Hyperspectral remote sensing of cyanobacterial pigments as indicators of the iron nutritional status of cyanobacteria-dominant algal blooms in eutrophic lakes

Iron can stimulate cyanobacterial growth. Determining iron availability to cyanobacteria is therefore essential for timely warnings of bloom development. The objectives of this study were to determine the key spectral parameters indicating cellular iron status in cyanobacteria and to establish reliable equations for estimating iron nutrition in cyanobacterial cells. Cells, pigments, cellular iron, and spectra of cyanobacteria were measured monthly at 17 sites in Meiliang Bay of Taihu Lake during the summer period of cyanobacterial blooms from 2010 to 2013. Pronounced spatial and temporal variability of cellular iron of cyanobacteria was observed. The previously developed structure-insensitive pigment index (SIPI) and plant senescence reflectance index (PSRI) and the newly proposed chlorophyll a/phycocyanin index (R_Chl/PC) exhibited strong relationships with cyanobacterial cellular iron content. The relationships between the cellular iron concentration and SIPI, PSRI and R_Chl/PC could be expressed as linear, quadratic and cubic functions, respectively. The equations derived herein were tested using independent data from 2008 to 2009, obtained from 31 sites within Taihu Lake. For the three models that included SIPI, PSRI and R_Chl/PC as predictors, the coefficients of determination (R²) between the measured and estimated cellular iron concentration were 0.549, 0.584 and 0.909, and the mean relative errors (RE) were 17.1%, 18.1% and 8.0%, respectively. The overall results indicated that use of the three key hyperspectral parameters, SIPI, PSRI and R_Chl/PC, could be used for non-destructive and real-time monitoring of the iron nutritional status of cyanobacteria-dominant algal blooms in eutrophic lakes.     

Spectral fluorescence signatures in the characterization of phytoplankton community composition

Fluorescence spectral signatures from 28 algal cultures aredescribed.The cultures are split into four groups accordingto their accessory pigments. Phycocyanin and phycoerythrin,characteristic pigments of cyanobacteria, form groups I andII. The characteristic pigment found in group III is chlorophyllb (green and rasinophyte algae) and in group IV it is chlorophyllc (diatoms, dinophytes and some other algae).This preliminarycatalogue of spectral signatures was used to characterize fivenatural phytoplankton communities from brackish water environmentsas a comparison with phytoplankton species found in the samples.Accessory pigments such as phycocyanin and phycoerythrin, characterizinggroups I and II, can be used for identification without confusion.Distinguishing between groups III and IV is more complicated,because their accessory pigments do not have their own fluorescence.These groups can be characterized by increased fluorescenceof chlorophyll a induced by energy excited through chlorophyllb and c. The possibilities of applying the spectral fluorescencesignatures approach to the characterization of natural communitiesare discussed.     

Iron deficiency-induced changes in the photosynthetic pigment composition of field-grown pear (Pyrus communis L) leaves

In this work we characterize the changes induced by iron deficiency in the pigment composition of pear (Pyrus communis L.) leaves grown under high light intensities in field conditions in Spain. Iron deficiency induced decreases in neoxanthin and β-carotene concomitantly with decreases in chlorophyll a, whereas lutein and carotenoids within the xanthophyll cycle were less affected. Iron deficiency caused major increases in the lutein/chlorophyll a and xanthophyll cycle pigments/chlorophyll a molar ratios. The chlorophyll a/chlorophyll b ratio increased in response to iron deficiency. The carotenoids within the xanthophyll cycle in iron-deficient and in iron-sufficient (control) leaves underwent epoxidations and de-epoxidations in response to ambient light conditions. In control leaves dark-adapted for several hours, most of the xanthophyll cycle pigment pool was in the epoxidated form vio-laxanthin, whereas iron-deficient leaves had significant amounts of zeaxanthin. Iron-deficient leaves also exhibited an increased non-photochemical quenching, supporting the possibility of a role for pigments within the xanthophyll cycle in photoprotection.     

