11β-Hydroxysteroid dehydrogenase-type 2 evolved from an ancestral 17β-Hydroxysteroid dehydrogenase-type 2

11β-Hydroxysteroid dehydrogenase-type 2 (11β-HSD2) regulates the local concentration of cortisol that can activate the glucocorticoid receptor and mineralocorticoid receptor, as well as the concentration of 11-keto-testosterone, the active androgen in fish. Similarly, 17β-HSD2 regulates the levels of testosterone and estradiol that activate the androgen receptor and estrogen receptor, respectively. Interestingly, although human 11β-HSD2 and 17β-HSD2 act at different positions on different steroids, these enzymes are paralogs. Despite the physiological importance of 11β-HSD2 and 17β-HSD2, details of their origins and divergence from a common ancestor are not known. An opportunity to understand their evolution is presented by the recent sequencing of genomes from sea urchin, a basal deuterostome, and amphioxus, a basal chordate, and the availability of substantial sequence for acorn worm and elephant shark, which together provide a more complete dataset for analysis of the origins of 11β-HSD2 and 17β-HSD2. BLAST searches find an ancestral sequence of 17β-HSD2 in sea urchin, acorn worm and amphioxus, while an ancestral sequence of 11β-HSD2 first appears in sharks. Sequence analyses indicate that 17β-HSD2 in sea urchin may have a non-enzymatic activity. Evolutionary analyses indicate that if acorn worm 17β-HSD2 is catalytically active, then it metabolizes novel substrate(s).     

Phylogeny, diversification rates and species boundaries of Mesoamerican firs (Abies, Pinaceae) in a genus-wide context

The genus Abies is distributed discontinuously in the temperate and subtropical montane forests of the northern hemisphere. In Mesoamerica (Mexico and northern Central America), modern firs originated from the divergence of isolated mountain populations of migrating North American taxa. However, the number of ancestral species, migratory waves and diversification speed of these taxa is unknown. Here, variation in repetitive (Pt30204, Pt63718, and Pt71936) and non-repetitive (rbcL, rps18-rpl20 and trnL-trnF) regions of the chloroplast genome was used to reconstruct the phylogenetic relationships of the Mesoamerican Abies in a genus-wide context. These phylogenies and two fossil-calibrated scenarios were further employed to estimate divergence dates and diversification rates within the genus, and to test the hypothesis that, as in many angiosperms, conifers may exhibit accelerated speciation rates in the subtropics. All phylogenies showed five main clusters that mostly agreed with the currently recognized sections of Abies and with the geographic distribution of species. The Mesoamerican taxa formed a single group with species from southwestern North America of sections Oiamel and Grandis. However, populations of the same species were not monophyletic within this group. Divergence of this whole group dated back to the late Paleocene and the early Miocene depending on the calibration used, which translated in very low diversification rates (r_0.0 = 0.026-0.054, r_0.9 = 0.009-0.019 sp/Ma). Such low rates were a constant along the entire genus, including both the subtropical and temperate taxa. An extended phylogeographic analysis on the Mesoamerican clade indicated that Abies flinckii and A. concolor were the most divergent taxa, while the remaining species (A. durangensis, A. guatemalensis, A. hickelii, A. religiosa and A. vejari) formed a single group. Altogether, these results show that divergence of Mesoamerican firs coincides with a model of environmental stasis and decreased extinction rate, being probably prompted by a series of range expansions and isolation-by-distance.     

Microbian Indication of Pollution of the Coastal Zone of the Sea of Okhotsk and Avacha Bay

The results of microbiological analysis of a number of microorganisms of various ecological–trophic groups in plankton microbial communities of some water areas of the Sea of Okhotsk and Avacha Bay are presented. The data were compared to the hydrochemical parameters (temperature, salinity, BOD₅, dissolved oxygen, phosphates, organic phosphate, detergents) determined simultaneously. The microbian indication method is used for express assessment of water pollution of the surveyed areas. The data demonstrated that Avacha Bay was subjected to heavier anthropogenic impact than the water areas of the ports of Kholmsk and Magadan.     

Suboxic zone in the Black Sea: real fact or analytical artefact

A reevaluation of the presence of a suboxic zone above the sulphide onset and the fine structure of the oxic/anoxic interface in the Black Sea is discussed. The results qualify this phenomenon as an analytical artefact and that the methods used for dissolved oxygen (DO) profiling are not applicable in the situation. Former and recent studies have established the stability of the oxic/anoxic interface structure with two principal components: the low DO gradient zone situated at the base of oxycline, and of the C-layer located beneath the sulphide onset boundary, where DO and sulphide coexist. The existence of the C-layer does not permit a suboxic zone void of perceptible DO and sulphide.     

