Prokaryotic Algae Research Articles

Broad-range necrophytophagy in the flagellate Orciraptor agilis (Viridiraptoridae, Cercozoa) and the underappreciated role of scavenging among protists.

Protists show diverse lifestyles and fulfill important ecological roles as primary producers, predators, symbionts, and parasites. The degradation of dead microbial biomass, instead, is mainly attributed to bacteria and fungi, while necrophagy by protists remains poorly recognized. Here, we assessed the food range specificity and feeding behavior of the algivorous flagellate Orciraptor agilis (Viridiraptoridae, Cercozoa) with a large-scale feeding experiment. We demonstrate that this species is a broad-range necrophage, which feeds on a variety of eukaryotic and prokaryotic algae, but fails to grow on the tested fungi. Furthermore, our microscopic observations reveal an unexpected flexibility of O. agilis in handling food items of different structures and biochemistry, demonstrating that sophisticated feeding strategies in protists do not necessarily indicate narrow food ranges.

Spirulina platensis: A comprehensive review of its nutritional value, antioxidant activity and functional food potential

BACKGROUND: Spirulina platensis is a well-known photosynthetic prokaryotic alga that has gained recognition in various industries, including food, health, aquaculture and pharmaceuticals. The United Nations acknowledged spirulina as a nutritious food source because of its rich pigments and high protein content. OBJECTIVE: This paper aims to provide an overview of how Spirulina is utilized as both a dietary supplement as well as functional food ingredient in the food industry. METHOD: Spirulina powder can be added to various foods such as bread, cakes and cookies to increase the nutritional value. It is particularly valuable as a dietary supplement in efforts to combat malnutrition in impoverished regions. RESULT: Spirulina platensis is also a source of essential components used in the therapeutic microalgae supplement market. These components include alpha-carotene, astaxanthin, polyunsaturated fatty acids (such as DHA and EPA) and polysaccharides like beta-glucan. CONCLUSION: It is evident that the consumption of spirulina algae can offer both financial benefits and health advantages. Even though there is a large amount of research on the nutritional, environmental and social benefits of spirulina, some natural areas still produce insufficient amounts of the algae. As a result, more and more scientists and researchers throughout the world are pushing for the growth of spirulina farming.

Changes in isotope fractionation during nitrate assimilation by marine eukaryotic and prokaryotic algae under different pH and CO2 conditions

AbstractThe impact of environmental factors on nitrogen (N) and oxygen (O) isotope effects during algal nitrate assimilation causes uncertainty in the field application of sedimentary N isotope records and nitrate isotopes to understand the marine nitrogen cycle. Ocean acidification is predicted to change nitrogen cycling including nitrate assimilation, but how N and O isotope effects during algal nitrate assimilation vary in response to changes in seawater pH and partial pressure CO2 (pCO2) remains unknown. We measured N and O isotope effects during nitrate assimilation and physiological states of the marine diatom Thalassiosira weissflogii and Synechococcus under different pH (8.1 or 7.8) and pCO2 (400 or 800 μatm) conditions. Low pH and/or high pCO2 equally decreased N and O isotope effects during nitrate assimilation by diatoms possibly due to reducing cellular nitrate efflux/uptake ratio and decreased isotope effects for nitrate uptake, whereas they did not affect those by Synechococcus with low intracellular nitrate concentration and limited nitrate efflux. Our results provide compelling experimental evidence showing different changes in N and O isotope effects during nitrate assimilation by marine eukaryotic and prokaryotic phytoplankton at low pH and/or high pCO2. These findings suggest new insight into environmental controls on variability in the isotope effect during algal nitrate assimilation, and have implications for improving a predictive understanding of N and O isotope tools in acidified oceans.

Toxic effects of thallium (Tl+) on prokaryotic alga Microcystis aeruginosa: Short and long-term influences by potassium and humic acid

