The Hatcheries That Are Helping Oysters Pass the Acid Test

The world's shellfish industry is facing a significant threat from increasing ocean acidification, which is caused by the ocean absorbing higher carbon dioxide levels. This is particularly impacting the ability of organisms like oysters, mussels, and clams to build their shells. However,?oyster hatcheries are crucial in mitigating these challenges and ensuring the future of oyster farming.

How Oyster Hatcheries Work

Most farmed oysters begin their lives in a hatchery. The process typically involves:

• Starting with "moms and pops" to produce billions of microscopic oyster larvae.
• These larvae are suspended in seawater, where they feed on phytoplankton for a couple of weeks.
• The tanks used to grow the larvae are aerated with a mixture of fresh seawater and oxygen.
• This method of spawning oysters in hatcheries leads to a 71% higher survival rate than in the wild.

The Threat of Ocean Acidification

In 2007, hatcheries on the West Coast of the United States experienced a series of catastrophic die-offs of larvae, initially baffling hatchery technicians. This was eventually attributed to upwellings of deep ocean water with a pH of 7.8, which was too acidic for the oyster larvae. Surface ocean pH is typically above 8.0. This event served as a foreshadowing of the potential future impact of ocean acidification on the shellfish industry. Ocean acidification is a result of rising human-caused carbon dioxide emissions, which alter the building blocks that organisms use to make their shells, resulting in smaller, weaker shells.

Adaptation and Resilience

Following the die-offs, some oyster businesses have invested in building their hatcheries and implementing strategies to counteract the effects of ocean acidification.

• Hog Island Oyster Co. acquired a seawater pumping permit and now mixes its ocean water intake with ash to increase its alkalinity.
• This ensures that the larvae are not damaged by declining ocean pH.
• Other shellfish growers have started to implement local monitoring strategies and apply alkaline substances to seawater.

Other strategies being explored include:

• Breeding oysters that are more tolerant to changing ocean conditions.
• Looking at bays with abundant seagrasses as natural refuges for shellfish culture.
• Co-culturing seaweed with shellfish.
• Culturing alternative species that are less vulnerable or more able to adapt.

The Broader Impact

The challenges experienced on the West Coast of the US have highlighted the global implications of ocean acidification. Scientists are now warning that the same issues could affect other regions, like New England. For example, the Gulf of Maine is warming faster than any other body of water and is also threatened by increasing acidification. Shellfish farmers there are experimenting with co-growing seaweed and shellfish in halo-shaped farms to help the shellfish grow thicker shells.

The situation has also prompted the public to become more aware of the impact of carbon pollution and the need to decrease carbon emissions.

Conclusion

The threat of ocean acidification to the shellfish industry is real and ongoing. However, hatcheries and farmers have demonstrated their ability to adapt and mitigate these challenges. By developing resilient strains of oysters and implementing innovative techniques, the shellfish industry is striving to navigate the effects of climate change.