Beachgoers who have been hoping for a jellyfish-free summer may get their wish fulfilled this year as an early bloom for the species likely means they will be fewer in numbers during the hot months, marine biologist Alan Deidun told Times of Malta.
Deidun, who coordinates the Spot the Jellyfish campaign, said that since the bloom, which is when there is a substantial growth of the species in a relatively short period of time, had already been spotted this year, this could likely result in far fewer jellyfish drifting into beaches this coming summer season.
“The central Mediterranean normally experiences a bloom in the population of several gelatinous species each year during late winter or early spring, over the January-March period,” he said.
“In colder or more temperate seas, this bloom normally happens later on in the year, around May or June, but, in the central Mediterranean, our spring bloom is actually a winter bloom, mainly since the food that these creatures feed upon in turn bloom at this time of the year,” he added.
Deidun said that the bloom in Malta is largely made up of the mauve stinger, the most common stinger in the Mediterranean Sea, with a nonetheless nasty sting.
Other species that are found in the gelatinous soup include the comb jellies, a harmless but beautiful creature, and more dangerous varieties like the Portuguese Man O’War and the barbed-wire jellyfish.
“The blooming jellies don’t just feed when they meet up – they also reproduce by spawning,” Deidun explained.
“The exact timing of spawning for the mauve stinger varies from year to year, depending on a number of environmental cues, including air and water temperature, the amount of precipitation, storminess, for example, in January and February.
“This year’s winter has been a particularly cold, windy and a prolonged one, such that water temperatures have dipped below the 15-degree mark, which has not happened for a number of years prior to this year and stayed cold for long.”
Jellyfish blooms are not sustainable as they tend to over-consume their food resources
This means that the first generation of mauve stingers that have hatched this year appeared early and in large numbers, which also attracted jellyfish-eating species to appear in large numbers in close association with the jellyfish bloom.
“Jellyfish blooms are not sustainable as they tend to over-consume their food resources and, since this year’s first-generation came of age quite early, between March and April, then we can expect that relatively few numbers of mauve stingers will be around in summer since the bulk of the bloom would have been consumed or dispersed,” Deidun said.
“There is pronounced inter-annual variability in the timing of jellyfish reproduction as jellyfish are very sensitive to environmental conditions around them. Besides, predator-prey relationships are closely paired, even in the marine domain and not just on land.”
He stressed that constant observation of such events has been crucial to helping the team understand what is happening and this is only made possible through citizen science.
Events unfolded similarly in 2021 when colder winter temperatures again caused mauve stingers to bloom earlier.
However, in 2019, Malta’s beaches were still plagued with jellyfish at the beginning of the swimming season, with thousands of the creatures floating in bays and washing up on the shores.