СОСТОЯНИЕ ЭКОСИСТЕМ ВОСТОЧНОГО И ЗАПАДНОГО БАССЕЙНОВ САКСКОГО ОЗЕРА (РЕСПУБЛИКА КРЫМ)

Eighty-seven seismic refraction profiles have been obtained to define the geologic structure in the upper crust associated with the midcontinent gravity high in Minnesota and Wisconsin. The seismic measurements were taken across a fixed spread of seven geophones from distances up to 13 km. A structural section was prepared for each profile by interpretation of the travel-time graph, and the individual sections were compiled onto regional cross sections. Measured seismic velocities in bedrock fall in the 2.5–7.1 km/sec range. Observed velocities can be assigned to seven categories corresponding to Paleozoic, upper, middle, and lower Upper Keweenawan strata, Middle Keweenawan volcanics, pre-Keweenawan felsic-to-intermediate intrusive rocks, and pre-Keweenawan mafic intrusive rocks. These groups display good continuity through the area and suggest the lithologic equivalence of rock bodies between geologic provinces. The St. Croix horst and its flanking basins underlie the midcontinent gravity high and its parallel gravity lows north of Minneapolis. Minimum throw along the western and eastern boundary fault zones reaches about 3.0 and 2.0 km. Sedimentary rocks in the eastern basin reach a thickness of at least 2.6 km. A complex horst-like structure also underlies the midcontinent gravity high in southern Minnesota; an uplifted basaltic body is bordered by sedimentary basins having strata about 3.0 km thick. Middle Keweenawan basalts are present locally in the eastern and western basins underlying the Upper Keweenawan strata. Rocks probably lithologically equivalent to the Oronto group are rare in the western basin, common in small basins on the St. Croix horst, and abundant in the eastern basin. Rocks probably lithologically equivalent to the Bayfield group are extensive in the western and eastern basins, but they have not been found on the St. Croix horst. The Bayfield group seems to be several kilometers thick across Douglas County north of the Douglas fault, and it does not appear to increase in thickness under the Bayfield peninsula.

Primary production values in Lake Ontario were low in winter, reached a maximum in midspring, declined during summer, and slightly increased in fall. Rate of increase of production for inshore waters (< 20 m depth) was greater especially in spring and early summer with a greater maximum reached earlier than in offshore waters. Assimilation numbers, mgC fixed/mg chlorophyll a per hour, in Lake Ontario were fairly constant over the lake with a yearly range of 1.2–1.6. Primary production showed a linear relationship to chlorophyll a concentration, as also occurred in Lake Erie.Lake Erie primary production varied in its three basins. Seasonally, in the Eastern Basin, production was highest in spring with a midsummer decline, and small peaks in fall. The Western Basin had a maximum in midsummer whereas the Central Basin had peaks in late summer and early fall. Assimilation numbers were highest in the Western Basin (up to 3.5 mgC/mg chlorophyll a per hour) and lowest in the mid-Central Basin and Eastern Basin with values of approximately 1.4 mgC/mg chlorophyll a per hour. A definite westerly increase of assimilation number was observed.Up to early summer, the two lakes were fairly equal in surface production but integral photosynthesis, mgC/m2 per hour was higher in Lake Ontario than in Lake Erie. The same was valid in November and December. In summer, Lake Erie was higher in production on both a mgC/m3 per hour and mgC/m2 per hour basis. For the period, April–December, Lake Ontario's total estimated yield was 170 gC/m2, whereas for Lake Erie values of 160, 210, and 310 gC/m2 were found for the Eastern, Central, and Western basins, respectively.

Using daily precipitation records from 151 stations, the Mann‐Kendall nonparametric test, and the rotated empirical orthogonal function, this study examined trends in precipitation and precipitation extremes and underlying mechanisms in the U.S. Great Basin during 1951–2013. The results indicate that annual total precipitation, 1 day and 5 day maximum precipitation, extreme precipitation days over the 95th and 99th percentiles trended upward during 1951–2013. Spatially, stations experienced significant positive trends in six indices are mostly distributed in the eastern basin, while those experienced significant negative trends are a few and situated in the western basin. Four distinct modes characterized by different patterns of annual precipitation variations were identified. They are the northeastern, southern, midwestern, and midnorthern modes. In addition, we found that the effects of El Niño–Southern Oscillation and Pacific Decadal Oscillation on precipitation was low in the basin. The intensifying high‐pressure system over the western North Pacific in winter and the increasing water vapor and air temperature of the atmosphere over the basin in winter and spring were mainly responsible for the upward trends in six indices during 1951–2013. Nevertheless, the topography regulates the effects of synoptic conditions on precipitation, contributing to the “east‐west” contrast in station distribution between those experienced negative and positive trends. Overall, precipitation and precipitation extremes increased significantly in the eastern and northern basin while increases were not significant in the western and southern basin. This information has important implications for not only predicting future precipitation changes but also mitigating precipitation‐change‐associated risks on ecosystems and human society in the Great Basin.

