Occurrence of potentially toxic cyanobacteria Microcystis aeruginosa in aquatic ecosystems of central Kerala (south India)

Microcystis aeruginosa is a potentially toxic bloom-forming freshwater cyanobacterium, usually found in eutrophic water bodies worldwide. The present study reports the occurrence of Microcystis aeruginosa and its bloom in freshwater ponds along central Kerala (south India). Monitoring of cyanobacterial blooms was conducted from May 2019 to February 2020 along the aquatic ecosystems of central Kerala and the M. aeruginosa blooms were recorded from two freshwater ponds of Kochi. Massive blooms of M. aeruginosa was observed during the period prior to summer monsoon (May) with an abundance of 1.17 × 106 cells L‑1 (Station 1) and during early summer (February) latter being more thick scum (2 × 108 cells L‑1) with high chlorophyll a. Dense aggregates of M. aeruginosa scums were more prevalent during the periods characterised by higher Surface Water Temperature (SWT). The nutrient characteristic pattern of the study area showed the abundance of M. aeruginosa correlated very well with higher dissolved nitrate (96.7 μmol L‑1) and phosphate (19.88 μmol L‑1) concentrations. Thus in the stable freshwater ponds with higher SWT and nutrients were the major factors influencing the growth and abundance of the cyanobacteria M. aeruginosa. Toxicological studies conducted revealed that the Microcystis bloom was hepatotoxic, inflicting fish mortality.

Download Full-text

Grazing of the copepod Cyclops vicinus on toxic Microcystis aeruginosa: potential for controlling cyanobacterial blooms and transfer of toxins

Oceanological and Hydrobiological Studies ◽

10.1515/ohs-2018-0028 ◽

2018 ◽

Vol 47 (3) ◽

pp. 296-302 ◽

Cited By ~ 5

Author(s):

Zakaria A. Mohamed ◽

Asmaa A. Bakr ◽

Hamed A. Ghramh

Keyword(s):

Microcystis Aeruginosa ◽

Grazing Rate ◽

Cyanobacterial Blooms ◽

Feeding Experiments ◽

Cyclops Vicinus ◽

Ankistrodesmus Falcatus ◽

Toxic Cyanobacteria ◽

Study Laboratory ◽

Grazer Species

Abstract Grazing of zooplankton on phytoplankton may contribute to a reduction of harmful cyanobacteria in eutrophic waters. However, the feeding capacity and interaction between zooplankton and toxic cyanobacteria vary among grazer species. In this study, laboratory feeding experiments were designed to measure the grazing rate of the copepod Cyclops vicinus on Microcystis aeruginosa and the potential microcystin (MC) accumulation in the grazer. Copepods were fed a mixed diet of the edible green alga Ankistrodesmus falcatus and toxic M. aeruginosa for 10 days. The results showed that C. vicinus efficiently ingested toxic Microcystis cells with high grazing rates, varying during the feeding period (68.9–606.3 Microcystis cells animal-1 d-1) along with Microcystis cell density. Microcystis cells exhibited a remarkable induction in MC production under grazing conditions with concentrations 1.67–12.5 times higher than those in control cultures. Furthermore, C. vicinus was found to accumulate MCs in its body with concentrations increasing during the experiment (0.05–3.21 μg MC animal-1). Further in situ studies are needed to investigate the ability of Cyclops and other copepods to assimilate and detoxify MCs at environmentally relevant concentrations before deciding on the biocontrol of Microcystis blooms by copepods.

Download Full-text

Phenological and Liver Antioxidant Profiles of Adult Nile Tilapia (Oreochromis niloticus) Exposed to Toxic Live Cyanobacterium (Microcystis aeruginosa Kceützing) Cells

Zeitschrift für Naturforschung C ◽

10.1515/znc-2012-11-1213 ◽

2012 ◽

Vol 67 (11-12) ◽

pp. 620-628 ◽

Cited By ~ 1

Author(s):

Hanan M. Khairy ◽

Marwa A. Ibrahim ◽

Mai D. Ibrahem

Keyword(s):