Thallium (Tl) is a priority pollutant regulated by the US EPA. It is also a critical element commonly used in high technology industries; with an increasing demand for semiconductors nowadays, wastewater discharges from manufacturing plants or metal mining activities may result in elevated levels of thallium in receiving water harming aquatic organisms. Regarding the impact of thallium on freshwater algae, little attention has been paid to prokaryotic physiology through various exposure periods. In this bench-scale study, prokaryotic alga Microcystis aeruginosa PCC 7806 was cultured in modified BG11 medium and exposed to Tl+ (TlNO3) ranging from 250 to 1250 μg/L for 4 and 14 days. Throughout the experiment using flow cytometry assays, algal population, cell membrane integrity, oxidation stress level, and chlorophyll fluorescence were exacerbated following the exposure to 750 μg Tl/L (approximately 4-day effective concentration of Tl+ for reducing 50% of algal population). Potassium and humic acid (HA) (1–5 mg/L) were added to study their influences on the thallium toxicity. With the additions of potassium, thallium toxicities to algal population and physiology were not significantly changed within 4 days, while they were alleviated within 14 days. With the addition of HA at 1 mg/L, cell membrane integrity was significantly attenuated within 4 days; ameliorating effects on algal population and oxidative stress were not observed until day 14. Thallium toxicities on oxidative stress level and photosynthesis activity were exacerbated in the presence of HA at 3–5 mg/L. The study provides useful information for further studies on the mode of toxic action of Tl+ in prokaryotic algae; it also demonstrates the necessity of considering short and long-term exposure durations while incorporating water chemistry into assessment of thallium toxicity to algae.

Tea polyphenols inhibit blooms caused by eukaryotic and prokaryotic algae

With changes in global climate, blooms are becoming more frequent and difficult to control. Therefore, the selection of algal suppressor agents with effective inhibition and environmental safety is of paramount importance. One of the main treatment strategies is to inhibit the release of harmful algal toxins. Tea polyphenols (TP) are natural products that have been widely used in medicine, the environment, and other fields due to their antibacterial and antioxidant properties. To investigate their potential application in the treatment of algal blooms, TP were applied to three different microalgae. TP exhibited strong inhibitory effects towards all three microalgae. They stimulate the accumulation of ROS in algal cells, leading to lipid peroxidation and subsequent damage to the cell membrane, resulting in the rupture and necrosis of Cyclotella sp. and Chlorella vulgaris cells. Remarkably, it was observed that lower concentrations of TP exhibited the ability to induce apoptosis in M. aeruginosa cells without causing any structural damage. This outcome is particularly significant as it reduces the potential risk of microcystin release resulting from cell rupture. Overall, blooms dominated by different algae can be treated by adjusting the concentration of TP, a new algal suppressor, indicating strong potential treatment applications.

NdhS interacts with cytochrome b6 f to form a complex in Arabidopsis.

Cyclic electron transport (CET) around photosystem I (PSI) is crucial for photosynthesis to perform photoprotection and sustain the balance of ATP and NADPH. However, the critical component of CET, cyt b6 f complex (cyt b6 f), functions in CET has yet to be understood entirely. In this study, we found that NdhS, a subunit of NADPH dehydrogenase-like (NDH) complex, interacted with cyt b6 f to form a complex in Arabidopsis. This interaction depended on the N-terminal extension of NdhS, which was conserved in eukaryotic plants but defective in prokaryotic algae. The migration of NdhS was much more in cyt b6 f than in PSI-NDH super-complex. Based on these results, we suggested that NdhS and NADP+ oxidoreductase provide a docking domain for the mobile electron carrier ferredoxin to transfer electrons to the plastoquinone pool via cyt b6 f in eukaryotic photosynthesis.

Design, synthesis and mechanism research of novel algicide based on bioactive fragments synthesis strategy

The frequency and intensity of harmful cyanobacterial blooms (HCBs) are increasing all over the world, their prevention and control have become a great challenge. In this paper, a series of 1,3,4-thiadiazole thioacetamides (T series) were designed and synthesized as potential algaecides. Among them, the compound T3 showed its best algacidal activity against Synechocystis sp. PCC 6803 (PCC 6803, EC50 = 1.51 μM) and Microcystis aeruginosa FACHB 905 (FACHB905, EC50 = 4.88 μM), which was more effective than the lead compound L1 (PCC6803, EC50 = 7.7 μM; FACHB905, EC50 = 8.8 μM) and the commercially available herbicide prometryn (PCC6803, EC50 = 4.64 μM；FACHB905, EC50 = 6.52 μM). Meanwhile, T3 showed a lower inhibitory activity (EC50 = 12.76 μM) than prometryn (EC50 = 7.98 μM) to Chlorella FACHB1227, indicating that T3 had selective inhibition to prokaryotic algae (PCC6803, FACHB905) and eukaryotic algae (FACHB1227). Furthermore, the algacidal and anti-algae activities of T3 were significantly better than those of prometryn, while the toxicity of zebrafish and human cells was less than prometryn. Electron microscope, physiological, biochemical and metabonomic analysis showed that T3 interfered with light absorption and light conversion during photosynthesis by significantly reducing chlorophyll content, thus inhibited metabolic pathways such as the Calvin cycle and TCA cycle, and eventually led to the cell rupture of cyanobacteria. These results afforded further development of effective and safe algaecides.

