Photophysiological variability of microphytobenthic diatoms after growth in different types of culture conditions

Abstract

R.M. Forster and V. Martin-Jézéquel. 2005. Photophysiological variability of microphytobenthic diatoms after growth in different types of culture conditions. Phycologia 44: 393–402.

Microphytobenthic diatoms have great ecological importance in estuarine and coastal marine ecosystems, yet many aspects of their physiology have not been investigated under controlled conditions. This work describes patterns in growth rates and photosynthesis in different types of culture for several species of benthic diatom. Cells were grown as epipelic biofilms both in batch culture vessels and in a continuous culture system, and differences in growth and photosynthetic physiology were measured using optical techniques. Consistent differences were observed in the maximum photochemical efficiency of PS II, F_v/F_m between species of diatoms, with highest values recorded early in the development of a culture. The maximum biomass produced also varied greatly between species, with the densest biofilms being formed by Amphora coffeaeformis. Batch cultures of benthic diatoms showed only small changes in F_v/F_m, but large decreases in the maximum rate of photosynthetic electron transport during the first week of culture development because conditions within the biofilm became unfavourable. A flow-through culture chamber was developed in order to increase the supply of nutrients to the biofilm and prevent the build-up of oxygen. In this system, high growth rates and a high maximum rate of photosynthesis was observed for periods of up to 1 wk. The flow chamber system could therefore be used for producing suitable material for comparative photophysiological experiments.

ACKNOWLEDGMENTS

This work was assisted by a CNRS ‘Poste Rouge’ Visiting Scientist position from the University of Brest, and an NWO Van Gogh award for travel costs. We thank V. Creach for support with cultures and identification, and J.C. Kromkamp for comments on the manuscript. This is NIOO publication number 3483.