Friday, February 16, 2018

What's living under the ice?

            It’s one of my fondest memories of childhood, ice skating on the one-acre pond in my backyard in North Kingstown. We often skated several times each day – before school, after school and even after dinner, thanks to the lights my father installed to illuminate the area. And weekends were for skating parties, hockey games and general silliness on the ice.
            That’s also when I first began to wonder about the creatures that were living in the water beneath the ice. Occasional spots of clear ice seemed to serve as a window into the underwater world, and I never ignored an opportunity to lie on the ice to see what was there.
I often saw very little, just mud and leaves and floating sediment. But every once in a
Cartoon by David Chatowsky
while, something else came into view – mostly aquatic insects, fairy shrimp, tiny fish and, once, a giant snapping turtle. I’ll never forget lying face-to-face with that snapper, wondering if he was frightened of me and worrying that he was as cold as I was.
            To this day I still think about that turtle every winter. I had assumed that most turtles bury themselves in the mud and hibernate through the cold months, but apparently not all do. Snapping turtles are particularly cold tolerant and well known for remaining active beneath the ice, though even they reduce their metabolism and move very slowly.
            Peter Paton, a reptile and amphibian expert at the University of Rhode Island, said that he has seen wood frogs, spotted turtles, and spotted salamanders swimming under the ice on occasion. It’s more likely to happen, he said, during cycles of melting and refreezing, especially during rainy periods in late winter. That’s when many frogs and salamanders begin to move from the land to the ponds in search of a mate. When temperatures plunge at night and the ponds refreeze, it may lock the animals in, but they seem to survive just fine.
            Aquatic creatures that cannot live on land – like fish, fairy shrimp and insect larvae – are locked beneath the ice, too, but they’ve evolved to live through such conditions and thrive. For some, the cold, icy conditions are a necessary trigger for the next stages of their growth and development.
            And as any ice fisherman will tell you, there are plenty of fish that remain active beneath the ice. That’s because there is still plenty of food available to sustain them: crustaceans keep creeping along, algae still bloom, plants still photosynthesize when enough light penetrates the ice, and tiny zooplankton continue to swim, feed, and reproduce.
            The larval form of dragonflies, stoneflies and mayflies are among a very few aquatic insects that remain active beneath the ice throughout the winter. Some can even live a short time encased in ice, which is especially helpful when shallow ponds freeze all the way to the bottom. And when the ice eventually melts and reaches a certain temperature, the bugs transform into their adult form and fly away.
            Which is what I’d like to do about now – fly away south. My ice skates no longer fit, our ponds seldom freeze thick enough to skate on any more, and general silliness on the ice is no longer as attractive as it once was. But I’d relish another opportunity to go face-to-face with a snapping turtle lurking beneath the ice.

This article first appeared in the Independent on February 15, 2018.

