Responses of the mussel Mytilus edulis to copper and phenanthrene: Interactive effects

Most investigations of the responses of marine organisms to xenobiotics have concentrated on single contaminants and little is known of possible interactive effects of different classes of xenobiotics. As these latter seldom occur in environmental isolation, it is important to understand any interactions (synergistic or antagonistic) which may occur. This problem has been approached in the mussel Mytilus edulis by exposing estuarine mussels to copper (20 μg litre⁻¹) and phenanthrene (100 μg litre⁻¹) both individually and in combination, and measuring cytochemical subcellular and physiological responses after 3 days exposure and 3 days and 12 days recovery period. Results showed that mussels accumulated both xenobiotics during 3 days exposure. Depuration of copper was complete in 3 days recovery period, while loss of phenanthrene ranged from 30% to 70% of the concentration reached after 3 days exposure. There were no interactive effects on depuration.Both copper and phenanthrene reduced lysosomal hydrolase latency in digestive cells, and copper appeared to have a synergistic effect in preventing recovery of latency of lysosomal N-acetyl-β-hexosaminidase during the recovery period. There was evidence, in the digestive cells, of an antagonistic effect of copper on stimulation of activity of the microsomal respiratory chain (measured as NADPH-neotetrazolium reductase) by phenanthrene. Stimulation of this system by phenanthrene persisted after 12 days recovery period. There was a synergistic interaction of copper and phenanthrene on elevation of oxygen consumption and ammonium excretion. Clearance rates and scope for growth (physiological condition) were depressed by copper but not by phenanthrene after 3 days exposure.These findings are discussed in terms of known effects of copper and phenanthrene and the interactions are considered in terms of environmental effects measurements.     

Beta diversity of tropical marine benthic assemblages in the Spermonde Archipelago, Indonesia

In order to preserve diversity it is essential to understand how assemblages change across space. Despite this fact, we still know very little about how marine diversity is spatially distributed, especially among lesser‐studied invertebrate taxa. In the present study beta‐diversity patterns of sea urchins, sponges, mushroom corals and larger foraminifera were assessed in the Spermonde Archipelago (Indonesia). Using ordinations we showed that the inshore zone (<5 km offshore), midshore zone (5 < x < 30 km offshore) and distance offshore zone (>30 km offshore) all contained distinct assemblages of sponges and corals, while only foraminifera assemblages from the inshore (<5 km offshore) zone were distinct. There was a significant spatial pattern of community similarity for all taxa surveyed, but this pattern proved to be wholly related to environmental variables for sponges and foraminifera, and primarily for mushroom corals and sea urchins. The lack of a pure spatial component suggests that these taxa may not be dispersal limited within the spatial scales of this study (c. 1600 km²). The analyses of the corals and foraminifera were additionally tested at two spatial scales of sampling. Both taxa were primarily associated with local‐scale environmental variables at the local scale and larger‐scale variables at the larger scale. Mean inter‐plot similarity was also higher and variation lower at the larger scale. The results suggest that substantial variation in similarity can be predicted using simple locally assessed environmental variables combined with remotely sensed parameters.     

A scenario-based risk framework for determining consequences of different failure modes of earth dams

Natural Hazards - Failure modes for earth dams are extensively reviewed and analysed using a three-pronged approach including a literature review, physical observations of a representative earth...     

Impact of sampling depth and plant species on local environmental conditions, microbiological parameters and bacterial composition in a mercury contaminated salt marsh

We compare the environmental characteristics and bacterial communities associated with two rushes, Juncus maritimus and Bolboschoenus maritimus, and adjacent unvegetated habitat in a salt marsh subjected to historical mercury pollution. Mercury content was higher in vegetated than unvegetated habitat and increased with sampling depth. There was also a significant relationship between mercury concentration and bacterial composition. Habitat (Juncus, Bolboschoenus or unvegetated), sample depth, and the interaction between both, however, explained most of the variation in composition (~70%). Variation in composition with depth was most prominent for the unvegetated habitat, followed by Juncus, but more constrained for Bolboschoenus habitat. This constraint may be indicative of a strong plant-microbe ecophysiological adaptation. Vegetated habitat contained distinct bacterial communities associated with higher potential activity of aminopeptidase, β-glucosidase and arylsulphatase and incorporation rates of (14)C-glucose and (14)C-acetate. Communities in unvegetated habitat were, in contrast, associated with both higher pH and proportion of sulphate reducing bacteria.     

