MEDITERRANEAN SEA

• In a warming world, marine creatures are in danger of suffocating. Gases like oxygen and carbon dioxide dissolve better at colder temperatures, so that means the warmer the water, the less oxygen is available to breathe
• Conversely, higher temperatures also cause an increase in metabolism, which in turn means animals have to breathe even more than usual
• That combination also heightens the risk of death by starvation for marine life
• Algal blooms are more common in hotter waters too. Such blooms can further deplete oxygen levels and produce toxins harmful for fish, marine mammals and birds, for instance

• High water temperatures are most harmful for animals living at the bottom of oceans, lakes or rivers.
• These benthic species include corals, mussels, sponges, starfish and plants like sea grasses, and are often attached to rock or solid ground. They can’t migrate when it gets too hot
• Scientists observed mass deaths of benthic species along thousands of kilometers of Mediterranean coastline between 2015 and 2019
• Many benthic species are crucial to the marine ecosystem. They filter the water and keep seas, rivers and lakes clean by eating dead organisms
• Some species are an important food source for other creatures or are harvested by humans. Benthic like soft corals, seaweed and seagrasses provide some of the main ocean habitats
• Heat is particularly harmful for Posidonia oceanica or Neptune grass
• Slow-growing seagrass is found only in the Mediterranean. Previous heat waves have decimated the species, which is bad news for the climate

• Jellyfish, on the other hand, are thriving because of higher temperatures, as well as nutrient run-off from farms and sewage.
• Overfishing and loss of fish habitat mean the jellyfish have few or no predators.
• When currents push the animals together, the Mediterranean turns into a crowded jellyfish hotspot
• The sea also hosts around 1,000 invasive species, the highest number in the world
• While this is not directly linked to climate change or rising temperatures “such conditions clearly favor species introduced from warmer seas
• Alien species can have a major impact on ecosystems. For instance, invasive Rabbitfish native to the Indo-Pacific and Rea Sea feed on seaweed and have reshaped the habitat of the eastern Mediterranean. Underwater deserts have replaced dense seaweed forests.
• Warming seas are already affecting fishing activities in the area.
• Fishermen are catching fewer familiar species and instead are finding more invasive fish which they have difficulty selling
• Habitat loss could also lead to an overall decline in fish populations, while disappearing seagrass means coasts will be more exposed to future storms.
• This could also have a knock-on effect for tourism because divers will be less likely to visit an impoverished underwater landscape