Dehydrogenases as tools in the study of marine sediments

A method is outlined for the measurement of NADH₂-dependent dehydrogenase activity in whole samples as well as in fractions of carbonate sediments. The method is based on extraction of enzyme activity with phosphate buffer containing 0.12% Triton X-100, dialysis, and a photometric assay which permits initial velocity determinations of the enzyme reaction under controlled conditions of pH, temperature, and substrate concentration. The dehydrogenases extracted from carbonate sediment of a subtropical beach at Bermuda are characterized by low K _m values (0.03 to 0.07 mM NADH₂/1), pH maxima around 8.5, and temperature maxima between 35° and 40°C. Their vertical distribution in the sediment agrees with what is known about the distribution of biomass on beaches of this type, maximum activity occurring in the topmost centimetre. Approximately 80 to 90% of the total electron transport activity is contained in the grain fraction, the remainder in the interstitial fraction of a sediment sample. From this it can be inferred that the interstitial fauna contributes only little to the total energy budget of this type of sediment, which is dominated by the Aufwuchs on the sand grains. The electron transport activity (ETA) measured by means of the dehydrogenase assay is taken to represent the maximum transport capacity (ETC) of all the organisms living in the sand ecosystem. From published evidence it is inferred that oxygen consumption of sediment samples and of individual organisms measured in vivo usually accounts for 10 to 20% of the maximum electron transport capacity measured in vitro with saturating concentrations of substrates and with Triton X-100 as part of the enzyme assay. It is suggested further that the ratios of dehydrogenase activities in different fractions or zones of sediment, or of different organisms, may represent one of the best indicators, so far available, of energy relationships in marine sediments.Contribution No. 652 from the Bermuda Biological Station for Research.     

Biodiversity and food security: from trade-offs to synergies

Regional Environmental Change -     

Prenatal diagnosis and perinatal management of a fetal ovarian cyst

A case of a prenatally diagnosed fetal ovarian cyst is presented. The pregnancy was complicated only by polyhydramnios, and some degree of fetal bowel obstruction could be recognized on sonogram. The newborn was delivered vaginally in the 39th week of pregnancy, and the cyst was removed by laparotomy on the day of the delivery. The etiology of this rare fetal condition is unknown.     

Evaluation of the respicon as a personal inhalable sampler in industrial environments

The Respicon has been introduced as a sampler for health related measurements of airborne contaminants at workplaces. The instrument is aimed at simultaneous collection of three health related aerosol fractions: (a) the coarser inhalable fraction, defining the aerosol fraction that may enter the nose and mouth during breathing; (b) the intermediate thoracic fraction, defining the fraction that may penetrate beyond the larynx and so reach the lung; and (c) the finer respirable fraction, defining the fraction that may penetrate to gas exchange region of the lung. The instrument has a number of features attractive to occupational hygienists: in addition to providing the three aerosol fractions simultaneously, it is light and compact enough to be used as a personal sampler. yet can be a tripod mounted for area sampling, it can provide samples not only for gravimetric analysis but also microscopic and chemical analyses; and it is also available in a photometric direct-reading version. The instrument has previously been evaluated as an area sampler and, in this mode of operation, has shown reasonable accuracy in collecting respirable, thoracic and inhalable particles, the latter up to particle diameters of ca. 80 microm. Except for some scattered unpublished data there exist no systematic investigations in the Respicon's performance when used as a personal sampler in the industrial environment. In this paper, we will report on a study of side by side comparison of the Respicon with the IOM inhalable sampler, regarded as a reference instrument for the inhalable fraction. The main study was performed at six different workplaces in a nickel refinery. Statistical analysis of the gravimetrically-determined concentration data reveals consistently lower aerosol exposure values for the Respicon as compared to the IOM sampler. The data for the nickel workplaces are compared with findings from other studies. The results are interpreted in the light of the overall results and the possibility of introducing a correction factor is discussed.     

Scalar transport from point sources in the flow around a finite-height cylinder

This paper presents a large eddy simulation of mass transfer in the flow around a surface-mounted finite-height circular cylinder. The study was carried out for a cylinder with height-to-diameter ratio of 2.5 and a Reynolds number based on the cylinder diameter of 44000. The approach flow boundary layer had a thickness of about 10% of the cylinder height. A tracer was released at various levels upstream of the cylinder. The effect of the release position in the subsequent spreading and dilution of the plumes is analyzed. It is found that a tracer released at the top or at mid-height is entrained into the recirculation zone behind the cylinder, and therefore presents similar plume evolution in the far wake in both cases. If the tracer is released at around three-quarters of the height of the cylinder, it is not significantly entrained by the main recirculation region, leading to smaller rates of spreading of the plume. Finally, if the tracer is released near the floor, the plume is entrained by the horseshoe vortex that wraps around the cylinder, leading to a large lateral spreading of the plume, remaining always near the floor.     

