John O'Halloran

Stocking density, growth and growth variation in juvenile turbot, Scophthalmus maximus (Rafinesque)

Abstract Although high stocking densities of turbot have been achieved in culture using supplementary oxygenation, this rearing strategy ignores the possibility that high densities may interfere with behavioural interactions between individuals and thereby affect biomass gain. This study describes the effect of stocking density on the growth of juvenile turbot populations. Groups of juvenile turbot were reared at four different densities (initial densities: 0.7, 1.1, 1.5 and 1.8 kg/m 2 ) for 45 days. Treatment density had a significant effect on turbot growth rates over the experimental period. Fish held at the highest density showed lower growth rates and mean weights at the conclusion of the study than fish held at lower densities. The dispersion in fish weights was also affected by stocking density. The variation in fish weights was greatest in the highest density group and as stocking densities increased the growth of some individuals was suppressed. It is concluded that growth of juvenile turbot can be significantly increased and more homogeneous weights achieved by stocking the fish at lower densities than previously reported.

Assessment of a glutathione S-transferase and related proteins in the gill and digestive gland of Mytilus edulis (L.), as potential organic pollution biomarkers

The response of the glutathione S-transferase (GST, EC 2.5.1.18) and related proteins of Mytilus edulis to environmental pollution load was assessed. Mussels were reciprocally transplanted between an industrial estuary (Douglas), a rural estuary (Youghal) and a m arine site (Bantry). In addition, m ussels were sam pled along a pollution gradient in an estuary receiving leather tannery effluent (Colligan). These latter m ussels were previously shown to be subject to oxidative stress resulting from the discharges. GST specific activity of cytosolic extracts from the gill and digestive gland tissues was determ ined for all anim als. Specific activity was shown to vary significantly in anim als from different sites, with highest specific activity always observed in sam ples (local and transplanted) taken from the industrial site. By com parison, the m ussels exposed to tannery discharges displayed no significant alteration in GST specific activity. Total intracellular glutathione (GSH) was also determ ined for sam ples taken from the Douglas and Youghal estuaries but no correlation with pollution load was observed. Using FPLC analysis, we observed no specific effect on the relative levels of the GST and the individual GST related proteins in gill or digestive gland sam ples from local or reciprocally transplanted anim als from Douglas or Youghal. The increase in GST specific activity observed in samples from the industrial estuary are indicative of a possible, specific inductive agent at this site. The results from the tannery site, by com parison, indicate that general oxidative stress does not result in elevated G ST specific activity in M. edulis.The response of the glutathione S-transferase (GST, EC 2.5.1.18) and related proteins of Mytilus edulis to environmental pollution load was assessed. Mussels were reciprocally transplanted between an industrial estuary (Douglas), a rural estuary (Youghal) and a m arine site (Bantry). In addition, m ussels were sam pled along a pollution gradient in an estuary receiving leather tannery effluent (Colligan). These latter m ussels were previously shown to be subject to oxidative stress resulting from the discharges. GST specific activity of cytosolic extracts from the gill and digestive gland tissues was determ ined for all anim als. Specific activity was shown to vary significantly in anim als from different sites, with highest specific activity always observed in sam ples (local and transplanted) taken from the industrial site. By com parison, the m ussels exposed to tannery discharges displayed no significant alteration in GST specific activity. Total intracellular glutathione (GSH) was also determ ined fo...

Identification of Novel Mutations in the Ryanodine-Receptor Gene (RYR1) in Malignant Hyperthermia: Genotype-Phenotype Correlation

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that is triggered in genetically predisposed individuals by common anesthetics and muscle relaxants. The ryanodine receptor (RYR1) is mutated in a number of MH pedigrees, some members of which also have central core disease (CCD), an inherited myopathy closely associated with MH. Mutation screening of 6 kb of the RYR1 gene has identified four adjacent novel mutations, C6487T, G6488A, G6502A, and C6617T, which result in the amino acid alterations Arg2163Cys, Arg2163His, Val2168Met, and Thr2206Met, respectively. Collectively, these mutations account for 11% of MH cases and identify the gene segment 6400-6700 as a mutation hot spot. Correlation analysis of the in vitro contracture-test data available for pedigrees bearing these and other RYR1 mutations showed an exceptionally good correlation between caffeine threshold and tension values, whereas no correlation was observed between halothane threshold and tension values. This finding has important ramifications for assignment of the MH-susceptible phenotype, in genotyping studies, and indicates that assessment of recombinant individuals on the basis of caffeine response is justified, whereas assessment on the basis of halothane response may be problematic. Interestingly, the data suggest a link between the caffeine threshold and tension values and the MH/CCD phenotype.

