The respiratory response of juvenile mud crabs, Rhithropanopeus harrisii to variations in salinity and following short-term exposure to halowax 1099®, a polychlorinated naphthalene (PCN)

Juvenile mud crabs Rhithropanopeus harrisii were exposed for five days to Halowax 1099, a polychlorinated naphthalene (approximately 1:1 ratio of tri- and tetrachlorinated isomers). Exposure concentrations were 0, 20, 50 or 100 μg/litre. The exposure salinity was 15%. At the end of the exposure period, respiratory rates of the crabs were determined at 15% S. The respiratory rates were also determined for control and exposed animals which were osmotically shocked by a move from 15% S to either 5 or 25% S immediately before respirometry. Exposure to PCNs always caused the mean respiratory rates of juvenile crabs to increase over control values. The respiratory response of crabs to PCN exposure was similar at the steady-state salinity (15% S) and after hyperosmotic shock (25% S). However, the mean rate for animals exposed to PCNs and given a hyposmotic shock was significantly higher than that for controls and for PCN-exposed animals at the other two salinities. Since hyperosmotic regulation of body fluids is most active at low salinities in this species, we suggest that the PCNs interfere with hyperosmotic regulation and reduce the efficiency of metabolic compensation for hyposmotic shock. The higher energetic cost of acclimation to transient reductions in salinity would be potentially detrimental to wild populations in impacted areas.     

Petroleum contamination and biochemical alterations in oysters (Crassostrea gigas) and plaice (Pleuronectes platessa) from bays impacted by the Amoco Cadiz crude oil spill

Following the Amoco Cadiz crude oil spill in March 1978, marine animals in coastal and estuarine environments along the north shore of Brittany, France became heavily contaminated with crude oil. The resident benthic fauna in the oil-impacted area which survived the spill were severely stressed by the pollution. The objectives of our investigation were to document long-term trends in petroleum hydrocarbon contamination and sublethal stress in oysters and plaice from the estuaries, Aber Benoit and Aber Wrac'h. Oysters in the estuaries accumulated aliphatic and aromatic petroleum hydrocarbons to high levels and remained heavily contaminated for the duration of the 27 month investigation. Plaice, on the other hand, retained only low concentrations of petroleum hydrocarbons in muscle and liver tissue. Nevertheless, the oysters exhibited very few histopathologic and biochemical responses to the oil, whereas the plaice from the estuaries exhibited a variety of sublethal histopathologic and biochemical alterations.     

Acute toxicity of a used chrome lignosulphonate drilling mud to several species of marine invertebrate

The acute toxicity of a used seawater chrome lignosulphonate drilling mud to several species of marine annelids, crustaceans and molluscs was evaluated. The medium density mud (13·4 lb/gal, 1·57 kg/litre) was composed primarily of seawater, bentonite clay, chrome lignosulphonate, lignite, sodium hydroxide and barium sulphate. The toxicity of four mud/seawater preparations was determined. These were the layered solids phase (LSP), the suspended solids phase (SSP), the unfiltered mud aqueous fraction (MAF) and the filtered mud aqueous fraction (FMAF). Four species each of marine annelids and bivalve molluscs and five species of marine crustaceans were evaluated. The median lethal concentration of the MAF (96-h LC₅₀) varied from 32 to > 100% MAF for the different species. The FMAF was slightly less toxic than the MAF. Adult polychaetes, Neanthes arenaceodentata and Ctenodrilus serratus, one-day old juveniles of opossum shrimp, Mysidopsis almyra, and four day zoeae of grass shrimp, Palaemonetes pugio, were the most sensitive to the MAF. Juvenile N. arenaceodentata, adult polychaetes, Ophryotrocha labronica, and three bivalve molluscs were highly tolerant to the MAF. The SSP preparation at concentrations of 10-20 ml/litre was toxic to post-larvae and juveniles of the commercial shrimp, Penaeus duorarum and P. aztecus, respectively. Exposure to the LSP preparation caused greater than 50% mortality amongst adult N. arenaceodentata, juvenile and adult coquina clams, Donax variabilis texasiana and adult scallops, Aequipecten amplicostatus. Other species tested were quite tolerant. A sublethal response observed was the inhibition of reproduction in the marine annelids, Dinophilus sp. and Ctenodrilus serratus. Toxicity of the mud aqueous fractions appeared to be due primarily to volatile soluble organic materials in the extract, whilst that of the SSP and LSP preparations appeared to be due to the smothering action of fine particulates in the mud. Based on the results of this investigation and published observations of solids concentrations in the water column during drilling mud discharge, it is concluded that discharge of a used chrome lignosulphonate drilling mud, such as that used in the present investigation, from offshore platforms is not likely to cause measureable damage to benthic, demersal or pelagic marine animals.     