Blooms of tunicates Oikopleura spp. and Dolioletta gegenbauri in the Seto Inland Sea, Japan, during summer

The ecological importance of appendicularians Oikopleura dioica and O. longicauda, and a doliolid Dolioletta gegenbauri as metazoan secondary producers was assessed in summer 1997 in the Seto Inland Sea, Japan. Blooms by the appendicularians occurred twice within a month following peaks of pico-/nanoplankton biomass. The biomass of Oikopleura spp. averaged over the water column (<B> ranged 0.1 to 8.0 μgC l-¹ and temporal average of <B> over the survey period ( ) was 3.2 μgC l-¹, 70% of for calanoid copepods. Furthermore, the temporal average of the production for Oikopleura spp. was 2.4 times higher than that for calanoids, reflecting the extraordinary high growth rates of the appendicularians. D. gegenbauri developed its population following a diatom bloom and <B> reached to 37 μgC l-¹ at the peak time. Although individuals of D. gegenbauri were seldom observed during the first half of the survey, for the doliolid (8.4 μgC l-¹) nearly doubled that for calanoids. These results indicate that the gelatinous tunicates Oikopleura spp. and D. gegenbauri play important roles as metazoan secondary producers in the Seto Inland Sea during summer. This revised version was published online in September 2006 with corrections to the Cover Date.     

Introduction into the ecosystem of the North Sea: Hydrography,biota, and food web relationships

The North Sea, one of the most productive of the earth's seas and oceans, is also surrounded by some of earth's most densely populated and heavily industrialized regions. A growing number of signals are being received which indicate that this valuable ecosystem is increasingly under stress. This has generated a corresponding increase in concern over the steps to be taken to protect the North Sea. While there are divergent views on what constitutes an ‘ideal’ North Sea, there is a general recognition that any decisions that are made should be based on a good understanding of this ecosystem. The intention of this paper is to give an overview of what is presently known, and to identify areas where more studies are needed. A brief summary of the hydrography and the biota of the North Sea is given. Biotic and abiotic structure justify partitioning the North Sea into three ecologically different regions: southern, central, and northern. For the most part, neither the top predators,e.g. marine birds and mammals, nor the macroalgae and sea grasses are included in this overview.     

南海北部生态系统食物网结构、能量流动及系统特征

根据20072008年在南海北部(107°00'120°00'E、17°00'23°30'N)进行的海洋生态综合调查数据,应用Ecopath with Ecosim软件构建了南海北部生态系统的生态通道模型,并通过模型分析了南海北部海洋生态系统的食物网结构、能量流动和系统的总体特征,并简要总结过度捕捞生态系统的基本特征。结果表明,南海北部海洋生态系统以捕食食物链为主要能流通道,初级生产者是系统能量的主要来源。各功能群的营养级范围为13.99,哺乳动物占据了最高的营养层,平均渔获物营养级为2.93。利用生态网络分析,系统的能量流动主要有6级,来自初级生产者的能流效率为12.6%,来自碎屑的转换效率为10.4%,平均能量转换效率为11.5%。系统连接指数(Connectance Index,CI)和系统杂食指数(System Omnivory Index,SOI)分别为0.290和0.239;Finn’s循环指数(Finn’scy cling index,FCI)和系统平均路径长度(Finn’s mean path length,MPL)分别为4.380和2.476;总初级生产力/总呼吸为2.596,综合研究表明当前南海北部海洋生态系统处于不成熟阶段。     

Variability at different spatial scales of a coralligenous assemblage at Giannutri Island (Tuscan Archipelago,northwest Mediterranean)

This study was carried out on the rocky cliffs of Giannutri Island (Tyrrhenian Sea, Italy) to test the hypothesis that coralligenous assemblages are consistent within the bathymetric range considered (25–35 m depth) over three different spatial scales (1000 m, 100 m and 10 m). A multi-factorial sampling design was used to assess patterns of vertical distribution in the studied area. Data on the percent cover of algae and invertebrates were collected at three depths (25, 30 and 35 m) using a photographic method, and percentage cover was obtained using a visual method. Analysis of the results using ANOVA indicated that the distribution and abundance of algae and some invertebrates of the sublittoral assemblages are clearly heterogeneous. Algae, sponges and bryozoans showed significant variability in distribution and abundance at different depths, but this variability was not consistent amongst transects. Ascidians did not show any variability, while the abundance of anthozoans differed significantly amongst transects. We concluded that heterogeneity in the distribution and abundance of the taxa analysed is related to the smallest spatial scale investigated (10's of m). Some of the possible causes of the observed variability are discussed.     

Phytoplankton biomass and production in northern South China Sea during summer: Influenced by Pearl River discharge and coastal upwelling

Chlorophyll a and primary production were studied in northern South China Sea during summer from 2007 to 2008. Microplankton dominated total phytoplankton biomass in the coast, while picoplankton dominated in the offshore. Algae bloom caused by Thalassionema nitzschioides was found at the subsurface of upwelling regions (D2, C2) in 2008, and maximum of phytoplankton abundance reached 1.58 × 10⁶ ind L^?1. Integrated primary production ranged from 189.3 to 976.2 mg m^?2 d^?1 in 2007, and ranged from 652.1 to 6601 mg m^?2 d^?1 in 2008. PP showed positive relationship with IPP (p < 0.01) and negative relationship with SST (p < 0.05). Coastal upwelling and Pearl River discharge sustained high PP, and played important role in regulating the phytoplankton biomass and production.