Autonomous in situ measurement of daily courses of the net CO2 exchange rate in a moss from alpine environment ( Short Communication )

Moss-dominated vegetation type is considered one of the the most productive community type in treeless alpine environments in European mountains. In this study, net carbon exchange rate (NCER) of alpine moss Polytrichum commune was measured by automatic CO2 exchange station unit. Samples of mosses were collected in a mountains from the site located above tree line (1420 m a.s.l.), and transferred to Brno, Czech Republic. Then the cluster of moss (23 cm in diameter, 30 cm in depth) including dead parts was placed into open measuring chamber end exposed to local climate for two weeks in autumn 2019. The chamber closed by a transparent lid repeatedly each 20 min and NCER measured by the system. Data on photosynthetically active radiation (PAR), relative air humidity (RH), and moss temperature (T) were recorded as well. Maximum/ minimum dark respiration reached 1.0 and 0.2 mmol (CO2) m-2 s-1. The highest NCER was found - 0.6 mmol (CO2) m-2 s-1 was caused by photosynthesis of moss clump at the temperature within the range of 14.5-17.5°C and 100% of relative air humidity

Oxygen evolution rate in Antarctic filamentous alga Stigeoclonium sp. evaluated by optodes relates to chlorophyll fluorescence parameters (Short Communication)

Photosynthetic reactions of algal communities, the essential component of primary production in polar regions, are strongly dependent on environmental factors. Among them, availability and amount of light in particular parts of growing season are of major importance. In this paper, the response of the photosynthetic processes of a filamentous fresh-water alga to photosynthetically active radiation (PAR) was studied by two approaches. The simultaneous measurements of the effective quantum yield (FPSII) and oxygen evolution rate (OER) at stepwise increasing photosynthetically active radiation provided data for beneficial correlation analysis of the FPSII to OER relationship in a wide range of PAR. In this study, the culture of filamentous alga Stigeoclonium sp. was analyzed. The linear relationship between FPSII and OER was found for the low PAR (the range of 0 – 200 mmol.m-2.s-1). At high PAR levels (200 – 1000 mmol.m-2.s-1) another linear relationship with different slope was found. The approach combining the fluorometric and oxymetric method might be used for calibration of data in follow up studies and, consequently for evaluation of photosynthetic rates (O2 evolution) from chlorophyll fluorescence data

Annual water temperature courses in two contrasting lakes at James Ross Island, Antarctica (Short Communication)

In this Short Communication, long-term temperature courses of two contrasting Antarctic lakes are presented. The lakes differed in their different location, size, and origin. Big Lachman Lake is a typical coastal shallow lake located on a terrace at an altitude of about 9 m. Dulánek Lake is a small-area, shallow kettle lake located in the lateral moraine composed of the back-arc alkaline volcanic rocks of the James Ross Island Volcanic Group at the height of about 220 m a.s.l. The data presented in this study support an idea that the water courses differed between the two lakes due to altitude and local microclimate. Similarly, significant differences in annual and summer-season courses of water temperature were apparent when several consecutive seasons were compared. Such differences have consequences for water invertebrates and autotrophic organisms because of episodic drying out of some lakes and/or formation of long-term lasting ice

Summer season variability of dissolved oxygen concentration in Antarctic lakes rich in cyanobaterial mats

Since 2007, limnological investigation of terrestrial lakes has been carried out at James Ross Island, Antarctica. The lakes in scope differ in their size, origin, geomorphological and hydrological characteristics. In several selected lakes, dissolved oxygen is measured repeatedly each summer season in order to quantify lake- and weather-related differences. For this study, typical reresentatives of (i) coastal shalow lakes, and (ii) high-altitude lakes with cyanobacterial mats were chosen. We present data on dissolved oxygen measured in 3 d interval during January 2010. Within this time, water temperature decreased gradually from 13 to 3 degC, as well as dissolved oxygen concentration. It varied within in the range of 12.50-18.0 mg l-1 indicating the values close to saturation and suprasaturation, respectively. Dissolved oxygen concentration showed slightly decreasing trend in a course of time. In majority of cases, the lakes with rich cyanobacterial flora showed higher dissolved oxygen concentrations than Lachman Lake 2 which posses less cyanobacterial mats than other the lakes involved into the study. Due to air temperature decrease, Dulanek lake, a high-altitude lake, froze in the last week of January 2010.Článek se zabývá měřeník koncentrace rozpuštěného kyslíku v několika jezerech severní odledněné části ostrova Jamese Rosse jako odrazu fotosyntetické aktivity autotrofů (řas a sinic) vyskytujících se v těchto jezerech.Since 2007, limnological investigation of terrestrial lakes has been carried out at James Ross Island, Antarctica. The lakes in scope differ in their size, origin, geomorphological and hydrological characteristics. In several selected lakes, dissolved oxygen is measured repeatedly each summer season in order to quantify lake- and weather-related differences. For this study, typical reresentatives of (i) coastal shalow lakes, and (ii) high-altitude lakes with cyanobacterial mats were chosen. We present data on dissolved oxygen measured in 3 d interval during January 2010. Within this time, water temperature decreased gradually from 13 to 3 degC, as well as dissolved oxygen concentration. It varied within in the range of 12.50-18.0 mg l-1 indicating the values close to saturation and suprasaturation, respectively. Dissolved oxygen concentration showed slightly decreasing trend in a course of time. In majority of cases, the lakes with rich cyanobacterial flora showed higher dissolved oxygen concentrations than Lachman Lake 2 which posses less cyanobacterial mats than other the lakes involved into the study. Due to air temperature decrease, Dulanek lake, a high-altitude lake, froze in the last week of January 2010

