Foundational Food Sources In The Gulf Of Maine Are Failing
This article is part of The State of Science, a series featuring science stories from public radio stations across the United States. This story, by Murray Carpenter, was originally published by Maine Public Radio.
At the Bigelow Laboratory for Ocean Sciences, researchers Barney Balch and Catherine Mitchell are looking at a map affixed to a large table.
“We’re looking at a chart of the Gulf of Maine, and right across the middle there’s a line that’s drawn from Portland, in Maine, to Yarmouth, in Nova Scotia,” Mitchell says.
That line is the route along which Bigelow researchers have been taking regular measurements for the last 25 years. They’ve analyzed chemical and temperature data that help describe how the waters of the gulf are changing. One tool they use is a six-foot long cylinder with wings.
“This is an autonomous underwater vehicle, or a glider,” Mitchell says. “So it’s a big robot that moves up and down in a yoyo-like pattern, from the top of the ocean to the bottom of the ocean right across the middle of the Gulf of Maine. So it’s measuring a bunch of science things as it goes. It looks a bit like a big yellow torpedo. It’s got some wings on it.”
A century ago, the oceanographer Henry Bigelow described the blooms of phytoplankton in the Gulf of Maine. Now, research from the East Boothbay lab that bears his name finds that phytoplankton in dramatic decline, and that could have a significant impact on the entire food web of the gulf.
Balch says the research involves NASA satellites first launched in the late 1970s that work in tandem with scientists gathering data out on the water. Balch’s colleagues had begun taking samples from a commercial ferry that operated along the same stretch. But then he had a bigger idea.
“It would be wonderful to actually put a full bona fide laboratory on the back of a flatbed truck that we could drive onto the ferry and take measurements from that,” he says.
NASA funded the lab on a truck, which took its first ferry ride in 1998. Since then, the lab has taken measurements on more than 200 trips across the gulf, all in sync with the NASA satellites. Using data collected by the satellites, the ferry, research vessels and the glider, Balch says the Bigelow time-series has demonstrated that phytoplankton productivity declined about 65% between 2001 and 2018.
“The part that is the most disconcerting is these are the microscopic plants that you can’t see with the naked eye,” he says, “yet they are at the bottom of the marine food web on which all life in the sea depends.”
Balch says there are many factors at work that may affect phytoplankton in the Gulf of Maine. For starters, air and water temperatures are warming. And there’s more intense rainfall, which can wash tea-colored water into the gulf, blocking sunlight, and also stratifying the water like unmixed salad dressing. That prevents nutrients from welling up to the surface, where they can fertilize the phytoplankton.
“These plants are no different than any other plants, they need two things, they need light, and nutrients to flourish,” Balch says. “And if you stratify that ocean, if you cap it off with this low-density water, it makes it harder for them to get the nutrients they need.”
On top of all this, Balch says, the Labrador Current, which used to bring cold water south to the Gulf of Maine, is now changing direction and moving more to the east.
To get a closer look at what’s at stake, we walk down to the dock, where a loon is quietly fishing, and the water is deep enough that Henry Bigelow could have pulled his research schooner alongside.
Even on a gray winter day, the water has a deep, rich, blue-green hue. And Mitchell and Balch say there’s a lot going on under there.
“It’s a mix of all these different things,” Mitchell says. “There’s the phytoplankton in there, there’s sediments in there, there’s the dissolved humic tea-like material from the land, the forests and the trees and the grass are in there, and they’re all mixed in together to give that overall color that we’re seeing.”
“There’s information in that color about what different types of plants are there,” Balch says, “and that’s our job is to try to decipher that.”
Balch says the combination of warming temperatures and declining phytoplankton suggest that the gulf’s productivity won’t rebound in the immediate future. But he hopes he’s wrong about that.
This story is part of Maine Public Radio’s series “Climate Driven: A deep dive into Maine’s response, one county at a time.”
Murray Carpenter is a climate reporter at Maine Public, based in Portland, Maine.
KATHLEEN DAVIS: And now it’s time to check in on the state of science. For WWNO. St Louis Public Radio. Iowa Public Radio News. Local science stories of national significance.
The gulf of Maine is a complex aquatic ecosystem it stretches from the coast of Massachusetts up to new Brunswick and Nova Scotia. It’s home to everything from lobsters and scallops to whales. Like many aquatic ecosystems, the gulf of Maine is changing. New research shows the teeny tiny phytoplankton in the gulf of Maine are in decline. So what could this mean for the gulf’s food web? Joining me to talk about it is my guest Murray Carpenter, climate reporter for Maine Public based in Portland, Maine. Welcome to Science Friday.
MURRAY CARPENTER: Hi. Thanks for having me on.
