Trophic cascades and future harmful algal blooms within ice-free Arctic Seas north of Bering Strait: A simulation analysis

Within larger ice-free regions of the western Arctic Seas, subject to ongoing trophic cascades induced by past overfishing, as well as to possible future eutrophication of the drainage basins of the Yukon and Mackenzie Rivers, prior very toxic harmful algal blooms (HABs) – first associated with ∼100 human deaths near Sitka, Alaska in 1799 – may soon expand. Blooms of calcareous coccolithophores in the Bering Sea during 1997–1998 were non-toxic harbingers of the subsequent increments of other non-siliceous phytoplankton. But, now saxitoxic dinoflagellates, e.g. Alexandrium tamarense, were instead found by us within the adjacent downstream Chukchi Sea during SBI cruises of 2002 and 2003. A previous complex, coupled biophysical model had been validated earlier by ship-board observations from the Chukchi/Beaufort Seas during the summer of 2002. With inclusion of phosphorus as another chemical state variable to modulate additional competition by recently observed nitrogen-fixers, we now explore here the possible consequences of altered composition of dominant phytoplankton functional groups [diatoms, microflagellates, prymnesiophyte Phaeocystis colonies, coccolithophores, diazotrophs, and dinoflagellates] in relation to increases of the toxic A. tamarense, responding to relaxation of grazing pressure by herbivores north of Bering Strait as part of a continuing trophic cascade. Model formulation was guided by validation observations obtained during 2002–2004 from: cruises of the SBI, CHINARE, and CASES programs; moored arrays in Bering Strait; other RUSALCA cruises around Wrangel Island; and SBI helicopter surveys of the shelf-break regions of the Arctic basin. Our year-long model scenarios during 2002–2003 indicate that post bloom silica-limitation of diatoms, after smaller simulated spring grazing losses, led to subsequent competitive advantages in summer for the coccolithophores, dinoflagellates, and diazotrophs. Immediate top-down control is exerted by imposed grazing pressures of the model’s herbivores and bottom-up control is also effected by light-, nitrate-, ammonium-, silicate-, and phosphate-modulated competition among the six functional groups of the simulated phytoplankton community. Similar to the history of the southern North Sea adjacent to the Rhine River, possible farming of northwestern Alaska and Canada, in conjunction with other human activities of ice retreat and overfishing, may lead to future exacerbations of poisonous phytoplankton. These potential killers include both toxic dinoflagellate and diazotroph HABs, deadly to terrestrial and marine mammals, as well as those of prymnesiophytes, some of which have already foamed beaches, while others have killed fishes of European waters.     

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation

Epidote-bearing porphyritic dikes (whole rock analysis: SiO₂?=?55–65 wt. %, MgO <2.1 wt. %, K₂O <2.5 wt. %, Al₂O₃ >17 wt. %, Na₂O + K₂O?=?5.7–9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388?±?2 Ma and 389?±?6 Ma. The porphyries contain phenocrysts of magmatic epidote (Ps?=?17–25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al₂O₃?=?12–16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than logfo₂ = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK?=?0.7–1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of ⁸⁶Sr/⁸⁷Sr_i?=?0.709–0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.     

Mineralogy, geochemistry and stratigraphy of the Maslovsky Pt–Cu–Ni sulfide deposit, Noril’sk Region, Russia

We report new data on the stratigraphy, mineralogy and geochemistry of the rocks and ores of the Maslovsky Pt–Cu–Ni sulfide deposit which is thought to be the southwestern extension of the Noril’sk 1 intrusion. Variations in the Ta/Nb ratio of the gabbro-dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses, which gave rise to the Northern and Southern Maslovsky intrusions that together host the Maslovsky deposit. The Northern intrusion is located inside the Tungusska sandstones and basalt of the Ivakinsky Formation. The Southern intrusion cuts through all of the lower units of the Siberian Trap tuff-lavas, including the Lower Nadezhdinsky Formation; demonstrating that the ore-bearing intrusions of the Noril’sk Complex post-date that unit. Rocks in both intrusions have low TiO₂ and elevated MgO contents (average mean TiO₂ <1 and MgO?=?12?wt.%) that are more primitive than the lavas of the Upper Formations of the Siberian Traps which suggests that the ore-bearing intrusions result from a separate magmatic event. Unusually high concentrations of both HREE (Dy+Yb+Er+Lu) and Y (up to 1.2 and 2.1?ppm, respectively) occur in olivines (Fo_79.5 and 0.25% NiO) from picritic and taxitic gabbro-dolerites with disseminated sulfide mineralization. Thus accumulation of HREE, Y and Ni in the melts is correlated with the mineral potential of the intrusions. The TiO₂ concentration in pyroxene has a strong negative correlation with the Mg# of both host mineral and Mg# of host rock. Sulfides from the Northern Maslovsky intrusion are predominantly chalcopyrite–pyrrhotite–pentlandite with subordinate and minor amounts of cubanite, bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals (Au, Ag and Pd), Sn–Pd–Pt–Bi–Pb compounds and Fe–Pt alloys. Sulfides from the Southern Maslovsky intrusion have δ ³⁴S?=?5–6‰ up to 10.8‰ in two samples whereas the country rock basalt have δ ³⁴S?=?3–4‰, implying there was no in situ assimilation of surrounding rocks by magmas.     

News Items

The process of reading a topographic map requires users to recognize and learn the cartographic symbols of the key (or legend) while interpreting the territory as depicted on the map at a given level of abstraction (the form and nature of features, their saliency and relationships). We present the results of an empirical user study that aims to identify and assess the main graphical characteristics that are used by map users to recognize the design principles which constitute the topographic mapping style adopted by IGN (Institut National de l'Information Géographique et Forestière), France. Our results suggest that 91% of the participants were able to recognize an IGN-France topographic map amongst other topographic map products. We also determine which graphical characteristics play a role in the recognition of this cartographic style, either by visual memory or by visual perception, and identify the representation of relief, including contour lines and shaded relief, as one of the major graphical characteristics of the topographic mapping style of IGN-France. Moreover, the participants of our study considered the representation of touristic POI (points of interest), toponymy, typography, the main roads network, the individual buildings and the forests, to be essential for stylistic recognition.     

GEOECOLOGICAL ANALYSIS OF ENVIRONMENTALLY DISTURBED AREAS BASED ON CARTOGRAPHIC MODELING: THE EXAMPLE OF AREAS OF MINERAL DEVELOPMENT

The authors describe the results of an extensive geomorphologic mapping program for the Kura-Araks Lowland of Azerbaijan, designed to increase the level of background information available for the rational planning and operation of irrigation systems. A particular focus is placed upon the identification and depiction of landforms of the Lowland exerting an influence on hydrogeologic conditions, the ground water regime, and on crop cultivation patterns. Translated by Edward Torrey, Alexandria, VA 22308 from: Geografiya i prirodnyye resursy, 1995, No. 4, pp. 169-171.     

Complex analysis of the damage caused by geocryologic processes (as exemplified by effects on the Chara-China Railway track, Transbaikal region)

The report presents an analysis of a unique data set demonstrating the influence of geocryological processes on the 75-km Chara-China Railway track (northern Transbaikal region). The originality of these investigations lies in the study of the influence of natural processes on the road in the absence of any repair works or protective and compensating measures for a long period of time (1998~2014). These conditions allowed assessment of the actual damage to the railroad.