Carbon sequestration via wood burial

To mitigate global climate change, a portfolio of strategies will be needed to keep the atmospheric CO2 concentration below a dangerous level. Here a carbon sequestration strategy is proposed in which certain dead or live trees are harvested via collection or selective cutting, then buried in trenches or stowed away in above-ground shelters. The largely anaerobic condition under a sufficiently thick layer of soil will prevent the decomposition of the buried wood. Because a large flux of CO2 is constantly being assimilated into the world's forests via photosynthesis, cutting off its return pathway to the atmosphere forms an effective carbon sink

Population Structure of Humpback Whales from Their Breeding Grounds in the South Atlantic and Indian Oceans

Although humpback whales are among the best-studied of the large whales, population boundaries in the Southern Hemisphere (SH) have remained largely untested. We assess population structure of SH humpback whales using 1,527 samples collected from whales at fourteen sampling sites within the Southwestern and Southeastern Atlantic, the Southwestern Indian Ocean, and Northern Indian Ocean (Breeding Stocks A, B, C and X, respectively). Evaluation of mtDNA population structure and migration rates was carried out under different statistical frameworks. Using all genetic evidence, the results suggest significant degrees of population structure between all ocean basins, with the Southwestern and Northern Indian Ocean most differentiated from each other. Effective migration rates were highest between the Southeastern Atlantic and the Southwestern Indian Ocean, followed by rates within the Southeastern Atlantic, and the lowest between the Southwestern and Northern Indian Ocean. At finer scales, very low gene flow was detected between the two neighbouring sub-regions in the Southeastern Atlantic, compared to high gene flow for whales within the Southwestern Indian Ocean. Our genetic results support the current management designations proposed by the International Whaling Commission of Breeding Stocks A, B, C, and X as four strongly structured populations. The population structure patterns found in this study are likely to have been influenced by a combination of long-term maternally directed fidelity of migratory destinations, along with other ecological and oceanographic features in the region

Germline selection shapes human mitochondrial DNA diversity.

Approximately 2.4% of the human mitochondrial DNA (mtDNA) genome exhibits common homoplasmic genetic variation. We analyzed 12,975 whole-genome sequences to show that 45.1% of individuals from 1526 mother-offspring pairs harbor a mixed population of mtDNA (heteroplasmy), but the propensity for maternal transmission differs across the mitochondrial genome. Over one generation, we observed selection both for and against variants in specific genomic regions; known variants were more likely to be transmitted than previously unknown variants. However, new heteroplasmies were more likely to match the nuclear genetic ancestry as opposed to the ancestry of the mitochondrial genome on which the mutations occurred, validating our findings in 40,325 individuals. Thus, human mtDNA at the population level is shaped by selective forces within the female germ line under nuclear genetic control, which ensures consistency between the two independent genetic lineages.NIHR, Wellcome Trust, MRC, Genomics Englan

Direct and Indirect Effects of Ciguatoxin On Guinea-Pig Atria and Papillary-Muscles

The mode of action of ciguatoxin (CTX) on the isolated atrial and papillary muscle of the guinea-pig heart was investigated using conventional methods for the measurement of mechanical and electrophysiological parameters. CTX induced positive inotropic and positive klinotropic responses in atrial and papillary muscles. Each response consisted of two phases. The initial positive inotropic response developed rapidly and resulted from the previously reported indirect action of CTX. The second phase of positive inotropy developed more slowly and was well maintained at doses of CTX up to 0.15 mouse units/ml in atria and up to 0.8 M.U./ml in papillary muscles. This phase was found to result from a direct action of CTX on the myocardium which was not reversed by washing. Tetrodotoxin (TTX) reversed the positive inotropic effects stemming from the direct action of CTX. The (-) and (+) enantiomers of propranolol were equally effective in inhibiting the direct effect of CTX. These antagonists did not displace CTX from the myocardium. CTX induced a TTX-sensitive depolarization of stimulated or quiescent atrial cells. All the effects of CTX on the atrial action potential were reversed by TTX. It was therefore concluded that CTX opens voltage dependent Na channels. CTX bound equally to resting and K-depolarized Na channels but there were indications that electrical stimulation enhanced the rate of CTX binding. CTX overrides the positive staircase effect of increasing stimulation frequency. Na channels found in the atria which were particularly sensitive to TTX did not play a prominent role in mediating the CTX effect. CTX appeared to have little effect on the normal Na channel inactivation process. CTX did not restore contractions in the K-depolarized cardiac muscles examined. The sensitivity of CTX action to TTX distinguished it from cardiac glycoside activity. Established mechanisms of Na/Ca exchange and Ca-induced release of Ca can explain the link between CTX-induced increase of intracellular [Na] and the positive inotropic response

Humpback whale “super-groups” – A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (<i>Megaptera novaeangliae</i>) in the Benguela Upwelling System

<div><p>Southern Hemisphere humpback whales (<i>Megaptera novaeangliae</i>) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, <i>Discovery</i> and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (<i>Euphausia superba</i>) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (<i>E</i>. <i>lucens</i>), hyperiid amphipods (<i>Themisto gaudichaudii)</i>, mantis shrimp (<i>Pterygosquilla armata capensis</i>) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent “fishy” smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of <i>E</i>. <i>lucens</i> in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (<i>Thyrsites atun</i>) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events provide considerable potential for further investigation of Southern Hemisphere humpback feeding behaviours in these relatively accessible low-latitude waters.</p></div