Non-toxic algal bloom responsible for ‘green tide’ phenomenon

By Conrad Prabhu — MUSCAT: Feb 25 – Sightings of discoloured swathes of seawater along parts of Muscat’s coastline line last week have been attributed to an outbreak of a non-toxic species of algal bloom that is quite common around this time of year. The species in question is Noctiluca Scintillans, a large, green dinoflagellate phytoplankton that is common in the waters of the Arabian Sea, according to a marine biologist of Sultan Qaboos University (SQU). “Satellite images appear to show a fairly widespread outbreak of this algal bloom along the Sea of Oman and the wider Arabian Sea,” the expert said. “Outbreaks occur when environmental conditions in these waters, coupled with nutrient levels, reach optimum levels,” he added in comments to Observer.
Last week, swimmers and beach strollers stumbled upon waves of green-hued seawater lapping on Muscat’s shores, notably at Bausher and Qurum.  While some, unfazed by this discolouration, enjoyed a dip in these waters, others kept a safe distance. However, this ‘green tide’ phenomenon appears to have receded by the weekend.
Noctiluca Scintillans do not typically fall in the category of Harmful Algal Blooms (HAB) because they do not release toxic chemicals of the kind associated with their peers, notably cyanobacteria (blue green algae), raphidophycean algean, and so on.
These chemicals are harmful primarily to fish and other aquatic animals, resulting in fish kills, and so on.  However, the consequences for human health are not of a serious nature, save for skin allergies, irritation and discomfort.
But, according to the SQU marine biologist, even the non-toxic Noctiluca Scintillans species blamed for last week’s algal outbreak can be source of concern in cirtain circumstances.  “It all depends on their abundance, the presence of other species in the same water, and if the swimmers have existing health issues. So it’s prudent to take precautions at all times,” he said.
Algal blooms are not new to Oman. According to marine scientists, the Sea of Oman hosts a variety of indigenous species of marine algae that see a sudden explosion in their populations when conditions are conducive for such growth.
Such blooms have long been a natural occurrence along the coasts of the Sea of Oman, Arabian Gulf and the Arabian Sea.
However, with the proliferation of seawater desalination projects all along the coastline, algal blooms pose a significant threat to the safe operation of these plants.
Harmful algal blooms (HABs) are known to cause significant operational difficulties in the form of increase membrane fouling, higher chemical consumption rates, and so on.