HARI SREENIVASAN: Now a new effort to shed light on a mystery that has long baffled scientists who study the world’s oceans and waterways.
Researchers are using some very sophisticated robots to understand what’s happening with microscopic marine life.
Special correspondent Cat Wise has the story, part of our weekly series covering the Leading Edge of science and technology.
CAT WISE: At the Crab Cove Visitors Center in Alameda, California, the main attraction is, no surprise, crabs.
WOMAN: It’s pointed, right? So that means it’s a…
CAT WISE: On a recent afternoon, a group of children on a field trip at the center headed outside to the nearby beach with naturalist Morgan Dill for a talk on the creatures of the cove.
MORGAN DILL, Naturalist, East Bay Regional Park District: We have got clams. We have got oysters. Would you like to see a crab’s baby picture? This is the cute little baby crab. So, this is their larval stage, and they go through this stage and they’re out there, but we don’t actually know too much about them, but this is their baby picture.
CAT WISE: Dill’s lesson highlighted a gap in her and other scientists’ otherwise detailed knowledge of the crab’s life cycle.
MORGAN DILL: Sometimes, when you flip them over, they have actually got eggs on their abdomen. And they’re holding them there, and there’s hundreds of eggs. And, so, often, the kids will say, OK, so where do they go from there?
We tell them they go back out into the bay, but we don’t really know how long they’re out there, when they’re coming back, and are they at the whim of the current or not?
CAT WISE: The answers to those questions have long been a mystery to those who study the oceans. But it’s not just the whereabouts of baby crabs that’s perplexing. More than 70 percent of all marine organisms start out life as tiny microscopic larvae, creatures like sea urchins, anemones, lobsters, shrimp, and a wide variety of fish. Many look like little aliens.
STEVEN MORGAN, University of California, Davis: We know so little about this life stage because it’s so incredibly difficult to study.
CAT WISE: Steven Morgan is a professor marine ecology at the University of California at Davis. Morgan has spent most of his career trying to figure out what happens to marine larvae before they become adults and are easier to track.
STEVEN MORGAN: On land, we can radio track mountain lions by putting collars on them and their offspring, and so we know exactly what’s happening to populations. But in the sea, imagine trying to follow this microscopic larval stage for weeks and months in the plankton while it’s developing. We can’t do that.
CAT WISE: The conventional wisdom in his field, says Morgan, has been that the larvae float passively in the big turbulent ocean, and it’s sheer luck if they are able to stay near shore or at certain depths that they prefer.
STEVEN MORGAN: People tend to think of them as larvae being carried by currents, much like a dandelion seed on the wind, and they have little control over where they’re going.
CAT WISE: But Morgan never bought into that theory, and in recent years, he and a small number of other scientists around the country have done tests in labs that show the larvae can in fact control their movements more than previously thought. It turns out that they are pretty good at swimming up and down in the water column.
STEVEN MORGAN: Did you see a difference in the swimming patterns between the species?
CAT WISE: But what do those up and down movements mean for them when they are in the ocean? Are they showing us they do have some control over their fate?
To figure that out, Morgan has enlisted the help of some cute, but very sophisticated robots. For the past two years, Morgan and his colleagues have been deploying swarms of these devices, affectionately called larvae bots, off the coast of Northern California. They are programmed to mimic the larvaes’ up and down behaviors as the float freely in the water.
Their buoyancy is controlled by an internal bladder filled with oil. And they are packed full of instruments, sensors and a GPS tracking system. The goal of this research, which is funded by the National Science Foundation, also a “NewsHour” funder, is to find out where the larvae bots are going and how they manage to get there.
STEVEN MORGAN: This is a new information that hasn’t — hadn’t really existed up until now. So, we’re sort of cracking the black box of larval behavior.
CAT WISE: In fact, data coming back from the larvae bots shows that they stay remarkably close to shore when programmed to go up and down at certain times of day. And that’s what Morgan thinks many of the larvae are doing too. They seem to know how to use currents and tides to go generally where they want.
STEVEN MORGAN: The one way that they can actually have some control over where they’re going and their destinies is actually to move vertically between currents that are stratified, moving in opposite directions.
So, if they can simply just regulate their amount of time in surface and bottom currents, then that will determine how far offshore and along shore they’re actually going.
CAT WISE: The concept of larvae-mimicking robots actually came about more than 20 years ago from two now retired professors at North Carolina State University, Tom and Donna Wolcott.
Steven Morgan met them and at a conference , and a partnership ensued. The robots are assembled back in North Carolina, and then shipped to the U.C. Davis Marine Lab in Bodega Bay, where principal marine electronics technician Grant Susner gets them ready to go to sea.
GRANT SUSNER, University of California, Davis: These robots are made by — their external housing is a fire extinguisher. We repurposed and recycled some old ones that they had around.
CAT WISE: Fire extinguisher.
GRANT SUSNER: Yes.
CAT WISE: Wow.
And you may have noticed, they aren’t exactly the same size as microscopic larvae. But Susner says it doesn’t actually make much of a difference.
GRANT SUSNER: The key feature of this robot is that we have programmed it, its behavior, to mimic the speed at which the larvae travel as well. So, this isn’t going to travel any faster than larvae does.
CAT WISE: While the robots seem to be revealing clues about the larvaes’ behavior, the question remains, why does it actually matter if, in fact, the larvae are better navigators?
I posed that question to a man who would really like to know where they are going.
BILL DOUROS, NOAA Office of National Marine Sanctuaries: Knowing that information is a big deal. There’d be a lot of benefits to us from a science standpoint, as well as from a management standpoint.
CAT WISE: Bill Douros is the West Coast regional director for NOAA’s Office of National Marine Sanctuaries. Douros says it’s difficult to manage and protect diverse populations of marine life without knowing where the youngsters are.
BILL DOUROS: The state of California and federal fishery managers have made decisions about where to place no-fishing areas along the coast of California. Many of these are inside national marine sanctuaries. And the scientists that advise on that make their best educated advice.
But they don’t know precisely how big the marine protected areas should be. If we knew better where the larvae go after they’re released, we might better design and may shrink even some no-fishing areas and no-take areas that are set up to protect abalone and crabs and other parts of the ecosystem.
CAT WISE: He also says that larval movements can impact much larger species.
BILL DOUROS: The larvae, which are part of this plankton food chain, ultimately predict where whales are going to be. If we knew where the whales were going to be in the next three days, we might reroute ship traffic to separate whales from ships, so that they don’t get struck by ships.
CAT WISE: For his part, Steven Morgan knows that his research and conclusions might still be a tough sell for many of his fellow marine scientists.
STEVEN MORGAN: I’m hoping that these robots, where we’re actually doing experiments in the ocean, will convince some of the skeptics and get more people, more investigators in marine science to think that way, because it’s a hugely important question.
CAT WISE: Back at Crab Cove, naturalist Morgan Dill and a group of curious kids are hoping they soon can get some answers for their important questions.
For the “PBS NewsHour,” I’m Cat Wise in California.
HARI SREENIVASAN: Cat’s report is also part of our Breakthroughs coverage of invention and innovation.
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