Organochlorine contaminants in seven species of Arctic seabirds from northern Baffin Bay

Organochlorine contaminants (OCs) were determined in liver and fat of seven species of seabirds (Alle alle, Uria lomvia, Cepphus grylle, Rissa tridactyla, Pagophila eburnea, Larus hyperboreus, and Fulmaris glacialis) collected in May/June 1998 from the Northwater Polynya in northern Baffin Bay. OC concentrations ranged over an order of magnitude between seabird species and OC groups, with PCBs having the highest concentrations followed by DDT, chlordane, HCH and ClBz. Positive relationships between delta15N (estimator of trophic level) and OC concentrations (lipid basis) were found for all OC groups, showing that trophic position and biomagnification significantly influence OC concentrations in Arctic seabirds. Concentrations of a number of OCs in particular species (e.g., HCH in P. eburnean) were lower than expected based on delta15N and was attributed to biotransformation. P. eburnea and F. glacialis, which scavenge, and R. tridactyla, which migrate from the south, were consistently above the delta15N-OC regression providing evidence that these variables can elevate OC concentrations. Stable isotope measurements in muscle may not be suitable for identifying past scavenging events by seabirds. OC relative proportions were related to trophic position and phylogeny, showing that OC biotransformation varies between seabird groups. Trophic level, migration, scavenging and biotransformation all play important roles in the OCs found in Arctic seabirds.     

Crude oil contaminated soil washing in air sparging assisted stirred tank reactor using biosurfactants

This study investigated the removal of crude oil from soil using air sparging assisted stirred tank reactors. Two surfactants (rhamnolipid and sodium dodecyl sulfate, SDS) were tested and the effects of different parameters (i.e. temperature, surfactant concentrations, washing time, volume/mass ratio) were investigated under varying washing modes namely, stirring only, air sparging only and the combination of stirring and air sparging. The results showed that SDS removed more than 80% crude oil from non-weathered soil samples, whilst rhamnolipid showed similar oil removal at the third and fourth levels of the parameters tested. The oil removal ability of the seawater prepared solutions were better than those of the distilled water solutions at the first and second levels of temperature and concentration of surfactant solutions. This approach of soil washing was noted to be effective in reducing the amount of oil in soil. Therefore we suggested that a field scale test be conducted to assess the efficiency of these surfactants.     

Distribution and diet of juvenile Patagonian toothfish on the South Georgia and Shag Rocks shelves (Southern Ocean)

The distribution and diet of juvenile (<750 mm) Patagonian toothfish are described from four annual trawl surveys (2003–2006) around the island of South Georgia in the Atlantic sector of the Southern Ocean. Recruitment of toothfish varies inter-annually, and a single large cohort dominated during the four years surveyed. Most juveniles were caught on the Shag Rocks shelf to the NW of South Georgia, with fish subsequently dispersing to deeper water around both the South Georgia and Shag Rocks shelves. Mean size of juvenile toothfish increased with depth of capture. Stomach contents analysis was conducted on 795 fish that contained food remains and revealed that juvenile toothfish are essentially piscivorous, with the diet dominated by notothenid fish. The yellow-finned notothen, Patagonotothen guntheri, was the dominant prey at Shag Rocks whilst at South Georgia, where P. guntheri is absent, the dominant prey were Antarctic krill and notothenid fish. The diet changed with size, with an increase in myctophid fish and krill as toothfish grow and disperse. The size of prey also increased with fish size, with a greater range of prey sizes consumed by larger fish.     

Persistent near-bottom aggregations of mesopelagic animals along the North Carolina and Virginia continental slopes

Submersible observations during four missions over the North Carolina and Virginia continental slopes (184–900 m) documented the occurrence of large aggregations of mesopelagic fishes and macronektonic invertebrates near or on the bottom. Aggregated mesopelagics formed a layer up to tens of meters deep positioned from a few centimeters to 20 m, usually <10 m, above the substrate. Aggregations were numerically dominated by microvores, notably the myctophid fish Ceratoscopelus maderensis and the penaeid shrimp Sergestes arcticus. Consistently present but in relatively lower numbers, were mesopelagic predators, including the paralepidids Notolepis rissoi and Lestidium atlanticum, the eel Nemichthys scolopaceus, the stomiid fishes Chauliodus sloani and Stomias boa ferox, and squids Illex spp. Near-bottom aggregations do not appear to be an artifact due to attraction to the submersible. Based on submersible observations in three areas in 4 years spanning a decade, near-bottom aggregations of midwater organisms appear to be a geographically widespread and persistent phenomenon along the continental slope of the southeastern US Aggregations may exploit areas of enhanced food resources at the bottom.     

Twin–twin transfusion syndrome: mathematical modelling

Twin–twin transfusion syndrome (TTTS) represents a pregnancy complication with a high risk for perinatal mortality and postnatal morbidity. Mathematical models have been utilized to examine the mechanisms of disease and potential treatment modalities. We developed four consecutive models based on pathophysiology mechanisms. Conceptually, these models remained simple, but with increased complexity in details. We present our models tutorially with the necessary equations expressed in words. The aetiology of TTTS was related to AV anastomoses from donor to recipient and their growth commensurate with placental growth. We assessed that natural growth of placenta and foetuses causes the diameter and length of the AV, as well as the AV's pressure gradient, to increase proportional to gestational age. The AV transfusion then increases faster than natural foetal growth. A progressively increasing discordance subsequently develops, not compensated for by foetal growth. A simulation is performed to show how this discordance in blood volumetric development causes successive discordances in other functions, particularly renal, circulatory, and cardio-vascular, resulting in disease progression to the various stages of TTTS. In conclusion, mathematical modelling of TTTS has provided an understanding of the sequence of events that leads to the various presentations of TTTS stages as well as the efficacy of therapies. Copyright © 2008 John Wiley & Sons, Ltd.     

Drivers of Forest Cover Dynamics in Smallholder Farming Systems: The Case of Northwestern Vietnam

The national-scale forest recovery of Vietnam started in the early 1990s and is associated with a shift from net deforestation to net reforestation. Large disparities in forest cover dynamics are, however, observed at the local scale. This study aims to unravel the mechanisms driving forest cover change for a mountainous region located in northwest Vietnam. Statistical analyses were used to explore the association between forest cover change and household characteristics. In Sa Pa district, deforestation rates are decreasing, but forest degradation continues at similar rates. Deforestation is not necessarily associated with impoverished ethnic communities or high levels of subsistence farming, and the largest forest cover dynamics are found in villages with the best socio-economic conditions. Our empirical study does not provide strong evidence of a dominant role of agriculture in forest cover dynamics. It shows that empirical studies on local-scale forest dynamics remain important to unravel the complexity of human–environment interactions.