Record sea temperatures seen in the Mediterranean could devastate marine life

A mass mortality event is a single, catastrophic incident that rapidly wipes out vast numbers of a species. Around 88% of these events in the Mediterranean were associated with hard sea floor inhabitants, such as corals. However, seagrasses and the more diverse community of the soft sea floor were also severely affected, accounting for 10% and 2% of these events, respectively.

Deaths in shallow water

More than two-thirds of the deaths of marine organisms occurring on the hard sea floor were in the shallowest waters. Marine environments with a depth of 0–25 meters are subject to particularly intense warming and are home to some of the most biodiverse ecosystems in the Mediterranean, formed by coral-like organisms. Other research estimates that marine heatwaves have been responsible for the loss of 80–90% of Mediterranean coral density since 2003.

Foundation species tend to be habitat-forming organisms and are therefore critical in structuring an ecosystem. They act as nursery grounds, provide protection against predators, and serve as a food source. Foundation species are key to sustaining biodiversity, and their loss will have repercussions for other species. As foundation species, the loss of coral, seagrass, and seaweed is particularly concerning.

It is not just intense heat stress that is causing mortality events. High water temperatures are associated with the proliferation of disease-causing organisms, such as bacteria, fungi, and viruses. This may further reduce the ability of the ecosystem to adapt to extreme heat, contributing to additional ecological damage.

Migration of marine life

As well as prompting the widespread death of marine life, marine heatwaves often trigger migration. Warm-water invasive species will move towards the warmer areas, replacing species escaping the rising temperatures. Anecdotal evidence suggests that the exceptional temperatures seen across the Mediterranean this summer may be driving extensive mass migration.

Leave a Comment