UNH researchers and regional partners are working to determine the cause of an unusually large brown algal bloom in the Gulf of Maine and monitor its effects on marine life.
Phytoplankton Monitoring in Gulf of Maine as a Signal of Climate Change Impacts
UNH research tracks the role of microscopic algae in sustaining marine biodiversity and ecosystems
Monday, December 16, 2024
Unlocking the Ocean’s Calcium Mystery
Coccolithophores, a type of phytoplankton that produce calcium carbonate plates around their cells, are among the most significant contributors to calcification in the ocean and play a crucial role in the global carbon cycle. These single-celled organisms not only drive carbon sequestration but also form blooms on the ocean’s surface that are so vast they can be seen from space. Yet, scientists have long puzzled over a discrepancy: much of the calcium carbonate these organisms produce never reaches the deep ocean as expected.
Harvey joined scientists from the Woods Hole Oceanographic Institution to study this piece of the puzzle. Their work identifies microzooplankton—microscopic predators of phytoplankton—as major players in dissolving coccolithophore calcium carbonate. Inside tiny digestive compartments, these predators break down and dissolve these calcium plates with strong acidity.
“It’s like eating a big Tums tablet,” Harvey said, “except here the acidity isn’t neutralized—it breaks down the calcium carbonate entirely.” The findings show how this biological mechanism can explain up to 100 percent of the calcium carbonate loss observed in the ocean's upper layers.
The implications of this work extend beyond the ocean’s chemistry to its ecosystems and even global food security. Since many marine species depend on healthy phytoplankton populations, disruptions to these foundational organisms could have cascading effects on the food web. As Harvey put it, “Understanding how microzooplankton shape these dynamics is essential for maintaining the delicate balance of marine ecosystems in a warming world.”
Read the paper Microzooplankton grazing on the coccolithophore Emiliania huxleyi and its role in the global calcium carbonate cycle , published in the ScienceAdvances.
This work was supported by the National Sciences Foundation.
Phytoplankton, the ocean’s microscopic plant powerhouses, form the base of the marine food web, supporting life from tiny zooplankton to mighty marine mammals. These small but vital organisms play a crucial role in maintaining marine ecosystems and regulating the planet’s climate by sequestering carbon in the oceans. Researchers at the University of New Hampshire are working to understand when, how, and why phytoplankton dynamics change, which could be essential for predicting environmental changes and marine ecosystems’ health.
“All the larger organisms that we enjoy eating or observing rely on phytoplankton,” explained Elizabeth (Liz) Harvey, associate professor of biological sciences at the UNH College of Life Sciences and Agriculture. “We can think of them as the marine version of the canary in the coal mine – if we start seeing significant changes in phytoplankton populations, it could directly affect the rest of the marine organisms present.”
Harvey studies marine microbes, including phytoplankton, and their fundamental ecological relationships. These microbes engage in predator-prey and parasitic interactions, similar to those of larger organisms. Her research focuses on how these interactions occur among phytoplankton, how they influence species abundance and diversity, and how these dynamics may shift in response to climate change.
To better monitor these dynamics, Harvey and her team conduct weekly sampling at three coastal sites along the New Hampshire coast and monthly sampling at offshore locations in the Gulf of Maine. In the lab, they use a specialized instrument called a FlowCam to visualize and measure the various species of phytoplankton present. Given that phytoplankton populations can change rapidly, this tool provides weekly updates on species composition, helping the research team detect short-term shifts in the ecosystem.
Better understanding phytoplankton populations and their interactions can aid with developing strategies to mitigate the effects of climate change on marine biodiversity in the Gulf of Maine, said Harvey. And with the Gulf of Maine being one of the fastest-warming bodies of water globally, it serves as a critical area for observing climate change impacts.
“In the Gulf of Maine, we’re particularly concerned about changes in the amount of phytoplankton present, the species present, and when during each year they are most abundant,” said Harvey.
“Phytoplankton dynamics directly influence the marine food web, and major shifts could have cascading effects on species such as zooplankton, fish, and marine mammals,” Harvey added. “These changes could significantly impact fisheries and aquaculture, which makes it crucial for us to develop strategies that help mitigate the effects of climate change on marine biodiversity.”
In the summer of 2023, Harvey and a team of other UNH scientists documented an unprecedented bloom of brown microalgae, Tripos muelleri. These blooms can impact marine life by altering oxygen levels and nutrient availability, thus affecting the Gulf’s biodiversity.
“It’s completely normal to see this species in the Gulf waters, but never at this intensity,” said Harvey. “We are interested to know if this indicates the beginning of a longer-term shift in species composition of phytoplankton in the Gulf of Maine, or whether this was a more random event.”
She added, “To answer this, we’re continuing to monitor the Gulf’s phytoplankton through weekly and monthly coastal and offshore sampling to track any changes in how these microscopic organisms are changing and what that could mean for the bigger picture.”
To learn more about Harvey’s research, visit the UNH Phyto Lab website. Are you an undergraduate student interested in joining the Phyto Lab? Learn more online!
This material is supported by.... the National Marine Fisheries Service, Grant/Award Numbers: NA21NMF4570525, NA18NMF4570255; the UNH School of Marine Science and Ocean Engineering; Aramco Services Company; the Curtis and Edith Munson Foundation; Office of Under Secretary for Science and Innovation.
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Written By:
Nicholas Gosling '06 | COLSA/NH Agricultural Experiment Station | nicholas.gosling@unh.edu
