They look strange, out of place — and they are. Because they’re not from around here. The odd-shaped stones and boulders that pepper the flat, dark, silty bottom here at nearly 1,800 feet look like meteorites, each surrounded by a wide, shallow crater. They’re not from outer space, but many have traveled a vast distance on Earth — hundreds, perhaps thousands of miles, over millennia. And now my sub is face to face with one of three I’d encounter on our first dive in Zhemchug Canyon yesterday (Saturday) afternoon.
They’re called “drop stones” and it’s icebergs that do the dropping. As glaciers move across the land, rocks become incorporated into the glacial ice. Once the glaciers find the coast, they “calve” into ice bergs and travel vast distances floating upon the ocean, melting along the way and eventually, releasing their rocky payload.
One might think of a rock, even a hefty one, falling to the bottom of the vast Bering Sea as one of the more inconsequential events in the universe. But if you’re tiny, living in a world that’s flat and unprotected from the swift Arctic current ripping by, even a tiny pebble can mean the difference between survival or not. Corals, like the sublimely pink Swiftia pacifica we came across yesterday, appear to be growing right out of the brown silt. But a closer look reveals a small rock or pebble beneath the surface providing a holdfast against the current. If you’re a tiny critter like a shrimp, your only option is to get down into a hole, if you can find one. But holes don’t last forever — the current will eventually sweep them away. You can also try to get yourself up against the downstream side of an object — like a rock — so you’re not swept away with the current. Other than that, there aren’t many options across the flat, nearly rockless landscape of the bottom of this neighborhood in Zhemchug Canyon.
So if one day a huge rock comes a-plummeting out of the sky, it’s like a deluxe condominium suddenly appearing, and the shrimp don’t waste a moment moving in. They covered the lee side of the drop stones I encountered, wall-to-wall. The penthouse was reserved for critters like basket stars, corals, anemones, sponges or hydroids that could attach themselves firmly, then grab prey as they float by in the current. Fish like rocks, too, especially, well — rockfish. The brightly orange-colored shortraker rockfish lay against one of the drop stones. A prehistoric-looking Giant grenadier, perhaps 4.5 feet long, with its long, eel-like tail gently waving in the current, nestled by another. And I encountered the aptly-named bigmouth sculpin by the third.
During my last dive at Pribilof Canyon, I noted flatfish depressions and the fact that they were full of shrimp. Same here at Zhemchug. I was even treated to a flatfish hole digging demonstration by a small halibut that I “encountered” (translation: terrified). He was quite upset at being awakened by a noisy metal object with bright lights pointed at his face, so he swam a few body lengths, then flapped his flat body furiously and kicked silt up onto the top of his flatness until he was (or at least thought he was) invisible. That process, repeated millions of times, means sanctuary for a critical part of the food chain, including the many shrimp I spied enjoying their stay in a flatfish hole. Not only does the hole allow them to relax and not have to fight the current, but NOAA scientist Bob Stone points out that little eddies forming as the current runs by cause food particles to drop out of the water column. So if you’re a shrimp, you can kick back, not lift a claw, and let the food come to you. The current scours shallow craters around the drop stones, so shrimp living there not only get regular food deliveries, but also a high-rise view. I suppose that’s the Bering Sea definition of the good life.
It’s quite remarkable in nature how little things matter, like where a rock falls or where a flatfish rests. And there are big things in this world that threaten those little things, like taking too many fish from the sea, and global warming, which is already believed to be changing the patterns of the ice pack in this region, along with distant glaciers, and the would-be drop stones they encounter. It’s important for us to think about what it takes — even the seemingly little things — to make an ecosystem work, especially one as wondrous and important as this one. Because if a rock falls in the Bering Sea, and no one is there to hear it, it’s still someone’s condo.