Natural water bodies, such as lakes, rivers, and oceans, are important sources of atmospheric met... more Natural water bodies, such as lakes, rivers, and oceans, are important sources of atmospheric methane (CH4). Therefore, quantitative and accurate determination of the dissolved CH4 concentration in water is of great significance for studying CH4 emissions and providing an in-depth understanding of the carbon cycle. Headspace gas chromatography (HGC) is the traditional method for measuring CH4 in water. Despite its long success, it has a lot of problems in use, such as complex pretreatment and a long measurement time, and it is not suitable for the CH4 determination of a large number of samples. In view of these shortcomings, a more convenient and efficient method based on membrane inlet mass spectrometry (MIMS) for quantitative measurements of the dissolved CH4 concentration in water was established. In our study, the standard curves showed that the method had high accuracy, both at low and high CH4 concentrations. After a laboratory test, to evaluate the sensitivity of this method,...
A new ''0 isotope dilution technique is presented and examples are given of the determination of ... more A new ''0 isotope dilution technique is presented and examples are given of the determination of true gross oxygen evolution (photosynthesis) and oxygen uptake (respiration) in plankton samples from estuarine surface waters and in the seagrass Zostera marina. The technique involves enriching dissolved oxygen with 3602, and measuring changes in isotope enrichment and oxygen concentration with time. It is relatively simple to apply, and less expensive than previously used 180 methods. Oxygen uptake rates of plankton samples incubated under various light conditions ranged from 0.75 to 10 times that in darkness. Gross oxygen evolution rates determined by isotope dilution were from 0 to 80 % higher than gross oxygen evolution rates calculated from parallel light and dark bottle experiments and ranged between 180 and 800 FM O2 (FM chl a)-' h-'. Ratios of gross oxygen uptake to gross oxygen evolution were between 0.12 and 0.67 and depended on both light intensity and sampling time. Occasionally, net oxygen evolution and isotope ddution occurred in darkened bottles, suggesting the existence of a non-photosynthetic process that produces new oxygen. In 2. marina, oxygen uptake at saturating light intensities was 4.7 times the rate in darkness. The data indicate the existence of significant, but variable, light stimulation of oxygen consumption in estuarine waters and higher rates of gross oxygen production than measured by the light and dark bottle technique.
Deep-Sea Research Part a-Oceanographic Research Papers, 1987
We investigated the photosynthetic behavior of Synechococcas WH7803 when grown over the irradianc... more We investigated the photosynthetic behavior of Synechococcas WH7803 when grown over the irradiance range of 30-200(I laE m 2 s ~ in nutrient-replete, continuous light, preadapted batch cultures. For each of 8 growth irradiances investigated, we found a unique photosynthesis vs irradiance (P vs 1) relationship. Cell-and carbon-specific photosynthetic light harvesting efficiencies (cq,.,.n) and ct¢c)) decreased 10-fold from the lowest to highest growth irradiances. Chlorophyll and phycocyanin-specific efficiencies also decreased but to a lesser extent. Phycoerythrin-specific efficiencies increased ca. 2-fold with increasing irradiances. Photosynthetic capacity (Pm,,x) approximated the in sire rate of photosynthesis (P,) only at growth irradiances which saturated growth rate; at light limiting irradiances, P.,.x increased to 2.9 times Pi. Photoinhibition of photosynthesis was only observed in light-limited cells. The mechanism of photoadaptation which resulted in the observed growth rate vs irradiance (lavs I) response involved regulation of u~.~.H) by changes in phycobilisome size over saturating irradiances and phycobilisome numbers over limiting irradiances. Our results are consistent with previously reported field observations of ~t~,h~ ~, u~,,~,tn and P ...... increasing with depth, and of no photoinhibition of near-surface collected assemblages, suggesting that high irradiances in near-surface waters can support maximal growth rates of Synechococcus. These results raise important questions regarding the interpretation of parameters of P vs 1 measurements from field studies. Our results do not conform to the previously reported hypothesis that a significant percentage of phycoerythrin serves as a non-photosynthetic nitrogen storage compound in these cells.
