Cyanobacteria, Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons.

The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.

Analytical Technique Optimization on the Detection of ß-cyclocitral in Microcystis Species.

ß-Cyclocitral, specifically produced by Microcystis, is one of the volatile organic compounds (VOCs) derived from cyanobacteria and has a lytic activity. It is postulated that ß-cyclocitral is a key compound for regulating the occurrence of cyanobacteria and related microorganisms in an aquatic environment. ß-Cyclocitral is sensitively detected when a high density of the cells is achieved from late summer to autumn. Moreover, it is expected to be involved in changes in the species composition of cyanobacteria in a lake. Although several analysis methods for ß-cyclocitral have already been reported, ß-cyclocitral could be detected using only solid phase micro-extraction (SPME), whereas it could not be found at all using the solvent extraction method in a previous study. In this study, we investigated why ß-cyclocitral was detected using only SPME GC/MS. Particularly, three operations in SPME, i.e., extraction temperature, sample stirring rate, and the effect of salt, were examined for the production of ß-cyclocitral. Among these, heating (60 °C) was critical for the ß-cyclocitral formation. Furthermore, acidification with a 1-h storage was more effective than heating when comparing the obtained amounts. The present results indicated that ß-cyclocitral did not exist as the intact form in cells, because it was formed by heating or acidification of the resulting intermediates during the analysis by SPME. The obtained results would be helpful to understand the formation and role of ß-cyclocitral in an aquatic environment.

Quantitative determination by screening ELISA and HPLC-MS/MS of microcystins LR, LY, LA, YR, RR, LF, LW, and nodularin in the water of Occhito lake and crops.

The occurrence of harmful cyanobacterial blooms in surface waters is often accompanied by the production of a variety of cyanotoxins, and these toxins are designed to target in humans specific organs on which they act. When introduced into the soil ecosystem by spray irrigation of crops, they may affect the same molecular pathways in plants having identical or similar target organs, tissues, cells, or biomolecules. There are also several indications that terrestrial plants, including crops, can bioaccumulate cyanotoxins and present, therefore, potential health hazards for humans. During this project, for monitoring purposes, water samples were collected from lake Occhito, in which there was an algal bloom (Planktothrix rubescens) in 2009, and from three tanks which acted as hydraulic junctions. In addition, crop samples irrigated with water from the three tanks mentioned above were also picked. Finally, the characterization of principal cyanobacteria was performed, to determine the presence of cyanotoxins such as microcystins and validate a method of screening ELISA for the determination of microcystins in vegetable samples and a confirmatory method by HPLC-ESI-MS/MS. Graphical abstract Occhito lake (left), microcystin LR (center), Tomato field in Foggia (right); figures below: ELISA (left), HPLC-MS/MS (right).

Immunomodulatory Potency of Microcystin, an Important Water-Polluting Cyanobacterial Toxin.

Microcystins (MCs) are primarily hepatotoxins produced by cyanobacteria and are responsible for intoxication in humans and animals. There are many incidents of chronic exposure to MCs, which have been attributed to the inappropriate treatment of water supplies or contaminated food. Using RAW 264.7 macrophages, we showed the potency of microcystin-LR (MC-LR) to stimulate production of pro-inflammatory cytokines (tumor necrosis factor α and interleukin-6) as a consequence of fast nuclear factor κB and nitrogen-activated protein kinase activation. In contrast to other studies, the observed effects were not attributed to the intracellular inhibition of protein phosphatases 1/2A due to lack of specific transmembrane transporters for MCs. However, the MC-LR-induced activation of macrophages was effectively inhibited by a specific peptide that blocks signaling of receptors, which play a pivotal role in the innate immune responses. Taken together, we showed for the first time that MC-LR could interfere with macrophage receptors that are responsible for triggering the above-mentioned signaling pathways. These findings provide an interesting mechanistic explanation of some adverse health outcomes associated with toxic cyanobacteria and MCs.

The possible role of cyanobacterial filaments in coral black band disease pathology.

