Human impacts on methane emission from mangrove ecosystems in India

Abstract

This study deals with the emission of methane in relation to changing environmental conditions and human impact, in three mangrove ecosystems of south India. Time-varying¯uxes of methane adopting the close chamber technique were used to estimate CH 4 emission from an unpolluted site (Pichavaram mangroves) and two polluted sites viz. (1) Ennore Creek mangroves (affected by fertilizer ef¯uents and crude oil discharges) and (2) Adyar estuary mangroves (affected by the discharges of organic and industrial wastes), covering monthly and seasonal variations. The results indicate annual average CH 4 emissions of 7.4, 5.02 and 15.4 mg m )2 h )1 from the sediment±water interface of the Pichavaram, Ennore Creek and Adyar estuary respectively. Emission characteristics obtained at Pichavaram mangroves represent a natural variability with changing physico-chemical factors, whereas the emission characteristics at Ennore Creek and Adyar estuary mangroves show anthropogenic in¯uence. Several environmental factors such as oxygen availability, organic matter, soil physical and chemical properties, in addition to human-mediated interventions have been identi®ed as in¯uencing emission rates in the mangrove ecosystems. Preliminary CH 4 emission estimates for the mangrove ecosystems along the Indian subcontinent and the tropical and subtropical coastline of the world by linear extrapolation based on surface area range from 0.05 to 0.37 and 2.8 to 19.25 Tg CH 4 year )1 respectively. Our results also highlight the impact of human activities on future emission of methane from the mangrove ecosystems.

Seasonal variation in nitrous oxide and methane emissions from subtropical estuary and coastal mangrove sediments, Australia

“…Temperature (as sensible heat flux and/or sediment temperature) has been positively correlated with mangrove sediment N 2 O and CH 4 emissions (Yi Lu et al. 1999; Purvaja & Ramesh 2000; Mukhopadhyay et al. 2002; Allen et al.…”

Plant‐mediated methane emission from an Indian mangrove

“…However, methanogenesis in and methane emission from unpolluted mangroves have been regarded as minor, both in a particular ecosystem and on a regional scale (Sotomayor et al , 1994; Giani et al , 1996; Alongi et al , 2000, 2001). More recently, however, we observed high methane emissions from both polluted and unpolluted coastal wetlands in South India (Purvaja & Ramesh, 2000a, 2001). These observations indicated for the first time that coastal ecosystems of the tropics might emit considerable amounts of methane.…”

Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

“…Most of organic carbon inputs are deposited in the lagoons (Castel et al 1996) where they fuel intense mineralization (Sorokin et al 1996) leading to the efflux of CO 2 to the atmosphere (Koné et al 2009). A few studies have addressed the CH 4 efflux to the atmosphere from shallow or/and intertidal lagoon sediments (Purvaya and Ramesh 2000;Verma et al 2002;Hirota et al 2007), but to our best knowledge, no studies have previously addressed the dynamics of CH 4 in surface waters of lagoons, and related diffusive air-water CH 4 fluxes.…”