The evolution of bacterial community structure and function in microalgal-bacterial consortia with inorganic nitrogen fluctuations in piggery digestate

The inorganic nitrogen concentrations in full-scale anaerobic digestion plants always vary seasonally, challenging the removal stability of microalgal-bacterial consortia in treating piggery digestate. Using a continuous photobioreactor, this study revealed the evolution of bacterial community under inorganic nitrogen fluctuations with influent nitrate loading ranged from 11 to 90 mg-N L−1 and influent ammonium loading ranged from 130 to 550 mg-N L−1. The loading of gradient nitrogen concentrations demonstrated that the optimal removal rate of total inorganic nitrogen was 45.62 mg-N L−1 d−1 along with the total chlorophyll concertation of 19.27 mg L−1, when introducing 240 mg-N L−1 of ammonium and 11 mg-N L−1 of nitrate. High throughput sequencing indicated that the dominant community members for nitrogen removal were shifted from prokaryotic algae to nitrifying and denitrifying bacteria, with nitrate being changed to ammonium. With the increasing influent ammonium loading, the suspended microalgal bacterial consortia gradually changed to microalgal bacterial biofilm, which was attributed to the biofilm-producing prokaryotes Thauera Comamona and Arenimonas. Co-occurrence network analyses illustrated that more functional bacterial modules were formed under ammonium fluctuation. Further correlation test identified influent ammonium loading as the important functional parameter shaping the bacterial community. Overall, this study expands our understanding of the homeostasis in microalgal-bacterial system in the cleaner production of piggery digestate.

The severe toxicity of CuO nanoparticles to the photosynthesis of the prokaryotic algae Arthrospira sp.

This research first verified that prokaryotic algae are more sensitive to toxicity of CuO nanoparticles (CuO NPs) than eukaryotic algae and that CuO NPs damaged photosynthesis of prokaryotic algae (Arthrospira sp.) but had no effect on respiration. The Cu2+ released by CuO NPs caused a bending deformation of the thylakoid, which was an important cause of the decline in photosynthetic capacity. In addition, the D1 protein was the most susceptible site to CuO NPs. The degradation of D1 protein reduced photosynthetic electron transport, which enhanced the excess excitation energy to cause the accumulation of reactive oxygen species (ROS) to further result in oxidative stress on algae. Dissolved organic matter (DOM) increased the toxicity of CuO NPs to photosynthesis of Arthrospira sp. The damage of photosynthesis caused by CuO NPs is an important reason why CuO NPs have a serious toxicity to algae.

Triacylglycerol and phytyl ester synthesis in Synechocystis sp. PCC6803

Cyanobacteria are unicellular prokaryotic algae that perform oxygenic photosynthesis, similar to plants. The cells harbor thylakoid membranes composed of lipids related to those of chloroplasts in plants to accommodate the complexes of photosynthesis. The occurrence of storage lipids, including triacylglycerol or wax esters, which are found in plants, animals, and some bacteria, nevertheless remained unclear in cyanobacteria. We show here that the cyanobacterium Synechocystis sp. PCC6803 accumulates both triacylglycerol and wax esters (fatty acid phytyl esters). Phytyl esters accumulate in higher levels under abiotic stress conditions. The analysis of an insertional mutant revealed that the acyltransferase slr2103, with sequence similarity to plant esterase/lipase/thioesterase (ELT) proteins, is essential for triacylglycerol and phytyl ester synthesis in Synechocystis The recombinant slr2103 enzyme showed acyltransferase activity with phytol and diacylglycerol, thus producing phytyl esters and triacylglycerol. Acyl-CoA thioesters were the preferred acyl donors, while acyl-ACP (acyl carrier protein), free fatty acids, or galactolipid-bound fatty acids were poor substrates. The slr2103 protein sequence is unrelated to acyltransferases from bacteria (AtfA) or plants (DGAT1, DGAT2, PDAT), and therefore establishes an independent group of bacterial acyltransferases involved in triacylglycerol and wax ester synthesis. The identification of the gene slr2103 responsible for triacylglycerol synthesis in cyanobacteria opens the possibility of using prokaryotic photosynthetic cells in biotechnological applications.