Microcystis Aeruginosa ◽

Oreochromis Niloticus ◽

Nile Tilapia ◽

Economic Problem ◽

Cyanobacterial Blooms ◽

Fish Mortality ◽

Blue Green Algae ◽

Progressive Development ◽

Cyanobacterial Species ◽

Nile Tilapia Oreochromis Niloticus

Blue-green algae (cyanobacteria) constitute the greater part of the phytoplankton. Microcystis aeruginosa is amongst the most ubiquitously distributed cyanobacterial species, and almost invariably produces cyclic heptapeptide toxins called microcystins (MCs). The present study was designed to investigate the phenological and liver antioxidant profiles of the Nile tilapia Oreochromis niloticus chronically exposed to toxic live M. aeruginosa cells. Fish were grown in the absence and presence of M. aeruginosa in three different concentrations for seven days, and subsequently reared for another 30 days in the absence of the cyanobacteria. While cyanobacteria did not cause any fish mortality, there was a progressive development of yellowish discolouration in the livers of exposed fish. In the livers, the activities and levels of superoxide dismutase (SOD), lactate dehydrogenase (LDH), glutathione (GSH), and lipid peroxidation products like malondialdehyde (MDA) were elevated in response to the concentration of M. aeruginosa. Moreover, DNA fragmentation and DNA-protein crosslinks were measured. These parameters can thus be considered potential biomarkers for the fish exposure to M. aeruginosa. The present study sheds light on cyanobacterial blooms like health, environmental, and economic problem, respectively.

Download Full-text

Physiological and Metabolic Responses of Marine Mussels Exposed to Toxic Cyanobacteria Microcystis aeruginosa and Chrysosporum ovalisporum

Toxins ◽

10.3390/toxins12030196 ◽

2020 ◽

Vol 12 (3) ◽

pp. 196 ◽

Cited By ~ 1

Author(s):

Flavio Oliveira ◽

Leticia Diez-Quijada ◽

Maria V. Turkina ◽

João Morais ◽

Aldo Barreiro Felpeto ◽

...

Keyword(s):

Microcystis Aeruginosa ◽

Dry Weight ◽

Cyanobacterial Blooms ◽

Control Group ◽

Freshwater Bivalve ◽

Marine Mussel ◽

Toxic Cyanobacteria ◽

Parachlorella Kessleri ◽

Marine Mussels ◽

Exposure Experiment

Toxic cyanobacterial blooms are a major contaminant in inland aquatic ecosystems. Furthermore, toxic blooms are carried downstream by rivers and waterways to estuarine and coastal ecosystems. Concerning marine and estuarine animal species, very little is known about how these species are affected by the exposure to freshwater cyanobacteria and cyanotoxins. So far, most of the knowledge has been gathered from freshwater bivalve molluscs. This work aimed to infer the sensitivity of the marine mussel Mytilus galloprovincialis to single as well as mixed toxic cyanobacterial cultures and the underlying molecular responses mediated by toxic cyanobacteria. For this purpose, a mussel exposure experiment was outlined with two toxic cyanobacteria species, Microcystis aeruginosa and Chrysosporum ovalisporum at 1 × 105 cells/mL, resembling a natural cyanobacteria bloom. The estimated amount of toxins produced by M. aeruginosa and C. ovalisporum were respectively 0.023 pg/cell of microcystin-LR (MC-LR) and 7.854 pg/cell of cylindrospermopsin (CYN). After 15 days of exposure to single and mixed cyanobacteria, a depuration phase followed, during which mussels were fed only non-toxic microalga Parachlorella kessleri. The results showed that the marine mussel is able to filter toxic cyanobacteria at a rate equal or higher than the non-toxic microalga P. kessleri. Filtration rates observed after 15 days of feeding toxic microalgae were 1773.04 mL/ind.h (for M. aeruginosa), 2151.83 mL/ind.h (for C. ovalisporum), 1673.29 mL/ind.h (for the mixture of the 2 cyanobacteria) and 2539.25 mL/ind.h (for the non-toxic P. kessleri). Filtering toxic microalgae in combination resulted in the accumulation of 14.17 ng/g dw MC-LR and 92.08 ng/g dw CYN. Other physiological and biochemical endpoints (dry weight, byssus production, total protein and glycogen) measured in this work did not change significantly in the groups exposed to toxic cyanobacteria with regard to control group, suggesting that mussels were not affected with the toxic microalgae. Nevertheless, proteomics revealed changes in metabolism of mussels related to diet, specially evident in those fed on combined cyanobacteria. Changes in metabolic pathways related with protein folding and stabilization, cytoskeleton structure, and gene transcription/translation were observed after exposure and feeding toxic cyanobacteria. These changes occur in vital metabolic processes and may contribute to protect mussels from toxic effects of the toxins MC-LR and CYN.

Download Full-text

Chemical Characterization of Microcystis aeruginosa for Feed and Energy Uses

Energies ◽

10.3390/en14113013 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3013

Author(s):

Larissa Souza Passos ◽

Éryka Costa Almeida ◽

Claudio Martin Pereira de Pereira ◽

Alessandro Alberto Casazza ◽

Attilio Converti ◽

...