Stomatal apertures in darkness and subsequent average opening rates in light were measured in Vic... more Stomatal apertures in darkness and subsequent average opening rates in light were measured in Viciafaba leaf discs throughout the nyctoperiods for plants grown on three Light:dark cydes (8:16, 12:12, and 16:8). The time core of opening in darkness depended on the specific light:dark cyde with the maimum aperture always occurring at the time the lights normally went on. The light-induced opening rate was also maximum at the end of the nyctoperiod.
The average opening rate of Vicia faba L. stomata was determined over an initial 20-minute light ... more The average opening rate of Vicia faba L. stomata was determined over an initial 20-minute light period following darkness. Nonsaturating intensities of broad band red and blue light had similar quantum effectiveness for the promotion of opening, whereas broad band green was about 40% and far red about 5% as effective. The opening rates under saturating red, green, and blue light were the same. Net photosynthesis was measured under various intensities of the same red, green, and blue light spectra. Red and blue light were equally efficient in causing photosynthesis, whereas green was 60% as effective. The light compensation points for the three colors were at higher intensities than those which satunrated the opening rate response. These data suggest that only a single pigment system, probably the photosynthetic pigments, is responsible for initiating the light-induced opening response in V.faba stomata.
The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to glob... more The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to global ocean primary production that can be stressed by solar radiation, both in the photosynthetically active (PAR) and ultraviolet (UV) range. We studied the responses of PSII quantum yield (active fluorescence), carbon fixation ((14)C assimilation) and oxygen evolution (membrane inlet mass spectrometry) in Synechococcus WH8102 under moderate UV and PAR. PSII quantum yield decreased during exposure to moderate UV and UV+PAR, with response to the latter being faster (6.4 versus 2.8 min, respectively). Repair processes were also faster when UV+PAR exposure was followed by moderate PAR (1.68 min response time) than when UV was followed by very low PAR (10.5 min response time). For the UV+PAR treatment, the initial decrease in quantum yield was followed by a 50% increase ("rebound") after 7 min exposure, showing an apparent photoprotection induction. While oxygen uptake increased with PAR, it did not change under UV, suggesting that this oxygen-dependent mechanism of photoprotection, which may be acting as an electron sink, is not an important strategy against UV. We used propyl gallate, an antioxidant, to test for plastid terminal oxidase (ptox) or ptox-like enzymes activity, but it caused nonspecific and toxic effects on Synechococcus WH8102.
A new ''0 isotope dilution technique is presented and examples are given of the determination of ... more A new ''0 isotope dilution technique is presented and examples are given of the determination of true gross oxygen evolution (photosynthesis) and oxygen uptake (respiration) in plankton samples from estuarine surface waters and in the seagrass Zostera marina. The technique involves enriching dissolved oxygen with 3602, and measuring changes in isotope enrichment and oxygen concentration with time. It is relatively simple to apply, and less expensive than previously used 180 methods. Oxygen uptake rates of plankton samples incubated under various light conditions ranged from 0.75 to 10 times that in darkness. Gross oxygen evolution rates determined by isotope dilution were from 0 to 80 % higher than gross oxygen evolution rates calculated from parallel light and dark bottle experiments and ranged between 180 and 800 FM O2 (FM chl a)-' h-'. Ratios of gross oxygen uptake to gross oxygen evolution were between 0.12 and 0.67 and depended on both light intensity and sampling time. Occasionally, net oxygen evolution and isotope ddution occurred in darkened bottles, suggesting the existence of a non-photosynthetic process that produces new oxygen. In 2. marina, oxygen uptake at saturating light intensities was 4.7 times the rate in darkness. The data indicate the existence of significant, but variable, light stimulation of oxygen consumption in estuarine waters and higher rates of gross oxygen production than measured by the light and dark bottle technique.
Improved separations of phytoplankton pigments using temperature-controlled high performance liqu... more Improved separations of phytoplankton pigments using temperature-controlled high performance liquid chromatography Laurie Van ~e u k e l e m ' , Alan J. L e w i t u s l .
