Methylmercury production in sediments of Chesapeake Bay and the mid-Atlantic continental margin

Methylmercury (MeHg) concentration and production rates were studied in bottom sediments along the mainstem of Chesapeake Bay and on the adjoining continental shelf and slope. Our objectives were to 1) observe spatial and temporal changes in total mercury (HgT) and MeHg concentrations in the mid-Atlantic coastal region, 2) investigate biogeochemical factors that affect MeHg production, and 3) examine the potential of these sediments as sources of MeHg to coastal and open waters. Estuarine, shelf and slope sediments contained on average 0.5 to 1.5% Hg as MeHg (% MeHg), which increased significantly with salinity across our study site, with weak seasonal trends. Methylation rate constants (k_meth), estimated using enriched stable mercury isotope spikes to intact cores, showed a similar, but weaker, salinity trend, but strong seasonality, and was highly correlated with % MeHg. Together, these patterns suggest that some fraction of MeHg is preserved thru seasons, as found by others [Orihel, D.M., Paterson, M.J., Blanchfield, P.J., Bodaly, R.A., Gilmour, C.C., Hintelmann, H., 2008. Temporal changes in the distribution, methylation, and bioaccumulation of newly deposited mercury in an aquatic ecosystem. Environmental Pollution 154, 77] Similar to other ecosystems, methylation was most favored in sediment depth horizons where sulfate was available, but sulfide concentrations were low (between 0.1 and 10 μM). MeHg production was maximal at the sediment surface in the organic sediments of the upper and mid Bay where oxygen penetration was small, but was found at increasingly deeper depths, and across a wider vertical range, as salinity increased, where oxygen penetration was deeper. Vertical trends in MeHg production mirrored the deeper, vertically expanded redox boundary layers in these offshore sediments. The organic content of the sediments had a strong impact on the sediment:water partitioning of Hg, and therefore, on methylation rates. However, the HgT distribution coefficient (K_D) normalized to organic matter varied by more than an order of magnitude across the study area, suggesting an important role of organic matter quality in Hg sequestration. We hypothesize that the lower sulfur content organic matter of shelf and slope sediments has a lower binding capacity for Hg resulting in higher MeHg production, relative to sediments in the estuary. Substantially higher MeHg concentrations in pore water relative to the water column indicate all sites are sources of MeHg to the water column throughout the seasons studied. Calculated diffusional fluxes for MeHg averaged  1 pmol m^− 2 day^− 1. It is likely that the total MeHg flux in sediments of the lower Bay and continental margin are significantly higher than their estimated diffusive fluxes due to enhanced MeHg mobilization by biological and/or physical processes. Our flux estimates across the full salinity gradient of Chesapeake Bay and its adjacent slope and shelf strongly suggest that the flux from coastal sediments is of the same order as other sources and contributes substantially to the coastal MeHg budget.     

渤海湾水生态环境现状和海岸带开发对其的影响研究

由于沿海地区经济迅速发展,越来越多的陆源污水排入渤海湾,渤海湾生态环境系统承受着巨大的压力。本文建立了渤海湾生态环境的多级指标体系,并根据2003年至2005年多次渤海湾监测资料对其现状进行了分析;然后进一步研究了由于围海造地、海水淡化等开发工程引起的近岸海域水动力条件和污染物输移的变化。结果表明,陆源污染物大量排放、沿海开发活动加剧是影响渤海湾水生态环境的主要原因。沿海围垦不仅导致潮通量减少,潮流作用减弱,而且影响近岸海域污染物的输移和分布。海水淡化高浓度盐水的排放也对近岸海域的水生态环境造成很大的影响。     

东山湾潮流动力特征研究

东山湾是福建重要的天然良港．根据2008年8月的3个潮次11个测站实测潮流资料结合历史调查资料分析东山湾的潮流性质、运动形式、涨落潮流特性、余流等特征．结果表明,东山湾主要属于往复式的规则半日潮流,潮流作用较强,其口门处和湾内水道上的实测最大流速一般大于100cm／s．持续时间较长的风对东山湾的余流较大的影响,大潮期间湾内存在明显的反时针的水平余环流系统．     