Phycobiliprotein fluorescence of Nostoc punctiforme changes during the life cycle and chromatic adaptation: characterization by spectral confocal laser scanning microscopy and spectral unmixing

Many cyanobacteria are highly adaptable to light quality, and many species undergo a complex life cycle. In this study we show that adaptive changes in the photosynthetic apparatus of cyanobacteria are not only caused by environmental, but also by developmental factors. Spectral confocal laser scanning microscopy (CLSM) was used to analyse in vivo the fluorescence spectra of the photosynthetic pigments chlorophyll a (Chl a), allophycocyanin (APC), phycocyanin (PC) and phycoerythrin (PE) of two Nostoc punctiforme strains. Changes in pigment fluorescence emission occurred in different developmental stages. Strain 1:1-26 showed an emission maximum at 674 nm in motile hormogonia stages, whereas vegetative stages showed maxima at 658 and 575 nm. These changes were not caused by chromatic adaptation. In contrast, the second strain (1:1-26lg) showed distinct fluorescence spectra, pigment localization and clear chromatic adaptation in red light. When these properties are known, both strains can be easily distinguished by the spectral CLSM method, which also allows the localization of the pigments within single cells. To calculate the contribution of individual phycobiliproteins to the observed changes, fluorescence spectra were analysed by spectral unmixing. This allowed the mathematical estimation of fluorescence shares for the individual phycobiliproteins in different developmental stages and both before and after chromatic adaptation. It is concluded that care should be taken when characterizing cyanobacteria by differences in pigment fluorescence, because these differences are influenced not only by chromatic adaptation, but also developmental stages. Spectral CLSM offers a powerful method to study the phycobiliprotein composition in vivo.     

Effects of kinetin and nitrogen on growth rates,pigment and protein contents in wild and phycoerythrin-deficient strains of <Emphasis Type="Italic">Hypnea musciformis</Emphasis> (Rhodophyta)

Hypnea musciformis (Wulfen in Jacqu.) J.V. Lamour. is the main source for carrageenan production in Brazil and strains with selected characteristics could improve the production of raw material. The effects of kinetin on growth rates, morphology, protein content, and concentrations of pigments (chlorophyll a, phycoerythrin, phycocyanin, and allophycocyanin) were assessed in the wild strain (brown phenotype) and in the phycoerythrin-deficient strain (green phenotype) of H. musciformis. Concentrations of kinetin ranging from 0 to 50 μM were tested in ASP 12-NTA synthetic medium with 10 μM nitrate (N-limited) and 100 μM nitrate (N-saturated). In N-limited condition, kinetin stimulated growth rates of the phycoerythrin-deficient strain and formation of lateral branches in both colour strains. Kinetin stimulated protein biosynthesis in both strains. However, differences between both nitrogen conditions were significant only in the phycoerythrin-deficient strain. In the wild strain, effects of kinetin on concentrations of phycobiliproteins were not significant in both nitrogen conditions, except for chlorophyll content. However, the phycoerythrin-deficient strain showed an opposite response, and kinetin stimulated the phycobiliprotein biosynthesis, with the highest concentrations of phycoerythrin in N-saturated medium, while the highest concentrations of allophycocyanin and phycocyanin were observed in N-limited medium. These results indicate that the effects of kinetin on growth, morphology, protein and phycobiliprotein contents are influenced by nitrogen availability, and the main nitrogen storage pools in phycoerythrin-deficient strain of H. musciformis submitted to N-limited conditions were phycocyanin and allophycocianin, the biosynthesis of which was enhanced by kinetin.     

Biomass-pigment relationships in potamoplankton

During most of the growing season of 1994, pigment content,as determined by HPLC analysis of algal sample extracts, wasfollowed in the River Meuse (Belgium) potamoplankton. The concentrationof some algal pigments (chlorophylls a and b, fucoxanthin, lutein,echinenone and alloxanthin) was related to biomass estimatesof total phytoplankton and of major taxonomic components (diatoms,green algae, cyanobacteria and cryptomonads). Highly significantlinear regressions were obtained for chlorophyll a-total biomass,fucoxanthin-diatoms, lutein-green algae, chlorophyll b-greenalgae. However, no relationship was found for cyanobacteriaor cryptomonads and their specific pigments, which may be attributedto poor accuracy of biomass estimates for these non-dominantalgae. In conclusion, the good relationship found for dominantalgae and their specific pigments confirms the value of pigmentsas quantitative markers of phytoplankton, as detected in othermarine and freshwater environments.     