Black band disease (BBD), characterized by a black mat or line that migrates across a coral colony leaving behind it a bare skeleton, is a persistent disease affecting massive corals worldwide. Previous microscopic and molecular examination of this disease in faviid corals from the Gulf of Eilat revealed a number of possible pathogens with the most prominent being a cyanobacterium identified as Pseudoscillatoria coralii. We examined diseased coral colonies using histopathological and molecular methods in order to further assess the possible role of this cyanobacterium, its mode of entry, and pathological effects on the coral host tissues. Affected areas of colonies with BBD were sampled for examination using both light and transmission electron microscopies. Results showed that this dominant cyanobacterium was found on the coral surface, at the coral-skeletal interface, and invading the polyp tissues and gastrovascular cavity. Although tissues surrounding the invasive cyanobacterial filaments did not show gross morphological alterations, microscopic examination revealed that the coral cells surrounding the lesion were dissociated, necrotic, and highly vacuolated. No amoebocytes were evident in the mesoglea of affected tissues suggesting a possible repression of the coral immune response. Morphological and molecular similarity of the previously isolated BBD-associated cyanobacterium P. coralii to the current samples strengthens the premise that this species is involved in the disease in this coral. These results indicate that the cyanobacteria may play a pivotal role in this disease and that the mode of entry may be via ingestion, penetrating the coral via the gastrodermis, as well as through the skeletal-tissue interface.

Combined exposure of carps (Cyprinus carpio L.) to cyanobacterial biomass and white spot disease.

OBJECTIVES: Under environmental conditions, fish can be exposed to multiple stressors including natural toxins and infectious agents at the same time. This study brings new knowledge on the effects of controlled exposure to multiple stressors in fish. The aim of this study was to test the hypothesis that influence of cyanobacterial biomass and an infection agent represented by the white spot disease can combine to enhance the effects on fish. METHODS: Common carps were divided into four groups, each with 40 specimens for 20 days: control group, cyanobacterial biomass exposed group, Ichthyophthirius multifiliis-infected fish (Ich) and cyanobacterial biomass-exposed fish + Ichthyophthirius multifiliis-infected fish. During the experiment we evaluated the clinical signs, mortality, selected haematological parameters, immune parameters and toxin accumulation. RESULTS: There was no mortality in control fish and cyanobacterial biomass-exposed fish. One specimen died in Ichthyophthirius multifiliis-infected fish and the combined exposure resulted in the death of 13 specimens. The whole leukocyte counts (WBC) of the control group did not show any significant differences. Cyanobacteria alone caused a significant increase of the WBC on day 13 (p≤0.05) and on day 20 (p≤0.01). Also, I. multifiliis caused a significant elevation of WBC (p≤0.01) on day 20. Co-exposition resulted in WBC increased on day 13 and decrease on day 20, but the changes were not significant. It is evident from the differential leukocyte counts that while the increase of WBC in the group exposed to cyanobacteria was caused by elevation of lymphocytes, the increase in the group infected by I. multifiliis was due to the increase of myeloid cells. It well corresponds with the integral of chemiluminescence in the group infected by I. multifiliis, which is significantly elevated on day 20 in comparison with all other groups. CONCLUSIONS: We can confirm additive action of different agents on the immune system of fish. While single agents seemed to stimulate the immune response, the combination of both caused immunosuppression.

Plankton microorganisms coinciding with two consecutive mass fish kills in a newly reconstructed lake.

Lake Karla, Greece, was dried up in 1962 and its refilling started in 2009. We examined the Cyanobacteria and unicellular eukaryotes found during two fish kill incidents, in March and April 2010, in order to detect possible causative agents. Both microscopic and molecular (16S/18S rRNA gene diversity) identification were applied. Potentially toxic Cyanobacteria included representatives of the Planktothrix and Anabaena groups. Known toxic eukaryotes or parasites related to fish kill events were Prymnesium parvum and Pfiesteria cf. piscicida, the latter being reported in an inland lake for the second time. Other potentially harmful microorganisms, for fish and other aquatic life, included representatives of Fungi, Mesomycetozoa, Alveolata, and Heterokontophyta (stramenopiles). In addition, Euglenophyta, Chlorophyta, and diatoms were represented by species indicative of hypertrophic conditions. The pioneers of L. Karla's plankton during the first months of its water refilling process included species that could cause the two observed fish kill events.

Massive fish death associated with the toxic cyanobacterial Planktothrix sp. bloom in the Béni-Haroun Reservoir (Algeria).

