PCB uptake and accumulation by oysters (Crassostrea virginica) exposed via a contaminated algal diet

Reproductively active oysters were fed daily with 0.2 g algal paste containing 0, 0.1, and 1.0 μg polychlorinated biphenyls (PCBs) (1:1:1 mixture of Aroclor 1242, 1254 and 1260) for either 15 or 30 days, and accumulation of PCBs in different organ tissues and eggs assessed. The effects of PCB exposure on lipid content, lipid class and fatty acid composition were also evaluated. PCBs were accumulated by the oysters and transferred to the eggs. PCB accumulation in oysters was dose, time and tissue dependent. Mean PCB contents were 3150, 1970, and 250 ng/g dry wt., respectively, in the visceral mass, gills+mantle and muscle of oysters fed algal paste containing 1.0 μg PCBs for 30 days. The PCBs in the eggs from the same oysters reached 671 ng PCBs/g dry wt. Feeding oysters with PCB-sorbed algal paste for 30 days significantly increased phospholipid and free fatty acid contents in gills+mantle tissues compared to the same tissues in the undosed control.     

Does PCB accumulation affect the lipid metabolism of the reproductively active oyster Crassostrea virginica?

Polychlorinated biphenyls (PCBs) pose a severe ecological risk. They are hydrophobic and are efficiently sequestered in lipid-rich tissues. Lipids function as energy reserves and as membrane components, and are essential for growth and reproductive processes in bivalves. Accumulation of PCBs may affect the mobilization of lipid reserves and membrane lipid composition; thus they may also impair reproductive and developmental processes. To test whether there are any changes in lipid metabolism, the lipid class and fatty acid composition in structural and reserve lipids of visceral mass, gills and mantle, and eggs of reproductively active oysters were examined. Oysters were fed daily with 0.2 g algal paste containing 0, 0.1, or 1.0 μg PCBs for 15 and 30 days. PCBs in the oyster tissues and eggs were also quantified. After 30 days of exposure PCBs were highly accumulated, up to 2635 ng/g in the visceral mass, 1880 ng/g in gill+mantle, and 671 ng/g (dry wt. bases). No significant changes were noted in either lipid class composition or fatty acid composition of structural or reserve lipids from PCB-exposed oyster tissues and eggs.     

Integrating geochronologic and instrumental approaches across the Bengal Basin

Constraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins. The geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem, because the viability of methods can be highly influenced by geomorphic attributes. For example, sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating. Similarly, the rate of sediment transport from source to sink may determine the maturity and/or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating. Here, we explore the viability and quirks of dating and instrumental methods that have been applied in the Bengal Basin, and review the records that they have yielded. This immense, dynamic, and spatially variable system hosts the world's most inhabited delta. Outlining a framework for successful chronologic applications is thus of value to managing water and sediment resources for humans, here and in other populated deltas worldwide. Our review covers radiocarbon dating, luminescence dating, archaeological records and historical maps, short-lived radioisotopes, horizon markers and rod surface elevation tables, geodetic observations, and surface instrumentation. Combined, these tools can be used to reconstruct the history of the Bengal Basin from Late Pleistocene to present day. The growing variety and scope of Bengal Basin geochronology and instrumentation opens doors for research integrating basin processes across spatial and temporal scales. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.     

Remote sensing of spider mite damage in California peach orchards

Remote sensing techniques can decrease pest monitoring costs in orchards. To evaluate the feasibility of detecting spider mite damage in orchards, we measured visible and near infrared reflectance of 1153 leaves and 392 canopies in 11 peach orchards in California. Pairs of significant wavelengths, identified by Partial Least Squares regression, were combined into normalized difference indices. These and 9 previously published indices were evaluated for correlation with mite damage.     

