Presence Of Toxic Cyanobacteria Research Articles

Forward and reverse evolution of multivariate responses to cyanobacteria in experimental waterflea populations

AbstractStudies of rapid evolution under changing environments are important for understanding the evolutionary fate of populations and the future of biodiversity. We used experimental evolution to test whether the presence of toxic cyanobacteria and its subsequent removal could lead to rapid forward and reverse genetic changes in multiple traits of the zooplankter Ceriodaphnia cornuta. In the forward selection experiment, the covariant pattern in multivariate trait space provided strong evidence of adaptive evolution in multiple traits at two selection levels, in the presence of toxic cyanobacteria. The C. cornuta population under high selection pressure showed higher tolerance than those under low selection pressure. The total trait change generated through evolutionary responses (constitutive evolution and evolution of plasticity) ranged from 0.2% to 32.2%, depending on the trait and selection level. After the relaxation of selection, almost all evolved traits were restored to their original state when the C. cornuta population were fed pure green algae. That is, the toxin‐tolerant phenotypes were culled off from the population in the absence of the selection pressure, suggesting a heavy cost of maintaining tolerance. The genotype dynamics indicated that asymmetric intraspecific competition may be the main force driving the rapid reverse evolution. These results suggest that the change in cyanobacteria biomass, from proliferation to decline, resulted in rapid forward and reverse evolution of multivariate phenotypic responses in the freshwater zooplankton grazer C. cornuta.

The presence of microcystins in the coastal waters of Nigeria, from the Bights of Bonny and Benin, Gulf of Guinea.

Microcystins (MCs) are the most studied toxins of cyanobacteria in freshwater bodies worldwide. However, they are poorly documented in coastal waters in several parts of the world. In this study, we investigated the composition of cyanobacteria and the presence of microcystins (MCs) in several coastal aquatic ecosystems of Nigeria. Direct morphological analysis revealed that members of the genus Oscillatoria were dominant with five species, followed by Trichodesmium with two species in Nigerian coastal waters. Oso Ibanilo had the highest cyanobacterial biomass (998 × 103 cells/L), followed by Rivers Ocean (156 × 103 cells/L). Except for the Cross River Ocean, cyanobacteria were present in all the investigated aquatic ecosystems. Ten (10) out of twenty water bodies examined had detectable levels of MCs. Furthermore, genomic DNA analysis for the mcyE gene of microcystin synthetase (mcy) cluster showed identities higher than 86% (query coverage > 96%) with toxic strains of cyanobacteria in all the samples analyzed. Also, the sequences of samples matched those of uncultured cyanobacteria from recreational lakes in Southern Germany. Our findings indicate that the presence of toxic cyanobacteria in coastal waters of Nigeria is of public and environmental health concern.

Timing of maternal exposure to toxic cyanobacteria and offspring fitness in Daphnia magna: Implications for the evolution of anticipatory maternal effects.

Organisms that regularly encounter stressful environments are expected to use cues to develop an appropriate phenotype. Water fleas (Daphnia spp.) are exposed to toxic cyanobacteria during seasonal algal blooms, which reduce growth and reproductive investment. Because generation time is typically shorter than the exposure to cyanobacteria, maternal effects provide information about the local conditions subsequent generations will experience. Here, we evaluate if maternal effects in response to microcystin, a toxin produced by cyanobacteria, represent an inheritance system evolved to transmit information in Daphnia magna. We exposed mothers as juveniles and/or as adults, and tested the offspring's fitness in toxic and non‐toxic environments. Maternal exposure until reproduction reduced offspring fitness, both in the presence and in the absence of toxic cyanobacteria. However, this effect was accompanied by a small positive fitness effect, relative to offspring from unexposed mothers, in the presence of toxic cyanobacteria. This effect was mainly elicited in response to maternal exposure to toxic cyanobacteria early in life and less so during reproduction. None of these effects were explained by changes in egg size. A meta‐analysis using our and others’ experiments suggests that the adaptive value of maternal effects to cyanobacteria exposure is weak at best. We suggest that the beneficial maternal effect in our study is an example of phenotypic accommodation spanning generations, rather than a mechanism evolved to transmit information about cyanobacteria presence between generations.

