Algae In The Pacific Are Losing Their Skeletons Because Of Ocean Acidification, Global Climate Change
After finding a reversal of competitive dominance among species of algae in the temperate coastal waters of the northeast Pacific Ocean, researchers believe that global climate change is the direct cause of increased ocean acidification which in turn has altered marine biodiversity.
A recent study, published in in the journal Ecology Letters, outlines the competitive dynamics among crustose coralline algae that grow skeletons made of calcium carbonate, living in the waters around Tatoosh Island, Washington. Crustose coralline algae and shellfish find it difficult to produce skeletons and shells when the ocean becomes more acidic due to absorption of carbon dioxide from the atmosphere. This is also an indicator of the impacts of ocean acidification on marine life.
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Scientists have been compiling a rich record of ecological data from Tatoosh Island, located off the northwestern tip of Washington State for a long time. In the 1980s, University of Washington biologist Robert Paine had conducted experiments here. Sophie McCoy, a PhD candidate at the University of Chicago and Dr. Cathy Pfister, professor of ecology and evolution at the school, repeated the same experiment with four species of crustose coralline algae to study their competitive behavior in today's ocean.
They chose coralline algae for the study because of an interesting fact: "On one hand, they can grow faster because of increased carbon dioxide in the water, but on the other hand, ocean acidification makes it harder for them to deposit the skeleton. It's an important tradeoff," said McCoy, lead author of the study, in a press release.
In previous experiments, a single species, Pseudolithophyllum muricatum, was clearly the winner over the three others almost every time. But in the most recent experiment, the same species won only 25 percent of the time. McCoy referred to it as a "rock, paper, scissors dynamics," where it was pretty much a crapshoot which species would come out on top.
The dominance of P. muricatum in the past, according to McCoy, was due to its comparatively thicker skeleton. In the 1980s, its skeleton was twice as thick as its competitors, according to the historical data. Today, its skeleton is roughly equal to those of the other species — in other words it has lost its competitive advantage. Organisms like P. muricatum that need to make more calcium are under increased stress with increased ocean acidification, and according to the most recent data, the water around Tatoosh has dropped pH significantly in the past 12 years.
This study is particularly important, according to McCoy, because it has been conducted in a natural context like Tatoosh Island instead of in the laboratory. "Field sites like Tatoosh are unique because we have a lot of historical ecological data going back decades. I think it's really important to use that in nature to understand what's going on," she said in a press release.
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