Increase in anthropogenic mercury in marginal sea sediments of the Northwest Pacific Ocean.

Over the past century, the addition of anthropogenic mercury (Hg) to vast areas of North Pacific marginal seas adjacent to the northeast Asian continent has tripled. Analysis of sediment cores showed that the rate of Hg addition (Hg flux) was greatest in the East China and Yellow Seas (9.1 μg m yr) in the vicinity of China (the source continent), but was small in the Bering and western Arctic Ocean (Chukchi Sea) (0.

Widespread Anthropogenic Nitrogen in Northwestern Pacific Ocean Sediment.

Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower δN values (expressed as δN = [N:N/N:N - 1] × 1000‰; the sediment N:N ratio relative to the air nitrogen N:N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher δN values (2-3‰ higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment δN increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (N) resulting from fossil fuel combustion and fertilizer use.

Effects of temperature and nutrients on changes in genetic diversity of bacterioplankton communities in a semi-closed bay, South Korea.

Bacterioplankton communities in a semi-closed bay (Jangmok Bay, South Korea) were analysed using a 16S rDNA multiplex 454 pyrosequencing approach. Diversity and operational taxonomic units of bacterioplankton communities in the Jangmok Bay are highest in cold water seasons and lowest in warm water ones. During cold seasons, α-proteobacteria respond rapidly to pulses of the concentration of inorganic nutrients, while γ-proteobacteria during warm water seasons are the most active type of bacterioplankton resent in the prevailing conditions, which include high dissolved organic carbon, chemical oxygen demand and primary production.

Can the algicidal material Ca-aminoclay be harmful when applied to a natural ecosystem? An assessment using microcosms.

We assessed the ability of an artificial clay (Ca-aminoclay) to suppress harmful algal bloom species (HABs) such as Cochlodinium polykrikoides and Chattonella marina and investigated the ecological responses in the closed and open microcosm systems. The Ca-aminoclay induced rapidly and selectively cell lysis in the HABs. However, applying Ca-aminoclay could cause adverse impacts in terms of biological and environmental changes.

Source- and region-specific distribution of polycyclic aromatic hydrocarbons in sediments from Jinhae Bay, Korea.

This study surveyed polycyclic aromatic hydrocarbons (PAHs) at 80 sites in sediment from Jinhae Bay, which consists of Masan Bay (MSB), Haengam Bay (HAB), Bay Proper (JBP), Wonmoon Bay (WMB), and Gohyun Bay (GHB). Levels of the EPA 16 priority PAHs, 5 groups of alkylated PAH homologues and 2 biogenic PAHs were determined. Total PAHs (sum of all target PAHs) ranged from 37.

Toxicological impact assessment of heavy metal contamination on macrobenthic communities in southern coastal sediments of Korea.

In the heavily industrialized Masan Bay of southern coast, Korea, the potential harmful effects of heavy metals (Cd, Co, Cu, Ni, Pb, Sn, Zn, and Hg) were evaluated in terms of the pollution load index (PLI) and ecological risk assessment index (ERI) methods, and the results obtained were considered alongside the health of the macrobenthic fauna communities. The results revealed that the bay sediments, especially in the inner bay and the outfall area of a sewage treatment plant, are exposed to moderate to serious levels of metal pollution. Hg and Cd contributed the most to the potential toxicity response indices in sediments recently deposited in the bay.

Historical record of metal accumulation and lead source in the southeastern coastal region of Korea.

Concentrations of heavy metals and Pb isotopes were measured in the 1-M HCl leaching fraction of core sediments spanning the last 400 years. This sedimentary record of pollution history in metal concentrations shows a good correlation with the increases in industrialization, urbanization, and energy consumption since 1901s. Notably, the Pb concentration and the (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios were constant before the 1910s (16.

Sedimentary records of metal contamination and eutrophication in Jinhae-Masan Bay, Korea.

Historical environmental pollution in a semi-enclosed coastal bay was investigated using high-resolution sedimentary records for C(org), N(tot), CaCO(3,) δ(13)C, and δ(15)N signatures, and trace metals. A temporal increase in organic matter might have been attributable to enhanced primary marine productivity, presumably caused by increased anthropogenic nutrient inputs in the semi-enclosed, eutrophic system. Metal accumulation occurred in three stages: a preindustrial stage before the 1930s with natural concentrations of metals, an industrialization stage (1940s-1970s) with the highest concentrations, and a postindustrial stage (post 1970s) with stable or decreasing concentrations.