Analysis of Phytoplankton Pigments by Excitation Spectra of Fluorescence (original) (raw)
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The use of spectral fluorescence methods to detect changes in the phytoplankton community
Eutrophication in Planktonic Ecosystems: Food Web Dynamics and Elemental Cycling, 1998
In vivo fluorescence methods are efficient tools for studying the seasonal and spatial dynamics of phytoplankton. Traditionally the measurements are made using single excitation-emission wavelength combination. During a cruise in the Gulf of Riga (Baltic Sea) we supplemented this technique by measuring the spectral fluorescence signal (SFS) and fixed wavelength fluorescence intensities at the excitation maxima of main accessory pigments. These methods allowed the rapid collection of quantitative fluorescence data and chemotaxonomic diagnostics of the phytoplankton community. The chlorophyll a-specific fluorescence intensities (R) and the spectral fluorescence fingerprints were analysed together with concentrations of chlorophyll a in different algal size-groups, phytoplankton biomass and taxonomic position. The lower level of R in the southern gulf was related to the higher proportion of cyanobacteria relative to total biomass and the lower abundance of small algae. The phycoerythrin fluorescence signal was obviously due to the large cyanobacteria. The basin-wide shift in the shape of chlorophyll a excitation spectra was caused by the variable proportions of differently pigmented cyanobacteria, diatoms and cryptomonads.
Fluorescence properties of natural phytoplankton populations
Marine Biology, 1973
The cellular fluorescence of chlorophyll a in natural phytoplankton was measured during vertical profiling in marine coastal waters. The ratio of in situ fluorescence to chlorophyll a concentration, which was considered as an index of cellular fluorescence, varied over a wide range, with large changes occurring both within the water column and between profiling sites. The variations were caused in part by an inhibition in the fluorescence of cells exposed to intense sunlight. The inhibition, which occurred at irradiances exceeding 0.15 langley (ly)/min, led to diel fluctuations in the fluorescence of those phytoplankton near the sea surface. The remaining variations were independent of changes in temperature, but were unexplained. Both light-dependent and light-independent variations in cellular fluorescence will affect the accuracy of the continuous, fluorometric measurement of in vivo chlorophyll.
Fluorescence Methods for Investigation of Living Cells and Microorganisms
Results of in situ fluorescence investigations on chlorophyll-a (chl-a) of phytoplankton in the Sea of Azov (May to June 2018) and in the Don River estuary (September to November 2019) are presented. Continuous data series of chl-a fluorescence were obtained with flow-through fluorometers. Discrete reference measurements of chl-a concentration and phytoplankton biomass were performed by standard methods for the sake of comparison and eventual corrections. The fluorescence intensity values measured in a lateral surface salinity gradient of the Sea of Azov were found correlating with the obtained data on the chl-a concentration (R 2 = 0.88, n = 27) and phytoplankton biomass (R 2 = 0.90, n = 11). Instead, there was a weak correlation (R 2 = 0.40, n = 33) between the fluorescence and phytoplankton biomass found in the estuary. This disparity in correlations was explained by the difference in conditions during measurements, which affected the fluorescence. There were no significant changes in both temperature and coenotic composition of phytoplankton in the course of the marine expedition. The measurements on the river covered a period characterized by the seasonal variations in the phytoplankton composition and by noticeable temperature fluctuations.
Water Research, 1998
ÐNatural phytoplankton samples were analyzed by a spectrometer which is designed to measure delayed¯uorescence (DF) excitation spectra in the range from 400 to 728 nm. It was possible to detect taxonomical changes in the algal assemblage of Lake Kinneret, Israel using DF spectra as analytical signature. The ratio of spectrally integrated excitation delayed¯uorescence to chlorophyll a concentration (DF/chlorophyll) in samples collected from Lake Kinneret, Israel,¯uctuated throughout the investigation period, which covered the annual bloom of the dino¯agellate Peridinium gatunense. The DF/chl ratio increased with the initiation of Peridinium population build up, reached the highest value when the algal bloom reached its peak and declined with the decrease of algal density. DF intensity was positively correlated with the primary productivity at the depth of maximal productivity, indicating that DF intensity may be used as a rapid probe of this variable.
Fluorescent screening of phytoplankton and organic compounds in sea water
Journal of Environmental Monitoring, 2000
The¯ow-through spectro¯uorometers, FLUO-IMAGER 2 , were developed to measure the abundance of phytoplankton, including the analysis of pigment composition and concentration of organic pollution and dissolved organic matter (DOM), in continuous mode. The measurements can be carried out without the timeconsuming pretreatment of water samples. The analytical concept uses the technique of spectral¯uorescent signatures (SFS), based on the systematized spectral library comprising the SFS of major phytoplankton species and chemical pollution. The SFS technique has been applied for several years in qualitative and quantitative screening of organic compounds and phytoplankton in the Baltic, North and Norwegian Seas. The results of the analysis of phytoplankton pigments, the dynamic processes of bloom development, DOM and oil pollution are presented.