Cyanobacteria and Cyanotoxins in Sicilian Freshwater Basins (Italy): A Risk Assessment for Drinking Water

The eutrophication of surface waterways led to a rise in harmful cyanobacterial blooms worldwide. Sicily, the biggest Italian region, suffers from a strong drought and a growing scarcity of clean water. Toxin producing Cyanobacteria (CB) in Sicilian dams have been often reported, but they have not been regularly monitored until today. Therefore, health risk associated with cyanotoxins (CTX) in drinking waters remains largely unknown. To prevent urban water crisis in next future, we need to manage all water resources effectively, especially the more dynamic surface freshwater sources. Aim of this study was to monitor the major dams of Sicily used as drinking water supplies to carry out a risk assessment relative to the presence of CB and CTX in raw waters.Seven out of thirty-three Sicilian dams, used as drinking water supply, were monitored seasonally for one year. We collected samples of surface and deep waters. ELISA test was performed to detect sum of CTX microcystins (MCs) and nodularins (NOD). Also, for each sample, CB species were identified.Planktothrix rubescens, Pseudoanabaena sp., Limnothrix redekei, Borzia sp., Merismopedia sp., Oscillatoria sp., Dolichospermum sp. Picocyanobacteria were found in the studied basins. Sums of MCs and NOD were detected in each sample and their concentrations ranged between 2 ng/L and 669 ng/L.Presence of toxic CB (especially P. rubescens) in Sicilian lakes, whose waters are used for drinking purposes, could represent an important risk for human health. Variability of species in a same basin could lead to the selection of the most harmful one and to increase of MCs in drinking waters. In one year of monitoring we usually detected low concentrations of CTX, but in some cases they were close to the reference value that WHO assessed for drinking water (1 µg/L). Even if LC-MS and molecular confirmation are needed, our results suggest that a more regular and frequent surveillance is necessary to minimize risk for human health.

Review of 130 years of research on cyanobacteria in aquatic ecosystems in Serbia presented in a Serbian Cyanobacterial Database

<p>The presence of toxic cyanobacteria in aquatic ecosystems in the territory of the Republic of Serbia was surveyed over a period of several decades. Increasing attention is being paid to some negative consequences that may be caused by these microorganisms. Information from available literary sources regarding the distribution and frequency of cyanobacteria and their toxins over a period of 130 years, together with the effects on humans and wildlife in aquatic ecosystems, were gathered and incorporated into a Serbian Cyanobacterial Database created for the CYANOCOST Action. This database encompasses information on 65 aquatic ecosystems, including rivers, lakes, ponds, canals, irrigation reservoirs, reservoirs used for drinking water supply and reservoirs used for other purposes. Cyanobacterial blooms were found in almost 80% of the investigated aquatic ecosystems. The analysis of the research showed the presence of more than 70 species, including blooms of 24 species from 13 genera. Five species of cyanobacteria: <em>Microcystis aeruginosa</em>, <em>Aphanizomenon flos-aquae</em>, <em>Planktothrix agardhii</em>, <em>Microcystis flos-aquae</em> and <em>Planktothrix rubescens</em> frequently formed blooms in the investigated waterbodies and cyanotoxins were also detected in some of them, which had certain negative effects. Here, we present an overview of data contained in the Serbian Cyanobacterial Database, concerning cyanobacterial distribution, cyanotoxin production and associated biological effects in different types of water bodies from the Republic of Serbia. Also, recent important and major cases of cyanobacterial blooming in reservoirs used for drinking water supply: at Vrutci and Ćelije, the Aleksandrovac irrigation reservoir, the Ponjavica River and Lake Palić, including systematic research on the Lake Ludoš and few fishponds are further described. It can be concluded that cyanobacteria and cyanotoxins are omnipresent in different water bodies throughout the Republic of Serbia. For these reasons it is imperative to continue with the monitoring of cyanobacteria and cyanotoxins, as well as to continuously supplement the established database with new information. The Serbian Cyanobacterial Database represents a treasury of information on cyanobacteria and their toxins, and as a model for other countries in the region and beyond. </p>

The role of environmental factors in the induction of oxidative stress in zebra mussel (Dreissena polymorpha)

