Effects of pioneering plants on microbial structures and functions in a glacier forefield

This study investigates the small-scale spatial impact of the pioneering plant Leucanthemopsis alpina (L.) Heywood (L. alpina) on biological and chemical–physical parameters in an early successional stage of a glacier forefield. Considering the frequent occurrence of isolated patches of this pioneer plant in the forefield of the Dammaglacier (Switzerland), we hypothesized that the impact of the plant would establish gradients in nutrients, and microbial community structure and activity that may be of importance for the successional processes occurring in the forefield. Our results indicated that, in young successional soils, the rhizosphere effect of L. alpina plant patches can influence bacterial cell numbers and activities not only within the root zone, but even at 20 cm distance from the plant. Microbial cell counts, active cells, and saccharase, glucosidase, and acid phosphatase activities revealed significant distance effects, decreasing from soil directly underneath the plant to soils at 20 and 40 cm distance. Soil chemical and physical parameters did not exhibit significant trends. Fingerprinting analysis of amplified 16S rDNA fragments was used to characterize the microbial community. A selective effect of the plant on the microbial community could not be shown because the bacterial communities were similar regardless of distance to the plant.     

Context is more important than habitat type in determining use by juvenile fish

Context

Habitat characteristics are often equated with habitat function for animals. However, in heterogeneous landscapes, similar habitat types occur in different environmental contexts. In the marine realm, landscape studies have been confined to particular environments, rather than encompassing entire seascapes, due to incompatible sampling methods required in different situations.

Objectives

We examined the interactive structuring effects of local habitat characteristics and environmental context on assemblage composition.

Methods

We used a single technique—remote underwater video census—to explore the importance of habitat type (biotic structural components, substrate, and depth) and environmental context (marine vs estuarine) in structuring juvenile fish assemblages throughout an entire coastal region. In this model system, a range of structural habitat types were present in both estuarine and marine contexts.

Results

The 1315 video surveys collected show a clear hierarchy in the organisation of juvenile fish communities, with assemblages first distinguished by environmental context, then by habitat type. Marine and estuarine mangroves contained entirely different assemblages, and likewise for rocky reefs and submerged aquatic vegetation. Our results suggest that two functionally different ‘seascape nursery’ types exist at local scales within a single region, defined by their context.

Conclusions

The context of a location can be of greater significance in determining potential habitat function than what habitat-forming biota and substrates are present, and apparently similar habitat types in different contexts may be functionally distinct. These findings have important implications for local-scale management and conservation of juvenile fish habitats, particularly in regard to offsetting and restoration.

     

Small forest patches as pollinator habitat: oases in an agricultural desert?

Landscape Ecology - Small forest fragments are often the most abundant type of semi-natural habitat in intensive agricultural landscapes. Wild pollinators can use these forest patches as nesting or...     

The effect of mass-flowering orchards and semi-natural habitat on bumblebee colony performance

Landscape Ecology - Bumblebees are important pollinators for agricultural crops and wild plants. However, agricultural intensification and loss of semi-natural habitat may have adverse effects on...     

Phylogenetic analysis of intestinal bacteria of freshwater salmon Salmo salar and sea trout Salmo trutta trutta and diet

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.     

Growth and morphology of an endangered native freshwater fish,crucian carp Carassius carassius,in an English ornamental pond

• 1. Crucian carp Carassius carassius, which is native to south‐east England, has received little previous study in Britain but is threatened by introductions of goldfish Carassius auratus through hybridization and by frequent mis‐identification of brown goldfish as crucian carp. The present study provides the first data on back‐calculated growth, morphology and age‐at‐maturity of crucian carp in Britain.
• 2. The youngest mature crucian were female (age 2+), the smallest mature crucian were male (age 3+), with almost all fish mature at age 3+. Sex dimorphism in back‐calculated standard length at age was not observed except at age 2+ (juveniles longest). Shifts in morphological characters often associated with maturation (dorsal and ventral fin length, dorsal and anal fin depth, pre‐dorsal distance, body width) were observed between ages 4+ and 7+, which (in contrast to the relatively abrupt shift in maturity) suggests that age and size at maturation may not reflect the size and age of active (i.e. real) spawning.
• 3. Back‐calculated standard lengths at age for crucian carp were intermediate relative to other European populations, indicating that environmental conditions in England appear to be well suited to the species despite being at the westernmost extent of the species' native European range. The management of ornamental ponds specifically for crucian carp is discussed.

© Crown copyright 2007. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

A Simple Flow-through System for Toxicity Testing with Daphnids

A simple and accurate flow-through system was developed for toxicity evaluation of biodegradable substances, wastewaters, and surface waters. The chronic toxicity of phenol to the daphnid Daphnia magna was studied during a 21 d exposure period, first using a semi-static and later a flow-through test. The flow- through system was advantageous especially when lower concentrations of phenol were examined. Its use provided a constant concentration of phenol in all tested samples. Exposure to phenol showed a similar influence on both survival and reproduction of daphnids; the IC25 value was 3.18 mg L-1.     

Comparative performance of winter and spring malting barleys in semiarid growing conditions

In Europe, during the 1960s, mainly two-rowed spring barley was used for malting. Traditionally, spring malting barley was produced in regions with moderate temperatures and adequate rainfall throughout the growing season. Winter malting barley, on the other hand, was mostly grown in the milder arid and semiarid parts of Europe. Due to global climatic changes and its higher yield, winter malting barley is now increasing in acreage in the traditional spring barley regions. Our study included a comparative analysis of several grain and malt characters of the winter and spring malting barley grown under the agroecological conditions of the Vojvodina Province, Yugoslavia. One thousand grain weight was shown to be approximately the same for both growth habits, whereas winter malting barley proved to have a higher hectoliter mass than the spring one. In those years that were less favorable for spring barley production, winter malting barley had better quality characters, namely a higher fine extract content, a better malt modification, and a lower malt protein content. This revised version was published online in July 2006 with corrections to the Cover Date.