Freshwater Biology, 2005
1. This study introduces delayed fluorescence (DF) excitation spectroscopy as an on-line tool for in situ monitoring of the composition and biomass of various colour classes of phytoplankton when they are photosynthetically active (cyanobacteria, chlorophytes, chromophytes and cryptophytes). The DF data are validated by comparison with those from conventional methods (weekly microscopic counts and the measurement of chlorophyll concentration).2. The composition of phytoplankton as assessed by DF agreed reasonably well with the results from microscopic counts, particularly when differences in chlorophyll-specific DF integrals of the various colour classes were taken into account.3. Integrals of DF spectra were converted into concentration of chlorophyll a using empirical factors derived from field data. The value of the conversion factor was nearly twice as high when the relative abundance of cyanobacteria was low (<15%) than when it was high. The converted DF-chl time series agreed well with chlorophyll measurements particularly when blooms were developing. As the DF method is inherently free of the interference caused by pigment degradation products, the discrepancy between the two data sets increased during the collapse of blooms and when sediment resuspension was intense.4. Fourier spectrum analysis of the time series of DF-chl indicated that samples must be taken, at a minimum, every 2–3 days to capture the dynamics of phytoplankton. As a consequence, the dynamics of various algal blooms, including their timing, duration and net growth rate, could be estimated with greater confidence than by using conventional methods alone.5. On-line DF spectroscopy is an advanced technique for monitoring daily the biomass and composition of the photosynthetically active phytoplankton in aquatic environments, including turbid shallow lakes. At present, the detection limit is around 1 mg DF-chl a m−3 in terms of total biomass but confidence in estimates of phytoplankton composition declines sharply below about 5 mg chl a m−3.6. On-line DF spectroscopy represents a promising approach for monitoring phytoplankton. It will be useful in water management where it can act as an early-warning system of declines in water quality. In basic ecological research it can supplement manual methods. While default calibration spectra may be acceptable for routine monitoring, we suggest a careful individual calibration of the DF spectrometer for basic research. The statistical methods developed here help to assess the adequacy of various calibration sets.
Journal of Marine Systems, 2017
This study presents the results of the first field application of a flow-through multi-wavelength Fast Repetition Rate fluorometer (FRRF) equipped with two excitation channels (458 and 593 nm). This device aims to improve the measurement of mixed cyanobacteria and algae community's photosynthetic parameters and was designed to be easily incorporated into existing ferrybox systems. We present a spatiotemporal analysis of the maximum photochemical efficiency (F v /F m) and functional absorption cross section (σ PSII) recorded from April to August 2014 on a ship-of-opportunity commuting twice per week between Helsinki (Finland) and Travemünde (Germany). Temporal variations of F v /F m and σ PSII differed between areas of the Baltic Sea. However, even though the Baltic Sea is characterized by several physico-chemical gradients, no gradient was observed in F v /F m and σ PSII spatial distribution suggesting complex interactions between biotic and abiotic controls. σ PSII was sensitive to phytoplankton seasonal succession and thus differed according to the wavelength used to excite photosystems II (PSII) pigments. This was particularly true in summer when high σ PSII (593) values were observed later and longer than high σ PSII (458) values, reflecting the role of cyanobacteria in photosynthetic light uptake measured at community scale. In contrast, F v /F m variations were similar after excitation at 458 nm or 593 nm suggesting that the adjustment of F v /F m in response to environmental factors was similar for the different groups (algae vs. cyanobacteria) present within the phytoplankton community.
Use of fluorescence information for automated phytoplankton investigation by image analysis
Journal of Plankton Research, 2008
Automated identification and quantification of algae in microscopic images is a tool that allows high taxonomic resolution with reasonable technical efforts. However, in samples containing various non-algal objects, this is still not a satisfactorily solved problem. We show that autofluorescence information improves discrimination of algae from non-algal objects as well as phycoerythrin (PE) containing algae from others. We analyse the stability of the autofluorescence to estimate its constraints. Cold and dark storage of glutaraldehyde fixed samples maintains autofluorescence sufficiently for 3 weeks. Under repeated excitations, chlorophyll a (Chl a) or PE autofluorescence show an exponential decrease followed by an intermediate maximum. A peak also occurs in emission wavelength ranges without chlorophyll and PE fluorescence. The unspecific autofluorescence causing the peaks is at least partly identical with the blue -green fluorescence (BGF) in plant cells. BGF interferes with identification of algae, thus correction of pigment autofluorescence with such unspecific fluorescence allows a more reliable algal discrimination procedure. A classification scheme for discrimination of Chl a and PE-containing algae shows a high performance in a test with natural samples. Integration of fluorescence and bright-field image information provides a powerful tool for phytoplankton analysis in complex samples.