In July 2017, a massive bloom of the potentially toxic cyanobacterial species Planktothrix sp. was observed in the Béni-Haroun Reservoir (Algeria), which was followed by a massive fish death. Many questions were raised in association with the role of cyanotoxins and the fish massive mortality. The objective of this paper is twofold: (1) to investigate the variability of physicochemical and cyanobacterial parameters (chlorophyll-a, phycocyanin, allophycocyanin, and microcystins) throughout the period of July 2017 to June 2018; and (2) to determine the free and total MC levels in viscera and muscle tissues of the common carp (Cyprinus carpio), which are found dead in the considered reservoir in October 2017. Our results showed microcystin (MC) concentrations in water samples (by the protein phosphatase PP2A assay) had reached 651.2 ng MC-LR equiv./L. Total MC levels (free + bound) in the viscera and muscle tissues of sampled dead fish were at 960.24 and 438.54 µg MC-LR equiv./kg dw, respectively. It is assumed that high concentrations of MC observed in the tissues of common carp induced a strong degradation of the visceral contents resulting in the complete lysis of the hepatopancreas, and presumably the massive fish death.

Cyanotoxins: bioaccumulation and effects on aquatic animals.

Cyanobacteria are photosynthetic prokaryotes with wide geographic distribution that can produce secondary metabolites named cyanotoxins. These toxins can be classified into three main types according to their mechanism of action in vertebrates: hepatotoxins, dermatotoxins and neurotoxins. Many studies on the effects of cyanobacteria and their toxins over a wide range of aquatic organisms, including invertebrates and vertebrates, have reported acute effects (e.g., reduction in survivorship, feeding inhibition, paralysis), chronic effects (e.g., reduction in growth and fecundity), biochemical alterations (e.g., activity of phosphatases, GST, AChE, proteases), and behavioral alterations. Research has also focused on the potential for bioaccumulation and transferring of these toxins through the food chain. Although the herbivorous zooplankton is hypothesized as the main target of cyanotoxins, there is not unquestionable evidence of the deleterious effects of cyanobacteria and their toxins on these organisms. Also, the low toxin burden in secondary consumers points towards biodilution of microcystins in the food web as the predominant process. In this broad review we discuss important issues on bioaccumulation and the effects of cyanotoxins, with emphasis on microcystins, as well as drawbacks and future needs in this field of research.

Daphnia response to biotic stress is modified by PCBs.

The aim of this study was to examine the influence of xenobiotics (PCBs) on the responses of Daphnia to biotic factors such as the presence of a predator (fish kairomone) or filamentous cyanobacteria. Both behaviour (depth selection) and life history (body size at first reproduction and fecundity) were affected by these stressors. Though there was no direct effect of PCBs, their influence resulted in disruption of the "natural" reaction to the presence of fish or cyanobacteria, leading to inadequate responses of Daphnia to these biotic threats. Examined clones of Daphnia showed significant diversity in their reaction to these stress factors, which was greater than that between Daphnia clones exposed to different environmental conditions. PCB pollution may change the frequency of Daphnia clones in favour of those whose responses to biotic stress are similar in both the absence and presence of these toxic chemicals.

Combined exposure of Japanese quails to cyanotoxins, Newcastle virus and lead: oxidative stress responses.

Wild birds are continually exposed to many anthropogenic and natural stressors in their habitats. Over the last decades, mass mortalities of wild birds constitute a serious problem and may possibly have more causations such as natural toxins including cyanotoxins, parasitic diseases, industrial chemicals and other anthropogenic contaminants. This study brings new knowledge on the effects of controlled exposure to multiple stressors in birds. The aim was to test the hypothesis that influence of cyanobacterial biomass, lead and antigenic load may combine to enhance the effects on birds, including modulation of antioxidative and detoxification responses. Eight treatment groups of model species Japanese quail (Coturnix coturnix japonica) were exposed to various combinations of these stressors. The parameters of detoxification and oxidative stress were studied in liver and heart after 30 days of exposure. The antioxidative enzymatic defense in birds seems to be activated quite efficiently, which was documented by the elevated levels and activities of antioxidative and detoxification compounds and by the low incidence of damage to lipid membranes. The greatest modulations of glutathione level and activities of glutathione-S-transferase, glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase and lipid peroxidation were shown mostly in the groups with combined multiple exposures. The results indicate that the antioxidative system plays an important role in the protective response of the tissues to applied stressors and that its greater induction helps to protect the birds from more serious damage. Most significant changes of these "defense" parameters in case of multiple stressors suggest activation of this universal mechanism in situation with complex exposure and its crucial role in protection of the bird health in the environment.