Multispectral aerial monitoring of a patchy vegetation oasis composed of different vegetation classes. UAV-based study exploiting spectral reflectance indices

The study brings data on monitoring of spectral refectance signatures of different components of Antarctic terrestrial vegetation by using a high-resolution multispectral images. The aim of the study was to compare several spots of a vegetation oasis by mapping vegetation cover using an UAV approach. This study provides data on vegetation distribution within a long-term research plot (LTRP) located at the northern coast of James Ross Island (Antarctica). Apart from normalized difference vegetation index (NDVI), 10 spectral reflectance indices (NDVI, NDVIRed-edge, RGBVI, NGRDI, ExG, TGI MSR, MSRRed-edge, Clgreen, ClRed-edge, GLI) were evaluated for different spots representing vegetation classes dominated by different Antarctic autotrophs. The UAV application and spectral reflectance indices proved their capability to detect and map small-area vegetated patches (with the smallest area of 10 cm2) dominated by different Antarctic autotrophs, and identify their classes (moss / lichens / biological soil crusts / microbiological mats / stream bottom microbiological mats). The methods used in our study revealed sufficiently high resolution of particular vegetation-covered surfaces and the spectral indices provided important indicators for environmental characteristics of the long-term research plot at the James Ross Island, Antarctica

Summer season variability of dissolved oxygen concentration in Antarctic lakes rich in cyanobaterial mats

Since 2007, limnological investigation of terrestrial lakes has been carried out at James Ross Island, Antarctica. The lakes in scope differ in their size, origin, geomorphological and hydrological characteristics. In several selected lakes, dissolved oxygen is measured repeatedly each summer season in order to quantify lake- and weather-related differences. For this study, typical reresentatives of (i) coastal shalow lakes, and (ii) high-altitude lakes with cyanobacterial mats were chosen. We present data on dissolved oxygen measured in 3 d interval during January 2010. Within this time, water temperature decreased gradually from 13 to 3oC, as well as dissolved oxygen concentration. It varied within in the range of 12.50-18.0 mg l-1 indicating the values close to saturation and suprasaturation, respectively. Dissolved oxygen concentration showed slightly decreasing trend in a course of time. In majority of cases, the lakes with rich cyanobacterial flora showed higher dissolved oxygen concentrations than Lachman Lake 2 which posses less cyanobacterial mats than other the lakes involved into the study. Due to air temperature decrease, Dulanek lake, a high-altitude lake, froze in the last week of January 2010

Long-term fluorometric measurements of photosynthetic processes in Antarctic moss Bryum sp. during austral summer season

Photosynthetic activity pattern of Bryum sp. was monitored for 28days using a chlorophyll a fluorescence measuring system installed in the field. For the study, long-term research plot, a moss-dominated vegetaiton oasis at seashore located close to the J.G. Mendel station (James Ross Island, Antarctica) was selected. In this study, two measuring sites were used: (1) control plot with moss cover and (2) moss located inside open top chamber (OTC). At both sites, effective quantum yield of photosynthetic processes in photosyntem II (FPSII) was measured and relative photosynthetic electron transport rate (ETRrel) evaluated each 15 min. Simultaneously, microclimate of the sites was measured including air and moss surface temperature, relative air humidity and photosynthetically active radiation. The length of photosyntetically active period depended mainly on hydration of moss cushion. Water availability, however, was not limiting in the measuring period (Jan 8 - Feb 18, 2009), because the sites were well suplied by melt water from neighbouring snowfield. Thus, daily courses of ETRrel were dependent on incident PAR. On sunny days, ETRrel reached values over 400. Inhibition of primary photosynthetic processes due to below-zero temperature and resulting freezing of moss cushions appeared two times within the measuring periods thanks to rapid decreases in air temperature. The effect of low air temperature on ETRrel was less apparent in OTC site since moss cushion freezing period was shorter and less pronounced than in control site thanks to OTC-induced shift in air temperature. For future photosynthetic studies in Antarctic mosses, simultaneous measurements of gas exchange- and chlorophyll fluorescence-related parameters is recommended so that the effects of particular limiting factors for photosynthesis and photosynthetic productivity can be distinguished and evaluated

