An inventory of factors that affect polysaccharide production by Phaeocystis globosa

Phaeocystis material contains polysaccharides that are built from at least eight different monosaccharides. Differences have been reported between the carbohydrate composition of different Phaeocystis species, and also between samples taken from Phaeocystis globosa blooms in different areas. In order to elucidate factors that could play a role in determining variation in carbohydrate composition and production, a number of Phaeocystis globosa strains were studied under laboratory conditions. Although there was a clear distinction of a northern and a southern cluster in the Phaeocystis globosa strains based on RAPD analysis, the differences in the composition of the mucopolysaccharides were relatively small. The contribution of glucose, however, ranged from 7–85% of total sugars. A strain that was cultured in seawaters of diverse origin produced polysaccharides of a different composition, suggesting the effect of environmental factors. The presence of bacteria affected neither the amount, nor the composition of the carbohydrates that were produced by Phaeocystis globosa. Glucose is part of both the intracellular polysaccharide pool and of the mucopolysaccharides in the colony matrix. Using specific digestion of the intracellular chrysolaminaran by laminarinase, the distribution of polysaccharides over different pools could be assessed. During growth of an axenic, mucus-producing strain, the portion of glucose present as chrysolaminaran appeared to increase. The polyglucose that was not digested by laminarinase remains unidentified. This study shows that environmental factors rather than strain differences determine differences in the sugar composition of Phaeocystis globosa, especially with respect to the glucose content of the material. A difference in the contribution of glucose could be correlated to the portion of cells in the culture that are not in the colonies. Our study emphasises that for studying polysaccharide dynamics in Phaeocystis globosa it is important to be able to discriminate between the different polysaccharide pools. Preliminary results of an enzymatic approach were promising     

Variability in concentration of suspensates in an estuarine environment

Three data sets of suspensate concentrations, collected under different sampling plans, were analyzed to develop a minimal sampling period, consistent with a predetermined precision. Individual samples collected during any part of a given day were within ±50% of the daily average. In the main channel of the estuary, a monthly sampling scheme closely approximated a weekly pattern; however, seasonal sampling was unsatisfactory. Outside the main channel, weekly, monthly, and seasonal sampling patterns did not differ greatly. Variability in suspensate concentrations must be considered when calculating sediment flux in estuarine and coastal waters.     

Tectonics at the intersection of the East Pacific Rise with Tamayo Transform fault

During the Fall of 1979, a manned submersible program, utilizing DSRV ALVIN, was carried out at the intersection of the East Pacific Rise (EPR) with the Tamayo Transform boundary. A total of seven dives were completed in the vicinity of the EPR/Tamayo intersection depression and documented the geologic relationships that characterize the juxtaposition of these types of plate boundaries. The young volcanic terrain of the EPR axis can be traced into and across the Tamayo Transform valley but becomes buried by sedimentary talus that is being shed from sediment scarps along the unstable sediment slope that defines the north side of the intersection depression. Within 4 km of the transform boundary, the dominant trend (000°) of the fissures and faults that disrupt the rise-generated volcanics is markedly oblique to the regional direction of sea floor spreading (120°). Since no evidence was found to suggest that these structures accommodate significant amounts of strike-slip displacement, they are taken to reflect a distortion of the EPR extensional tectonic regime by a transform generated shear couple. The floor of the Tamayo Transform valley in this area is inundated by mass-wasted sediment, and the principal transform displacement zone is characterized at the surface by a narrow (<1.5 km) interval of fault scarps in sediment that trends parallel with the transform valley. Extrapolated to the west, this zone links with zones of transform deformation investigated during earlier submersible studies (CYAMEX and Pastouret, 1981). Evidence of low-level hydrothermal discharge was seen at one locality on the EPR axis and at another 8 km west of the axis at the edge of the zone of transform deformation.     

