Will ocean acidification affect marine microbes?

Area of Science:

• Marine biology
• Oceanography
• Biogeochemistry

Background:

• Rising atmospheric carbon dioxide (CO2) is decreasing surface ocean pH, leading to concerns about ocean acidification.
• Current assessments of ocean acidification's impact on marine microbes often overlook natural pH variability.
• Ocean pH naturally fluctuates with seasons, depth, and productivity gradients.

Purpose of the Study:

• To evaluate the impact of natural pH variability on marine microbial communities.
• To provide context for ocean acidification research by comparing marine and freshwater pH changes.
• To propose a null hypothesis regarding the effect of future ocean pH conditions on biogeochemical processes.

Main Methods:

• Literature review and synthesis of existing data on ocean pH variability.
• Comparison of natural pH fluctuations in marine and freshwater environments.
• Analysis of microbial adaptation to pH changes in different aquatic ecosystems.

Main Results:

• Surface ocean pH exhibits significant natural variability influenced by microbial CO2 cycling and nitrification.
• Freshwater microbes routinely tolerate pH changes far exceeding projected ocean acidification levels.
• Both marine and freshwater microbial communities have evolved under variable pH conditions.

Conclusions:

• Natural pH variability in the ocean is substantial and often overlooked in acidification studies.
• Marine microbes' historical exposure to pH fluctuations suggests potential resilience to future changes.
• A null hypothesis posits that major ocean biogeochemical processes, excluding calcification, will remain largely unchanged under future higher CO2/lower pH conditions, pending contrary evidence.