GEORGE TOWN: Rising sea temperatures are slowly affecting vital marine habitats like coral reefs and seagrass beds, increasing their risk of bleaching, according to a marine biologist.

Coastal states like Penang are particularly vulnerable as rising heat warms not just the surface but also deeper waters, disrupting marine life balance.

Universiti Sains Malaysia (USM) Centre for Marine and Coastal Studies (Cemacs) director Prof Datuk Dr Aileen Tan said bleaching occurs when vital algae are expelled, leaving the ecosystems vulnerable to disease and death.

“Algae provide essential nutrients to corals in exchange for shelter and protection.

“Additionally, warming waters disrupt the growth, reproduction and metabolic functions of seagrass beds as well as mangroves, which are vital nurseries for many marine species,” she said.

Prof Tan said studies have revealed that as waters increase in heat, fish catches actually become smaller, younger and less abundant.

“As the ocean warms, a silent migration occurs beneath the waves, where fish and other marine creatures begin seeking refuge in cooler waters.

“This shift towards higher latitudes or deeper depths as such can drastically alter local marine biodiversity,” she added.

The threat extends to aquaculture industries, as warm temperatures also increase the threat of diseases.

“Warmer temperatures create optimal conditions for pathogens to thrive. Bacteria multiply and spread more quickly in elevated temperatures.

“Increased temperatures also translate to lower capacity for water to hold oxygen, exacerbating the challenges in aquaculture by altering nutrient dynamics and microbial communities.

“This imbalance results in algal blooms, such as a red tide, which produce toxins harmful to marine life,” said Prof Tan.

According to the Annual Fisheries Statistics 2022 published by the Fisheries Department, approximately 52% of Malaysia’s seafood production came from aquaculture.

Prof Tan said the increase in water temperature at sea contributed to the increased harvest of prawns by fishermen, shifting their seasonal pattern and resulting in wet markets now experiencing an abundance of prawns available for sale.

“These conditions of increased tonnage will probably not last as they are also tied down to food in the water, which may be limited later,” she said.

She said the added warmth provides marine organisms with a reproduction boost.

“The increase in temperature would enhance the reproduction cycle and trigger more frequent spawning of marine organisms.

“As lakes and dams dry up, rivers release less amounts of freshwater into the sea, thus raising the salinity of the coastal seas.

“High salinity at sea, followed by a sudden rain that lowers the salinity, will trigger spawning too.”

At Pulau Tikus Market, fishmonger Tan Lam Soon, 40, said boats are now returning with just over a basket of prawns for him each day.

Despite the scarcity, he ex- plained that the drop in price for prawns is due to a fall in consumer demand.

“Large prawns that used to cost RM80 per kg are now just RM65 per kg. That is because people are buying less and there is a surplus,” he said, adding that there are fewer squids, which had led to higher prices from RM30 per kg to RM35 per kg.

At Cecil Street Market, fishmonger Chng Meng Siang, 39, said in recent weeks, there was still ample supply for mid-sized prawns, which led to a price drop.

Chng, who operates the biggest stall in the market, added that while the supply of other seafood is stable, the supply for squids has been low and they are now more expensive.

https://www.thestar.com.my/news/nation/2024/08/17/the-threat-of-warmer-seas