Preliminary evaluation of organic carbon sedimentation rates in Asian mangrove coastal ecosystems estimated by

The organic carbon accumulation rate in mangrove ecosystem was reported to be important sink of carbon as well as that in boreal peat accumulation. For the estimation of 10 years scale organic carbon accumulation rates at mangrove plantation coastal area, the 210Pb is expected to be suitable for decades scale estimation by its half-life, though it has possibility of bio-/physical- turbation effect in applying 210Pb chronology, especially in Asian mangrove ecosystem where the anthropogenic physical turbation by coastal fishery is vigorous. We studied the organic carbon and 210Pb accumulation rates in subtropical mangrove coastal ecosystems in Japan, Vietnam and Thailand to remove the effect of bio- anthropogenic turbation on organic carbon accumulation. We finally concluded that 210Pb was applicable to estimate organic carbon accumulation rates in these ecosystems. The measured organic carbon accumulation rates using 210Pb in mangrove coastal ecosystems of Japan, Vietnam and Thailand were $0.22 - 6.0$ t-C ha-1 y-1

Storm-driven erosion of fine sediment and its subsequent transport and trapping in fringing mangroves, Sawi Bay, Thailand

A field and model study was undertaken in 1998/1999 of the dynamics of water, fine sediment and particulate carbon\ud in the degraded mangrove environment of Sawi Bay. Thailand. The currents were weak (:S 0.3 m s··\\) and principally\ud diurnal tidal. The mean currents were primarily controlled by the prevailing circulation in the adjoining Gulf of\ud Thailand and river runoff. There was very little biological detritus present to act as a coagulant for the fine cohesive\ud sediment in suspension in the mangrove-fringed, muddy coastal waters. The sediment in suspension was mostly fine\ud silt and clay aggregated into small flocs and resuspended by wind waves. This sediment was winnowed from the\ud coastal zone and was advected back in this area by wind waves. The mangroves trap fine sediment and particulate\ud carbon during such events. Riverine inflow of fine sediment in the mangroves was much smaller than the inflow of\ud fine sediment from the sea. The mangroves at Sawi Bay grew on relatively shallow mud overlying a sandy substrate.\ud They infilled with sediment and particulate carbon at a rate equal to, respectively, only 10% and 1% of that for the\ud pristine mangrove environment of Hinchinbrook Channel, Australia. Further, mangroves were inundated only 10%\ud as often at Sawi Bay than at Hinchinbrook, hence the export of nutrients from vegetation detritus was also smaller\ud at Sawi Bay than at Hinchinbrook. Nutrient retention and recycling in mangroves were presumably higher at Sawi\ud Bay than in Hinchinbrook Channel

Distribution of trace elements in sediments and biota of Songkhla Lake, Southern Thailand

The concentrations of Co, Ni, Cu, Zn, Cd, Pb, As, Fe, Mn, and Al were determined in sediments and biota of Songkhla Lake, a shallow coastal lagoon located in southern Thailand. In June 2006, surface sediments were sampled in 44 stations in the three sections of the lake (inner-, middle-, and outer sections). Sediment cores were also sampled in 13 stations in three cross-sections of the lake. In surface sediments, trace and major elements, organic matter, sediment grain size analysis, and sulfides were determined, and in the sediment cores, redox profiles were made. Soil samples were also collected at garbage dumping sites in the vicinity of the lake. In addition, the metal accumulation in two catfish species (Arius maculatus and Osteogeneiosus militaris) and the crustacean (Apseudes sapensis) was also investigated. Trace element concentrations in sediments of Songkhla Lake show that, especially the Outer section of the lake, in particular the sediments at the mouths of the Phawong, U-Taphao, and Samrong Canals are significantly enriched with trace elements due to municipal, agricultural, and industrial discharges entering the lake through the canals. Aluminum-normalized enrichment factors throughout the lake vary from 0.4 to 1.7 for Ni, 0.3 to 3.3 for Cu, 0.2 to 7 for Zn, 0.1 to 14 for As, 1 to 24 for Cd, 0.7 to 6.8 for Pb, and 0.1 to 7.8 for Mn. Correlations between the elements and sediment characteristics show that Cu, Zn, Cd, and Pb are essentially associated with the sulfide fraction; that Ni and Co are predominantly bound to the clay minerals and iron oxy-hydroxides, and that As is principally bound to iron oxy-hydroxides. The accumulation of trace elements between muscle tissue and liver and eggs of A. maculatus and O. militaris is element-specific, but concentrations of trace elements in fish muscle tissue are well within the limits for human consumption

Environmental impacts of diesel fuel on bacteria and phytoplankton in a tropical estuary assessed using in situ mesocosms

10.1007/s10646-004-6373-8Ecotoxicology143397-412ECOT