Ecophysiology of photosynthesis of Vaucheria sp. mats in a Svalbard tidal flat

Abstract

The photosynthetic performance of a Vaucheria sp. community in the Adventfjorden tidal flats near Longyearbyen, Svalbard, the Arctic was evaluated in a series of in situ and ex situ measurements based on variable chlorophyll fluorescence and gasometric approaches. The in situ measurement did not indicate any possible drivers from the selected environmental parameters (temperature, PAR, UVR, emersion period duration) of photosynthetic activity. Two ecotypes, spikes or loose filaments, observed in the field were related to emersion and immersion periods during the tidal cycle. Ex situ long-term monitoring identified PAR as the main controlling factor of photosynthesis. No limitation of photosynthetic activity due to temperatures or light was detected. The detailed ex situ photosynthesis measurements of Vaucheria sp. samples pre-acclimated to different irradiances did not reveal any decrease of photosynthesis in high light. Irradiance affected only the photosynthesis rate, but not the photosynthesis efficiency. The Vaucheria sp. was acclimated to the prevailing low-light conditions but was able to tolerate high-light conditions on sunny days of the late Artic summer.