Mermaid’s wineglass algae (center, bottom) near the study site. (Credit: Emily Carrington)
Worldwide, coastal ecosystems are full of calcified algae species. These stitch together in networks that provide valuable habitats and resources to fish and other marine life. But with a future of more acidic oceans predicted to come, are some of the species at risk?
Scientists at the University of Washington recently completed a study into the effects of ocean acidification on one delicate alga, the mermaid’s wineglass. It lives on shallow seafloors and is commonly found in waters off Vulcano, an island located near the northeast coast of Sicily.
In those waters, Jason Hall-Spencer, a researcher from Plymouth University, had found that members of the species living nearer to volcanic vents releasing carbon dioxide appeared different when compared to those living farther away. And so, during a visit to U. Washington’s Friday Harbor Labs for a seminar presentation, he asked if anyone there would be interested in finding out why.
“He had brought in a suitcase with two vials of mermaid’s wineglass. One was in carbon dioxide-rich water and the other was not,” said Emily Carrington, a professor of biology at U. Washington. “So I offered the study to Laura Newcomb, a 2nd-year graduate student in my lab.”
Newcomb began conducting studies of the alga using Friday Harbor Labs, but there were concerns that preservatives that had been used in storing Hall-Spencer’s samples could change the results. With that in mind, researchers decided it was necessary to go to Italy to collect measurements with fresh samples.
And so they traveled to Vulcano to directly gather data around vents spewing CO2 above an active volcano. These were segmented into three different zones so that researchers could look at the effects of high, medium and low levels on the mermaid’s wineglass.
“They are small, delicate plants, so she (Newcomb) snorkeled and collected them with usually a putty knife, but they don’t cut so well,” said Carrington. “They were collected in vials that she brought up to the surface.”
Newcomb, as well as Marco Milazzo of the University of Palermo, also used bottles to gather discrete water samples around the different vent zones to gauge the relationship of their carbon dioxide releases with the health of mermaid’s wineglass plants living near them. All of the samples were processed in a lab in Palermo.
These revealed a few interesting things, says Carrington.
“First of all, we found that the plant does live in the high CO2 conditions. It’s not obliterated and it can live there. It’s an example of a plant that can,” said Carrington. “Of course, if it moves closer to the vent, it can’t live. There’s a gradient of how harsh it can tolerate. But it can survive in areas where some snails and grazers cannot.”
The scientists also looked at how calcified the algae were because their stalks’ stiffness are important for raising their petals high enough off the substrate to propagate. In the high carbon dioxide areas, they found that the mermaid’s wineglass plants had less calcium carbonate.
But they also went a little further, Carrington says, zeroing in on how the conditions affected the plants’ ability to thrive.
“What does calcium carbonate do to the plant’s performance? I like to point out that we (humans) have calcium carbonate in our bones. And so we could lose a little density and be fine, but it will reach a point where it’s too much,” said Carrington. “So we took one part and did a cantilever beam test and it showed that less-calcified stalks were not as stiff, but more importantly that it was not linear. Losing 10 percent of calcification is like you’re doing 30 percent worse. It’s a steep loss and that’s the most important lesson we learned from this pretty little alga.”
So losing just a little bit of calcium carbonate pushes mermaid wineglass plants past a tipping point where they can’t maintain the structural stiffness they need to be able to reproduce. But this non-linear finding wasn’t all that surprising to Carrington, as there are many examples in biology where such relationships reveal themselves. In fact, she says it is more the rule than the exception.
The find is a good example of how researchers could approach data sets differently, in a somewhat more open-minded way.
“Often, scientists assume there will be standard, linear responses. And a lot of the models assume it too,” said Carrington. “But sometimes drawing a line through a data set is not the best pass and it makes more sense to draw a curve.”
Full results of the work are published in the scientific journal Biology Letters. Funding was provided by the National Science Foundation and the Mediterranean Sea Acidification program.
Top image: Mermaid’s wineglass algae (center, bottom) near the study site. (Credit: Emily Carrington)