High diversity of root associated fungi in both alpine and arctic Dryas octopetala

<p>Abstract</p> <p>Background</p> <p><it>Dryas octopetala </it>is a widespread dwarf shrub in alpine and arctic regions that forms ectomycorrhizal (ECM) symbiotic relationships with fungi. In this study we investigated the fungal communities associated with roots of <it>D. octopetala </it>in alpine sites in Norway and in the High Arctic on Svalbard, where we aimed to reveal whether the fungal diversity and species composition varied across the Alpine and Arctic regions. The internal transcribed spacer (ITS) region of nuclear ribosomal DNA was used to identify the fungal communities from bulk root samples obtained from 24 plants.</p> <p>Results</p> <p>A total of 137 operational taxonomic units (OTUs) were detected (using 97% similarity cut off during sequence clustering) and well-known ECM genera such as <it>Cenococcum</it>, <it>Cortinarius, Hebeloma</it>, <it>Inocybe </it>and <it>Tomentella </it>occurred frequently. There was no decrease in fungal diversity with increasing latitude. The overall spatial heterogeneity was high, but a weak geographical structuring of the composition of OTUs in the root systems was observed. Calculated species accumulation curves did not level off.</p> <p>Conclusions</p> <p>This study indicates that the diversity of fungi associated with <it>D. octopetala </it>does not decrease in high latitude arctic regions, which contrasts observations made in a wide spectrum of other organism groups. A high degree of patchiness was observed across root systems, but the fungal communities were nevertheless weakly spatially structured. Non-asymptotical species accumulation curves and the occurrence of a high number of singletons indicated that only a small fraction of the fungal diversity was detected.</p

Impact and restitution model - Water column. ERA Acute for water column exposed organisms

Exposure to oil components in the water column in ERA Acute can be modelled using either of two alternative options in the oil spill model OSCAR. While the option based on the Critical Body Residue (CBR) takes changing oil properties/toxicities and exposure time into account and therefore represents a scientifically more valid approach, an alternative and more conservative option based on the modelled maximum total hydrocarbon (THC) concentrations over the whole water column is also described. A global fish restitution model has been developed based on historical recruitment data, and demonstrating strong links between the climatic regime and natural fluctuations of fish stocks. Restitution modelling shows that as long as impact is assessed on the reproductive unit (spawning stock), even a major oil spill will not have a measurable effect on fish stocks. Higher risk may apply if fish larvae are considered representing a valuable resource in itself, e.g. as a planktonic food source of predating organisms, but this is not within the scope of this project.publishedVersio

Aspects of growth in Arctic cod, Boreogadus saida (Lepechin 1773)

In June 1986- 42 young Arctic cod were caught in ice-covered waters of the Barents sea with dip-nets by scuba divers. From August to June 1987 the fish were kept at -PC and fed on frozen shrimp (Pandalus borealis). Length and weight were measured monthly. A fast weight increment of about 0.7% per day was observed in the autumn (Sept.-Nov.). In the winter (Jan.-Feb), the growth rate declined to 0.05% per day. However, daily food intake only decreased by 50% during these winter months. Since the fish were exposed to constant illumination in the aquarium, this growth experiment indicates that something else than light has a significant influence on growth in Arctic cod

Harp seal (Phoca Groenlandica) invasions in north Norwegian coastal waters: A preliminary report on age composition and feeding habits

Since 1978 large numbers of harp seals (Phoca groenlandica) have invaded areas of North Norway in winter and spring. In 1987 and 1988 dramatic increases occurred both in magnitude and geographic extent of these seal invasions, and it is suggested that the collapse of the Barents Sea capelin stock in 1985/1986 may have been a contributory factor to this. Sampling of stomach contents for food analyses and of teeth for age determinations was carried out from harp seals taken as bycatch in Norwegian gill-net fisheries in 1986 and 1988. It appears that the seal herds comprised both immature and mature animals. The stomach analyses suggested that feeding was opportunistic, with a variety of fish (in particular the gadoid species cod, saithe, haddock and Norway pout, and the pelagic shoaling species herring and capelin) being taken as prey. Prawns and squid were also consumed, but in considerably lower quantities than fish

Temporal and spatial dynamics of diatom (Bacillariophyceae) communities in a peatland area

This study was conducted to simultaneously investigate the spatial and temporal dynamics of diatom communities inhabiting two microhabitat types (Sphagnum periphyton and epipelon) in a peatland area of the Czech Republic. The changes in diatom community structure and corresponding diversity indices at both large (i.e., variation between sites) and small (i.e., variation between two microhabitats) scales were assessed through time. The results indicated clear spatial patterns at large, but not at small scale, and only limited seasonal dynamics in the diatom community. At the large scale, significant differences in diatom communities among sites were associated with both geographic position and environmental conditions (pH and conductivity). A significant effect of microhabitat type was detectable within sampling sites; the relationship between other factors and species data was not important on a small scale. The results of this study showed that both diatom diversity and community structure are good indicators of ecological heterogeneity associated with relatively high spatial and/or environmental variability. However, subtle differences in environmental conditions are hardly detectable or hidden using traditional diatom species.</p

