Leaf metabolites and carbon harvesting: Insights into spatial extremities of a mangrove ecosystem in Mumbai, India

Mangrove physiological traits are largely driven by ecogeomorphic conditions and environmental stressors. These traits provide adaptive strategies to enable growth and productivity in challenging coastal and marine settings. Moreover, plant biodiversity is a key component to determine the habitat richness, functioning and larger ecosystem dynamics and has a central role in carbon sequestration processes. The urban mangrove green cover at Carter Road in Mumbai harbors key species like Sonneratia alba Sm., Sonneratia apetala Buch.-Ham., Rhizophora mucronata Poir., and Avicennia marina (Forssk.) Vierh. They were evaluated for essential phytochemicals like proline and chlorophyll in ambient ecosystem conditions. Proline was highest in R. mucronata (22.42 ± 0.40 µmol g-1) and lowest in S. apetala (18.93 ± 0.14 µmol g-1). Chlorophyll a, Chl b, Chla+b and Chl a/b varied significantly at the two positional extremes –landward and seaward, with considerably higher values recorded at the landward edge. Chl a content (mg g-1) at the landward edge ranged from 1.60 ± 0.03 to 1.31 ± 0.12 and were much higher in comparison to the seaward fringe (0.71 ± 0.06 to 0.58 ± 0.02). Positional increments were also observed for Chl b and Chl a+b. Linear mixed effect model was significant for positional distinctiveness of soil carbon parameters like soil organic carbon (SOC%),bulk density and soil strata organic carbon (SOCOrg). The SOC (%) gave maximum values of surface soil (0-10 cm) at seaward (1.41 ± 0.06) and landward (2.08 ± 0.31) positions with corresponding SOCOrg (Mg C ha-1) values of 18.05 ± 1.711 and 22.367 ± 2.35 respectively, indicating significant carbon deposits landwards. The standing biomass carbon for aboveground and belowground biomass was 357.00 ± 33.09 Mg C ha-1 and 99.39 ± 9.21 Mg C ha-1 respectively. Thisstudy provides insights into modulation of Chlorophyll content impacting the ecosystem productivity and its carbon storage propensities.