Abstract:
Mangrove ecosystems store carbon in large quantities within their ecosystem pool. As a ‘Blue carbon
ecosystem’, mangroves play a crucial role in sequestering carbon dioxide (CO2) and maintaining the
balance of atmospheric CO2 levels. However, anthropogenic disturbance is a major threat to mangrove
areas that directly affects ecosystem functions. Therefore, the current study aims to estimate the Soil
Organic Carbon (SOC) content of mangroves in human-disturbed and relatively undisturbed areas in
Rekawa Lagoon, Southern Sri Lanka. Soil samples were collected using the transect method from the
three regions: fringe, middle, and back mangrove regions using a soil corer (50cm length and 3.4cm
diameter). In total, 216 soil samples were collected in two depth ranges: 0-25cm and 25-50cm and
analyzed using the Loss on ignition (LOI) method. T-test and ANOVA test were performed to analyze
the data using R-4.2.2 statistical software. The total average SOC contents in the 0-50 cm depth range
of the relatively undisturbed and disturbed mangrove areas were 312.85±14.76 Mg C ha-1 and
260.52±26.34 Mg C ha-1, respectively (p < 0.05). The relatively undisturbed mangrove areas showed
higher average SOC content across all regions when compared to the disturbed areas. The average SOC
contents of the fringe, middle, and back, in the relatively undisturbed areas were 279.50 ± 21.88 Mg C
ha-1, 312.56±13.06 Mg C ha-1, 346.47±34.54 Mg C ha-1 respectively, and the disturbed areas were
207.59±33.65 Mg C ha-1, 238.22±36.00 Mg C ha-1, and 335.74±37.66 Mg C ha-1, respectively (p<0.05).
The current study concludes that anthropogenic disturbances significantly lower the SOC content. The
reduction of the SOC content in disturbed areas suggests that anthropogenic disturbances could lead to
the potential release of approximately 52.33 Mg C ha-1 from the topsoil (0–50 cm) into the atmosphere.
Further, the study emphasizes the importance of conserving undisturbed mangrove areas, with insight
towards climate change mitigation.
