Determining the fate of Microcystis aeruginosa cells and microcystin toxins following chloramination

Abstract

The cyanobacterium Microcystis aeruginosa can produce potent toxins known as microcystins. While many studies have focussed on the chlorination of microcystin toxins, little work has been conducted with respect to the chloramination of the microcystins. In addition, no studies have been reported on the effect of chloramination on intact Microcystis cells. This study was conducted to determine the fate of M. aeruginosa cells and microcystin toxins following chloramination of a drinking water source. Results indicate that monochloramine could effectively oxidise dissolved microcystin-LR (MCLR) provided high CT values were employed, typically greater than 30,000 mg min L(-1). The decay of MCLR was demonstrated to be a pseudo first-order reaction with rate constants ranging from 9.3x10(-7) to 1.1x10(-5) s(-1) at pH 8.5. However, in the presence of Microcystis cells, monochloramine was ineffective in oxidising microcystin toxins due to the cells exerting a demand on the oxidant. The doses of monochloramine applied (2.8 and 3.5 mg L(-1)) were shown to rapidly release intracellular microcystins into the dissolved state. Flow cytometric analysis of the cells determined that the lower monochloramine dose did not compromise the cell membrane integrity, even though microcystins were rapidly released from the cells. In contrast the higher monochloramine dose resulted in cell membrane disruption with up to 90% of the cells shown to be non-viable after the high dose was applied.

Toxic and non-toxic strains of Microcystis aeruginosa induce temperature dependent allelopathy toward growth and photosynthesis of Chlorella vulgaris

“…However, their biomass can also be determined using indirect methods, the most common being Chla quantification (Lawton et al, 1999;Ho et al, 2010;Sun et al, 2012). Furthermore, Microcystis exists mainly as single cells during long-term storage and cultivation under laboratory conditions, while it commonly occurs as colonial aggregates constrained by an amorphous mucilage or sheath under natural conditions (Zhang et al, 2011;Wang et al, 2013).…”

Epipelic cyanobacterial diversity in Pinang River basin, Malaysia, revealed by 16S-based metagenomic approach

“…Ціанобактерії, або синьозелені водорості, є давньою групою мікроорганізмів, що виникла мільярди років тому і характеризується відносно багатим морфологічним різноманіттям (Dvořák et al, 2020). Це прокаріотичні фотосинтетичні автотрофи, отже їх відрізняють від еукаріотичних водоростей (Ho et al, 2010). Фотосинтетичні автотрофи є майже у всіх середовищах існування, куди доступне світло.…”

“…Ціанобактерії також можуть сприяти процесам вивітрювання гірських порід, таких як вапняки, прискорюючи деградацію їх поверхні (Sigler et al, 2003). Деякі ціанобактерії також здатні здійснювати фіксацію азоту (Ho et al, 2010). Відомі симбіотичні взаємовідносини між різними еукаріотичними організмами та ціанобактеріями, оскільки еукаріоти не здатні фіксувати азот (Krupke et al, 2014).…”

11 Control and management of harmful algal blooms

“…[ 93,106,[131][132][133][134][135][136][137][138][139][140][141][142] Coagulation and flocculation Efective techniques for the mitigation of both cyanobacteria and cyanotoxins must be determined by considering the underlying properties of the water system in question, including depth, pH values, concentrations of suspended solids, and dissolved organic and inorganic compounds [195,196]. To be successful, any mitigation approach must reduce both cyanobacteria and cyanotoxins and pose no or negligible threat to ecosystems.…”