Presence Of Cyanobacteria Research Articles

Phytoplankton composition modifies predator-driven life history evolution in Daphnia

Organisms experience competing selective pressures, which can obscure the mechanisms driving evolution. Daphnia ambigua is found in lakes where a predator, the alewife (Alosa pseudoharengus) either does (anadromous) or does not (landlocked) migrate between marine and freshwater. We previously reported an association between alewife variation and life history evolution in Daphnia. However, differences in alewife migration indirectly influence phytoplankton composition for Daphnia. In ‘anadromous lakes’, Daphnia are present in the spring and experience abundant high-quality green algae. Intense predation by young-of-the-year anadromous alewife quickly eliminates these Daphnia populations by early summer. Daphnia from ‘landlocked lakes’ and lakes without alewife (‘no alewife lakes’) are present during the spring and summer and are more likely to experience high concentrations of sub-optimal cyanobacteria during the summer. To explore links between predation, resources, and prey evolution, we reared third-generation laboratory-born Daphnia from all lake types on increasing cyanobacteria concentrations. We observed several significant ‘lake type × resource’ interactions whereby the differences among lake types depended upon cyanobacteria concentrations. Daphnia from anadromous lakes developed faster, were larger at maturation, produced more offspring, and had higher intrinsic rates of increase in the absence of cyanobacteria. Such trends disappeared or reversed as cyanobacteria concentration was increased because Daphnia from anadromous lakes were more strongly influenced by the presence of cyanobacteria. Our results argue that alewife migration and phytoplankton composition both play a role in Daphnia evolution.

CYANOBACTERIAL BLOOMS AND THEIR TOXICITY IN VOJVODINA LAKES, SERBIA

The presence of cyanobacteria (blue-green algae) is a significant indicator of water quality,having in mind that several genera have the quality of producing cyanotoxins, which are harmful to animals,plants and humans. Seven lakes in Vojvodina (Republic of Serbia) were examined in May and September 2007 for cyanobacterial presence and cyanotoxins content, Chl a concentration and index of phosphatase activity as the indicators of water quality. In the spring period, cyanobacteria species were not dominant in only 2 of 14 water samples. Microcystins were detected in all of the lakes examined. The concentrations of microcystins ranged from 6.66 μg/L (Provala Lake) to 199.9 and 238 μg/L (Palic and Ludas Lake respectively).The investigations conducted on 7 water ecosystems in Vojvodina, regarding the basic parameters of eutrophication, Chl a concentration and phosphatase activity index, have rendered the examined ecosystems immensely endangered due to significant water quality deterioration. It was determined that the intensification of eutrophication processes has been linked to the increased presence and abundance of cyanobacteria as well as significant toxin production.

Impact of potassium permanganate on cyanobacterial cell integrity and toxin release and degradation

Potassium permanganate (KMnO4) is commonly used as a pre-treatment oxidant to remove soluble manganese (Mn) and iron (Fe) which can contribute to dirty water in drinking water supplies. Because Mn and Fe problems are commonly associated with thermal stratification in summer and autumn, they frequently coincide with the presence of cyanobacteria. The use of KMnO4 as an oxidant for Mn and Fe control therefore needs to consider the potential impacts on cyanobacterial cell integrity and toxin release. This study aims to assess the effect of KMnO4 on cyanobacteria cell integrity, toxin release and toxin oxidation. A toxic strain of Microcystis aeruginosa was exposed to various concentrations of KMnO4 and the cell integrity of cyanobacteria was measured with flow cytometry. Further the intra- and extra-cellular toxin concentrations were quantified and it was apparent that KMnO4 reduced both the intra- and extra-cellular toxins at low initial concentrations of 1 and 3mgL−1 without complete cell lysis. However, the cell integrity of cyanobacteria was compromised at KMnO4 concentrations of 5mgL−1 and 10mgL−1 and led to intracellular toxin release. In the 10mgL−1 KMnO4 treatment, the total toxin was oxidised after 7h contact time. A model describing the two step process of release and degradation was developed and may provide a tool to assess the risk water quality posed by toxin release. Consequently, it may be possible to use KMnO4 as a pre-treatment for Mn and Fe at concentrations<3mgL−1 and short contact time when cyanobacteria are also present.

