Oysters: Climate Change Served Raw

How our air quality might be killing our shuckable friends from the sea

The Hog Island Oyster Company spends more time thinking about greenouse gasses than you might imagine.  For them, climate change isn’t just a threat to their operating model, total yield, or harvesting costs, but to the very survival of oysters as a species. Hog Island Oysters are grown in the tidal waters of Tomales bay, where changing tides bring in rich nutrients and phytoplankton from the sea, creating an ideal environment for growing oysters1.  In the past years, however, the tides have been bringing in a less welcome guest, and in increasing quantity: CO2 dissolved from the atmosphere into the ocean.

 Larval oysters are small enough to grow in a controlled "nursery"
Larval oysters are small enough to grow in a controlled “nursery”

The threat to the oyster industry is not the global temperature increase, but the acidification of the sea.  Roughly 30% of the CO2 that is released into the atmosphere is absorbed by the ocean, which drastically increases the acidity of the water2. Further, “upwelling”, or the phenomena where the wind pushes surface water away from shore and circulates deeper (and more acidic) water toward the shore/tidelands, has been on the rise due to changing weather patterns.  This increase in acidity effectively dissolves the calcium carbonate shells of many shellfish, leaving smaller softer shells and weaker oysters3.  This impact is most notable in the oyster’s larval stage, as the weakened state makes the baby oyster more susceptible to disease.  Hog Island noticed a sharp increase in mortality of infant oysters several years ago, and has since moved their “nursery” into a controlled environment, to protect from the ocean’s acidity in the oyster’s most vulnerable stage.  This strategy is working for the time being, but the company is unable to keep more mature oysters in such a controlled environment as the larger oysters take considerably more space and require much more access to the nutrients carried in by the ocean tides.


As the oysters’ environment become more acidic due to increase in CO2 concentrations (expected to rise

Keeping the oysters in a controlled environment becomes increasingly difficult as they grow
Keeping the oysters in a controlled environment becomes increasingly difficult as they grow

from 400 ppm to 600 ppm by the end of the century2), farmers will need to control the oysters’ environment more carefully and later into their life, which will cause an exponential increase in cost to Hog Island. The company is currently preparing for future climate change by building an additional “nursery” to develop young oysters in Humboldt Bay, CA, and by pairing with researchers from UC Davis’ Bodega Marine Laboratory to develop future solutions to the threat of climate change3.


The company’s operating model is most likely to change through significant increase in R&D expenditures to keep the oysters alive. One avenue to explore via research is selective breeding, a well-known practice that has been used in the past to maximize oyster size, yield, and susceptibility to disease4. The facilities and staff required to breed, grow, and measure different breeds of oyster would amount to a large increase in the firm’s expenses.


Genetic modification should also be considered as a tool for the company and researchers.  A study released in 2009 showed that animals with lower concentrations of magnesium in their shells were less susceptible to increased ocean acidity, and thrived in water with up to 900 ppm of CO22. Genetic engineering has also already been used on oysters, but again to increase overall yield as opposed to increase resilience toward ocean acidity5.  If researchers could find small modifications to the genetics of the oyster’s shell to decrease the magnesium levels, it may lead to a more resilient breed.


Lastly, Hog Island Oyster Co may need to consider a dramatic overhaul of their farming technique by building facilities (isolated from the ocean) to farm their oysters from the larval stage through maturity.  This would drive costs up significantly, as the 160 acres of growing area would need to be isolated from the sea and controlled for acidity.  They would then need to find an acceptable replacement for the ocean’s natural circulation: the food and nutrients brought in with the tides and the waste product from the oysters carried away. Engineering a replacement for the natural tide would be the most difficult, as oyster taste and quality is driven by some very small factors in their specific environment, and finding the right combination of nutrients, minerals, and other qualities of the water would take intense experimentation.  This will be a research and capital heavy project but may very well be required if CO2 levels in the ocean continue to rise over the next few decades.


