title: Multiple sources driving the organic matter dynamics in two contrasting tropical mangroves.
abstract: In this study, we have selected two different mangroves based on their geological, hydrological and climatological variations to investigate the origin (terrestrial, phytobenthos derived, and phytoplankton derived) of dissolved organic carbon (DOC), particulate organic carbon (POC) in the water column and the sedimentary OC using elemental ratios and stable isotopes. Qeshm Island, representing the Iranian mangroves received no attention before this study in terms of DOC, POC biogeochemistry and their sources unlike the Sundarbans (Indian side), the world's largest mangrove system. Slightly higher DOC concentrations in the Iranian mangroves were recorded in our field campaigns between 2011 and 2014, compared to the Sundarbans (315±25μM vs. 278±42μM), owing to the longer water residence times, while 9-10 times greater POC concentration (303±37μM, n=82) was linked to both suspended load (345±104mgL(-1)) and high algal production. Yearlong phytoplankton bloom in the mangrove-lined Persian Gulf was reported to be the perennial source of both POC and DOC contributing 80-86% to the DOC and 90-98% to the POC pool. Whereas in the Sundarbans, riverine input contributed 50-58% to the DOC pool and POC composition was regulated by the seasonal litter fall, river discharge and phytoplankton production. Algal derived organic matter (microphytobenthos) represented the maximum contribution (70-76%) to the sedimentary OC at Qeshm Island, while mangrove leaf litters dominated the OC pool in the Indian Sundarbans. Finally, hydrographical settings (i.e. riverine transport) appeared to be the determinant factor in differentiating OM sources in the water column between the dry and wet mangroves.
authors.affiliation: Institut Universitaire Européen de la Mer, UBO, UMR 6539 LEMAR, rue Dumont dUrville, 29280 Plouzane, France; Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany. Electronic address: raghab.ray@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Ray
authors.affiliation: Leibniz Center for Tropical Marine Ecology, Fahrenheitstr. 6, 28359 Bremen, Germany; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Shahraki
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D007492:Iran; D012623:Seawater / Q000737:chemistry*; D053833:Wetlands
chemical_list: D006812:Humic Substances
keywords: India; Iran; Mangroves; Organic carbon; Stable isotopes