Diurnal changes in photosynthetic activity of the biological soil crust and lichen: Effects of abiotic factors (Petuniabukta, Svalbard)

In polar ecosystems, primary producers have to cope with a very harsh climate that limits the time available for growth and biomass production. In this study, diurnal measurement of photosynthetic processes in biological soil crust and a lichen were carried out in Petuniabukta, Spitsbergen. For field measurements, a method of induced fluorescence of chlorophyll was used. Measurements of photosynthetic activity were taken as repetitive measurements of effective quantum yield of photosystem II (PhiPSII). The short-term field measurements were carried out for 10 days in summer 2014. PhiPSII was recorded each 5 minutes as well as microclimatic data (air temperature, air humidity, photosynthetically active radiation - PAR). The microclimatic parameters were recorded by a datalogger. In general, physiological activity of both biological soil crust and a lichen showed daily courses. Tested lichen was Cladonia rangiferina and the most dominant species in biological soil crust was Nostoc sp. Typically, most of PhiPSII values ranged 0.6 – 0.7 in both model organisms. The results have shown that photosynthetic activity was strongly correlated with all observed abiotic factors in both study objects. Particularly important was the relation found between PAR and PhiPSII in biological soil crust. When the biological soil crust was exposed to high PAR doses of irradiation (about 2300 micromol m-2 s-1) photoinhibition of primary processes of photosynthesis was observed as PhiPSII decrease, while photosynthetic activity of lichen remained at same level. Furthermore, it has been demonstrated increasing that in situ photosynthetic activity increased in both biological soil crust and lichen with a decrease in temperature.Byly sledovány primární fotoszntetické procesy biologické půdní krusy a lišejníku. Studie byla uskutečněna v terénu na Špicberkách.In polar ecosystems, primary producers have to cope with a very harsh climate that limits the time available for growth and biomass production. In this study, diurnal measurement of photosynthetic processes in biological soil crust and a lichen were carried out in Petuniabukta, Spitsbergen. For field measurements, a method of induced fluorescence of chlorophyll was used. Measurements of photosynthetic activity were taken as repetitive measurements of effective quantum yield of photosystem II (PhiPSII). The short-term field measurements were carried out for 10 days in summer 2014. PhiPSII was recorded each 5 minutes as well as microclimatic data (air temperature, air humidity, photosynthetically active radiation - PAR). The microclimatic parameters were recorded by a datalogger. In general, physiological activity of both biological soil crust and a lichen showed daily courses. Tested lichen was Cladonia rangiferina and the most dominant species in biological soil crust was Nostoc sp. Typically, most of PhiPSII values ranged 0.6 – 0.7 in both model organisms. The results have shown that photosynthetic activity was strongly correlated with all observed abiotic factors in both study objects. Particularly important was the relation found between PAR and PhiPSII in biological soil crust. When the biological soil crust was exposed to high PAR doses of irradiation (about 2300 micromol m-2 s-1) photoinhibition of primary processes of photosynthesis was observed as PhiPSII decrease, while photosynthetic activity of lichen remained at same level. Furthermore, it has been demonstrated increasing that in situ photosynthetic activity increased in both biological soil crust and lichen with a decrease in temperature

Diurnal changes in photosynthetic activity of the biological soil crust and lichen: Effects of abiotic factors (Petuniabukta, Svalbard)

In polar ecosystems, primary producers have to cope with a very harsh climate that limits the time available for growth and biomass production. In this study, diurnal measurement of photosynthetic processes in biological soil crust and a lichen were carried out in Petuniabukta, Spitsbergen. For field measurements, a method of induced fluorescence of chlorophyll was used. Measurements of photosynthetic activity were taken as repetitive measurements of effective quantum yield of photosystem II (ΦPSII). The short-term field measurements were carried out for 10 days in summer 2014. ΦPSII was recorded each 5 minutes as well as microclimatic data (air temperature, air humidi-ty, photosynthetically active radiation - PAR). The microclimatic parameters were recorded by a datalogger. In general, physiological activity of both biological soil crust and a lichen showed daily courses. Tested lichen was Cladonia rangiferina and the most dominant species in biological soil crust was Nostoc sp. Typically, most of ΦPSII values ranged 0.6 – 0.7 in both model organisms. The results have shown that photosynthetic activity was strongly correlated with all observed abiotic factors in both study objects. Particularly important was the relation found between PAR and ΦPSII in biological soil crust. When the biological soil crust was exposed to high PAR doses of irradiation (about 2300 µmol m-2 s-1) photoinhibition of primary processes of photosynthesis was observed as ΦPSII decrease, while photosynthetic activity of lichen remained at same level. Furthermore, it has been demonstrated increasing that in situ photosynthetic activity increased in both biological soil crust and lichen with a decrease in temperature