Temporal changes in physical, chemical and biological sediment parameters in a tropical estuary after mangrove deforestation

Abstract

a b s t r a c tDated sediment cores taken near the head and mouth of a tropical estuary, Nha-Phu/Binh Cang, in south central Viet Nam were analyzed for changes over time in physical, chemical and biological proxies potentially influenced by removal of the mangrove forest lining the estuary. A time-series of satellite images was obtained, which showed that the depletion of the mangrove forest at the head of the estuary was relatively recent. Most of the area was converted into aquaculture ponds, mainly in the late 1990's. The sediment record showed a clear increase in sedimentation rate at the head of the estuary at the time of mangrove deforestation and a change in diatom assemblages in the core from the mouth of the estuary indicating an increase in the water column turbidity of the entire estuary at the time of the mangrove deforestation. The proportion of fine-grained sediment and the d 13 C signal both increased with distance from the head of the estuary while the carbon content decreased. The nitrogen content and the d 15 N signal were more or less constant throughout the estuary. The proportion of fine-grained material and the chemical proxies were more or less stable over time in the core from the mouth while they varied synchronously over time in the core from the head of the estuary. The sediment proxies combined show that mangrove deforestation had large effects on the estuary with regard to both the physical and chemical environment with implications for the biological functioning.

Carbon in the Coastal Seascape: How Interactions Between Mangrove Forests, Seagrass Meadows and Tidal Marshes Influence Carbon Storage

“…The ability to trap sediments (and therefore to sequester carbon) is compromised if these habitats are degraded or removed. Case studies and modelling show how near-shore turbidity levels, distribution of fine sediments and sedimentation rates may change following mangrove removal [44][45][46]. Sediment trapping by mangroves can help protect sensitive coral sites from soil runoff [47], and similar effects are likely for seagrass; indeed, the enhanced sedimentation that destroyed the seagrass beds in Sabah [41] was caused by removal of forests, including neighbouring mangroves.…”

Descrição da comunidade microbiana ativa em solos de manguezais por metagenômica e metatranscriptômica

“…Estudos recentes mostram que os manguezais estão sob forte pressão de degradação, sendo que somente entre 1980 e 2005 houve uma redução de 30% a 50% da área de manguezais no mundo, como resultado do desenvolvimento urbano e mudanças climáticas (HOLGUIN et al, 2006;MAITI et al, 2013;ELLEGAARD et al, 2014). Esse ecossistema está sujeito a flutuações ao longo do dia, passando da condição alagada a seca em questões de horas alterando o potencial redox, salinidade, aeração dos solos entre outros (BARKER, 2009).…”