Photosynthetic Accessory Pigments Research Articles

Effect of Fluoride Toxicity on Physiological and Biochemical Parameters of Wheat (Triticum aestivum)

Wheat is the second most important cereal crop next to rice. Fluoride toxicity effects on physiological (relative water content, chlorophyll and carotenoids) and biochemical (soluble sugar, starch, free amino acid, proline and malondialdehyde (MDA) contents parameters of wheat plants from their germination to maturity and ultimately reduces the yield.A pot experiment was conducted to investigate the effect of different concentrations [0 (T1 ), 50 (T2 ), 100 (T3 ), 200 (T4 ), 250 (T5 ) and 300 (T6 ) mg fluoride kg-1 soil] of fluoride in wheat variety HUW-234. Observation was recorded at 30, 60 and 90 DAS. The results indicate that increased level of fluoride decline RWC, chlorophyll, carotenoids, starch, soluble protein, free amino acid while chlorophyll a: b ratio, soluble sugar, proline and MDA contents increased. The present study revealed that fluoride increased concentrations of soluble sugars, proline and MDA indicated that like other stresses fluoride also caused oxidative stress in wheat. Chlorophyll a : chlorophyll b ratio also increased in plant leaves exposed to fluoride. It is noted that fluoride caused more reduction in level of accessory photosynthetic pigments (chlorophyll b and carotenoids) than in the level of main photosynthetic pigments.

Reutilization of food industrial waste for lutein production with heterotrophic microalgae Chlorella sorokiniana MB-1-M12

BackgroundLutein is a xanthophyll carotenoid commonly found in photosynthetic organisms, such as microalgae and plants. It serves as a photosynthetic accessory pigment and possesses antioxidant properties. Lutein is recognized for its prophylactic use in preventing Age-Related Macular Degeneration (AMD) and is widely employed in health supplements. The demand for lutein is steadily increasing. This study utilized Chlorella sorokiniana MB-1-M12 for heterotrophic growth and lutein production, employing molasses as a model of food industrial waste as an alternative carbon source. MethodsMolasses was hydrolyzed using acids, and the optimal hydrolysis conditions were determined by varying the types and concentrations of the acids. The resulting hydrolysate, which contains reducing sugars, was then recovered and used to support the heterotrophic growth of C. sorokiniana MB-1-M12 for lutein production. Significant FindingsThe best efficiency in molasses hydrolysis was achieved using 0.15 M sulfuric acid, resulting in a maximum sugar recovery of 0.721 gs of reducing sugar per gram of molasses. When the molasses hydrolysate reached a sugar concentration of 10 g/L, it yielded a biomass of 2.57 g/L and a lutein content of 2.1 mg/g. These findings indicate that molasses can effectively serve as a substitute for glucose as a carbon source, although it cannot provide all the essential micronutrients required for biomass growth. Consequently, the addition of nutrients in BG-11 medium became necessary. This study successfully demonstrates the upcycling of waste resources, such as molasses, into a high-value product like lutein, all achieved in a cost-effective and resource-efficient manner.

Highly Efficient Water-Based Extraction of Biliprotein R-Phycoerythrin From Marine the Red-Macroalga Sarcopeltis skottsbergii by Ultrasound and High-Pressure Homogenization Methods

