Climatic anomalies may create a long-lasting ecological phase shift by altering the reproduction of a foundation species.

The resilience of ecological communities is often defined by one or a few species that have disproportionately important roles influencing many other species in the community. This is true for some areas of the Mediterranean Sea that are characterized by large brown fucoid algae in the genus Cystoseira that form dense underwater forests structurally similar to the giant kelps of the Pacific. While shorter than the giant kelp, Cystoseira form dense underwater stands, contributing to the three-dimensional complexity of the seascape (Fig. 1). These canopy-forming seaweeds play a crucial role in primary production and nutrient cycling of temperate coastal ecosystems from the Mediterranean Sea to the Atlantic Ocean (Mineur et al., 2015) and act as 'ecosystem engineers', providing food, nursery, and shelter for a rich associated biota. This article is protected by copyright. All rights reserved.