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Optical properties of corals distort variable chlorophyll fluorescence measurements

TitleOptical properties of corals distort variable chlorophyll fluorescence measurements
Publication TypeJournal Article
Year of Publication2019
AuthorsWangpraseurt D., Lichtenberg M., Jacques S.L, Larkum A.WD, Kuhl M.
JournalPlant Physiology
Date Published2019/04
Type of ArticleArticle
ISBN Number0032-0889
Accession NumberWOS:000462993100037
Keywordselectron-transport rates; elevated-temperature; fluorometer; light-absorption; microenvironment; pam; photosynthesis; photosystem-ii; Plant Sciences; reabsorption; scattering; zooxanthellae

Pulse-amplitude-modulated (PAM) fluorimetry is widely used in photobiological studies of corals, as it rapidly provides numerous photosynthetic parameters to assess coral ecophysiology. Coral optics studies have revealed the presence of light gradients in corals, which are strongly affected by light scattering in coral tissue and skeleton. We investigated whether coral optics affects variable chlorophyll (Chl) fluorescence measurements and derived photosynthetic parameters by developing planar hydrogel slabs with immobilized microalgae and with bulk optical properties similar to those of different types of corals. Our results show that PAM-based measurements of photosynthetic parameters differed substantially between hydrogels with different degrees of light scattering but identical microalgal density, yielding deviations in apparent maximal electron transport rates by a factor of 2. Furthermore, system settings such as the measuring light intensity affected F-o, F-m, and F-v/F-m in hydrogels with identical light absorption but different degrees of light scattering. Likewise, differences in microalgal density affected variable Chl fluorescence parameters, where higher algal densities led to greater F-v/F-m values and relative electron transport rates. These results have important implications for the use of variable Chl fluorimetry in ecophysiological studies of coral stress and photosynthesis, as well as other optically dense systems such as plant tissue and biofilms.

Short TitlePlant Physiol.
Student Publication: