Scientists say manmade structures provide ideal habitat that explains surge in numbers
If you are noticing more jellyfish in the sea on your holiday this summer, the blame may lie just over the horizon.
Scientists have discovered that offshore wind farms and oil and gas plat- forms provide an ideal habitat in which the creatures can thrive.
Until now, the rapid increase in jellyfish numbers in oceans around the world has been largely blamed on overfishing, which wipes out their natural predators, global warming and nutrient run-off.
The research suggests man-made structures have played a role in the jellyfish boom by offering a home for polyps – the tiny organisms which eventually grow into jellyfish. “They preferably attach to downward-facing solid surfaces and since the availability of these is scarce in nature, they can be predominantly found on man-made structures,” the team of Slovenian and Portuguese scientists report.
The phenomenon is particularly pronounced in the Adriatic, where populations of a species called moon jellyfish, which do not have a strong enough sting to harm humans, have increased in numbers in recent years.
The researchers believe the explosion in numbers is closely related to the growth in oil and gas platforms in the Adriatic – from just a handful in 1970 to around 150 now. In a report published in Environmental Research Letters, they used computer simulations to recreate the dynamics of ocean currents and the life-cycle of moon jellyfish.
The results suggested a correlation between big jellyfish numbers and man-made structures such as energy platforms and wind farms. The structures “enable the formation of new populations in formerly unpopulated open waters,” the scientists found after a five-year study. Scattered across the Adriatic, they enable isolated populations to find each other and breed.
The profusion of jellyfish was “an aspect that is usually overlooked when evaluating the ecological impact of existing and future wind farms, oil and gas platforms”, the scientists said.
A large number of jellyfish in the sea signals the deterioration of marine ecosystems, and can clog the intake pipes of shore-based power stations and desalination plants, weigh down fishing nets and – in the case of some stinging species – present a danger to humans.
The research has implications for British waters, where hundreds of offshore turbines are under construction or planned. Last year, wind farms in the UK generated more electricity than coal-powered plants. In Europe, the power-generating capacity of offshore wind installations more than doubled in three years, from 2012 to 2015.
“With the recent push towards renewable energy, the numbers (of wind farms) have skyrocketed, and that is just a fraction of what to expect in the future,” the scientists said.