How scientists are attracted to the bottom and what questions they have for molluscs

It happens that scientists are tempted to explore the seabed. Maybe they need to drill it, or build something there, or they just want to know everything about the bottom. Out of a pure thirst for truth.

They immediately have a problem: the seabed is large, and the scientists are small and it is difficult for them to cover the whole bottom at once. You need to somehow contrive and study it so as not to put your whole life on the bottom soil.

And scientists came up with the idea of first asking the mollusks. Clams know a hell of a lot about the seabed because they’ve been living there for a long time. And along with the mollusks, various sea spiders, stars, plankton and other invertebrates live there – so as not to list everyone every time, scientists call them “bottom communities”.

If something happens at the bottom, the bottom communities immediately find out about it, fuss, run, and then discuss with their neighbors for another six months, trying to somehow survive the stress. By the way, they react very sensitively, but they run rather slowly, which also plays into the hands of scientists.

If we take, say, the Barents Sea or the Kara Sea, where they always strive to drill or build something, then there are under four thousand species of tiny invertebrate animals. Ask, I don’t want to.

Well, scientists ask. They lean over the side and hang in wavering shadows over some collection of mollusks. To begin with, they dump the trawl, unceremoniously rake a piece of the bottom community into it, lift it onto the ship and see who is there, which means they live on the bottom of the ocean.

Then they begin to act thinner, but not more delicate. They do not take a whole trawl, but a small scoop, with which they more or less carefully bite off a chunk from the bottom. The ladle with which scientists eagerly scoop soil from the bottom is called … a bottom grab.

“Hrum!” – a bottom grab gnaws into the ground. Ay, ssss…!” – the starfish hisses, whose paw has been pinched by a ladle, and the wretched one crawls to the side. The bucket soars back.

Here, scientists are already looking not just at who is approximately there, but how many and what kind of mollusks are sitting in the bucket, and from which starfish this foreskin was plucked off. Everything does not look very attractive: scientists put their greedy fingers into a piece of cold mud from the bottom, poking around in it, rinsing with water, shamelessly tugging and squeezing the stunned clams. They lay out all the washed mollusks in jars, begin to count, weigh and call them by name.

The bottom grab is emptied into a basin, so that later they can get into this vile briquette with scientific hands

And six months later, the same thing happened again. And then more. And further. To study the bottom, if you want to do something with it, you need to start in advance, four years before the first intervention. Otherwise, something at the bottom can be irretrievably damaged, and then the state will punish you. You probably know that our state is terribly concerned about the polychaete worm, and for the nudibranch mollusk, in general, it can tear out the Adam’s apple. And put all those involved on the bathyscaphe from the propeller side.

In addition to catching shellfish and grabbing them with greedy hands, there are other ways to study benthic communities. You can send a diver to them with a Leica and a notebook. But unlike a bottom grab, a diver constantly requires money and oxygen, and even if it is launched too deep, it can depressurize and burst there, frightening bottom communities and spoiling all science for us. So they take care of the divers, they try to immerse them less often and closer to the shore.

More benthic communities can be seen, oddly enough, from a satellite. But also only near the coast, in good weather and clear water.

Then the data on the counted and touched mollusks are compared. If from year to year the total weight of mollusks and the number of their species in the bucket does not change, then everything is okay. If the number of species has decreased, but they themselves have become heavier, then the mollusks are on the mass and eat something that was not previously brought into their bottom community. For example, some delicious organic waste. And if, for example, out of fifty species in the bucket, three are left, and even those have a mine cough and black circles under their eyes, then things are bad.

But this does not solve the main problem. We can count shellfish at specific points as much as we want and get detailed information, but the vast seabed will not decrease from this. What to do?

Here scientists effectively snap their fingers at the audience and say that they will now apply areal geophysical surveys, and then combine them with the study of bottom communities! After that, they hear a puzzled silence in response, sigh heavily and begin to explain in a human way.

You can study a large piece of the bottom at once if you have a ship, a bottom profiler, a multibeam echo sounder, a side-scan sonar, hot tea in a thermos and a lot of free time.

Attached to the bottom of the ship, a multi-beam echo sounder screams acoustically towards the bottom and builds a high-precision relief map. He shouts like a fan, because he is multi-beam.

*This is how a multibeam echo sounder works*

Behind the ship, a bottom profiler is dragged on a rope and screams into the bottom with low-frequency “Bird! bird-y! The acoustic signal not only flies to the ground, but also burrows into it forty to sixty centimeters. And only then it digs back and returns to the surface, where it gets into a seismic streamer. A seismic streamer is a kind of reflected signal catcher, which is also dragged behind the ship on a rope behind the profiler. So scientists learn the structure of bottom sediments in depth – where is the sand, and where is the stone, where is the career brief, that is, ugh, the barrier reef.

*Long yellow hair is a seismic streamer. And short yellow sausages closer to the ship are the source of the signal*

The side-scan sonar also trails behind the ship on a rope, but unlike the profilograph, it crawls near the very bottom. He cunningly looks sideways parallel to the bottom and makes a projection. He can see when something lies at the bottom: stones, corals, the lost frigate of Her Majesty or the previous side-scan sonar.

*This is how side-scan sonar can see a plane lying on the bottom*

All of these can be attached to the ship at the same time. The ship is moving, and the scientists on it are literally filled with scientific data and the delight of the discoverers.

Believe me, this is not difficult for a research ship. In addition to echo sounders, he has a bunch of other things hanging on winches above the water: a plankton net, a Rosetta probe with a battery of bottles in which he can collect water samples from different depths. A hollow soil tube, which can be thrown into the bottom under its own weight and it will stick, then close it from below and get a neat layered bottom column to the surface.

*Scientists throw a soil tube, and then they measure who has the soil column longer*

Sometimes there is even a remote-controlled underwater vehicle – when it is launched, scientists immediately begin to swear. They take away the control panel from each other and everyone shouts that it is he who can swim closer and more imperceptibly than the others to the bottom community and catch him completely by surprise.

*A research vessel has winches sticking out from everywhere, and the more winches, the more it can scientifically explore and the less scientists are tired of carrying equipment on their own hump*

Then, when the ship temporarily surfed, scientists trembling with anticipation take geophysics data, the results of interviews with mollusks – and combine them. They say: “Here at this depth, on sandy soil with small pebbles, in such and such a temperature of water, such mollusks live. And the sea spider Lawrence. And the polychaete worm Georges. Now and forever, we, scientists, assume that in other areas with the same depth, water temperature and bottom structure, the same mollusks, sea spiders and George’s half-brother, the worm Andryukha, will live.

*A map that is obtained after geophysical surveys. It can be overlaid with sampling data from benthic communities*

If there is not enough data, and scientists always do not have enough, they continue to study.

The ship with the scientists barrages back and forth, trying not to spray the solarium much, echo sounders scream at the bottom, the sonar squints to the sides, counted mollusks are densely packed in jars, and all this lasts until it becomes clear where you can do something without a big drill damage. Or build something at the bottom – most often, then to drill something in this place too.

And, of course, just to slightly satisfy the generally insatiable craving of scientists for the secrets of the seabed.