Cyanobacterial Abundance and Microcystin Profiles in Two Southern British Lakes: The Importance of Abiotic and Biotic Interactions

Abstract

Freshwater cyanobacteria blooms represent a risk to ecological and human health through induction of anoxia and release of potent toxins; both conditions require water management to mitigate risks. Many cyanobacteria taxa may produce microcystins, a group of toxic cyclic heptapeptides. Understanding the relationships between the abiotic drivers of microcystins and their occurrence would assist in the implementation of targeted, cost-effective solutions to maintain safe drinking and recreational waters. Cyanobacteria and microcystins were measured by flow cytometry and liquid chromatography coupled to tandem mass spectrometry in two interconnected reservoirs varying in age and management regimes, in southern Britain over a 12-month period. Microcystins were detected in both reservoirs, with significantly higher concentrations in the southern lake (maximum concentration >7 µg L−1). Elevated microcystin concentrations were not positively correlated with numbers of cyanobacterial cells, but multiple linear regression analysis suggested temperature and dissolved oxygen explained a significant amount of the variability in microcystin across both reservoirs. The presence of a managed fishery in one lake was associated with decreased microcystin levels, suggestive of top down control on cyanobacterial populations. This study supports the need to develop inclusive, multifactor holistic water management strategies to control cyanobacterial risks in freshwater bodies.

Protective Role of Native Rhizospheric Soil Microbiota Against the Exposure to Microcystins Introduced into Soil-Plant System via Contaminated Irrigation Water and Health Risk Assessment

“…MCs are hepatotoxic cyclic heptapeptides produced by several bloom-forming cyanobacteria belonging to several genera such as Microcystis , Nostoc , Oscillatoria , Planktothrix and Dolichospermum [ 8 , 9 , 10 , 11 , 12 , 13 ]. Owing to their ring structure, MCs are chemically stable under several field and laboratory conditions with half-life ranging from 0.4 to 22 days [ 14 , 15 , 16 , 17 , 18 , 19 ] and total concentrations varying from less than 1 µg·L −1 to 29,000 µg·L −1 in surface waters [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Dissolved MCs in water bodies are recognized as a major public health hazard and disrupting agents of certain fundamental ecological processes [ 31 , 32 , 33 ].…”

Cyanobacteria and their secondary metabolites in three freshwater reservoirs in the United Kingdom

“…Microcystins and anatoxin-a have been regularly reported in European waters with concentrations up to 100 and 14.4 µg/L, respectively, during seasonal studies in the recent years (e.g., Italy, Poland, Czech Republic, Germany, Russia, France, and Netherlands [16] and references herein). Many freshwater bodies in the United Kingdom (U.K.) frequently experience cyanobacterial blooms and high microcystin concentrations [17,18]. One study reported that 53% of 117 samples from cyanobacterial blooms reached microcystin concentrations above 0.2 µg/L and 13% of samples exceeded the WHO alert level of 20 µg/L [19].…”

Co-occurrence of microcystin and cylindrospermopsin in hypereutrophic Mahakanadarawa and Nachchaduwa reservoirs

“…Moreover, according to our data, water temperature within the reservoir in a single day showed a positive correlation with MC and CYN concentrations probably due to the spatial and diurnal variation in temperature where warmer areas accumulated more toxins. The DO is considered as a potential indicator for the onset of cyanotoxins derived from lysed cells in a blooming population (Hartnell et al 2020). However, DO of both Mahakanadarawa and Nachchaduwa reservoirs did not show a significant correlation to either MC or CYN.…”