Yields of cultured Pacific oysters Crassostrea gigas Thunberg improved after one generation of selection

Parental families (G₀) in three lines of Pacific oysters were selected based on live weight and meat yields at harvest. The average live weight yield of progeny (G₁) from crossing G₀-selected lines in seven trials was 9.5% greater than that of nonselected control families and live weight yields were significantly greater (ANOVA, P<0.001) in four out of seven trials. The response to selection was greater if G₁ families were tested at the same site as their parents' selection site rather than at a different site, although this effect was only significant for G₁ families of cohort 5 (P<0.01) but not cohort 7 (P>0.05). A significant genotype×environment interaction affected yields in both cohort 5 and cohort 7 (ANOVA; P<0.001). In addition, correlation between the yields of the same families planted at both intertidal and subtidal sites was positive but weak (cohort 5, r=0.30; cohort 7, r=0.35), indicating that selection for high yield in one environment would likely result in a low correlated response in a different environment. Nonetheless, it was possible to identify six families in cohort 5 and four families in cohort 7 that were among the top 10 families at both sites. Further evaluation of families across a wider range of environments is needed to determine if it is possible to substantially improve yields by selecting “generalist” families that perform well along the whole Pacific coast, or whether it will be necessary to select lines that are suited to particular sites.     

Big impacts from small abstractions: The effects of surface water abstraction on freshwater fish assemblages

1. Abstractions and diversions are prevalent in river networks worldwide; however, specific mechanisms and measures reflecting changes in functional characteristics of aquatic assemblages in response to flow abstraction have not been well established. In particular, the influence of small takes on fish assemblages is poorly understood.
2. Field surveys and stable‐isotope analyses were used to evaluate the impact of differing levels of flow abstraction on fish assemblage structure, and native–non‐native patterns of coexistence, associated with small surface water abstractions in four streams in New Zealand. Study design accounted for longitudinal processes (spatial autocorrelation) to isolate the effects of abstractions on fish assemblages.
3. Reaches with reduced flows downstream of abstraction points had significantly lower fish abundances per metre of stream length, probably because of decreased habitat size, altered interspecific interactions and barriers to movement. The loss of larger fish in reaches with high abstraction resulted in shallower mass–abundance slopes and shorter stable isotope‐derived food‐chain lengths, likely to have been caused by fewer trophic links in the food web. The large fish absent from these reaches were flow‐sensitive introduced salmonids, resulting in higher relative abundances of small‐bodied native fish, probably as a result of predatory and competitive release.
4. Quantification of metrics designed to characterize ecosystem functioning as well as abundance and species composition indicated that small water abstractions can alter both the structure and composition of stream fish assemblages and modify the outcomes of native–non‐native species interactions. Thus, a better understanding of the effects of small abstractions could be used to improve the strategic management of fish in invaded riverscapes.

     

Combined effect of fertilizer and herbicide applications on the abundance, community structure and performance of the soil methanotrophic community

The use of agrochemicals, such as mineral fertilizers and herbicides in agricultural systems, may affect the potential of soils to act as a sink for methane. Typically, the effect of each agrochemical on soil methane oxidation is investigated separately whereas in the field these agrochemicals are used together to form one comprehensive land management system. Here we report the results of field experiments that assessed the combined effect of multiple fertilizer and herbicide (nicosulfuron, dimethenamide and atrazine) applications on the soil methanotrophic community. Soils treated with organic fertilizer had three times higher methane oxidation rates compared to soils receiving mineral fertilizers. These higher oxidation rates were positively reflected in a significantly enhanced abundance of methanotrophs for the organic fertilized soils. In contrast, herbicide application did not alter significantly the soil methane oxidation rate or the methane-oxidizing population abundance. Subsequently, the methanotrophic community structure was analyzed with group-specific DGGE of 16S rRNA genes. Cluster analysis of the methanotrophic patterns clearly separated the mineral from organically fertilized soils. Less pronounced clustering differentiated between chemical and manual weed control. Furthermore, cluster analysis of the methanotrophic community revealed that soil type was the primary determinant of the community structure. Our results indicate that fertilizer type had the greatest influence on methane oxidizer activity and abundance. Soil type had the most pronounced effect on the microbial community structure.     