Remote estimation of phycocyanin (PC) for inland waters coupled with YSI PC fluorescence probe

Nuisance cyanobacterial blooms degrade water resources through accelerated eutrophication, odor generation, and production of toxins that cause adverse effects on human health. Quick and effective methods for detecting cyanobacterial abundance in drinking water supplies are urgently needed to compliment conventional laboratory methods, which are costly and time consuming. Hyperspectral remote sensing can be an effective approach for rapid assessment of cyanobacterial blooms. Samples (n=250) were collected from five drinking water sources in central Indiana (CIN), USA, and South Australia (SA), which experience nuisance cyanobacterial blooms. In situ hyperspectral data were used to develop models by relating spectral signal with handheld fluorescence probe (YSI 6600 XLM-SV) measured phycocyanin (PC in cell/ml), a proxy pigment unique for indicating the presence of cyanobacteria. Three-band model (TBM), which is effective for chlorophyll-a estimates, was tuned to quantify cyanobacteria coupled with the PC probe measured cyanobacteria. As a comparison, two band model proposed by Simis et al. (Limnol Oceanogr, 50(11): 237-245, 2005; denoted as SM05) was paralleled to evaluate TBM model performance. Our observation revealed a high correlation between measured and estimated PC for SA dataset (R (2) =0.96; range: 534-20,200 cell/ml) and CIN dataset (R (2) =0.88; range: 1,300-44,500 cell/ml). The potential of this modeling approach for imagery data were assessed by simulated ESA/Centinel3/OLCI spectra, which also resulted in satisfactory performance with the TBM for both SA dataset (RMSE % =26.12) and CIN dataset (RMSE % =34.49). Close relationship between probe-measured PC and laboratory measured cyanobacteria biovolume was observed (R (2) =0.93, p<0.0001) for the CIN dataset, indicating a stable performance for PC probe. Based on our observation, field spectroscopic measurement coupled with PC probe measurements can provide quantitative cyanobacterial bloom information from both relatively static and flowing inland waters. Hence, it has promising implications for water resource managers to obtain information for early warning detection of cyanobacterial blooms through the close association between probe measured PC values and cyanobacterial biovolume via remote sensing modeling.

Effect of non-toxic, filamentous cyanobacteria on egg abortion in Daphnia under various thermal conditions

The aim of this study was to examine whether the presence of non-toxic filamentous cyanobacteria can cause egg abortion in Daphnia. To test this hypothesis, we fed females of Daphnia pulicaria with the green alga Scenedesmus obliquus from birth until eggs were laid in the brood chamber. Gravid Daphnia females were then exposed to media containing either S. obliquus or filaments of a non-toxic strain of the cyanobacterium Cylindrospermopsis raciborskii. The females were then observed throughout the whole period of egg development and all events of egg abortion were recorded. Experiments were conducted at three temperatures: 16, 20, and 24°C. In the presence of cyanobacteria, the proportion of aborted eggs ranged from 2.6 to 12.9%, compared with 0–1.8% in the green algae treatment. The number of aborted eggs, but not the number of egg-aborting females, tended to increase at higher temperature. Our data indicate that interference by non-toxic cyanobacterial filaments may affect the reproductive success of Daphnia, not only through suppression of their fecundity, but also via an increase in the number of aborted eggs. Therefore, the reproductive rate of Daphnia based on the fecundity of females may be overestimated in situations where filamentous cyanobacteria are present.

Fitness benefits and costs of induced defenses in Daphnia carinata (Cladocera: Daphnidae) exposed to cyanobacteria

Induced defenses can shape the trophic interactions between prey and predators, but the presence, benefits, and costs of induced defenses against harmful algae in zooplankton are little known. Here, the hypothesis that a short-time exposure to harmful algae can induce defenses in zooplankton was tested by evaluating the fitness changes in a single clone of Daphnia carinata (Cladocera: Daphnidae) after the exposure to a bloom-forming cyanobacterium Microcystis aeruginosa. Life-table experiments revealed that the 1-day exposure to M. aeruginosa significantly enhanced the average life span, the net reproductive rate, and the intrinsic rate of population increase of D. carinata in the presence of cyanobacteria, compared to nonexposed individuals. Then, we tested the second hypothesis that the induced defense in zooplankton would carry a cost on fitness in the absence of cyanobacteria. The 1-day exposure to M. aeruginosa significantly depressed the average life span, the net reproductive rate, and the intrinsic rate of population increase of D. carinata when exclusively feeding on a green alga, Chlorella pyrenoidosa. The induced defense against M. aeruginosa in D. carinata after a short-time exposure explains some aspects of the interactions between harmful algae and zooplankton, and may provide new general insights into the predator–prey “arms race”.