Friday, February 9, 2018

Hydrothermal vents speed development of deep-sea skate eggs

            A team of scientists from the University of Rhode Island and the Charles Darwin Research Station exploring the seafloor northwest of the Galapagos Islands in 2015 made an unexpected discovery. Large numbers of egg cases of a deep-sea skate – relatives of sharks and rays – were observed adjacent to the hot water emitted from hydrothermal vents, which the scientists said the skates use to accelerate the development of the embryos.
                It is the first time such behavior has been recorded in marine animals. The discovery is published this week in the journal Scientific Reports.
                Brennan Phillips, URI assistant professor of ocean engineering, was leading the operations team of remotely-operated vehicle operators during the expedition to explore the underwater
Robotic arm picks up Pacific skate egg from ocean floor (Ocean Exploration Trust)
mountains around the Galapagos. He said they didn’t recognize the significance of the aggregation of skate eggs until much later.
                “We were on a really deep dive in a hydrothermally-active rift valley, with walls 30 meters tall on either side, and the ROV was meandering back and forth looking for vents,” Phillips explained. “We started noticing all these egg cases, and we recorded their location and collected a few but then just kept going.”
                Later, when the egg locations were analyzed and compared to hydrothermal vent locations and recorded water temperatures, the scientists concluded that the eggs were likely intentionally placed by the skates where the water was warmer than average.
                In total, 157 mobile-phone-sized egg cases were observed, which DNA analysis revealed to be from the Pacific white skate (Bathyraja spinosissima). About 58 percent of the egg cases were found within 20 meters of a black smoker, the hottest kind of hydrothermal vent, and 89 percent of the egg cases were laid in water that was hotter than the background temperature of 2.76 degrees Centigrade.
                “The eggs weren’t right next to the active vents, because the water can get so hot – hundreds of degrees – that it would kill them,” Phillips said. “We found most of them in the lukewarm water not far from the vents and near some extinct vents.
                “The kicker is that we showed our data to a bunch of shark experts, and they had seen anecdotal evidence of shark and ray egg cases near hydrothermal vents, but they never had the data to put the story together,” he added.
                Several land animals have been recorded laying their eggs in similar situations. A rare bird native to Tonga, the Polynesian megapode, often nests in volcanically-heated soils, for instance. Fossils of some sauropod dinosaurs of the Cretaceous era are believed to have done so as well.
                This isn’t the first time Phillips has observed unexpected behaviors by shark family members in heated water. In 2014, he investigated an underwater volcano near the Solomon Islands in the western Pacific Ocean, where he watched several species of shark swim right through the bubbling hot water in the volcano’s crater.
                “Our cameras caught images of schools of sharks, smaller fish and even jellyfish living in the hot acidic plume,” he said at the time. “This presumably toxic environment supports a whole community of life, even though every once in a while it blows up.”
                Coupled with his hydrothermal vent observation, Phillips believes that sharks, rays and skates – which evolved about 500 million years ago – have adapted to the unusual conditions.
                “Seafloor volcanism comes and goes, and it is often one of the causes of mass extinctions,” he said. “It’s interesting to me that we’re seeing sharks and skates thriving around volcanoes and vent sites, like they’re especially resilient and have evolved to withstand the hot water environment.”

Thursday, February 8, 2018

Beach birds: Geology's link to avian abundance

            One of the rarest breeding birds in the Northeast finds the beaches of Rhode Island particularly appealing in summer – not for swimming and sunbathing, of course, but for nesting and feeding.  Piping plovers, sparrow-sized pale shorebirds listed as threatened on the U.S. endangered species list, breed more densely in Rhode Island than anywhere else in their Atlantic coastal range.
About 90 pairs of the birds – up from just 10 in the 1980s – can be found laying eggs and raising their chicks on a half dozen beaches in the state, from Goosewing Beach in Little Compton to Moonstone Beach in South Kingstown and Napatree Point in Westerly. They choose
Piping plover nest at Napatree Point (Peter Paton)
those particular beaches for reasons of geology as much as for any other characteristic. According to ornithologist Peter Paton, they seek ocean-facing beaches where crashing waves create a sizable wrack line of seaweed and other debris for feeding; wide unvegetated beaches that give them plenty of visibility to watch for approaching predators; and sand that frequently blows over the dunes to create washover fans for nesting habitat.
“Piping plovers are particularly adapted to open beach areas created by storms,” said Paton, a professor of natural resources science at the University of Rhode Island. “When Hurricane Sandy came through and pushed sand back into the dunes behind the beaches and created big sand fans, that provided them with prime nesting habitat.
“But if the storms and sea level rise push beaches farther and farther into vegetated upland areas,” he added, “or if there’s no place for the beaches to move, it could be a serious issue for them.”
            The plover/geology connection doesn’t stop there, however. The plumage of the birds is sand colored, allowing them to more easily blend in with their environment when they are wandering the beach looking for food or when incubating their eggs. And their nest is generally placed in an area of sand with scattered small cobblestones, because the eggs are camouflaged to look like the stones.
            Least terns, gull-like birds that are also on the endangered list, choose the same beaches as the plovers for nesting, and for similar reasons. American oystercatchers do, too, though their preferred nesting habitat isn’t nearly as narrowly defined. The large black-and-white shorebird with a bright orange beak seeks open undisturbed sandy beaches near shellfish beds for feeding. Several other bird species raise their young in the vegetated dunes adjacent to beaches, like spotted sandpipers and savannah sparrows, and even more birds prefer nearby salt marshes.

