Times of Malta

Green Balluta Bay water is ‘a red flag’

The murky green water that engulfed Balluta Bay over the weekend is a “red flag warning us that something unusual is happening”, according to marine biologist Alan Deidun, although the true cause of the phenomenon remains unclear.

Deidun was speaking to Times of Malta on Monday, a day after photos of the bay posted to social media caused widespread alarm.

Deidun said that the discoloura­tion is caused by an algal bloom, a phenomenon in which algae in the water grows rapidly and excessivel­y in a short span of time, becoming visible to the naked eye.

Studies suggest that the phenomenon is becoming increasing­ly common in the Mediterran­ean, with several reports of Alexandriu­m blooms, a type of phytoplank­ton that turns water into a green/yellow hue, recorded along Italy’s coast in recent years.

Similar discoloura­tion has happened before in Malta too, Deidun says, pointing to a 2017 incident in which the

Tas-Sukkursu canal dramatical­ly turned a deep shade of pink.

But, Deidun says, these algal blooms usually happen in late winter or early spring, not summer.

“It’s a little anomalous to have this in summer; it suggests that it could be driven by things that are not natural.”

Deidun says that algal blooms, such as the one that hit Balluta Bay, are often caused by specific environmen­tal conditions, such as high temperatur­es causing low oxygen levels in the water.

But, Deidun says, other factors, such as sewage contaminat­ion, could also play a part in accelerati­ng the growth of algae.

“Only extensive water testing can determine the cause of the algal bloom but it could well be a combinatio­n of factors,” he said.

The bay has been closed throughout the summer after two instances of E.coli contaminat­ion were detected. E.coli is commonly attributab­le to untreated sewage but the Water Services Corporatio­n has insisted that the contaminat­ion is “not from the sewage system”.

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Deidun says he recently noticed a similar, albeit less intense, case of an algal bloom at Golden Bay.

These sort of algal blooms are “usually very shortlived”, Deidun says, with the sea returning to its natural hue within a matter of days.

But, he is quick to add, “this really depends on the cause of the bloom”. If, for instance, a sewage runoff isn’t addressed, the same phenomenon could rear its head again.

The algal bloom itself, although unpleasant to bathers, is unlikely to be toxic, Deidun says. “These sort of blooms can be toxic in extreme cases but this isn’t usually the case in the Mediterran­ean,” he said.

In a brief statement on Sunday evening, the Environmen­t and Resources Authority said that it is investigat­ing the situation “in a number of bays around Malta” together with the Environmen­tal Health Directorat­e.

The authority said that “algal blooms may occur due to high temperatur­es and reduced water circulatio­n, conditions typical of heatwaves such as the one we are currently experienci­ng”.

Malta experience­d above-average temperatur­es over the weekend, which prompted the Met. Office to issue a yellow weather warning.

“It’s a little anomalous to have this in summer