As the world’s oceans continue to absorb increasing amounts of carbon dioxide (CO2) from the atmosphere, researchers are studying how the conditions affect phytoplankton, the species on the lowest level of the marine food chain.
UW oceanography professor James Murray is currently leading a team of several UW students and researchers from Western Washington University (WWU) in conducting novel experiments at the Friday Harbor Lab in the San Juan Islands. The researchers are observing how phytoplankton react to ocean acidification, the ongoing decrease of the ocean’s pH level due to an increase of CO2 in the ocean. They discovered that currently, the ocean already contains high levels of CO2 and continues to absorb more, which makes an increasingly acidic ocean environment. In many regions of the world, ocean acidification has had disastrous effects on ecosystems, such as the death of coral reefs. However, researchers said effects in the Puget Sound marine ecosystem are still unclear, as the team needed further research.
“Phytoplankton is one of the first responders to increases in CO2 because they use an element of CO2 to fix carbon into biomass via photosynthesis,” said Robin Kodner, research scientist at Friday Harbor Labs and an assistant professor of biology at WWU, in an interview with Crosscut.com. “That sets off a whole cascade in the microbial food web.”
The lab remains one of the only places in the United States to use experimental techniques such as mesocosms, experimental water enclosures designed with conditions that closely mirror those in nature. The mesocosms allow researchers to realistically manipulate environmental factors and observe the effect on organisms.
“With small-scale experiments, it’s hard to look at the entire food web,” Murray said. “When we do a large-scale experiment like this, we can include large volumes of water to hold all the core components of the ecosystem in the ocean.”
By mimicking different oceanic environments in the mesocosms, the team could oversee what happens to phytoplankton under varying levels of acidity and better understand the larger-scale effects of acidification on the entire ecosystem. Researchers also observed the responses of other components of the food web.
The team built large plastic domes filled with nearly 3,000 liters of natural ocean water. In the early stages of the experiment, Murray and his team lowered nine domes underwater. Six had high levels of CO2 and three were constant control variables. The control domes contain water with Friday Harbor’s current acidity levels, while the other six contain seawater twice as acidic.
“We can control the amount of carbon dioxide in the water and look at how [phytoplankton] are responding to changing environmental conditions,” said Michael O’Donnell, a research associate at the Friday Harbor Lab.
To control the mesocosm environments even further, mesh was placed over the domes, therefore reducing light exposure by 50 percent. The light reduction allows researchers to slow the photosynthetic process and the biological production of phytoplankton.
However, the researchers worried that too much light was being cut off and could not drive enough phytoplankton growth. To better mimic an oceanic environment, Murray and his team took off the light inhibitors and simply lowered the mesocosms into deeper water.
So far, the researchers have not noticed substantial effects. They suspect that since ocean water in Friday Harbor already contains high levels of CO2, phytoplankton must have already adapted to high levels. Further research is needed to discover the effects of CO2 on the smallest member of the ocean food chain.
“In a coastal region like Puget Sound, it won’t be as damaging as most people have assumed,” Murray said. “There is a lot of speculation and concern that it will really damage the ecosystems, and it really might in the open ocean.”
Reach reporter Karina Mazhukhina at science(at)dailyuw.com. Twitter: @karina9m
Karina Mazhukhina, The Daily, University of Washington, 16 July 2013. Article.