Complexities blight algal bloom toxin monitoring

A recent report by government scientists has pointed to a conundrum in World Health Organisation (WHO) guidelines for water companies looking to test drinking water for toxins released by algal blooms in water bodies that feed water treatment plants.

The WHO guidance directs water companies to monitor cyanotoxin released by the cyanobacteria that create algal blooms “in the event of potential blooms.” However, according to the UK Food and Environment Research Agency (Fera) there is no definition for an algal bloom.

Other observations in the Drinking Water Inspectorate-commissioned report, Cyanotoxins in raw surface waters, included one taken from a literature review that covered accounts of the relationship between the number of cyanobacteria and the concentration of cyanotoxins. Fera found that “the single consistent theme was the variability, between sites and even within a single site but between years.”

Fera found also: “There is consistent evidence that there is a very poor relationship between the presence of cyanobacteria and the concentration of cyanotoxins. There is relatively little information on the fate of cyanotoxins once they are in the water column and/or sediment.”

Fera reported that the observations in the literature “largely focussed” on one group of cyanotoxin – microcystins – with “relatively little data” on others. Fera said its findings identified that microcystins were detected in raw water with other related compounds sometimes in higher concentrations, which raises the question of whether the current threshold of 1.0 μg/L for one specific microcystin (MC-LR) “should in fact be total microcystins – something that is currently under consideration within WHO”.