The Corwen Outlier and its implications for the Mid Mississippian palaeogeography of North Wales,UK

The isolated outlier of Visean (Mid Mississippian) limestones and sandstones near Corwen, North Wales, UK, provides a critical constraint on regional tectonic and palaeogeographical models. The late Asbian to Brigantian succession comprises a series of shoaling‐upwards cycles (parasequences). These were the product of forced, glacioeustatic regressions and have boundaries that testify to emergence, karstic dissolution and soil formation on a low gradient carbonate platform prior to flooding and the resumption of marine deposition. The recognition of two of the main marker beds within the North Wales Visean succession (Main Shale and Coral Bed) together with a newly applied foraminiferal and algal biozonation allow the outlier succession to be correlated with other Visean outcrops in the region and more widely throughout the British Isles. In revealing regional thickness and facies variations, these comparisons show that the outlier succession was deposited landward of the early Asbian shoreline in a region of enhanced subsidence localized along the Bala Lineament. The Corwen Outlier suggests that, within narrow gulfs associated with the region's major tectonic lineaments, Mississippian carbonate facies extended farther south into the contemporary hinterland of older rocks and that, in response to Brigantian climate change, these topographic features likely also influenced fluvial catchments supplying siliciclastic sediment to the platform's landward margin and, subsequently, Namurian deltas. Contrary to earlier suggestions, Visean outcrop patterns, facies distributions and thicknesses in the vicinity of the Bala Lineament can be explained without the need to invoke extensive post‐depositional lateral displacements. BGS © NERC 2013. Geological Journal © John Wiley & Sons Ltd.     

Planetary Bioresources and Astroecology: 1. Planetary Microcosm Bioassays of Martian and Carbonaceous Chondrite Materials: Nutrients, Electrolyte Solutions, and Algal and Plant Responses

The biological fertilities of planetary materials can be assessed using microcosms based on meteorites. This study applies microcosm tests to martian meteorites and analogues and to carbonaceous chondrites. The biological fertilities of these materials are rated based on the soluble electrolyte nutrients, the growth of mesophile and cold-tolerant algae, and plant tissue cultures. The results show that the meteorites, in particular the Murchison CM2 carbonaceous chondrite and DaG 476 martian shergottite, contain high levels of water-extractable Ca, Mg, and SO₄-S. The martian meteorites DaG 476 and EETA 79001 also contain higher levels of extractable essential nutrients NO₃-N (0.013-0.017 g kg⁻¹) and PO₄-P (0.019-0.046 g kg⁻¹) than the terrestrial analogues. The yields of most of the water-extractable electrolytes vary only by factors of 2-3 under a wide range of planetary conditions. However, the long-term extractable phosphate increases significantly under a CO₂ atmosphere. The biological yields of algae and plant tissue cultures correlate with extractable NO₃-N and PO₄-P, identifying these as the limiting nutrients. Mesophilic algae and Asparagus officinalis cultures are identified as useful bioassay agents. A fertility rating system based on microcosm tests is proposed. The results rate the fertilities in the order martian basalts > terrestrial basalt, agricultural soil > carbonaceous chondrites, lava ash > cumulate igneous rock. The results demonstrate the application of planetary microcosms in experimental astroecology to rate planetary materials as targets for astrobiology exploration and as potential space bioresources. For example, the extractable materials in Murchison suggest that concentrated internal solutions in carbonaceous asteroids (3.8 mol L⁻¹ electrolytes and 10 g L⁻¹ organics) can support and disperse microorganisms introduced by natural or directed panspermia in early solar systems. The results also suggest that carbonaceous asteroids and martian basalts can serve as potential future resources for substantial biological populations in the Solar System.     

Modelling the growth of cyanobacteria (GrowSCUM)

Toxic cyanobacteria have become a common nuisance in freshwater lakes and reservoirs throughout the world, sometimes resulting in the closure of sites with high amenity value. Cyanobacteria are able to regulate their buoyancy state in response to changing photosynthetic rates. Additionally, the cyanobacteria are liable to become entrained within wind-induced near-surface turbulent currents, resulting in mixing and mass transport. These movement processes have been modelled. A mathematical function is presented which describes light- and nutrient-limited cyanobacterial growth. The growth model is integrated with a previous movement model (SCUM: simulation of cyanobacterial underwater movement) as movement patterns and wind-induced lake mixing strongly affect the intensity and duration of light received by the cyanobacteria and thereby determine the photosynthetic potential. Results of the model suggest that cyanobacteria are resistant to periods of lake mixing and continue to increase their biomass, but at a depressed rate. Growth is most rapid under calm conditions. The results agree well with field-based findings, confirming the validity of the growth function.     

