IN MARCH 2024, some beaches in Sabah experienced a massive invasion of jellyfish swarms. These jellyfish are called “tomato jellyfish” (Crambione sp.) and there were so many of them that the beach looked like a giant bowl of tomato soup. This came on the heels of multiple reports of sting cases from the Portuguese Man O War jellyfish (Physalia physalis) along the east coast of Peninsular Malaysia, causing negative publicity and impacting local coastal tourism.
This sudden but temporary increase in the jellyfish population, termed “population blooms,” is not new in Malaysia. Historical records have indicated at least 65 cases of jellyfish blooms occurred in Malaysian waters from the early 1960s to the present, where at least 10 jellyfish species have been identified as the culprit.
[ihc-hide-content ihc_mb_type=”block” ihc_mb_who=”unreg” ihc_mb_template=”3″ ]Despite their frequent and massive blooms, jellyfish have not been a priority for scientific research in Malaysia until recently. Local scientists from Universiti Putra Malaysia and Universiti Malaysia are now studying the causes of the bloom phenomenon, including how local environmental changes can affect jellyfish populations and why they only thrive at certain times. This research will help provide a better understanding of their role in the ocean.
Climate change, for instance, could be a factor in jellyfish population blooms. Interestingly, the recent blooms of Crambione sp. and other jellyfish species in Malaysia occurred during the years when El Nino intensified, namely 2016, 2018, 2020, and early 2024. During El Nino, the ocean experiences warmer waters, lower oxygen, and ocean acidification, which can be stressful for less adaptive marine organisms.
However, these conditions are favourable for jellyfish to thrive. In temperate regions, warmer temperatures have been linked to the increased numbers of at least 18 jellyfish species, while in Malaysia, jellyfish blooms were frequently reported during the warmer months from January to September.
Climate change – A winning situation for jellyfish
Why jellyfish could be the biggest winners from climate change? Scientists have found that warm temperatures could trigger the strobilation (recruitment) of jellyfish juveniles and accelerate their growth. Additionally, adult jellyfish could expand their range towards temperate and subtropical regions. Jellyfish can also tolerate low-oxygen (hypoxic) conditions better than their competitors, such as fish and shellfish, due to their lower oxygen and food demands.
Moreover, ocean acidification, which reduces calcification in most skeleton-forming organisms, may benefit non-calcifying predators or competitors, including jellyfish.
Aside from climate-related effects, jellyfish booms are also caused by other human activities, such as overfishing. Overfishing has led to a decline in the populations of jellyfish predators and competitors, which has reduced the pressure on jellyfish. This means that there are fewer predators to feed on the eggs and larvae of jellyfish. The increase in human-made structures, such as fishing stakes, fish cages, and jetties, also promotes the jellyfish’s benthic life stage. This stage requires them to settle on hard surfaces, similar to sea anemones.
The increase in jellyfish blooms around the world, including Malaysia, over the past few decades is a cause for concern due to their impact on the ecosystem and humans. Jellyfish often present stinging threats to humans and are a common cause of human injury worldwide. Some species, particularly the Portuguese Man O’ War, Irukandji, and Chironex sp., can cause severe symptoms, complications, and even fatalities from their harmful stings.
In Malaysian waters alone, over 700 cases of jellyfish stings (both fatal and non-fatal) have been reported since the early 2000s. More recently, a 5-year-old French boy died after being stung by an unidentified cubozoan while swimming at a beach on Pangkor Island.
Beyond individual harm, the blooms of the jellyfish population may also negatively disrupt economy-driven human activities. As most jellyfish sting cases often involve beachgoers, beach closures can hinder recreational beach activities and cause losses in tourism revenue.
The blooms can also have adverse effects on commercial fisheries and aquaculture by damaging fishing nets, contaminating catches, and reducing fish stocks. The massive occurrences of jellyfish are harmful to fish populations since they can prey on fish larvae and eggs, compete with zooplanktivorous fish species, and act as intermediate vectors for various fish parasites.
Nevertheless, the blooms of economically valuable species have benefitted local jellyfish fishery. Four local species, namely Lobonemoides robustus, Rhopilema esculentum, Rhopilema hispidum, and Acromitus hardenbergi have been commercially harvested since the 1970s. These species are known to have low calories, high mineral contents, and good protein quality, making them highly nutritious and beneficial for medicinal purposes. The local jellyfish harvests are processed as semi-dried food products at local factories and exported to various Asian countries, especially China, Korea, and Japan.
Among Southeast Asian countries, Malaysia is ranked third after Thailand and Indonesia in terms of the amount of jellyfish commodities exported.
Until recently, the Intergovernmental Oceanographic Commission of UNESCO, through its Sub-Commission for the Western Pacific (IOC-WESTPAC), has been a significant help in promoting collaborative research and networking among Western Pacific countries in jellyfish research, bloom monitoring, information sharing, and hazard awareness.
However, we still need more information to know why there are so many jellyfish in some areas and if it’s because of climate change or other human factors. Also, we need to learn more about the life and behaviour of jellyfish so we can predict where they’ll be and when. This information is urgently needed so we can better manage and reduce the impact of jellyfish blooms on the marine environment and human well-being amid climate shifts.
[/ihc-hide-content]