Sarcopeltis skottsbergii is an endemic species of the southern region of South America, with R-phycoerythrin (R-PE) as an accessory photosynthetic pigment. The production of S. skottsbergii is around twenty thousand tons of dry alga per year. The evaluation of (R-PE) in a biorefinery model is still incipient in the algal biotechnology area and will be used in the food, pharmaceutical, cosmeceutical, and nutraceutical industries. This work evaluated the cell disruption and separation processes by using two green technologies, ultrasound-assisted extraction (UAE) and high-pressure homogenization (HPH), to obtain an R-phycoerythrin enriched extract from S. skottsbergii. Two-levels three-factor central composite design (CCD) and response surface methodology (RSM) were carried out to optimize the extraction conditions, including the factors for UAE (time, amplitude, and solvent) and HPH (Pressure, number of passes, and solvent). Additionally, a second-order polynomial fit was performed to fit the experimental data by the green method. HPH method was the most efficient extraction method under the conditions obtained of 100-400 MPa pressure power, 2-3 number of passes, and distilled water as solvent. Furthermore, the experimental extraction yields ranged from 4.4-5.7 mg of PE g-1 of dry biomass under the optimal extraction conditions (400 MPa; 2 passes), which agreed with the predictive yield of 4.6-5.5 mg g-1 DW. The ultrafiltration membrane used for the separation process for both methods exhibited a rejection of R-phycoerythrin concentrated at 30 KDa. Furthermore, R-phycoerythrin showed a positive correlation between the antioxidant capacity (ORAC) in the best-selected extractions. After the extraction, the same pattern was observed in Chlorophyll a and total carotenoids with DPPH. Thus, it was an attractive non-aggressive extraction alternative with biological activity of interest for formulating biotechnological products for the food industry is suggested.

Highlighting Theodor W. Engelmann's “Farbe und Assimilation” [Color and Assimilation

AbstractIn 1883, Theodor Wilhelm Engelmann, a German scientist, wrote his essay “color and assimilation” (Ger.: “Farbe und Assimilation”) describing the state of the art in photosynthesis research, his recent findings, and further assumptions based upon his presented results. Nearly 140 years later, many of his assumptions were proven correct. By his still well‐known bacteria experiments using aerotactic, heterotrophic bacteria, he identified the chloroplasts as the location in which photosynthesis and oxygen production takes place. Furthermore, by evaluating the effects of different light spectra, he constructed the first action spectra that demonstrated the implication of the “green gap” of chlorophylls. He further posited that accessory photosynthetic pigments existed to extend the absorption range of chlorophyll. Although infrequently cited, his work was foundational for current ecological research of the vertical appearance of algae species within the underwater gradient in light spectrum due to specific harvesting of different light spectra, hence complementary chromatic adaptation of communities. This short retrospective highlights this piece of literature that represents an early step toward our current understanding of ecological competition for light spectra.

A Review of Phycobiliproteins of Cyanobacteria: Structure, Function and Industrial Applications in Food and Pharmaceutical Industries

Phycobiliproteins are accessory photosynthetic pigments with a tetrapyrrole structure derived from bacterial strains that are organized on a thylakoid membrane inside a structure called phycobilisomes. Phycobiliproteins have been extensively commercialized in the manufacture of fluorescent probes for clinical and immunological analysis, in addition to their ability to dye with proven antioxidant and medicinal properties. Phycocyanin, Phycoerythrin and Allophycocyanin are the main types of phycobiliproteins that are widely used as useful food supplements today; however, in Iran, the true value of this natural pigment with bioactive properties has not been realized. Todays, the use of artificial colors and antioxidants in food product has led to an increase in cancer in many people. Therefore, awareness of the presence of natural food pigments of natural origin is of particular important. On the other hand, since so far no review article on extraction, separation and purification as well as evaluation of the biological activity of the pigment Phycoerythrin and Phycocyanin, has been published in Iran, so such review articles can pave the way for the introduction of natural edible pigments from cyanobacteria are considered to be usable in the food industry. Therefore, the purpose of this review article is to introduce the structure, function, biosynthesis and different methods of extraction of Phycobiliproteins in industrial dimensions along with different applications of Phycocyanin in food and pharmaceutical industries.

Hemolytic Activity in Relation to the Photosynthetic System in Chattonella marina and Chattonella ovata.