The effect of nitrogen starvation on photosynthetic pigments and energy coupling was compared in ... more The effect of nitrogen starvation on photosynthetic pigments and energy coupling was compared in Synechococcus sp. (Cyanophyta) strains originating from oceanic (oligotrophic) or coastal (eutrophic) marine environments. A survey indicated that those of oceanic or subtropical origin retained a greater fraction (55 to 98 %) of their major phycobiliprotein during a 24 h nitrogen starvation period compared to coastal strains (30 to 44 %) For 3 strains studied in detail, nitrogen starvation caused a significant (> 85 ':L) loss of phycoerythrin from Synechococcussp. WH8018 after 24 h, but only a minor loss (< 25 %) from Synechococcus sp. WH7803 or WH8103 after 3 d starvation. All 3 strains exhibited reduced gross oxygen evolution dunng the first 24 h of starvation, however, indicating a reduction in energy transfer from phycoerythrin to the electron transport chain. Changes during starvation in the in vivo fluorescence excitation and emission spectra indicated a small degree of uncoupling of phycoerythrin from allophycocyanin in Synechococcus sp. WH7803 and MrH8103 but not Synechococcus sp. WH8018. In neither case could it account for the measured loss in photosynthetic efficiency, however. The unusual nature of phycobiliprotein regulation in oceanic strains may reflect an adaptation to episodic (few days time scale) inputs of limiting nutnents to oligotrophic surface waters, thus providing a mechanism for more rapid rejuvenation.
Diel changes in the photosynthetic-irradiance response of phytoplankton were measured in coastal,... more Diel changes in the photosynthetic-irradiance response of phytoplankton were measured in coastal, neritic and oceanic waters. At each site, maximum daily light-saturated photosynthesis rates were 2 to 3 times higher than rates recorded either at dawn or dusk. Time of day that maximum occurred varied with site and depth. Diel measurements in coastal water indicated that minimum photosynthetic capacity occurred in the middle of the night, that up to one-half of the total diel change occurred at night, and that times of most rapid change occurred around dawn and dusk. Independent measurements of nitrogen nutritional status on the neritic and oceanic assemblages indicated that there was no nitrogen limitation for phytoplankton growth.
Natural water bodies, such as lakes, rivers, and oceans, are important sources of atmospheric met... more Natural water bodies, such as lakes, rivers, and oceans, are important sources of atmospheric methane (CH4). Therefore, quantitative and accurate determination of the dissolved CH4 concentration in water is of great significance for studying CH4 emissions and providing an in-depth understanding of the carbon cycle. Headspace gas chromatography (HGC) is the traditional method for measuring CH4 in water. Despite its long success, it has a lot of problems in use, such as complex pretreatment and a long measurement time, and it is not suitable for the CH4 determination of a large number of samples. In view of these shortcomings, a more convenient and efficient method based on membrane inlet mass spectrometry (MIMS) for quantitative measurements of the dissolved CH4 concentration in water was established. In our study, the standard curves showed that the method had high accuracy, both at low and high CH4 concentrations. After a laboratory test, to evaluate the sensitivity of this method,...
A new ''0 isotope dilution technique is presented and examples are given of the determination of ... more A new ''0 isotope dilution technique is presented and examples are given of the determination of true gross oxygen evolution (photosynthesis) and oxygen uptake (respiration) in plankton samples from estuarine surface waters and in the seagrass Zostera marina. The technique involves enriching dissolved oxygen with 3602, and measuring changes in isotope enrichment and oxygen concentration with time. It is relatively simple to apply, and less expensive than previously used 180 methods. Oxygen uptake rates of plankton samples incubated under various light conditions ranged from 0.75 to 10 times that in darkness. Gross oxygen evolution rates determined by isotope dilution were from 0 to 80 % higher than gross oxygen evolution rates calculated from parallel light and dark bottle experiments and ranged between 180 and 800 FM O2 (FM chl a)-' h-'. Ratios of gross oxygen uptake to gross oxygen evolution were between 0.12 and 0.67 and depended on both light intensity and sampling time. Occasionally, net oxygen evolution and isotope ddution occurred in darkened bottles, suggesting the existence of a non-photosynthetic process that produces new oxygen. In 2. marina, oxygen uptake at saturating light intensities was 4.7 times the rate in darkness. The data indicate the existence of significant, but variable, light stimulation of oxygen consumption in estuarine waters and higher rates of gross oxygen production than measured by the light and dark bottle technique.
