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

Abstract

Microphytobenthic diatoms have great ecological importance in estuarine and coastal marine ecosystenis, 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,town 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 technique. 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 [KEYWORDS: CHLOROPHYLL-A FLUORESCENCE ; BENTHIC DIATOM ; INDUCTION KINETICS ; TERM VARIATIONS ; QUANTUM YIELD ; WADDEN-SEA ; DYNAMICS ; BIOMASS ; PHYTOPLANKTON ; TEMPERATURE]