Genotoxicity of crude extracts of cyanobacteria from Taihu Lake on carp (Cyprinus carpio).

Genotoxicity of crude cyanobacteria extracts (CBE) from blooms in Taihu Lake, China toward common carp (Cyprinus carpio) was measured. The primary extracellular product was determined by HPLC to be Microcystin-LR (MC-LR, L for leucine and R for arginine) with an average concentration of 2.4 × 10(2) µg MC g(-1) dry weight of cyanobacteria. Acute toxicity to carp, expressed as the 72-h LC(50,) was 53 mg, dw cyanobacteria L(-1). Genotoxicity, as determined by the micronucleus (MN) and comet assays were both dose- and time-depended. Deformities of cellular organelles in liver and gill were observed by use of transmission electron microscopy (TEM). The results showed that MC-LR from cyanobacteria from Taihu Lake could induce genotoxic response and tissue-level morphological changes in common carp.

Toxicity of cyanobacterial bloom extracts from Taihu Lake on mouse, Mus musculus.

The acute and sub-chronic toxicities of cyanobacterial extract from Taihu Lake (PR China) on mouse (Mus musculus) were investigated in this study via intraperitoneal (i.p.) injection. Increases in liver/body weight ratios and pathological changes in mouse liver showed adverse effects at the organ level. Images from transmission electron microscopy (TEM) indicated that abnormal membrane structure occurred and that the organelles were damaged severely in the cells of liver and testis. The high dose group received i.p. injection of 12 mg lyophilized algae cells/kg body weight. Malondialdehyde (MDA) levels increased significantly in the livers of this group, along with a significant decrease in catalase (CAT) activity. These results revealed the existence of obvious oxidative stress. Comet assay results also suggested a dose-dependent relationship between DNA damage in hepatocytes/testicular cells and the amount of bloom extract administered to the mice. There was a significant increase in DNA damage compared to the control group and the genotoxicity of the cyanobacterial bloom to testicular cells was higher than in hepatocytes.

The effect of peroral administration of toxic cyanobacteria on laboratory rats (Rattus norvegicus var. alba).

OBJECTIVES: The toxic cyanobacteria are a serious problem for water supply systems, recreation, and agriculture. Cyanobacteria produce numerous bioactive compounds including microcystins - the most studied cyanobacterial hepatotoxins. Only rare studies addressed realistic situation, i.e. impact of MCs accumulated in the fish tissues on the overall physiology. The aim of the present study was to provide a model simulation of the simple food chain for evaluation of impacts of cyanobacteria on the rat physiology under different exposure scenario. METHODS: Experimental rats were fed with food with fish meat, which contained external additions of isolated microcystins as well as toxic cyanobacteria Microcystis, nontoxic cyanobacteria Arthrospira and green alga Chlorella. Subgroups of the animals were also challenged with a model antigen KLH to investigated immune-related parameters. We studied parameters of oxidative stress in the liver as levels of lipid peroxidation and glutathion levels. Series of hematological, biochemical and immunological parameters were also investigated. RESULTS: Although considerable amounts of microcystins were administered to rats, all levels of MCs were under the detection limit (1 ng/g fresh weight) in the rat tissues using tandem LC/MS. Only some conjugates of microcystins with cystein and glutathion were detected in the rat liver exposed to Microcystis biomass (values were around the detection limit). Statistically significant depletion of body and liver weight was observed in groups with microcystin addition in comparison with all other groups. Rats exposed to MCs had stimulated immune system (showed higher antibody answer on administered antigen). Also modulation of some lymphocyte subpopulations was recorded with the most interesting observation of stimulated NK cell numbers in groups exposed to isolated toxins (but not to biomass containing the same toxin amount). CONCLUSIONS: Our study demonstrates that oral exposure to microcystins in the diet may induce some detoxification responses and modulation of some hematological and immunological parameters.