Deep-Sea Research Part a-Oceanographic Research Papers, 1987
We investigated the photosynthetic behavior of Synechococcas WH7803 when grown over the irradianc... more We investigated the photosynthetic behavior of Synechococcas WH7803 when grown over the irradiance range of 30-200(I laE m 2 s ~ in nutrient-replete, continuous light, preadapted batch cultures. For each of 8 growth irradiances investigated, we found a unique photosynthesis vs irradiance (P vs 1) relationship. Cell-and carbon-specific photosynthetic light harvesting efficiencies (cq,.,.n) and ct¢c)) decreased 10-fold from the lowest to highest growth irradiances. Chlorophyll and phycocyanin-specific efficiencies also decreased but to a lesser extent. Phycoerythrin-specific efficiencies increased ca. 2-fold with increasing irradiances. Photosynthetic capacity (Pm,,x) approximated the in sire rate of photosynthesis (P,) only at growth irradiances which saturated growth rate; at light limiting irradiances, P.,.x increased to 2.9 times Pi. Photoinhibition of photosynthesis was only observed in light-limited cells. The mechanism of photoadaptation which resulted in the observed growth rate vs irradiance (lavs I) response involved regulation of u~.~.H) by changes in phycobilisome size over saturating irradiances and phycobilisome numbers over limiting irradiances. Our results are consistent with previously reported field observations of ~t~,h~ ~, u~,,~,tn and P ...... increasing with depth, and of no photoinhibition of near-surface collected assemblages, suggesting that high irradiances in near-surface waters can support maximal growth rates of Synechococcus. These results raise important questions regarding the interpretation of parameters of P vs 1 measurements from field studies. Our results do not conform to the previously reported hypothesis that a significant percentage of phycoerythrin serves as a non-photosynthetic nitrogen storage compound in these cells.
Stomatal apertures in darkness and subsequent average opening rates in light were measured in Vic... more Stomatal apertures in darkness and subsequent average opening rates in light were measured in Viciafaba leaf discs throughout the nyctoperiods for plants grown on three Light:dark cydes (8:16, 12:12, and 16:8). The time core of opening in darkness depended on the specific light:dark cyde with the maimum aperture always occurring at the time the lights normally went on. The light-induced opening rate was also maximum at the end of the nyctoperiod.
The average opening rate of Vicia faba L. stomata was determined over an initial 20-minute light ... more The average opening rate of Vicia faba L. stomata was determined over an initial 20-minute light period following darkness. Nonsaturating intensities of broad band red and blue light had similar quantum effectiveness for the promotion of opening, whereas broad band green was about 40% and far red about 5% as effective. The opening rates under saturating red, green, and blue light were the same. Net photosynthesis was measured under various intensities of the same red, green, and blue light spectra. Red and blue light were equally efficient in causing photosynthesis, whereas green was 60% as effective. The light compensation points for the three colors were at higher intensities than those which satunrated the opening rate response. These data suggest that only a single pigment system, probably the photosynthetic pigments, is responsible for initiating the light-induced opening response in V.faba stomata.
The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to glob... more The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to global ocean primary production that can be stressed by solar radiation, both in the photosynthetically active (PAR) and ultraviolet (UV) range. We studied the responses of PSII quantum yield (active fluorescence), carbon fixation ((14)C assimilation) and oxygen evolution (membrane inlet mass spectrometry) in Synechococcus WH8102 under moderate UV and PAR. PSII quantum yield decreased during exposure to moderate UV and UV+PAR, with response to the latter being faster (6.4 versus 2.8 min, respectively). Repair processes were also faster when UV+PAR exposure was followed by moderate PAR (1.68 min response time) than when UV was followed by very low PAR (10.5 min response time). For the UV+PAR treatment, the initial decrease in quantum yield was followed by a 50% increase (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;rebound&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) after 7 min exposure, showing an apparent photoprotection induction. While oxygen uptake increased with PAR, it did not change under UV, suggesting that this oxygen-dependent mechanism of photoprotection, which may be acting as an electron sink, is not an important strategy against UV. We used propyl gallate, an antioxidant, to test for plastid terminal oxidase (ptox) or ptox-like enzymes activity, but it caused nonspecific and toxic effects on Synechococcus WH8102.
