Seasonal variations in primary production (PP) in the Kara Sea are underresearched. Previous studies only collected data during autumn or in late summer. However, the middle of summer is close to the ...beginning of the growing season, when PP can contribute significantly to annual water column integrated primary production (IPP). In addition, differences can be expected in the spatial and vertical distribution of phytoplankton communities in this period. This gap in midsummer data was addressed within the framework of a multidisciplinary research cruise by the R/V “Akademik Mstislav Keldysh” (from 15 July to 18 August 2016). High values of IPP (> 200 mgC m
−2
day
−1
) and surface chlorophyll
a
(Chl
a
) concentration (Chl
0
> 1 mg m
−3
) were associated with the Ob–Yenisey river plume, located in the central part of the Kara Sea. Beyond the influence of the plume, in the western and southwestern regions of the Kara Sea, well-pronounced subsurface chlorophyll maxima (SCM) were observed. In some cases, the Chl
a
concentration in SCM exceeded Chl
0
by two orders of magnitude. SCM were often accompanied by subsurface PP maxima (SPM). At stations where SCM was pronounced, IPP values reached 500–800 mgC m
−2
day
−1
, and > 30 % of IPP was accounted for by SPM-integrated PP. Thus, in the middle of summer in the Kara Sea, IPP was linked with the chlorophyll-specific phytoplankton biomass and depended on the strength of the SCM.
—
This paper analyzes the use of the automated aftershock hazards assessment system (AFCAST) through the example of a series of aftershocks of the
M
w
7.8 earthquake in Turkey of February 6, 2023 ...(the Pazarcik earthquake). The paper presents automated estimates of the aftershock activity area, the magnitude of the strongest aftershock, and the duration of the hazardous period, yielded using data on the main shock and on the first aftershocks.
A relative decrease in the fraction of large aftershocks in the first days after earthquakes in subduction zones is demonstrated, and a connection of this phenomenon with aseismic stress release is ...shown.
The purpose of this study was to assess the performance of Cepheid® Xpert MTB/RIF® (“Xpert”) and TB-Biochip® MDR (“TB-Biochip”). Sputum specimens from adults with presumptive tuberculosis (TB) were ...homogenized and split for: (1) direct Xpert and microscopy, and (2) concentration for Xpert, microscopy, culture Lowenstein–Jensen (LJ) solid media and Mycobacteria Growth Indicator Tube® (MGIT), indirect drug susceptibility testing (DST) using the absolute concentration method and MGIT, and TB-Biochip. In total, 109 of 238 (45.8 %) specimens were culture-positive for
Mycobacterium tuberculosis
complex (MTBC), and, of these, 67 isolates were rifampicin resistant (RIF-R) by phenotypic DST and 64/67 (95.5 %) were isoniazid resistant (INH-R). Compared to culture of the same specimen, a single direct Xpert was more sensitive for detecting MTBC 95.3 %, 95 % confidence interval (CI), 90.0–98.3 % than direct (59.6 %, 95 % CI, 50.2–68.5 %) or concentrated smear (85.3 %, 95 % CI, 77.7–91.1 %) or LJ culture (80.8 %, 95 % CI, 72.4–87.5 %); the specificity was 86.0 % (95 % CI, 78.9–91.3 %). Compared with MGIT DST, Xpert correctly identified 98.2 % (95 % CI, 91.5–99.9 %) of RIF-R and 95.5 % (95 % CI, 85.8–99.2 %) of RIF-susceptible (RIF-S) specimens. In a subset of 104 specimens, the sensitivity of TB-Biochip for MTBC detection compared to culture was 97.3 % (95 % CI, 91.0–99.5 %); the specificity was 78.1 % (95 % CI, 61.5–89.9 %). TB-Biochip correctly identified 100 % (95 % CI, 94.2–100 %) of RIF-R, 94.7 % (95 % CI, 76.7–99.7 %) of RIF-S, 98.2 % (95 % CI, 91.4–99.9 %) of INH-R, and 78.6 % (95 % CI, 52.1–94.2 %) of INH-S specimens compared to MGIT DST. Xpert and Biochip were similar in accuracy for detecting MTBC and RIF resistance compared to conventional culture methods.
The variability of sea ice in the Weddell Sea, along with melting of glaciers of the Antarctic Peninsula and ice shelves, determines the volumes of melt water entering the water area, which, among ...other things, affects the hydrophysical conditions of phytoplankton development. Based on the materials of a scientific cruise carried out in the Powell Basin in January–February 2020, the spatial distribution of melt water content and its influence on the hydrophysical structure of the surface layer, the vertical distribution of fluorescence values and, the content of chlorophyll
a
were investigated. Areas with the highest freshening were identified in the eastern part of the Powell Basin (shelf of the South Orkney Islands) and in the southwestern part of the basin in the area of ice removal from the Weddell Sea to the north. The least freshening was recorded in the northwestern part of the Powell Basin. It is shown that the distribution of melt water was the main factor enhancing the vertical stability of the surface layer. An increase in vertical stability led to the formation of hydrophysical environmental conditions preventing vertical mixing, which affected the development of phytoplankton communities, namely, their concentration within a limited depth range in the surface layer. In the absence of other factors limiting phytoplankton development in these, well-shown peaks of chlorophyll concentration in the 0–50 m layer were formed. These zones included the shelf area of the South Orkney Islands and northern boundary of the Powell Basin. In areas with an insignificant freshening effect, the fluorescence peaks were diffuse; the phytoplankton community developed in a wider depth range of the surface layer.
The main disadvantages of selected elements of seismicity modeling for composing the General Seismic Zoning maps are considered in the framework of a probabilistic approach. We proposed a method that ...should provide more precise assessment of probable future seismicity after the improvements of the disadvantages. A stochastic seismicity model is suggested for the first time as a synthetic earthquake catalog, which is generated for an arbitrary conditional period and which reproduces the properties of the catalog of factual earthquakes including spatiotemporal grouping. The verification method of seismicity models is suggested to check the correspondence of the models to the primary data and the assessment of the predictive efficiency of the models and to compare various models based on these characteristics.
The distribution of primary production (PP), chlorophyll
a
concentration (Chl
a
), and size structure of the phytoplankton community were studied in the Kara Sea during the first-year ice retreat in ...late June 2021. The maximum value of water column PP (IPP) reached 1352 mgC m
–2
day
–1
. The ice-edge phytoplankton bloom was characterized by high averaged of IPP and Chl
a
integrated in the photosynthetic layer (Chl
phs
) values: 740 mgC m
–2
day
–1
and 81.40 mg m
–2
, respectively. The highest IPP values were observed at sites where Chl
a
was concentrated in the upper mixed layer or where the subsurface chlorophyll maximum coincided with the pycnocline. Over the area of phytoplankton bloom, the contribution of microphytoplankton (>20 µm) to the total IPP and Chl
phs
was 92 and 82%, respectively. Contribution of picophytoplankton (<3 µm) to the total PP increased along the depth until reaching the lower margin of layer of photosynthesis, from 3 to 70%, on average. No similar pattern has been observed for vertical distribution of Chl
a
. This pattern was evidenced by an increase in the chlorophyll specific carbon fixation rate (assimilation number) of picophytoplankton with depth under low insolation conditions.
PDF
