Estimation of conversion factors for fungal biomass determination in compost using ergosterol and PLFA 18:2ω6,9

Eleven species of common fungi from compost were analysed for their content of ergosterol and phospholipid fatty acids (PLFAs) after growth on agar media. Mean content of ergosterol was 3.1 mg g⁻¹ dw of fungal mycelium (range 1-24 mg g⁻¹ dw). Total amount of PLFAs varied between 2.6 and 43.5 μmol g⁻¹ dw of fungi (mean 14.9 μmol g⁻¹ dw). The most common PLFAs were 16:0, 18:2ω6,9 and 18:1ω9, comprising between 79 and 97 mol% of the total amount of PLFAs. The PLFA 18:2ω6,9, suggested as a marker molecule for fungi, comprised between 36 and 61 mol% of the total PLFAs in the Ascomycetes, between 45 and 57 mol% in the Basidiomycetes and 12-22 mol% in the Zygomycetes. There was a good correlation between the content of the two fungal marker molecules, ergosterol and the PLFA 18:2ω6,9, with a mean content of 1 mg ergosterol being equivalent to 2.1 μmol of 18:2ω6,9. Based on results from the fungal isolates, conversion factors were calculated (5.4 mg ergosterol g⁻¹ biomass C and 11.8 μmol 18:2ω6,9 g⁻¹ biomass C) and applied to compost samples in which both the ergosterol and the PLFA 18:2ω6,9 content had been measured. This resulted in similar estimates of fungal biomass C using the two marker molecules, but was three to five times higher than total microbial biomass C calculated using ATP content in the compost. This could partly be explained by the fact that both of the markers used for fungal biomass are cell membrane constituents. Thus, the ergosterol and the PLFA content were related to the hyphal diameter of the fungi, where fungi with thinner hyphae had higher ergosterol concentrations than fungi with thicker hyphae. This could also partly explain the large interspecific variation in content of the two marker molecules.     

Pre-Clovis mastodon hunting 13,800 years ago at the Manis site, Washington

The tip of a projectile point made of mastodon bone is embedded in a rib of a single disarticulated mastodon at the Manis site in the state of Washington. Radiocarbon dating and DNA analysis show that the rib is associated with the other remains and dates to 13,800 years ago. Thus, osseous projectile points, common to the Beringian Upper Paleolithic and Clovis, were made and used during pre-Clovis times in North America. The Manis site, combined with evidence of mammoth hunting at sites in Wisconsin, provides evidence that people were hunting proboscideans at least two millennia before Clovis.     

Release of emamectin from sediment: effects of oil,organic material or infauna?

Purpose

The aim of this study was to quantify the release of the hydrophobic contaminant emamectin (EMA) from marine sediments in response to inputs of organic material (OM) and/or oil, in the presence or absence of two different bioturbating species. Specifically, it was designed to test whether oil would decrease the release of EMA and whether OM and/or the presence of bioturbating macrofauna would increase the release of EMA from sediment.

Materials and methods

Experimental sediments were spiked with EMA (5 μg kg^?1 wet sediment). The different treatments were prepared by the addition of OM (310 g algae m^?2) and/or an aliphatic oil (29.6 g oil m^?2). In addition, two bioturbating species, Brissopsis lyrifera or Ennucula tenuis, were added in some aquaria, resulting in a total of 12 treatments with four replicates each. Water samples for analyses of silicate and EMA and sediment samples for analyses of total organic carbon (TOC) were taken at the start and end of the experimental exposure. In addition, oxygen was measured during the experimental period of 8 days. Fluxes were calculated and compared between treatments using generalised linear models (GLMs).

Results and discussion

The EMA release flux was significantly increased in treatments with added OM, possibly reflecting the presence of soluble complexes formed between EMA and dissolved OM. The presence of B. lyrifera caused a small, but statistically significant, increase in EMA release from sediment. This species would be expected to have a stronger effect on bioirrigation and particle mixing than E. tenuis, particularly when the population density of the latter species is low (as in the present experiment). There were no consistent effects of oil in this experiment, but the presence of oil decreased the EMA release flux when co-occurring with added OM and/or B. lyrifera. Increased retention of hydrophobic contaminants in the presence of oil is consistent with the existing literature on contaminant fate.

Conclusions

The results from this study highlight the need to consider both the infauna present in polluted areas and the level of organic enrichment of the sediment when modelling the environmental fate of hydrophobic contaminants. It also highlights that labile OM and refractory oil appear to differ in their effects on the remobilisation of hydrophobic organic contaminants, by reducing and increasing release, respectively.     