The role of bivalve molluscs as tools in estuarine sediment toxicity testing: a review

Estuarine sediments frequently are repositories and therefore potential sources of anthropogenic contaminants. Many organic and metallic chemical compounds released into aquatic systems bind to particulates and so accu- mulate in the sediments, thus, sediments become repositories of contaminants in estuaries. These may also cause contamination through diffusion of porewater, resuspension of particulates and dispersal of benthic fauna. There is a need to assess the biological affects of these anthropogenic contaminants because they may be toxic to infauna and bottomfish. Sediment toxicity bioassays are a means for carrying out such an assessment and primarily provide data on toxicity by measuring the effects on the test organism. Existing sediment toxicity bioassays rely on a battery of aquatic toxicity tests, which are based on the extraction of pore water, and elutriate from sediments and then subjecting these sediment phases to toxicity testing regimes. Two estuarine bivalve molluscs, Scrobicularia planaand Tapes semidecussatuswere used to assess the ecotoxicity of field-collected sediments from estuarine and coastal areas around the Irish and English Coast over a 3-year study period. A variety of endpoints were measured during the study including survival in air, behaviour, animal condition, biochemistry, soft tissue metal concentrations, lysosomal membrane integrity and histopathology. Of these endpoints, the most sensitive were survival, survival in air, lysosomal membrane integrity, behaviour and histopathology.

Shellfish toxicity: human health implications of marine algal toxins

Five major human toxic syndromes caused by the consumption of shellfish contaminated by algal toxins are presented. The increased risks to humans of shellfish toxicity from the prevalence of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from anthropogenic activities, especially increased eutrophication, marine transport and aquaculture, and global climate change. Improvements in toxin detection methods and increased toxin surveillance programmes are positive developments in limiting human exposure to shellfish toxins.

Chromium speciation in tannery effluent—II. Speciation in the effluent and in a receiving estuary

Abstract The forms and transformations of chromium were characterised in the effluent of an Irish tannery before and after discharge into an estuary. The three primary effluent streams in the tannery were studied, i.e. the chrome and sulphide streams and the final composite effluent. Chromium was fully speciated in the final effluent, the discharge plume, and in the estuary outside discharge periods. The partitioning of chromium was also studied in the sediments, and transformations due to the remobilisation and oxidation of Cr(III) were followed. These data were compared to a reference site. Mixing of the chrome and sulphide streams resulted in the binding of Cr(III) to organic ligands, notably proteins. The speciation of chromium in the final effluent was dominated by Cr(III) particulates with a mean concentration of 72.4 mg Cr 1 −1 . Some 80–90% of these particulates were inorganic while 10–20% were bound to organic ligands. Dissolved concentrations averaged 3.6 mg 1 −1 at pH 10. However, a 45% fall in dissolved Cr(III) was recorded after lowering the pH of the final effluent to that of the receiving waterway, i.e. pH 7.6–8.1. Approximately 50% of the remainder was determined to be bound to proteinaceous ligands with 50% bound to stable organic ligands. However, only the latter species was detectable in the water column outside discharge periods. Low levels of dissolved organic Cr(III) were also found to leach from both control and contaminated sediments, although concentrations were higher in the contaminated sediments. Cr(VI) was undetectable in the estuary ( −1 ) and local sediments were found not to oxidise Cr(III) in the effluent. In comparison, a number of sediments obtained from other sites readily oxidised experimentally added Cr(III) in the tannery effluent matrix. Elevated levels of organic and inorganic chromium in suspended solids were detectable at all sites studied in the contaminated estuary. Sediment Cr concentrations corrected for grain size were also elevated at all sites with highest concentrations being associated with fine grain sediments. However, total Cr concentrations in the sediments were relatively low compared to other tannery contaminated sites due to good dispersion of the effluent in the estuary.

Chromium speciation in tannery effluent—I. An assessment of techniques and the role of organic Cr(III) complexes

Abstract Three methods of chromium speciation were assessed in relation to possible interferences from Cr(III)-organic complexes. They were, namely: 1,5-diphenyl-carbazide (DPC) spectrophotometry, organic extraction with methyl isobutyl ketone (MIBK) and co-precipitation with iron and bismuth salts. Initially, a number of organic ligands, i.e. proteins, amino acids and organic acids were reacted with Cr(III) and only those complexes with solubility levels above that of ionic Cr(III) were assessed further. The spectrophotometric method was found to suffer minor interferences which were attributable to a non-specific turbidity effect. In comparison, two methods of MIBK extraction were found to suffer severe interferences with Cr(III)-protein complexes. Also, co-precipitation with iron salts resulted in high levels of contamination by Cr(III)-organic complexes in the ionic chromium fractions. Due to the poor solubility of bismuth salts, this method was discarded. The results demonstrate that chromium speciation in the presence of organic complexes can lead to erroneous results. However, with recognition of the presence of such complexes, corrections can be made. Since the co-precipitation behaviour of organic Cr(III) appears to be relatively specific, a scheme is described for the speciation of Cr(III) in tannery contaminated waterways. In addition, it is recommeded that a separate determination of Cr(VI) is conducted using a modification of the DPC method.

