Can Plankton Survive Warming Seas?

Have you ever tried to turn the lights on only to learn the switch was connected to something else entirely? The same can be true for the environment where flipping on or off one switch (e.g. changing atmospheric chemistry) can turn others on or off as well (e.g. changing surface temperatures).

“If we increase carbon dioxide a lot, we’re turning on a switch, and if we turn on that switch our planet might turn on or off some other switches,” said Basia Marcks, a Ph.D. candidate at the University of Rhode Island’s Graduate School of Oceanography, speaking at the Bay Informed Discussion Series. “We don’t know exactly what switches those are, what they’ll do, and what the consequences are.”

We’re introducing a whole new pool of CO2 that the Earth is not used to being released in that abrupt [amount] of time.

Marcks and Jacob Strock, a master’s student at GSO, discussed the drivers of climate change, what changes can be expected over the next few decades, and how phytoplankton —tiny marine plants — are important for regulating climate.

The Earth is equipped with natural sources that produce CO2 and sinks that remove CO2, which are usually naturally balanced over time in what’s known as a “carbon budget.” For instance, rocks changed by heat and pressure can release carbon, as can volcanic eruptions. Carbon from weathering rocks and decaying marine life can travel to ocean basins to be stored for millions of years.

What is different today is time.

“We’re introducing a whole new pool of CO2 that the Earth is not used to [having] released in that abrupt of a time,” she said, referring to a graph showing the rapid increase in the amount of CO2 that has been released into the atmosphere since the 1950s. She explained that this is largely due to burning fossil fuels. “We’re going into the rock record and extracting some of that carbon that was stable and now making it unstable, active, and [directing] it right into the atmosphere.”

Phytoplankton may be a way forward in mitigating this excess of carbon in the atmosphere and understanding potential future conditions. Although they store significantly less carbon than other reservoirs such as fossil fuels, these microscopic plants are the link between the sky and sea that could help regulate carbon on a much faster timescale than some of the other modes.

They use the oxygen from the CO2 dissolved in the oceans to photosynthesize and produce sugars, and they use the remaining carbon to build their shells. When they die, their carbon-laden shells sink to the bottom and are deposited into the ocean floor, where the carbon will be stored for millions of years. This process happens in a matter of days to weeks. Plankton, said Marcks, represent a huge transport mechanism of carbon and may be one of the ways the planet will try to rebalance the carbon budget.

Phytoplankton are important because they generate roughly half of all organic matter on the planet and produce half the world’s oxygen.
Smithsonian Environmental Research Center

“On average, the ocean is greater than 2 miles deep, and a lot of this water hasn’t interacted with the atmosphere for hundreds to 1,000 years,” added Strock, who is studying plankton populations and dynamics. “Having these biological intermediaries that can take material from the surface to the deep has a lot of potential to affect our climate.”

But for plankton to counter this excess carbon, they need to have the numbers.

“There’s a delicate balance between growth and loss,” he said. “Plankton exhibit exponential growth. The equation is the same as compound interest; small changes in the interest rate over time have a big impact.”

But not all species of plankton grow at the same rate or respond the same to changes in temperature or nutrient availability. Nobody, he said, has really looked at how any of these species will acclimate to rapid changes in the system, specifically temperature.

“The biology isn’t going to jump instantaneously from one equilibrium to another. You never plop a goldfish from the store directly into the tank. You leave it tied up in the bag and put it in the tank to let it adjust because it takes some time for that to happen. It’s the same for plankton,” Strock explained. “These organisms aren’t probably doing their optimum or what they would if they were given enough time to adjust.”

Strock is working with researchers at GSO to begin looking at how different plankton species will manage this temperature shift. This includes shifts in predation and food availability linked to temperature changes.

“We know temperature is an important determinant to growth and abundance, but we haven’t studied acclimation yet. We’re going after it with models and going into the labs, and will hopefully come out with some predictive capacity,” he said. “The ocean is a huge, dynamic system and we’re currently dealing with enormous changes. The mean annual surface temperature of the [Narragansett Bay] is increasing, so we’re seeing the effects of climate change locally. And here in Rhode Island, we care about the aquaculture, about the fisheries, the recreational abilities, and tourism of this region.”

Understanding how plankton reacts to a new temperature regime is not only critical for climate research but also has huge implications for local fisheries and uses of our marine resources. Plankton, said Strock, essentially provide an invaluable service that could never be replaced.

The entire presentation may be viewed at the Bay Informed Discussion Series Facebook page: https://www.facebook.com/bayinformed/.

– Meredith Haas | Rhode Island Sea Grant

 

The Bay Informed Discussion Series is sponsored by Rhode Island Sea Grant in partnership with GSO. This series is held every third Thursday of the month at 7 p.m. at the URI Graduate School of Oceanography Bay campus in Narragansett. These events are designed for the community to get involved and learn more about research at GSO.

For more information, visithttp://web.uri.edu/chowder-marching/bay-informed/, on Facebook@bayinformed, or contact gsobayinformed@gmail.com.

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