Field assessment of biochemical stress indices for the sandworm Neanthes virens (Sars)

Certain biochemical stress responses have been observed in the laboratory for Neathhes virens subjected to various environmental and pollutant stressors. The purpose of the present study was to determine whether similar alterations in these biochemical parameters could be detected in a natural population of N. virens from a contaminated site as compared with animals from a nearby reference site. A site in Portland Harbor, Maine, adjacent to an oil storage facility with oil-contaminated sediments was selected as the experimental study area and the reference site was at Pine Point, approximately 15 miles south of Portland.Animals were collected from the two sites on consecutive days on a bimonthly basis at low tide within a day of the full moon from September 1981 through March 1982. Coelomic fluid samples were taken within 2 h after collection and the animals were then frozen in liquid nitrogen for transport back to the laboratory. Coelomic fluid samples were analyzed for glucose and the frozen tissues were analyzed for glycogen, lipid and free amino acid concentrations.Significant differences in these parameters were often observed between the two populations. The glycogen content of animals from the contaminated site was always less than that of animals from the reference site, whereas the lipid levels were always higher. Significant differences between the free amino acid composition of the animals from the two sites were also observed. Although distinct biochemical differences can be detected between these two populations, the considerable biological variation in these parameters may limit their usefulness for field monitoring investigations for this species.     

Azimuthal structures in the wind and chromosphere of the herbig Ae star ab aur. preliminary results from the MUSICOS 1992 campaign

MUSICOS (for MUlti-SIte COntinuous Spectroscopy) is an international project to facilitate and organize world-wide multi-site campaigns in high resolution spectroscopy, in view of obtaining a complete time coverage of various types of variable stellar phenomena.In the framework of this project a vast spectroscopic campaign was organized in December 1992, involving 8 sites well distributed in longitude around the Earth. The observations concerned three scientific programs, among which was the study of azimuthal structures in the wind and chromosphere of the pre-Main-Sequence Herbig Ae star AB Aur.The Hei 5876 line of AB Aur, which is formed in the expanding chromosphere of this star, in the innermost parts of its wind, was monitored at a resolution of 30000, nearly continuously for about 4 days. A spectacular variability of this line was discovered, the profile changing from pure emission to a composite profile including a deep absorption component in the course of a few hours. This variability can be the signature of azimuthal structures in the wind of AB Aur.We present the data collected during the campaign, and discuss possible interpretations of the spectacular variations of the Hei 5876 line.ESA/VILSPAUniversity of British Columbia CanadaBased on observations obtained during the MUSICOS 92 MUlti-SIte COntinuous Spectroscopic campaign from the National Solar Observatory McMath/Pierce 1.5 m, University of Hawaii 2.2 m, Beijing Observatory Xinglong 2.16 m, La Palma 4.2 m William Herschel Telescope, and Observatoire de Haute-Provence 1.52 m telescopes.Presented at the Cosmic Winds and the Heliosphere Conference in Tucson, Arizona, U.S.A., October 18–22, 1993.Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.Visiting Astronomer National Solar Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.     