We measured prokaryotic production and respiration in the major water masses of the North Atlantic down to a depth of 4,000 m by following the progression of the two branches of North Atlantic Deep Water (NADW) in the oceanic conveyor belt. Prokaryotic abundance decreased exponentially with depth from 3 to 0.4 3 105 cells mL21 in the eastern basin and from 3.6 to 0.3 3 105 cells mL21 in the western basin. Prokaryotic production measured via 3H-leucine incorporation showed a similar pattern to that of prokaryotic abundance and decreased with depth from 9.2 to 1.1 mmol C m23 d21 in the eastern and from 20.6 to 1.2 mmol C m23 d21 in the western basin. Prokaryo
\ntic respiration, measured via oxygen consumption, ranged from about 300 to 60 mmol C m23 d21 from ,100 m depth to the NADW. Prokaryotic growth efficiencies of ,2% in the deep waters (depth range 1,200–4,000 m) indicate that the prokaryotic carbon demand exceeds dissolved organic matter input and surface primary production by 2 orders of magnitude. Cell-specific prokaryotic production was rather constant throughout the water column, ranging from 15 to 32 3 1023 fmol C cell21 d21 in the eastern and from 35 to 58 3 1023 fmol C cell21 d21 in the western basin. Along with increasing cell-specific respiration towards the deep water masses and the relatively short turnover time of the prokaryotic community in the dark ocean (34–54 d), prokaryotic activity in the meso- and bathypelagic North Atlantic might be higher than previously assumed.

1 - This study related recent distribution changes in seven macroalgae taxa (Acetabularia acetabulum, Chaetomorpha linum, Cladophora sp., Gracilariopsis longissima, Spyridia sp., Ulva laetevirens, Valonia aegagrophyla) to spatial (basin) and temporal (time) trophic differences in a meso-eutrophic Mediterranean coastal lagoon (Orbetello, Italy). 2 - In July 2003 and July 2009, the coverage percentage (CP) of each considered taxon was measured in 38 stations equally distributed in the Western and Eastern lagoon basins. All data were analysed using SURFER v8.0 software along with ANOVA, ANOSIM and multivariate analyses to produce geostatistical spatial distribution maps and to estimate statistical probabilities for “basin” and “time” factors. 3 - Data from this study were integrated with data on phanerogams reported by Giovani et al. (2010) to evaluate changes occurring at a functional group level from 2003-2009 using the Ecological Evaluation Index (EEI). 4 - Observed macroalgae changes may have been due to lagoon management activities performed during the study period. The removal of direct nitrate inputs seems to have forced specie-specific shifts that were highly significant only in the Western basin. 5 - Statistically significant differences at the taxon level have been indicated for Spyridia sp. (basin and time) and Cladophora sp. (time) taxa. Other non-significant changes included a rarefaction of Chaetomorpha linumin the Western basin and Spyridia sp. in the Eastern basin, and an increase of Gracilariopsis longissima, C. linum and Valonia aegagrophyla in the Eastern basin. 6 - EEI application indicated a general improvement in water quality due to management measures applied in Western basin, whereas the Eastern basin evidences stability/slight degradation from 2003-2009

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

The species composition, cell concentration, and biomass in the surface layer were determined at 10 stations in the central part of the Western Basin (WB) and one station in the Eastern Basin (EB) of the Large Aral Sea. A total of 42 algae species were found. Diatoms had the highest number of species. The similarity of the phytoplankton composition in the WB was high, whereas the phytoplankton composition in the WB and EB differed significantly. In the WB, the cell concentration and biomass of the phytoplankton varied from 826 × 103 to 6312 × 103 cells/l (the mean value was 1877 × 1586 × 103 cells/l) and from 53 to 241 μgC/l (the mean value was 95 × 56 μgC/l). In the EB, the phytoplankton abundance was 915 × 103 cells/l and 93 μgC/l. The vertical distribution of the phytoplankton in upper 35 m was investigated at one station in the WB. The maximum values of the algal cell concentration and biomass were recorded under the thermocline at the 20 m depth. The integrated biomass of the phytoplankton was 14 gC/m2.