Seasonal and spatial variation in lipid and triacylglycerol levels in juvenile chinook salmon (Oncorhynchus tshawytscha) from the Bridge River, British Columbia

Triacylglycerols (TAGs) are the primary form of energy storage in fish, but little work has been done on the dynamics of TAG storage and use in relation to environmental conditions. We sampled age-0 chinook salmon (Oncorhynchus tshawytscha) in two reaches of a regulated river in British Columbia, Canada that had different discharge regimes. During the summer, fish from the reach with high freshet flows grew more slowly and had lower TAG levels than those from the reach with lower and more stable flows. In addition, smaller individuals had lower TAG levels than larger ones. We suggest that in the reach with higher flows fish were unable to obtain sufficient surplus energy for somatic growth and lipid storage. In the fall, when flows were lower, TAG storage increased and the proportion of total lipids that were TAGs were similar for both small and large fish. The allocation of energy to TAG stores was likely a strategy to ensure individuals had sufficient energy for overwintering. Our results suggest that individual-based variation in TAG levels may be sensitive to environmental factors and can be used as a measure of fish condition and performance, but more work is needed to fully understand lipid dynamics in seasonally and spatially variable rearing environments.     

Sedimentological and palaeoenvironmental study from Waregi Hill in the Hiwegi Formation (early Miocene) on Rusinga Island,Lake Victoria,Kenya

Palaeontological deposits on Rusinga Island, Lake Victoria, Kenya, provide a rich record of floral and faunal evolution in the early Neogene of East Africa. Yet, despite a wealth of available fossil material, previous palaeoenvironmental reconstructions from Rusinga have resulted in widely divergent results, ranging from closed forest to open woodland environments. Presented here is a detailed study of the sedimentology and fauna of the early Miocene Hiwegi Formation at Waregi Hill on Rusinga Island, Kenya. New sedimentological analyses demonstrate that the Hiwegi Formation records an environmental transition from the bottom to the top of the formation. Lower in the Hiwegi Formation, satin-spar calcite after gypsum in siltstone deposits are interpreted as evidence for open hypersaline lakes. Moving up-section, carbonate deposits – interpreted previously as evidence of aridity – are actually diagenetic calcite cements, which preserve root systems of trees, suggesting a more closed environment; further up-section, the uppermost palaeosol layer contains abundant root traces and tree-stump casts, previously reported as evidence of a closed-canopy forest. These newly interpreted environmental differences are reflected by differences in faunal composition and abundance data from Hiwegi Formation fossil sites R1 and R3. Taken together, this work suggests that divergent palaeoenvironmental reconstructions in previous studies may have been informed by time-averaging across multiple environments. Further, results demonstrate that during the early Miocene local or regional habitat heterogeneity already existed. Rusinga’s Hiwegi Formation varied both spatially and temporally, which challenges the interpretation that a broad forested environment stretched across the African continent during the early Neogene, transitioning later to predominately open landscapes that characterize the region today. This result has important implications for interpretations of the selective pressures faced by early Miocene fauna, including Rusinga Island’s well-preserved fossil primates.     

