Does the size of the microphytobenthic biofilm on intertidal mudflats depend on the available photosynthetic biomass?

Methodology of light response curves: application of chlorophyll fluorescence to microphytobenthic biofilms

“…The biomass (or size) of experimental biofilms, expressed in mg chl a m −2 , is assessed a priori from the quantity of chl a introduced in the tube and the surface area of the bottom of the tube. In the present experiment, the size of biofilms was set at about 35 mg chl a m −2 to reproduce in situ conditions corresponding to the date and site of sampling (Herlory et al 2005 ). To reach this value, the concentration of the prepared microalgal suspension (see above) was adjusted to 930 μg chl a L −1 , and 5 mL of this suspension was added to 13-mm diameter tubes, prior to settling of cells.…”

“…Microphytobenthos assemblages are frequently dominated by epipelic (i.e., free and mobile) diatoms (Round 1971 ) that migrate to the sediment surface during diurnal emersion periods forming transient biofilms (Gouleau 1976 ; Paterson 1986 ; Paterson et al 1986 ; Paterson 1995 ). This biogenic structure, recognized as the primary production system in intertidal mudflats (Guarini et al 2000 ) usually disappears at the end of emersion due to reburying of diatoms or to their resuspension with the incoming tide (Consalvey et al 2004b ; Easley et al 2005 ; Herlory et al 2005 ). Modulated fluorescence is a non-destructive technique which not only preserves the structure of the biofilm but also enables the assessment of the rapid response to light of microalgae induced by the high-frequency fluctuation of natural irradiance.…”

The Vertical Migratory Rhythm of Intertidal Microphytobenthos in Sediment Depends on the Light Photoperiod, Intensity, and Spectrum: Evidence for a Positive Effect of Blue Wavelengths

“…The use of coupled Chl a fluorescence with imaging techniques has proven to be of paramount interest to monitor the temporal changes in MPB biomass, in particular with an Imaging-PAM fluorometer (Du et al, 2010;Vieira et al, 2013;Blommaert et al, 2018). Imaging of Chl a fluorescence allows assessment of the dynamics of the "photosynthetically active (or productive) biomass" (PAB) at the surface of sediment (Herlory et al, 2005;Guarini et al, 2008). In the present study, we have used Imaging-PAM fluorimetry to assess changes in PAB in a continuous mode with measurements every 900 s over several days with less than 15-min stop for watering and mixing the sediment tray every 24 h. The main advantage of imaging-fluorimetry compared to other fluorimeters (for instance, the Water-PAM fiber version or the Diving-PAM) is its non-invasive feature; there is no contact with the sediment surface (Vieira et al, 2013).…”

“…The conceptualization of MPB migration dynamics (Guarini et al, 2008) opened a path to improvements in coupled biological-physical modeling attempts of mudflat primary production (Guarini et al, 2006). In this framework, the quantification of the MPB photosynthetically active biomass (PAB) at the surface of sediment (Herlory et al, 2005) and the precise measurement of its spatial and temporal dynamics (Consalvey et al, 2004), as well as its photosynthetic productivity (Kwon et al, 2012;Cartaxana et al, 2016a;Haro et al, 2019), have received major interest. It is generally accepted that rhythmic MPB migration is first governed by the tidal and diurnal cycles, which, together, control the light availability at the surface of sediment.…”

A new tool to detect high viscous exopolymers from microalgae

“…In these photosynthetic structures, whose average thickness is several micrometers, the microalgae are arranged into parallel layers surrounded by extracellular polymeric substances [21].…”