Indicators of sediment and biotic mercury contamination in a southern New England estuary

Total mercury (Hg) and methylmercury (MeHg) were analyzed in near surface sediments (0-2 cm) and biota (zooplankton, macro-invertebrates, finfish) collected from Narragansett Bay (Rhode Island/Massachusetts, USA) and adjacent embayments and tidal rivers. Spatial patterns in sediment contamination were governed by the high affinity of Hg for total organic carbon (TOC). Sediment MeHg and percent MeHg were also inversely related to summer bottom water dissolved oxygen (DO) concentrations, presumably due to the increased activity of methylating bacteria. For biota, Hg accumulation was influenced by inter-specific habitat preferences and trophic structure, and sediments with high TOC and percent silt-clay composition limited mercury bioavailability. Moreover, hypoxic bottom water limited Hg bioaccumulation, which is possibly mediated by a reduction in biotic foraging, and thus, dietary uptake of mercury. Finally, most biota demonstrated a significant positive relationship between tissue and TOC-normalized sediment Hg, but relationships were much weaker or absent for sediment MeHg. These results have important implications for the utility of estuarine biota as subjects for mercury monitoring programs.     

Are the eastern and western basins of the English Channel two separate ecosystems?

The English Channel is part of the "Greater North Sea" sub-region in the Marine Strategy Framework Directive. However, the Channel is characterized by hydrologic, oceanographic and biogeographic features that support its division into two main entities: the western basin and the eastern basin. This paper summarizes the Channel's main natural features and principal human activities to examine the similarities and differences between both basins. The differences between the basins support an ecosystem-based management approach at the combined basin scale, rather than the present approach of separating the France and UK sides.     

Phytoplankton community composition in nearshore coastal waters of Louisiana

Phytoplankton community compositions within near-shore coastal and estuarine waters of Louisiana were characterized by group diversity, evenness, relative abundance and biovolume. Sixty-six taxa were identified in addition to eight potentially harmful algal genera including Gymnodinium sp. Phytoplankton group diversity was lowest at Vermillion Bay in February 2008, but otherwise ranged between 2.16 and 3.40. Phytoplankton evenness was also lowest at Vermillion Bay in February 2008, but otherwise ranged between 0.54 and 0.77. Dissolved oxygen increased with increased biovolume (R2 = 0.85, p < 0.001) and biovolume decreased with increased light attenuation (R2 = 0.34, p = 0.007), which supported the importance of light in regulating oxygen dynamics. Diatoms were dominant in relative abundance and biovolume at almost all stations and all cruises. Brunt-V?is?l? frequency was used as a measure of water column stratification and was negatively correlated (p = 0.02) to diatom relative percent total abundance.     

黑龙江省闪电活动特征及其与地面相对湿度的响应关系

利用2006-2017年黑龙江省闪电定位资料和日平均地面相对湿度资料,采用数理统计、Pearson相关分析、GIS空间分析技术,研究了闪电密度和强度对地面相对湿度（R_H）的响应关系。结果表明：地面R_H过小或过大都不利于闪电活动产生;当R_H < 25%时,几乎无闪电发生,当R_H < 77%时,R_H增加有利于闪电活动发生,当R_H>79%时,随着R_H增加,闪电活动减少;当R_H < 77%时,闪电密度与之呈正相关,闪电强度与之呈负相关;当R_H>79%时,闪电密度与之呈负相关,闪电强度与之呈正相关;地面R_H的临界值域约为77%-79%;70%≤ R_H ≤ 90%区间为闪电易发湿度区间,在闪电密度与湿度相关度高的区域,闪电更趋于集中发生在闪电易发湿度区间。     

Glucuronidation in the polar bear (Ursus maritimus)

Polar bears bioaccumulate lipophilic pollutants, including polychlorinated biphenyls (PCBs), into their bodies from their exclusive diet of marine organisms. Hydroxylated PCB metabolites (OH-PCBs) have been found in plasma, presumably due to CYP-dependent biotransformation of PCBs in liver. Little is known about the phase 2 metabolism of hydroxylated xenobiotics in polar bears. The objective of this study was to examine UDP-glucuronosyltransferase (UGT) activity with OH-PCBs and a hydroxylated polycyclic aromatic hydrocarbon, 3-hydroxy-benzo(a)pyrene (3-OH-BaP), in polar bear liver. Samples of frozen polar bear liver were used to prepare microsomes. UGT activity with 3-OH-BaP in Brij-treated microsomes, measured by a fluorescence assay, was readily measurable with protein concentrations in assay tubes of up to 10 g/ml, but dropped off very sharply at higher protein concentrations. The apparent Km for 3-OH-BaP was 1.71 +/- 0.04 microM, and Vmax 1.26 +/- 0.16 nmol/min/mg protein (mean +/- SD, n=3). UGT activities with a model tetrachloro-OH-PCB (4'-OH-CB72) and a model hexachloro-OH-PCB (4'-OH-CB159) were assayed with [14-C]-UDPGA and separation of the [14-C]-glucuronide by ion-pair extraction and thin-layer chromatography. [14-C]-glucuronide conjugates were readily formed by polar bear liver microsomes in the absence of added substrate, apparently from contaminants present in liver. This phenomenon was not observed using hepatic microsomes from laboratory-held catfish. Glucuronidation efficiency was much higher with 4'-OH-CB72 (Km 7.3 microM; Vmax 1.55 nmol/min/mg) than 4'-OH-CB159 (Km 16.1 microM; Vmax 0.46 nmol/min/mg). The identities of the aglycones present in polar bear liver are not known, but could include OH-PCBs or hydroxylated metabolites of other persistent organic pollutants. This study demonstrates that UGT with high activity for 3-OH-BaP and other substrates is present in polar bear liver.     

现代腕足动物壳体的δ^18O和δ^13C值

现代腕足动物壳体的δ~（１８）Ｏ和δ~（１３）Ｃ值Ｊ。Ｃ。Ｓｃｏｔｔ等在过去的３４年里，许多科技工作者利用古代腕足动物壳体的δ１８值作为古海水δ１８Ｏ值或温度的长期变化的指示物。最近，腕足动物壳体的δ１８Ｏ值被用来计算古海水的温度、密度和盐度，以了解古...