Trophic cascade in a marine protected area with artificial reefs: spiny lobster predation mitigates urchin barrens.

An ultimate benefit of marine protected areas (MPAs) is to reverse trophic cascades caused by human-driven collapse of critical ecological interactions. Here we demonstrate that, despite a small scale (0.28 km ) and not being fully protected, an MPA with strict fishing management and habitat enhancement by artificial reefs (ARs) in southwest Japan can lead to well-established macroalgal communities on widespread sea urchin barrens through cascading effects of predator recovery.

Experimental evaluation of the anti-attachment effect of microalgal mats on grazing activity of the sea urchin Strongylocentrotus nudus in oscillating flows.

Algal mats can hinder the adhesion of the tube feet of sea urchins. This leads to the hypothesis that the restriction of sea urchin feeding activity by wave action can potentially be enhanced by the presence of algal mats, which will facilitate the survival of kelp recruits at sites with wave action in urchin barrens. To evaluate the potential anti-attachment effect of algal mats on sea urchins, a laboratory tank experiment was performed on the movement of Strongylocentrotus nudus sea urchins and their grazing on juvenile kelp plants at the center of 30×30 cm flat test substrates with or without a thin-layer microalgal mat at four levels of oscillatory flow (maximum orbital velocity: 10, 20, 30 and 40 cm s(-1)).