Removal of cyanobacteria by slow sand filtration for drinking water

Potential problems arising from the presence of cyanobacteria in water intended for human consumption have been reported by several researchers. Regarding water treatment plants, intact cells of cyanobacteria should be removed to avoid the release of cyanotoxins due to cell lysis. Water treatment techniques with different degrees of complexity can be employed but, whenever possible, the method of easiest installation, operation and maintenance should be selected, especially for non-industrialized countries and rural communities. In this context, research was carried out to evaluate the efficiency of slow sand filtration to treat water from Gavião reservoir in the city of Pacatuba, Ceara, Brazil, which has exhibited phytoplankton density of approximately 105 cells/mL with a prevalence of cyanobacteria representing over 90% of total cells. The results have demonstrated that slow sand filtration can be used to achieve water purification that meets federal standards. However, it was established that filtration through beds of gravel (prefilter) before the slow sand filtration is essential. The removal of phytoplankton reached values of approximately 97% and the filter run duration was more than 70 days. Furthermore, the slow sand filter was very efficient in removing total coliforms, with removal of up to 99.98%.

International Guidance Manual for the Management of Toxic Cyanobacteria

Cyanobacteria are a concern for water authorities worldwide as their persistence in water supplies causes numerous problems for water treatment plants. However, the major concern associated with the presence of cyanobacteria is the metabolites they produce, taste and odour compounds, particularly 2-methyl isoborneol and geosmin, and a range of toxic compounds known collectively as algal toxins, or cyanotoxins. The management of cyanobacteria and cyanotoxins is one of the priority issues and this international guidance manual aims to consolidate the available knowledge and information: This manual is a user-friendly document that can be accessed on several levels, from basic information for the water quality manager who knows very little about cyanobacteria, to those requiring more detailed guidance on, for example, source water management methods, or doses of activated carbon required to reduce toxin concentration to below the WHO guideline. It is hoped this manual is accessed by water utilities world-wide, and feedback on its application will be used to update and implement revisions to maintain and enhance its usefulness to the international water industry. This title belongs to GWRC Report Series . ISBN: 9781780401355 (eBook)

Spatio-temporal variability of tastes and odors of drinking water within a distribution system

The threshold of human perception in the detection of tastes and odors (T&O) relating to compounds in drinking water is variable. For example, chlorine can be detected at the ppm level and geosmin can be perceived at the ppt level. In this paper, sensory tests (using a human panel), physicochemical analyses (total and free residual chlorine, temperature, metals, geosmin, and 2-methylisoborneol (2MIB)) and microbiological analyses (algae, Actinomycetes and heterotrophic plate count) were performed for water samples collected during a seventeen-month period at ten different locations of a municipal distribution network of Quebec City (Canada). The results showed that different flavors(1) assessed by a panel and aggregated into global flavor intensity (GFI) vary considerably spatially and seasonally. Multiple regression analysis showed that the factors best explaining the variability of GFI are (in order) the season, the location, the concentration of total residual chlorine and the presence of cyanobacteria. Results also demonstrate that chlorine has a masking effect on other T&O.

Optimization of variable fluorescence measurements of phytoplankton communities with cyanobacteria

Excitation–emission fluorescence matrices of phytoplankton communities were simulated from laboratory-grown algae and cyanobacteria cultures, to define the optical configurations of theoretical fluorometers that either minimize or maximize the representation of these phytoplankton groups in community variable fluorescence measurements. Excitation sources that match the photosystem II (PSII) action spectrum of cyanobacteria do not necessarily lead to equal representation of cyanobacteria in community fluorescence. In communities with an equal share of algae and cyanobacteria, inducible PSII fluorescence in algae can be retrieved from community fluorescence under blue excitation (450–470 nm) with high accuracy (R 2 = 1.00). The highest correlation between community and cyanobacterial variable fluorescence is obtained under orange-red excitation in the 590–650 nm range (R 2 = 0.54). Gaussian band decomposition reveals that in the presence of cyanobacteria, the emission detection slit must be narrow (up to 10 nm) and centred on PSII chlorophyll-a emission (~683 nm) to avoid severe dampening of the signal by weakly variable phycobilisomal fluorescence and non-variable photosystem I fluorescence. When these optimizations of the optical configuration of the fluorometer are followed, both cyanobacterial and algal cultures in nutrient replete exponential growth exhibit values of the maximum quantum yield of charge separation in PSII in the range of 0.65–0.7.

