A comparison of different ranking schemes for assessing the effect of large point sources of pollution in the UK

The availability of national maps of critical loads for soils, vegetation and freshwaters helpsenable the assessment of the effects of large point sources of pollution in the UK. The deposition footprint of most major sources has been modelled and combined in a GIS with a national critical loads database. As part of an integrated pollution control strategy (IPC) it may be helpful to rank point sources in order of their effects on the environment. A comparison of the discriminating power and effectiveness of several ranking schemes has been carried out. A variety of ranking schemes were investigated, such as; total area where sulphur deposition exceeds the critical load or average mass deposited on areas where the critical load is exceeded. Their relative merits were compared for several current and future scenarios, such as, actual 1993 emissions or predicted emissions for 2001. Rankings for the unit emissions provided a measure of the pollution potential of each source and were a complex function of the location of sensitive areas and meteorological conditions. Rankings under other scenarios tended to be dominated by the relative magnitude of the emissions. Comparison between the ranking schemes was made using non-parametric statistics. The comparisons reveal complex interactions between different schemes. The approach is providing practical solutions to a pollution control strategy based on maximising environmental benefits.     

A three-year study of Salmonella dublin infection in a closed dairy herd

Over a period of three years, Salmonella dublin was isolated occasionally from the faeces of nine adult cattle in a closed dairy herd. The organism was also isolated from 12 of the samples collected after parturition; isolations were made from newborn calves on 11 occasions, from a vaginal swab once and from a milk sample once. Nine of the isolations from the calves were made from swabs obtained within 24 hours of birth. Throughout the investigation isolations were made from heifers, steers and older calves and 11 infected animals were detected. S. dublin was widespread in the farm environment and it was concluded that environmental contamination was an important source of infection for animals of all ages, some of which may have become latent carriers. The family history of one cow, seven of whose offspring were infected with S dublin, suggested the possibility of vertical transmission. Without reliable tests to detect latent carriers, it is suggested that control of this infection must be based on improved hygiene and the use of vaccination to improve the immunity of the herd.     

Interspecific comparison of experimental and natural routes of Lepeophtheirus salmonis and Caligus elongatus challenge and consequences for distribution of chalimus on salmonids and therapeutant screening

Although the gills have been reported as a site for settlement by sea lice attached stages in experimental challenges, the prevalence and abundance of infection on gills have not been reported in farmed fish and have been reported only rarely in wild salmonids. Disproportionate attachment to the gills may be significant in evaluation of new therapeutants and this study asks whether the efficacy data from studies of therapeutants based on experimental challenge can be extrapolated to the fish farm arena. The distribution of chalimus on gills, body and fins of farmed first sea year Atlantic salmon were examined in two Scottish sea lochs, each on two occasions (30 fish on each sampling date), fish from one farm with infection with Lepeophtheirus salmonis only and the other farm with exclusively Caligus elongatus. The dorsal fin was the primary attachment site of L. salmonis (50% and 33% in two samples respectively) with 29% and 32% on other fins and 20% and 29% on the body and head. Only one of 56 chalimus (1.8%) and four of 75 chalimus (5.3%) were attached to the gills. In contrast, the chalimus distribution of C. elongatus was predominantly on fins other than the dorsal, including the tail, 74% and 71%, on two sampling occasions, respectively, with only 4.2% and 3.6% of chalimus located on the dorsal fin. The pectoral fins were the most common location with 32%, followed by the tail 23%, pelvic fins 14% and only 3% on the anal fin. None of 287 and 111 chalimus in two samples, respectively, of C. elongatus was attached to the gills. The low abundance of lice on the gills indicated that non‐destructive sampling methods adequately represented lice infection. In three experimental challenges with L. salmonis, the gills were a major attachment location with 19.9–36.3% of chalimus, 9.9–26.9% on the body, 22–27% on the dorsal fin and 19–23% on the other fins. These differences with natural challenge in L. salmonis reported here and also in the literature suggest that the importance of the gills for chalimus location in the experimental model is atypical and an artefact of reduced host swimming speed in tanks that permits copepodids to attach to the gills. In natural infection, the flow over the gills is high and reduced flow is required for copepodid settlement. Greatest reductions (96%) in chalimus bath treated with cypermethrin occurred on the gills with no significant reductions in those located on the dorsal and other fins. It is possible that the efficacy of therapeutants may be higher in chalimus attached to the gills because of the higher concentration encountered of bath therapeutant and extrapolation of efficacy to farms may be misleading and progression to field testing is essential.     

Alternative dietary protein sources for Atlantic salmon (Salmo salar L.) effect on intestinal microbiota,intestinal and liver histology and growth

The present study has addressed the issue of dietary alterations on gut microbiota in fish by investigating modulation of the allochthonous and autochthonous bacterial gut community of Atlantic salmon following feeding with pea protein concentrate, soy protein concentrate, extracted sunflower, poultry by‐product and feather meal. The results revealed that total allochthonous and total autochthonous bacteria isolated from the distal intestine (DI) were affected by dietary modulations. Total autochthonous bacteria in proximal intestine remained unaffected. Corynebacteriaceae dominated the allochthonous bacteria and Lactobacillaceae dominated the autochthonous bacteria community in proximal and DI indicating that the most abundant groups are not shifted by alternative proteins. Some variations were observed between the bacterial communities as result of dietary manipulations. Alternative protein sources resulted in no severe signs of enteritis. Vacuolization of the liver was unaffected by diet. Furthermore, addition of plant materials significantly affected production of acetic acid. Weight of pyloric‐, proximal‐ and DI was influenced by diet, especially feather meal. Growth performance was significantly affected by inclusion of feather meal to the diet. In conclusion the results showed that pea protein concentrate and poultry by‐products are suitable protein replacements for Atlantic salmon and that soy protein concentrate is a potential candidate.     

Estimating the Effect of Abiotic Factors on Modifying the Sensitivity of Vegetation to Nitrogen Deposition: An Application of Endorsement Theory

Many natural and semi-natural vegetation communities are sensitive to eutrophication; most eutrophication is caused by human activities. Critical loads have been developed in Europe to provide an effects-based approach to pollutant abatement including nitrogen deposition. Critical loads to protect ecosystems from eutrophication from excess nitrogen are only specified for very broad habitat types (e.g., ‘dry heaths’) and as a range of values (e.g., between 10 and 20 kg N ha^?1 year^?1). There may be considerable variation in vegetation communities within a broad habitat and there is a requirement (e.g., from conservation agencies, etc.) for more precise critical loads for more clearly specified receptors (habitats, vegetation communities). This paper demonstrates the use of endorsement theory to rationalise incomplete, qualitative and conflicting information on abiotic parameters (e.g., climate, management) that may influence the vegetation response to nitrogen deposition and hence, the critical loads. The endorsement theory approach is tested for 22 heathland community types in the UK (as described by the National Vegetation Classification of Rodwell, Cambridge University Press, vol. 3, 1991) to determine if the critical load for a community should be nearer the upper or lower limit of the published ranges. The results give a ‘confident’ endorsement for one heath community and a ‘likely’ endorsement for a further 13 communities for a critical load at the lower limit. The endorsements suggest that the critical load for most heaths should be at the lower end of the range meaning that current estimates of the exceeded area calculated using the mid-point of the range is an underestimate.