东北季风期海南岛三亚湾初级生产力分布特征及其影响因素

根据2006年10月和2007年1月的监测资料,对三亚湾在东北季风初始期和盛行期初级生产力的分布特征及其受水体环境的影响因素进行了分析。三亚湾秋、冬季表层潜在初级生产力平均值分别为6.81mgC·m-3·h-1和7.47mgC·m-3·h-1;水柱初级生产力平均值分别为504.96mgC·m-2·d-1和495.33mgC·m-2·d-1。东北季风期间,三亚湾水体垂直混合作用加强,层化现象减弱,水动力过程和营养盐等环境因子是该海湾初级生产力分布特征和季节变化的重要调控因素;其中冬季较高的DIN分布对表层初级生产力有潜在促进作用,而水体扰动增强、真光层深度下降则导致水柱初级生产力低于秋季。三亚河口近岸水域秋、冬季均为营养盐、叶绿素a及初级生产力的高值区,其中表层潜在初级生产力在秋季和冬季分别达到了45.80mgC·m-3·h-1和39.27mgC·m-3·h-1,表明调查期间三亚河营养盐输入对近岸水体浮游植物初级生产过程的显著影响。     

莱州湾南岸海水入侵现状评价

根据莱州湾南岸海水入侵区地下水水质特点,将海水入侵等级划分为4级。同时,选取Cl^-,矿化度,SO4^2-,rHCO3^-/rCl^-,K^-等指标作为评价因子,并分别确定了这5项指标的等级划分范围。然后,运用模糊数学的综合评判方法,对研究区内海水入侵现状做出评价。     

2005/2006年度莱州湾东部的海冰灾害及其影响

莱州湾是水深较浅的半封闭海湾,与外海海水的交换缓慢,受黄河等十几条入海河流汇入的淡水影响使海水的盐度较低.受寒潮影响莱州湾内海冰灾害发生频繁.莱州湾的海冰灾害分5个冰情等级.在冬季气温偏高的年份,莱州湾内形成Ⅰ、Ⅱ级海冰,沿岸一般没有固定冰形成;一般年份形成Ⅲ级海冰,西岸和南岸冰情较严重,有固定冰形成;在冬季气温偏低的年份,形成Ⅳ级或Ⅴ级海冰,南岸、西岸的固定冰宽度较大,有时整个莱州湾海面都分布流冰.2005年末～2006年初在莱州湾东岸形成了一次较严重的海冰灾害,莱州市近海海湾扇贝养殖的经济损失达400万元以上.为减轻未来海冰灾害带来的损失提出了加强海冰灾害的监测和预报技术研究,严格管理近海养殖生产作业,莱州湾沿岸地方政府应制定<海冰灾害应急预案>,建设和完善海冰灾害应急防御体系等防御海冰灾害的对策.     

Accumulation of petroleum hydrocarbons and heavy metals in clams （Ruditapes philippinarum） in Jiaozhou Bay, China

Accumulation and distributions of aliphatic and polyaromatic hydrocarbons (PAHs) and heavy metals were measured in tissues of the clam Ruditapes philippinarum collected from 5 sites in Jiaozhou Bay, Qingdao, China. The concentrations of total aliphatic hydrocarbon and PAHs ranged from 570 to 2 574 ng/gdw (gram dry weight) and from 276 to 939 ng/gdw, in the most and least polluted sites, respectively. The bio-accumulation of hydrocarbons and PAHs in the clams appeared to be selective. Aliphatic hydrocarbons were predominantly represented by short chain (<nC₂₃) n-alkanes, suggesting that petroleum hydrocarbons were likely the major contamination source. The selective uptake of 3 and 4 ring PAHs, such as naphthalene, fluorene, phenanthrene, fluoranthene and pyrene, by the clams was probably related to the physiological and bio-kinetic processes that were energetically favorable for uptake of compounds with fewer rings. Accumulation of the metals Cd, Cu, Zn, Pb, Cr, Hg, and As in the clam tissues also showed high variability, ranging from 0.043 to 87 μg/gdw. Among the 7 detected metals, Zn, Cd, Cu, and As had a particularly high potential of accumulation in R. philippinarum. In general, a positive correlation was found between the tissue concentrations and sediment concentrations of hydrocarbons and of some metals. Our study suggests that moderate contamination with polyaromatic hydrocarbons, and low to moderate contamination with metals, currently exists for clam R. philippinarum in Jiaozhou Bay, in comparison with other regional studies. A long-term monitoring program is certainly needed for assessment of the potential ecological influence and toxicity of these contaminants of R. philippinarum in Jiaozhou Bay.     