The influence of wind dispersion on the presence of cyanobacteria and algae on South African goldmine tailings.

The presence and abundance of cyanobacteria and algae in the air on mine tailings storage facilities that is rehabilitated for different periods were determined.

Linking biotic interactions and climate change to the success of exotic Daphnia lumholtzi

Summary 1. Warmer temperatures may increase cyanobacterial blooms in freshwater ecosystems, yet few ecological studies examine how increases in temperature and cyanobacterial blooms will alter the performance of non-native species. We evaluated how competitive interactions and interactions between these two drivers of ecological change influence the performance of non-native species using the native zooplankton Daphnia pulex and the non-native zooplankton Daphnia lumholtzi as a model system. Based on the literature, we hypothesised that D. lumholtzi would perform best in warmer temperatures and in the presence of cyanobacteria. 2. Laboratory competition experiments showed that in the absence of competitors, growth rates of D. pulex (but not D. lumholtzi) were reduced at higher temperatures and with the cyanobacterial foods Anabaena flos-aquae and Microcystis aeruginosa. In the presence of competitors, however, D. pulex emerged as the superior resource competitor at both temperatures with cyanobacterial food. We therefore predicted that, if competitive interactions are important to its establishment, D. lumholtzi would perform best in the absence of cyanobacteria in heated environments. 3. As predicted, when both species were introduced at low densities in field mesocosms, D. lumholtzi performed best at high temperatures without added cyanobacteria and worst at ambient temperatures with added cyanobacteria, indicating that competitive interactions are likely to be important for its establishment. 4. Taken together, these studies indicate that, while D. lumholtzi may benefit from increases in temperature, associated increased cyanobacterial blooms may hinder its performance. Thus, our findings underscore the importance of considering biotic interactions such as competition when predicting the future establishment of non-native species in response to climate warming.

The impact of cyanobacteria on growth and death of opportunistic pathogenic bacteria

Climate change may cause increased microbial growth in water sources and more knowledge is required on how this may affect the hygienic water quality, i.e., whether increased occurrence of cyanobacteria and algae may stimulate the growth rate of opportunistic pathogenic bacteria. Laboratory experiments were performed to investigate if the presence of the cyanobacteria Anabanea lemmermannii and Microcystis aeruginosa affected the survival and growth rate of the opportunistic pathogenic bacteria Aeromonas hydrophila and Pseudomonas aeruginosa, and the faecal indicators Escherichia coli and coliforms. Cyanobacteria were cultured in bottles containing the nutrient-poor medium 02. Sewage, A. hydrophila or P. aeruginosa was added to cyanobacterial cultures and the bacterial growth and survival was followed. E. coli and coliforms from sewage died within few days and the decay rate was not affected by the presence of cyanobacteria. The presence of Anabaena stimulated the growth rate of P. aeruginosa, but had no effect on the growth rate of A. hydrophila. Microcystis had no effect on the growth rate of P. aeruginosa and an inhibiting effect on the growth rate of A. hydrophila.

Insights into chemotaxonomic composition and carbon cycling of phototrophic communities in an artesian sulfur‐rich spring (Zodletone, Oklahoma, USA), a possible analog for ancient microbial mat systems

Zodletone spring in Oklahoma is a unique environment with high concentrations of dissolved-sulfide (10 mm) and short-chain gaseous alkanes, exhibiting characteristics that are reminiscent of conditions that are thought to have existed in Earth's history, in particular the late Archean and early-to-mid Proterozoic. Here, we present a process-oriented investigation of the microbial community in two distinct mat formations at the spring source, (1) the top of the sediment in the source pool and (2) the purple streamers attached to the side walls. We applied a combination of pigment and lipid biomarker analyses, while functional activities were investigated in terms of oxygen production (microsensor analysis) and carbon utilization ((13)C incorporation experiments). Pigment analysis showed cyanobacterial pigments, in addition to pigments from purple sulfur bacteria (PSB), green sulfur bacteria (GSB) and Chloroflexus-like bacteria (CLB). Analysis of intact polar lipids (IPLs) in the source sediment confirmed the presence of phototrophic organisms via diacylglycerol phospholipids and betaine lipids, whereas glyceroldialkylglyceroltetraether additionally indicated the presence of archaea. No archaeal IPLs were found in the purple streamers, which were strongly dominated by betaine lipids. (13)C-bicarbonate- and -acetate-labeling experiments indicated cyanobacteria as predominant phototrophs in the source sediment, carbon was actively fixed by PSB/CLB/GSB in purple streamers by using near infrared light. Despite the presence of cyanobacteria, no oxygen could be detected in the presence of light, suggesting anoxygenic photosynthesis as the major metabolic process at this site. Our investigations furthermore indicated photoheterotrophy as an important process in both habitats. We obtained insights into a syntrophically operating phototrophic community in an ecosystem that bears resemblance to early Earth conditions, where cyanobacteria constitute an important contributor to carbon fixation despite the presence of high sulfide concentrations.

