The Application of Variable Chlorophyll Fluorescenceto Microphytobenthic Biofilms

International audienceCommunity assemblages of diatoms, green algae andcyanobacteria comprise the microphytobenthos (MPB),which inhabit benthic sediment ecosystems (Admiraal1984; Underwood and Kromkamp 1999; Consalvey et al. 2004). Particular attention has been paid to theanalysis of intertidal soft sediment systems, e.g. cohesivemudflat and sandy substrata typical of estuarine habitats.Variable chlorophyll fluorescence has been applied tothese systems since the 1990s, in an attempt to investigatethe primary productivity and photophysiology ofthe integrated biofilms, when viewed as a “black boxsystem”, and also at the species level (Sections 5, 6 and7). These transient (i.e. temporary) biofilms are not confinedto such soft sediment habitats however, and morerecently application of fluorescence methodologies hasbeen applied to biofilms inhabiting rocky shores andstromatolite systems (Kromkamp et al. 2007; Perkinset al. 2007). However the large majority of publishedwork has centred upon benthic soft-sediment biofilms,due to their important ecosystem functions of carbonflow and sediment stability (Underwood and Kromkamp1999). In the former their high magnitude of productivityfuels carbon flow through invertebrate and bacterial foodwebs to support important trophic levels of anthropogenicallyexploited taxa, including coastal fish and shellfisheries and coastal avifauna. In the case of sedimentstability, biogenic exopolymers, usually referred to asextracellular polymeric substances (EPS), produced bythe MPB in part to facilitate mobility, may contributesignificantly to sediment stability, hence increasing thesediment resistance to hydrodynamic stresses and thusresistance to coastal erosion (e.g. Underwood andKromkamp 1999 and citations there-in). Finally, thephotosynthetic production of oxygen can be regarded asan important ecosystem function