Testing the potential for improving quality of sediments impacted by mussel farms using bioturbating polychaete worms

Biodeposits from farmed mussels severely influence the biogeochemistry of sediments by increasing the levels of organic matter (OM). Mitigation of such negative impacts is important for the development of sustainable aquaculture operations. As a step towards developing methods for remediation of coastal sediments affected by mussel farming, the effects of the polychaete, Hediste diversicolor was evaluated experimentally. In a series of field‐ and laboratory experiments we tested hypotheses about the effects of polychaetes on sediment oxygen consumption, nutrient fluxes and sulphide pools under different polychaete densities and sedimentation regimes. The experimental results support the idea that polychaetes can mitigate negative effects on the benthic environment beneath mussel farms. H. diversicolor oxidized the sediment and generally enhanced the oxygen consumption, and thus the decomposition of OM. The accumulation of pore water sulphides were reduced and fluxes of nutrients across the sediment‐water interface increased. Additional calculations suggest that the effects of polychaetes were mainly indirect and driven by increased microbial activity due to the borrowing activity of the polychaetes. Trends of increasing decomposition with increasing polychaete density suggest that the decomposition could be further enhanced by higher densities. Overall, we concluded that H. diversicolor is a potentially strong candidate for remediation of mussel farm sediments. The results show that sediments inhabited by H. diversicolor have high assimilative capacity of OM and oxygen conditions are significantly improved following the addition of polychaetes at naturally occurring densities. However, technological developments are needed in order to allow the approach to be used in practice.     

Herbicide sorption, degradation, and leaching in three Swedish soils under long-term conventional and reduced tillage

Soil tillage has the potential to influence water flow and solute transport through the soil by cutting continuous macropores which connect the soil surface to the subsoil. Tillage also affects soil organic carbon sequestration which may lead to different sorption and degradation properties depending on the long-term tillage practices. The objective of this study was to quantify the differences in sorption, degradation and leaching of the herbicides bentazone and isoproturon between conventional tillage (CT) and reduced tillage (RT) under Swedish conditions. Three sites, Ultuna (silty clay), Säby (loam), and Lönnstorp (sandy loam moraine till), where replicate plots had been under either CT or RT for at least 9 years, were included in the study. A higher organic carbon content had developed in the top 5 cm of RT plots compared to the 10–20 cm depth and CT plots since the establishment of the experimental treatments. Adsorption and degradation were studied in laboratory experiments and solute transport was studied in undisturbed column experiments using non-reactive tracers and herbicides. The results from the column experiments were not significantly different between tillage treatments for Säby and Lönnstorp. For Ultuna, RT resulted in a more pronounced preferential tracer transport pattern and isoproturon leaching was twelve times larger compared to CT columns. This indicates that the tillage treatment had affected the macropore connectivity only at Ultuna. Freundlich adsorption coefficients for both bentazone and isoproturon were larger (though not always significantly) in the top 5 cm of RT soil compared to the 10–20 cm depth and to CT, reflecting the higher organic carbon content. The degradation rate was also generally larger (though not always significantly) in the top 5 cm of RT soil. These results show that RT has the potential to reduce pesticide leaching. However, any such reduction may be counter-balanced by enhanced preferential flow for soils where RT results in improved macropore connectivity.     

Plasticization of a protein-based film by glycerol: a spectroscopic, mechanical, and thermal study

Kafirin, the seed storage protein of the cereal sorghum, is highly homologous with the maize storage protein zein. The effects of plasticisation of a kafirin film by glycerol in the absence of water were examined by a combination of spectroscopic (NMR and infrared), rheological, and calorimetric methods. The results suggest that at low glycerol levels the glycerol is absorbed onto and possibly into the protein. Increasing the level of glycerol increases the motion of the protein and changes the protein conformation. There are corresponding changes of the mechanical properties of protein films. At 40% (w/w) of glycerol, two glass transition temperatures were observed, one of which corresponded to the glass transition temperature of pure glycerol. This result indicates that at this level of plasticizer there are sufficient glycerol/glycerol interactions occurring to allow a separate glass formation process for glycerol.     