Chattonella species, C. marina and C. ovata, are harmful raphidophycean flagellates known to have hemolytic effects on many marine organisms and resulting in massive ecological damage worldwide. However, knowledge of the toxigenic mechanism of these ichthyotoxic flagellates is still limited. Light was reported to be responsible for the hemolytic activity (HA) of Chattonella species. Therefore, the response of photoprotective, photosynthetic accessory pigments, the photosystem II (PSII) electron transport chain, as well as HA were investigated in non-axenic C. marina and C. ovata cultures under variable environmental conditions (light, iron and addition of photosynthetic inhibitors). HA and hydrogen peroxide (H2O2) were quantified using erythrocytes and pHPA assay. Results confirmed that% HA of Chattonella was initiated by light, but was not always elicited during cell division. Exponential growth of C. marina and C. ovata under the light over 100 µmol m−2 s−1 or iron-sufficient conditions elicited high hemolytic activity. Inhibitors of PSII reduced the HA of C. marina, but had no effect on C. ovata. The toxicological response indicated that HA in Chattonella was not associated with the photoprotective system, i.e., xanthophyll cycle and regulation of reactive oxygen species, nor the PSII electron transport chain, but most likely occurred during energy transport through the light-harvesting antenna pigments. A positive, highly significant relationship between HA and chlorophyll (chl) biosynthesis pigments, especially chl c2 and chl a, in both species, indicated that hemolytic toxin may be generated during electron/energy transfer through the chl c2 biosynthesis pathway.

Overexpression of the Golden SNP-Carrying Orange Gene Enhances Carotenoid Accumulation and Heat Stress Tolerance in Sweetpotato Plants.

Carotenoids function as photosynthetic accessory pigments, antioxidants, and vitamin A precursors. We recently showed that transgenic sweetpotato calli overexpressing the mutant sweetpotato (Ipomoea batatas [L.] Lam) Orange gene (IbOr-R96H), which carries a single nucleotide polymorphism responsible for Arg to His substitution at amino acid position 96, exhibited dramatically higher carotenoid content and abiotic stress tolerance than calli overexpressing the wild-type IbOr gene (IbOr-WT). In this study, we generated transgenic sweetpotato plants overexpressing IbOr-R96H under the control of the cauliflower mosaic virus (CaMV) 35S promoter via Agrobacterium-mediated transformation. The total carotenoid contents of IbOr-R96H storage roots (light-orange flesh) and IbOr-WT storage roots (light-yellow flesh) were 5.4–19.6 and 3.2-fold higher, respectively, than those of non-transgenic (NT) storage roots (white flesh). The β-carotene content of IbOr-R96H storage roots was up to 186.2-fold higher than that of NT storage roots. In addition, IbOr-R96H plants showed greater tolerance to heat stress (47 °C) than NT and IbOr-WT plants, possibly because of higher DPPH radical scavenging activity and ABA contents. These results indicate that IbOr-R96H is a promising strategy for developing new sweetpotato cultivars with improved carotenoid contents and heat stress tolerance.

A comparative study of phycobilliprotein production in two strains of Pseudanabaena isolated from Arctic and tropical regions in relation to different light wavelengths and photoperiods

Phycobiliproteins, which include phycocyanin, allophycocyanin and phycoerythrin, are the group of coloured accessory photosynthetic pigments present in cyanobacteria (blue-green algae). Pseudanabaena is a genus of microscopic cyanobacteria, cosmopolitan in distribution and known to be rich in phycoerythrins. Cyanobacteria are photosynthetic organisms, thus, one of the factors that influences their metabolism is the quality and quantity of incident light. In order to determine the production of phycobiliproteins (mainly phycocyanin and phycoerythrin) in this genus, the quantity of these pigments was investigated in two different strains of Pseudanabaena, P. catenata USMAC16 isolated from an Arctic location (Svalbard) and P. amphigranulata USMAC18 from a tropical location (Tasik Harapan, USM, Malaysia). The aims of this study were twofold. First, to determine the influence of different light wavelengths (white, green and red) and exposure duration (photoperiod of 12–24 h (h)) on phycocyanin and phycoerythrin production in the two strains. Second, to compare the production of phycobiliprotein between the two strains. Highest phycocyanin production was obtained under red light, while phycoerythrin production was highest under green light. Highest production was achieved with photoperiod 24:00 h L:D (L: light, D: dark) in the polar strain and 12:12 h L: D in the tropical strain. P. catenata (Arctic strain) was a good producer of phycoerythrin when grown under green light.

