Is oxygenation related to the decomposition of organic matter in cryoconite holes?

Cryoconite is a sediment occurring on glacier surfaces worldwide which reduces ice albedo and concentrates glacier surface meltwater into small reservoirs called cryoconite holes. It consists of mineral and biogenic matter, including active microorganisms. This study presents an experimental insight into the influence of sediment oxygenation on the cryoconite ability to produce and decomposition of organic matter. Samples were collected from five glaciers in the Arctic and the European mainland. Cryoconite from three glaciers was incubated in stagnant and mechanically mixed conditions to imitate inter-hole water–sediment mixing by meltwater occurring on glaciers in Northern Hemisphere, and its effect on oxygen profiles and organic matter content. Moreover, we investigated short-term changes of oxygen conditions in cryoconite from four glaciers in illuminated and dark conditions. An anaerobic zone was present or approaching zero oxygen in all illuminated cryoconite samples, varying in depth depending on the origin of cryoconite: from 1500 µm from Steindalsbreen (Scandinavian Peninsula) and Forni Glacier (The Alps) to 3100 µm from Russell Glacier and Longyearbreen (Arctic) after incubation. Organic matter content varied between glaciers from 6.11% on Longyearbreen to 16.36% on Russell Glacier. The mixed sediment from the Forni Glacier had less organic matter than stagnant, the sediment from Longyearbreen followed this trend, but the difference was not statistically significant, while the sediment from Ebenferner did not differ between groups. Our results have implications for the understanding of biogeochemical processes on glacier surfaces, the adaptation of organisms to changing physical conditions due to abrupt sediment mixing, but also on the estimation of productivity of supraglacial systems

Influence of photo- and chromatic acclimation on pigment composition in the sea

The aim of this work was to find statistical relationships between the concentrations of accessory pigments in natural populations of marine phytoplankton and the absolute levels and spectral distributions of underwater irradiance. To this end, empirical data sets from some 600 stations in different parts of the seas and oceans were analysed. These data were obtained from the authors' own research and from the Internet's bio-optical data base. They included the vertical distributions of the concentrations of various pigments (identified chromatographically) and the vertical and spectral distributions of the underwater irradiance measured in situ or determined indirectly from bio-optical models. The analysis covered a total of some 4000 points illustrating the dependence of pigment concentration on underwater irradiance characteristics, corresponding to different depths in the sea. The analysis showed that the factor governing the occurrence of photoprotecting carotenoids (PPC) is short-wave radiation λ a concentration) and the magnitude of the absorbed radiative energy per unit mass of chlorophyll a from the spectral interval λ z = 60 m (or less near the surface) to account for vertical mixing. This absorbed short-wave radiation (λ *(z)). Analysis of the relationships between the concentrations of particular photosynthetic pigments (PSP), i.e. chlorophyll b, chlorophyll c, photosynthetic carotenoids (PSC), and the underwater irradiance characteristics indicated that these concentrations were only slightly dependent on the absolute level of irradiance E0(λ), but that they depended strongly on the relative spectral distribution of this irradiance f(λ)= E0(λ)/PAR0. The relevant approximate statistical relationships between the relative concentrations of particular PSP and the function of spectral fitting Fj, averaged in the layer Δz, were derived. Certain statistical relationships between the pigment composition of the phytoplankton and the irradiance field characteristics are due to the photo- and chromatic acclimation of natural populations of marine phytoplankton. These relationships can be applied in models of the coefficients of light absorption by phytoplankton

Variability of the specific fluorescence of chlorophyll in the ocean. Part 2. Fluorometric method of chlorophyll a determination

Two methods of determining the chlorophyll <i>a</i> concentration in the sea have been formulated on the basis of artificially induced fluorescence measured with the aid of submersible fluorometers. The method of statistical correlation is founded on the empirical relationship between fluorescence and chlorophyll concentration. The theoretical model of fluorescence described in Part 1 of this paper (see Ostrowska <i>et al.</i> 2000, this volume) provides the basis of the other method, the physical method. This describes the dependence of the specific fluorescence of phytoplankton on the chlorophyll concentration, a diversity of photophysiological properties of phytoplankton and the optical characteristics of the fluorometer. <br> &nbsp;&nbsp;&nbsp;&nbsp;In order to assess their practicability, the methods were subjected to empirical verification. This showed that the physical method yielded chlorophyll concentrations of far greater accuracy. The respective error factors of the estimated chlorophyll concentration were <i>x</i> = 2.07 for the correlation method and <i>x</i> = 1.5 for the physical method. This means that the statistical logarithmic error varies from -52 to +107% in the case of the former method but only from -33 to +51% in the case of the latter. Thus, modifying the methodology has much improved the accuracy of chlorophyll determinations

Genetic relationship between Polish and Chinese strains of the mushroom Agaricus bisporus (Lange) Sing., determined by the RAPD method

Abstract. The genetic relationship between twenty-six strains of Agaricus bisporus were analysed by the RAPD (random amplified polymorphic DNA) method. DNA amplification was performed with the use of twelve arbitrary 10-mer primers. Four primers, which gave polymorphic band patterns were chosen for RAPD analysis. In total, they gave 24 distinguishable bands, of which nine were polymorphic. The conducted research showed that there is a great genetic similarity among the examined strains. Low polymorphism of the strains may be a proof of a limited genetic pool used in the cultivation of those strains

Measurement of phytoplankton photosynthesis rate using a <i>pump-and-probe</i> fluorometer

In this work we have studied the possibility of determining the rate of phytoplankton photosynthesis in situ using a submersible pump-and-probe fluorometer in water areas differing in their trophic level, as well as in climatic and hydrophysical characteristics. A biophysical model was used to describe the relationship between photosynthesis, underwater irradiance, and the intensity of phytoplankton fluorescence excited by an artificial light source. Fluorescence intensity was used as a measure of light absorption by phytoplankton and for assessing the efficiency of photochemical energy conversion at photosynthetic reaction centers. Parameters of the model that could not be measured experimentally were determined by calibrating fluorescence and irradiance data against the primary production measured in the Baltic Sea with the radioactive carbon method. It was shown that the standard deviation of these parameters in situ did not exceed 20%, and the use of their mean values to estimate the phytoplankton photosynthetic rate showed a good correlation between the calculated and mea