Semisubmersible response to transient ice forces

The paper presents an analytical and experimental study on the transient response of semisubmersibles to bergybit impact and the strength of bergybit ice to high strain-rate loadings. Two approaches have been proposed for the solution of the semisubmersible-bergybit interaction problem, one using the energy approach and the other using the conventional structural dynamics approach with initial velocity conditions. In addition the local behaviour of the impacted regions have been analysed for deformation and failure. Numerical results have been given for local behaviour of an impacted column and global behaviour of semisubmersible-bergybit system. Experimental study has been reported on the impact strength of iceberg ice at strain rates of 10⁻³, 10⁻² and 10⁻¹; the indentation impact strength of ice is found to be 3–4 times the unaixial compressive strength, at the same strain rate.     

Production of the Crab Elamenopsis kempiHymenosomatidae in the Garmat-Ali Region, Basrah, Iraq

Abstract. The production of the hymenosomatid crab Elamenopsis kempi was calculated for a period of 18 months from a subtidal area of the Garmat-Ali river, southern Iraq. The highest average individual somatic energy was attained in spring. Maximum population biomass and production were attained by the summer cohort and the minimum values were exhibited by the overwintering cohort. The fluctuations of the average population biomass were followed throughout the sampling period. Average total annual population production was 13.2 g DW · m^-2· a^-1 and the P/B ratio was 5.9. These values were compared with those of the most common crustaceans in the region.     

Benthic Nutrient Recycling in Port Phillip Bay, Australia

Benthic chamber measurements of the reactants and products involved with biogenic matter remineralization (oxygen, ammonium, nitrate, nitrite, phosphate, silicate, TCO₂and alkalinity) were used to define solute exchange rates between the sediment and overlying water column of Port Phillip Bay, Australia. Measurements at various sites throughout the bay, conducted during the summers of 1994 and 1995, indicate that the variability in flux values within a site is comparable to year-to-year variability (±50%). Four regions of the bay were distinguished by sediment properties and the northern region was identified as having 3–30 times greater nutrient regeneration rates than the other regions. Benthic recycling accounted for 63 and 72% of the annualized N and P input, respectively, to the entire bay as determined by summing benthic, dissolved riverine, atmospheric and dissolved effluent sources. However, bay-wide sedimentary denitrification accounted for a loss of 63% of the potentially recyclable N. This fraction is higher than many other coastal regions with comparable carbon loading. Denitrification efficiency is apparently not enhanced by benthic productivity nor by bio-irrigation. The rate of bio-irrigation is negatively correlated with denitrification efficiency. Bio-irrigation was studied using radon-222 and CsCl spike injection chamber measurements. Radon fluxes from sediments in Port Phillip Bay were enhanced over the diffusive flux by 3–16 times. The modelled rate of loss of Cs from chamber water was positively correlated with radon flux enhancement results. Both methods identify regions within Port Phillip Bay that have particularly high rates of non-diffusive pore-water overlying water solute exchange.     

A Linear Programming Model for Seabed Oil-Gas Pipe Network

This paper analyzes the pipe network system of oil-gas collection and transportation foroffshore oilfield development.A"0-1"integer linear programming model is constructed to optimize theinvestment of seabed pipe network.The mathematical model is solved by the spanning tree method ofgraph theory and network analysis.All spanning trees of a network graph compose all the feasible solu-tions of the mathematical model.The optimal solution of the model is the spanning tree with the minimumcost among all spanning trees.This method can be used to optimize the seabed pipe network system andgive a minimum cost plan for the development of offshore marginal oilfield groups.     

Thickness of the mixed bottom layer in the Northern Atlantic

The thickness of the mixed bottom boundary layer (BBL) has been analyzed based on the CTD data at transoceanic sections in abyssal waters of the Northern Atlantic. The measurements were carried out at two transoceanic sections approximately along 48° N (ASV-99) and 5° N (AI-2000) in 1999 and 2000. These data, and the WOCE data obtained at four zonal sections (AR7E and AR12 along 57° N, AR01 along 24.5° S, and A06 along 7.5° N), were used for the calculation of the statistical characteristics of the BBL??s thickness H _B . The probability distribution function F(H _B ) was close to lognormal. The mean value ??H _B ?? at different latitudes was in the range from 30 to 60 m. The averaged BBL thickness = 46.1 m. The BBL??s thickness was about 1% of the ocean??s depth D; the ratio H _B /D was the minimum (0.8%) near the equator and increased up to 1.6% in the polar latitudes.