            The link between birds and geology isn’t one that many birders or geologists spend much time thinking about, but the link exists nonetheless. What the birds seek in the geology of their preferred beach varies from species to species. The grain size of the sand matters to some birds, as does the slope of the beach, whether it has an adjacent coastal pond, and how protected it is from waves and storm surge.
            Luckily, Rhode Island’s beaches are highly variable, providing many of the elements required by a wide variety of birds for feeding and nesting. Unlike the shoreline of New Jersey or the Outer Banks of North Carolina, where the beaches are much the same for hundreds of miles, a short walk on an Ocean State beach often turns up considerable geologic diversity. And that diversity is the result of the region’s glacial history.
            “One characteristic of our glacial shorelines is the heterogeneous sediment types and land forms that intersect the shoreline,” said Bryan Oakley, a coastal geologist and assistant professor at Eastern Connecticut State University, who has studied the Rhode Island coastline for nearly a decade. He noted that the region is dominated by two types of sediment: till, which consists of what he calls “a poorly sorted mixture of everything from clay to gravel deposited directly by the ice sheet,” and stratified deposits of sand, gravel and silt from the rivers and lakes formed by the melting glacier.
            “Till produced things like Green Hill and Quonochontaug and Point Judith, boulders without a lot of sand in front of them,” Oakley explained. “The Matunuck Headlands from Cards Pond to East Matunuck is comprised of stratified deposits. The beaches themselves might not look too different – you’ve got a pile of sand with a dune behind it – but what you find further down differs from place to place. There are differences in grain size that relates to the underlying glacial geology.”
            Considerable variability exists among the beaches in Narragansett Bay as well. According to Janet Freedman, a geologist with the Rhode Island Coastal Resources Management Council, the sand and sediment in bay-facing beaches are often a bit muddier than those on the south shore due to a division in the glacial ice sheet that deposited finer grain sediment, mica schists and sandstone on beaches in the bay. “Along the south shore the glacial material is more granitic, and that is more of a coarser grain size,” she said. “A beach is just a pile of sediment,” added Oakley. “If you have a source of sand and gravel suitable for the wave and tidal energy at the site, you’ll have a beach. The difference in the bay is that there are lots of shoreline protection structures, so the beaches are armored to some degree, more so than we see on the south shore.”

