Tides

The Science and Spirit of the Ocean

Jonathan White

• Editore: Trinity University Press
• Anno: 2017
• ISBN:
  9781595348067
• Argomento: Biological Sciences
• Categoria: Ecosystems & Habitats

In Tides: The Science and Spirit of the Ocean, writer, sailor, and surfer Jonathan White takes readers across the globe to discover the science and spirit of ocean tides. In the Arctic, White shimmies under the ice with an Inuit elder to hunt for mussels in the dark cavities left behind at low tide; in China, he races the Silver Dragon, a twenty-five-foot tidal bore that crashes eighty miles up the Qiantang River; in France, he interviews the monks that live in the tide-wrapped monastery of Mont Saint-Michel; in Chile and Scotland, he investigates the growth of tidal power generation; and in Panama and Venice, he delves into how the threat of sea level rise is changing human culture—the very old and very new. Tides combines lyrical prose, colorful adventure travel, and provocative scientific inquiry into the elemental, mysterious paradox that keeps our planet’s waters in constant motion. Photographs, scientific figures, line drawings, and sixteen color photos dramatically illustrate this engaging, expert tour of the tides.

1 The Perfect Dance

Birds and Big Tides in the Bay of Fundy

It’s a strange thing that most of the feeling we call religious . . . is really the understanding and the attempt to say that man is related to the whole thing, related inextricably to all reality, known and unknowable. . . . It is advisable to look from the tide pool to the stars and then back to the tide pool again.

— John Steinbeck, The Log from the Sea of Cortez

When a late summer tide slips across the Bay of Fundy, it reveals miles of glistening mudflats. All that mud is filled with Corophium, a mudshrimp about the size of a rice grain. And every August, just as the mudshrimp population peaks, 700,000 semipalmated sandpipers descend onto these tidal flats. This bird is so small it fits in the cavity between two clasped hands, and so light you wouldn’t notice it was there.

Having flown 900 miles nonstop from the Arctic to this great Canadian bay, the sandpipers land weak and skinny. But not for long. In eight days on the tideline, they double their weight with mudshrimp. They’d better. If they don’t consume enough calories for the nonstop 2,500-mile trek over the Atlantic to their South American wintering grounds, they’ll drop out of the sky somewhere midocean. “It’s like taking off in your car across a wilderness, knowing there is only one gas station—exactly halfway. If you miss it, or if you don’t fill your tank to the brim before leaving, you simply won’t make it,” Peter Hicklin tells me.

Hicklin is a retired Canadian Wildlife Service biologist. He is recounting his thirty years of shorebird research—including two life-threatening accidents—as I steer a rental car between potholes and soft red clay. It’s early August, and we’re headed to Johnson’s Mills, a large tidal flat in Shepody Bay, New Brunswick. The roadside is overgrown with alder and black spruce, but at times it opens to sweeping green fields of hay and corn, punctuated by large gambrel-roofed barns and crisp white Victorian farmhouses. The muddy-brown sea, Shepody Bay to the west and Cumberland Basin to the east, is never far from sight.

“In the early 1970s we knew almost nothing about this place,” says Hicklin, his accent hinting at his French Acadian heritage. “The tidal flats were considered a dangerous wasteland—no one went out there. We knew Fundy had the largest tides in the world, but we didn’t know until recently that they have shaped everything that lives here, from the careers of scientists and fishermen to birds and fish and mudshrimp. If it weren’t for the tides, none of this would be here. Hell, I wouldn’t be here.”

“Shhhh,” whispers Hicklin as we park and walk to the beach. The tide is high, almost at its peak; small wavelets from a pleasantly cool onshore breeze lap the gray rocks and sand of the upper shore. People in light parkas and shorts hover by the roadside shrubs; they carry cameras with long lenses, spotting scopes on tripods, and sophisticated video equipment. Children lie on their stomachs in fireweed and mustard, propping up binoculars. They whisper and silently swat mosquitos, repositioning themselves for the optimum view.

Like me, they have timed their trips from New York and Ontario and Wisconsin to arrive at just this hour. We—the birds and the people—are on two different migrations: the birds on wings across Arctic tundra, we in automobiles across paved highways, together balancing for a moment on the crest of a Fundy high tide.