The aim of this study was to investigate the influence of specific environmental factors, such as temperature, pH, oxygen concentration, and phosphate, nitrate, chloride, sodium, potassium, sulphate, magnesium and calcium ions concentration, as well as microcystins, on the seasonal variations in the activity of the antioxidant system of the zebra mussel. We examined changes in lipid peroxidation (LPO) levels, glutathione content and the catalase activity of mussels inhabiting the two ecosystems, which differ due to their trophic structure and the presence of toxic cyanobacteria. The results show a relationship between the activity of the antioxidant system of zebra mussels and the seasonal fluctuations of environmental parameters: the symptoms of oxidative stress were generally the highest during spring and the lowest during summer in both ecosystems. Our study also revealed that regardless of the study area the most important factors determining the activity of the antioxidant defences of mussels were the mineral composition (particularly magnesium and calcium ions concentrations) and physical parameters of the water (oxygen concentration and pH). However, factors resulting from the trophic status of studied ecosystems, such as limitations in food resources or high concentration of microcystins during cyanobacterial blooms, were periodically responsible for increased level of LPO in the tissues of zebra mussel. These findings may indicate a limited tolerance of the zebra mussel to the local environmental conditions.

Increasing dominance of small zooplankton with toxic cyanobacteria

Summary Cyanobacterial blooms are often associated with an increase in abundance of small‐bodied zooplankton. The hypothesis that toxic cyanobacteria lead to in the dominance of small‐bodied zooplankton was tested by investigating competitive outcomes with three common cladoceran species, analysing cladoceran remains in sediments, and identifying zooplankton resting eggs. Although the large‐bodied cladoceran Daphnia pulex outcompeted the medium‐sized cladoceran Simocephalus vetulus when fed green algae in laboratory experiments, the presence of toxic cyanobacteria completely altered this competitive outcome. Similar shifts in competitive dominance with the presence of cyanobacteria were observed when both D. pulex and S. vetulus competed with the small‐bodied cladoceran Bosmina longirostris. Sediment cores from Dianshan Lake, the largest shallow lake in Shanghai, and surface sediments from 10 random ponds and rivers in the area were collected to recover the cladoceran and total zooplankton communities. Microcystin concentrations in sediments were used as a proxy for cyanobacterial abundances in nature. Altogether, cladoceran remains representing 10 genera were recovered from the sediment samples. Microcystin concentrations in the Dianshan Lake sediment cores were positively correlated with Bosmina abundance, but negatively correlated with both Daphnia and Diaphanosoma abundance. The proportion of large‐bodied cladocerans significantly declined in relation to small‐bodied species with increasing microcystin concentrations in the lake sediments. Fifty‐eight types of zooplankton resting eggs were recovered in sediments from Shanghai waters and identified using DNA barcoding. The abundance of both a lecanid rotifer and total rotifers significantly increased with increasing cyanobacteria in the sediment cores, whereas the dominant copepod, Sinocalanus tenellus, decreased. However, these trends were not observed in comparison of surface sediments from 10 ponds and rivers in the area. These results indicate that the presence of toxic cyanobacteria may have altered the zooplankton communities and contributed to increased dominance of small‐bodied species. This study also demonstrates that cladoceran remains and zooplankton resting eggs recovered from sediment cores are convenient natural archives for evaluating zooplankton responses to cyanobacterial blooms.

Cyanobacteria in aquaculture systems: linking the occurrence, abundance and toxicity with rising temperatures

The presence of toxic cyanobacteria in aquaculture systems is a matter of concern due to its capability to produce toxin known as microcystin. This study was carried out to determine the presence, abundance and toxic potential of cyanobacteria in selected aquaculture systems in Perak, Malaysia, as well as to identify the potential main trigger of toxic cyanobacterial blooms in aquaculture water. In this study, a total of 40 freshwater fish ponds were sampled from 10 different aquaculture farms in Perak, Malaysia. Results revealed that the most frequently found cyanobacterial taxa in Perak aquaculture water was Microcystis spp., where it was detected in all of the studied ponds. During the sampling period, 75 % of the sampled ponds water contained unsafe levels of microcystin with concentrations up to 295.86 µg MC-LR equivalent L−1. This study also discovered that a combination of temperature and pH was the key environmental factor that triggered the proliferation and toxicity of cyanobacteria, whereby temperature was statistically proven to be a more powerful predictor in comparison with pH. This study has implied that cyanobacteria can present health risk to human through aquaculture fish consumption. Moreover, the risk posed by cyanobacteria in aquaculture systems will be amplified by the influence of global warming, with rising water temperatures up to 32 °C.

