What happens below the surface when you dive?

The Mediterranean Sea is warming faster than most other seas worldwide, with consequences becoming increasingly evident. Scientists warn that rising temperatures are enabling invasive species to spread rapidly, displacing native fish, mollusks, and other marine organisms. Some changes are already irreversible, significantly affecting both the marine ecosystem and fisheries, as well as coastal communities. In recent years, the Mediterranean has experienced a notable increase in water temperatures, driven primarily by global warming caused by fossil fuel use. The sea's semi-enclosed nature means heat accumulates more slowly compared to open oceans, leading to prolonged periods of elevated temperatures. According to scientific estimates, the sea’s temperature could rise by two to six degrees Celsius by 2100, with more frequent and intense marine heatwaves. Other projections suggest a temperature increase of approximately 1.8 to 3.5 degrees Celsius depending on emission scenarios and regional factors. Invasive species pose a growing threat to the region’s biodiversity. Warmer waters create favorable conditions for species that enter the Mediterranean mainly through the Suez Canal. These include venomous fish, jellyfish, and catfish, which are spreading more quickly toward the western part of the sea. Some of these species present dangers to humans: venomous fish have toxic spines, while jellyfish contain potent toxins that can be lethal upon ingestion. Marine biologist Ernesto Azzurro from Italy’s National Research Council noted that around 1,000 invasive species have been identified in the Mediterranean, with approximately 800 having established permanent populations. The effects are particularly pronounced in the eastern part of the basin, where nearly 93% of native mollusk populations have disappeared in shallow waters. On Cyprus, some invasive species have already displaced traditional marine organisms. Azzurro emphasized that the Mediterranean will become even poorer in biodiversity, especially in its eastern regions, where climate change has created conditions unsuitable for native species. “The Mediterranean will be even worse off and have fewer species because climate change, especially in its eastern part, creates conditions that are no longer suitable for native species,” he stated. These ecological shifts are not limited to nature alone, they also affect human populations. Scientists have observed mass die-offs of mussels along the Italian coast of the Adriatic Sea. In some areas, water temperatures exceeded 30 degrees Celsius, resulting in almost complete population losses from certain mussel species. Azzurro warned that if no resilient populations emerge under new climatic conditions, the future of mussels in the Adriatic Sea looks bleak. “The decline has been spectacular. If we don’t find populations that can survive in these new climatic conditions, the future of mussels, at least in the Adriatic Sea, is not promising,” he added. Fishermen are also facing challenges as native fish species decline, forcing them to adapt to new types of catch and altered living conditions. Coastal communities must adjust their livelihoods and traditions in response to these environmental changes. Experts agree that completely eliminating invasive species is no longer feasible, but limiting their spread and reducing their impact is possible. Recommended measures include promoting the fishing of beneficial invasive species, safely removing dangerous ones, and stricter control over ballast water from ships, which often transport foreign organisms between seas. According to estimates, such actions could reduce the introduction of new invasive species by 95 to 99 percent. Zoologist Piero Genovesi from Italy’s Institute for Environmental Protection and Research stressed that while solutions exist, they require a collective global vision. “We know what needs to be done. We must reduce fossil fuel use. This is a clear issue for humanity, and we know the solutions, although they demand a shared global perspective,” he concluded.