The importance of extracellular carbohydrate production by marine epipelic diatoms
Underwood, G.J.C.; Paterson, D.M. (2003). The importance of extracellular carbohydrate production by marine epipelic diatoms. Adv. Bot. Res. 40: 183-240
In: Advances in Botanical Research. Academic Press: London; New York. ISSN 0065-2296; e-ISSN 2162-5948
Soft-sediment habitats in intertidal and shallow subtidal marine ecosystems frequently support extensive populations of benthic microalgae (microphytobenthos). These algal assemblages are dominated by species of motile benthic diatoms and form biofilms, a matrix of cells, sediments and extracellular polymeric substances (BPS), that create a complex microhabitat and act to stabilise sediments. Diatom BPS consists of a relatively undefined complex mixture of proteins, proteoglycans and carbohydrates. This complexity causes problems in extracting and analysing BPS and in the intercomparison of studies. This chapter reviews our current knowledge on the production rates, patterns and composition of benthic diatom BPS in culture and field studies. Production patterns are dynamic, changing with cell growth phase, photosynthesis and irradiance, nutrient conditions, and are also linked to endogenous cell rhythms. Meta-analysis of published monosaccharide composition data identified at least four major types of BPS produced by benthic diatoms, with varying patterns of production and composition. It is clear that more detailed research on the structural and physical properties of BPS are needed to understand its role in the environment. The natural occurrence of BPS is closely linked to diatom biomass, a pattern consistent over both macro (km) and micro (JLm) scales. BPS is lost from sediments by various routes; solubilisation and removal by overlying water, bacterial degradation and consumption by deposit-feeding invertebrates. Work is needed to quantify these pathways and clarify the importance of BPS in coastal carbon cycles. Diatom BPS is a widely cited mechanism for increasing sediment stability and stabilisation by biofilms is well described. However, data are not consistent and developments in our knowledge of the structure and function of BPS are needed to explain how BPS binds and interacts within the sediment-biofilm matrix and affects the rheology of sediment.
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