Pigment Content of Selected Planktonic Algae in Response to Simulated Natural Light Fluctuations and a Short Photoperiod

The lipophilic photosynthetic pigments in Limnothrix redekei, Planktothrix agardhii (cyanobacteria), Stephanodiscus minutulus, Synedra acus (diatoms), Scenedesmus acuminatus, and Scenedesmus armatus (chlorophycean) all isolated from an eutrophic lake were quantitatively determined by HPLC. The algae were grown semi-continuously under nutrient sufficient conditions at 20°C at a 12/12 h light/dark cycle with constant irradiance or with simulated natural light fluctuations as well as at a 6/18 h light/dark cycle with constant irradiance, all at the same daily light exposure. The zeaxanthin and the myxoxanthophyll contents of cyanobacteria were not influenced by fluctuating light, a short photoperiod or a different sampling time. The chlorophyll b/a ratio, the lutein/chlorophyll a ratio, and the neoxanthin content of chlorophycean as well as the chlorophyll c/a and the fucoxanthin/chlorophyll a ratio of diatoms were only slightly influenced by these factors. Therefore in some cases marker pigment contents and in other cases marker pigment/chlorophyll a ratios may be more useful for quantifying the relative importance of different taxonomic groups in natural phytoplankton. Simulated natural light fluctuations or the length of the photoperiod only slightly influenced the pigment content or the marker pigment/chlorophyll a ratio.     

Phytoplankton pigments and community composition in Lake Tanganyika

1. A 2‐year (2002–2003) survey of chlorophyll and carotenoid pigments is reported for two off‐shore stations of Lake Tanganyika, Kigoma (Tanzania) and Mpulungu (Zambia), and from three cruises between those sites. Chlorophyll a concentrations were low (0.3–3.4 mg m^?3) and average chlorophyll a integrated through the 100 m water column were similar for both stations and years (36.4–41.3 mg m^?2). Most pigments were located in the 0–60 m layer and decreased sharply downward. Chlorophyll a degradation products (phaeophytins and phaeophorbides) were detected at 100 m depth, whereas carotenoids became undetectable. Temporal and seasonal variation of the vertical distribution of pigments was high. 2. The biomass of phytoplankton groups was calculated from marker pigment concentrations over the 0–100 m water column using the CHEMTAX software. On average for the study period, chlorophytes dominated in the northern station, followed by cyanobacteria T1 (type 1, or Synechococcus pigment type), whereas cyanobacteria T1 dominated in the south. Cyanobacteria T2 (type 2, containing echinenone), presumably corresponding to filamentous taxa, were detected in the rainy season. Diatoms (and chrysophytes) developed better in the dry season conditions, with a deep mixed layer and increased nutrient availability. Very large variation in the vertical distribution of algal groups was observed. 3. Our observations on phytoplankton composition are broadly consistent with those from previous studies. Our pigment data provide evidence for the lake‐wide importance of picocyanobacteria and high interannual variation and spatial heterogeneity of phytoplankton in Lake Tanganyika, which may render difficult assessment of long‐term changes in phytoplankton driven by climate change.     