Assessment of algal biomasses having different cell structures for biosorption properties of acid red P-2BX dye

The increased applications of synthetic dyes in the textile industrial activities have negative implications such as water pollution by dye containing effluents. The treatment of industrial wastewater is important due to the toxic effects of dyes. Biosorption is defined as a relatively economical and eco-friendly wastewater treatment method. The aim of this study was to examine the biosorption of Acid Red P-2BX (ARP-2BX) dye that is extensively used and abundantly found in textile wastewater. The dye biosorption capacities of prokaryotic algae (Phormidium animale) and eukaryotic algae (Scenedesmus sp.) were investigated. The effects of pH (2–10), biosorbent type (ash or dried), initial dye concentration, biosorbent dosage, contact time and temperature were determined. Maximum dye removal was performed by dried P. animale as 99.70 ± 0.27%. The biosorption isotherms and kinetics were also calculated, the ARP-2BX dye biosorption was fitted with Langmuir isotherm and pseudo-second-order kinetic models. In order to analyze the changes that occurred in algal structure, FTIR and elemental analysis were done. The results of this study concluded that P. animale was a favorable biosorbent for treatment of textile wastewater.

The toxicological effects of oxybenzone, an active ingredient in suncream personal care products, on prokaryotic alga Arthrospira sp. and eukaryotic alga Chlorella sp.

Oxybenzone (OBZ; benzophenone-3, CAS# 131-57-7) is a known pollutant of aquatic and marine ecosystems, and is an ingredient in over 3000 personal care products, as well as many types of plastics. The aim of this study is to explore the different toxicities of OBZ on an eukaryotic (Chlorella sp.) and a prokaryotic algae (Arthrospira sp.). OBZ is a photo-toxicant, with all observed toxicities more sever in the light than in the dark. Cell growth and chlorophyll inhibition were positively correlated with increasing OBZ concentrations over time. Twenty days treatment with OBZ, as low as 22.8 ng L−1, significantly inhibited the growth and chlorophyll synthesis of both algae. Both algae were noticeably photo-bleached after 7 days of exposure to OBZ concentrations higher than 2.28 mg L−1. Relatively low OBZ concentrations (0.228 mg L−1) statistically constrained photosynthetic and respiratory rates via directly inhibiting photosynthetic electron transport (PET) and respiration electron transport (RET) mechanisms, resulting in over production of reactive oxygen species (ROS). Transmission and scanning electron microscopy showed that the photosynthetic and respiratory membrane structures were damaged by OBZ exposure in both algae. Additionally, PET inhibition suppressed ATP production for CO2 assimilation via the Calvin-Benson cycle, further limiting synthesis of other biomacromolecules. RET restriction limited ATP generation, restricting the energy supply used for various life activities in the cell. These processes further impacted on photosynthesis, respiration and algal growth, representing secondary OBZ-induced algal damages. The data contained herein, as well as other studies, supports the argument that global pelagic and aquatic phytoplankton could be negatively influenced by OBZ pollution.

Cyanotoxins: Toxins from prokaryotic blue-green algae with immense impact

Cyanotoxins: Toxins from prokaryotic blue-green algae with immense impact

Effects of aeration intensity as agitation in simple photobioreactors on leptolyngbya (cyanobacteria) growth as biofuel feedstock

Indonesia known as a hotspot of biodiversity, including cyanobacteria biodiversity. One member of cyanobacteria (prokaryotic algae) is Leptolyngbya. Leptolyngbya HS-16 is an isolate that had been isolated from hot spring in Red Crater of Gunung Pancar, Sentul, Bogor. As mats-producing microalgae, this strain is a very promising source of Biofuel. Biofuel can be extracted from lipid of microalgal biomass. Bioreactor is a method to encourage the growth of microalgal biomass. To get a best result in growth, agitation must be done, to make sure every single cell of microalgae gets the adequate nutrition. The aeration on simple photobioreactors is set to high and low intensity. The high intensity of aerations average amount are 191 bubble/min, while the low intensity one are 117 bubble/min, with a device that could produce smaller bubble size to reduce the aeration-agitation effect. The research was done to acknowledge the effect of aeration intensity to Leptolygnbya HS-16.

