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, 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. 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 by a tethering experiment showing that predation on urchins was similarly high at and near lobster shelters but decreased at ˜100 m from the AR to a similar level as at an unprotected site. Time-lapse photography revealed that predation on tethered urchins was due mostly to the largest size class of lobsters (>100 mm carapace length), which comprised only 7% of the population, highlighting the importance of large-sized lobsters in controlling urchin abundance in localized areas adjacent to urchin-dominated barrens. Despite an ongoing once-a-year fishing event permitted within the MPA, lobster populations were persistent, demonstrating that the cascading effect of the lobsters on urchins and ultimately macroalgae was robust to temporary reductions in predator population size. Erect macroalgal cover was not simply accounted for by snapshot urchin density or biomass, suggesting a hysteresis effect of the phase shifts between macroalgal dominance and urchin barren states.

中文翻译：

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人工鱼礁海洋保护区的营养级联：刺龙虾捕食减轻了海胆的贫瘠

海洋保护区 (MPA) 的最终好处是逆转由人类驱动的关键生态相互作用崩溃引起的营养级联。在这里，我们证明，尽管规模较小（0.28 km ²）且未得到充分保护，但日本西南部具有严格捕捞管理和人工鱼礁 (ARs) 栖息地增强的 MPA 可以在广泛的海胆上形成完善的大型藻类群落通过捕食者恢复的级联效应使贫瘠之地。海胆密度低的区域出现在主要由 MPA 内的采石场 AR 形成的白天龙虾 ( Panulirus japonicus ) 庇护所及其周围。我们在实验室证实龙虾捕食两种主要的海胆（Echinometra sp. A 和海螺)，具有大小和物种依赖性捕食。与龙虾数量少的天然避难所（斑块礁）相比，海胆较少的区域从有大量龙虾的 AR 延伸得更远（~65 m）。这种模式的因果关系通过一项拴系实验得到证实，该实验表明，在龙虾庇护所及其附近，对海胆的捕食量同样高，但在距 AR 约 100 m 处下降到与未受保护地点相似的水平。延时摄影显示，捕食系留海胆的主要原因是体型最大的龙虾（甲壳长度 > 100 毫米），仅占人口的 7%，凸显了大型龙虾在控制海胆丰度方面的重要性。与以海胆为主的贫瘠之地相邻的局部区域。尽管 MPA 允许进行一年一次的捕鱼活动，龙虾种群持续存在，这表明龙虾对海胆和最终大型藻类的级联效应对于暂时减少捕食者种群规模是稳健的。直立的大型藻类覆盖不仅仅由快照海胆密度或生物量来解释，这表明大型藻类优势和海胆贫瘠状态之间的相移存在滞后效应。