The impact of physical processes on pollutant transport in Hangzhou Bay

A Lagrangian tracer model is set up for Hangzhou Bay based on Coupled Hydrodynamical Ecological model for Regional Shelf Sea (COHERENS). The study area is divided into eight subdomains to identify the dominant physical processes, and the studied periods are March (the dry season) and July (the wet season). The model performance has been first verified by sea-surface elevation and tidal current observations at several stations. Eight tracer experiments are designed and Lagrangian particle tracking is simulated to examine the impact of physical processes (tide, wind and river runoff) on the transport of passive tracer released within the surface layer. Numerical simulations and analysis indicate that: (1) wind does not change the tracer distribution after 30 days except for those released from the south area of the bay during the wet season; (2) the tide and the Qiantang River runoff are important for particle transport in the head area of the bay; (3) the Changjiang River runoff affects the tracer transport at the mouth of the bay, and its impact is smaller in the dry season than in the wet season. Supported by the Natural Science Foundation of China (No.40576080); National High Technology Research and Development Program of China (863 Program, No. 2007AA12Z182)     

Thickness distribution and extent of sea ice and snow in Prydz Bay and surrounding waters observed in 2012/2013 austral summer

Three ship-based observational campaigns were conducted to survey sea ice and snow in Prydz Bay and the surrounding waters(64.40°S–69.40°S, 76.11°E–81.29°E) from 28 November 2012 to 3 February 2013. In this paper, we present the sea ice extent and its variation, and the ice and snow thickness distributions and their variations with time in the observed zone. In the pack ice zone, the southern edge of the pack ice changed little, whereas the northern edge retreated significantly during the two earlier observation periods. Compared with the pack ice, the fast ice exhibited a significantly slower variation in extent with its northernmost edge retreating southwards by 6.7 km at a rate of 0.37 km?d-1. Generally, ice showed an increment in thickness with increasing latitude from the end of November to the middle of December. Ice and snow thickness followed an approximate normal distribution during the two earlier observations(79.7±28.9 cm, 79.1±19.1 cm for ice thickness, and 11.6±6.1 cm, 9.6±3.4 cm for snow thickness, respectively), and the distribution tended to be more concentrated in mid-December than in late November. The expected value of ice thickness decreased by 0.6 cm, whereas that of snow thickness decreased by 2 cm from 28 November to 18 December 2012. Ice thickness distribution showed no obvious regularity between 31 January and 3 February, 2013.     

Seasonal change in body length of important small copepods and relationship with environmental factors in Jiaozhou Bay,China

Differences among species in prosome length and in species’ response to environmental factors do exist. Therefore, it is useful to examine prosome length for different copepod species in variable environments. Seasonal variations in prosome length of four small copepods and their copepodite stages in the Jiaozhou Bay were compared and the relative influence of temperature, salinity, and chlorophyll concentration were examined. Two peaks were found in the mean prosome length of Paracalanus parvus (in early winter and May). For Acartia bifilosa, the maximum values of all copepodites occurred mainly from February to April, and decreased to the bottom in July. Prosome length of Acartia pacifica peaked when it first appeared in June, then reached to the minimum in July. Parvocalanus crassirostris only appeared from late summer to autumn and the mean prosome length showed no clear changes. Correlations of adult prosome length with environmental factors were evaluated. For the four species, temperature was negatively correlated to prosome length except for P. crassirostris. But the different species varied markedly in their responds to temperature. A. bifilosa showed a more definite trend of size variation with temperature than P. parvus and A. pacifica. Correlations of prosome length with salinity were significantly positive for almost all the small copepods. The relationship between chlorophyll concentration and prosome length was complicated for these copepods, but for P. parvus, chlorophyll concentration was also an important affecting factor. Furthermore, investigation needs to be done on food quality for some copepod. These results are essential to estimate the biomass and the production, and to understand these small copepods’ population dynamics in this human-affected bay.