Effects of microcystin and complex cyanobacterial samples on the growth and oxidative stress parameters in green alga Pseudokirchneriella subcapitata and comparison with the model oxidative stressor--herbicide paraquat.

Oxidative stress is one of the biochemical mechanisms involved in toxicity of cyanobacterial toxins microcystins (MC), but its role in the effects of complex water blooms is elusive. The aim of this study was to investigate effects of pure MCs and different complex mixtures of cyanobacterial metabolites on the growth and biochemical markers of oxidative stress and detoxification in green alga Pseudokirchneriella subcapitata. Pure MCs at high concentrations (300 µg/L) had no effects on the growth of P. subcapitata (up to 10 day exposures) but stimulated activity of glutathione reductase (GR) after short 3 and 24 h exposures. Other biomarkers (levels of glutathione, GSH, and activities of glutathione-S-transferase, GST, and glutathione peroxidase, GPx) were not affected by pure MCs). Crude extract of the laboratory culture of cyanobacteria Microcystis aeruginosa (containing 300 µg/L of MCs) had no effects on algal growth or any of the biomarkers. Weak growth stimulations after 4-7 days were observed after exposures to the growth-spent medium of the M. aeruginosa culture, which also inhibited activities of GST after prolonged exposures. Other investigated parameters (reduced GSH and activity of GPx) were not affected by any of the cyanobacterial samples. The results were compared with effects of model oxidative stressor herbicide paraquat, which exhibited variable effects on both algal growth and biomarkers (decrease in reduced GSH, stimulations of GR). Taken together, although pure MCs induce oxidative stress in green alga, the effects of cyanobacterial mixtures, which are more relevant to the natural situation, are more complex and they differ from the pure toxin. High variability in the biochemical responses to the oxidative stress makes the interpretation of results complicated, which limits the use of these biomarkers as early warnings of toxicity under natural conditions.

Are Bacterio- and Phytoplankton Community Compositions Related in Lakes Differing in Their Cyanobacteria Contribution and Physico-Chemical Properties?

Bacterioplankton community composition has become the center of research attention in recent years. Bacteria associated with toxic cyanobacteria blooms have attracted considerable interest. However, little is known about the environmental factors driving the bacteria community, including the impact of invasive cyanobacteria. Therefore, our aim has been to determine the relationships between heterotrophic bacteria and phytoplankton community composition across 24 Polish lakes with different contributions of cyanobacteria including the invasive species Raphidiopsis raciborskii. This analysis revealed that cyanobacteria were present in 16 lakes, while R. raciborskii occurred in 14 lakes. Our results show that bacteria communities differed between lakes dominated by cyanobacteria and lakes with minor contributions of cyanobacteria but did not differ between lakes with R. raciborskii and other lakes. Physical factors, including water and Secchi depth, were the major drivers of bacteria and phytoplankton community composition. However, in lakes dominated by cyanobacteria, bacterial community composition was also influenced by biotic factors such as the amount of R. raciborskii, chlorophyll-a and total phytoplankton biomass. Thus, our study provides novel evidence on the influence of environmental factors and R. raciborskii on lake bacteria communities.

Reversed evolution of grazer resistance to cyanobacteria.

Exploring the capability of organisms to cope with human-caused environmental change is crucial for assessing the risk of extinction and biodiversity loss. We study the consequences of changing nutrient pollution for the freshwater keystone grazer, Daphnia, in a large lake with a well-documented history of eutrophication and oligotrophication. Experiments using decades-old genotypes resurrected from the sediment egg bank revealed that nutrient enrichment in the middle of the 20th century, resulting in the proliferation of harmful cyanobacteria, led to the rapid evolution of grazer resistance to cyanobacteria. We show here that the subsequent reduction in nutrient input, accompanied by a decrease in cyanobacteria, resulted in the re-emergence of highly susceptible Daphnia genotypes. Expression and subsequent loss of grazer resistance occurred at high evolutionary rates, suggesting opposing selection and that maintaining resistance was costly. We provide a rare example of reversed evolution of a fitness-relevant trait in response to relaxed selection.

Vulnerability of Quebec drinking-water treatment plants to cyanotoxins in a climate change context.

