothers, who had to use what space was left.