Bio-optical modeling of photosynthetic pigments in corals

The spectral reflectance of coral is inherently related to the amounts of photosynthetic pigments present in the zooxanthellae. There are no studies, however, showing that the suite of major photosynthetic pigments can be predicted from optical reflectance spectra. In this study, we measured cm-scale in vivo and in situ spectral reflectance for several colonies of the massive corals Porites lobata and Porites lutea, two colonies of the branching coral Porites compressa, and one colony of the encrusting coral Montipora flabellata in Kaneohe Bay, Oahu, Hawaii. For each reflectance spectrum, we collected a tissue sample and utilized high-performance liquid chromatography to quantify six major photosynthetic pigments, located in the zooxanthellae. We used multivariate multiple regression analysis with cross-validation to build and test an empirical linear model for predicting pigment concentrations from optical reflectance spectra. The model accurately predicted concentrations of chlorophyll a, chlorophyll c ₂, peridinin, diadinoxanthin, diatoxanthin and β-carotene, with correlation coefficients of 0.997, 0.941, 0.995, 0.996, 0.980 and 0.984, respectively. The relationship between predicted and actual concentrations was 1:1 for each pigment, except chlorophyll c ₂. This simple empirical model demonstrates the potential for routine, rapid, non-invasive monitoring of coral-zooxanthellae status, and ultimately for remote sensing of reef biogeochemical processes.     

Algal pigment diversity in coastal sediments from Kerguelen (sub-Antarctic Islands) reflecting local dominance of green algae,euglenoids and diatoms

Summary High Performance Liquid Chromatography analysis of algal pigments from inter- and subtidal (deep and shallow) sediments from the Kerguelen Islands showed clear differences in the pigment composition at the different stations. High concentrations of chlorophyll c and fucoxanthin were present at all locations, indicating significant diatom densities, chlorophyll b was detected at all sites. At one station the other green algal pigments were also present; here green algae contributed more to chlorophyll a concentrations than diatoms, as estimated by using pigment ratios and microscopic observations. At another location chlorophyll b was associated with a high concentration of diadinoxanthin, indicating an abundance of euglenoids. This indicates that chemotaxonomy can be powerful tool in microphytobenthos studies since enumeration of living cells are difficult as many algae are attached to sediment particles (epipsammic algae). Ways of diagenesis, carotenoid degradation and the role of grazing are briefly mentioned. Phaeophorbide a-like pigments were the most significant chlorophyll a degradation products, with concentrations up to 110 g · g^–1 dry weight sediment, i.e. 10 times the chlorophyll a concentration. Some taxonomic estimations, based on pigments ratios, and their limits, are discussed.     

In-situ fluorescence monitoring of cyanobacteria: Laboratory-based quantification of species-specific measurement accuracy

In recent years, in-situ fluorometers have been extensively deployed to monitor cyanobacteria in near real-time. Acceptable accuracy can be achieved between measured pigments and cyanobacteria biovolume provided the cyanobacteria species are known. However, cellular photosynthetic pigment content and measurement interferences are site and species specific and can dramatically affect sensor reliability. We quantified the accuracy of an in-situ fluorometer compared with traditional methods using mono- and mixed cultures of four different cyanobacterial species. We found: (1) lower pigment content in cultures in stationary phase, (2) higher precision with the sensor compared to traditional pigment quantification methods of measuring phycocyanin and chlorophyll a, (3) species-specific relationships between sensor readings and measurements related to biovolume, (4) overestimation of pigments in mixed compared with mono cultures, (5) dissolved organic matter causing a loss in signal proportional to its degree of aromaticity, and (6) potential to quantify the degree of cell lysis with a fluorescent dissolved organic matter sensor. This study has provided important new information on the strengths and limitations of fluorescence sensors. The sensor readings can provide accurate biovolume quantification and species determination for a number of bloom-forming species when sensors are properly compensated and calibrated.     

