Condition of coastal mesoplankton communities in the northeastern area of the Black Sea in 2005

The structure and distribution of mesoplankton in the northeastern part of the Black Sea along 6-mile and 100-mile sections in the area off Golubaya Bay (near the city of Gelendzhik) were analyzed. The studies were performed from R/V Akvanavt and the boat Ashamba. The observations were carried out during the vegetation season from the beginning of June to the first half of October 2005. Samples of mesoplankton were collected with use of a BSD net with an opening of 0.1 m² and a mesh size of 180 μm. Both the total (over the entire water column) and layer-by-layer (separately for the upper quasi-homogeneous layer, the seasonal thermocline, and the subthermocline layer) hauls were performed down to the bottom (at sea depths of less than 200 m) or down to the upper boundary of the hydrogen sulfide waters. The particular hydrophysical conditions that were observed in 2005 resulted in an approximately one-month advance of the phenological condition of the planktonic community as compared to the usual pattern. Beroe ovata appeared in the plankton at the end of July, the mass development of Mnemiopsis leidyi was suppressed, and the duration of its influence on edible zooplankton was essentially reduced. As a result, the total mesoplankton biomass in August–October 2005 was 1.5–2 times as great as that in 2004. The abundance of Acartia clausi increased approximately 4–5 times and the quantity of Sagitta setosa also considerably increased. At selected stations, Mnemiopsis leidyias, the main predator in the community, was replaced by Sagitta setosa.     

西沙群岛生物碳酸盐的成因和沉积:来自活体仙掌藻的证据

A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems: the depleted atoll system and growth atoll system; the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected,the isotopic ages of 14 C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60–100 g/m2; the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium(Te), rhodium(Rh) and strontium. It is believed that the Halimeda grow slowly,including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration.     

Features of wind waves at the southeastern coast of Sakhalin according to bottom-pressure measurements

The results of wind-wave measurements with bottom-pressure sensors are discussed. These measurements were performed at the southeastern coast of the Island of Sakhalin in 2006–2009. The problems of converting data obtained with these sensors into water-level displacent in the context of the linear theory are noted. Twenty records with a duration of 2 weeks to 3 months were obtained. These records contain from 150000 to 1200000 waves for three different observation points located at the southeastern coast of Sakhalin in the regions of the village of Vzmor’ye, Lake Izmenchivoye, and the Cape of Ostryi. The estimates obtained for wave-height distributions were approximated by the Weibull distribution. They were compared to the theoretical Rayleigh, Forristall, Weibull, and Glukhovskii distributions. As one would expect, in the region of small wave heights, all distributions prove to be close to one another, and, for large wave heights, the Weibull distribution is preferred.     

Dispersal of the Zhujiang River (Pearl River) derived sediment in the Holocene

High-resolution Chirp profiling and coring reveals an elongated(ca. 400 km) Holocene Zhujiang River(Pearl River)-derived mud area(maximum thickness 20 m) extending from the Zhujiang River Delta, southwestward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the-120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the Western Pacific marginal seas(mainly Changjiang(Yangtze) and Huanghe(Yellow) Rivers derived) indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages: Stage 1 is before the mid-Holocene sea-level highstand(ca. 7.0 cal. ka BP), the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse-1C; Stage 2, after the mid-Holocene sealevel highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5–10 m water depth to less than 1–2 m around 20–30 m water depth. In addition, we also find a developed distal clinoform in the east of the Leizhou Peninsula.     

Thioploca spp. sheaths as niches for bacterial and protistan assemblages

Sulfide oxidizing bacterial mats are common in regions of the continental shelves characterized by high primary production and the resultant oxygen minimum zone. These mats are made up of several species of Beggiatoa and/or Thioploca, which oxidize sulfide that is generated in the sediment. Thioploca spp. inhabit a large polysaccharide sheath that encompasses bundles of 1–20 filaments (trichomes), each ranging from 3 to 60 μm in diameter. This sheath has been shown to be a critical component of the autecology of Thioploca. Analysis of Thioploca from cold seeps in Monterey Bay using light and transmission electron microscopy identified new and diverse microbial assemblages associated with interstitial spaces between trichomes, inside the sheath. Small diameter, non‐vacuolate, filamentous prokaryotes were numerous. Amoebae, euglenozoa, ciliates and other protists of unknown affiliation were observed in sheaths. Most of the protists possessed food vacuoles and some protists showed ultrastructural evidence of endosymbionts. These observations suggest that Thioploca sheaths may serve as oases on the sea floor, providing nutritional and detoxification services to previously unrecognized microbial partners.     

Geoelectric section of the Central Tien Shan: Sequential inversion of the magnetovariational and magnetotelluric data along the Naryn Line

The paper presents the results of 2D inversion of deep magnetotelluric (MT) and magnetovariational (MV) soundings along the Naryn Line. The method of partial (sequential) inversions is used. According to this method, at the first stage, magnetovariation responses are used for the localization of deep anomalies of electrical conductivity, and then the magnetotelluric sounding data are invoked to refine the structure of the host medium and the structural details in the upper part of the section. It is shown that this approach enables one to estimate the informativeness of separate components of the electromagnetic field, to reduce the distorting influence of the near-surface geoelectric inhomogeneities, and to increase the stability of the final solution of the inverse problem.     

The arrow of time

Why does time apparently fly one way, when the laws of physics are actually time-symmetrical? Paul Davies proposes a quantum solution, in the Whitrow Lecture 2004, given on 8 October 2004.     

Accuracy estimates for some global analytical models of the Earth’s main magnetic field on the basis of data on gradient magnetic surveys at stratospheric balloons

Two global analytical models of the main magnetic field of the Earth (MFE) have been used to determine their potential in deriving an anomalous MFE from balloon magnetic surveys conducted at altitudes of ～30 km. The daily mean spherical harmonic model (DMSHM) constructed from satellite data on the day of balloon magnetic surveys was analyzed. This model for the day of magnetic surveys was shown to be almost free of errors associated with secular variations and can be recommended for deriving an anomalous MFE. The error of the enhanced magnetic model (EMM) was estimated depending on the number of harmonics used in the model. The model limited by the first 13 harmonics was shown to be able to lead to errors in the main MFE of around 15 nT. The EMM developed to n = m = 720 and constructed on the basis of satellite and ground-based magnetic data fails to adequately simulate the anomalous MFE at altitudes of 30 km. To construct a representative model developed to m = n = 720, ground-based magnetic data should be replaced by data of balloon magnetic surveys for altitudes of ～30 km. The results of investigations were confirmed by a balloon experiment conducted by Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences and the Moscow Aviation Institute.