Temporal and Spatial Dynamics of Diatom (Bacillariophyceae) Communities in a Peatland Area

This study was conducted to simultaneously investigate the spatial and temporal dynamics of diatom communities inhabiting two microhabitat types (Sphagnum periphyton and epipelon) in a peatland area of the Czech Republic. The changes in diatom community structure and corresponding diversity indices at both large (i.e., variation between sites) and small (i.e., variation between two microhabitats) scales were assessed through time. The results indicated clear spatial patterns at large, but not at small scale, and only limited seasonal dynamics in the diatom community. At the large scale, significant differences in diatom communities among sites were associated with both geographic position and environmental conditions (pH and conductivity). A significant effect of microhabitat type was detectable within sampling sites; the relationship between other factors and species data was not important on a small scale. The results of this study showed that both diatom diversity and community structure are good indicators of ecological heterogeneity associated with relatively high spatial and/or environmental variability. However, subtle differences in environmental conditions are hardly detectable or hidden using traditional diatom species

Temporal and Spatial Dynamics of Diatom (Bacillariophyceae) Communities in a Peatland Area

This study was conducted to simultaneously investigate the spatial and temporal dynamics of diatom communities inhabiting two microhabitat types (Sphagnum periphyton and epipelon) in a peatland area of the Czech Republic. The changes in diatom community structure and corresponding diversity indices at both large (i.e., variation between sites) and small (i.e., variation between two microhabitats) scales were assessed through time. The results indicated clear spatial patterns at large, but not at small scale, and only limited seasonal dynamics in the diatom community. At the large scale, significant differences in diatom communities among sites were associated with both geographic position and environmental conditions (pH and conductivity). A significant effect of microhabitat type was detectable within sampling sites; the relationship between other factors and species data was not important on a small scale. The results of this study showed that both diatom diversity and community structure are good indicators of ecological heterogeneity associated with relatively high spatial and/or environmental variability. However, subtle differences in environmental conditions are hardly detectable or hidden using traditional diatom species

Sealworm (<i>Pseudoterranova decipiens</i>) infection in the benthic cottid (<i>Taurulus bubalis</i>) in relation to population increase of harbour seal (<i>Phoca vitulina</i>) in Skagerrak, Sweden

In Koster archipelago (northern Skagerrak, Sweden) the harbour seal population increased from approximately 350 to more than 1000 individuals between 1988 and 1998. During the same period, sealworm (Pseudoterranova decipiens) abundance in the most heavily infected fish species, bullrout (Myoxocepahulus scorpius) and sea scorpion (Taurulus bubalis), did not increase. Since harbour seals do not normally feed on those cottids an infection route via cod (Gadus morhua), which consume cottids, is proposed. The abundance of sealworm in the final host is therefore related to the probability of cod preying on infected cottids prior to being preyed upon by seals. Our model predicts that the abundance of larval sealworm in benthic fishes is not related to the number of seals when the colony is over a specific threshold size

Social behaviour in mesopelagic jellyfish

Gelatinous organisms apparently play a central role in deep pelagic ecosystems, but lack of observational methodologies has restricted information on their behaviour. We made acoustic records of diel migrating jellyfish Periphylla periphylla forming small, ephemeral groups at the upper fringe of an acoustic scattering layer consisting of krill. Groups of P. periphylla were also documented photographically using a remotely operated vehicle (ROV). Although the adaptive value of group formation remains speculative, we clearly demonstrate the ability of these jellyfishes to locate and team up with each other

An approach based on the total-species accumulation curve and higher taxon richness to estimate realistic upper limits in regional species richness

Most of accumulation curves tend to underestimate species richness, as they do not consider spatial heterogeneity in species distribution, or are structured to provide lower bound estimates and limited extrapolations. The total‐species (T–S) curve allows extrapolations over large areas while taking into account spatial heterogeneity, making this estimator more prone to attempt upper bound estimates of regional species richness. However, the T–S curve may overestimate species richness due to (1) the mismatch among the spatial units used in the accumulation model and the actual units of variation in β‐diversity across the region, (2) small‐scale patchiness, and/or (3) patterns of rarity of species. We propose a new framework allowing the T–S curve to limit overestimation and give an application to a large dataset of marine mollusks spanning over 11 km2 of subtidal bottom (W Mediterranean). As accumulation patterns are closely related across the taxonomic hierarchy up to family level, improvements of the T–S curve leading to more realistic estimates of family richness, that is, not exceeding the maximum number of known families potentially present in the area, can be considered as conducive to more realistic estimates of species richness. Results on real data showed that improvements of the T–S curve to accounts for true variations in β‐diversity within the sampled areas, small‐scale patchiness, and rarity of families led to the most plausible richness when all aspects were considered in the model. Data on simulated communities indicated that in the presence of high heterogeneity, and when the proportion of rare species was not excessive (>2/3), the procedure led to almost unbiased estimates. Our findings highlighted the central role of variations in β‐diversity within the region when attempting to estimate species richness, providing a general framework exploiting the properties of the T–S curve and known family richness to estimate plausible upper bounds in γ‐diversity