Boothbay-based Bigelow scientists detect rare signs of climate resilience

The Continuous Plankton Recorder sails across the North Atlantic Ocean. Photo from the Marine Biological Society

The world’s oceans are 95% unmapped and impact us in ways we may not fully understand. New research from the Boothbay-based Bigelow Laboratory confirms just that. According to Dr. Karen Stamieszkin, lead author of the study, mysteries do not begin miles below the surface, but on the surface itself.

A scanning electron microscope image of Michaelsaria elgans, a species of plankton known to be capable of mixotrophy. Colin Fischer photo

A team of Boothbay researchers examined 60 years of data (1958–2015) on microscopic plankton in the North Atlantic Ocean. In a study published in “Frontiers of Marine Science,” researchers provided the first basin-level view of how the distribution of mixotrophs varies, detecting an increase in abundance as the Gulf of Maine warms.

The Continuous Plankton Recorder (CPR) survey is conducted by the Marine Biological Association. Its data turned out to be of great importance for Stamieszkin’s research.

“CPR is a decadal survey designed to sample zooplankton,” Stamieszkin said. “But it also catches large phytoplankton [mixotrophs], and that’s why it worked well for this study. We found that the data was set up to compare mixotrophs and photoautotrophs [diatoms].”

For thousands of years, scientists believed that organisms could survive by photosynthesis or by directly consuming prey. In the twentieth century, they noticed that most marine life does both: mixotrophic organisms change their habits as needed—hence their industry nickname, “flexible feeders.”

Stamieszkin found that mixotrophs are most abundant when it is warm and nutrients are less abundant – conditions expected to become more common due to climate change. She said the study confirms that the ocean is changing at a molecular level, and because mixotrophs are flexible in the way they obtain food, they have resilience to global warming.

The results serve as a starting point for further experiments to investigate the impact of mixotrophy on nutrient cycling and predict how marine life will respond to a changing environment. Or so the team hopes.

Trophic index across the CPR study regions (1996-2015). Red indicates more heterotrophs, gray mixotrophs and blue autotrophs. Photo from the Marine Biological Society

“We didn’t necessarily intend to study climate resilience, but our findings beg the question,” says Stamieszkin. “Another thought is: If mixotrophs are more resilient than their counterparts, will they replace those at the base of the food web? The last sentence of the article states that the study is intended to spark further research, and that is true. Our work presents new hypotheses to advance science.”

Stamieszkin explained that if mixotrophs replaced the base of the planktonic food web, it would impact all ocean life, including local seafood and the endangered whales that Maine is federally required to protect. Furthermore, microbial life in the ocean produces half of the Earth’s oxygen. Massive changes in the plankton community would change how much oxygen is available for humans to breathe.

Bigelow Laboratory is involved in the Gulf of Maine North Atlantic Time Series, a separate project that has been collecting data to monitor changes in the oceans since 1998.

“Time series that cover a long time frame and a large space are rare because they are so expensive to finance,” Stamieszkin said. “But they are crucial to understanding our changing ocean and its countless ecosystems. Marine biotic components, such as phytoplankton, are responsible for the global nutrient cycle; they have a direct impact on human life.”

Barney Balch, a researcher emeritus at Bigelow, helped get the GNATS program off the ground.

“The power of long-term series of environmental measurements is that you get to know and determine the natural variability of your specific system,” says Balch. “Such work is extremely labor intensive – making hundreds of cruises along the same transect over decades – but you gain enormous statistical power to credibly evaluate climate change.”

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