KATHLEEN DAVIS: So explain to me why phytoplankton are just so important in the gulf of Maine.
MURRAY CARPENTER: Phytoplankton, like plants on land, they absorb carbon dioxide and use photosynthesis to grow. And then these little phytoplankton in turn feed everything from zooplankton to clams and fish. And so everything in the gulf of Maine depends on them. From lobsters to right whales to bluefin tuna. Some oceanographers even like to say all fish are diatoms. And Barney Balch of the Bigelow Laboratory for Ocean Science in East Boothbay, Maine put it in simple terms.
BARNEY BALCH: The part that is the most disconcerting is these are the microscopic plants that you can’t see with the naked eye. Yet they are the bottom of the marine food web on which all life in the sea depends.
KATHLEEN DAVIS: So phytoplankton, as that clip said, they are kind of this building block that the rest of the food web is built atop of. But they are very, very, very small. So how do researchers actually measure how robust this population is?
MURRAY CARPENTER: They’ve been pretty creative about this. The Bigelow Lab is a nonprofit that’s on the coast of Maine. And they’ve been doing research on the gulf of Maine for a long time. They’re named after the pioneering oceanographer Henry Bigelow. The Bigelow researchers noticed that a ferry between Portland Maine and Yarmouth, Nova Scotia was crossing the gulf of Maine regularly at a very strategic location.
So they began taking water samples from the ferry. Then they went one step further and they built a bona fide sampling lab that they could actually mount on a flatbed truck. And they would just drive this truck right onto the ferry and use it as a mobile sampling lab.
KATHLEEN DAVIS: So they kind of created this on the go laboratory.
MURRAY CARPENTER: Yeah, that’s exactly what it is. But the ferry service hasn’t been continuous. Some years it doesn’t operate at all. So sometimes they’ve used private research vessels along the same transect taking samples. And sometimes they use autonomous glider. It’s basically a sampling robot. It’s six feet long, bright yellow. And it looks like a torpedo with wings. And they just send that across to get samples in the gulf of Maine when the ferry is not running.
And all together with the robot and the ferry and the private research trips, they’ve done hundreds of trips over 25 years and they’ve gathered this data together in what they call the gulf of Maine north Atlantic time series. And there’s yet another variable here. They sync these trips up with NASA satellites that take photos of the water as they pass overhead. So this allows them to correlate their observations on the water with the colors observed from the satellite. And Bigelow researcher Catherine Mitchell told me the color of the water reveals more than you might think.
CATHERINE MITCHELL: It’s a mix of all these different things. There’s the phytoplankton in there. There’s sediments in there. There’s this dissolved humic tea-like materials from the land, the forest, and the trees, and the grass that are in there and they’re all mixed in together to give it that overall color that we’re seeing.
KATHLEEN DAVIS: So 25 years of a lot of data. How have these scientists seen the ecosystem change over that period of time?
MURRAY CARPENTER: One huge change is that the phytoplankton populations have declined dramatically. Balch and Mitchell published a paper last year and it showed that phytoplankton in the gulf of Maine declined 65% between 2001 and 2018.
KATHLEEN DAVIS: Wow. I mean, is this because of the usual culprit, climate change? Or is there something else going on here?
MURRAY CARPENTER: Yeah, climate is playing a huge role. But the researchers were clear that it’s really complicated. For starters, the gulf of Maine is warming really fast. Research from the Gulf of Maine Research Institute shows the water’s now nearly four degrees Fahrenheit warmer than it was as recently as between 2001 and 2018.
KATHLEEN DAVIS: Wow.
MURRAY CARPENTER: They say it’s warming faster than 99% of the world’s oceans. And on top of that, heavier precipitation some years is sending more freshwater into the gulf. And that does two things. One, the water’s a bit murkier and this actually blocks the sunlight from the phytoplankton. But the other thing it does is it’s stratified the water. I mean, Blach put it to me like it’s like unmixed salad dressing.
So you have the less dense, fresher water on top and the denser, saltier water beneath. And this prevents the kind of mixing that would allow the nutrients to come up from the bottom and reach the phytoplankton towards the top. So there’s a lot going on there.
KATHLEEN DAVIS: So a lot of changes happening in the gulf of Maine. What could the future look like?
MURRAY CARPENTER: Well, the researchers were very careful to not really predict exactly what it might look like. But they do say the trends are pretty ominous, in a way. Because the warming trend is predicted to continue. And with the warming, we’re seeing these declines in phytoplankton. But as Barney Balch told me, he really hopes he’s wrong about this.
KATHLEEN DAVIS: That’s all the time that we have for now. I would like to thank my guest, Murray Carpenter, climate reporter for Maine Public based in Portland, Maine. Thank you so much for joining us.
MURRAY CARPENTER: Thank you, Kathleen.