An Aboriginal Australian genome reveals separate human dispersals into Asia

We present an Aboriginal Australian genomic sequence obtained from a 100-year-old lock of hair donated by an Aboriginal man from southern Western Australia in the early 20th century. We detect no evidence of European admixture and estimate contamination levels to be below 0.5%. We show that Aboriginal Australians are descendants of an early human dispersal into eastern Asia, possibly 62,000 to 75,000 years ago. This dispersal is separate from the one that gave rise to modern Asians 25,000 to 38,000 years ago. We also find evidence of gene flow between populations of the two dispersal waves prior to the divergence of Native Americans from modern Asian ancestors. Our findings support the hypothesis that present-day Aboriginal Australians descend from the earliest humans to occupy Australia, likely representing one of the oldest continuous populations outside Africa.     

Screening of properties of modified chitosan-treated wood

Chitosan is a biopolymer derived from chitin in crustacean shells. Over the past decade it has been studied as an environmentally benign wood-protecting agent. It is assumed to act as a fungi-stat against a wide range of fungi and even as a fungicide at higher concentrations. This study investigated the properties of wood treated with modified chitosan of different molecular weights. Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.) samples were impregnated with two chitosan solutions differing in their average molecular weights. The chitosan solutions were depolymerized by nitrous acid to one solution of high molecular weight and one solution of low molecular weight with a concentration of 5% (w/v). The results show changes in sorption properties, antifungal properties, fire-retardant properties and mechanical properties of modified chitosan-treated wood. Heat-modified, chitosan-treated wood showed similar properties to chitosan-treated wood, except for brownish coloration, enhanced hydrophobation, and slightly reduced antifungal and fire-retardant properties. The modulus of rupture and hardness showed little or no change. The modulus of elasticity of the heat-modified, chitosan-treated wood increased by 27% compared with untreated wood.     

Release of dissolved trace metals and organic contaminants during deep water disposal of contaminated sediments from Oslo harbour,Norway

Purpose  

The current study was conducted in order to assess the release of dissolved contaminants from sediment relocation works in Oslo harbour, Norway, whilst operations were being carried out, and to assess the potential for spreading into the wider fjord area.     

Serum chemistry reference values in free‐ranging North Atlantic male walruses (Odobenus rosmarus rosmarus) from the Svalbard archipelago

Background: Information regarding health and disease is limited for walruses, a keystone species in arctic marine ecosystems. Serum chemistry analysis is a useful clinical tool for the health assessment of walruses, but only a few captive Pacific walruses have been evaluated. Objectives: The aim of this study was to determine serum chemistry reference values for free‐ranging male Atlantic walruses (Odobenus rosmarus rosmarus) on Svalbard and to assess potential differences in animals with low and high tissue levels of organic pollutants. Methods: Blood samples were collected from 17 wild, adult, male Atlantic walruses chemically immobilized with etorphine at eastern Svalbard (Norway). Serum was obtained for routine biochemical analysis as well as nonesterified free fatty acids (NEFA) and cortisol tests. Serum protein concentration was also measured by agarose gel electrophoresis. Results: Reference values (ranges) included alanine aminotransferase (12–51 U/L), aspartate aminotransferase (54–137 U/L), alkaline phosphatase (42–243 U/L), creatine kinase (32–506 U/L), lactate dehydrogenase (480–1322 U/L), amylase (0–23 U/L), lipase (68–298 U/L), total protein (68–91 g/L), albumin (25.3–34.8 g/L), creatinine (84–137 μmol/L), urea (8.2–19.9 mmol/L), bilirubin (0–4 μmol/L), cholesterol (4.4–7.3 mmol/L), NEFA (0.1–0.4 mmol/L), triglycerides (0.6–2.2 mmol/L), calcium (2.0–2.7 mmol/L), phosphorus (1.7–2.8 mmol/L), sodium (147–162 mmol/L), potassium (4.7–7.4 mmol/L), chloride (102–115 mmol/L), and cortisol (<28–214 nmol/L). Walruses exposed to high levels of organic pollutants (n=6) had significantly lower (P=.022) phosphorus concentration than those with low levels of pollutants (n=6). Conclusions: The clinical chemistry reference values determined in this study can serve as baseline data for future health‐related studies of walruses in a changing Arctic and may also be helpful for health evaluations of walruses in captivity. Impacts of the exposure of marine mammals to organic pollutants should be further investigated.