At least in some eelgrass beds, oxygen levels were dramatically higher during summer daylight hours when photosynthesis was humming along. Over longer periods, however, no general patterns emerged to show how eelgrass might be influencing water chemistry.
Nevertheless, experiments with oysters planted both inside and outside of eelgrass beds seemed to show very real benefits from the vegetation. The experiments, which included commercially valuable Pacific oysters as well as native Olympia oysters, examined many factors, from biochemical makeup of the oysters to their shell structure.
“Really broadly speaking, for Olympia oysters we have seen a general pattern of enhanced growth inside of eelgrass,” Horwith said. “This is not a minor thing. Typically we have seen in 2016 and ’17 a boost of about 30 percent in the growth rate of oysters inside of seagrass.”
In 2018, using a somewhat different approach, the researchers found no difference in growth inside and outside of eelgrass beds. But this year, using even more experimental sites, Olympia oysters within eelgrass beds are showing a clear pattern of more rapid growth.
Limited work with Pacific oysters has so far shown a pattern consistent with Olympia oysters. On the other hand, similar experiments with Manila clams showed unexplained reduced growth. For geoduck clams, no significant difference has been seen so far.
“This, to me, illustrates the importance of working species by species,” Horwith said. “Even in the same functional group, there can be big differences in the way they interact with water chemistry.”
Environmental DNA
While many researchers are studying how individual species respond to ocean acidification, one group from the UW’s School of Marine and Environmental Affairs is using DNA to ask a different question.
“We go out into the world and ask ‘What’s there?’” says ecologist Ryan Kelly, whose work with other researchers involves a search for DNA that has been shed by organisms into the surrounding environment. This approach is referred to as environmental DNA research, or eDNA for short.
“Every living thing has DNA and is leaving that DNA in the environment,” Kelly said, explaining the concept at the symposium. “Whether you are a many-celled porpoise or a single-celled dinoflagellate, you have DNA, and so we can go and collect that.”
Simply put, researchers filter samples of water and run genetic tests to see which species have left their DNA behind. The results provide a good idea of what is living in a given area — and what is not.
In eDNA studies in Hood Canal and the San Juan Islands, more than 400 different kinds of plankton were found throughout the year. An analysis led by Ramòn Gallego in Kelly’s lab helped to reveal which plankton — including harmful species — showed up under various water conditions and where they were likely to appear at different times of the year.
An alternative approach in studying eDNA is to focus on a single species to see how the concentration of DNA differs from place to place or over time in one location. Conditions may dictate whether one place is more hospitable to a species than another or whether the species might do better in summer or winter.
Kelly showed his audience an animated map of Puget Sound, which changed to reveal monthly variations in the relative populations of Alexandrium, a toxic species of plankton responsible for paralytic shellfish poison, which can be deadly to humans. During August 2017, high levels of DNA from Alexandrium suggested that a plankton bloom was underway in southern Hood Canal near Hoodsport.
In another study in Kelly’s lab, Kelly Cribari discovered quantities of DNA related to a group of plankton called Kareniaceae, which has been identified by other researchers as new potentially toxic alga. While nearly absent in waters with normal acidity, eDNA of this species has been found repeatedly in areas with lower pH. These new findings suggest that these plankton could become a growing problem in Puget Sound as ocean acidification intensifies.
Predicting future damage
Extensive monitoring of Puget Sound waters provides a fairly up-to-date picture of water conditions, such as temperature, dissolved oxygen, acidity and so on. But these numbers alone don’t describe the potential for damage that occurs to marine life when water quality gets out of whack.
Now, thanks to a team of scientists focused on biological effects, red flags can be raised to signal serious problems for certain organisms when water-quality measurements reach dangerous thresholds. The team is led by Nina Bednaršek, senior scientist at the Southern California Coastal Water Research Project, who presented the latest threshold findings during the ocean acidification symposium.
Bednaršek and colleagues used pteropods, a group of sea snails, to identify dangerous thresholds. These tiny animals are an important food source for many marine species, and they have been studied extensively for their sensitivity to ocean acidification. Specifically, their shells, which are made of calcium carbonate, do not grow properly in waters with low carbonate ion concentrations — so water chemistry becomes a life-or-death matter.
Besides a low concentration of carbonate ion, the time of exposure in corrosive waters can affect the severity of damage. Both ion concentration and the duration of exposure are used to estimate thresholds beyond which pteropod growth and survival will be impaired. For example, pteropod eggs may fail to develop in water low in carbonate ion — even when the exposure is for just two days. On the other hand, pteropod adults are likely to survive longer in the same water, perhaps because their shells are already complete. Studies have identified threshold levels for mild and severe shell dissolution, as well as other negative biological responses.
Published thresholds — which include bothe the magnitude and duration of stressful conditions — have been derived through a consensus of a dozen or more experts familiar with ocean acidification effects on specific species. Besides pteropods, thresholds have been developed — but not yet reported — for echinoderms, such as sea stars and sea urchins. Thresholds for Dungeness crabs are under development.
When combined with real-time temperature and chemical data gathered from monitoring buoys and other sources, one can get an understanding of the type of damage taking place over time. Bednaršek said conditions in Puget Sound often reach harmful levels for all stages of pteropods, especially in Hood Canal, South Sound and Whidbey Basin.
