Seaweed farms provide refugia from ocean acidification

Area of Science:

• Marine Biology
• Oceanography
• Aquaculture

Background:

• Ocean acidification poses a significant threat to marine ecosystems.
• Seaweed farming is a proposed, yet understudied, adaptation strategy.
• Understanding the impact of seaweed farms on local water chemistry is crucial.

Purpose of the Study:

• To assess the efficacy of seaweed farming in mitigating ocean acidification.
• To quantify changes in pH and carbon system parameters within seaweed farms.
• To evaluate the potential of seaweed farms as refugia for marine organisms.

Main Methods:

• Comparison of pH and carbon system parameters in seaweed farm waters versus surrounding waters.
• Monitoring across three seaweed farms with varying species (Saccharina japonica, Gracilariopsis lemaneiformis, Porphyra haitanensis) in China.
• Analysis of dissolved oxygen and aragonite saturation state (Ωarag).

Main Results:

• Seaweed farms demonstrated efficient buffering of acidification, increasing pH by up to 0.10 units.
• Significant deficits in pCO2 (average 58.7 μatm) were observed within farms.
• Elevated dissolved oxygen and Ωarag were recorded, benefiting calcifying organisms.

Conclusions:

• Seaweed farming is a viable, scalable, and low-cost strategy to combat ocean acidification and deoxygenation.
• Farms can create localized refugia, enhancing marine organism resilience.
• Intense pH variability within farms may aid adaptation to future ocean conditions.