Biodiversity and toxin production of cyanobacteria in mangrove swamps in the Red Sea off the southern coast of Saudi Arabia

Abstract This study investigated the diversity and toxin production of cyanobacteria forming microbial mats on the soil surface and mangrove pneumatophores in three different mangrove swamps in the Red Sea off the southern coast of Saudi Arabia. In total, 34 species belonging to 15 genera and five families were recorded. Benthic mats had higher numbers of species (25–31) than pneumatophore mats (10–12). Cyanobacterial biodiversity (H) and species evenness (E) were greater in benthic mats (H=2.52–2.83 and E=0.79–0.83) than in pneumatophore mats (H=1.7–1.82 and E=0.73–0.74). The results showed high similarity of species between different mangrove sites (67.6%–91.7%) and low similarity between benthic and pneumatophore mats at the same site (32.3%–35.75%). During this study, only nine cyanobacterial species were successfully isolated and tested for their toxicity. The extracts of these species exhibited toxicity to Artemia salina (LC50=0.3–5.1 mg l-1). Based on the results of ELISA and HPLC analyses, four species were found to produce microcystins (683–974 μg g-1) and three species produced saxitoxins (58.9–93.8 μg g-1). The presence of toxic cyanobacteria and their toxins in mangrove swamps may pose a risk for marine animals because these toxins can accumulate in aquatic food webs with a potential for transfer to higher trophic levels.

Differential susceptibility of cladoceran species to a saxitoxin-producer strain of Cylindrospermopsis raciborskii (cyanobacteria)

Toxic cyanobacteria can affect several organisms, including herbivorous zooplankton, as cladocerans. In this study we tested the hypothesis that cladoceran species of different body size, origin and degree of exposure to toxic cyanobacteria would respond differently to a saxitoxin(STX)-producing strain of the cyanobacterium Cylindrospermopsis raciborskii (CYRF-01). Newborns were exposed to increasing concentrations of the strain CYRF-01 mixed to a fixed proportion of green algae for 14 days and survivorship, age at first reproduction, clutch size, total offspring and the intrinsic rate of population increase (r), as a measure of fitness, were estimated. Different responses to the strain CYRF-01 were observed, with Daphnia similis (temperate, large size) being more sensitive, followed by Moina micrura (tropical, small size), both presenting symptoms of decreased fitness and paralysis. While Ceriodaphnia richardi (tropical, small size) D. gessneri (tropical, medium size) and Diaphanosoma spinulosum (tropical, small size) showed neither of these symptoms, the later species showed even increased fitness in the cyanobacterial treatments relative to control with green algae, suggesting not only a greater resistance to this strain, but also that it can serve as a nutritional supplement for this cladoceran. In conclusion, the results showed that while some cladocerans species may be negatively affected in their fitness, others may be not affected at all or even utilize STX-producer cyanobacteria as a complementary resource. This suggests that responses of cladocerans to toxic cyanobacteria in nature may vary with species and that the presence of toxic cyanobacteria may shape zooplankton communities to the dominance of more tolerant herbivorous species.

Toxicological aspects of treatment to remove cyanobacterial toxins from drinking water determined using the heterozygous P53 transgenic mouse model

The presence of toxic cyanobacteria in drinking water reservoirs renders the need to develop treatment methods for the ‘safe’ removal of their associated toxins. Chlorine has been shown to successfully remove a range of cyanotoxins including microcystins, cylindrospermopsin and saxitoxins. Each cyanotoxin requires specific treatment parameters, particularly solution pH and free chlorine residual. However, currently there has not been any investigation into the toxicological effect of solutions treated for the removal of these cyanotoxins by chlorine. Using the P53 def transgenic mouse model male and female C57BL/6J hybrid mice were used to investigate potential cancer inducing effects from such oral dosing solutions. Both purified cyanotoxins and toxic cell-free extract cyanobacterial solutions were chlorinated and administered over 90 and 170 days (respectively) in drinking water. No increase in cancer was found in any treatment. The parent cyanotoxins, microcystins, cylindrospermopsin and saxitoxins were readily removed by chlorine. There was no significant increase in the disinfection by-products trihalomethanes or haloacetic acids, levels found were well below guideline values. Histological examination identified no effect of treatment solutions except male mice treated with chlorinated cylindrospermopsin (as a cell free extract). In this instance 40% of males were found to have fatty vacuolation in their livers, cause unknown. It is recommended that further toxicology be undertaken on chlorinated cyanobacterial solutions, particularly for non-genotoxic carcinogenic compounds, for example the Tg. AC transgenic mouse model.