ESTIMATION OF CHLOROPHYLL a FROM TIME SERIES MEASUREMENTS OF HIGH SPECTRAL RESOLUTION REFLECTANCE IN AN EUTROPHIC LAKE

We acquired high spectral resolution reflectance data in Carter Lake, a eutrophic oxbow on the Iowa–Nebraska border, from April 1995 to April 1996. Chlorophyll a, total seston, sestonic organic matter, Secchi depth, and nephelometric turbidity were determined for each respective spectral measurement. Changes in algal taxonomic structure and abundance coincided with the development and senescence of a midsummer through autumn bloom of Anabaena. Taxonomic structure was more diverse in late winter and spring when Synedra sp. (diatom) and several chlorophytes and dinoflagellates were present. Overall, chlorophyll a varied from about 20 to 280 μg·L^?1, Secchi transparency from 18 to 74 cm, and seston dry weight from 11 to 48 mg·L^?1 in February and September, respectively. Particulate matter completely dominated lake water light attenuation. Dissolved organic matter had low optical activity. The most sensitive spectral feature to variation in chlorophyll a concentration was the magnitude of the scattering peak near 700 nm. The 700-nm peak correlated to chlorophyll concentration through the relationships between algal pigment absorption near 670 nm and the cell biomass and surface-related scattering signal in the near infrared. An algorithm relating the height of the 700-nm reflectance peak above a reference baseline between 670 and 850 nm to chlorophyll a was accurate and robust despite large variations in optical constituents caused by both strong seasonality in the algal system and short-term variations in seston from wind-induced sediment resuspension. The present algorithms were successfully used in other systems with different seasonality and productivity patterns. The coefficients of the models relating chlorophyll a and spectral reflectance variables appeared to be ecosystem specific: both the intercept and slope for the models in this study were moderately lower than for several other recently published results. We validated our algorithm coefficients with a second, independent dataset. The standard error for chlorophyll a prediction was ±28 μg·L^?1.     

Feeding of biofilm-dwelling nematodes examined using HPLC-analysis of gut pigment contents

The natural feeding behaviour of the nematodes Chromadorina bioculata (Schultze in Carus 1857) and Chromadorina viridis (Linstow 1876) was studied in situ, within epilithic biofilms of the Garonne River (France). Based on their feeding-type characteristics and population dynamics, it was hypothesised that these species feed selectively on microphytobenthos (MPB) within the biofilm, and that among MPB groups, diatoms are preferred. High-performance liquid chromatography (HPLC) was used for separation, identification and quantification of pigments both in nematode guts and in the biofilm. This is the first time that nematode gut pigment contents were examined under natural conditions. Diatoms dominated the MPB which also comprised cyanobacteria and green microalgae. The comparison between chlorophyll a content in nematode guts versus in the biofilm showed that C. bioculata and C. viridis fed opportunistically (non-selectively) on MPB within the biofilm. Only diatom biomarker pigments were found in nematode guts suggesting that they could preferentially fed on diatoms among MPB groups. However, the non-detection of biomarker pigments for other microphyte groups could be also linked to HPLC detection limits. It was estimated that Chromadorina nematodes daily ingested on average 0.03–0.67% of the MPB standing stock. This grazing covered only a small part of their energetic requirements, suggesting that besides MPB they probably also fed on other biofilm food sources. Some considerations on the applicability of the HPLC gut pigment analysis technique for the examination of nematode feeding are also presented.     

Phytoplankton of an eutrophic tropical reservoir: comparison of biomass estimated from counts with chlorophyll-a biomass from HPLC measurements

The seasonal variation of phytoplankton in an eutrophic tropical reservoir was evaluated through photosynthetic pigments analyzed by HPLC. The contributions of algal classes to total chlorophyll a (TChl-a) were estimated by two procedures. The first one used fixed marker pigment/chlorophyll a ratio available from culture studies of the major species of each class. In the second procedure, a matrix factorization program (CHEMTAX) was used to analyze the pigment data. The pigment data were compared with carbon biomass estimated from microscope analysis. A significant correlation between total chlorophyll a (measured by HPLC) and total biomass was obtained, indicating only a slight variation in the content of algal chlorophyll a when compared to its fluctuations in carbon biomass. The interpretation of pigment data with CHEMTAX resulted in a good agreement with biomass. Although displaying some differences, the general pattern of the phytoplankton community dynamics and the major shifts in composition, biomass and the cyanobacterial bloom were evidenced. In contrast, Chl-a biomass estimates from fixed Xan/Chl-a ratios presented poor agreement with microscope data and did not register the principal changes in phytoplankton. Our results also highlighted the needs of better understanding of the relationships between marker pigments, chlorophyll-a and algal biomass.     

