Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters

Concentrations and enantiomeric profiles for a range of organochlorine compounds are reported in blubber samples from a number of individual killer whales (Orcinus orca) from British and Irish waters. Elevated contaminant levels and enriched isotopic ratios were determined in one individual whale sampled in the Scottish Western Isles compared to the others suggesting marine mammal based dietary influences. The potential application of isotopic ratios to model contaminant uptake, enantioselective enrichment and accumulation is demonstrated. Data are presented which provide information on enantioselective enrichment factors (EFs) for o,p'-DDT, alpha-HCH and toxaphene congeners CHB26 and CHB 50. This dataset further improves the current database on reported levels of a number of contaminants and provides additional background information on potential metabolic processes in killer whales from British and Irish waters.     

Changes in octocoral communities and benthic cover along a water quality gradient in the reefs of Hong Kong

Cover of the main reef benthic groups, and abundances and taxonomic richness of octocorals were surveyed in the reefs of Hong Kong, and related to spatial and water quality gradients. Nutrient and particle concentrations are high throughout the area, with concentrations declining from the south towards the north-eastern region. Regression tree analyses showed that hard coral cover was most strongly related to water clarity, that macroalgal cover was highest in areas with high wave action and high water clarity, and that crustose coralline algae were negatively related to sedimentation. Octocoral communities (42 species in 23 genera) were dominated by zooxanthellae-free taxa; those few species with zooxanthellae were restricted to reefs with low wave action and high water clarity in the north-eastern region. The water quality gradient spans from conditions that are marginal for zooxanthellate octocorals while still supporting diverse scleractinian communities, towards an estuarine endpoint where zooxanthellate octocorals cease to exist and hard coral communities are reduced to a few resilient colonies. The data suggest that the types, abundances and richness of zooxanthellate octocorals, and the shift from zooxanthellate to azooxanthellate octocoral communities, may act as useful indicators of water clarity in regions where long-term water quality data are unavailable.     

The response of coastal marshes to sea-level rise: Survival or submergence?

In order to maintain an elevation in the intertidal zone at which marsh vegetation can survive, vertical accretion of the marsh surface must take place at a rate at least equal to the rate of relative sea-level rise. Net vertical accretion of coastal marshes is a result of interactions between tidal imports, vegetation and depositional processes. All of these factors are affected, directly or indirectly, by alterations in marsh hydrology which might occur as a result of sea-level rise. The overall response of coastal marshes to relative sea-level rise depends upon the relative importance of the inorganic and organic components of the marsh soil and the impact of increased hydroperiod on net accumulation. The varied combination of factors contributing to sediment supply, and their complexity at the scale of individual marshes, means that predicting the response of suspended sediment concentration in marsh floodwater to any changes which may occur as a result of sea-level rise, at anything other than the local scale is unlikely to be accurate. The impact of sea-level rise on net below-ground production is also complex. The sensitivity of certain species to waterlogging and soil chemical changes could result in a change in species composition or the migration of vegetation zones. Consequently, predicting the net impact of sea-level rise on organic matter accumulation is fraught with difficulties and requires improved understanding of interactions between vegetation, soil and hydrologic processes.     

Relationship between populations of amphipods and pollution

The composition and distribution of the amphipods inhabiting rocky environments in the French Mediterranean coast have been studied over the past 18 yr with particular emphasis upon pollution. The results from 203 quantitative samples, each consisting of 400 cm² area were analysed as to species, number of specimens, partial dominance, Shannon-Weaver and Margalef Index of diversity and similarity index of Sanders. Included were 35 species of gammarids and 4 species of caprellids which were represented by over 90 000 individuals. An inverse relationship was found to exist between the richness of the population and the degree of pollution. No caracteristic group of species was linked to areas affected by pollution, but certain species were excluded by more severe pollution whereas the number of specimens of some other species increased, a certain balance between two preferential groups as indicated.     

The orbit, mass, and albedo of transneptunian binary (66652) 1999 RZ253

We have observed (66652) 1999 RZ₂₅₃ with the Hubble Space Telescope at seven separate epochs and have fit an orbit to the observed relative positions of this binary. Two orbital solutions have been identified that differ primarily in the inclination of the orbit plane. The best fit corresponds to an orbital period, days, semimajor axis a=4660±170 km and orbital eccentricity e=0.460±0.013 corresponding to a system mass m=3.7±0.4×¹⁰¹⁸ kg. For a density of the albedo at 477 nm is p₄₇₇=0.12±0.01, significantly higher than has been commonly assumed for objects in the Kuiper belt. Multicolor, multiepoch photometry shows this pair to have colors typical for the Kuiper belt with a spectral gradient of 0.35 per 100 nm in the range between 475 and 775 nm. Photometric variations at the four epochs we observed were as large as 12±3% but the sampling is insufficient to confirm the existence of a lightcurve.     