盐度胁迫下中肋骨条藻和东海原甲藻的生长与內源多胺调节作用的关系*

提要 实验室内开展了不同盐度梯度下培养常见的两种赤潮藻中肋骨条藻(Skeletonema costatum)和东海原甲藻(Prorocentrum donghaiense)的实验,根据logistic生长模型获得了生长参数Bf和mmax,并测定了藻体中过氧化物酶(POD)、二胺氧化酶(DAO)、多胺氧化酶(PAO)的活性和丙二醛(MDA)、腐胺(Put)、亚精胺(Spd)、精胺(Spm)的含量。结果表明,高、低盐度胁迫下,两种藻均会积累MDA,活性氧自由基的伤害增强,藻的生长受到了抑制。同时,两种藻都会提升多胺含量,通过多胺的调节作用来缓解胁迫的伤害,促进生长,但是在提升的多胺种类和形态上,两种藻存在着差异。高盐胁迫下,中肋骨条藻会提升多胺尤其是游离态多胺的含量来缓解伤害,东海原甲藻则依靠结合态的亚精胺和游离态的精胺的调节作用。低盐胁迫下,中肋骨条藻会提升游离态腐胺的含量,而东海原甲藻体内各形态的多胺都会上升。     

A Model Describing the Time Course and Variability in Toxicity of Hydrophobic Chemicals to Aquatic Organisms-Toxicity of chlorinated benzenes to marine algae

The growth of Chlorella marine, Nannochloris oculate, Pyramimonaos sp., Platymonas subcordiformis and Phaeodactylum tricornutum exposed to chlorobenzene, 1,2-dichlorobenzene, 1, 2, 3, 4-tetrachlorobenzene and pentachlorobenzene was tested. The Boltzman equation was used to describe organism growth. The time course for uptake of hydrophobic organic chemicals (HOCs) by aquatic organisms was expressed by incorporating growth and, if desired, the effect of metabolism into the HOC bioconcentration process. The probability of any given concentration of HOCs in the organisms causing a specified toxic endpoint was expressed with a modified Weibull distribution function. The combined bioconcentration and probability equations were tested with data for time course of incubation of algae exposed to chlorinated benzenes (CBs). A set of parameters, including the uptake rate constant k1, the elimination rate constant k2 and thereafter the bioconcentration factor on a dry weight basis, BCFD, the critical HOC concentration in the organism resulting in a specified toxic endpoint, C*A, and the spread factor, S, could be obtained by fitting only experimental data for percent growth inhibition(%)-time-CB exposure concentration. The average coefficients of variation within CBs were 15.2% for BCFD, 21.0%for k1, 18.3% for k2, 8.1% for C*A and 9.7% for S. The variability in toxicity (such as EC10, EC50, ECg0) derived from the model equations agreed well with those experimentally observed.     

Three new species of Batrachospermum Roth （Batrachospermaceae, Rhodophyta） in China

Three new species of Batrachospermum Roth (Batrachospermales, Rhodophyta) from China are described in this paper. B. yunnanense sp. nov. has long-cylindrical trichogynes with long stalks and is diagnostic of section Virescentia. Within this section, B. yunnanense is similar to B. helminthosum Bory emend. Sheath et al., but it is dioecious and has curved carpogonial branches, while the latter is monoecious and has straight carpogonial branches. It is also similar to B. transtaganum Reis, but it differs from the latter in long carpogonia,big carposporophytes and carposporangia. It is considered that B. nothocladoideum sp. nov. is assigned to section Contorta, subsection Kushiroense, because its carpogonial branches are twisted and gonimoblast filaments are loosely agglomerated. This new species similar to B. iriomotense Kumano, but with short fascicles, long-ovoid or subpyriform cells, numerous terminal hairs, long-ellipsoid trichogynes, big carposporophytes and small carposporangia. The plant is quite tough and cartilaginous and similar to Nothocladus in gross morphology, but its carposporophytes are compact instead of diffuse. This shows that it may be a transitional species between section Contorta and genus Nothocladus. So, B. transitorium sp. nov. should belong to section Contorta, subsection Kushiroense, because of its curved or twisted carpogonial branches and loosely agglomerated gonimoblast filaments, with globose or subglobose cells in fascicles similar to B. spermatiophorum Vis et Sheath, but no colourless spermatiophores. In terms of small and numerous carposporophytes, B. transitorium sp. nov. is similar to some species of section Batrachospermum. However, their other features are unique, indicating its transitional nature between section Contorta and Batrachospermum.     