The combined effect of salinity,temperature and oil on the growth pattern of embryos of the killifish, Fundulus heteroclitus Walbaum

Embryos of the estuarine teleost, Fundulus heteroclitus, were exposed during development to different concentrations of the water-soluble fractions (WSF) of a No. 2 fuel oil under various temperature-salinity combinations. Temperatures and salinities were, respectively: 20, 25 or 30°C and 10, 20 or 30%S. The WSF were extracted from No. 2 fuel oil daily and diluted to concentrations of 15, 20 or 25% of the original mixture. Controls were exposed to seawater without WSF at each temperature-salinity combination.The length of eleutheroembryos was markedly decreased by exposure to WSF. Temperature exerted an effect on growth at low WSF concentrations (0 and 15% WSF) but not at higher ones. The two highest WSF concentrations had a predominant effect on growth that was not further modified by physical factor influences. Conversely, as the WSF exposure increased, the yolk diameter increased, indicating a decreased utilisation of yolk material during development. The mean number of vertebrae in the eleutheroembryos decreased at high WSF concentrations and at high temperatures. Morphological abnormalities consisted predominantly of spinal deformations (scoliosis and lordosis). The data indicate that the survivors of chemical toxicity during embryo development exhibit sublethal responses which would reduce their survival potential in later life.     

Bioerosion by the sea urchin Diadema mexicanum along Eastern Tropical Pacific coral reefs

Bioerosion is a natural process in coral reefs. It is fundamental to the health of these ecosystems. In the Eastern Tropical Pacific (ETP) coral reefs, the most important bioeroders are sponges, bivalves, sea urchins and the fish Arothron meleagris. In the 1980s, El Niño caused high coral mortality and an increase in macroalgal growth. As a result, greater sea urchin bioerosion occurred. This weakened the reef framework. Considering the high vulnerability of the ETP coral reefs, the goal of this study was to determine the current bioerosion impact of the sea urchin Diadema mexicanum along the western coasts of Mexico, El Salvador, Costa Rica and Panamá. The balance between coral bioaccretion and sea urchin bioerosion was also calculated. Between 2009 and 2010, in 12 coral reefs localities, D. mexicanum density, bottom cover and rugosity were quantified along band transects. The daily bioerosion rate was obtained from the amount of carbonates evacuated by sea urchins per unit time. The rate of coral accretion was calculated by multiplying the coral growth rate of the dominant genus by the density of their skeleton and by their specific coral cover. The localities were dissimilar (R = 0.765, P < 0.001) in terms of live coral cover, crustose calcareous algae, turf cover, rugosity index, and density and size of D. mexicanum. At all sites, with the exception of Bahía Culebra (Costa Rica), coral bioerosion was less than coral bioaccretion. Diadema mexicanum plays a dominant role in the balance of carbonates in the ETP, but this depends on reef condition (protection, overfishing, eutrophication) and so the impacts can be either positive or negative.     

The formation of whitings on the Little Bahama Bank

Whitings (patches of suspended fine-grained calcium carbonate) on the Great Bahama Bank (GBB) have been studied since the 1940s. The source and cause of these whitings have been hotly debated for a number of years. Recent studies have shown that resuspension of underlying sediments act as seed crystals for the slow precipitation of CaCO₃. Similar studies have not been conducted on the nearby more northerly Little Bahama Bank (LBB) where satellite photographs indicate the presence of extensive whitings north of the Grand Bahama Island. Research cruises were made to the LBB in July 2003 and May 2005. On board measurements were used to examine the distribution of the components of the carbonic acid system in LBB waters. The distribution of suspended calcium carbonate was also determined and samples of the suspended material and underlying sediments were collected for analyses, including ¹⁴C age determinations.The maximum residence time for waters on the LBB is a little over half (～ 144 d) that on the GBB. A ～ 20% decrease was found in the salinity-normalized titration alkalinity for inner bank waters. This yields a carbonate precipitation rate similar to waters on the GBB. However, unlike the waters in the whitings on the GBB where no changes in carbonic acid system parameters have been detected, large changes in the carbonic acid system parameters were found in the whiting waters of the LBB. These results clearly indicate that active precipitation was occurring in these waters. These observations are interpreted as indicating that there is a much slower mixing of waters associated with whitings and surrounding bank waters on the LBB than on the GBB. The more closed nature of whitings on the LBB makes them better targets for study of the processes taking place in whitings.Suspended carbonate mineralogy and geochemistry closely matched those of the fine-grained portion of the underlying sediments. These results support a close relationship between carbonates found in whitings and those in underlying sediments. This is further evidenced by a similar age for whiting carbonates (～ 700 y) and easily resuspended sediment carbonates (～ 1000 y) and is what was previously observed on the GBB.These observations indicate that the processes leading to whiting formation and associated calcium carbonate precipitation along with changes in water chemistry are quite similar in these two shallow carbonate bank environments in the Bahamas.     

