Context

• Extreme heat has plagued the Mediterranean for weeks. Wildfires have raged across at least nine countries in the region from Algeria to Greece.

  • The soaring temperatures are not only a danger for people and ecosystems on land, they’re also harming marine life.

Mediterranean sea

• At the end of July, Mediterranean Sea surface temperatures hit a record 28.7 degrees Celsius (83.66 Fahrenheit), with some eastern parts of the waters reaching more than 30 C.
• Those temperatures could rise further in August, which is usually hotter.

But why are high sea temperatures a problem?

• 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.
• 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.
  • 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. Benthics like soft corals, seaweed and seagrasses provide some of the main ocean habitats.
• Heat is particularly harmful for Posidonia oceanica or Neptune grass.
• And the large, 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.
• 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.
• Habitat loss could also lead to an overall decline in fish populations, while disappearing seagrass means coasts will be more exposed to future storms. 

Way Forward

• We need to increase the number of strictly protected areas where fishing, diving and boating are not allowed.
• Designating protected areas isn’t enough, they also have to be properly managed, which is something that’s lacking now.
• Some of the Mediterranean’s new inhabitants could also be a helpful addition as the planet heats up.
  • Tropical seaweed Halophila stipulacea Ascherson, originally native to the Red Sea, copes well with rising temperatures and salinity levels compared to other seaweeds.
• It’s an invasive species that could potentially help “seagrass beds survive in a smaller part of the Mediterranean and continue to provide some of their essential ecosystem services.

Source: IE

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