Mass mortality events involving marine taxa are increasing worldwide. The long-spined sea urchin Diadema africanum is considered a keystone herbivore species in the northeastern Atlantic due to its control over the abundance and distribution of algae. After a first registered mass mortality in 2009, another event off the coasts of Madeira archipelago affected this ecologically important species in summer 2018. This study documented the 2018 D. africanum mass mortality event, and the progress of its populations on the southern coast of Madeira island. A citizen science survey was designed targeting marine stakeholders to understand the extent and intensity of the event around the archipelago. Underwater surveys on population density prior, during and after the mass mortality, permitted an evaluation of the severity and magnitude of the event as well as urchin population recovery. A preliminary assessment of causative agents of the mortality was performed. The event was reported in the principal islands of the archipelago reducing the populations up to 90%. However, a fast recovery was registered during the following months, suggesting that the reproductive success was not compromised. Microbiological analyses in symptomatic and asymptomatic individuals, during and after the event, was not conclusive. Nevertheless, the bacteria Aeromonas salmonicida, or the gram-negative bacteria, or the interaction of different types of bacteria may be responsible for the disease outbreak. Further studies are needed to assess the role of pathogens in sea urchin mass mortalities and the compound effects that sea urchins have in local habitats and ecological functioning of coastal marine ecosystems.

世界范围内涉及海洋生物群的大规模死亡事件正在增加。长脊海胆迪亚德马。非洲被认为是在大西洋东北部的一个重点食草动物物种由于其对藻类的丰度和分布的控制。在2009年首次出现大规模死亡之后，马德拉群岛海岸附近的另一起事件在2018年夏季影响了这一具有重要生态意义的物种。该研究记录了2018年非洲象D草（D. africanum）大规模死亡事件及其在马德拉岛南部海岸的人口发展。设计了一项针对海洋利益相关者的公民科学调查，以了解该群岛周围事件的程度和强度。在大规模死亡之前，之中和之后对人口密度进行水下调查，可以评估该事件的严重性和严重程度以及海胆种群的恢复情况。对死亡率的病因进行了初步评估。据报道，该事件在群岛的主要岛屿上使人口减少了90％。但是，在接下来的几个月中，出现了快速恢复，这表明繁殖成功并未受到损害。有症状和无症状个体在事件发生期间和之后的微生物学分析，尚无定论。尽管如此，细菌鲑鱼气单胞菌或革兰氏阴性细菌，或不同类型细菌的相互作用可能是造成疾病暴发的原因。需要进一步的研究来评估病原体在海胆大规模死亡中的作用以及海胆对当地栖息地和沿海海洋生态系统的生态功能的复合影响。