An algal bloom has resulted in the deaths of sardines near the Coast Guard port in Sidab. According to an expert from the Marine Science and Fisheries Centre (MSFC), Ministry of Agriculture and Fisheries, the fish choked to death due to the shortage of oxygen.
“After investigating the samples, it was found that the oxygen levels had dropped to 1.2 mg/l, caused by the excessive growth of phytoplanktons,” an expert from MSFC said. The level of oxygen should be around 1.5mg/l and above.
Contrary to common belief most phytoplanktons are useful for the marine environment. It is only when there is an overgrowth or a bloom that they might be harmful, the expert said.
Badr bin Hadeeb bin Mubarak al Qataiti, a fisherman said, “Some algae are a source of food for some types of fish but they cause a lot of problems. They spread in water very fast reducing oxygen supply which can lead to deaths of fish.”
However, phytoplanktons are an important part of the healthy marine life, said Dr Khalid Abdullah al Hashmi, researcher and biological oceanographer, Department of Marine Science and Fisheries at Sultan Qaboos University. “Phytoplanktons represent the base of the food chain, so they are of significant importance to both fisheries and the environment. Phytoplanktons contribute about 95 per cent of total production in the marine environment, with the balance being contributed by benthic macrophytes and sea grasses. The abundance of phytoplanktons can be taken as one of the fastest and most efficient means to assess quantitatively the fisheries potential in a given area.”
Dr Hashmi added that phytoplanktons contribute more than 50 per cent of oxygen in Earth’s atmosphere. “This oxygen is produced as a by-product of photosynthesis process. During this process, phytoplanktons are responsible for most of the transfer of carbon dioxide from atmosphere to ocean. About 20mn tonnes of carbon dioxide is transferred daily from atmosphere to oceans around the world.”
He said that phytoplankton overgrowth or bloom (known as Harmful algal bloom-HAB) can be detrimental to both the environment and human activities. “This overgrowth can have natural origin or can be stimulated by excessive runoff of nutrients from land or by the discharge of untreated sewage into coastal waters which can serve as fertiliser for these micro algae. There are a number of ways in which HABs cause harm.”
Different species of phytoplanktons may contain one or more potent toxins, which may be concentrated as they move through the food chain, negatively impacting the organisms (including humans) that consume them.
“Some HABs, via their toxins, or indirectly through their biomass accumulation, can kill fish. High fish mortalities may be caused by the development of low oxygen conditions or gill clogging and damage due to mucus secretion and asphyxiation,” said Dr Hashmi.
ROP statement on fish deaths
Reacting to reports doing the rounds on social media that the Coast Guard port is responsible for the deaths of fish near Sidab, the ROP stated, “We would like to clarify that the port project was undertaken after scientific studies were conducted by international companies. The port entrance was widened to ensure that no harm was caused to marine organisms in the area. All licences and permits were issued before the start of the project and that ROP specialists constantly monitored work on the project. Deaths of fish occurred not only in this area, but in other areas too.”