Profiles of Fecal Porphyrins in River Otters Following the Exxon Valdez Oil Spill

Median levels of Coproporphyrin III (Copro III) in fecal samples of river otters (Lontra canadensis) collected from an oiled area in Prince William Sound, Alaska, USA, during 1990 were significantly higher than in samples collected from the same oiled area during 1996 (p=0.011, one way analysis of variance), a nonoiled reference area in Prince William Sound during 1996 (p=0.002) and a reference area in southeast Alaska during 1998 (p=0.004). An overall test of significance that combined probabilities from the statistical analysis of this porphyrin study with those from other biomarker studies revealed a significant difference in physiological response of river otters between oiled and nonoiled areas of the Sound for 1990 (p < 0.01). We demonstrated that changes in levels of fecal porphyrins may serve as a biomarker that may contribute to a health assessment of wild river otters.     

Arctic Sea‐Ice extent and anomalies, 1953–1984

Abstract

A study is presented of the seasonal and interannual variability of Arctic sea‐ice extent over the 32‐year period 1953–84. The data set used consists of monthly sea‐ice concentration values given on a 1°‐latitude grid and represents a 7‐year extension of the 25‐year data set analysed by Walsh and Johnson (1979). By focussing attention on the variability in seven distinct subregions that circumscribe the polar region, a number of interesting spatial patterns emerge in the regional seasonal cycles and anomalies of ice coverage. For example, the time‐scale of the smoothed anomaly fluctuations varies from a 4–6 year cycle in the western Arctic (e.g. the Beaufort Sea) to a decadal one in the eastern Arctic (e.g. the Barents Sea). Also, in agreement with earlier studies, a significant out‐of‐phase relationship was found between the 25‐month smoothed anomalies in the Beaufort and Chukchi Sea region and the Greenland Sea. It is proposed that this behaviour is related to atmospheric pressure anomalies associated with the see‐saw in winter air temperature between northern Europe and western Greenland. Finally, a particularly large 9‐year ice anomaly in the Greenland Sea that was centred on 1968 appears to have evolved into a substantial 4‐year Labrador Sea anomaly that peaked in 1972. Both of these anomalies coincided with the passage of the “ Great Salinity Anomaly”, which traversed cyclonically around the subpolar gyre in the northern North Atlantic during the period 1968–82.     

The impact of submersed aquatic vegetation on the development of river mouth bars

This work is inspired by the sudden resurgence of the submersed aquatic vegetation (SAV) bed in the Chesapeake Bay (USA). Because the SAV bed occurs at the mouth of the Bay's main tributary (Susquehanna River), it plays a significant role in modulating sediment and nutrient inputs from the Susquehanna to the Bay. Previous model studies on the impact of submersed aquatic vegetation on the development of river mouth bars lacked a complete mechanistic understanding. This study takes advantage of new advances in 3D computational models that include explicit physical-sedimentological feedbacks to obtain this understanding. Specifically, we used Delft3D, a state-of-the-art hydrodynamic model that provides fine-scale computations of three-dimensional flow velocity and bed shear stress, which can be linked to sediment deposition and erosion. Vegetation is modeled using a parameterization of hydraulic roughness that depends on vegetation height, stem density, diameter, and drag coefficient. We evaluate the hydrodynamics, bed shear stresses, and sediment dynamics for different vegetation scenarios under conditions of low and high river discharge. Model runs vary the vegetation height, density, river discharge, and suspended-sediment concentration. Numerical results from the idealized model show that dense SAV on river mouth bars substantially diverts river discharge into adjacent channels and promotes sediment deposition at ridge margins, as well as upstream bar migration. Increasing vegetation height and density forms sandier bars closer to the river mouth and alteration of the bar shape. Thus, this study highlights the important role of SAV in shaping estuarine geomorphology, which is especially relevant for coastal management. © 2019 John Wiley & Sons, Ltd.     

Spreading of Antarctic Bottom Water and its effects on the floor of the Indian Ocean inferred from bottom-water potential temperature,turbidity, and sea-floor photography

Data on bottom-water potential temperature, turbidity and current indications show that in the Southern Ocean west of the Kerguelen Plateau, Antarctic Bottom Water (AABW) of Weddell Sea origin spreads northwards from the Atlantic—Indian Basin in two directions: (1) AABW enters the Agulhas Basin through relatively deep areas in the Mid-Indian Ridge at 20–25°E and possibly at 35°E, and flows northwards into the Mozambique Basin as far as its northern limits; (2) a more easterly spreading path extends from the Atlantic—Indian Basin through the Crozet into the Madagascar, Mascarene, Somali and Arabian Basins. The passage in the western branch of the Indian Ridge for the AABW spreading from the Crozet into the Madagascar Basin appears to be at 29-26°S and 60–64°E.East of the Kerguelen Plateau in the South Indian Basin, the bottom water formed mainly along the Adélie Coast and Ross Sea travels west towards the Kerguelen Plateau and then parallel to it. This water finally flows eastwards hugging the Southeast Indian Ridge. Significant deviations from this general circulation pattern occur due to local topographic effects. Some AABW in the South Indian Basin exits through a passage at 120–125°E in the region of the Australian—Antarctic discordance in the Southeast Indian Ridge and enters the South Australian Basin and subsequently the Wharton Basin. This passage is clearly indicated by the northward extension of a cold, bottom-water tongue as shown by the temperature distribution in the region; the bottom-water effects in the passage are reflected in the high turbidity and current lineations on the sea floor.In the Southern Ocean basins, bottom-water turbidity is generally high, reflecting in part the strong bottom-water activity. The effects of AABW circulation on the sea floor—in the form of well-developed small- or large-scale current ripples and erosional/depositional features, manganese-nodule formations, and unconformities and reworking of sediments observed in cores — are also marked in these basins. Even though the AABW in the Wharton Basin is cold, its spreading effects on the sea floor are minimal in this basin in contrast to the basins west of the Mid-Indian Ridge at comparable latitudes.     