Algal flora of barks of tropical forests of Western Ghats-Perspectives of research

The bark algae constitutes epiphloeic algae which occur on the tree barks. Along with epiphyllic algae which occur on leaves together called epiphytic algae (Haffmann 1989). The epiphytic algae are terrestrial algae found in extreme environments characterized by humidity or by low/high temperature or light intensity. Being in habitats frequently fluctuations of environmental conditions, occur in contrast with the mostly stable aquatic environments. Having exposed to stress situations terrestrial algae develop morphological and physiological adaptations. The prokaryotic blue green algae along with eukaryotic green algae shared major constituents of terrestrial algal populations and the group exists diversity. However the terrestrial algal diversities poorly understood, though they play important role in biodiversity, ecological and economic values. Among the terrestrial algal flora, the algal flora of barks are one of the important components of terrestrial subaerial habitat of tropical region in general and tropical rain forests in particular. The details of investigation on bark algae of tropical forests of India are not available till date except a few scattered reports which deal with occurrence and systematics (Fristch 1907, Haffmann 1989, Fremy 1930). Though the research on bark algae of tropical ecosystem were initiated during the latter part of the 19th century, till date no comprehensive research papers on bark algae of the tropical rain forests are available. An attempt is made to review the potential prospective of investigations on bark algae of tropical ecosystems, based on the earlier literatures with reference to India and neibouring countries. The research paper is also discussed in relation to contemporary research which has carried out in the South Western regions of the India, where lies Western Ghats, which is one of the hot spots of biodiversity.

A new extracellular von Willebrand A domain-containing protein is involved in silver uptake in Microcystis aeruginosa exposed to silver nanoparticles.

Silver nanoparticles (AgNPs) can be toxic for cyanobacteria when present at low nanomolar concentrations, but the molecular mechanisms whereby AgNPs (or free Ag(+) released from AgNPs) interact with these prokaryotic algal cells remain elusive. Here, we studied Ag uptake mechanisms in the prokaryotic cyanobacterium Microcystis aeruginosa exposed to AgNPs by measuring growth inhibition in the absence or presence of high-affinity Ag-binding ligands and by genetic transformation of E. coli with a protein predicted to be involved in Ag uptake. We discovered a new von Willebrand A (vWA) domain-containing protein in M. aeruginosa that mediates Ag uptake from AgNPs when expressed in E. coli. This new Ag transport protein, which is absent in eukaryotic algae, is a potential candidate explaining the higher AgNPs toxicity in cyanobacteria such as M. aeruginosa than that in eukaryotic algae. The present study provides new insights on Ag uptake mechanisms in the prokaryotic algae M. aeruginosa.

Comparative toxicity of sodium carbonate peroxyhydrate to freshwater organisms

Sodium carbonate peroxyhydrate (SCP) is a granular algaecide containing H2O2 as an active ingredient to control growth of noxious algae. Measurements of sensitivities of target and non-target species to hydrogen peroxide are necessary for water resource managers to make informed decisions and minimize risks for non-target species when treating noxious algae. The objective of this study was to measure and compare responses among a target noxious alga (cyanobacterium Microcystis aeruginosa) and non-target organisms including a eukaryotic alga (chlorophyte Pseudokirchneriella subcapitata), microcrustacean (Ceriodaphnia dubia), benthic amphipod (Hyalella azteca), and fathead minnow (Pimephales promelas) to exposures of hydrogen peroxide as SCP. Hydrogen peroxide exposures were confirmed using the I3− method. SCP margins of safety for these organisms were compared with published toxicity data to provide context for other commonly used algaecides and herbicides (e.g. copper formulations, endothall, and diquat dibromide). Algal responses (cell density and chlorophyll a concentrations) and animal mortality were measured after 96h aqueous exposures to SCP in laboratory-formulated water to estimate EC50 and LC50 values, as well as potency slopes. Despite a shorter test duration, M. aeruginosa was more sensitive to hydrogen peroxide as SCP (96h EC50:0.9–1.0mgL−1 H2O2) than the eukaryotic alga P. subcapitata (7-d EC50:5.2–9.2mgL−1 H2O2), indicating potential for selective control of prokaryotic algae. For the three non-target animals evaluated, measured 96-h LC50 values ranged from 1.0 to 19.7mgL−1 H2O2. C. dubia was the most sensitive species, and the least sensitive species was P. promelas, which is not likely to be affected by concentrations of hydrogen peroxide as SCP that would be used to control noxious algae (e.g. M. aeruginosa). Based on information from peer-reviewed literature, other algaecides could be similarly selective for cyanobacteria. Of the algaecides compared, SCP can selectively mitigate risks associated with noxious cyanobacterial growths (e.g. M. aeruginosa), with an enhanced margin of safety for non-target species (e.g. P. promelas).

Effect of nitrogen regime on antioxidant parameters of selected prokaryotic and eukaryotic microalgal species

Nitrogen is a critical element for algal growth and shifting its concentration above or below the optimum concentration may have a deleterious effect on algal cells. Antioxidants are one of the important factors that protect algal cells from stresses, e.g., nitrogen stress. The purpose of this study was to evaluate the biomass, pigments, antioxidant compounds and activities of two algal species, Arthrospira platensis (prokaryotic Cyanophyta) and Pseudochlorella pringsheimii (eukaryotic Chlorophyta) under hypo- and hyper-nitrogen concentrations. In general, the increase in the nitrogen concentrations of the nutrient medium (75 and 6–18 mM for A. platensis and P. pringsheimii, respectively) led to an increase in the biomass yield, pigments and other antioxidant contents. However, this increment was reversed by further N additions. The data showed that the prokaryotic alga (A. platensis) can grow at relatively hyper-nitrogen concentrations rather than the eukaryotic one (P. pringsheimii). The antioxidant enzyme activities for the both species were significantly stimulated with the relatively lower nitrogen concentrations, while increasing the N concentrations in the media decreased the enzyme activities. Despite the superiority of A. platensis as a potent antioxidants source, both algae showed high antioxidant levels compared to the synthetic antioxidant marker (butylated hydroxytoluene, BHT).

Capillary Electrophoresis Single-Strand Conformational Polymorphisms as a Method to Differentiate Algal Species.

Capillary electrophoresis single-strand conformational polymorphism (CE-SSCP) was explored as a fast and inexpensive method to differentiate both prokaryotic (blue-green) and eukaryotic (green and brown) algae. A selection of two blue-green algae (Nostoc muscorum and Anabaena inaequalis), five green algae (Chlorella vulgaris, Oedogonium foveolatum, Mougeotia sp., Scenedesmus quadricauda, and Ulothrix fimbriata), and one brown algae (Ectocarpus sp.) were examined and CE-SSCP electropherogram “fingerprints” were compared to each other for two variable regions of either the 16S or 18S rDNA gene. The electropherogram patterns were remarkably stable and consistent for each particular species. The patterns were unique to each species, although some common features were observed between the different types of algae. CE-SSCP could be a useful method for monitoring changes in an algae species over time as potential shifts in species occurred.

Evaluation of the utility of six measures for algal (Microcystis aeruginosa, Planktothrix agardhii and Pseudokirchneriella subcapitata) viability

Standard algal toxicity tests are used to discern responses of algae to a variety of exposures including pesticides, personal care products and complex mixtures such as runoff and effluents. There are concerns regarding the accuracy, precision and utility of algal viability measures used as endpoints in algal toxicity test protocols. To definitively evaluate six algal viability measures, algae were heat-treated to produce known live:dead cell ratios. Cultures of two prokaryotic algae (Microcystis aeruginosa and Planktothrix agardhii) and a eukaryotic alga (Pseudokirchneriella subcapitata) were boiled for five minutes and mixed after cooling with untreated cultures to produce suspensions of 0%, 25%, 50%, 75% and 100% live algal cells. Optical microscopy was used to assess the viability of algae on a cell-by-cell basis by measuring cell density, uptake of a vital stain (neutral red) and exclusion of a mortal stain (erythrosin b). Aggregate measures of algal cell viability included chlorophyll a concentrations, pheophytin a concentrations and respiration (measured as 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium formazan absorbance (INT)). Cell densities, erythrosin b stained cells and chlorophyll a concentrations correlated with viable M. aeruginosa, P. agardhii and P. subcapitata cells (R2=0.97–0.78, 0.98–0.85 and 0.99–0.97 respectively). Pheophytin a concentrations and neutral red stained cells did not correlate with viable algae (R2=0.41–0.01 and 0.15–0.03 respectively). For INT formazan absorbance, 50%, 75% and 100% viable algae had greater variances and did not strongly correlate (R2=0.75–0.54). This result was likely confounded by respiration associated with resident bacteria. Three of the six methods provided accurate and precise information regarding the viability of both prokaryotic and eukaryotic algae. These methods also have a relatively low initial expense and can be used widely.