The world’s oceans are rapidly changing in response to human activities. Carbon emissions are causing the warming of oceans, loss of sea ice, and what is now a new hot topic—ocean acidification. About one-third of carbon emitted into the atmosphere is absorbed by ocean water. This ultimately results in increasing acidity and decreasing availability of calcium carbonate, the chemical that many organisms use to build their shells.

These changes pose a potential risk to numerous marine species. Eggs and larvae of most organisms are sensitive to environmental change, and oyster farms in Washington state have already felt the effect of ocean acidification, which has killed larvae in hatcheries.

Ocean acidification can potentially affect species further up the food chain. As a result, consequences may multiply. While some clear threats are evident, a number of unknowns remain.

At SAFS, ocean acidification has come under increasing scrutiny in recent years. For example, in 2011, it was the focus of the Bevan Series on Sustainable Fisheries. To better understand this problem, SAFS researchers, including Carolyn Friedman (CF),André Punt (AP), and graduate student Emma Hodgson (EH, Tim Essington, advising professor), are focusing on ocean acidification from different perspectives.

MD: How might ocean acidification impact different species and their ecosystems?

CF: We are examining the influence of ocean acidification on the life history and transgenerational effects of key local species such as the Pacific oyster and two native Species of Concern: the pinto abalone and Olympia oyster.

EH: We are addressing how the California Current ecosystem may change in response to ocean acidification. I am using a risk framework to better understand which key ecological or fishery species might be most susceptible to ocean acidification.

AP: Dusanka Poljak (MS, 2013) developed population models for red king crab in Bristol Bay, and I am extending these models to other crab stocks in the Bering Sea.

MD: What have you learned so far?

CF: The bacterial pathogen Vibrio tubiashii has caused losses in local bivalve hatcheries for the last eight years. It first re-emerged in association with upwelling off the Oregon coast and low pH waters. Elene Dorfmeier (MS student) found that this bacterium’s ability to cause disease in larval oysters did not change with pH, but its growth was enhanced by declining pH due to increased CO2.

We observed increased mortality and reduced growth in all species we examined. Pinto abalone and Pacific oyster larvae survival was most affected when the parents matured under current conditions but the larvae experienced an ocean acidification event. On the other hand, Olympia oyster larvae held under constant, very high CO2conditions showed no visible ill effects, suggesting greater resilience than other tested species. Even so, under ocean acidification conditions, fewer larvae were released, and those releases were delayed.

EH: When risk analyses are conducted for a species, they often consider only one life history stage, such as adults. In our work, we are looking at each life history stage (eggs, larvae, juveniles, and adults) separately. This can help us to get a better idea of how risk might change for a species over the course of its life. For example, adult Dungeness crab are at lower risk than their eggs.

AP: Ocean acidification may profoundly impact the North Pacific crab fishery. The high mortality rates for juvenile red king crab associated with ocean acidification mean that harvests may decrease, with potentially enormous economic consequences. However, those impacts won’t be evident for at least 20 years, so we have time to plan.

MD: Your projects are interdisciplinary. Can you explain?

CF: We are investigating host susceptibility to disease and parasite responses to changing ocean pH and carbonate chemistry in collaboration with Assistant Professor Steven Roberts and partnering with Joth Davis (SAFS affiliate Associate Professor) and Emily Carrington (Biology Professor, Friday Harbor Marine Labs).

EH: Much of the research on ocean acidification focuses on the direct response of potentially sensitive species, but does not make the link to how this might affect the whole ecosystem. Tim and I are working with partners at the NOAA Northwest Fishery Science Center to use an ecosystem model to investigate what changes might occur throughout the food web as different organisms respond to ocean acidification. Ultimately, we plan to bring this to the port level and hence to fishing communities.

AP: We are exploring the impact of ocean acidification all the way from the larval stage to fishery impacts. This involves collaboration with ecologists and economists at NOAA.

MD: What will you focus on next?

CF: Our data suggest that some shellfish species appear to be in peril as a result of ocean acidification. Tested shellfish were negatively impacted, but some species appear more resilient to than others. We need more cross-generational studies to understand the effects of acidification at the population level.

EH: We will use the risk analysis to develop different scenarios for an ecosystem model. For example, if we find one species to be at high risk, we would use the ecosystem model to simulate low survival for that species, which would enable us to look at how declines in one species might impact other parts of the food chain.

AP: I am working with my NOAA partners to develop models for Bering Sea snow crab and Tanner crab because much of the catch of Tanner crab is due to the fishery for snow crab. I am interested in determining the cumulative effects of ocean acidification and bycatch on the profitability of the fishery.

SAFS website. Full article.