Monitoring the Gulf of Maine

The Gulf of Maine is an incredibly useful body of water to study when it comes to exploring the effects of climate change, says Eugen Cotei ’21. “That’s because the waters of the Gulf have warmed faster than 99 percent of the ocean.”

Cotei has been working as a research fellow this summer helping Associate Professor of Earth and Oceanographic Science Michèle LaVigne analyze the conditions in this rapidly warming corner of the Atlantic Ocean. “My goal over the summer has been to validate data collected by the pier sensor at the Coastal Studies Center,” he explained.

“The sensor measures variables like pH, carbon dioxide levels, and dissolved oxygen concentrations in the seawater, all of which are incredibly important in understanding how the dynamic system operates, especially in the context of our changing climate and coastal acidification.” Based at the Schiller Coastal Studies Center less than thirteen miles from campus, Cotei has been collecting water samples from Harpswell Sound at regular intervals during low and high tide. These samples are analyzed and compared with the sensor data, and in theory should be able to validate those data.

“Once the sensor is validated, sensor results (which have been recorded continuously for about two years now) can be used to understand and characterize changes in the sound’s chemistry,” explains Cotei, who will be following up these findings during his senior year. “For my honors thesis, I will be considering how these results change seasonally and compare them with proxy data from long-lived organisms that reveal past oceanographic conditions in the Gulf of Maine. This project will therefore give us clues about any significant changes in the variability of coastal seawater chemistry over the past few hundred years. It’s really exciting stuff!

The Impact on Marine Life

At least two other seniors will also be working at the Schiller Center this fall studying the impact of the warming oceans on different types of marine life.

Hannah Randazzo is looking at how warmer conditions will affect the ability of the sea star (known by some as the starfish although it’s not a fish!) to grow new limbs. “For my senior honors thesis, I am examining the ways in which climate stress, namely ocean acidification and ocean warming, will affect sea star arm regeneration in the near future,” she said.

“Ocean acidification is affecting the pH of the ocean through a series of chemical reactions that ultimately results in a decrease of free carbonate ions,” added Randazzo. “Since sea stars form their endoskeletons from calcium carbonate,” she explained, “a decrease in carbonate ion availability will affect the ability of sea stars to construct their endoskeletons.” Conversely, however, ocean warming also increases metabolic efficiency, so it also has the potential to improve sea star regeneration as well as damage it.

“Since these two processes will be occurring at the same time, they may be having opposing effects. Therefore, my research project will examine their combined effects on a keystone intertidal species, yielding results that could have implications for the entire intertidal community structure,” said Randazzo.

Sophie Walton, meanwhile, is looking at how the invasive green crab is affecting the blue mussel population in the Gulf of Maine. “Blue mussels are a critical species native to Maine, but their numbers have declined over 60 percent in the last forty years,” she said. “This decline is likely due to a combination of climate change and overfishing, but green crab predation in recent years has added to the problem.” Green shore crabs, or Carcinus maenas, are not new to Maine, but warmer ocean temperatures have caused their numbers to explode, with dire consequences for the populations of shellfish they consume, including blue mussels.

For her honors thesis this year, Walton is paying particular attention to the indirect effects of green crab predation on the species. “When in the presence of green crabs,” she explained, “blue mussels thicken their shells to make it harder for the crab to break into their shells.” This successfully lowers the chances of a green crab predation, she said, but also means the mussels have less energy for other things, like reproduction.

“In a species that is already declining, lowered reproductive output could have really significant implications. So, I am looking into the energy allocation in blue mussels in the presence and absence of green crabs. Blue mussels are struggling on a several fronts, responding to warming waters being one of them, and my project looks at another reason their populations may be struggling that would interact with the effects of climate change to make the problem worse,” said Walton.

Bowdoin, 26 August 2020. Article.

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