The Absorption and Fluorescence Spectra of the Cyanobacterial Phycobionts of Cryptoendolithic Lichens in the High-Polar Regions of Antarctica

The algologically pure cultures of the green–brown cyanobacterium Chroococcidiopsissp. and three cyanobacteria of the genus Gloeocapsa, the blue–green Gloeocapsa sp.₁, the brown Gloeocapsa sp.₂, and the red–orange Gloeocapsa sp.₃, were isolated from sandstones and rock fissures in the high-polar regions of Antarctica. These cyanobacteria are the most widespread phycobionts of cryptoendolithic lichens in these regions. The comparative analysis of the absorption and the second-derivative absorption spectra of the cyanobacteria revealed considerable differences in the content of chlorophyll a and in the content and composition of carotenoids and phycobiliproteins. In addition to phycocyanin, allophycocyanin, and allophycocyanin B, which were present in all of the cyanobacteria studied, Gloeocapsa sp.₂ also contained phycoerythrocyanin and Gloeocapsa sp.₃ phycoerythrocyanin and C-phycoerythrin (the latter pigment is typical of nitrogen-fixing cyanobacteria). The fluorescence spectra of Gloeocapsa sp.₂ and Gloeocapsa sp.₃ considerably differed from the fluorescence spectra of the other cyanobacteria as well. The data obtained suggest that various zones of the lichens may be dominated either by photoheterotrophic or photoautotrophic cyanobacterial phycobionts, which differ in the content and composition of photosynthetic pigments.     

生长素吲哚乙酸对铜绿微囊藻生理生化及产毒特性的影响

为了探究生长素吲哚乙酸(IAA)对产毒铜绿微囊藻(Microcystis aeruginosa)的影响, 从生长、光合色素含量、叶绿素光诱导荧光特征、脂质氧化和微囊藻毒素合成特性等方面, 研究了IAA对M. aeruginosa CHAB6301生理生化及产毒的影响。结果表明, 在低浓度IAA(0.04和0.2 mg/L)条件下, 铜绿微囊藻生长、叶绿素含量、光合系统(PSⅡ)电子传递效率及藻毒素含量均无明显变化, 藻蓝蛋白、别藻蓝蛋白和丙二醛(MDA)含量均低于对照。高浓度IAA(1和5 mg/L)能够促进细胞生长, 提高叶绿素含量, 但是抑制藻蓝蛋白和别藻蓝蛋白含量, 降低膜脂过氧化程度和细胞内藻毒素合成。综合各指标测定结果, 低浓度IAA对M. aeruginosa CHAB6301生长和光合作用影响不明显, 而高浓度IAA可促进藻细胞生长和光合作用, 增加微囊藻水华形成几率。     

PIGMENT AND PHOTOSYNTHETIC RESPONSES OF OSCILLATORIA AGARDHII (CYANOPHYTA) TO PHOTON FLUX DENSITY AND SPECTRAL QUALITY1

The effects of photon flux density (PFD) and spectral quality on biomass, pigment content and composition, and the photosynthetic activity of Oscillatoria agardhii Gomont were investigated in steady-state populations. For alterations of PFD, chemostat populations were exposed to 50, 130 and 230 μmol photons·m^?2·s^?1 of photosynthetic active radiation (PAR). Decreases in biomass, chlorophyll a (Chl a) and c-phycocyanin (CPC) contents, and CPC: Chl a and CPC: carotenoid content was not altered. Increases in the relative abundances of myxoxanthophyll and zeaxanthin and deceases in the relative abundances of echinenone and β-carotene within the carotenoid pigments coincided with increasing PFD. Increases in Chl a-specific photosynthetic rates and maxima and decreases in biomass-specific photosynthetic rates and maxima with increasing PFD were attributed to increased light harvesting by carotenoids per unit Chl a and reduction in total pigment content, respectively. Responses to spectral quality were tested by exposing chemostat populations to a gradient of spectral transmissions at 50 μmol photons·m^?2·s^?1 PAR. Biomass differences among populations were likely attributable to the distinct absorption of the PAR spectrum by Chl a, CPC, and carotenoids. Although pigment contents were not altered by spectral quality, relative abundances of zeaxanthin and echinenone in the carotenoid pigments increased in populations exposed to high-wavelength PAR. The population adapted to green light possessed a greater photosynthetic maximum than populations adapted to other spectral qualities.     