Semipalmated sandpipers above the Bay of Fundy.

If I had somehow floated into the bay on driftwood from points south, I might have drifted in and out again without noticing a thing. But Hicklin’s “Shhhh” and the dedicated birders direct my focus. At first I don’t even see bird shapes, and then I realize the entire beach is shimmering with life. Other than a few small patches of sand and rock, the whole beach is a vibrating carpet of tiny, beautiful sandpipers. Thousands of them.

Occasionally the flock takes to the air. As one, they lift with the soothing hiss of a wave retreating over loose pebbles. Aloft, they swirl and dive and bank. One moment their white underbellies are turned toward the shore, and the flock disappears against the sunlit sky; as they turn again, a wave of gray rushes through the group and they appear as smoke—wispy and shifting, twisting and hovering. They are perfectly choreographed dancers—graceful, supple, arching, rhythmic. Watching them, we are speechless. No music plays, but the dancing flock is as musical as anything I have seen.

I first journeyed to the legendary Bay of Fundy in 2011. With a tidal range (the vertical measurement between consecutive high and low waters) of 54.6 feet, it competes with Ungava Bay, 1,200 miles north, for the world’s largest tide. I drove the 350-mile coast of Nova Scotia and New Brunswick, the Canadian provinces that border the bay, meandering from the lobstering and scallop-fishing regions at the bay’s mouth to the upper inlets of Chignecto Bay and Minas Basin, where the transition between tide and land blurs.

In the fishing community of Alma, I saw the incoming tide lift the fleet with a gentle hand. Because boats in these harbors are afloat only a few hours either side of high tide, I mused at how fishermen must schedule their comings and goings. Terry Rossiter, a fisherman working out of Alma for thirty years, told me from the tailgate of a red pickup, “Most people live by the sun, but if you fish Fundy you live by the moon and tides. You’re on a completely different schedule than everybody else.” The tide, mostly driven by the moon, changes by about an hour every day. So if Rossiter leaves the dock tomorrow at three in the morning, the next day it will be four, and a week later it’ll be almost noon. “We eat and sleep on that schedule,” he says. “When the tide’s flooding, whatever hour it is, the crews go to their boats, load things on—food and bait—get things ready. We have a failsafe mark on the wharf, so when the washboard hits that mark, we go, ready or not. If you miss the tide, you miss the whole day.”

Rossiter is one of hundreds who live by the moon and tides of Fundy, one of millions who live this way worldwide. In upper Fundy, weir fishermen take advantage of the tides by stretching a net between two poles at low tide. Cod and shad are swept in by the flooding tide and picked during the next low. At Dark Harbour on Grand Manan Island, harvesters collect the edible seaweed dulse during the lowest tides of spring and summer. These occur roughly every two weeks, coinciding with the new and full moons. Pickers in Dark Harbour call these dulsing tides, gathering night or day to handpick the ruddy, fingerlike fronds. They flourish in the lowest part of the intertidal zone, which is the area between high and low water. Hauled to shore in burlap bags, the wet harvest is spread to dry in the sun. Dark Harbour sits at the bay’s mouth and is the dulse capital of Fundy, exporting 75,000 pounds a year of this crispy, salty, high-mineral snack. Some goes to the United States, Europe, and Australia, but much of it stays in Canada, to be eaten raw or pan-fried as chips, baked in the oven and topped with cheese, or sprinkled on salads.

A growing population of Fundy scientists study the tide’s far-reaching and mysterious workings. Biologists examine how marine animals synchronize their life cycles with it. Geologists look at how currents shape the ocean bottom. Sedimentologists monitor suspended clays and sand that are stirred and redeposited. Oceanographers research tide anomalies—which is almost an oxymoron, since anomalies abound. Engineers improve devices that generate electricity from the tides.

Fundy’s tides shape the bay’s landscape and culture. What happens here happens to some extent everywhere. More than half the world’s population lives on or near the coast, and there is no coast or ocean without a tide. Fundy has an especially large tide, so it appears unusual, but the economic and scientific, social and biological dynamics at play here are also at play for billions of people across our watery planet.