Composition,export and faunal utilization of drift vegetation in the salt river submarine canyon

Submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water. We studied the composition, export, and faunal utilization of shallow, nearshore benthic vegetation as it was transported to offshore areas via the Salt River submarine canyon on the island of St Croix, U.S. Virgin Islands. The study was conducted using a saturation diving system (NULS-1: Hydrolab) during two missions in April and August, 1980. Using bottom drifters deployed in Salt River Bay and the submarine canyon, we recorded net benthic current flow up to 2 cm s^?1 moving out of the lagoon and down the canyon to deeper water. Using bottom nets set up at the canyon head and at the 29 m isobar, and from transect surveys and drift clump samples, we determined drift plant export rates and drift clump biomass and species composition. The dominant drift plants were Thalassia testudinum and Syringodium filiforme and algae in the genera Dictyota, Dictyopterus, and Diloplus. During the second mission, the seagrass Halophila decipiens became more abundant, both in the drift and in large patches along the canyon floor. In both missions, more drift was collected in the nets during high wind conditions than during calmer days. Calculated turnover times ranged from 0·01 to 4·4 days for algae in the order Dictyotales and 4·4 to 18 days for Thalassia blades. Total exported biomass of drift vegetation varied between 1·4 to 65·1 kg wet wt day^?1. Samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes, but in relatively low numbers. Faunal numbers were most strongly related to rate of drift movement.     

Implications for improving paleolimnological inference models utilizing scale-bearing siliceous algae: transforming scale counts to cell counts

Microfossil remains of siliceous scale-bearing members of the Synurophyceae and Chrysophyceae have become of increasing importance in paleolimnological studies, especially ones involving the reconstruction of historical lakewater pH. Since the numbers of scales per cell for individual taxa are not known, inference models have been based on the relative abundances of scales, not cells. Theoretically, inference models based on the relative numbers of cells would be more appropriate. Morphometric characteristics of scales and cells were used to estimate the mean numbers of scales per cell for 38 taxa. The mean numbers of scales per cell ranged from a low of 27 to a high of 214; over 80% of the taxa had fewer than 100 scales per cell. A highly significant model for estimating the numbers of scales per cell was developed based on scale and cell surface area measurements. The application of the model in order to estimate the number of scales per cell for additional taxa, or ones found to have different morphometric measurements, is discussed.     

中国褐毛藻属Halothrix的分类学研究

对作者于1998~2003年间在中国沿海采集的褐毛藻属 Halothrix 标本进行了分类研究。经鉴定,确认有4个种,即可疑褐毛藻H. ambigua Yamada、细弱褐毛藻H. gracilis Luan et Ding sp. nov.、褐毛藻 H. lumbricalis (Kuetzing) Reinke和垫状褐毛藻 H. pulvinata Luan et Ding sp. nov.,其中新种2个。文中对这4个种进行了较详细的特征描述,以及较完整的其他分类学信息,并编制了检索表。细弱褐毛藻H. gracilis Luan et Ding sp. nov.的长同化丝稍细,直径15～55μm,中、上部细胞较长,长宽比为1.3～3;短同化丝的细胞较多,10~17个;具有匍匐丝体。垫状褐毛藻 H. pulvinata Luan et Ding sp. nov.具有明显垫状的基部,由多数无色丝体组成,丝体细胞13~20个,细胞长宽比为1.3~11,长同化丝在基部多分枝。其研究结果在一定程度上丰富了我国大型海藻的物种多样性。模式标本保存在中国科学院海洋研究所海洋生物标本馆(AST)。