Recently, a team of Brazilian and American scientists discovered over 600 miles of coral reef at the mouth of the Amazon River, calling into question the belief these reefs need clear water to thrive. Reporter Andrea Vasquez catches up with the expedition’s lead American scientist Patricia Yager.
Discovering 600 miles of of coral reef
A team of Brazilian and American researchers recently discovered 600 miles of coral reef at the muddy mouth of the Amazon River, calling into question the belief that these reefs need clear water to thrive.
Reporter Andrea Vasquez catches up with the expedition's lead American scientist, Patricia Yager, via Google Hangout.
Patricia Yager, thanks for joining us.
It's nice to be here.
So, you did not set out to find this specifically when you went to the Amazon to do research.
So what did you find and how?
That's a really good point to start with.
So, this is a good illustration of the serendipity of science.
We went to study the Amazon River plume, which is a very large effect on the tropical ocean, and we needed to get to the mouth of the river.
And one of the scientists that came on board that cruise, his name is Rodrigo Moura.
I asked him what he wanted to do on this cruise, knowing that it was so muddy, and he handed me a paper from the 1970s, and it suggested in this paper that you could find reef fish on this part of the continental shelf of Brazil, and I kind of looked at him funny.
It was a hand-drawn map.
It's a very old paper from a kind of obscure journal.
And I looked at it, and I was like, 'Huh. Wow.
That would be really cool.'
[ Both laugh ] So, how do we do this?
And he thought that he could find them using the multibeam, which is a sonar-type instrument that's on the ship.
So he was watching the multibeam the whole time as we sailed over the shelf.
And he thought he saw things that might indicate the reefs were there, so he knew where we might want to go back to.
What do you know? He found them.
The multibeam is really high-resolution, so you can tell when something is just a few meters taller than the rest of the seafloor, and it also tells you if it's harder.
So the multibeam is able to -- Actually, it's the other sonar instrument that can tell how hard the reflection is up off the bottom.
The sound goes into the mud and kind of comes back with less of a firm signal, and in this case, it bounces much harder.
So you can tell kind of the hardness, and you can tell how high up.
And he was able to see little bumps on the seafloor, and that's where we put the dredge in the water.
I mean, we're all hanging over the side, and he's bringing this thing up, and, oh, my gosh.
He brings up this huge collection of very colorful, beautiful animals and dumps it out on the deck and then proceeds to sort through it.
And everybody's just hanging over looking at all of this amazing stuff, and so, we were just really amazed.
This muddy area where the mouth of the Amazon reaches and the fresh water reaches the ocean's salt water -- is that right?
So you get sort of a unique mix and ecosystem?
In most rivers, there's an estuary, right?
So, the river meets the sea, and the tides carry the ocean in and out of this sort of enclosed body.
But the Amazon is so huge.
Even though it's many, many -- 40 miles wide.
I mean, you feel like you're in the middle of the ocean when you're sitting at the mouth of the river, 'cause you can't see either shoreline.
And yet, the water's fresh.
The velocity is so fast -- the discharge is so high that it comes all the way out to the ocean and just hits the ocean like a wall.
And it's only about 30 feet deep right at the mouth.
In fact, it was a little tricky getting the ship in there and not [laughing] grounding the ship.
We had to sail really carefully up sort of a channel during the high tide so we could get to the mouth.
It's less dense, so as the seafloor kind of falls away, it lifts up away from the seafloor and forms about a 30-foot-thick layer of fresher water as it mixes.
So it gets salty quickly.
It doesn't stay zero salinity for a long time.
Maybe 3 or 4 miles away, it's now a little bit salty.
But it's very muddy.
But it's lifted up above the seafloor, so these reefs are actually underneath that layer.
They're not living in the muddy outflow from the river.
They're living 50 meters, or 150 feet, below the surface.
But the trick is that the plume is over the top of it, blocking all the light.
And when you think about reefs, you think about needing light, and this plume is clearly blocking the light.
So, does that mean that you found different types of plant and animal life because of this different environment?
This is the coast of Brazil.
And here's the Amazon River mouth.
And the plume is heading offshore.
It's quite large.
And so you can see in the south, the species are different from the species in the north.
And we found true corals -- reef-building corals -- and other kinds of corals -- the non-reef-building corals -- in the south.
'Cause they need the light.
But they're able to survive some of the year in the dark.
That's what's kind of interesting, is that they're able to tolerate the low-light conditions.
As you go further north, there were no more reef-building corals.
There were lots of reef animals, like brittle stars and sponges.
There was a lot of just beautiful, beautiful, colorful sponges.
They don't need the photosynthesis from the sunlight.
They're just able to feed on -- My hypothesis is that they're feeding on all the food that's coming from the plume.
From here, what are some of the questions that you and other researchers are trying to use this discovery to answer?
Because at this time, we're also seeing other reefs around the world being threatened by warming waters and changes that's making on their ecosystem.
These reefs may serve to tell us something about how marginal reefs are doing on the planet.
Marginal reefs in the sense of that they're not in optimal conditions.
They're living in sub-optimal conditions, so they may be a little bit more resilient, maybe, to some of the conditions.
Because they're so deep, the tendency is to think that they're kind of immune from human impacts, but in fact, they're not.
They're sitting in the same warming water.
I mean, they're in the surface layer, so they're sitting in the same warming water and the hot acidity water that the other reefs around the world are experiencing, so they're not immune from that human impact.
And they're also being fished pretty heavily, it turns out.
There's a large artisanal fishery on the Brazil coast.
They're also still really important for the larger fish.
So lots of reef serve as nursery grounds for fisheries -- large fish.
So they were finding little baby fishes that were juveniles of big open water, blue water fish that, you know, they spend their time growing up in this sort of safe place.
So they're still really important for that.
Well, we can't wait to see what else comes from this accidental discovery.
Patricia Yager, thanks for joining us.