Unwelcome 'swimmers' set their sights on Aussie beaches

A popular rock pool was slammed shut for cleaning late last week as hoards of "unwelcome swimmers" descended on the area and a wildlife expert said if the weather continues to stay as hot as it has been, we're likely to see "a bumper season".

On Friday afternoon, Ross Jones Memorial Pool in Coogee in Sydney's east, was closed after countless sea maggot larvae were spotted invading the water. The critters, a species of what’s known as "seaweed flies" or "kelp flies" are "very common" — both globally and on "our beaches in particular".

They favour the humidity, hatching from their eggs in decaying seaweed. They're also responsible for breaking down sea vegetation along the shoreline, meaning they have an important part to play in the ecosystem, though Eastern Suburbs residents hoping to cool off with a dip were probably less than impressed to find their favourite pool closed.

Popular swim spot in Sydney's east closes for cleaning

A spokesperson for Randwick City Council said the site has since reopened, which they said is cleaned rigorously once a week.

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"We clean all our ocean pools weekly, fortunately this particular issue regarding sea maggots is not common," a spokesperson told Yahoo News Australia. "It was likely a combination of the hot weather and small swells that created the conditions to encourage the larvae growth."

Insect expert warns Aussies to be prepared for a 'bumper season'

Speaking to Yahoo, Dr Tom White, entomologist and lecturer at The University of Sydney, said if "these weather conditions persist" it's likely to be a "bumper season" for the insects.

"Warmth and humidity is great for many if not most insects, including flies, so as those conditions persist it’s likely to be a bumper season," White said.

"Predicting precisely which species will benefit the most is difficult, but it’s generally a safe bet to guess that the common insects we bump into day-to-day (like these flies) will do particularly well.

'Good news story' for hungry wildlife

White explained that though "a little unpleasant", they don't pose any risk to beachgoers. "With that said, however, the local birds, fish, crabs, and other scavenging sea-life will be grateful for the bountiful meal," he said. "So it’s a good news story for the local wildlife.

"These flies lay their eggs in the seaweed, and many also use it for foraging and mating.

"Any influx of seaweed is likely both to contain quite a high number of flies, and to attract others from nearby. Their lifespans are quite short like most insects, so a week or two of seaweed is often enough to see the local population start to grow in numbers too."

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