Several days after my visit to Alma, I perched on a stack of fish traps in Hall’s Harbour on the Nova Scotia side of the bay and watched the water drain under the fishing fleet like a long exhale. At low tide, the harbor is completely dry. The boats—Petrel, Bacchus, Pretty Woman, and a couple dozen others—settled haphazardly on the gravel bottom. To survive these continuous groundings, Fundy boats are fitted with two keels instead of one. Grounding on a single keel is like trying to balance on one leg; the second keel allows the boat to settle on two “legs.” From my fish-trap seat, which didn’t move with the tide, I saw the boats sink below the dock like a setting sun, leaving only their radio antennae visible. At dock’s end, a sign reads, “When the tide is out, you have to go looking for it.”

Bay of Fundy fishing boats at high and low tide.

The Bay of Fundy Tourism Partnership describes for the many tourists three kinds of tides: vertical, wave, and horizontal. These are not scientific terms, but they’re fitting descriptions for tides everywhere. Hall’s Harbour is a vertical tide because the shoreline is steep and an onlooker can easily see a dramatic vertical difference between high and low water.

A wave tide—commonly known as a tidal bore—is a flooding tide that travels upriver as a single wave. Fundy has a wave tide on five rivers—the Herbert, Maccan, Salmon, Shubenacadie, and Petitcodiac—but there are eighty or ninety worldwide, with the largest on the Qiantang River in China and the Amazon in Brazil.

A horizontal tide occurs on gradually sloping shorelines where an ebb tide exposes acres—sometimes miles—of intertidal zone. Sandpipers like the horizontal tides of the upper Bay of Fundy because the mudshrimp are there. “It’s the perfect environment for these little shrimp,” Hicklin told me, “because they burrow into the mud during low tide and swim at high tide to feed.”

I first heard about the sandpipers, mudshrimp, and Peter Hicklin while talking to Rossiter in Alma. I met Hicklin shortly after, eagerly accepting his invitation to return the next year to see the birds. Before I made the trip, he asked that I bring three bottles of red wine from Oregon or Washington and a pair of cut-off jeans. “We can’t buy wine from those wineries,” he told me over the phone. “You’ll need the cut-offs because I’m going to take you out on the mudflats—that’s the only way you’ll really understand what’s happening here.”

Now I’m back beside Hicklin at Johnson’s Mills, having delivered the wine last night. He figures there are 140,000 peeps, as ornithologists call them, on the beach in front of us. Some are resting with their necks turned 180 degrees, some are preening, others are nervously pacing. “They’re roosting here,” Hicklin explains. “They’ve been foraging for twelve hours without a break, following the tide all the way out and then all the way back in. One bird will swallow about 16,000 mudshrimp during that time. At slack high water they rest for a couple of hours before the cycle begins again.”

A semipalmated sandpiper (not to scale).

Rest is a relative word for a bird with a heart rate of eight hundred beats per minute. Like its cousin, the rufous hummingbird, which for its size has the world’s fastest metabolism (one thousand beats per minute), the sandpiper’s fiery interior never slows, powering long flights and hours of foraging. What little rest a peep gets in Fundy, it gets amid the protection of the flock, which is perpetually alert. The flock watches for predators, including four nesting pairs of peregrine falcons that were reintroduced in the 1980s. These falcons, faithful to one partner and one nest year after year, raise chicks that are eager for a hunting lesson about the time the peeps arrive. An immature falcon is a bit gawky, but a falcon is a falcon, and sandpipers are no match for their speed and ruthless precision. They scatter at the first hint of a falcon’s shadow. But the daily losses are a small price for the flock to pay for Fundy’s bounty.

Between fueling up and watching for peregrines, the birds take little notice of us. Pressed against one another by the rising tide, they are so close we can study them without binoculars and spotting scopes. I see details of individual birds: delicate dark and light feathers; white chests with fine red and brown stripes; black rumps, legs, and eyes. Their short, slender black beaks are slightly blunt. They shift and jostle, wing to wing. Their constant murmur—cher, cher, cher—is as soothing as the light breeze.

Some scientists argue that the birds land here not by plan or mysterious genetic knowledge but simply from exhaustion in their long flight to Suriname, much as a car coasts to a stop when out of gas. Once here,...