Formation of assimilable organic carbon during oxidation of natural waters with ozone, chlorine dioxide, chlorine, permanganate, and ferrate

Five oxidants, ozone, chlorine dioxide, chlorine, permanganate, and ferrate were studied with regard to the formation of assimilable organic carbon (AOC) and oxalate in absence and presence of cyanobacteria in lake water matrices. Ozone and ferrate formed significant amounts of AOC, i.e. more than 100 μg/L AOC were formed with 4.6 mg/L ozone and ferrate in water with 3.8 mg/L dissolved organic carbon. In the same water samples chlorine dioxide, chlorine, and permanganate produced no or only limited AOC. When cyanobacterial cells ( Aphanizomenon gracile) were added to the water, an AOC increase was detected with ozone, permanganate, and ferrate, probably due to cell lysis. This was confirmed by the increase of extracellular geosmin, a substance found in the selected cyanobacterial cells. AOC formation by chlorine and chlorine dioxide was not affected by the presence of the cells. The formation of oxalate upon oxidation was found to be a linear function of the oxidant consumption for all five oxidants. The following molar yields were measured in three different water matrices based on oxidant consumed: 2.4–4.4% for ozone, 1.0–2.8% for chlorine dioxide and chlorine, 1.1–1.2% for ferrate, and 11–16% for permanganate. Furthermore, oxalate was formed in similar concentrations as trihalomethanes during chlorination (yield ∼ 1% based on chlorine consumed). Oxalate formation kinetics and stoichiometry did not correspond to the AOC formation. Therefore, oxalate cannot be used as a surrogate for AOC formation during oxidative water treatment.

Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria

Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal.

Fate and effects of nonylphenol in the presence of the cyanobacterium Microcystis aeruginosa

Interactions of nonylphenol (NP), a toxic and oestrogenic degradation product of widely used non-ionic surfactants, with the cyanobacterium Microcystis aeruginosa were studied. Batch cultures were incubated for 10 days with NP concentrations between 10 and 570 nM. NP was removed more quickly in the presence of M. aeruginosa (half-life 2.7–5.2 days) than in its absence (half-life 6.7–10.2 days) at all concentrations tested. At the end of the experiment, NP could not be found in the biomass, so the biotic removal is due to uptake and chemical transformation, and not to physical binding on the cells. The observed effective concentrations, EC50 and EC20, were 0.45 and 0.25 μ M, respectively. Therefore, NP is expected to have toxic effects on M. aeruginosa only in very contaminated surface waters. However, for concentrations that go far beyond environmental levels, cyanobacteria are able to cope with NP toxicity by internalising the compound in a less toxic form. Therefore, the presence of cyanobacteria may increase the rate of NP removal from the aquatic environment.