Keyword(s):

Microcystis Aeruginosa ◽

Animal Feed ◽

Renewable Energy Sources ◽

Chemical Characterization ◽

Cyanobacterial Blooms ◽

Energy Sources ◽

Carbohydrate Source ◽

Heating Value ◽

Adverse Health Effects ◽

Degradation Reactions

Cyanobacterial blooms and strains absorb carbon dioxide, drawing attention to its use as feed for animals and renewable energy sources. However, cyanobacteria can produce toxins and have a low heating value. Herein, we studied a cyanobacterial strain harvested during a bloom event and analyzed it to use as animal feed and a source of energy supply. The thermal properties and the contents of total nitrogen, protein, carbohydrate, fatty acids, lipid, and the presence of cyanotoxins were investigated in the Microcystis aeruginosa LTPNA 01 strain and in a bloom material. Microcystins (hepatotoxins) were not detected in this strain nor in the bloom material by liquid chromatography coupled to mass spectrometry. Thermogravimetric analysis showed that degradation reactions (devolatilization) initiated at around 180 °C, dropping from approximately 90% to 20% of the samples’ mass. Our work showed that despite presenting a low heating value, both biomass and non-toxic M. aeruginosa LTPNA 01 could be used as energy sources either by burning or producing biofuels. Both can be considered a protein and carbohydrate source similar to some microalgae species as well as biomass fuel. It could also be used as additive for animal feed; however, its safety and potential adverse health effects should be further investigated.

Download Full-text

Evidence of Quorum Sensing in Cyanobacteria by Homoserine Lactones: The Origin of Blooms

Water ◽

10.3390/w13131831 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1831

Author(s):

Natalia Herrera ◽

Fernando Echeverri

Keyword(s):

Cell Proliferation ◽

Quorum Sensing ◽

Microcystis Aeruginosa ◽

Industrial Effluents ◽

Cyanobacterial Blooms ◽

Cylindrospermopsis Raciborskii ◽

Bacterial Communication ◽

Homoserine Lactones ◽

Exogenous Compounds ◽

Almost All

Although several theories have been postulated to explain cyanobacterial blooms, their biochemical origin has not yet been found. In this work, we explore the existence of bacterial communication, called quorum sensing, in Microcystis aeruginosa and Cylindrospermopsis raciborskii. Thus, the application of several known acylhomoserine lactones to cultures of both cyanobacteria causes profound metabolic. At 72 h post-application, some of them produced substantial increases in cell proliferation, while others were inhibitors. There was a correlation with colony-forming activity for most of them. According to ELISA analysis, the microcystin levels were increased with some lactones. However, there was a clear difference between M. aeruginosa and C. raciborskii culture since, in the first one, there was an inducing effect on cell proliferation, while in C. raciborskii, the effects were minor. Besides, there were compound inhibitors and inducers of microcystins production in M. aeruginosa, but almost all compounds were only inducers of saxitoxin production in C. raciborskii. Moreover, each lactone appears to be involved in a specific quorum sensing process. From these results, the formation of cyanobacterial blooms in dams and reservoirs could be explained since lactones may come from cyanobacteria and other sources as bacterial microflora-associated or exogenous compounds structurally unrelated to lactones, such as drugs, industrial effluents, and agrochemicals.

Download Full-text

Effects of Malachite Green on the Microbiomes of Milkfish Culture Ponds

Water ◽

10.3390/w13040411 ◽

2021 ◽

Vol 13 (4) ◽

pp. 411

Author(s):

Chu-Wen Yang ◽

Yi-Tang Chang ◽

Chi-Yen Hsieh ◽

Bea-Ven Chang

Keyword(s):