The Effect of Clouds on the Visible Spectra of Extrasolar Giant Planets

Earth, Moon, and Planets -     

Effect of hydrologic management on marsh surface sediment deposition in coastal Louisiana

High rates of coastal land loss in Louisiana have prompted efforts to maintain or restore coastal wetland habitats, and structural management of marsh hydrology is one of a number of approaches that has been adopted. The aim of this study was to determine the effect of hydrologic management measures on marsh-surface sediment deposition in the Mississippi deltaic plain. Four impoundments, ranging in size from 50 ha to 177 ha and similarly sized control sites were included in the study. At each site, marsh-surface sediment traps were collected approximately biweekly for 3.5 yr to measure changes in sediment deposition. There was no significant difference in sediment deposition between any of the impoundment and control sites during the premanagement period. The results show no significant difference in marsh-surface sediment deposition between management year 1992–1993 and management year 1994–1995, but management year 1993–1994 had significantly lower sediment deposition than either the first or the last year of the study. Management year 1992–1993 showed the highest sediment deposition when it was assessed across all basins, areas, and sites, and this high rate of deposition is accounted for by the impact of Hurricane Andrew. For all management years there were significant differences between impoundment and control sites, with control sites showing higher rates of marsh surface sediment deposition than impoundments. No clear pattern was identified concerning the influence of various types of hydrologic management on rates of sediment deposition. This reduction in sediment deposition indicated that the areas under management in this study are receiving insufficient inorganic sediment deposition to keep pace with sea-level rise.     

Patterns of sediment deposition in subsiding coastal salt marshes,Terrebonne Bay,Louisiana: The role of winter storms

High rates of wetland loss in the Mississippi deltaic plain have been attributed to a combination of insufficient marsh sedimentation and relative sea-level rise rates of over 1.2 cm yr^?1. This study examines contemporary patterns of sediment delivery to the marsh surface by evaluating the contribution of individual marsh flooding events. Strong meteorological effects on water level in Terrebonne Bay often mask the usual microtidal fluctuations in water level and cause flood events to be of unpredictable frequency and duration. Sediment deposited on the marsh surface was collected weekly at two sites. Preliminary results allow the relative contributions of tidal and storm inundations to be calculated. Maximum sedimentation is associated with strong southerly winds both causing increased flooding and mobilizing sediment from open bay areas. Sediment deposition is limited by the availability of suspended sediment and the opportunity for its transport onto the marsh surface.     

Understanding salt-marsh accretion,Scolt Head Island,Norfolk, England

Measurements of surface sediment accretion have been obtained for Hut Marsh, Scolt Head Island, Norfolk, England, using sand marker horizons. More than eighty 1-m² marker sites were deployed in October 1983, and vertical accretion measured at them in April and October 1986 and April 1987. Elevations relative to Ordnance Datum were established by levelling each site at the time of deployment. Data collected by Steers between 1935 and 1957 on the same marsh show a clear relationship between marsh elevation and sedimentation. The results of the current more detailed study, presented as mean annual accretion rates, indicate a complex pattern of sediment distribution at this macrotidal location. These data, together with the results of tidal flow monitoring in the creeks on Hut Marsh, show the importance of spatial and temporal patterns of sediment delivery and variations in depositional processes in determining the distribution of sedimentation across the marsh surface.     

Ratio of the Core to the Extended Emissions in the Comoving Frame for Blazars

In a two-component jet model, the emissions are the sum of the core and extended emissions: \(S^{\mathrm{ob}}=S_{\mathrm{core}}^{\mathrm{ob}}+S_{\mathrm{ext}}^{\mathrm{ob}}\), with the core emissions, \(S_{\mathrm{core}}^{\mathrm{ob}}= f S_{\mathrm{ext}}^{\mathrm{ob}}\delta ^{q}\) being a function of the Doppler factor \(\delta \), the extended emission \(S_{\mathrm{ext}}^{\mathrm{ob}}\), the jet type dependent factor q, and the ratio of the core to the extended emissions in the comoving frame, f. The f is an unobservable but important parameter. Following our previous work, we collect 65 blazars with available Doppler factor \(\delta \), superluminal velocity \(\beta _{\mathrm{app}}\), and core-dominance parameter, R, and calculated the ratio, f, and performed statistical analyses. We found that the ratio, f, in BL Lacs is on average larger than that in FSRQs. We suggest that the difference of the ratio f between FSRQs and BL Lacs is one of the possible reasons that cause the difference of other observed properties between them. We also find some significant correlations between \(\log f\) and other parameters, including intrinsic (de-beamed) peak frequency, \(\log \nu _{\mathrm{p}}^{\mathrm{in}}\), intrinsic polarization, \(\log P^{\mathrm{in}}\), and core-dominance parameter, \(\log R\), for the whole sample. In addition, we show that the ratio, f, can be estimated by R.