Two-dimensional electronic-Raman spectroscopy.

We present a new technique, two-dimensional electronic-Raman spectroscopy (2DER), which combines femtosecond stimulated Raman spectroscopy and a pulse-shaper-assisted 2D spectroscopic scheme for the actinic pump. The 2DER spectrum presents the initial actinic excitation wavelength with nanometer spectral resolution in the first axis and the detected stimulated Raman spectra in the second axis. We measured the correlation of the electronic and vibrational states in the photosynthetic accessory pigment β-carotene and reveal its photoexcited state manifold.

Isolation and purification of food-grade C-phycocyanin from Arthrospira platensis and its determination in confectionery by HPLC with diode array detection.

C-Phycocyanin is the major phycobiliprotein in Arthrospira platensis, also known as Spirulina, which is a cyanobacterium used as a dietary supplement because of its powerful effects on body and brain. C-phycocyanin is a blue-colored accessory photosynthetic pigment with multiple applications in food industry as natural dye or additive, and in pharmaceuticals. This study presents a simple protocol for the extraction and purification of food-grade C-phycocyanin from Arthrospira platensis. The cell lysis of cyanobacterium was performed by sonication combined with repeated freezing and thawing cycles. The purification of the crude extract of C-phycocyanin was carried out by ammonium sulfate precipitation followed by ion exchange chromatography resulting in 2.5 purity. The purity of phycocyanobilin chromophore has been tested by UV-visible spectrophotometry by monitoring the absorption after each stage of purification. A high-performance liquid chromatography method has been developed and validated for the determination of food-grade C-phycocyanin. Intra- and interday precision values less than 5.6% and recovery greater than 91.2% indicated high precision and accuracy of the method for analysis of C-phycocyanin. The method has been applied to commercial confectionery of blue color and to the purified protein obtained in the first stage of the study.

Phycobilins and Phycobiliproteins Used in Food Industry and Medicine.

Open tetrapyrroles termed phycobilins represent the major photosynthetic accessory pigments of several cyanobacteria and some eukaryotic algae such as the Glaucophyta, Cryptophyta and Rhodophyta. These pigments are covalently bound to so-called phycobiliproteins which are in general organized into phycobilisomes on the thylakoid membranes. In this work we first briefly describe the physico-chemical properties, biosynthesis, occurrence, in vivo localization and roles of the phycobilin pigments and the phycobiliproteins. Then the potential applications and uses of these pigments, pigment-protein complexes and related products by the food industry (e.g., as LinaBlue® or the so-called spirulina extract used as coloring food), by the health industry or as fluorescent dyes are critically reviewed. In addition to the stability, bioavailability and safety issues of purified phycobilins and phycobiliproteins, literature data about their antioxidant, anticancer, anti-inflammatory, immunomodulatory, hepatoprotective, nephroprotective and neuroprotective effects, and their potential use in photodynamic therapy (PDT) are also discussed.

Self-aggregation of synthetic chlorophyll-c derivative and effect of C17-acrylate residue on bridging green gap in chlorosomal model

Abstract A zinc bacteriochlorophyll- d analog possessing a fully π-conjugated porphyrin skeleton and an acrylate residue at the 17-position was prepared by chemical modification of an accessory photosynthetic pigment, chlorophyll- c 1 from a diatom Chaetoceros species. The synthetic zinc chlorophyll- c 1 derivative self-aggregated in a less polar organic solvent and in a solid film to give a red-shifted and broadened visible absorption spectrum, which is similar to that of the main light-harvesting antenna of a green photosynthetic bacterium, where magnesium chlorins with the 17-propionate residue including bacteriochlorophyll- d aggregate in a J -type fashion to form large oligomers. The resulting self-aggregates showed specific and intense absorption bands at around 500 and 600 nm due to the π-extension along the molecular x-axis, which could bridge the “green gap” observed in the above natural antenna system. Visible and infrared absorption spectral analyses revealed that the supramolecular structure of self-aggregates of the zinc chlorophyll- c 1 derivative are comparable to those of the natural antenna, in spite of double dehydrogenation at the 17,18- and 17 1 ,17 2 -positions in the molecule.

