In kelp forests, scientists seek climate change refuge for herring roe
Aerial surveys of Sitka Sound showed a lot of active herring spawn this week, stretching over 31 nautical miles to date. But that wasn’t the only place to find roe. In the basement of the Sitka Sound Science Center researchers are incubating thousands of herring eggs to determine the effects of warming ocean temperatures and ocean acidification on the species — now and in the future.
As I descend into the basement of the Sitka Sound Science Center, down the narrow concrete staircase, I find a scene akin to something in a horror movie or an episode of Goosebumps: An eerie blue light and a loud humming noise emanating from behind a green tarp curtain -- but Lauren Bell, a researcher working on her Ph.D. through UC Santa Cruz, is reassuring.
“Behind this glowing green tarp is a pretty cool experiment that we’ve just started,” Bell said. “We’re trying to simulate future conditions of Sitka Sound and rear herring roe from fertilization to hatch to see how they do.”
Bell pushes the tarp aside and we squeeze into the makeshift room. On the floor are rows of small white tubs, glowing bright from UV light.
“What you’re looking at is a single layer of herring roe, herring eggs lined up along these blades of kelp,” she says. “They are basically held in these conditions and we’re going to hold them here until they hatch, and see if their health is affected in any way. If their hatch rate, their fertilization success, their length, their size is affected at all by these changing ocean conditions.”
Each incubator holds about 300 herring roe, about 7,000 in the 24 trays, so Bell and her research partner, assistant UAS professor Angie Bowers, didn’t need to collect more than a handful of herring to conduct the research. Just one fish lays around 20,000 eggs.
Researchers know that the ocean is warming, absorbing excess CO2 in the environment, and becoming more acidic through a process called ocean acidification. Bell is trying to replicate those warmer conditions in Sitka Sound, 100 years from now.
“What that means is a projected increase in water temperature by about 4 degrees Celsius,” Bell says. “And an increase in the CO2, the carbon dioxide content of the water. So more ocean acidification, the pH is actually going to be lower.”
Researchers also hypothesize that kelp forests and seagrass beds can help offset that acidification process by absorbing CO2 through photosynthesis, creating refuge zones by raising the pH, making the environment less acidic. Now, Bell and Bowers are trying to figure out just how much kelp could help species like pacific herring, in warming conditions.
“Algae might respond in some way to climate change. Fish might respond in another way. Does the habitat these herring roe grow up in actually afford them some protection from future conditions?” Bell said.
Bell is comparing fertilized roe on kelp and roe on clear silicone baking sheets, which are similar in texture to the kelp but don’t photosynthesize. They look at the eggs under a microscope every day to see what changes they can observe, but one thing is certain.
“At our higher temperature treatments they’re going to mature quicker,” she said. “In our low temperature treatments which are simulating today, they’ll probably take another 15-16 days to hatch.”
She says that in many ways, this project is unique.
“Quite a few [studies] have looked at temperature effects, but not very many that have looked at the temperature and carbon dioxide, ocean acidification effects combined.”
And Bell says, though they’re looking into the impact of temperatures 100 years from now, there could be some implications for the fishery today.
“One the temperature data, knowing our waters are warming up is going to change timing for everything, for spawn timing, for development,” she says.
“Really we don’t yet know what ocean acidification is going to do to these guys at any stage of their life,” she says. “If we can start to get a picture of if they’re more vulnerable than we think, or less vulnerable than we think, that will hopefully influence what protections we want to give them, how we manage them.”
Right now, she’s just a few days into the project, so it’s too early to tell if the kelp effectively protects the roe from the high temperatures and low pH. She’ll need about three weeks for all of the eggs to hatch- around the same time their relatives in Sitka Sound will be hatching in the wild.