Cyanobacteria are a growing concern in the province of Quebec due to recent highly publicised bloom episodes. The health risk associated with the consumption of drinking water coming from contaminated sources was unknown. A study was undertaken to evaluate treatment plants' capacity to treat cyanotoxins below the maximum recommended concentrations of 1.5 microg/L microcystin-LR (MC-LR) and the provisional concentration of 3.7 microg/L anatoxin-a, respectively. The results showed that close to 80% of the water treatment plants are presently able to treat the maximum historical concentration measured in Quebec (5.35 microg/L MC-LR equ.). An increase, due to climate change or other factors, would not represent a serious threat because chlorine, the most popular disinfectant, is effective in treating MC-LR under standard disinfection conditions. The highest concentration of anatoxin-a (2.3 microg/L) measured in natural water thus far in source water is below the current guideline for treated waters. However, higher concentrations of anatoxin-a would represent a significant challenge for the water industry as chlorine is not an efficient treatment option. The use of ozone, potassium permanganate or powder activated carbon would have to be considered.

Toxicity of cyanobacterial bloom in the eutrophic dam reservoir (Southeast Poland).

Cyanobacterial bloom was observed in a highly eutrophic dam reservoir, Zemborzycki, near Lublin (SE Poland) over a warm period in the year 2007. The water bloom consisted of several cyanobacterial taxa: Anabaena circinalis, Anabaena spiroides, Anabaena flos-aquae, Planktothrix agardhii, Aphanizomenon flos-aquae, Aphanizomenon gracile, and Microcystis flos-aquae. Anabaena spp., and Aphanizomenon spp., potential producers of neurotoxic anatoxin-a, quantitatively predominated in the studied bloom. High-performance liquid chromatography (HPLC) analysis of surface scum sampled during Anabaena circinalis domination revealed the presence of anatoxin-a at a high concentration (1,035.59 microg per liter of surface scum). At the same time, neither gas chromatography/mass spectrometry (GC/MS) nor microcystin enzyme-linked immunosorbent assay (ELISA) test showed the presence of other frequently found cyanotoxins, microcystins. Toxicity of cyanobacterial bloom was assessed by the crustacean acute toxicity test Daphtoxkit F pulex using Daphnia pulex, and by the chronic toxicity test Protoxkit F with a ciliate protozoan Tetrahymena thermophila. The crude extract of cyanobacterial scum showed high toxicity for Daphnia pulex, with 24-h median effective concentration (EC50) value of 90.3 microg/L of anatoxin-a, which corresponded to the cyanobacterial density in the scum of 1.01 g dry weight/L. For Tetrahymena thermophila, 24-h EC50 was lower, evaluated to be 60.48 microg/L of anatoxin-a, which corresponded to a cyanobacterial density of 0.68 g dry weight/L of the scum. On the basis of evaluated toxicity units, the cyanobacterial extract was classified at class IV toxicity, which means high toxic hazard.

Invasion of toxic marine cyanobacteria in to the tsunami affected coastal villages of southern India.

This documentation explores the facts about the invasion of marine cyanobacteria in to the tsunami affected coastal villages of Nagapattinam district of Tamilnadu and Karaikkal district of Pondicherry Union Territory (UT) in southern India. Water samples were collected from eight tsunami-hit coastal villages in different open water sources. The collected samples were processed for detecting marine cyanobacterial growth. Totally 110 water samples were processed, three samples were positive for the toxic cyanobacteria, Lyngbya sp., and nine for nontoxic species such as Epithemia sp.,, Johannesbaptistia pellucida, Oscillatoria princeps, Phormidium fragile, Synechocystis sp. Besides posing a public health risk because of the toxic cyanobacteria, the bloom formation by the cyanobacterial species such as Anabaena, Microcystis, Lyngbya, Plectonema, Phormidium contaminated the water bodies and deteriorated the water quality in the tsunami affected villages. The study revealed that another kind of public health risk from the invasion of toxic cyanobacteria to the costal ecosystem during the tsunami. It is necessary, in this context, that the surveillance mechanism, which is geared up during or after natural disasters, should have a provision to monitor the transportation of toxic elements/organisms from marine system to coastal/inland ecosystems and to control such organisms.