A new ''0 isotope dilution technique is presented and examples are given of the determination of ... more A new ''0 isotope dilution technique is presented and examples are given of the determination of true gross oxygen evolution (photosynthesis) and oxygen uptake (respiration) in plankton samples from estuarine surface waters and in the seagrass Zostera marina. The technique involves enriching dissolved oxygen with 3602, and measuring changes in isotope enrichment and oxygen concentration with time. It is relatively simple to apply, and less expensive than previously used 180 methods. Oxygen uptake rates of plankton samples incubated under various light conditions ranged from 0.75 to 10 times that in darkness. Gross oxygen evolution rates determined by isotope dilution were from 0 to 80 % higher than gross oxygen evolution rates calculated from parallel light and dark bottle experiments and ranged between 180 and 800 FM O2 (FM chl a)-' h-'. Ratios of gross oxygen uptake to gross oxygen evolution were between 0.12 and 0.67 and depended on both light intensity and sampling time. Occasionally, net oxygen evolution and isotope ddution occurred in darkened bottles, suggesting the existence of a non-photosynthetic process that produces new oxygen. In 2. marina, oxygen uptake at saturating light intensities was 4.7 times the rate in darkness. The data indicate the existence of significant, but variable, light stimulation of oxygen consumption in estuarine waters and higher rates of gross oxygen production than measured by the light and dark bottle technique.
Improved separations of phytoplankton pigments using temperature-controlled high performance liqu... more Improved separations of phytoplankton pigments using temperature-controlled high performance liquid chromatography Laurie Van ~e u k e l e m ' , Alan J. L e w i t u s l .
The effect of nitrogen starvation on photosynthetic pigments and energy coupling was compared in ... more The effect of nitrogen starvation on photosynthetic pigments and energy coupling was compared in Synechococcus sp. (Cyanophyta) strains originating from oceanic (oligotrophic) or coastal (eutrophic) marine environments. A survey indicated that those of oceanic or subtropical origin retained a greater fraction (55 to 98 %) of their major phycobiliprotein during a 24 h nitrogen starvation period compared to coastal strains (30 to 44 %) For 3 strains studied in detail, nitrogen starvation caused a significant (> 85 ':L) loss of phycoerythrin from Synechococcussp. WH8018 after 24 h, but only a minor loss (< 25 %) from Synechococcus sp. WH7803 or WH8103 after 3 d starvation. All 3 strains exhibited reduced gross oxygen evolution dunng the first 24 h of starvation, however, indicating a reduction in energy transfer from phycoerythrin to the electron transport chain. Changes during starvation in the in vivo fluorescence excitation and emission spectra indicated a small degree of uncoupling of phycoerythrin from allophycocyanin in Synechococcus sp. WH7803 and MrH8103 but not Synechococcus sp. WH8018. In neither case could it account for the measured loss in photosynthetic efficiency, however. The unusual nature of phycobiliprotein regulation in oceanic strains may reflect an adaptation to episodic (few days time scale) inputs of limiting nutnents to oligotrophic surface waters, thus providing a mechanism for more rapid rejuvenation.
Diel changes in the photosynthetic-irradiance response of phytoplankton were measured in coastal,... more Diel changes in the photosynthetic-irradiance response of phytoplankton were measured in coastal, neritic and oceanic waters. At each site, maximum daily light-saturated photosynthesis rates were 2 to 3 times higher than rates recorded either at dawn or dusk. Time of day that maximum occurred varied with site and depth. Diel measurements in coastal water indicated that minimum photosynthetic capacity occurred in the middle of the night, that up to one-half of the total diel change occurred at night, and that times of most rapid change occurred around dawn and dusk. Independent measurements of nitrogen nutritional status on the neritic and oceanic assemblages indicated that there was no nitrogen limitation for phytoplankton growth.
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