            From a bird’s perspective, all of that geologic variability means a wide variety of food is likely hidden in the sediments waiting to be eaten. While just a handful of bird species nest on the state’s beaches, dozens more visit throughout the year – especially during migration – to bulk up on the tiny invertebrates that fill nearly every nook and cranny of the coastline.
            Although few research studies have been conducted about the creatures that live in the sand on New England beaches, Tim Simmons has become a local expert on the topic. A retired biologist who worked for many years for the Massachusetts Natural Heritage and Endangered Species Program, he has spent much of his career studying beach tiger beetles and other associated species in Massachusetts. He calls beach sand “an incredible ecological niche” for tiny amphipods, beetles, flies and other invertebrates.
            “People don’t see how alive a beach is,” he said. “They compare it to a desert, but that’s far from what it is.”
            Simmons said that some amphipods and beetles choose to live in the fine sands because that’s where they find it easiest to burrow beneath the surface. Others choose coarser sands where there are larger spaces between the grains, while still others prefer the saturated sand closest to the waterline.
            “There are a whole lot of things in there that you can’t really even see unless you’re wearing polarized sunglasses,” he said. “I remember watching shorebirds feasting on something, but I couldn’t see what. Every time a wave came up and went back down, the birds ran in to grab something. Turns out it was the larvae of a polychaete worm. The birds could see them but I couldn’t until I put on my sunglasses.”
            Because the composition of the sand on many beaches changes from season to season and storm to storm, many of the invertebrates that live in the sand must be prepared to move when the conditions change or when their food supply shifts.
            “Some beaches that are perfect habitat for some species in the summer are rocky and full of boulders in winter with nowhere for the creatures to hide,” Simmons said. “In the mud at inlets to coastal ponds, you get a different suite of species than in the sand. But then when washover fans carry beach sand over the mud, the mud creatures have to pack up and move.”
            Those that can’t move fast enough get washed away or become food for something else. The predatory tiger beetle that Simmons studies is capable of rapid movements and can often detect vibrations caused by the eroding beach in time to emerge from their burrow and escape to a safer location. They move from season to season, too, traveling to the dunes in winter and back to the sand near the wrack line in summer.
            “There’s also a grasshopper that’s almost completely bound to dune blow-outs, where a storm has blown out the vegetated face of a dune and created a bowl-shaped depression,” he said. “As juveniles, they’re flightless and hop around, and birds often forage there for them in the early morning.”
            The wrack line is another beach ecosystem that changes daily and where another unique suite of creatures can be found. A 2004 study by a URI graduate student recorded an abundance of species that spend at least part of their lives in the wrack line. Some eat the decomposing seaweed or use it as cover from predators and extreme temperatures, others lay their eggs there, and wolf spiders make daily migrations from the dune grass to the wrack to prey upon amphipods.
Shorebirds of many varieties – from piping plovers and ruddy turnstones to whimbrels and semipalmated sandpipers – eat anything and everything they can find in the wrack.

A visit to Napatree Point further illustrates this link between birds and geology. The mile-long sandy peninsula extending southwest from Watch Hill in Westerly has experienced dramatic changes in the last 100 years – from being the site of 39 homes prior to the 1938 hurricane to a somewhat pristine barrier beach today that shifts with almost every storm.
Riding out the peninsula on an ATV, Janice Sassi, manager of the Napatree Point Conservation Area, pointed out the wide sandy beach on the ocean-facing side, where waves crash loudly and piping plovers are often observed feeding on flies and amphipods in the wrack line during the breeding season. It’s here that wintering and migrating sanderlings adroitly chase the receding waves to quickly grab larval crabs that briefly expose themselves to filter feed, then the birds dash shoreward to avoid getting their ankles wet as the next wave approaches. Closer to the point, where seaweed-covered boulders divide the shrubby dunes from the sea, purple sandpipers forage for arthropods and mollusks amid the plant material on the waist-high rocks.
On the opposite side of the dunes, just 75 yards away, a narrow beach faces the quiet Little Narragansett Bay, where thousands of migrating shorebirds feed on horseshoe crab eggs deposited beneath the sand at the high tide line in May and June; where the region’s highest concentration of oystercatchers forage in the adjacent mussel beds; and where about 40 other species regularly search for a meal among the rocks, seaweed and sand during migration, including northern harriers that hunt for mice and voles in the dunes in winter and nesting osprey that hunt for fish wherever they can find them in summer.
“There are so many birds here in the summer and during migration that it’s like you’re at the mall during the holidays,” said Sassi, noting that she and her volunteers work hard to ensure that the hordes of boaters and beach-goers that also visit Napatree in summer do not disturb the birds.
Bryan Oakley said that while the sand is not likely much different on one side of the peninsula or the other, the wave energy is certainly lower on the bay side, making for better habitat for many species of birds and their prey. The calmer water on the bay side is also home to abundant minnows of several varieties, the perfect meal for the terns that nest nearby.
“As often as I’m here, it’s different every single time,” Sassi said. “The light is different, I see something different, and yet the birds are always here. Where else can you go where you have bay on one side, ocean on the other, you have a lagoon, the dunes are allowed to migrate as they’re supposed to, and you have shrublands and all kinds of wildlife. To realize that the geology plays such a role in attracting the birds is amazing.”

This article first appeared in the Winter 2018 issue of the magazine 41 North.