Browsing by Subject "ekofysiologia"

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  • Kellomäki, Seppo; Hari, Pertti (Suomen metsätieteellinen seura, 1980)
  • Kellomäki, Seppo; Hari, Pertti; Kanninen, Markku; Ilonen, Pirkko (Suomen metsätieteellinen seura, 1980)
  • Mäkelä, Annikki; Kellomäki, Seppo; Hari, Pertti (Suomen metsätieteellinen seura, 1980)
  • Kellomäki, Seppo; Kanninen, Markku (Suomen metsätieteellinen seura, 1980)
  • Lehtonen, Kari K. (Finnish Institute of Marine Research, 1997)
    Monographs of the Boreal Environment Research 7
  • Seppälä, Jukka (Finnish Environment Institute, 2009)
    Monographs of the Boreal Environment Research 34
    To obtain data on phytoplankton dynamics (abundance, taxonomy, productivity, and physiology) with improved spatial and temporal resolution, and at reduced cost, traditional phytoplankton monitoring methods have been supplemented with optical approaches. Fluorescence detection of living phytoplankton is very sensitive and not disturbed much by the other optically active components. Fluorescence results are easy to generate, but interpretation of measurements is not straightforward as phytoplankton fluorescence is determined by light absorption, light reabsorption, and quantum yield of fluorescence - all of which are affected by the physiological state of the cells. In this thesis, I have explored various fluorescence-based techniques for detection of phytoplankton abundance, taxonomy and physiology in the Baltic Sea.In algal cultures used in this thesis, the availability of nitrogen and light conditions caused changes in pigmentation, and consequently in light absorption and fluorescence properties of cells. The variation of absorption and fluorescence properties of natural phytoplankton populations in the Baltic Sea was more complex. Physical environmental factors (e.g. mixing depth, irradiance and temperature) and related seasonal succession in the phytoplankton community explained a large part of the seasonal variability in the magnitude and shape of Chlorophyll a (Chla)-specific absorption. Subsequent variations in the variables affecting fluorescence were large; 2.4-fold for light reabsorption at the red Chla peak and 7-fold for the spectrally averaged Chla-specific absorption coefficient for Photosystem II. In the studies included in this thesis, Chla-specific fluorescence varied 2-10 fold. This variability in Chla-specific fluorescence was related to the abundance of cyanobacteria, the size structure of the phytoplankton community, and absorption characteristics of phytoplankton.Cyanobacteria show very low Chla-specific fluorescence. In the presence of eukaryotic species, Chla fluorescence describes poorly cyanobacteria. During cyanobacterial bloom in the Baltic Sea, phycocyanin fluorescence explained large part of the variability in Chla concentrations. Thus, both Chla and phycocyanin fluorescence were required to predict Chla concentration.Phycobilins are major light harvesting pigments for cyanobacteria. In the open Baltic Sea, small picoplanktonic cyanobacteria were the main source of phycoerythrin fluorescence and absorption signal. Large filamentous cyanobacteria, forming harmful blooms, were the main source of the phycocyanin fluorescence signal and typically their biomass and phycocyanin fluorescence were linearly related. It was shown that for reliable phycocyanin detection, instrument wavebands must match the actual phycocyanin fluorescence peak well. In order to initiate an operational ship-of-opportunity monitoring of cyanobacterial blooms in the Baltic Sea, the distribution of filamentous cyanobacteria was followed in 2005 using phycocyanin fluorescence.Various taxonomic phytoplankton pigment groups can be separated by spectral fluorescence. I compared multivariate calibration methods for the retrieval of phytoplankton biomass in different taxonomic groups. During a mesocosm experiment, a partial least squares regression method gave the closest predictions for all taxonomic groups, and the accuracy was adequate for phytoplankton bloom detection. This method was noted applicable especially in the cases when not all of the optically active compounds are known.Variable fluorescence has been proposed as a tool to study the physiological state of phytoplankton. My results from the Baltic Sea emphasize that variable fluorescence alone cannot be used to detect nutrient limitation of phytoplankton. However, when combined with experiments with active nutrient manipulation, and other nutrient limitation indices, variable fluorescence provided valuable information on the physiological responses of the phytoplankton community. This thesis found a severe limitation of a commercial fast repetition rate fluorometer, which couldn’t detect the variable fluorescence of phycoerythrin-lacking cyanobacteria. For these species, the Photosystem II absorption of blue light is very low, and fluorometer excitation light did not saturate Photosystem II during a measurement.This thesis encourages the use of various in vivo fluorescence methods for the detection of bulk phytoplankton biomass, biomass of cyanobacteria, chemotaxonomy of phytoplankton community, and phytoplankton physiology. Fluorescence methods can support traditional phytoplankton monitoring by providing continuous measurements of phytoplankton, and thereby strengthen the understanding of the links between biological, chemical and physical processes in aquatic ecosystems.
  • Hänninen, Heikki (Suomen metsätieteellinen seura, 1986)
  • Korpilahti, Eeva (Suomen metsätieteellinen seura, 1988)
    Data were collected over 3 yr during the growing season in a 20-yr-old stand at the Forestry Field Station of the University of Helsinki, Finland, to study the relations of photosynthesis and transpiration to environmental factors (irradiance, temperature, water content of soil and air) and metabolic processes.
  • Luangjame, Jesada (The Society of Forestry in Finland - The Finnish Forest Research Institute, 1990)
    In a study of two salt-tolerant tree species, Combretum quadrangulare and Eucalyptus camaldulensis, results from a greenhouse experiment with NaCl salinity of 0, 0.5, 1.0, 1.5 and 2.0% were compared with those of a field study on non-saline and saline soils in north-eastern Thailand. Determination of optimum gas exchange and development and evaluation of photosynthetic models with and without water deficit were included. Shoot height and diameter growth, shoot internode length, root length/biomass, leaf width and length, leaf area, number and biomass, and shoot:root and leaf:root ratios decreased with salinity, while leaf thickness increased with salinity. More growth occurred in roots than in the leaf canopy. In the laboratory, photosynthesis, stomatal conductance and water potential decreased with salinity, while CO2 compensation point increased with salinity. Transpiration, dark respiration and photorespiration increased at low salinity but decreased at high salinity. In the field study, however, there were no significant differences in stomatal conductance and opening between saline and non-saline soils. Model predictions supported results of the field measurements. Adaptation of salinity was reflected in an acclimatization of tree structure in the field study. There were both functioning and structural changes of seedlings in the greenhouse experiment. In terms of ecophysiological and morphological characteristics, E. camaldulensis showed better salt tolerance than C. quadrangulare in both the greenhouse experiment and field study.
  • Kellomäki, Seppo; Oker-Blom, Pauline (Suomen metsätieteellinen seura, 1981)