Mangroves are ecologically and economically important forests of the tropics. They are highly productive ecosystems with rates of primary production equal to those of tropical humid evergreen forests and coral reefs. Although mangroves occupy only 0.5% of the global coastal area, they contribute 10–15% (24 Tg C y−1) to coastal sediment carbon storage and export 10–11% of the particulate terrestrial carbon to the ocean. Their disproportionate contribution to carbon sequestration is now perceived as a means for conservation and restoration and a way to help ameliorate greenhouse gas emissions. Of immediate concern are potential carbon losses to deforestation (90–970 Tg C y−1) that are greater than these ecosystems' rates of carbon storage. Large reservoirs of dissolved inorganic carbon in deep soils, pumped via subsurface pathways to adjacent waterways, are a large loss of carbon, at a potential rate up to 40% of annual primary production. Patterns of carbon allocation and rates of carbon flux in mangrove f...

Carbon Cycling and Storage in Mangrove Forests

Mangrove forests are highly productive, with carbon production rates equivalent to tropical humid forests. Mangroves allocate proportionally more carbon belowground, and have higher below- to above-ground carbon mass ratios than terrestrial trees. Most mangrove carbon is stored as large pools in soil and dead roots. Mangroves are among the most carbon-rich biomes, containing an average of 937 tC ha-1, facilitating the accumulation of fine particles, and fostering rapid rates of sediment accretion (∼5 mm year -1) and carbon burial (174 gC m-2 year -1). Mangroves account for only approximately 1% (13.5 Gt year -1) of carbon sequestration by the world’s forests, but as coastal habitats they account for 14% of carbon sequestration by the global ocean. If mangrove carbon stocks are disturbed, resultant gas emissions may be very high. Irrespective of uncertainties and the unique nature of implementing REDD+ and Blue Carbon projects, mangroves are prime ecosystems for reforestation and restoration.

Carbon sequestration in mangrove forests

All chapters of the previous edition [see HbA 37, 2103] have been completely rewritten to cover the rapid increase in research in this area. The number of literature citations have been reduced by referring to recent review articles and the book aims at a comprehensive and critical rather than encyclopaedic summary of the data of environmental chemistry. The 1st 4 chapters deal with air, water, rocks and soils; the cycling of C, N, H, O2 and S in the biosphere are covered in 1 chapter and the elemental Other CABI sites 

Environmental Chemistry of the Elements

Effective rhizoinoculation and biofilm formation by arsenic immobilizing halophilic plant growth promoting bacteria (PGPB) isolated from mangrove rhizosphere: A step towards arsenic rhizoremediation.

Ecosystem Service Value assessment of a natural reserve region for strengthening protection and conservation.

Carbon sequestration and annual increase of carbon stock in a mangrove forest

Biogeochemical controls of arsenic occurrence and mobility in the Indian Sundarban mangrove ecosystem.

Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose an environmental risk. Adsorption and desorption are hypothesized to be the major processes controlling arsenic retention in surface sediment under oxic/suboxic condition. This study aims to investigate sorption kinetics of As(III & V) and its feedback to arsenic mobilization in the mangrove sediment. It ranges from sand to silty clay loam and shows the adsorption of As(III & V) following the Langmuir relation. Estimates of the maximum adsorption capacity are 59.11 ± 13.26 μg g−1 for As(III) and 58.45 ± 8.75 μg g−1 at 30°C for As(V) in the pH range 4 to 8 and salinity 15–30 psu. Extent of adsorption decreases with increasing pH from 4 to 8 and desorption is the rate-limiting step in the reaction of arsenic with sediment. Arsenic in the sediment could be from a Himalayan supply and co-deposited organic matter drives its release from the sediment. Arsenic concentration in the sediment is well below its maximum absorption capacity, suggesting the release of sorbed arsenic in pore water by the microbial oxidation of organic matter in the sediment with less feedback of adsorption.

Adsorption kinetic control of As(III & V) mobilization and sequestration by Mangrove sediment

This study reports the measurement of stability constants for the interaction of As (V and III) and Sb (V and III) with humic substances extracted from aquatic sediments of the Sundarban mangrove forest ecosystem. It was observed that As and Sb formed a slightly more stable association with fulvic acid (FA) than with its humic acid (HA) counterpart. Quenching of fluorescence at increasing As (III and V) or Sb (III and V): FA or HA ratios was obtained that ideally correspond to a 1:1 complexation model. Quite strong complexation of As and Sb by FA and HA occurs at neutral pH, indicating that HA and FA probably markedly affect the mobility of As and Sb in the mangrove environment.

Implication of Organic Matter on Arsenic and Antimony Sequestration in Sediment: Evidence from Sundarban Mangrove Forest, India

Vanadium (V), niobium (Nb), and tantalum (Ta), recognized as Technology-Critical Element (TCE), are highly growing in demand for industrial development. Despite their economic relevance, little is known about their environmental concentrations, especially in marine ecosystems like mangroves. This paper describes concentrations and distribution patterns of Group Va elements (V, Nb and Ta) in plant organs and sediments from diverse mangroves of the Indian Sundarbans. Sediment cores and plant organs of eight dominant mangrove species were sampled and analyzed for V, Nb and Ta by ICP-MS. Stable carbon isotope (δ13C) in mangrove leaves were analyzed by EA-IRMS. Mean concentrations (mg kg−1) of V, Nb and Ta decreased in the order V (84.7 ± 12.5) > Nb (37.5 ± 4) > Ta (3 ± 0.8) in the sediment and V (0.6 ± 0.6) > Nb (0.02) > Ta (0.002) in the mangrove plants. Species-specific variability in bioaccumulation factor (V: 0.012–0.035; Nb: 0.001–0.003; Ta: 0.001–0.005), translocation factor (V: 0.5–5.1; Nb: 0.26–7.06; Ta: 0.22–2.56) and enrichment factor (V: 0.008–0.027; Nb: 0.0002–0.001; Ta: 1.0 × 10−5-3.0 × 10−6) indicated different partitioning of Group Va elements within the plant organs and varying degree of mangrove uptake efficiency. Results showed a general decrease in V, Nb and Ta concentrations with their increasing atomic weight. Their total concentrations in plants were related to the degree of enrichment of substrate sediments. The phytoextraction capacity varied amongst mangrove species depending on their CO2 uptake efficiency. Given increased demand for TCEs, results may have important implications for bioremediation processes.

S. K. Mandal

Papers

Carbon sequestration and annual increase of carbon stock in a mangrove forest

Biogeochemical controls of arsenic occurrence and mobility in the Indian Sundarban mangrove ecosystem.

Adsorption kinetic control of As(III & V) mobilization and sequestration by Mangrove sediment

Implication of Organic Matter on Arsenic and Antimony Sequestration in Sediment: Evidence from Sundarban Mangrove Forest, India

Bioaccumulation of vanadium (V), niobium (Nb) and tantalum (Ta) in diverse mangroves of the Indian Sundarbans