Polycyclic aromatic hydrocarbons and trace metal contamination of coastal sediment and biota from Togo

The state of contamination of tropical environments, particularly in Africa, remains a relatively under explored subject. Here, we determined polycyclic aromatic hydrocarbon (PAH) and trace metal concentrations in coastal sediment and biota samples (fish and mussels) from Togo (West Africa). In the sediments, the ∑21 PAH concentrations ranged from <4 ng g(-1) to 257 ng g(-1), averaging 92 ng g(-1). Concentration ratios of low molecular weight PAHs (2-3 rings) versus high molecular weight PAHs (≥4 rings) were always lower than 1 (ranging from 0.08 to 0.46) indicating that high molecular weight PAHs were dominant in all sediment samples, and that PAHs originated mainly from anthropogenic combustion activities. The sediments were also analyzed for major elements and a total of 15 trace metals, which were found in elevated concentrations. The calculated enrichment factor (EF) values relative to the Earth's crust show that the contamination is extremely severe for Cd (EF = 191), severe for Cr (EF = 18) and U (EF = 17.8), moderately severe for Zr (EF = 8.8), for Ni (EF = 6.8), Sr (EF = 5.9) and Ba (EF = 5.4), and moderate for V (EF = 3.6) and Zn (EF = 3.4). Sediments sampled in areas affected by the dumping of phosphorite mine tailings showed particularly high concentrations of trace metals. Overall, concentrations of both PAHs and trace metals in sediment tend to increase from the coastline to the open sea (2 km offshore). This is attributable to the increasingly finer texture of coastal sediment found offshore, which has a terrigenous origin and appears loaded with various contaminants through adsorption processes. Such high loads of trace metals were also found in the biota (fish and mussels). The ratio of measured trace metal concentrations in biota to threshold limits set by the World Health Organization herein defined as relative health factor (RHF) was high. Average RHF values in fish were highest for Se (470), As (250), Ag (97), Ni (78), Mn (63), Fe (53), Pb (36), Cd (10), and Cr (7) while lowest for Cu (0.08) and Zn (0.03). Cd and Al did not bioaccumulate in the analyzed fish species. In mussels, the RHF values were highest for Fe (9,108), As (295), Pb (276), Se (273), Mn (186), Ni (71), Ag (70), Cd (14), and Cu (4).     

Avian magnetic compass: fast adjustment to intensities outside the normal functional window

To determine how fast birds can adapt to magnetic intensities outside the normal functional window of their magnetic compass, we tested migratory birds in a magnetic field of 92,000 nT, twice the intensity of the local geomagnetic field at the test site in Frankfurt a.M., Germany. In the local field, robins showed a significant preference of their southerly migratory direction, whereas in the 92,000-nT field, they were initially disoriented. However, when the birds were preexposed to 92,000 nT for 1 h before being tested, they were able to orient under this intensity, and their behavior did not differ from that in the geomagnetic field. These data show that birds require only a short time to adjust to magnetic intensities, which they cannot spontaneously use for orientation. Interpreting these findings in view of the radical pair model (Ritz et al. 2000), this means that they can learn rather quickly to interpret novel activation patterns on their retina.     

Environmental Modeling and Methods for Estimation of the Global Health Impacts of Air Pollution

Air pollution is increasingly recognized as a significant contributor to global health outcomes. A methodological framework for evaluating the global health-related outcomes of outdoor and indoor (household) air pollution is presented and validated for the year 2005. Ambient concentrations of PM2.5 are estimated with a combination of energy and atmospheric models, with detailed representation of urban and rural spatial exposures. Populations dependent on solid fuels are established with household survey data. Health impacts for outdoor and household air pollution are independently calculated using the fractions of disease that can be attributed to ambient air pollution exposure and solid fuel use. Estimated ambient pollution concentrations indicate that more than 80% of the population exceeds the WHO Air Quality Guidelines in 2005. In addition, 3.26?billion people were found to use solid fuel for cooking in three regions of Sub Saharan Africa, South Asia and Pacific Asia in 2005. Outdoor air pollution results in 2.7?million deaths or 23?million disability adjusted life years (DALYs) while household air pollution from solid fuel use and related indoor smoke results in 2.1?million deaths or 41.6?million DALYs. The higher morbidity from household air pollution can be attributed to children below the age of 5 in Sub Saharan Africa and South Asia. The burden of disease from air pollution is found to be significant, thus indicating the importance of policy interventions.