Depth to the apparent redox potential discontinuity (aRPD) as a parameter of interest in marine benthic habitat quality models

The usefulness of the apparent redox potential discontinuity (aRPD) in assessments of marine benthic habitat quality was explored at two intertidal mudflats along the north Pacific coast of Canada. Two transects were established at each intertidal site, with three sediment biogeochemistry cores collected from each transect four times over the summer of 2016. Measurements of the sediment pore water dissolved oxygen (DO) content and redox (Eh) conditions were taken at the surface of the core (measured vertically), as well as at increasing depths (1 cm between readings) into the sediment (measured horizontally through predrilled holes in the biogeochemistry corer). While oxic, anoxic, oxidized, and reduced sediment pore water was observed above and below the aRPD, in general, sediment above the aRPD had higher DO content, and higher Eh values than sediment below the aRPD. Therefore, the aRPD depth can be used as a relative indicator of sediment pore water DO and Eh conditions: sediment with a deeper aRPD depth has more available DO, and the pore water has higher Eh values (more oxidized or less reduced) than sediment with a shallower aRPD depth. As such, the aRPD depth is a useful parameter to include in models that assess the quality of marine benthic habitats.     

An analysis of sponge diversity and distribution at three taxonomic levels in the Thousand Islands/Jakarta Bay reef complex, West-Java, Indonesia

Very few coral reefs are located close enough to large cities to study the influence of large urban populations on reef assemblages. An exception is the Thousand Islands reef complex to the north of Jakarta, the capital city of Indonesia, and one of the largest conurbations in the world. Here we present data from a detailed survey where sponge assemblages were assessed at 30 patch reefs associated with islands in three coastal zones along an in-to-offshore gradient. Sponge assemblages are described at three taxonomic levels of detail (species, genus and family level). We recorded a total of 118 sponge species, 64 genera and 36 families, Aaptos suberitoides (Brønsted, 1934), Clathria (Thalysias) reinwardti (Vosmaer, 1880), Petrosia (Petrosia) nigricans (Lindgren, 1897) and Xestospongia testudinaria (Lamarck, 1813) were the most common species overall. There was a pronounced difference in composition among zones with the most distinct difference between the inshore zone and the other two zones. The inshore environment was characterised by very high turbidity and low live coral cover; the dominant substrate consisted of algal turf and sand. Environmental conditions improved and sponge diversity increased further offshore, although most areas appeared to have been affected by some form of disturbance. Ordinations were also largely congruent, at species, generic and family levels of taxonomic resolution. This indicates that variation in composition at higher taxonomic levels is a good indicator of variation at lower taxonomic levels, at least when there is a pronounced environmental gradient.     

Geosynthesis of dibenzothiophene and alkyl dibenzothiophenes in crude oils and sediments by carbon catalysis

Sediment extracts and crude oils have been shown to contain methyl substituted biphenyls and dibenzothiophenes, with isomer distributions suggesting a geochemical relationship between the two compound classes. Laboratory simulation experiments have shown that carbon catalyses the reaction between surface adsorbed sulfur and biphenyl to form dibenzothiophene. Similarly, the methyl substituted biphenyls reacted to yield corresponding methyl dibenzothiophenes. We suggest that the widespread distribution of dibenzothiophene and alkylated dibenzothiophenes in sediments and crude oils is the result of a catalytic reaction of biphenyl ring systems and surface-adsorbed sulfur on the surface of carbonaceous material.     

Formation and reactions of alkyl adamantanes in sediments: Carbon surface reactions

Diamondoids are hydrocarbons with a carbon skeleton that is superimposable on the diamond lattice. Adamantane is the cage-shaped primary unit of diamondoids and occurs widely in sediments and petroleum. The first report of adamantane isolated from petroleum extends back seven decades, but the precursors and reaction mechanisms for the formation of adamantane and related diamondoids in sediments has remained unclear. We report the formation of alkyl adamantanes by heating β-ionone with activated carbon in closed system pyrolysis experiments in the range 170-320 °C. In addition, hydrogen exchange, demethylation, methyl transfer and isomerisation reactions were observed when the model compounds adamantane and 1,3-dimethyladamantane were heated at moderate temperature with activated carbon. A reaction pathway for the formation and reactions of alkyl adamantanes is proposed on the basis of ring isomerisation of adamantane to protoadamantane on the activated carbon surface. The carbonaceous surface reactions described help account for the occurrence and distribution of alkyl adamantanes in petroleum basins, as evidenced by the strong linear relationships between compound pairs related by isomerisation and demethylation for a set of crude oils from the Carnarvon Basin, Western Australia.