How Mangroves Breathe Underwater
Field Measurements of Internal Oxygen Dynamics During Tidal Inundation
Background
The intertidal zone represents one of the most physiologically challenging environments for plants, where tidal inundation strongly limits oxygen availability in waterlogged sediments. Mangrove forests persist in this dynamic habitat through specialized adaptations that allow them to cope with alternating flooded and exposed conditions. During inundation, reduced oxygen diffusion creates anoxic conditions that constrain root respiration and aerobic microbial activity, requiring mangroves to rely on aerial structures to transport oxygen to submerged tissues. However, the extent to which these internal oxygen transport mechanisms regulate tolerance to prolonged inundation remains poorly understood. Understanding these processes is increasingly important as global mangrove decline and climate-driven environmental changes threaten the persistence and ecosystem services provided by these coastal ecosystems.
Set-up/Sample
As part of Project Halo, field measurements were conducted in mangrove forests to investigate oxygen dynamics within aerial structures across contrasting tidal conditions. A portable PyroScience FireSting-O2 oxygen measurement system equipped with oxygen probes and temperature sensors was used to monitor internal oxygen availability and surrounding environmental conditions during tidal transitions. The oxygen probes were deployed within mangrove tissues, while temperature sensors recorded conditions in the adjacent sediment environment. Both instruments were suitable for submerged applications, allowing measurements to be collected throughout the tidal cycle under natural field conditions.
Fig. 1 Field measurements set-up: Oxygen probes were inserted in vegetable tissue for measuring its variation during the tidal cycle.
Results
The results revealed a consistent relationship between internal oxygen dynamics and tidal fluctuations, indicating that inundation strongly influences oxygen availability within mangrove aerial structures. These findings provide new insights into how mangroves regulate oxygen transport under changing hydrological conditions and contribute to a better understanding of the mechanisms supporting their persistence in the intertidal environment.
Fig. 2 Oxygen in aerial structures pattern when exposed and submerged during a tidal cycle.
Conclusion
These measurements will contribute to a broader ecological study aimed at understanding the functional responses of mangrove forests to changing tidal regimes and environmental conditions. Integrating internal oxygen dynamics with hydrological and ecological variables will provide new insights into how mangrove species adapt to fluctuating inundation patterns and how these mechanisms influence ecosystem functioning in intertidal environments.
Giulia Fiantanese
Project HALO, Water Research Laboratory, UNSW
28/7/26