By: M Najmuz Zafar

MUSCAT: The Ministry of Agriculture and Fisheries (MoAF) is monitoring spread of the red tide phenomenon since August 11 off the Muscat coast particularly near Al Bustan area.

While there is no immediate concern over marine life loss, the ministry represented by the Marine Sciences and Fisheries Centre (MSFC) has stated that the tide is likely to spread in the coming months.

Red tide, one of the harmful algal blooms (HABs), is a natural ecological phenomenon and affects marine resources. The continuous spread of green tide in Oman since 1976 has affected the marine environment and even led to the closure of desalination plants.

MSFC has been running the HAB monitoring programme for the past many years and has found that phytoplankton causing the current red tide is Akashiwo sanguinea type, which is rarely found in Omani waters.

The most common dinoflagellate Noctiluca scintillans is associated with the red tide events in Omani waters. Toxic species like Karenia selliformis, Prorocentrum arabianum and Trichodesmium erythraeum have also been reported in the recent past.

Dr Abdulaziz al Marzouqi, director, MSFC, told Muscat Daily that almost every year the red tide phenomenon is witnessed from September to March. “We are continuously monitoring the situation. Several field visits have helped us in sampling the planktons for scientific study, which include monitoring of temperature, salinity, oxygen and pH levels of water.”

He added that at the moment there have been no reports of fish mortality and it is not going to affect marine life in the short term. “As this is the time when the phenomenon begins, we have to wait and watch.”

Dr Marzouqi said although this type of plankton is not toxic, it sometimes leads to the death of marine organisms because of the resulting low percentage of dissolved oxygen in the water.

The occurrence of red tides has become more frequent in Omani waters in the recent years. Some of them caused fish kill, damaged fishery resources and mariculture, threatened the marine environment and the osmosis membranes of desalination plants. However, a number of them have been harmless.

A review of different HAB occurrences from 1976 to 2009 showed that about 81 red tide events have been recorded along Omani waters of which ten incidents have resulted in mass mortality of fish and other marine organisms.

The first red tide incident was reported during the last week of August 1976 along the Salalah coast between Taqah and Raysut and caused deaths of about 7,000-10,000 tonnes of fish.

Since 1988, there has been regular documentation and monitoring of red tides and their impact on the coastal waters of Oman. Different coastal regions of Oman show variation in susceptibility to algal blooms and red tides, however most of the incidents have been recorded from the Muscat region. The red tides appear to have become more widespread and persistent since late 1980s.