Abalone Mortality Associated With Hypoxia in Tidepools During a Summer Heatwave

Area of Science:

• Marine Biology
• Ecology
• Climate Change Impacts

Background:

• Marine heatwaves are increasing globally, threatening marine ecosystems.
• Intertidal zones are particularly vulnerable to extreme temperatures and altered water exchange during heatwaves.
• Roe's abalone (Haliotis roei) are commercially important mollusks inhabiting Western Australian intertidal rocky platforms.

Purpose of the Study:

• To investigate the causes of differential mortality of Roe's abalone during a marine heatwave event.
• To compare environmental conditions between tidepools and exposed platform surfaces inhabited by abalone.

Main Methods:

• Field observations of abalone mortality on intertidal platforms.
• In-situ measurements of seawater temperature and dissolved oxygen concentrations within tidepools and on platform surfaces.
• Correlation analysis between environmental parameters and abalone survival.

Main Results:

• Substantial mortality of Roe's abalone was observed in intertidal tidepools, but not on adjacent exposed platform surfaces.
• Seawater temperatures were similar between tidepools and platform edges during the heatwave.
• Dissolved oxygen levels were significantly lower in tidepools, reaching hypoxic conditions.

Conclusions:

• Oxygen depletion, potentially combined with heat stress and limited water exchange, likely caused the high mortality of Roe's abalone in tidepools.
• Tidepool habitats may act as ecological traps during marine heatwaves for intertidal species.
• Understanding these dynamics is crucial for managing vulnerable marine populations facing climate change.