Human activities among possible factors in Teluk Bahang fish deaths: report

GEORGE TOWN – The Centre for Marine and Coastal Studies (Cemacs) at Universiti Sains Malaysia has identified human activities as among factors which may have contributed to the recent deaths of thousands of fishes near the Teluk Bahang coast here.

The widespread deaths were seen in the waters which turned pink due to the algal bloom – a pollutant whose ammonia content can be deadly to marine life, particularly fishes.

A report on the incident has been sent to the state government, and a copy of which was shared with The Vibes by Cemacs director Prof Aileen Tan Shau Hwai.

It stated that the cause of algal bloom can be from human activities such as runoffs from agriculture, dissolved chemicals introduced into water supplies via rainfall or irrigation, and effluent from sewage treatment plants, which all contribute to excess amounts of nutrients in our waterways.

These nutrients are food for algae.

It is important to ensure all waste is treated before discharging to the sea and to reduce the amount of nutrients running off to the water bodies and eventually entering the coastal areas and ocean.

Tan hopes that such findings can generate awareness on the discharging of waste into the open seas surrounding Penang.

The report’s summary said that from August 26 to 29, patches of pink algal bloom were observed along Teluk Bahang.

The bloom occurred following a spell of heavy rain a few days earlier.

The bloom was caused by the dinoflagellate, Noctiluca scintillans, which is quite large in size (0.2-2 mm in diameter).

Adequate nutrients brought by substantial rainfall may have triggered the N. scintillans bloom.

Local hydrodynamics and the diverging currents governed the presence and dispersion of the bloom in the area.

This dinoflagellate is not known to produce toxins, but it has negative effects on the environment due to the release of ammonia and using up lots of oxygen when decomposing.

The high ammonia content of the vacuole irritates fishes, which generally avoid the bloom areas.

The low oxygen and high ammonia are what kills the fishes.

In addition, blooms of this species can be responsible for environmental hazards, such as fish kills due to clogging of gills or reduction of oxygen levels in the water.

It may also be an indicator of anthropogenic eutrophication.

Many dead fish have been reported and spotted near the beach and surface of the coastal area.

The whole event was first noticed two or three days ago when the bottom dwellers (stingray, crabs) were found on the surface or at shallow waters, most probably due to low oxygen levels (asphyxiation: deprived of oxygen, resulting in unconsciousness or death; suffocation). In addition, a strong stench of sulphide in the mud was also reported.

The bloom was not observed after four days at Teluk Bahang and it was assumed to have drifted away due to the vigorous movement of the tides and water currents when the spring tide approached.

The algae were observed at Pulau Betong on September 8, indicating that the bloom was set adrift by the southwestern wind and current. 

The bloom has surfaced when the tides had changed to neap again, with strong sunlight during the day.

However, no dead fish were observed on the day of reporting.

One of Malaysia’s oldest nongovernmental organisations, Sahabat Alam Malaysia, has been campaigning for decades over the need to prevent any unnecessary discharges of pollutants into the waterways of rivers and seas.

It also warned of the increasing effect of plastic waste pollution here. – The Vibes, September 16, 2023

Source: The Vibes https://www.thevibes.com/articles/news/98773/human-activities-among-possible-factors-in-teluk-bahang-fish-deaths-report