Sequential resuspension of biofilm components (viruses, prokaryotes and protists) as measured by erodimetry experiments in the Brouage mudflat (French Atlantic coast)
|Author(s)||Dupuy Christine1, Mallet Clarisse2, Guizien Katell3, Montanie Helene1, Breret Martine1, Mornet Francoise4, Fontaine Camille1, Nerot Caroline1, 5, Orvain Francis6|
|Affiliation(s)||1 : Univ La Rochelle, Littoral Environm & Soc LIENSs, UMR 7266, CNRS ULR, F-17000 La Rochelle, France.
2 : Univ Clermont Ferrand, CNRS, UMR 6023, Lab Microorganismes Genome & Environm, F-63177 Aubiere, France.
3 : CNRS UPMC, Observ Oceanol Banyuls Sur Mer, UMR 8222, Lab Ecogeochim Environm Benth, F-66650 Banyuls Sur Mer, France.
4 : IFREMER, Stn La Rochelle, Lab Ressources Halieut La Rochelle, F-17137 Lhoumeau, France.
5 : Inst Univ Europeen Mer, UMR 6539, LEMAR, F-29280 Plouzane, France.
6 : Univ Caen Basse Normandie, BioMEA FRE3484, CNRS, F-14032 Caen, France.
|Source||Journal Of Sea Research (1385-1101) (Elsevier Science Bv), 2014-09 , Vol. 92 , P. 56-65|
|WOS© Times Cited||15|
|Keyword(s)||Viruses, Microorganisms, Resuspension, Benthic-pelagic coupling, Spatial distribution, Mudflat|
|Abstract||Resuspension thresholds in terms of friction velocity were experimentally quantified for the prokaryotes, protists and for the first time, viruses of intertidal mudflat biofilms. Differences in resuspension thresholds could be related to the type, behaviour and size of microorganisms and their association with particles. Free microorganisms (viruses, bacteria and some nanoflagellates) were resuspended by weak flow at friction velocities lower than 2 cm s- 1. Chlorophyll a, some nanoflagellates and attached bacteria were resuspended together with the bed’s muddy sediment, which required friction velocities larger than 3 cm s- 1. Diatoms smaller than 60 μm were resuspended at velocities between 3 and 5 cm s- 1, while those larger than 60 μm were resuspended at higher friction velocities (5.5 to 6.5 cm s- 1). The thresholds of resuspension also depended on the micro-scale position of microorganisms in the sediment (horizontal and vertical distribution). In the field, the vertical distribution of chlorophyll a (a proxy of microphytobenthos) was skewed, with a maximum in the first 2 mm of sediment. Along the neap-spring tidal cycle, chlorophyll a revealed an increase in MPB biomass in the first 2 mm of the sediment, in relation to light increases with exposure durations. The horizontal distribution of chlorophyll a could be inferred from erosion experiments. During the initial phase of biofilm growth, the distribution of chlorophyll a seemed horizontally homogeneous, and was uniformly eroded at the beginning of the increase in chlorophyll a. From these results, we can make a hypothesis: in the subsequent phase of biofilm growth until the maximum of emersion duration, the eroded quantity of chlorophyll a was larger than expected based from chlorophyll a vertical distribution, suggesting that biofilm horizontal distribution became patchy and enriched chlorophyll a were preferentially eroded. When emersion duration and biofilm growth decreased, the trend was reversed, and eroded quantity of chlorophyll a was lower than expected from chlorophyll a vertical distribution, suggesting that areas with low chlorophyll a were preferentially eroded. Such erosion patterns when biofilm growth decreased probably resulted from the bulldozing activity of a surficial sediment bioturbator, the gastropod Peringia ulvae. Our study did not directly prove this horizontal distribution but it should be further discussed. This distribution need to be studied to acquire real evidence of patchy distributions.|