Received 15 September 1996. Accepted 15 February 1997.
Article first published online: 28 JUN 2008
Journal of Phycology
Volume 33, Issue 3, pages 542–553, June 1997
How to Cite
Serôdio, J., Marques da Silva, J. and Catarino, F. (1997), NONDESTRUCTIVE TRACING OF MIGRATORY RHYTHMS OF INTERTIDAL BENTHIC MICROALGAE USING IN VIVO CHLOROPHYLL A FLUORESCENCE. Journal of Phycology, 33: 542–553. doi: 10.1111/j.0022-3646.1997.00542.x
Abbreviations: a*(z), Optical absorption cross section normalized to Chl a of cells at depth z (m2· g Chl a−1); c(z). sediment Chl a content at depth z (g Chl a· m−3); Chl, chlorophyll; d, distance between the PAM fiberoptics and the sample surface (mm); E0 (d, z), scalar exciting spectral irradiance at depth z, at a distance d + z from the fiberoptics (W · m−2· nm−1); Ed(d, z), Ed, downwelling exciting spectral irradbance at depth z, at a distance d + z from the fiberoptics and at the fiberoptics level (W·m−2· nm−1); F(d), depth-integrated fluorescence intensity emitted by the ensemble of cells present in the sediment, which is detected by the fiberoptics at a distance d from the sediment surface (mV); F(d, z), fluorescence intensity emitted by cells present in a unit volume at depth z, which is detected at the fiberoptics level at a distance d + z from the sediment surface (mV); Fl (d, z), fluorescent radiance flux emitted by the cells present in a unit volume of sediment at depth z, at a distance d + z from the fiberoptics (W·m−3· nm−l); Fo, Fv, FM, dark-level (minimum), variable, and maximum values attainable by Chl a fluorescence intensity, here considered to be measured 1 mm from the sample surface (mV); Fu,(d, z), upwelling fluorescent spectral irradiance emitted at depth z, at a distance d + z from the fiberoptics (W·m−2·nm−1); φF(z), quantum yield of Chl a fluorescence at depth z (quanta emittedquanta absorbed−1); φFo, φFM, dark-level and maximum quantum yield of Chl a fluorescence (quanta emittedquanta absorbed−1); G, factor representing the conversion between detected fluorescent irradiance and fluorometer output (mV·W−1·m2·nm); kair, ksed, attenuation coefticients of exciting light and emitted fluorescence in the air and in the sediment (mm−1); LHCII, light-harvesting complex of phutosystem II; μ(z), average cosine (mean cosine of the average path direction of incident photons); nPSII(z), PSII concentration at depth z (PSII · m−3); PSII, photosystem II; Q(z), fractional reduction of emitted fluorescence due to intracellular reabsorption at depth z, rex, rem, fractional reflexion losses of exciting light and emitted fluorescence at the sediment-air (or sediment-water) interface; R(z), irradiance reflectance (ratio of upward to downward irradiance) at depth z; σPSII (z), functional absorption cross section of energy-absorbing pigments in LHCII at depth z (m2ΨII−1); z, depth below sediment surface (mm).
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Key index words: benthic microalgae;
- chlorophyll a fluorescence;
- Euglena granulata;
- intertidal areas;
- Phaeodactylum tricornutum;
- Spirulina maxima;
- vertical migration
In vivo chlorophyll (Chl) a fluorescence was measured in undisturbed intertidal sediments with the purpose of tracing the vertical migratory rhythms of benthic microalgae. A pulse amplitude fluorometer, an instrument which does not require physical contact with the sample, was used, thus allowing successive measurements to be taken on the same sample without causing any type of disturbance to the sediment structure. The basis of the method is the possibility to detect changes in the Chl a concentration near the sediment surface caused by the vertical movement of the microalgae. This requires the verification of two conditions: the possibility to follow changes in the sediment Chl a content from fluorescence intensity, and a sediment photic depth smaller than the vertical distances covered by the moving microalgae. Both conditions were experimentally verified in intertidal muddy sediments of the Tagus estuary, Portugal. In vivo fluorescence was shown to vary linearly with the sediment Chl a content, and the sediment photic depth was estimated to reach 0.27 mm, a value clearly smaller than the reported depths for microalgal migrations. Sediment samples kept under in situ conditions exhibited large hourly Variations (over 400%) in the Chl a fluorescence intensity, which were closely synchronized with the daytime periods of emersion. The rhythmic fluctuations in Chl a fluorescence were confirmed further to represent microalgal migration by (1) its endogenous nature (fluorescence continued to follow diurnal and tidal cycles after removal of environmental stimuli), (2) its dependence on the vertical distribution of the microalgal population within the sediment (vertically homogenized samples failed to display fluorescence variations), and (3) the lack of significant temperature and light effects on the fluorescence emission under in situ conditions (tested in three species representative of the main groups found in the studied microphytobenthic communities—the diatom Phaeodactylum tricornutum (Böhlin), the cyanobacterium Spirulina maxima (Setch. et Gard.), and the euglenophyte Euglena granulata (Klebs) Lemm.). The results obtained indicate that, in spite of the potential concurrent effects of factors other than the Chl a concentration on the fluorescence intensity, in vivo Chl a fluorescence can be used to trace nondestructively the migratory behavior of benthic microalgae.