Marine / Unusual algal bloom unlikely to be harmful, UHI principal says
THERE is unlikely to be a negative impact if the large algal bloom photographed by NASA in the waters to the southeast of the isles ever reach Shetland’s coastline.
While there are some 200 species of harmful algae that produce toxins of various sorts that might affect aquaculture, the algae that is likely to have turned the sea into a striking turquoise – the coccolithophore Gephrocapsa huxleyi – is not one of them.
UHI Shetland principal Professor Jane Lewis, who is a marine phycologist (an algae specialist) said hydrographic condition out at sea may have been similar to those in 2021 when a similar phytoplankton bloom was visible along the east coast of the isles.
That bloom is thought to have started at the Continental shelf edge to the north and then moved to Shetland in the current and easterly winds.
The current bloom will have started in similar conditions – a source of original population, nutrients and sun light, as well as hydrographic conditions that prevents the bloom to be dispersed by sea conditions.
Nasa’s Earth Observatory published a photo of the 100 miles wide algal bloom on its website at the weekend.
Dr Lewis said the phenomenon is not “necessarily linked to rising sea temperatures”.
She said it was likely that the bloom would disperse naturally, though how that would happen is less clear.
“It could be by a mixing event (storms or similar), grazing or viral removal of the bloom, life cycle events of the phytoplankton composing the bloom, lack of nutrients leading to bloom decay,” she said.
Depending on the way the bloom decays this could lead “to stripping of oxygen from the water column or sediments”, she said, which could then suffocate other marine organisms and lead to die off events.
She added: “I should also point out that phytoplankton provide around half the oxygen on the planet and coccolithophores are a carbon sink – locking away carbon dioxide in their skeletons – so not all bad.”
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