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Racing Tides

Scientists make the most of a short time window to study the intertidal.
January 30, 2017

4:00 a.m.

The waters off Calvert Island are smooth as glass. Dawn has yet to crack. Our headlamps bob down the gangway of the Hakai Institute dock, the taste of hastily swallowed coffee in our mouths. We’re getting up at this absurd hour to go to the beach.

Today’s goal is to survey the biodiversity of creatures living in the strip of land around the shore called the intertidal zone. The intertidal zone is covered in water at high tide and exposed at low tide. Scientific surveys can take awhile, so scientists have to maximize their snorkel-free time here by heading out during the very lowest tides of the year.

Unfortunately for people who value sleep, these lowest low tides are happening very early on Calvert Island at this time of the year. The team can’t survey in the dark, but they can make sure they’re standing on the beach ready to start as soon as it’s light enough to scrawl a measurement or identify a worm.

sea cucumber
A California sea cucumber, unamused at being displayed on an oar. Photo by Ami Kingdon

“The zone only gets exposed for six hours,” says Hakai scholar and University of Victoria (UVic) PhD student Kieran Cox, who is leading the team today, “and we need all six hours and eight people to finish our work.”

Cox, who is irrationally cheerful at this hour, knows the drill well and directs the team with energy and succinct good humor. Cox and his team will survey 15 coastal sites scattered from Vancouver Island north to the BC Central Coast, a collaborative project with the Ecological Interactions Research Program at Vancouver Island University and UVic.

In April, he checked the tide tables for the year to find the lowest ones, and then planned their field season around those dates. The tides dictate everything—what to survey, when, and where.

4:30 a.m.

We pile our gear in dry bags and plastic containers on the dock. Field science mixes high- and low-tech: there’s a fancy laser level on a tripod wedged beside a red plastic colander made by Betty Crocker. A hint of dawn shows as we set off, towing a small aluminum boat behind us. The mountains start materializing out of the sky, girdled by thin bands of mist and cloud.

5:00 a.m.

We anchor off a small beach. The crew splashes over the sides of the boat, protected from the frigid ocean by hip waders and rubber boots. Cox and Kayla Mohns, one of the research technicians, set up the laser level on its tripod and turn it on. It’s still dark enough that the laser, used to measure the beach’s slope, draws lurid red bands across everyone’s chest like we’re being scanned at a grocery store.

Intertidal Science
The science team gets their gear ready, as the laser level measures the slope of the beach. Photo by Ami Kingdon

Cox and another research technician lay out transects, unspooling 30 meters of measuring tape from the high tide line out into the shallow water to create a grid. Mohns pinpoints the sites that they’ll sample on the freshly laid grid. Everyone works fast. The tide allows no do-overs.

It’s not a classically beautiful beach. This sloping mudflat resembles a slushy winter sidewalk. A slippery skin of algae coats the mud, which is dotted with pools of seawater left over from the last high tide. White clamshells crunch underfoot with a sound like ice.

At each of Mohns’s orange-tape-flagged sites we drop a square of white PVC piping and the survey begins. We start to count the creatures living on the surface of the beach, the epifauna. Then, we dig up the surface mud layer and dig through the chocolate brown sludge, seeking out the so-called “infauna”: worms, clams, and crabs that live within the muck. Someone finds a shrimp, and calls everyone over to look; another team finds a wriggling baby sculpin, one of the more common fish.

The tide ebbs lowest at 7:00 a.m., so we start halfway up the beach in the mid-intertidal then move out to the low intertidal, snatching precious data from the mud. As the water creeps back up, we’ll finish in the high intertidal at the forest’s edge. The race is on.

7:00 a.m.

At its lowest ebb, a new ecosystem emerges that is almost always underwater—the subtidal. I gape as I step carefully over red-pink anemones that deflated into masses of goop when the tide went out. Mohns pulls up a sea cucumber the size of a can of Pringles on a wooden oar.

Lying on the sand I notice chunks of what looks like rubber, industrially smooth and shaped like discarded tires. I say with disappointment that someone has left garbage here. But Mohns laughs and tells me they’re eggs from a moon snail. Sure enough, the “rubber” is sand, epoxied into a perfect collar. I want to keep exploring, but the tide turns, and it’s all hands on deck to sample the lowest reaches of the beach.

Moon snail egg collar
The distinct egg collar of a moon snail next to an empty shell of an adult. Photo by Ami Kingdon

10:00 a.m.

The water is crawling higher up the beach by the minute. Jackets are shed and hung on a fallen tree up the shore. The flats smelled benign at dawn. Now, as the Sun clears the trees, the muck smells distinctly funky.

10:30 a.m.

We race to finish the final plots. The team scribbles out their last labels and measurements, huddled on barnacle-encrusted rocks as the water creeps up their waders. The beach has vanished beneath the waves.

But the data we’ve gathered will help Cox and his supervisors—Sarah Dudas, a Canada Research Chair at Vancouver Island University, and Francis Juanes, Liber Ero Professor of Fisheries at UVic—build up a long-term monitoring dataset that can be shared with other scientists and researchers. They can then analyze how humans, climate change, and other stresses are impacting this ecosystem.

Cox says once they have the baseline, they can answer important questions about how it changes. “How does diversity respond to us?” he says. “How does diversity vary along the coast? How does diversity change throughout the year?”

As we pull away on the boat, I stare down at the submerged beach. Fish and red rock crabs dart across the sand. Threadlike algae and moon jellyfish no bigger than an Oreo drift in the greenish water. In a few hours, the tide will creep back down again. When we leave the beach denizens will go on with their cyclical lives.

Cox and the team will wake up tomorrow before dawn to go to a different beach. And race the tides all over again.

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