Calanoid copepods feed and produce eggs in the presence of toxic cyanobacteria Nodularia spumigena

Feeding and fecundity of two calanoid copepod species (Acartia bifilosa and Eurytemora affinis) were studied in a food assemblage dominated by toxic cyanobacteria, to reveal whether mesozooplankton are able to obtain sufficient good quality food in different phases of a cyanobacteria bloom. Bloom conditions were simulated in a mesocosm by adding a high concentration of cultured hepatotoxic Nodularia spumigena to 100 mm filtered natural sea water. This seston was fed to copepods at days 1, 7, and 14 from the start of the mesocosm experiment, when it consisted of actively growing cyanobacteria (days 1 and 7) and increasing amounts of heterotrophic organisms and probably detritus (day 14). From bulk changes in chlorophyll and estimated ratios between chlorophyll and accessory pigments, it appears that both copepod species ingested large quantities of cyanobacteria in the first experiment but switched to ciliates when those became more abundant. Egg production of A. bifilosa was observed in all experiments, irrespective of the high concentration of nodularin in the mesocosm. The results demonstrate that the dominant copepod species of the Baltic Sea are able to feed, survive, and produce eggs in a plankton community dominated by toxic cyanobacteria.

Life history responses of Daphnia clones to toxic Microcystis at different food levels

We examined how the amount of food of good quality, Scenedcsmus obtusiusculus, influ- enced the toxic effects of the cyanobacterium Microcystis acruginosa on Daphnia pulex in a 21 day life table experiment. Our results show that all hie history traits studied, i.e. longevity, growth and reproduction, of D.pulex were negatively affected by toxic Microcystis. The detrimental effects on these life history traits were less pronounced at increasing food levels. In addition, D.pulex clones dif- fered in their life history responses to toxic Microcystis, suggesting that the presence of toxic cyanobacteria may modify the outcome among D.pulex clones.

Daphnia vertical distribution and the presence of toxic cyanobacteria

Daphnia can alter its vertical position in the water column in response to chemical cues from predators. In this study we tested the hypothesis that a Daphnia pulex clone with little evolutionary exposure to cyanobacteria would move away from patches of cyanobacteria (Anabaena affinis and A. flos-aquae) which contain potent endotoxins. Daphnia was censused at 2 h intervals for 6 h in laboratory columns in which there was a steep vertical gradient of cyanobacteria. Data were analyzed by repeated-measures ANOVA. Control (no Anabaena) and experimental columns showed no significant differences in Daphnia distributions. Daphnia in experimental columns frequently moved into areas with dense concentrations of Anabaena and stayed there for long periods of time. Our results show that this D. pulex clone does not exhibit a rapid (within 6 h) avoidance response to toxic Anabaena.

Microcystin class of toxins: health effects and safety of drinking water supplies

The microcystins are produced by several species of common planktonic cyanobacteria found in surface waters, but their biological function remains unknown. The microcystins have been shown to be extremely potent hepatotoxins in a variety of experimental animals and they are lethal at low doses. Microcystin-LR, one of over 40 microcystin analogues, has also been shown to be a potent tumor promoter. The toxic effects of the microcystins have been attributed to the inhibition of protein phosphatases. This inhibition causes collapse of the cytoskeleton and interferes with a general signal transduction mechanism in cells. The presence of toxic cyanobacteria in surface water has been documented in all parts of the world. The microcystins have been related to a few incidents of human illness and several incidents of animal poisoning in Canada, United States, Australia, Europe, and Africa. Therefore, exposure to the microcystins is a potentially significant health risk and toxin removal from drinking water is becoming a concern worldwide. Conventional water treatment processes (coagulation/sedimentation, chlorination) have generally proven ineffective at removing microcystin toxins from drinking water. Activated carbon, ozone, and free chlorine have been effective in removing microcystins below detectable concentrations in laboratory experiments. Considering these factors, the occurrence of microcystins in drinking water supplies deserves serious attention to insure that adverse health effects are prevented.Key words: microcystins, hepatotoxins, cyanobacteria, blue-green algae, water treatment, health risk.