Simulated Heatwaves Reshuffle the Mediterranean's Tiny Food Web

As climate change intensifies, marine heatwaves are becoming a critical threat to coastal ecosystems. In a recent study conducted in the Thau Lagoon, France, scientists used mesocosms—controlled water enclosures—to simulate a temperature rise of 3°C above ambient levels for ten days.

The results illustrated a classic 'trophic cascade', a side-effect where changes at the top of the food web ripple downwards. The heat caused an increase in metazooplankton (animal plankton), which heavily preyed upon protozooplankton. With these microscopic grazers removed, their usual food source—phytoplankton—was left unchecked and began to proliferate.

However, this was not a simple boom for all algae. The metazooplankton also consumed larger phytoplankton cells, forcing the community to shift towards smaller species. Even after temperatures returned to normal, recovery was uneven; groups like nanophytoplankton struggled to bounce back. This experiment highlights how warming waters do not just kill organisms directly; they fundamentally restructure the complex relationships that sustain marine life.