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two people stand next to scientific equipment in a boat

Ferry for Science

As the amount of carbon dioxide in the atmosphere increases, about a quarter of it is absorbed by the ocean resulting in increasingly acidic waters. Estimates suggest that roughly 7 million tons of carbon dioxide now enter the ocean each day. In the Gulf of Alaska, cold temperatures, influx of freshwater from streams and glaciers, and naturally high concentrations of carbon dioxide mean that marine waters are predisposed to acidification. As a result, Alaska is expected to experience the effects of ocean acidification sooner and more severely than lower latitudes. Alaskan communities and ecosystems rely heavily on the health of the ocean, and the impacts of ocean acidification may be significant for marine life, seafood industries, and the economies of local communities.

To understand the complex dynamics of ocean acidification along the northern Pacific coast, continuous measurements are needed at a large scale. ACRC, the Hakai Institute, the Alaska Ocean Observing System (AOOS), the Alaska Ocean Acidification Network, and the NOAA Pacific Marine Environmental Laboratory have formed a partnership with the Alaska Marine Highway Systemto establish an unprecedented ocean monitoring effort. Every week, the M/V Columbia ferries passengers over 1,800 milesfrom Bellingham, Washington, up the coast of British Columbia, through the inside passage to Skagway, Alaska and back. The vessel is now doing much more than getting travelers and cargo from port to port. Since 2017 it’s been collecting, analyzing, and reporting back on the surface seawater chemistry along its route, the longest ferry run in North America. Hakai Institute scientist Wiley Evans installed and maintains the equipment on board that’s responsible for these measurements.

Every three minutes, the monitoring equipment collects a new seawater sample to analyze for dissolved oxygen, temperature, carbon dioxide, and salt content. This year-round data collection marks an advance in the understanding of the rate and trends of acidification of coastal waters, at a scale never conducted before. Measurements of this frequency and extent can help determine acidification hotspots as well as refugia, and help fishery, mariculture, tourism, and wildlife managers mitigate and adapt to acidification patterns.

With the data collected since monitoring began in 2017, trends in surface seawater chemistry are already being observed. Measurements of seasonal abundance of aragonite, a mineral type of calcium carbonate used by some shellfish and plankton species to grow shells, show that surface water is most corrosive in the fall and winter. As seawater pH levels lower, marine organisms vulnerable to acidification struggle to build and maintain their shells. When spring arrives, phytoplankton blooms remove carbon dioxide from the water through photosynthesis, and increasing water temperatures make aragonite more available to shelled marine organisms. These seasonal shifts are part of naturally-driven processes, but ocean acidification could push pH levels beyond key thresholds that some aquatic organisms can adapt to.

Soon, the data from the monitoring system will stream directly to an online database atAOOS, where coastal communities can observe changes that could affect their livelihoods and take measures to manage the impacts.

a researcher selects mussels for sampling on a beachShellfish Toxicity Monitoring

Along the vast coastline of Southeast Alaska, communities have relied on shellfish for millennia, but this abundant food source can be deadly due to toxins caused by harmful algal blooms (HABs).HABs of the phytoplanktonAlexandriumcan occur at any time of year, although they occur more frequently in the summer months when the ocean temperatures are warmer.Alexandriumblooms often produce a suite of toxins called paralytic shellfish poison (PSP), which can accumulate in shellfish such as clams and mussels. At high concentrations, PSP can cause illness or death in humans, birds, and marine mammals. There have been 117 reported cases of PSP in Alaska between 1993 and 2014, including 5 fatalities, the large majority of which occurred in Southeast Alaska. Though not a new phenomenon, these blooms are becoming increasingly difficult to predict and can have dire economic and public health impacts to the areas they affect.

The processes that drive harmful algal blooms in Alaska are not well understood, and Alaska is the only West Coast state that lacks a statewide biotoxin monitoring program. In addition, climate change and ocean acidification could increase the frequency and severity if blooms, meaning that the risk of PSP-related illness and death may grow.

The creation of theSoutheast Alaska Tribal Toxins(SEATT) network in 2013 united communities in addressing the risks of shellfish harvest by implementing a monitoring program and establishing a state of the art analysis lab. Before SEATT, the only truly safe way to eat shellfish in some Southeast Alaska communities was to buy them from a store, as the nearest existing shellfish testing facility in Anchorage was prohibitively far or expensive from some communities. Through the SEATT program, fifteen tribal organizations in Southeast Alaska communities monitor water quality and collect shellfish to be tested every two weeks at local harvesting sites. The SEATT lab can process samples for subsistence, recreational, and commercial harvesters within a 24 hour window once received. Still, not every community has the resources to test for PSP, and because toxicity can change over a matter of days, the results become increasingly unreliable in the time passed since testing. The availability of timely, cost-effective testing facilities is imperative for safe shellfish consumption, but knowing which environmental conditions drive harmful algal blooms could help concentrate toxicity testing around high-risk time periods and areas.

To address this, ACRC postdoctoral researcher John Harley is collaborating with the SEATT network to compile the vast database of environmental data and shellfish toxin levels they have collected into tool that may help map and predict PSP events. By linking environmental data such as sea surface temperature, freshwater input, and solar radiation with data on shellfish PSP toxin levels over a period of years, Dr. Harley is creating a model that weighs the influence of these combined factors to determine how likely an area is to have toxic shellfish. By training the model using data from previous blooms, it will eventually be able to use real-time environmental data to predict PSP risk in areas around Southeast Alaska.

The resulting tool could lower the risk of PSP death and illness, allow communities to safely harvest shellfish even without monitoring programs, and inform mariculture management practices. In addition to these seasonal predictions, determining long term trends in harmful algal bloom occurrence as affected by ocean acidification and climate change will help communities prepare for future impacts of PSP to food availability and commercial shellfish industries.

 
 

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