SPECTRAL LIGHT ABSORPTION BY INTACT BLADES OF PORPHYRA ABBOTTAE (RHODOPHYTA): EFFECTS OF ENVIRONMENTAL FACTORS IN CULTURE1

Whole thallus absorptance spectra were recorded for Porphyra abbottae Krishnamurthy gametophytes grown in batch culture at combinations of temperature (8, 10, 12° C), irradiance (17.5, 70, 140 μmol photons·m^?2·s^?1), nutrients (f/4, f/2, f media) and water motion (0, 50, 100, 150 rpm). Light, nutrients, water motion and the interaction of nutrients with water motion all significance affected broadband (400-700 nm) absorptance and absorptance by phycoerythrin (566 nm), phycocyanin (624 nm) and chlorophyll a (680 nm). Absorptances increased in low light, low water motion and high nutrient levels. Shifts in phycoerythrin: chlorophyll a absorptance ratios closely paralleled changes of absorptance by the major pigments, whereas the phycoerythrin: phycocyanin ratio decreased only with increasing nutrient supply Absorptance ratios were significantly correlated with growth rate. Absorptance increased asymptotically with blade thickness or pigment content. Based on previously determined growth rates, nutrient saturated P. abbottae can synthesize photosynthetic pigments in excess of immediate needs. Allocation is given preferentially to the phycobiliproteins, with highest preference for phycocyanin.     

An Endolithic Microbial Community in Dolomite Rock in Central Switzerland: Characterization by Reflection Spectroscopy, Pigment Analyses, Scanning Electron Microscopy, and Laser Scanning Microscopy

A community of endolithic microorganisms dominated by phototrophs was found as a distinct band a few millimeters below the surface of bare exposed dolomite rocks in the Piora Valley in the Alps. Using in situ reflectance spectroscopy, we detected chlorophyll a (Chl a), phycobilins, carotenoids, and an unknown type of bacteriochlorophyll-like pigment absorbing in vivo at about 720 nm. In cross sections, the data indicated a defined distribution of different groups of organisms perpendicular to the rock surface. High-performance liquid chromatography analyses of pigments extracted with organic solvents confirmed the presence of two types of bacteriochlorophylls besides chlorophylls and various carotenoids. Spherical organisms of varying sizes and small filaments were observed in situ with scanning electron microscopy and confocal laser scanning microscopy (one- and two-photon technique). The latter allowed visualization of the distribution of phototrophic microorganisms by the autofluorescence of their pigments within the rock. Coccoid cyanobacteria of various sizes predominated over filamentous ones. Application of fluorescence-labeled lectins demonstrated that most cyanobacteria were embedded in an exopolymeric matrix. Nucleic acid stains revealed a wide distribution of small heterotrophs. Some biological structures emitting a green autofluorescence remain to be identified.     

Qualitative and quantitative composition of pigments in Phaeodactylum tricornutum (Bacillariophyceae) stressed by iron

The effect of Fe(III) deficiency on qualitative and quantitative changes in pigment composition in Phaeodactylum tricornutum Bohlin was demonstrated by HPLC and AAS. Maximum content of pigments showed the diatom cells incubated at the optimum iron concentration, i.e., 10 M. The contents of chlorophyll a, chlorophyll c ₁+c ₂, fucoxanthin, diadinoxanthin and ,-carotene were 109.99, 20.16, 40.39, 1.29 and 1.48 fg per cell, respectively. The results obtained showed that Fe(III) affected qualitative and quantitative pigment composition in P. tricornutum. The content of individual pigments, proportions between accompanying pigments and their ratios to chlorophyll a were important indicators of phytoplankton response to iron stress. The strong reduction in ,-carotene content, several times (2–5) increase in diadinoxanthin level as compared to ,-carotene, and high amount of diadinoxanthin in relation to chlorophyll a were observed in algae growing at very low Fe(III) concentrations, 0.001 and 0.01 M. The data suggested that phytoplankton pigments could be a potential physiological marker.