Scales of horizontal patchiness in chlorophyll a, chemical and physical properties of landfast sea ice in the Gulf of Finland (Baltic Sea)

Horizontal variation of first-year landfast sea ice properties was studied in the Gulf of Finland, the Baltic Sea. Several scales of variation were considered; a number of arrays with core spacings of 0.2, 2 and 20 m were sampled at different stages of the ice season for small-scale patchiness. Spacing between these arrays was from hundreds of meters to kilometers to study mesoscale variability, and once an onshore–offshore 40-km transect was sampled to study regional scale variability. Measured variables included salinity, stable oxygen isotopes (¹⁸O), chlorophyll a (chl-a), nutrients and dissolved organic carbon. On a large scale, a combination of variations in the under-ice water salinity (ice porosity), nutrient supply and the stage of ice development control the build-up of ice algal biomass. At scales of hundreds of meters to kilometers, there was significant variability in several parameters (salinity, chl-a, snow depth and ice thickness). Analyses of the data from the arrays did not show evidence of significant patchiness at scales <20 m for algal biomass. The results imply that the sampling effort in Baltic Sea ice studies should be concentrated on scales of hundreds of meters to kilometers. Using the variations observed in the study area, the estimate for depth-integrated algal biomass in landfast sea ice in the Gulf of Finland (March 2003) is 5.5±4.4 mg chl-a m^–2.     

Seasonal depletion of resources intensifies trophic interactions in subarctic freshwater fish communities

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Oxygen and carbon isoscapes for the Baltic Sea: Testing their applicability in fish migration studies

Conventional tags applied to individuals have been used to investigate animal movement, but these methods require tagged individuals be recaptured. Maps of regional isotopic variability known as “isoscapes” offer potential for various applications in migration research without tagging wherein isotope values of tissues are compared to environmental isotope values. In this study, we present the spatial variability in oxygen () and dissolved inorganic carbon (δ¹³C_DIC) isotope values of Baltic Sea water. We also provide an example of how these isoscapes can reveal locations of individual animal via spatial probability surface maps, using the high‐resolution salmon otolith isotope data from salmon during their sea‐feeding phase in the Baltic Sea. A clear latitudinal and vertical gradient was found for both and δ¹³C_DIC values. The difference between summer and winter in the Baltic Sea values was only slight, whereas δ¹³C_DIC values exhibited substantial seasonal variability related to algal productivity. Salmon otolith δ¹⁸O_oto and δ¹³C_oto values showed clear differences between feeding areas and seasons. Our example demonstrates that dual isotope approach offers great potential for estimating probable fish habitats once issues in model parameterization have been resolved.     

Cathepsin C activity as related to some histochemical substrates

Summary Hog kidney homogenate was fractionated initially following the steps presented by De La Haba et al. (1959) for the purification of cathepsin C from beef spleen. The preparation was further fractionated by gel filtration using Sephadex G 200, starch gel and immunoelectrophoresis. The following enzymes were identified in the fractions obtained:Cathepsin C, which liberated ammonia from glycyl-phenylalanine amide and naphthylamine from glycyl-phenylalanyl--naphthylamide, pH optimum at 5.0, was activated by cysteine and inhibited by sulfhydryl reagents.An aminopeptidase, which liberated first of all glycine from glycyl-phenylalanine amide and glycyl-phenylalanyl--naphtylainide and after that ammonia and naphthylamine, respectively, hydrolysed numerous amino acid naphthylamides, pH optimum at 7.0–7.5, was activated by Co⁺⁺ and inhibited by EDTA.A peptidase, which liberated glycine from glycyl-phenylalanine amide and naphthylamide, did not hydrolyse amino acid naphthylamides, maximally active at neutral pH, was inhibited by EDTA.Several esterases, two in gel filtration, 5–6 in starch gel and immunoelectrophoresis, hydrolysing 5-bromoindoxyl acetate. The activities were sensitive to E 600.Both the studies on the characteristics of these activities as well as starch gel and immunoelectrophoretic studies support the view that none of the esterase activities is identical with cathepsin C. Cathepsin C, on the other hand, does not hydrolyse significantly 5-bromoindoxyl acetate and, consequently, this substrate can not be used to demonstrate cathepsin C histochemically.Glycyl-phenylalanyl--naphthylamide is recommended as a new sensitive chromogenic substrate for cathepsin C in biochemical studies in which the role of the aminopeptidase (s) can be adequately excluded but cannot be used in the histochemical demonstration of this enzyme.     

Spatial variability and temporal trends in water‐use efficiency of European forests

The increasing carbon dioxide (CO₂) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree‐ring sites located across Europe are investigated to determine the intrinsic water‐use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared with simulations of a dynamic vegetation model (LPX‐Bern 1.0) that integrates numerous ecosystem and land–atmosphere exchange processes in a theoretical framework. The spatial pattern of tree‐ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south‐to‐north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil‐water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO₂ and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation–climate feedbacks are currently still poorly constrained by observational data.     

Adaptive Radiation along a Thermal Gradient: Preliminary Results of Habitat Use and Respiration Rate Divergence among Whitefish Morphs

Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L.)) morphs (two pelagic, one littoral and one profundal) using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one profundal recently diverged via adaptive radiation to exploit different major niches in a deep and thermally stratified subarctic lake. We found evidence that the morphs used different thermal niches. The profundal morph had the most distinct thermal niche and consistently occupied the coldest thermal habitat of the lake, whereas differences were less pronounced among the shallow water pelagic and littoral morphs. Our results indicated ontogenetic shifts in thermal niches: juveniles of all whitefish morphs inhabited warmer ambient temperatures than adults. According to sampling of the otolith nucleus, hatching temperatures were higher for benthic compared to pelagic morphs. Estimated respiration rate was the lowest for benthivorous profundal morph, contrasting with the higher values estimated for the other morphs that inhabited shallower and warmer water. These preliminary results suggest that physiological adaptation to different thermal habitats shown by the sympatric morphs may play a significant role in maintaining or strengthening niche segregation and divergence in life-history traits, potentially contributing to reproductive isolation and incipient speciation.     

Linkage studies in a new X-linked myopathy, suggesting exclusion of DMD locus and tentative assignment to distal Xq.

We here report linkage studies in a family suffering from a recently described hereditary muscle disease named X-linked myopathy with excessive autophagy (XMEA). Significant lod scores excluding linkage to the Duchenne-Becker muscular dystrophy locus were found. Several other loci on the short and long arms of the X chromosome produced negative lod scores, whereas probe DX13-7 defining locus DXS15 showed no recombinants and a lod score of z = 0.903 at theta = .0. Further studies should be done to determine whether the gene for XMEA is (1) located at Xq and (2) caused by a mutation of the Emery-Dreifuss muscular dystrophy gene, which has been assigned to the same region.