Emergence of novel strains of avian infectious bronchitis virus in Sweden

Infectious bronchitis virus (IBV) causes avian infectious bronchitis, an important disease that produces severe economic losses in the poultry industry worldwide. Recent IBV infections in Sweden have been associated with poor growth in broilers, drop in egg production and thin egg shells in layers. The complete spike gene of selected isolates from IBV cases was amplified and sequenced using conventional RT-PCR. Nucleotide and amino acid sequence comparisons have shown that the recent isolates bear 98.97% genetic similarity with strains of the QX-like genotype. The phylogenetic analysis revealed that strains predominant in the nineties, which were of the Massachusetts type, have been replaced by D388/QX-like strains, however the evolutionary link could not be established. The homology between the two genotypes was 79 and 81%. Remarkably, a strong positive selection pressure was determined, mostly involving the S1 subunit of the S gene. This strong selective pressure resulted in recombination events, insertions and deletions in the S gene. Two new isolates generated from recombination were found with nucleotide sequence diverging 1.7-2.4% from the D388/QX-like branch, indicating the emergence of a new lineage. The study demonstrates a constant evolution of IBV that might be in relation to increased poultry farming, trade and vaccine pressure. The findings underscore the importance of continuous monitoring to control spread of infections, as well as to timely adjust diagnostic methods, molecular epidemiological studies, development and use of vaccines that are adapted to the changing disease scenario.     

An Estimation of the Potential Fluxes of Nitrogen Phosphorus, Cadmium and Lead from Sea Ice and Snow in the Northern Baltic Sea

The amount of nutrients (N and P) and trace elements (Cd and Pb)accumulated and incorporated into the snow and sea ice cover was assessed for the northern Baltic Sea, resulting in an estimate for the potential flux of nutrients and trace elements to underlying waters during sea ice and snow melt. From the atmosphere the sea ice and snow cover accumulate less than 3% of the annual N and P load, and about 5% of the annual Cd and Pb load to the Bothnian Bay. The atmospheric deposition of nutrients to the northern Baltic Sea has declined considerably during the last decade. The total accumulation in the snow and ice, from the atmosphere and seawater, make up to 6% of the annual nutrient and up to 40% of the annual Cd and Pb load into the Bothnian Bay. Thus sea ice plays an important, but still poorly understood role in chemical cycling, transformations, and budgets. The fate of substances accumulated and released from snow and sea ice merit further investigation, especially if sea ice is a source and a platform for transformation of accumulated substances, thus indirectly affecting their toxicity and/or bioavailability before they are released to the water column.     

Saproxylic beetles in natural and man-made deciduous high stumps retained for conservation

Intensive forest management in Scandinavia has decreased the amount of dead wood required by saproxylic (wood-living) organisms. To reduce this problem, some dead wood is now retained during forest operations, often in the form of man-made high stumps (ca. 4 m high). Most often these stumps are cut with a harvester, although the stumps in this study were made with explosives. The aims of this study were to determine whether such stumps of aspen (Populus tremula) and birch (Betula spp.) could be used by red-listed saproxylic beetles (Coleoptera), and to examine how the fauna of man-made high stumps differs from that of natural stumps. We also studied how tree species, sun-exposure, stage of decay and trunk diameter influenced the fauna. In 169 samples of bark from high stumps 116 saproxylic species were found, of which 21 were red-listed. Many species, including red-listed ones, were more associated with man-made stumps than with natural stumps. However, in total, more species were found in the natural than in the man-made stumps. This is probably because man-made stumps provide a more homogeneous type of wood substrate than natural ones. Among the other variables the difference between aspen and birch was the most important. We conclude that man-made high stumps are valuable habitats for many saproxylic beetle species.     

Method to compute fiber directions in wood from computed tomography images

This paper describes a new method, called the CT-direction method, in which the fiber directions in wood in three-dimensional space are calculated from the pixel information on a series of two-dimensional computed tomography images. Local fiber directions are calculated from the principal directions of inertia of measurement spheres distributed throughout the body of the wood object. The calculated fiber directions are probably due to density streaks in the material, such as fiber bundles, which are directed in the fiber direction, and not the density of individual fibers, which are too small to be detected. The fiber directions vary locally, and density streaks from knots, growth rings, and compression wood influence the results, which adds spread to the results. The fiber directions are presented as spiral grain angles and conical angles and are compared with spiral grain angles measured with the tracheid-effect method. The comparisons show that the CT-direction method is a nondestructive way to measure fiber directions locally and in the interior of the body of a piece of wood.