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[1] Hog Island Oyster Co. “Farming Oysters”  https://hogislandoysters.com/oysters/farming

[2] Oceanus Magazine. “Ocean Acidification: A Risky Shell-Game”  http://www.whoi.edu/oceanus/feature/ocean-acidification–a-risky-shell-game

[3] San Francisco Chronicle. “Oyster Farmers Worried as Climate Change Lowers Ocean pH” http://www.sfchronicle.com/bayarea/article/Oyster-farmers-worried-as-climate-change-lowers-6445523.php

[4] (abstract) Calvo et. al “Dual disease resistance in a selectively bred eastern oyster,Crassostrea virginica, strain tested in Chesapeake Bay” http://www.sciencedirect.com/science/article/pii/S004484860200399X

[5] The Telegraph. “Genetically ‘Improved’ Oysters Behind France’s Shellfish Plague” http://www.telegraph.co.uk/news/worldnews/europe/france/2656892/Genetically-improved-oysters-behind-Frances-shellfish-plague.html




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Student comments on Oysters: Climate Change Served Raw

  1. As an oyster enthusiast, this presents some concern to me. I wasn’t aware that the impending threat of air pollution was so direct in harming oyster shells. Based on the solutions identified by this article, my question focuses on where the additional funding would come from to do selective breeding. I agree that selective breeding is an effective method since it simply speeds up the natural selection process, but wonder if some of the funding could be government sponsored. Oysters serve as a natural water filter in the ocean, and are a necessary component of the ecosystem. Allocating some public or even private funding to this endeavor could speed up the process and counteract the current threats from acidic upwelling and C02.

  2. This is a really interesting article!! I, too, love oysters and would be extremely sad to see their extinction.

    I think the point of genetically modifying the magnesium levels in oysters’ shells is an interesting one. My impression is that Hog Island Oyster company is small and would not have the margins from their oysters in order to invest in the R&D required to do the research that tests the efficacy, impact on taste, and FDA testing that would have to accompany these new oysters. Because of that, I also feel like if they were to raise money to do so, they may not be incentivized to do so given the free-rider problem that comes with being the first mover.

    Because of this, I think that Hog Island will have to focus on other measures to combat climate change, such as forming a collective with other oyster companies to pool resources together to do this research or identify a way to do farming on a larger, more sustainable scale.

  3. As someone who has been to the Hog Island Oyster farm in Tomales Bay numerous times, this is of great concern to me. I agree with “climatechangewoes” that Hog Island does not have the necessary resources itself to perform the R&D that might result in new types of oysters that might be resistant to some of the environmental impacts Hog Island has seen. I also think it is unlikely that a collective of oyster companies would have the necessary resources.

    Unfortunately, Hog Island will likely be forced to expand their farming practices that isolate their oysters from the ocean. I’m sure that this will have the unfortunate side effect of reducing the quality and variety of oysters they farm, as well as increase the prices for their oysters.

    I do think that “J2G18” brings up a good point that could potentially help Hog Island acquire funds from the government to perform some of the research that they would otherwise be unable to do. In addition to the filtering that oysters perform (that J2G18) mentions, oyster beds have also traditionally helped prevent erosion. While many large, natural oyster beds have been decimated (either by harvesting, climate change, or other means), local and federal governments would be wise to look into oyster beds as a way to help address other impacts of climate changes caused by rising sea levels. The Oyster Restoration Workgroup has some interesting information about the efficacy of oysters in preventing erosion: http://www.oyster-restoration.org/living-shorelines/

  4. Very interesting post!

    The thought of losing our oyster beds to acidification born from climate change is even more troubling when you consider that oysters more than pull their weight in combating climate change — from source below “Recent work done by Roger Newell of the University of Maryland shows that a healthy oyster habitat can reduce total added nitrogen by up to 20 percent. A three-acre oyster farm filters out the equivalent nitrogen load produced by 35 coastal inhabitants”. The ability of oysters to act as effective nitrogen sinks could potentially be a compelling argument for securing government investment in R&D to combat the effects of acidification. One potential avenue that R&D could explore, in addition to genetic modification, is multi-trophic (i.e., multi-species, different levels of the food chain) aquaculture which seeks to grow oysters in combination with another commodity that acts as a sink for ocean acidity (thereby improving at least local acidity conditions) — some species of seaweed could potentially fulfill this function/ could be genetically engineered to do so with potentially less backlash than genetically engineering the oysters themselves.


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