Dynamic subsidence of Eastern Australia during the Cretaceous

During the Early Cretaceous Australia's eastward passage over sinking subducted slabs induced widespread dynamic subsidence and formation of a large epeiric sea in the eastern interior. Despite evidence for convergence between Australia and the paleo-Pacific, the subduction zone location has been poorly constrained. Using coupled plate tectonic–mantle convection models, we test two end-member scenarios, one with subduction directly east of Australia's reconstructed continental margin, and a second with subduction translated ~ 1000 km east, implying the existence of a back-arc basin. Our models incorporate a rheological model for the mantle and lithosphere, plate motions since 140 Ma and evolving plate boundaries. While mantle rheology affects the magnitude of surface vertical motions, timing of uplift and subsidence depends on plate boundary geometries and kinematics. Computations with a proximal subduction zone result in accelerated basin subsidence occurring 20 Myr too early compared with tectonic subsidence calculated from well data. This timing offset is reconciled when subduction is shifted eastward. Comparisons between seismic tomography and model temperature cross-sections, and an absence of subduction zone volcanism in eastern Australia in the Early Cretaceous provide support for the back-arc basin scenario.     

徐家围子断陷构造地质特征研究新进展

在徐家围子断陷深层连片三维地震精细解释的基础上,结合前人的研究成果,系统的刻画了深大断裂的性质、产状和时空分布规律。从区域构造应力场着手,详细剖析了徐家围子断陷的构造地质特征,重新构建了深大断裂体系。依据剖面特征和断陷的地质结构,首次在徐家围子断陷内解释出两条深大走滑断裂带,发现深大走滑断裂控制了营城组火山岩的形成和分布。明确了徐家围子断陷"两凹夹一隆、东西分带、南北分块"构造格局的动态演化过程及其控制因素。详细剖析了断陷期地层的沉积发育过程、后期改造过程以及现今赋存特征。为庆深气田火山岩储层分布规律预测奠定了基础。     

徐家围子断陷深层结构形成与演化的探讨

徐家围子断陷是松辽盆地北部深层最重要的含气断陷。本文根据最新地震和钻井资料综合研究成果,结合前人研究认识,探讨了徐家围子断陷的形成与演化,认为徐家围子断陷在区域构造位置上处于东北地区松辽盆地的北部,处于松辽盆地区域莫霍面隆起的西斜坡上,特定的位置决定了其形成演化的各个阶段受东北地区区域板块构造运动的控制,与松辽盆地的形成与演化具有一定的关系。徐家围子断陷形成与演化可以划分为5个阶段,是太平洋构造域板块间的相互作用和深部热力作用发育演化的结果,这种过程造就了现今南北分块、东西分带、凹隆相间、构造复杂和沉积岩与火山岩并存的地质结构。徐家围子断陷深层现今构造格局受控于近NW向的徐中断裂、近SN向的徐西断裂、近NW向的徐东断裂带和四组近NE向的断裂。本次研究,对以往无法解释的很多地质现象给予了很好的解释,得出了一些崭新的认识,也从宏观上为寻找天然气资源给予了有力指导。     

Biogeographical Patterns of Marine Benthic Macroinvertebrates Along the Atlantic Coast of the Northeastern USA

The biogeography of marine benthic macroinvertebrates of US Atlantic estuaries and inshore coastal areas from Delaware Bay north to Passamaquoddy Bay was studied to compare recent data with historical biogeographic studies, define physical–chemical factors affecting species’ distributions, and provide information for calibrating benthic indices of environmental condition. Five years (2000–2004) of data from 614 non-polluted, soft-bottom stations from the National Coastal Assessment were analyzed. Multi-dimensional scaling done on Bray-Curtis similarity matrices of species’ relative abundance (547 species) suggested seven subregions: two based on salinity (oligohaline, mesohaline) and five based on latitude. Species’ distribution patterns for stations with salinities ≥18 (n = 558) were strongly influenced by latitude; Cape Cod was a clear faunal transition zone (R = 0.92, p < 0.001). Conversely, for stations with salinities <18 (n = 56), salinity was the more important factor. An ordination of abiotic variables (temperature, salinity, sediment percent silt-clay, depth) correlated well with the ordination of species’ relative abundance data (R = 0.77, p < 0.001). The first split of a multivariate regression tree was by a summer bottom temperature of 20°C at Cape Cod. Salinity and percent silt-clay led to further splits. These results support the existence of Virginian and Transhatteran biogeographic provinces. They constitute a baseline for addressing broad-scale and long-term issues such as global climate change, species invasions, and conservation planning.