One can also combine predictive models with biological thresholds to anticipate problems for specific species. For example, the Salish Sea Model, under development by the Washington Department of Ecology, is designed to predict water chemistry based on a number of factors — including the amount of nutrients from natural and human sources coming into Puget Sound.
Based on that modeling, excess nutrients — such as nitrogen from sewage-treatment plants — may contribute to water conditions that can cause thresholds to be exceeded for pteropods and larval Dungeness crabs in parts of Puget Sound.
Thresholds for Dungeness crabs and other commercial species could be used in the future to help estimate economic losses from ocean acidification, whether caused by nutrient loading or atmospheric deposition.
A different kind of predictive model discussed at the symposium, called LiveOcean, is designed to produce daily forecasts of underwater conditions likely to occur over the coming three days. Similar to a weather forecast, the model uses up-to-date information on currents and other physical and chemical properties to predict changes in water conditions in the Salish Sea and along the coast.
LiveOcean can predict when and where pH will dip to dangerous levels, the potential course of toxic algal blooms, and likely pathways for incursions of aquatic invasive species, such as European green crabs, according to UW oceanographer Parker MacCready, who led the effort to develop the model.
One of its most important applications — and the initial motivation for building the model — is to help shellfish growers avoid harmful waters when planting oyster seed and operating oyster hatcheries, MacCready explained.
Oceanographer Samantha Siedlecki reported on an analysis that looked out to the year 2100, showing that many ocean conditions along the West Coast are likely to become more severe — more harmful to sea life — than predicted by global models.
The analysis, which involved numerous collaborators, considered how local factors — such as coastal currents, upwelling and biological activity — tend to “amplify” projections developed at a global scale, said Siedlecki, a former UW research scientist now based at the University of Connecticut.
While the new analysis showed a rate of acidification fairly consistent with global models, levels of temperature and carbon dioxide are projected to be adversely higher in the year 2100 — much higher in some areas. Likewise, beneficial oxygen and carbonate ion concentrations are predicted to be lower than global projections would suggest, and the amount of time that dangerous low-oxygen levels are present could double by 2100 in several coastal areas.
Moderator Jan Newton, a UW oceanographer, said it was important to recognize the capabilities of experts in this region who are developing “really sophisticated hydrodynamic models” to calculate future ocean conditions.
“I really want to acknowledge the groundbreaking work that is going on here, and thank you all,” she said.
State policies and communication
Ocean acidification can be a daunting problem for scientists, politicians and the public, but Washington state has consistently stepped up to the challenge, according to Jennifer Hennessey, senior policy adviser to Gov. Jay Inslee.
In 2012, she said, Washington was the first state to address the problem of ocean acidification with the release of a comprehensive plan containing six broad strategies:
- Reduce carbon emissions, such as from power generation and transportation, while improving energy efficiency,
- Reduce land-based contributions to ocean acidification, such as from sewage systems, agriculture and development,
- Increase adaptation to change, such as by restoring shoreline habitats, recycling seaweed for upland uses and propagating native species to maintain biodiversity,
- Invest in science to enhance understanding and reveal new approaches to the problem,
- Inform and engage stakeholders, leaders and the public, and
- Maintain a sustainable focus on ocean acidification through policy and science coordination.
“Washington’s strategy catalyzed ingenuity across the state and partnerships up and down the West Coast,” Hennessey said during the symposium. “The state has invested millions in ocean acidification work. We’ve leveraged federal resources that are here — we are very lucky to have them here — and we have attracted private financing, too.”
Progress has been made on all six of those fronts, as identified in a 2017 update by the Marine Resources Advisory Council, she said. And this year the state took a big step forward when the Legislature doubled the state’s investment in ocean acidification — including money for a variety of scientific studies. Lawmakers also approved a package of governor-proposed initiatives, including mandates requiring only renewable energy supplies by 2045 along with new building-efficiency standards.
“Our action plan is held up as an example of how to move from a problem to action,” Hennessey said, adding that Washington is collaborating with other states, including Oregon and California. Those states were represented at the symposium by Steve Weisberg of the Southern California Coastal Water Research Project and Charlotte Whitefield of the Oregon Coordinating Council on Ocean Acidification and Hypoxia. Both Weisberg and Whitefield said their states are working from action plans similar to Washington’s.
“We are elevating this issue through various forums, including the launch of the International Alliance to Combat Ocean Acidification,” Hennessey said.
She noted that the organization has grown to more than 80 members —including 10 states and provinces, 12 nations, seven tribes and four cities, plus dozens of businesses and nonprofit groups along with educational and research institutions.
“Our partnerships are playing an important role, but we need to do more,” Hennessey said. “We need to expand the breadth and depth of those partnerships, and we need to get beyond the usual circle of people in this room.
“We need to connect with people first. Why should they care? We need to make it relevant to the audience … and we need to identify actions,” she continued. “Without this connection, people are left wondering what they should do and feeling somewhat helpless with those curves (on graphs) that Dick (Feely) started us off with early in the day.”
Moderator Jan Newton said she thought she heard gasps in the room when Feely outlined the frightening path forward, as ocean acidification picks up its pace because of changes in ocean chemistry.
“We are understanding so much more and becoming more knowledgeable about this issue,” Newton said. “Not only are we are dedicated to our science, we also have a huge responsibility to society. Fruitful collaborations across agencies and institutions are essential to addressing this problem, as is clear communication to the public.”
Communication with the public, she concluded, is being planned to outline the problem in some detail and gain momentum for a different path to the future.