Random-Lag Singular Cross-Spectrum Analysis

We compare the distribution of stars of different spectral types, and hence mean age, within the central SMC and find that the asymmetric structures are almost exclusively composed of young main-sequence stars. Because of the relative lack of older stars in these features and the extremely regular distribution of red giant and clump stars in the SMC central body, we conclude that tides alone are not responsible for the irregular appearance of the central SMC. The dominant physical mechanism in determining the current-day appearance of the SMC must be star formation triggered by a hydrodynamic interaction between gaseous components. These results extend the results of population studies (see Gardiner & Hatzidimitriou) inward in radius and also confirm the suggestion of the spheroidal nature of the central SMC based on kinematic arguments (Dopita et al.; Hardy, Suntzeff, & Azzopardi). Finally, we find no evidence in the underlying older stellar population for a "bar" or "outer arm," again supporting our classification of the central SMC as a spheroidal body with highly irregular recent star formation.     

Toxicity of chromated copper arsenate (CCA)-treated wood to non-target marine fouling communities in Langstone Harbour, Portsmouth, UK

The effect of the anti-marine-borer timber preservative chromated copper arsenate (CCA) (a pressure impregnated solution of copper, chromium and arsenic compounds) on non-target marine fouling animals was investigated during a subtidal exposure trial. Panels of Scots pine treated to target retentions of 12, 24 and 48 kg CCA per m-3 of wood, plus untreated controls were submerged at a coastal site on the south coast of the UK for 6, 12 and 18 months. After each exposure period the fouling communities that formed on the surface of panels were assessed both qualitatively and quantitatively. Community structure was similar on panels treated to the three CCA loadings, but was significantly different from community structure on untreated panels. The total number of species (species richness) was similar on all panels, although the number of individual organisms attached to the surface of panels was significantly higher on CCA-treated panels than on untreated panels. k-dominance curves revealed that the difference in numbers of individuals between CCA-treated and untreated panels was caused by higher numbers of the dominant species (Elminius modestus, Hydroides ezoensis, and Electra pilosa) on CCA-treated panels. Other species were present in similar numbers on panels of all treatments. Results indicate that there are no detrimental toxic effects to epibiota caused by the presence of CCA preservative within the matrix of the wood at any of the treatment levels. Differences in community structure between CCA-treated and untreated panels may be due to enhanced larval settlement on CCA-treated timber by some species as a result of modifications to the surface properties of the timber by the CCA preservative.     

The effects of biological fouling control at coastal and estuarine power stations

The use of low levels of oxidants as antifouling agents in coastal and estuarine power station cooling water circuits can give rise to concerns over the likely production of chlorination byproducts (CBPs) including organohalogens, of largely cryptic identity, loading and impact. In order to review the current understanding of the degree of impact involved this paper describes a recent collaborative programme of work on CBPs within the wider context of a number of allied studies on power station cooling water entrainment and discharge effects. Bromoform was the single most important CBP found in coastal power station effluents. Although bromoform was found to accumulate in the liver of the sea bass Dicentrarchus labrax (L.) continuously exposed to a chlorinated effluent stream, no otherwise untoward impact on continuously exposed individuals was discerned. Populations of the common blue mussel Mytilus edulis L., likewise exposed, exhibited two responses: a high degree of genoplasticity and the evolution of stress proteins--although both may have been due to thermal rather than toxic stress. Experiments on plankton that simulated the conditions of entrainment within cooling water systems isolated the influence of oxidant usage, with mortality varying between taxa and life stage. The results suggest a very limited impact of oxidant use and the associated CBPs on receiving waters both in terms of plume toxicity or any more widespread ecotoxicological influence. Instead, it is in combination with applied temperature (DeltaT), pressure and the other stressors involved in entrainment within the power station cooling water circuits themselves that an impact is most marked.