Influence of basin characteristics on baseflow and stormflow chemistry in the Great Smoky Mountains National Park,USA

Relationships between stream chemistry and elevation, area, Anakeesta geology, soil properties, and dominant vegetation were evaluated to identify the influence of basin characteristics on baseflow and stormflow chemistry in eight streams of the Great Smoky Mountains National Park. Statistical analyses were employed to determine differences between baseflow and stormflow chemistry, and relate basin‐scale factors governing local chemical processes to stream chemistry. Following precipitation events, stream pH was reduced and aluminium concentrations increased, while the response of acid neutralizing capacity (ANC), nitrate, sulfate, and base cations varied. Several basin characteristics were highly correlated with each other, demonstrating the interrelatedness of topographical, geological, soil, and vegetative parameters. These interrelated basin factors uniquely influenced acidification response in these streams. Streams in higher‐elevation basins (>975 m) had significantly lower pH, ANC, sodium, and silicon and higher nitrate concentrations (p < 0.05). Streams in smaller basins (<10 km²) had significantly lower nitrate, sodium, magnesium, silicon, and base cation concentrations. In stormflow, streams in basins with Anakeesta geology (>10%) had significantly lower pH and sodium concentrations, and higher aluminium concentrations. Chemical and physical soil characteristics and dominant overstory vegetation in basins were more strongly correlated with baseflow and stormflow chemical constituents than topographical and geological basin factors. Saturated hydraulic conductivity, of all the soil parameters, was most related to concentrations of stormflow constituents. Basins with higher average hydraulic conductivities were associated with lower stream pH, ANC, and base cation concentrations, and higher nitrate and sulfate concentrations. These results emphasize the importance of soil and geological properties influencing stream chemistry and promote the prioritization of management strategies for aquatic resources. Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient execution of the WRF model and other HPC applications in the cloud

There are many scientific applications that have high performance computing (HPC) demands. Such demands are traditionally supported by cluster- or Grid-based systems. Cloud computing, which has experienced a tremendous growth, emerged as an approach to provide on-demand access to computing resources. The cloud computing paradigm offers a number of advantages over other distributed platforms. For example, the access to resources is flexible and cost-effective since it is not necessary to invest a large amount of money on a computing infrastructure nor pay salaries for maintenance functions. Therefore, the possibility of using cloud computing for running high performance computing applications is attractive. However, it has been shown elsewhere that current cloud computing platforms are not suitable for running some of these kinds of applications since the performance offered is very poor. The reason is mainly the overhead from virtualisation which is extensively used by most cloud computing platforms as a means to optimise resource usage. Furthermore, running HPC applications in current cloud platforms is a complex task that in many cases requires configuring a cluster of virtual machines (VMs). In this paper, we present a lightweight virtualisation approach for efficiently running the Weather Research and Forecasting (WRF) model (a computing- and communication-intensive application) in a cloud computing environment. Our approach also provides a higher-level programming model that automates the process of configuring a cluster of VMs. We assume such a cloud environment can be shared with other types of HPC applications such as mpiBLAST (an embarrassingly parallel application), and MiniFE (a memory-intensive application). Our experimental results show that lightweight virtualisation imposes about 5 % overhead and it substantially outperforms traditional heavyweight virtualisation such as KVM.