title: Effect of biofilm on fluorescence measurements derived from fast repetition rate fluorometers.
abstract: This study evaluates, for the first time, the influence of biofilms on single and double optical window (SOW and DOW, respectively) fast repetition rate fluorometer (FRRF) measurements of microalgal photosystem-II initial fluorescence (F0), maximum fluorescence (Fm), variable fluorescence (Fv = Fm - F0), quantum yield (Fv/Fm) and functional absorption cross section (σPSII)]. Biofilms with chlorophyll > 0.1 μg cm(-2) and > 0.3 μgcm(-2) on SOW and DOW, respectively, produced a substantial increase in fluorescence. However, the relative magnitude of biofouling effects depended on sample chlorophyll concentrations, being more critical at concentrations < 1 mg m(-3). In DOW-FRRF, biofilms affected F0 (increased) and Fv/Fm (decreased) but not Fv and σPSII, whereas in SOW-FRRF, biofilms increased fluorescence and showed a variable effect on Fv/Fm and σPSII, because only biofilms on SOW attained actual Fm. As a result, the biofilm effect was substantial on SOW-FRRF measurements. On the other hand, the neutral-density filters (representing non-chlorophyll containing biofilms) with different transmission levels reduced the fluorescence signal. Correction procedures for the above photosystem-II parameters are proposed here.
authors.affiliation: a Biofouling & Bioinvasion Division , CSIR - National Institute of Oceanography , Dona Paula , India.
authors.forename: Jagadish S
authors.initials: JS
authors.lastname: Patil
authors.forename: Toshiro
authors.initials: T
authors.lastname: Saino
mesh_terms: D000818:Animals; D018441:Biofilms; D002734:Chlorophyll / Q000737:chemistry*; D005260:Female; D005453:Fluorescence; D005470:Fluorometry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D013552:Swine
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll
keywords: biofilms; chlorophyll; fast repetition rate fluorometer; optical windows; transmission