General aspects of the evolutionary history of whales and dolphins

Abstract The Cetacea are the most diverse and highly aquatically adapted group of mammals. Their fossil record extends back at least to the Middle Eocene ( ca 50 Ma), and they will possibly be found earlier, judging by the relatively highly evolved nature of the earliest known whales. The most likely terrestrial ancestors of whales are the mesonychids, primitive hoofed mammals with omnivorous diets. Recently discovered archaeocetes with large, mesonychid-like heads and dentitions and functional hind limbs reconfirm earlier ideas about the mesonychid origin of cetaceans and the amphibious nature of the earliest transitional forms. Fossil cetaceans are relatively abundant and diverse thoughout the world, and are now known from every continent, including Antarctica. Odontocetes evolved echolocation to locate food. Mysticetes developed bulk feeding adaptations. Both undoubtedly evolved from archaeocetes, and the monophyly of Cetacea is the most parsimonious present hypothesis. Chromosomal and molecular evidence has taken an increasingly important role in determining cetacean relationships, but fossils and classical comparative morphological studies remain a necessary and pivotal source of information about cetacean phylogeny.     

A once-molten,coarse-grained,Ca-rich inclusion in Allende

A compact, spheroidal Type B inclusion in Allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures. The combined textural and chemical features of this object cannot be explained by independent vapor-solid condensation of grains in space, followed by random aggregation of these grains into an inclusion. Rather, it probably formed from a once-molten droplet that crystallized in response to radiative cooling from its outer surface. The crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is: melilite-spinel-anorthite-fassaite. This sequence supports the idea that oxygen isotopic heterogeneities in coarse-grained inclusions were formed after complete solidification of these objects by partial exchange with a less¹⁶O-rich gas, and not during or before a melting event.     

Mechanisms of iron oxide transformations in hydrothermal systems

Coexistence of magnetite and hematite in hydrothermal systems has often been used to constrain the redox potential of fluids, assuming that the redox equilibrium is attained among all minerals and aqueous species. However, as temperature decreases, disequilibrium mineral assemblages may occur due to the slow kinetics of reaction involving the minerals and fluids. In this study, we conducted a series of experiments in which hematite or magnetite was reacted with an acidic solution under H₂-rich hydrothermal conditions (T = 100-250 °C, ) to investigate the kinetics of redox and non-redox transformations between hematite and magnetite, and the mechanisms of iron oxide transformation under hydrothermal conditions. The formation of euhedral crystals of hematite in 150 and 200 °C experiments, in which magnetite was used as the starting material, indicates that non-redox transformation of magnetite to hematite occurred within 24 h. The chemical composition of the experimental solutions was controlled by the non-redox transformation between magnetite and hematite throughout the experiments. While solution compositions were controlled by the non-redox transformation in the first 3 days in a 250 °C experiment, reductive dissolution of magnetite became important after 5 days and affected the solution chemistry. At 100 °C, the presence of maghemite was indicated in the first 7 days. Based on these results, equilibrium constants of non-redox transformation between magnetite and hematite and those of non-redox transformation between magnetite and maghemite were calculated. Our results suggest that the redox transformation of hematite to magnetite occurs in the following steps: (1) reductive dissolution of hematite to and (2) non-redox transformation of hematite and to magnetite.     

南京直立人的U/Th和U/Pa年代

中国直立人化石的准确定年对于研究人类演化有着极为重要的意义。1993～1994年在南京汤山葫芦洞发现的两个直立人头盖骨化石和一枚牙化石被称为“南京直立人”。其中1号头盖骨化石之上的方解石钙板的U/Th年龄为53.3_(-1.2)~(+1.5)万年;但考虑到定年的准确性,则为53.3_(-3.0)~(+3.5)万年。其~(231)Pa/~(235)U活度比值为0.998±0.006。这表明“南京直立人”的年代应该大于50万年。与”南京直立人”伴生的动物牙化石U/Th年代为18.5～29.0万年;U/Pa年代为13.7～17.2万年。此外,对于同一颗牙化石,牙釉的年龄小于牙本质的年龄。同一样品的U/Pa年龄也显著小于其U/Th年龄。因此,牙化石的U摄取过程并不符合U早期摄取模式。多数牙化石分析点在~(234)U/~(238)U-~(230)Th/~(238)U图上落在位于U早期摄取和线性摄取模式曲线之间,指示牙化石的U摄取过程很可能介于上述两种模式之间。如果这一假设成立,那么牙化石的U/Th和U/Pa线性摄取模式年龄则为其年代的上限。因为不受U摄取过程~(234)U/~(238)U变化的影响,U/Pa线性摄取模式年龄比U/Th较为可靠。最小的U/Pa线性摄取模式年龄为1Ma,这是”南京直立人”上限年龄的估计。从定年结果看,”南京直立人”可能生活在海洋同位素(MIS)16阶段,但这不是最终结论。