The sea butterfly effect: distorted oceans could shatter ecosystems
Kelsey Gobroski / Sun Star Reporter
March 22, 2011
When you catch a fever, a few degrees can be the difference between life and death. The oceans are the same way: a few more hydrogen ions and a slightly higher temperature can have catastrophic consequences. UAF is waking up to the reality of changing oceans alongside the rest of the world, resulting in local research and guest lecturers. German oceanographer Silke Lischka talked about her ocean research at Ny-Ålesund, Svalbard (an arctic archipelago), in the Vera Alexander Learning Center on March 11.
Lischka works at the Leibniz Institute of Marine Sciences in Kiel, Germany. She traveled to Svalbard to study the impacts of global ocean changes on the sea butterfly, a type of shelled plankton in the pteropod group. The Arctic will be among the first areas to feel the effects of a phenomenon called ocean acidification, which led to the recent establishment of the Ocean Acidification Research Center on West Ridge at UAF.
“It’s a busy time in the Arctic, I would say,” said Bodil Bluhm of the School of Fisheries and Ocean Sciences (SFOS).
Ocean acidification doesn’t mean the ocean becomes acidic, but gets less basic, or alkaline, on a 0 to 14 pH scale. Battery acid has a low pH. Bleach, a basic substance, has a higher pH. Normally seawater hovers around a pH of 8.2, but dropped to 8.1 since the Industrial Revolution, according to the European Project on Ocean Acidification. This might not seem like much, but pH is logarithmic. That decrease leads to a 26 percent increase in hydrogen ions floating around.
Oceans suck up carbon dioxide from the atmosphere. The carbon dioxide reacts with seawater in two ways: making oceans drop in pH and locking carbonate used in pteropod, or sea butterfly, shells.
Although Lischka regularly looks at copepods, tiny shrimp-shaped plankton, her boss needed someone for a pteropod project in Svalbard in 2009. Lischka, who based her doctoral research there, took the opportunity.
Svalbard is a Norwegian archipelago east of Greenland. The international research settlement Ny-Ålesund is embedded on a fjord on the warmer western coast of Svalbard. Lischka and her colleagues caught specimens of the sea butterfly Limacina helicina, plopped them in seawater of different temperatures and pH levels, and watched what happened after 29 days, she said.
Sea butterflies look like tiny black dots in a glass of seawater, Lischka said. These snail-like plankton flutter up the water column with two wing-like feet, their coordination a little uneven under the weight of a cumbersome calcium carbonate snail shell.
These dots are food to fish, which in turn are eaten by birds, sea lions, and orcas. Lischka studies whether sea butterflies, and thus the oceans’ food chains, are in danger in this rapidly changing world. This study makes pteropods the poster children for ocean acidification, much as the plight of the polar bear displays the effects of sea ice retreat.
The oceans are also warming, and Lischka compared the effects of changing temperatures with changing pH. Lischka studied how much pteropod shells grew and how much their shells dissolved. She found carbon dioxide had more of an effect than temperature on pockmarking the shells with holes, but rising temperatures raised death rates.
Although ocean acidification is observable, and pH changes affect sea butterflies, it’s hard to know the end result of a changing ocean on pteropods. Russell Hopcroft, of SFOS, studies plankton communities. He worked with Global Ocean Ecosystem Dynamics (GLOBEC), which studied the possible effects of climate change on marine ecosystems.
To study effects, you need to know where you started. This is called a baseline, and scientists are still working on one for pteropods and a lot of other ocean dynamics. GLOBEC worked on finding a baseline, as will UAF graduate student Ayla Doubleday. Doubleday will culture and study pteropods and larvaceans, another type of plankton.
Lischka’s results were based in experimentation. Even if the oceans become the same pH as the experiments, the change won’t be immediate.
Think of an animal that migrated to Alaska from farther south, such as beavers, Hopcroft said. Over time, they adjusted to the cold, but if you took a southern beaver and let it loose at the northern extent of beaver territory, it would have trouble acclimating. Lischka’s studies are a worst-case scenario — a world where pteropods can’t adjust in the time it takes for oceans to change.
“We know the potential of what ocean acidification might do, but it’s very hard to disentangle what it’s actually doing,” Hopcroft said.
Next, Lischka plans to look at how ocean acidification might affect pteropods’ abilities to last through the winter. They need extra energy to survive the cold temperatures, but there isn’t much information on how much energy they need or how susceptible they are to changes.
“I think as they are probably most vulnerable to ocean acidification during winter we should know how they overwinter,” Lischka said. There is a new species of sea butterfly migrating to Svalbard with the warmer waters. Lischka plans to compare how they deal with winters. The newcomer might not have enough fat storage for long winters. This ties into Doubleday’s studies: a focus on the baseline.
Ocean acidification hits the Arctic faster and harder because cold water absorbs more carbon dioxide. UAF’s Ocean Acidification Research Center, founded in the fall of 2010, works toward becoming a resource on Alaska’s changing oceans.
With Hopcroft and Doubleday, UAF is beginning to establish baselines for ocean ecosystems, but the university also closely tracks ocean acidification’s effects through Mathis and his students.
“We know the potential; we don’t know the outcome,” Hopcroft said.
This article was modified on March 22, 2011. We incorrectly stated that pH ranges from 1 to 14. The correct range is 0 to 14. We have made the correction and the Sun Star regrets this error.