Pheophytin a isolated from the seagrass Syringodium isoetifolium plausibly blocks umuC proteins of select bacterial pathogens, in silico.

This investigation is designed to evaluate the antibacterial efficiency of the noodle grass Syringodium isoetifolium, which is commonly found in the Indian coastal waters. Also, this study characterizes the active compound and predicts the mode of action in silico. Human pathogenic bacteria were treated with crude metabolites of S. isoetifolium. The potent fraction b was analysed by UV/VIS, Spectroscopy RP-HPLC, FT-IR, ESI-Mass and 1 H and 13 C NMRs and determined to be a hydrate of pheophytin a (C55 H74 N4 O6 ). The isolated compound Pheo had MIC values of 6·2±0·7 (Salmonella typhi) and 12·5±0·8 (Escherichia coli and Pseudomonas aeruginosa) μgml-1 . Molecular docking studies of the compound were done to find the binding sites on the pathogens using a Molegro Virtual Docker platform. Pheo targets umuC proteins by binding compactly to five amino acid residues with interaction energy of -3·66 and a Moldock score of -160·175. Hence, we conclude that pheophytin a, besides being an accessory photosynthetic pigment, also has proven to be antibacterial against human pathogens. Lesser MIC values with definite binding sites predicted in silico are suggestive of a precise of action for this compound. Easy extraction methods of the active compound that has a definite target render this under-explored seagrass a good source of antibacterial compound against human pathogenic bacteria. This learning may favour more researches in this unexplored area to build up Pheo-based natural products as antibiotic therapies.

The Optimized Concentration and Purity of Spirulina platensis C-Phycocyanin: A Comparative Study on Microwave-Assisted and Ultrasound-Assisted Extraction Methods

Microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction methods to efficiently extract the C-phycocyanin (C-PC) from the blue-green algae, Spirulina platensis, were compared. The results showed that the linear and interaction effects of two parameters of extraction time and buffer pH on C-PC concentration and purity ratio were significant. The C-PC concentration was enhanced by increasing extraction time up to 7 and 25 min for UAE (2.84 mg/mL) and MAE (4.54 mg/mL) processes, respectively. The extraction time significantly had more effect than the buffer pH value on the purity ratio. The highest purity ratio of C-PC in UAE (0.65) and MAE (1.27) technologies was obtained in buffer pH values of 6.0 and 7.0, respectively. The C-PC extracted from the MAE system significantly had higher concentration and purity than that obtained using the UAE procedure. Thus, MAE as an efficient method can be applied to extract heat-sensitive C-PC from S. platensis in an industrial scale. Practical Applications C-phycocyanin (C-PC) is a blue-colored photosynthetic accessory pigment in all cyanobacteria that has high antioxidant activity to enhance the prolonged induction period for fats or oils by preventing peroxidation of unsaturated fatty acids. Finding a proper and novel extraction method is necessary to obtain high-quality C-phycocyanin for using in different food formulations. Optimization of experimental conditions can thus provide selection of a fast and cost-saving process in the extraction of this functional ingredient.