Oxygen consumption, new production, vertical advection and environmental evolution in the Mediterranean Sea

<p>Qaidam Basin, located in the northern margin of the Tibet Plateau, is the junction of several tectonic blocks. The blocks’ extrusion resulted in large faults and strong historical earthquakes. Previous studies have shown that the crustal structures of the eastern and the western Qaidam Basin are obviously different. In this study, the seismic reflection and refraction phases from Conrad and Moho discontinuity in Qaidam Basin are distinguished by waveform simulation and travel time fitting of 3 regional earthquakes on 32 stations. The results of travel time fitting and waveform simulation show that the first arrivals in the epicenter range of 90km ~ 260km are the P* phases from the Conrad discontinuity. The depth of Conrad discontinuity under the eastern basin is about 4 km shallower than that in the western basin, which can be attributed to different crust thickening models between the eastern and western basin. In addition, the focal depths of regional earthquakes occurred within recent 5 years in Qaidam region also shows the difference of the Conrad discontinuity. The Conrad discontinuity is considered to be the lower boundary of the low velocity layer in the upper crust. The upper crust thickening in the western basin led to the sinking of the layer, while the multiple thrusts resulted in the rise of the lower crust in the east. The two different effects could interpret the depth change of the Conrad discontinuity in the basin from the west to the east. </p>

Another description of the Mediterranean Sea outflow

Long term changes in nutrients, chloride, and phytoplankton density in the nearshore waters of Lake Erie

The overall functioning of the Mediterranean Sea, which transforms Atlantic Water (AW) into Mediterranean Waters (MWs), has been comprehended for a while, and the process of dense water formation, which leads AW to sink offshore in specific northern zones of the Western and the Eastern Basins, has been studied in the world ocean. However, the circulation of the various waters from/to the basins openings to/from the zones of sinking is still debated in the Western Basin, while a similar debate is only being initiated in the Eastern Basin. The differences between the circulation schemas published up to now can be large and they have already been commented upon in papers published recently. To provide a coherent introductory chapter, only the authors’ analysis is presented hereafter. Overall, and due to the Coriolis effect, all waters (AW and MWs) that circulate at basin scale tend to follow, in the counterclockwise sense, the isobaths at their own level. Hence they tend to describe, in both the Western and the Eastern Basins, quasi permanent gyres a few 10s km thick and a few 1000s km long along the continental slope. This simple schema is complicated by the fact that the southern parts of both gyres described by AW are markedly unstable, the AW inflow being hence identified with the so-called Algerian Current and Libyo-Egyptian Current and generating specific systems over the whole depth. Indeed, these currents (100–200 m deep) meander and generate, a few times per year, anticyclonic eddies that can reach diameters of 100–200 km (and even more), propagate downstream (i.e. eastward) at speeds up to a few km/day, and sometimes extend down to the bottom (2–3000 m). Hence, these eddies follow the deeper isobaths, separate from their parent current where these isobaths diverge from the upper continental slope, and drift for years (up to 3 at least) in the central part of the basins, possibly coming back shoreward where they interact with their parent current, sometimes in a dramatic way. These eddies entrain AW and MWs from the peripheral part of the basins towards their central part, together with eddies induced by the wind in the Eastern Basin only and having similar characteristics. In both basins, the northern parts of the gyres display specific features linking them to the zones of AW sinking, hence being identified (more easily in the Western Basin than in the Eastern one due to the topography) with the so-called Northern Currents. In addition to these circulation features, and because the various openings are only a few 100s m deep, the deeper MWs must be uplifted before outflowing. This is achieved permanently and more or less everywhere through continuous mixing with less dense waters and uplifting by newly formed denser waters. This is also achieved when and where intense mixing with other waters (cascading from sills or sinking) and sucking upward straits occur. Mediterranean SeaWestern and Eastern basinsWater masses General circulationMesoscale

Abstract. Climate change accelerates the global water cycle. However, the relationships between climate change and hydrological processes in the alpine arid regions remain elusive. We sampled surface water and groundwater at high spatial and temporal resolutions to investigate these relationships in the Qaidam Basin, an extremely arid area in the northeastern Tibetan Plateau. Stable H–O isotopes and radioactive 3H isotopes were combined with atmospheric simulations to examine hydrological processes and their response mechanisms to climate change. Contemporary climate processes and change dominate the spatial and temporal variations of surface water isotopes, specifically the westerlies moisture transport and the local temperature and precipitation regimes. The H–O isotopic compositions in the eastern Kunlun Mountains showed a gradually depleted eastward pattern, while a reverse pattern occurred in the Qilian Mountains water system. Precipitation contributed significantly more to river discharge in the eastern basin (approximately 45 %) than in the middle and western basins (10 %–15 %). Moreover, increasing precipitation and a shrinking cryosphere caused by current climate change have accelerated basin groundwater circulation. In the eastern and southwestern Qaidam Basin, precipitation and meltwater infiltrate along preferential flow paths, such as faults, volcanic channels, and fissures, permitting rapid seasonal groundwater recharge and enhanced terrestrial water storage. However, compensating for water loss due to long-term ice and snow melt will be a challenge under projected increasing precipitation in the southwestern Qaidam Basin, and the total water storage may show a trend of increasing before decreasing. Great uncertainty about water is a potential climate change risk facing the arid Qaidam Basin.

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

Improved modelling of the Messinian Salinity Crisis and conceptual implications