Abstract:
Current blue carbon frameworks emphasise carbon sequestration and under-evaluate the oxygenreleasing role, and hence capture only half of the biogeochemical contribution of mangrove ecosystems.
The current study evaluates the oxygen-releasing amount of existing mangrove biomass and its
temporal change over 2010 – 2025. The study was conducted at the Kadolkele Mangrove Reserve in
the Negombo Lagoon, Sri Lanka. Three random belt transects (10 m width) were laid perpendicular to
the shoreline and subdivided into 10m × 10m (100 m²) sampling units (12). Biomass (total above- and
belowground) of mangroves was estimated using allometric methods. The estimated amount of oxygen
released from the existing biomass was calculated by converting biomass into carbon stocks (applying
a carbon conversion factor of 0.47), then converting into molecular oxygen using the stoichiometric
relationships inherent to photosynthesis. The economic value of oxygen released by mangrove biomass
was estimated using a cylinder-based (medical oxygen cylinder) replacement approach. From 2010 to
2025, 18.8% of biomass increment and 16.5% of total organic carbon (TOC) level increment were
observed, resulting in a 21.1% of raise of oxygen release from 171.10 to 207.73 million L ha-1. The
economic value of the amount of oxygen released from the total mangrove area of 14 ha reveals a
proportional increment, rising from approximately LKR 10.06 billion (USD 30.5 million) in 2010 to
LKR 12.18 billion (USD 36.9 million) in 2025. Representing a theoretical ecosystem magnitude, the
estimated oxygen release from mangrove biomass per hectare corresponds to the annual oxygen
requirement of approximately 946 individuals in 2025 and 781 in 2010, based on the standard per capita
oxygen consumption. This study highlights the substantial ecological and economic value of mangrove
ecosystems through their role in oxygen production. Integrating oxygen-releasing ecosystem services
into policy frameworks will strengthen conservation strategies, highlighting the tangible benefits. This
quantification and economic valuation provide a novel and tangible metric for integrating ecological
functions into the blue economy framework.
