“The first time you bring up a net, everybody’s like, ‘What is that? That’s so weird!’” says Amy Maas, an assistant professor in the School of Ocean Futures and an ASU BIOS faculty member, who has been on research cruises with Niimi.
“It looks like a busy city, but in three dimensions, or like a galaxy spinning around. You’ve got all these different shaped things — and none are shaped like us; they’ve got too many legs or no legs at all — and they’re zooming around in this bucket,” Maas says.
On his first research cruise, in July 2021, Niimi remembers Maas and Leocadio Blanco-Bercial — another ASU BIOS researcher and assistant professor in the School of Ocean Futures — easily identifying the different zooplankton.
But he was confused: Was that thing zooming around in the net a krill or a shrimp? The two can look similar, but krill, zooplankton also called euphausiids, have exposed gills, though you need a microscope to see that. Eventually, after multiple research trips and nights spent studying in the ship’s lab, Niimi became adept at identifying krill and pteropods.
“I can just look at it with my naked eye and say, ‘That’s this genus,’ or ‘That’s this species,’” he says.
What were once just “specks of dust” were now distinct creatures — each playing an essential role in the ocean’s overall health.
The importance of plankton
Zooplankton are tiny organisms that range from a fraction of a millimeter to centimeters in length and take a variety of shapes. Krill look like tiny shrimp; copepod can resemble insects, with a pair of antenna atop their teardrop-shaped bodies; and pteropods, planktonic marine snail, are called “sea butterflies” because their foot resembles two wings. Then there’s phytoplankton, the microscopic algae that zooplankton feed on and which photosynthesize in the top layers of the ocean.
Though they might be small, the role plankton play is enormous.
“Zooplankton are the most abundant animals on Earth, by far, and they are sustaining all the trophic webs in the oceans,” Blanco-Bercial says.
They’re also the first step in the biological carbon pump, the crucial ocean system that sequesters carbon out of the atmosphere and stores it in the deep ocean.
“We need to know the crucial roles of these different zooplankton so that we know, as the ocean is changing, how the biological carbon pump may be changing.”
— Susanne Neuer, founding director of the School of Ocean Futures
The pump works like this: First, phytoplankton capture carbon dioxide through photosynthesis.
“Think of the equivalent of grass on land. That’s what phytoplankton are in the ocean,” says Susanne Neuer, founding director of the School of Ocean Futures and a professor in ocean biogeochemistry and one of Niimi’s advisors.
Then, the phytoplankton die and begin to sink, or they get eaten by zooplankton, which excrete fecal pellets containing organic carbon that sink even deeper. Those zooplankton die or get eaten by bigger predators themselves — and sink. As the organic carbon sinks and sinks, it gets stored for longer and longer. It can stay sequestered for up to 1,000 years if it reaches the deep ocean.
A "sea elephant" heteropod under the microscope, and displayed with an iPhone mount.
What Niimi, Neuer and others are trying to figure out is what zooplankton are out there, where they are going, how much they’re excreting and how much carbon or other nutrients are in all those sinking particles. After they collect the zooplankton, one experiment involves putting them in beakers and seeing just how many fecal pellets they produce and what’s in them. Understanding their vital roles in the carbon cycle is part of a puzzle.
The oceans take up about a quarter to a third of all our emissions through this carbon pump. Without it, we would have already surpassed the 1.5 degree Celsius target from the Paris climate agreement, Neuer says.
“The ocean is buying us time,” Neuer says. And that time is thanks to plankton.
But while the ocean helps stem climate change, it’s being affected by it. The researchers are studying the biological carbon pump because the seas are changing, already getting warmer and more acidic.
“We need to know the crucial roles of these different zooplankton so that we know, as the ocean is changing, how the biological carbon pump may be changing,” Neuer says, who is the principal investigator in the project.
Partnering for the oceans
Neuer started working with scientists at ASU BIOS about 15 years ago. ASU BIOS itself has been doing oceanography work for 120 years. U.S. scientists first visited it in 1903, and it has run long-term studies for years — like its Bermuda Atlantic Time-series Study, which has collected data on the ocean’s physical, biological and chemical properties through cruises out to sea every month since 1988. As Neuer and Niimi have done, other researchers can access that trove of historical data and piggyback onto those cruises for their work.
“That saves a lot of time, money and headaches, to know that those data exist,” Blanco-Bercial says, “and then you can focus on the question you want to answer.”
In 2021, ASU and BIOS joined forces, turning the Bermuda institution into a center for the Julie Ann Wrigley Global Futures Laboratory, alongside ASU’s Center for Global Discovery and Conservation Science in Hawaii.
“The merger between BIOS and ASU opens up ocean sciences for ASU students,” Neuer says, including opportunities for field experience and the chance to work with the faculty in Bermuda.