Sea ice algal biomass and physiology in the Amundsen Sea, Antarctica

AbstractSea ice covers approximately 5% of the ocean surface and is one of the most extensive ecosystems on the planet. The microbial communities that live in sea ice represent an important food source for numerous organisms at a time of year when phytoplankton in the water column are scarce. Here we describe the distributions and physiology of sea ice microalgae in the poorly studied Amundsen Sea sector of the Southern Ocean. Microalgal biomass was relatively high in sea ice in the Amundsen Sea, due primarily to well developed surface communities that would have been replenished with nutrients during seawater flooding of the surface as a result of heavy snow accumulation. Elevated biomass was also occasionally observed in slush, interior, and bottom ice microhabitats throughout the region. Sea ice microalgal photophysiology appeared to be controlled by the availability of both light and nutrients. Surface communities used an active xanthophyll cycle and effective pigment sunscreens to protect themselves from harmful ultraviolet and visible radiation. Acclimation to low light microhabitats in sea ice was facilitated by enhanced pigment content per cell, greater photosynthetic accessory pigments, and increased photosynthetic efficiency. Photoacclimation was especially effective in the bottom ice community, where ready access to nutrients would have allowed ice microalgae to synthesize a more efficient photosynthetic apparatus. Surprisingly, the pigment-detected prymnesiophyte Phaeocystis antarctica was an important component of surface communities (slush and surface ponds) where its acclimation to high light may precondition it to seed phytoplankton blooms after the sea ice melts in spring.

Increased physiological performance of the calcifying green macroalga Halimeda opuntia in response to experimental nutrient enrichment on a Caribbean coral reef

Calcifying green macroalgae of the genus Halimeda are widely distributed on coral reefs and may become more abundant under higher nutrient availability. To determine how nutrient enrichment affects the physiological performance of Halimeda opuntia (Linnaeus) J.V.Lamouroux in relation to different water depths, we carried out in situ nutrient enrichment experiments in Curaçao, Netherlands Antilles. H. opuntia was collected in 5m and then incubated at 5 and 15m in clear acrylic cages with or without addition of N and P. Growth, algal tissue composition (internal C, N, and P content, δ15N signatures, protein content), photosynthetic performance and pigment content were measured after 14 days of incubation. Growth rates and total C increased with nutrients and were higher in 5m water depth. N and P content were higher and δ15N signatures were lighter with nutrients in both depths. Photosynthetic performance, concentrations of the main and accessory photosynthetic pigments, and photoprotection also increased with nutrients and showed some response to depth. These results indicate that nutrient enrichment supported a rapid increase in physiological performance of H. opuntia, but with differences in depth. In 5m, more C was allocated to growth, where light levels were sufficient, while in 15m C was allocated to photosynthetic pigments. These results suggest that nutrient enrichment may influence their abundance and depth distribution on the reef.

Isolation, characterization and antioxidative activity of C-phycocyanin from Limnothrix sp. strain 37-2-1

C-phycocyanin (C-PC) is a blue colored accessory photosynthetic pigment found in cyanobacteria. Some of the medicinal properties of Spirulina have been attributed to this pigment, which includes anticancer, antioxidant, and anti-inflammatory activity. We have screened cyanobacteria isolated from freshwater habitats in Florida for their high content of C-PC. Of 125 strains tested, one filamentous strain identified as Limnothrix sp. was selected for further research. This strain produced 18% C-PC of total dry biomass. Here we describe a simple method for obtaining C-PC of high purity without the use of ion exchange chromatography. The procedure is based on pigment precipitation from the cell lysate with an appropriate concentration of ammonium sulfate, then purification with activated carbon and chitosan, followed by a sample concentration using tangential flow filtration. We have shown that when the lower concentration of ammonium sulfate was used, C-PC with higher purity index was recovered. Characterization of C-PC from Limnothrix showed that it had an absorbance maximum at 620nm and fluorescence at 639nm. The molecular mass of intact C-PC was estimated to be ~50kDa with α and β subunits forming dimmers. When C-PC content per unit biomass was compared to that of marketed Spirulina powder, we found that Limnothrix was superior. C-phycocyanin from Limnothrix had an antioxidative activity on DPPH free radicals similar to that found in a natural antioxidant - rutin.

