Transcriptomic responses to ocean acidification in larval sea urchins from a naturally variable pH environment

Area of Science:

• Marine Biology
• Oceanography
• Genomics

Background:

• Some marine ecosystems naturally experience pH declines similar to predicted future ocean acidification (OA).
• The molecular mechanisms enabling organisms to tolerate low pH, especially calcifying species, remain largely unknown.
• It is uncertain if adaptation to current pH variability confers future OA resistance.

Purpose of the Study:

• To investigate the molecular mechanisms of pH tolerance in marine organisms.
• To determine if natural exposure to low pH in intertidal habitats confers resilience to future ocean acidification.
• To analyze the transcriptomic response of purple sea urchins to varying pH levels.

Main Methods:

• Monitoring natural pH dynamics in a Northeast Pacific intertidal habitat.
• Culturing purple sea urchin (Strongylocentrotus purpuratus) larvae in CO2-acidified seawater.
• Analyzing gene expression using transcriptomics to assess molecular responses to pH stress.

Main Results:

• Purple sea urchin larvae may adjust calcium bioavailability and skeletogenic pathways to maintain calcification under low pH.
• Larvae exhibit distinct transcriptional responses to different pH stress magnitudes.
• A robust response to present-day pH conditions was observed, contrasting with a muted response to near-future scenarios.

Conclusions:

• Purple sea urchin larvae possess mechanisms to cope with low pH, including adjustments to calcification processes.
• Adaptation to present-day pH fluctuations may not guarantee resilience to projected future ocean acidification.
• Understanding these molecular mechanisms is crucial for predicting the impact of OA on marine calcifying species.