Scientists warn Adriatic Sea is changing as warming waters bring new species

CROATIA, 2 August 2026 – The Adriatic Sea is warming at an accelerating rate, and scientists say the effects are already becoming visible beneath the surface, with new marine species arriving, native ecosystems changing and long-term impacts expected for both wildlife and coastal communities.

Recent weeks of intense heat have pushed sea temperatures close to 30°C in some parts of the Adriatic, with swimmers across Croatia noticing the unusually warm water.

While warmer seas may be welcomed by many beachgoers, marine researchers say the long-term consequences are far more significant.

Scientists monitoring the Adriatic have reported an increasing presence of invasive species, including the lionfish and the comb jelly, which can threaten native fish, shellfish and other marine organisms by competing for food, occupying habitats or acting as predators.

Ela Pahor, a marine expert at Aquarium Pula, told HRT reporter Anita Bartolović that invasive species are often more aggressive than native ones and can significantly alter the balance of the marine ecosystem.

Researchers also warn that the Mediterranean Sea is warming faster than expected due to increasingly frequent extreme weather events.

Lionfish (Photo: Jens Petersen/CC BY 2.5)

According to Dr Martin Pfannkuchen from the Ruđer Bošković Institute in Rovinj, the northern Adriatic has experienced exceptionally rapid warming over the past decade, with average annual temperatures increasing by more than 2.7°C, making it one of the fastest-warming marine areas in Europe.

Scientists say rising sea temperatures are only one part of the challenge. Pollution from wastewater, stormwater runoff, chemicals and contaminated rivers is placing additional pressure on the marine environment.

Higher temperatures can also encourage the growth of harmful bacteria, while many shallow coastal habitats have already disappeared, researchers say.

Meanwhile, long-term monitoring by the Institute for Marine and Coastal Research at the University of Dubrovnik shows the Adriatic has warmed by approximately 1.2°C since 1985. Researchers found the pace of warming has accelerated significantly since 2011, with temperatures now increasing by around 1°C every 16 years.

The warming sea is also changing marine biodiversity. Scientists have recorded more than 20 new plankton species in the Adriatic over the past 30 years, including two species previously unknown to science.

Although researchers say there are currently no major disruptions to plankton communities in the southern Adriatic, early signs of ecological change have already been observed. In the Mljet Lakes, one native jellyfish species has already been displaced by an introduced species.

Scientists say continued warming is expected to gradually reshape the composition of marine plant and animal communities throughout the Adriatic, with consequences for biodiversity as well as people whose livelihoods depend on the sea.