Metal tolerance of an indigenous cyanobacterial strain, Lyngbya putealis

Response of an indigenous cyanobacterial strain ( Lyngbya putealis) isolated from contaminated site to increasing levels of copper and cobalt was investigated in single metal systems. This cyanobacterial strain showed better response when the medium was spiked with metal. As compared to cobalt treatment, copper had more favorable effect. In single metal systems (copper or cobalt), metal treatments positively effected the cyanobacterial growth as indicated by higher concentration of the primary and accessory photosynthetic pigment (chlorophyll and phycobiliproteins), and biomass production at 0.5 mg/L ( M 0.5) as compared to that at control ( M 0). Exopolymer production (exopolysaccharides and extracellular proteins) too tended to increase significantly in response to both copper and cobalt in L. putealis and found to be maximum at metal concentration M 2.0. This species also showed increased accumulation of starch and carbohydrates in presence of metal (copper or cobalt) at M 0.1. But the overall response was better for copper as compared to cobalt in single metal systems for almost all the studied parameters which show that the strain offered good protection against copper but was sensitive to cobalt.

Phytoplankton pigment patterns and community composition in the northern South China Sea during winter

Phytoplankton pigment patterns and community composition were investigated in the northern South China Sea using high-performance liquid chromatography and the CHEMTAX software from February 11 to 23, 2009. We recognized four different vertical distribution patterns of pigments: chlorophyll a (Chi a)-like type, divinyl chlorophyll a (DV Chi a) type, even distribution type, and surface type. The average value of ratios of accessory photo-protective pigments (APP) to accessory photo-synthetic pigments was 0.89±0.63 in the upper 50 m and 0.16±0.06 below 50 m depth. With increasing depth, APP decreased and photo-synthetically active radiation was attenuated. There was an obvious succession in the phytoplankton community from inshore to the open sea. Diatoms were dominant in the inshore region, while pelagophytes, Prochlorococcus, cyanobacteria and prymnesiophytes were dominant in the open sea. The vertical distribution of phytoplankton also differed greatly from inshore to the open sea. In the coastal and shelf region, diatoms were important components in the whole water column. Cyanobacteria also had a high abundance at the Subsurface Chlorophyll a Maxima (SCM) in the shelf region. In the slope and open sea, Prochlorococcus and cyanobacteria were important groups above the SCM, while pelagophytes dominated below the SCM.

Microalgal pigment ratios in relation to light intensity: implications for chemotaxonomy

Pigment-based chemotaxonomy relies upon the assertion that the pigment arrays of mixed microalgal communities (phytoplankton, periphyton, microphytobenthos) can be deconvo- luted in ways to provide an estimate of taxon-specific chlorophyll a (chl a) as a proxy for biomass. This relies on having valid chl a:biomarker pigment ratios. However, pigment ratios change for a variety of reasons. We examined the effects of only light intensity (photon flux density, PFD) on the pigment ratios of 10 species in the phyla Cyanobacteria, Chlorophyta, Chromophyta (Bacillariophyceae), Haptophyta, and Pyrrophyta. Chl a:marker pigment versus PFD (30-45 through 1800 µmol quanta m -2 s -1 ) data revealed distinct trends for photosynthetic accessory pigments (PAP) versus photopro- tective pigments (PPP). Chl a:PAP class pigments (chl b, fucoxanthin, peridinin, echinenone) exhib- ited relative stability (possibly stoichiometry) with increasing PFD, while chl a:PPP class pigment trends revealed large increases in the relative amounts of the PPP pigments (zeaxanthin, myxoxan- thophyll, canthaxanthin, scytonemins). Total chl a cell -1 often decreases in concert with increasing PFD and partially or totally explains the decrease in chl a:PPP ratios. We verified that all 'xanthophyll cycle' pigments expressed large and erratic ratios and therefore did not predict chl a levels. We con- clude that light (400 to 700 nm) measurements taken in the field can offer valuable ancillary data for adjusting pigment-based chemotaxonomic formulae for the study of microalgal communities.