A laboratory study on O2 dynamics and photosynthesis in ice algal communities: quantification by microsensors, O2 exchange rates, 14C incubations and a PAM fluorometer: Quantification by microsensors, O2 exchange rates, 14C incubations and a PAM fluorometer

Ronnie N. Glud; Søren Rysgaard; Michael Kühl

doi:10.3354/ame027301

A laboratory study on O₂ dynamics and photosynthesis in ice algal communities: quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer: Quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer

Ronnie N. Glud^*, Søren Rysgaard, Michael Kühl

^*Corresponding author for this work

61 Citations (Scopus)

Abstract

The present study compared O₂ exchange measurements, fluorometry and ¹⁴c incubations for measuring productivity of sea-ice algae. It is demonstrated that brine leaking out of ice during freezing conditions is supersaturated with respect to O₂, while the melting water released during thawing is undersaturated with O₂. This results in a highly variable O₂ concentration at the ice-water interface during expanding or shrinking of sea ice. Consequently, great care should be taken when inferring biological activity from O₂ exchange rates, whether they are obtained via microprofiles, bulk incubations or direct measurement of O₂ concentrations in water below sea ice. Accounting for the O₂ dynamics related to changes in sea-ice structure, the photosynthetic activity of a mixed ice algal culture, as measured by net O₂ exchange rates and ¹⁴C incubation, co-varied as a function of biomass and irradiance. The ratio between the net O₂ efflux and the gross C fixation rate (the photosynthetic quotient) was similar for frozen and non-frozen ice algal communities and averaged 1.43 ± 0.48. Quantification of the relative electron transport rate (ETR) from photosystem II (PSII) and the minimum fluorescence yield (F₀) by a pulse-amplitude-modulated (PAM) fluorometer offers a fast, simple and non-invasive approach for estimating activity and biomass of ice algal communities. The relative ETR measurements correlated with the other 2 measures for primary production. However, the correlation was non-linear, leading to a poor resolution of the fluorometer approach at higher photosynthetic activities. A similar observation was made for the correlation between measurements and the concentration of chlorophyll a.

Original language	English
Journal	Aquatic Microbial Ecology
Volume	27
Issue number	3
Pages (from-to)	301-311
Number of pages	11
ISSN	0948-3055
DOIs	https://doi.org/10.3354/ame027301
Publication status	Published - 16 Apr 2002

Keywords

Fluorometer
Microelectrodes
Oxygen
Primary production
Pulse amplitude modulated fluorometry
Sea-ice algae

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Glud, R. N., Rysgaard, S., & Kühl, M. (2002). A laboratory study on O₂ dynamics and photosynthesis in ice algal communities: quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer: Quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer. Aquatic Microbial Ecology, 27(3), 301-311. https://doi.org/10.3354/ame027301

A laboratory study on O₂ dynamics and photosynthesis in ice algal communities: quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer : Quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer. / Glud, Ronnie N.; Rysgaard, Søren; Kühl, Michael.

In: Aquatic Microbial Ecology, Vol. 27, No. 3, 16.04.2002, p. 301-311.

Research output: Contribution to journal › Journal article › Research › peer-review

Glud, RN, Rysgaard, S & Kühl, M 2002, 'A laboratory study on O₂ dynamics and photosynthesis in ice algal communities: quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer: Quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer', Aquatic Microbial Ecology, vol. 27, no. 3, pp. 301-311. https://doi.org/10.3354/ame027301

Glud, Ronnie N. ; Rysgaard, Søren ; Kühl, Michael. / A laboratory study on O₂ dynamics and photosynthesis in ice algal communities: quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer : Quantification by microsensors, O₂ exchange rates, ¹⁴C incubations and a PAM fluorometer. In: Aquatic Microbial Ecology. 2002 ; Vol. 27, No. 3. pp. 301-311.

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abstract = "The present study compared O2 exchange measurements, fluorometry and 14c incubations for measuring productivity of sea-ice algae. It is demonstrated that brine leaking out of ice during freezing conditions is supersaturated with respect to O2, while the melting water released during thawing is undersaturated with O2. This results in a highly variable O2 concentration at the ice-water interface during expanding or shrinking of sea ice. Consequently, great care should be taken when inferring biological activity from O2 exchange rates, whether they are obtained via microprofiles, bulk incubations or direct measurement of O2 concentrations in water below sea ice. Accounting for the O2 dynamics related to changes in sea-ice structure, the photosynthetic activity of a mixed ice algal culture, as measured by net O2 exchange rates and 14C incubation, co-varied as a function of biomass and irradiance. The ratio between the net O2 efflux and the gross C fixation rate (the photosynthetic quotient) was similar for frozen and non-frozen ice algal communities and averaged 1.43 ± 0.48. Quantification of the relative electron transport rate (ETR) from photosystem II (PSII) and the minimum fluorescence yield (F0) by a pulse-amplitude-modulated (PAM) fluorometer offers a fast, simple and non-invasive approach for estimating activity and biomass of ice algal communities. The relative ETR measurements correlated with the other 2 measures for primary production. However, the correlation was non-linear, leading to a poor resolution of the fluorometer approach at higher photosynthetic activities. A similar observation was made for the correlation between measurements and the concentration of chlorophyll a.",

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AB - The present study compared O2 exchange measurements, fluorometry and 14c incubations for measuring productivity of sea-ice algae. It is demonstrated that brine leaking out of ice during freezing conditions is supersaturated with respect to O2, while the melting water released during thawing is undersaturated with O2. This results in a highly variable O2 concentration at the ice-water interface during expanding or shrinking of sea ice. Consequently, great care should be taken when inferring biological activity from O2 exchange rates, whether they are obtained via microprofiles, bulk incubations or direct measurement of O2 concentrations in water below sea ice. Accounting for the O2 dynamics related to changes in sea-ice structure, the photosynthetic activity of a mixed ice algal culture, as measured by net O2 exchange rates and 14C incubation, co-varied as a function of biomass and irradiance. The ratio between the net O2 efflux and the gross C fixation rate (the photosynthetic quotient) was similar for frozen and non-frozen ice algal communities and averaged 1.43 ± 0.48. Quantification of the relative electron transport rate (ETR) from photosystem II (PSII) and the minimum fluorescence yield (F0) by a pulse-amplitude-modulated (PAM) fluorometer offers a fast, simple and non-invasive approach for estimating activity and biomass of ice algal communities. The relative ETR measurements correlated with the other 2 measures for primary production. However, the correlation was non-linear, leading to a poor resolution of the fluorometer approach at higher photosynthetic activities. A similar observation was made for the correlation between measurements and the concentration of chlorophyll a.

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