Trophic cascade in a marine protected area

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 km2), and not being fully protected, a 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. Areas with low urchin densities occurred in and around daytime lobster (Panulirus japonicus) shelters primarily formed by quarry-rock ARs inside the MPA. We confirmed in the laboratory that lobsters preyed on two dominant sea urchins (Echinometra sp. A and Heliocidaris crassispina), with size- and species-dependent predation. The area with few urchins extended farther (~65 m) from an AR with numerous lobsters than from a natural shelter (patch reef) with far fewer lobsters. Causation of this pattern was confirmed...