Predator control for protecting kaki (Himantopus novaezelandiae)—lessons from 20 years of management

In New Zealand, the endemic kaki or black stilt (Himantopus novaezelandiae) has been the focus of intensive conservation management for the past 20 years. Threatened by predation and habitat loss, the population fell to as low as 23 birds before management was implemented to reverse the decline. Predator trapping has been one form of management intervention in the wild, yet despite 20 years of control, there is only limited evidence to suggest that predator trapping is beneficial for the survival of kaki. Lack of adequate experimental design and understanding of the predator-prey dynamics in the system in which kaki live appear to be the main reasons why the benefits of predator control are not consistently clear. An adaptive management approach would have provided more information on the efficacy of predator trapping and increased understanding of the inter-relationships between kaki survival and predator abundance.     

Sea-level solar radiation in the biologically active spectrum

Calculations show a significant depletion of ultraviolet and visible radiation due to absorption and scattering by particulates and cloud drops for a fixed amount of ozone.     

Significant increases in pulping efficiency in C4H-F5H-transformed poplars: improved chemical savings and reduced environmental toxins

The gene encoding ferulate 5-hydroxylase (F5H) was overexpressed in poplar (Populus tremula x Populus alba) using the cinnamate-4-hydroxylase (C4H) promoter to drive expression specifically in cells involved in the lignin biosynthetic pathway and was shown to significantly alter the mole percentage of syringyl subunits in the lignin, as determined by thioacidolysis. Analysis of poplar transformed with a C4H-F5H construct demonstrated significant increases in chemical (kraft) pulping efficiency from greenhouse-grown trees. Compared to wild-type wood, decreases of 23 kappa units and increases of >20 ISO brightness units were observed in trees exhibiting high syringyl monomer concentrations. These changes were associated with no significant modification in total lignin content and no observed phenotypic differences. C4H-F5H-transformed trees could increase pulp throughputs at mills by >60% while concurrently decreasing chemicals employed during processing (chemical pulping and bleaching) and, consequently, the amount of deleterious byproducts released into the environment.     

Preferred nesting sites of bumblebee queens (Hymenoptera: Apidae) in agroecosystems in the UK

Bumblebees (Bombus spp.) have undergone a documented Europe-wide decline in recent years, mostly attributable to destruction of forage and nest sites caused by agricultural intensification. This study was set up to quantify species-specific nest-site preferences of observed UK species for various types of field and forest boundary habitat. In total, 1287 observations were made of seven common bumblebee species; nest-searching behaviour was taken as being indicative of nest site preference. There was interspecific variation in preferred habitat, with some species found to be much more specific in their choice of nest site than others. A strong association was found between those species that are known to prefer subterraneous nesting and those habitats that contained banks (Bombus terrestris, B. lapidarius and B. lucorum); other species were strongly associated with tussock-type vegetation (B. pascuorum, B. hortorum and B. ruderarius). In order to safeguard the continued existence of bumblebee species it is clear that a variety of field and forest boundary types need to be conserved; this has positive implications for the conservation of other species of flora and fauna associated with agroecosystems.     

Sediment toxicity and heavy metals in eleven lime reference lakes of Sweden

Sediments from an eutrophic reference lake (L. HjÄlmaren) and eleven oligotrophic Swedish lakes were analyzed for heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and tested for whole sediment toxicity to Daphnia magna. Whole sediment toxicity, expressed as 48-hr EC50 on a wet weight basis in reconstituted dilution water, ranged from 2.8% (most toxic) to >32% (least toxic). Correlations between bulk sediment heavy metal concentrations and toxicity were significant (P≤0.05) for Hg, Pb, and Zn. However, a causal connection between the concentrations of these metals and toxicity was not supported by the results from metal-spiked sediment toxicity tests. In addition sediment toxicity was not affected by the addition of EDTA, which is a strong chelator known to reduce metal toxicity. After storage for several months test sediments either remained nontoxic, toxic, or increased in toxicity. These results illustrate some of the difficulties in the interpretation of bulk sediment chemistry data and the release of toxic chemicals from sediment samples, highlighting the effect of sediment storage on toxicity.