While working on board a research vessel positioned 240 miles offshore Ireland in the Atlantic, BIOS zooplankton ecologist Amy Maas announced this month the publication of three new papers in science research journals. Maas, who has spent May at sea with 26 other scientists for the multi-year EXPORTS project (EXport Processes in the Ocean from Remote Sensing), used Instagram to promote the just-released science publications.
The EXPORTS project, which helped to fund several research projects featured in the papers, combines satellite observations and robots with direct measurements in the ocean to understand and predict the carbon cycle. Specifically, scientists are working to understand how carbon makes it to the dimly-lit “twilight zone” and deeper ocean interior. They want to know how long it stays there, which is vital to understanding present and future ocean ecosystems and global climate.
Maas’ ongoing role with the project since 2017 has been to collect, measure, and better understand zooplankton and their waste products. The small, sometimes microscopic organisms, which help to form the base of the marine food web, play a critical role in removing carbon dioxide from the atmosphere that is part of the ocean’s carbon cycle.
Zooplankton Excrement: ‘It’s Actually Really Important’
Just like other marine animals, zooplankton poop. As these fecal pellets sink, they do two things: provide food for other marine life and move carbon from the surface water to the deep ocean, where it is prevented from mixing back up with the atmosphere. “In this way, the pellets remove some of the extra carbon that humans produce out of the atmosphere,” Maas said. “That’s good news for us, as this means that carbon can’t contribute to global warming.”
Maas said the study was the brainchild of science colleague Karen Stamieskin at Virginia Institute of Marine Science (VIMS) and involved “convincing a bunch of zooplankton to poop in special chambers that separated them from their fecal pellets.” Stamieskin, the lead author on the paper with Maas and scientist Deborah Steinberg (also at VIMS), then counted them and measured the carbon for different species, and also whole communities, based on five different size groupings.
Maas noted that “even though these smallest critters don’t make up a huge part of the biomass, their poops are super important.”
Paper featured in Limnology and Oceanography. Fecal pellet production by mesozooplankton in the subarctic Northeast Pacific Ocean. 2021.
Comparing Results in the Atlantic and Pacific
The Atlantic and Pacific Oceans differ, from their sizes to their saltiness to the organisms that live in each. Even the amount of carbon sent to depth by migrating zooplankton is different; in the North Pacific, researchers know that it is low, and Maas’ recent paper sought to determine exactly how low.
The North Atlantic, particularly during the spring phytoplankton bloom, offers a different story for comparison. Like on land, spring in the North Atlantic means growth. Using energy from sunlight, phytoplankton draw in nutrients, carbon dioxide, and water from their surroundings to reproduce. In the process, they emit life-giving oxygen and provide food for a host of larger marine organisms, from snails to whales.
“We are doing the same experiments out here in the North Atlantic right now that we did in the North Pacific because we are in the middle of the spring bloom when lots of carbon gets sent to depth,” she said. “It is our high-export site for comparison.”
The long-term goal is to look at both regions and try to improve the global models that use satellite data and larger models that predict climate and climate change. The work in the Pacific, supported by EXPORTS, is the result of research performed in 2018 with more than 150 individual zooplankton collected from the North Pacific.
Paper featured in the Journal of Plankton Research. Allometry and the calculation of zooplankton metabolism in the subarctic Northeast Pacific Ocean. 2021.
Helping to Make A Big Job Become More Efficient
Scientists who collect and study zooplankton from research vessels sometimes use of a large net known as the MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System). As the name implies, researchers controlling the net can trigger it to open and close as desired to gather samples of small organisms at different ocean depths. This allows them to determine and compare what organisms live at each depth.
For research published in this paper, Maas and BIOS colleagues, including zooplankton ecologist Leocadio Blanco-Bercial, used samples collected from offshore Bermuda in the Sargasso Sea. They then ran the samples through a waterproof, high-resolution scanner in their BIOS laboratory, called a zooSCAN, to quickly make digital images of huge numbers of zooplankton samples.
One purpose of the research was to compare the effectiveness of this research tool (taking pictures of the individual animals to get their actual sizes using the zooSCAN) to an old way of estimating (weighing the animals all together and guessing at their average sizes). Scientists measuring zooplankton collected during the month-long EXPORTS project will use the newer methods described in the paper.
“With that information we can start to look at how size changes in different ecosystems, and calculate the movement of organisms and their waste products from surface to depth as they migrate over the course of the day,” Maas said. The information provides additional insights into the role that zooplankton and their movement (as well as the movement of their carbon- and nitrogen-carrying waste) play in global warming.
Paper featured in the Journal of Plankton Research. Use of optical imaging datasets to assess biogeochemical contributions of the mesozooplankton. 2021.