Infectious Diseases ◽

Microbial Communities ◽

Malachite Green ◽

Fish Farming ◽

Cyanobacterial Blooms ◽

Anoxygenic Phototrophic Bacteria ◽

Fish Mortality ◽

Veterinary Drug ◽

Degrading Bacteria ◽

Microbial Infections

Intensive fish farming through aquaculture is vulnerable to infectious diseases that can increase fish mortality and damage the productivity of aquaculture farms. To prevent infectious diseases, malachite green (MG) has been applied as a veterinary drug for various microbial infections in aquaculture settings worldwide. However, little is known regarding the consequences of MG and MG-degrading bacteria (MGDB) on microbial communities in milkfish culture ponds (MCPs). In this study, small MCPs were used as a model system to determine the effects of MG on the microbial communities in MCPs. The addition of MG led to cyanobacterial blooms in the small MCP. The addition of MGDB could not completely reverse the effects of MG on microbial communities. Cyanobacterial blooms were not prevented. Microbial communities analyzed by next generation sequencing revealed that cyanobacterial blooms may be due to increase of nitrogen cycle (including nitrogen fixation, nitrate reduction and anammox) associated microbial communities, which raised the levels of ammonium in the water of the small MCP. The communities of anoxygenic phototrophic bacteria (beneficial for aquaculture and aquatic ecosystems) decreased after the addition of MG. The results of this investigation provide valuable insights into the effects of MG in aquaculture and the difficulties of bioremediation for aquatic environments polluted by MG.

Download Full-text

Harmful phytoplankton blooms and fish mortality in a eutrophicated reservoir of northeast Brazil

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132008000400022 ◽

2008 ◽

Vol 51 (4) ◽

pp. 633-641 ◽

Cited By ~ 23

Author(s):

Naithirithi Tiruvenkatachary Chellappa ◽

Sarah Laxhmi Chellappa ◽

Sathyabama Chellappa

Keyword(s):

Cyanobacterial Bloom ◽

Hplc Method ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Fish Mortality ◽

Cylindrospermopsis Raciborskii ◽

Northeast Brazil ◽

Cyanobacterial Toxin ◽

Bloom Formation ◽

Harmful Effects

The aim of this work was to study the eutrophication in the tropical freshwater ecosystems and the consequent cyanobacterial bloom formation and economical damage to fisheries and harmful effects to public health. Mass fish mortality due to toxin producing cyanobacterial blooms was registered during December 2003 in Marechal Dutra Reservoir, Acari/RN, Northeast Brazil. Phytoplankton and fish samplings were carried out on alternate days during the episode of fish mortality and monthly during January to June 2004. The cyanobacterial toxin was identified and quantified from the seston samples and liver of the dead fishes using the standard HPLC method. The results indicated that the toxic blooms of Cylindrospermopsis raciborskii and Microcystis aeruginosa were persistent for two weeks and represented 90% of the phytoplankton species assemblages. The lethally affected fishes were Oreochromis niloticus, Plagioscion squamosissimus, Cichla monoculus, Prochilodus brevis, Hoplias malabaricus and Leporinus friderici. The microcystin levels varied from 0.07 to 8.73µg L-1 the seston samples and from 0.01 to 2.59µg g-1in the liver samples of the fishes during the bloom period.

Download Full-text

Heavy-metal pollution alters dissolved organic matter released by bloom-forming Microcystis aeruginosa

RSC Advances ◽

10.1039/c7ra00414a ◽

2017 ◽

Vol 7 (30) ◽

pp. 18421-18427 ◽

Cited By ~ 4

Author(s):

Haiming Wu ◽

Li Lin ◽

Guangzhu Shen ◽

Ming Li

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Microcystis Aeruginosa ◽

Metal Pollution ◽

Heavy Metal Pollution ◽

Aquatic Ecosystems ◽

Eutrophic Lakes

The risk of heavy metals to aquatic ecosystems was paid much attention in recent years, however, the knowledge on effects of heavy metals on dissolved organic matter (DOM) released byMicrocystiswas quite poor, especially in eutrophic lakes.

Download Full-text

Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>Microcystis aeruginosa</i>

Biogeosciences ◽

10.5194/bg-10-8139-2013 ◽

2013 ◽

Vol 10 (12) ◽

pp. 8139-8157 ◽

Cited By ~ 13

Author(s):

M. W. Matthews ◽

S. Bernard

Keyword(s):

Optical Properties ◽

Microcystis Aeruginosa ◽

Cyanobacterial Blooms ◽

Shell Layer ◽

Sphere Model ◽

Homogeneous Population ◽

Chl A ◽

Inherent Optical Properties ◽

Gas Vacuoles ◽

The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole-like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. Measured Rrs was used to provide a range of values for the central value of the real refractive index, 1 + ε, for the shell layer using measured IOPs and a radiative transfer model. Sufficient optical closure was obtained for 1 + ε between 1.1 and 1.14, which had corresponding Chl a-specific phytoplankton backscattering, bbφ*, between 3.9 and 7.2 × 10−3 m2 mg−1 at 510 nm. The bbφ* values are in close agreement with the literature and in situ particulate backscattering measurements. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. A sensitivity analysis of empirical algorithms for estimating Chl a in eutrophic/hypertrophic waters suggests these are robust under variable constituent concentrations and likely to be species-sensitive. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

Download Full-text