Selected cultures of mercury-resistant bacteria degrade the fungicide-slimicide phenylmercuric acetate. By means of a closed system incorporating a flameless atomic absorption spectrophotometer and a vapor phase chromatograph, it was demonstrated that elemental mercury vapor and benzene were products of phenylmercuric acetate degradation. 相似文献
Evidence from DNA phylogeny, Plio‐Pleistocene ocean currents, giant tortoise dispersal, evolution of plant defences, radiocarbon dates and archaeology indicates that the endemic giant tortoises on the Mascarenes and Seychelles colonized naturally and were not translocated there by humans. 相似文献
Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr−1) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.
Gray seals (Halichoerus grypus) undergo a terrestrial postweaning fast (PWF) that depletes energy reserves acquired during the suckling interval. Plasticity in PWF duration may ensure that pups of variable body condition depart for sea with adequate energy reserves. To test this hypothesis, we examined body condition of 30 gray seal pups at weaning and monitored their PWF duration. On average, fat accounted for 47.3% +/- 0.7% of their 53.2 +/- 1.3-kg weaning mass. Although fasting duration averaged 21 +/- 1.1 d (n = p28), there was considerable variation in fasting duration (9 to > 31 d) and the resulting age when pups departed to sea (26 to > 49 d). Percent fat at weaning(38.6%-54.6%) was positively correlated with fasting duration(n = 28, r = 0.376, P = 0.0489). In contrast, total body gross energy (735.3-1,447.4 MJ) and body mass (39.0-66.0 kg) were not correlated with fasting duration. Thus, body composition,not overall body reserves, predicted fasting duration, but the effect was weak, indicating that other factors also account for the observed variation in fasting duration. We speculate that pups with greater percent fat more effectively utilized lipid and conserved protein while meeting metabolic costs throughout the PWF. As a result, fatter pups extended the PWF duration,which may be critical for development of diving physiology and may have facilitated their survivorship to age 1. 相似文献
Fatty acid (FA) signature analysis is a powerful tool to investigate foraging ecology and food web dynamics in marine ecosystems.
However, use of FA signatures to qualitatively or quantitatively infer diets is potentially complicated by effects of nutritional
state on lipid metabolism. Estimation of diets using the quantitative fatty acid signature analysis (QFASA) model requires
the use of calibration coefficients to account for predator metabolism of individual FAs. We conducted a captive feeding experiment
to determine the effects of a 50% reduction in food intake on growth rate and adipose tissue FA signatures of tufted puffin
(Fratercula cirrhata) nestlings, a species that routinely experiences food restriction during growth. FA signatures of chicks fed low- and high-calorie
diets both exhibited a change in composition in response to the dietary shift with the direction of change in the composition
of individual FAs matching the direction of change in the dietary FAs. Despite a growth rate in the restricted nestlings that
was 38% of those in the well-fed group, rates of FA turnover were not different between high and low-calorie treatments, and
turnover was close to, but not entirely complete, after 27 days on both high-calorie and restricted diets. FA signatures of
tufted puffin nestlings were significantly affected by caloric restriction, but these effects were much less pronounced than
those of dietary turnover, and calibration coefficients of puffins fed low and high-calorie diets were highly correlated.
Our results demonstrate that changes in physiological state can affect FA metabolism, but future research is required to better
understand whether the size of these effects is sufficient to substantially alter diet estimation using the QFASA model. 相似文献