Comparative studies of cyanobacterial associations with crop plants

Cyanobacteria are very sociable organisms having ability to form symbiotic relationships with a variety of organisms from all other domains of life. Their association with plants is of prime importance. Very less work is done on development of new artificial symbiotic associations between cyanobacteria and crops of agricultural importance. Present study deals with formation of association between cyanobacteria, from different taxonomic classes and different economically important crops. Cyanobacteria, mainly isolated from rice fields were used. These cyanobacteria were co-inoculated with ten days old seedlings for one week. Roots were observed by light microscopy, fluorescent microscopy and confocal laser scanning microscope (CLSM) to locate the presence of cyanobacteria in roots. Chlorophyll-a content from the roots was estimated to quantify the extent of cyanobacterial association with roots. Extracellular polysaccharides (EPS) from cyanobacteria was extracted and characterized for comparison, to find component actively involved in the formation of association. Indole-3-acetic acid was determined in media to view its role in colonization. Cyanobacterial strains were identified by ribotyping. Isolated cyanobacteria were both unicellular and filamentous, Identified as Synechocystis sp., Chroococcidiopsis sp., Oscillatoria sp., Phormidium sp. and Arthrospira sp. on the basis of 16S rRNA. Filamentous cyanobacteria showed significantly more attachment with roots and prefer the entire root. Root tips were not invaded in beginning but in later stages cyanobacterial growth was also present on tips. Unicellular strains were entangled in root hairs in beginning and in later stages colonize the rhizoplane also. After ten days cyanobacteria were also present inside the roots. Cyano-plant association is initiated by EPS, produced by cyanobacteria and strength of attachment depends on extent of cyanobacterial EPS released. It was observed that attachment of cyanobacteria to roots depends more on quality of EPS not on quantity of cyanobacteria. Arthrospira sp. producing maximum EPS showed very less attachment while Oscillatoria sp. and Phormidium sp. were strongly attached. Comparison of EPS components will also show some interesting results (in progress). It was also observed that strains producing indole-3-acetic acid showed more colonization with the roots in comparison with the strains that lack this ability. IAA was also measured in the medium after co-inoculation. These strains have tryptophan dependent pathway for IAA synthesis, so presence of IAA without tryptophan showed IAA synthesis activity in presence of roots. Cyanobacteria can be used in agricultural fields that not only make associations with plants, can also improve the plants growth and the rhizospheric conditions.

Fate and effects of octylphenol in a Microcystis aeruginosa culture medium

Octylphenol (OP) is a xenobiotic with endocrine disrupting properties found in freshwaters worldwide. Its effects have been studied in organisms with nuclear receptors but effects on phytoplankton communities are poorly characterized, despite the fact that these organisms are constantly exposed to this compound. For this reason fate and effects of OP in the cyanobacterium Microcystis aeruginosa were assessed from 10 nM to 5 μM OP concentration. Up to a test concentration of 250 nM, OP removal increased significantly in the presence of cyanobacteria, the compound half-life in the absence of cells being 15 days against 9 days in the presence of the cells. Only 4% of the total OP removed was found bound to the cells, indicating an active metabolization of the compound. Moreover, the role of the exudates produced by M. aeruginosa, in the OP removal from culture medium, was assessed. Culture medium with exudates, resulting from a 7-day growth of M. aeruginosa, spiked with 50 nM OP, showed a higher half-life (22 days). Compared to culture medium without exudates, it can be hypothesized that higher organic matter concentrations make the hydrolysis or photolysis of OP more difficult. In culture media, the cells of M. aeruginosa could compensate and even counteract this, as OP half-life was shortened. At higher OP levels (1.25 and 5 μM) M. aeruginosa growth was impaired, indicating toxic effects. This shortage of biomass prevented the M. aeruginosa-assisted OP withdrawal from the culture media.

A phycocyanin probe as a tool for monitoring cyanobacteria in freshwater bodies

In many countries, the presence of cyanobacteria in freshwater bodies used for both drinking water and recreational purposes is under increasing public health attention. Water managers are considering how to implement monitoring that leads to a minimization of the risks incurred by the users of potentially contaminated sites. To address this question, this study involved assessing the performance of a submersible probe for measuring phycocyanin-specific fluorescence as a function of cyanobacterial biomass, with the aim of applying it as a tool for surveillance management. Its advantages and limits compared to more traditional analyses are discussed. The monitoring of cyanobacteria in the water bodies of western France was carried out using a minifluorimeter specific to the fluorescence of phycocyanin, a pigment specific to cyanobacteria. The results are compared with the analyses recommended by the World Health Organisation (chlorophyll a and cell counting). This study based on nearly 800 samples shows a significant correlation between the phycocyanin content and the cyanobacterial biomass, expressed as the number of cells per mL (R2 = 0.73). This submersible probe is simple and rapid to use, making it possible to take into account horizontal and vertical heterogeneities in the proliferation growth. In this way, we are able to detect at an early stage the conditions that could potentially lead to a risk, in order to start sampling. Due to its sensitivity, this tool proves suitable for monitoring aimed at reducing the risks incurred by the users of contaminated sites and launching preventative actions. The use of the phycocyanin probe provides an effective tool to complement traditional analyses of cyanobacterial presence. It is suggested that a surveillance protocol based on phycocyanin concentration can significantly improved the accuracy of the extent of cyanobacterial bloom development in the light of spatial and temporal variabilities associated with these occurrences.