Variability of heat shock proteins and glutathione S-transferase in gill and digestive gland of blue mussel, Mytilus edulis

Glutathione S-transferase (GST) and heat shock proteins (hsps) 40, 60, 70 and 90 were determined by immunoblotting using actin as an internal control in Mytilus edulis from one station outside (site1) and three stations within (sites 2-4) Cork Harbour, Ireland. Comparisons were made between gill and digestive gland and between sites. Gill shows generally higher hsp 60, 70 and 90 while digestive gland has higher hsp 40. Site 1 showed higher gill hsps 40 and 70 than sites 2-4 while gill GST was higher in sites 3 and 4 than 1 and 2. Comparison with sites in the North Sea (site 5: outside Tjärnö in The Koster archipelago in the Skagerack) and Baltic Sea (site 6: Askö island) also revealed lower hsps 40 and 70 in site 6 (low salinity) than site 5 (high salinity) although hsps 60, 70 and 90 were detectable in digestive gland unlike sites 1-4. Previously, only hsp 70 had been studied at these sites [Mar. Environ. Res. 39. (1995), 181]. At the mRNA level, gill hsp 70 is 80-fold higher at Tjärnö than Askö. These data suggest that, while salinity may slightly decrease hsp 40 and 70, both hsp 70 and GST are selectively up-regulated by approx. 10- and 3-fold, respectively, at Tjärnö compared to the other sites which we attribute to exposure to more widely fluctuating pollution levels.

Effects of growth stage and tree species composition on breeding bird assemblages of plantation forests

Capsule Bird species assemblages are strongly dependent on growth stage and forest structure, but do not appear to be greatly affected by tree species composition. Aims To investigate changes in bird species composition of plantation forests in relation to crop tree species and forest growth stage. Methods We surveyed populations of birds in 44 plantation forests throughout Ireland in the summers of 2001 and 2002. Our study sites represented three combinations of tree species (pure Sitka Spruce Picea sitchensis, pure Ash Fraxinus exelsior, and Sitka Spruce/Ash mixed at inter-stand level) at five ages (4–8 years, 9–17 years, 23–29 years, 35–50 years and 50+ years). We used ordinations and indicator species analyses to explain the influence of growth stage and tree species composition on the bird assemblages of these forests. Results Bird species assemblage is dependent on growth stage. Changes in bird species composition over the commercial forest cycle are related to shrub layer and proximity to the forest edge. The bird assemblages of pre-canopy closure forests are typical of open habitats, some of the constituent bird species being of conservation concern within Ireland. As forests mature, these are replaced by commoner, more generalist species. We found no significant effect of tree species on bird species assemblage. Possible reasons for this include the relatively narrow range of tree species mixtures studied, and the paucity of forest specialist birds in Ireland. Conclusions Forest management for bird diversity in Ireland should promote the shrub layer in and around forest plantations, and ensure that new afforestation does not take place in areas with diverse communities of open-habitat birds. Opportunities for Irish forest plantations to provide habitat for bird forest specialists may be limited.

The ecology of dippers Cinclus cinclus (L.) in relation to stream acidity in upland Wales: time-activity budgets and energy expenditure

SummaryThe time-activity budget and energy expenditure of a riverine bird, the dipper Cinclus cinclus, was studied from March 1988 to July 1989, across a range of streams of contrasting acidity in upland Wales. Differences in time-activity budgets of birds on acidic and circumneutral streams were consistent with documented differences in prey availability and diet. Birds spent a significantly greater proportion of their active day foraging, swimming and flying, and less time resting, on acidic streams. Activity measurements varied significantly through the year, through the day, and with river flow. Despite differences in time budgets, mean Daily Energy Expenditure (DEE) on acidic streams was only 4.5–7.0% greater than on circumneutral streams. However, rates of energy gain were greater for dippers on circumneutral streams for every month of the year, a pattern confirmed by differences in body condition. By spending more time feeding, dippers on acidic streams will have less time for other activities such as self-maintenance and predator surveillance; they may also be less able to meet the additional demands accompanying the initiation of breeding. These findings are discussed in relation to the feeding ecology and breeding performance of dippers on streams of contrasting water quality in upland Wales.