Arsenic Accumulation and Biotransformation Affected by Nutrients (N and P) in Common Blooming-Forming Microcystis wesenbergii (Komárek) Komárek ex Komárek (Cyanobacteria)

Arsenic accumulation and biotransformation in algae was mostly carried out in a medium that contained far higher nutrient concentrations than that in natural freshwaters. The obtained results might have limited environmental validity and result in a failure to describe authentic arsenic biogeochemical cycles in natural freshwater systems. To validate the assumption, arsenic accumulation, and biotransformation in common bloom forming Microcystis wesenbergii was performed under a high nutrient concentration in BG11 medium (N = 250 mg/L, P = 7.13 mg/L), and adjusted low nutrients that mimicked values in natural freshwaters (N = 1.5 mg/L, P = 0.3 mg/L). The growth rate and maximum M. wesenbergii cell density were much lower in the high nutrient set, but more inhibition was shown with increasing ambient iAs(V) concentrations both in the high and low nutrient sets. The proportion of intracellular contents in total arsenicals decreased with increasing iAs(V) concentrations in both high and low nutrient sets but increased with incubation time. Intracellular iAs(III) was not found in the high nutrient set, while it formed high concentrations that could be comparable to that of an extracellular level in the low nutrient set. M. wesenbergii could methylate arsenic, and a higher proportion of organoarsenicals was formed in the low nutrient set. Lower intracellular MMA(V) and DMA(V) concentrations were found in the high nutrient set; contrarily, they presented a higher concentration that could be comparable to the extracellular ones in the low nutrient set. The results demonstrated that different nutrient regimes could affect arsenic accumulation and biotransformation in M. wesenbergii, and low nutrient concentrations could inhibit the excretion of iAs(III), MMA(V) and DMA(V) out of cells. Further investigations should be based on natural freshwater systems to obtain an authentic arsenic accumulation and biotransformation in cyanobacteria.

Cyanobacteria, cyanotoxins, and their histopathological effects on fish tissues in Fehérvárcsurgó reservoir, Hungary

Cyanobacteria are important members of lake plankton, but they have the ability to form blooms and produce cyanotoxins and thus cause a number of adverse effects. Freshwater ecosystems around the world have been investigated for the distribution of cyanobacteria and their toxins and the effects they have on the ecosystems. Similar research was performed on the Fehérvárcsurgó reservoir in Hungary during 2018. Cyanobacteria were present and blooming, and the highest abundance was recorded in July (2,822,000 cells/mL). The species present were Aphanizomenon flos-aquae, Microcystis flos-aquae, Microcystis wesenbergii, Cuspidothrix issatschenkoi, Dolichospermum flos-aquae, and Snowella litoralis. In July and September, the microcystin encoding gene mcyE and the saxitoxin encoding gene sxtG were amplified in the biomass samples. While a low concentration of microcystin-RR was found in one water sample from July, analyses of Abramis brama and Carassius gibelio caught from the reservoir did not show the presence of the investigated microcystins in the fish tissue. However, several histopathological changes, predominantly in gills and kidneys, were observed in the fish, and the damage was more severe during May and especially July, which coincides with the increase in cyanobacterial biomass during the summer months. Cyanobacteria may thus have adverse effects in this ecosystem.

Tracing the active genetic diversity of Microcystis and Microcystis phage through a temporal survey of Taihu

Harmful algal blooms are commonly thought to be dominated by a single genus, but they are not homogenous communities. Current approaches, both molecular and culture-based, often overlook fine-scale variations in community composition that can influence bloom dynamics. We combined homology-based searches (BLASTX) and phylogenetics to distinguish and quantify Microcystis host and phage members across a summer season during a 2014 Microcystis- dominated bloom that occurred in Lake Tai (Taihu), China. We found 47 different genotypes of the Microcystis-specific DNA-dependent RNA polymerase (rpoB), which included several morphospecies. Microcystis flos-aquae and Microcystis wesenbergii accounted for ~86% of total Microcystis transcripts, while the more commonly studied Microcystis aeruginosa only accounted for ~7%. Microcystis genotypes were classified into three temporal groups according to their expression patterns across the course of the bloom: early, constant and late. All Microcystis morphospecies were present in each group, indicating that expression patterns were likely dictated by competition driven by environmental factors, not phylogeny. We identified three primary Microcystis-infecting phages based on the viral terminase, including a novel Siphoviridae phage that may be capable of lysogeny. Within our dataset, Myoviridae phages consistent with those infecting Microcystis in a lytic manner were positively correlated to the early host genotypes, while the Siphoviridae phages were positively correlated to the late host genotypes, when the Myoviridae phages express putative genetic markers for lysogeny. The expression of genes in the microcystin-encoding mcy cassette was estimated using mcyA, which revealed 24 Microcystis-specific genotypes that were negatively correlated to the early host genotypes. Of all environmental factors measured, pH best described the temporal shift in the Microcystis community genotypic composition, promoting hypotheses regarding carbon concentration mechanisms and oxidative stress. Our work expounds on the complexity of HAB events, using a well-studied dataset to highlight the need for increased resolution of community dynamics.

Microcystis wesenbergii (Komárek) Komárek ex Komárek, 2006 (Cyanophyceae) – a new species for the Crimean coast of the Black Sea

The note describes a new species of toxic cyanobacteria Microcystis wesenbergii (Komárek) Komárek ex Komárek, 2006, which was discovered after the study of the periphyton community of synthetic polymeric materials during experimental vertical exposure of 45 samples of polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polypropylene (PP). The experimental vertical module was located in the water column of the Karantinnaya Bay of the Black Sea near Sevastopol (44°37′23.0″N, 33°29′38.5″E) from August to September 2018, when the water temperature varied from +22.4 to +26.6 °C and water salinity – from 17 to 18 ‰. Microcystis wesenbergii was found at a depth of 7.6 to 9.2 m on samples of HDPE, green PET, PP, and fragments of plastic containers for polymer samples. Microcystis wesenbergii is a polymorphic, planktonic species that occurs in small quantities in the water column of stagnant and slowly flowing eutrophic and mesotrophic freshwater reservoirs; it is toxic, sometimes forming blooms; cosmopolitan, except subpolar regions. The species was found in complex colonies consisting of subcolonies reaching a maximum length of 3700 μm; the diameter of young spherical colonies ranged from 240 to 367 μm. The diameter of M. wesenbergii cells was larger than the diagnosis [(10.19 ± 0.79) μm]; the color of the cells was predominantly light brown instead of blue-green. The discovery of toxic M. wesenbergii in the Karantinnaya Bay of the Black Sea indicates high latent diversity of cyanobacteria in this water area.

El género Sphaerocavum y dominancia de S. brasiliense y Microcystis wesenbergii (Microcystaceae, Cyanophyceae) en la floración algal de la laguna Huacachina, Perú

En el presente trabajo se registra por primera vez a las cianobacterias Sphaerocavum brasiliense Azevedo y Sant’Anna y Microcystis wesenbergii (Komárek) Komárek in Kondrateva (Microcystaceae, Cyanophyceae) en una floración algal de la laguna Huacachina (Ica), incluyendo el primer reporte del género Sphaerocavum para el Perú. Se sugiere el monitoreo de estas cianobacterias por ser formadoras de floraciones algales.