G. Becker et al., USE OF A MICROSCOPE PHOTOMETER TO ANALYZE IN-VIVO FLUORESCENCE INTENSITY OF EPILITHIC MICROALGAE GROWN ON ARTIFICIAL SUBSTRATA, Applied and environmental microbiology, 63(4), 1997, pp. 1318-1325
An epifluorescence microscope photometer was used to develop a new in
vivo fluorimetric method for analyzing fluorescence intensities of epi
lithic microalgae grown on clay tiles in the field, This enabled a non
destructive, direct quantification of algal biomass on the substratum
surface, Measurements of a chlorophyll a standard in ethanol (90%) wit
h our fluorimetric method (exitation at 546 nm; emission, >590 nm) cor
related well with those from conventional spectrofluorimetric and spec
trophotometric methods, Biofilms were analyzed with the microscope pho
tometer by measuring the in vivo fluorescence intensity of 70 spots di
stributed randomly over the tile surface, They were then analyzed by t
he two in vitro methods after photopigment extraction, Chlorophyll a c
ontent and in vivo fluorescence intensity correlated well, The regress
ion curves were linear up to 6 mu g cm(-2) but were quadratic or hyper
bolic at higher concentrations of up to 28 mu g cm(-2) The degree of s
catter among individual measurements was higher in biofilms than chlor
ophyll a standards, This in vivo analysis is well suited to ecological
experiments and has the advantage of measuring on an extremely small
scale, which enables direct analysis of the microdistribution of epili
thic microalgae in live biofilms, We demonstrated this by comparing fl
uorescence intensities of the grazing tracks of the snail Ancylus flav
iatilis with those of ungrazed areas, Our in vivo analysis is also uni
que in enabling biofilms on artificial substrata to be removed, analyz
ed, and then returned intact in field or laboratory experiments.