Data from: Marine Phytophthora species can hamper conservation and restoration of vegetated coastal ecosystems

Phytophthora species are potent pathogens that can devastate terrestrial plants, causing billions of dollars of damage yearly to agricultural crops and harming fragile ecosystems worldwide. Yet, virtually nothing is known about the distribution and pathogenicity of their marine relatives. This is surprising, as marine plants form vital habitats in coastal zones worldwide (i.e. mangrove forests, salt marshes, seagrass beds), and disease may be an important bottleneck for the conservation and restoration of these rapidly declining ecosystems. We are the first to report on widespread infection of Phytophthora and Halophytophthora species on a common seagrass species, Zostera marina (eelgrass), across the northern Atlantic and Mediterranean. In addition, we tested the effects of Halophytophthora sp. Zostera and Phytophthora gemini on Z. marina seed germination in a full-factorial laboratory experiment under various environmental conditions. Results suggest that Phytophthora species are widespread as we found these oomycetes in eelgrass beds in six countries across the North Atlantic and Mediterranean. Infection by Halophytophthora sp. Zostera, P. gemini, or both, strongly affected sexual reproduction by reducing seed germination 6-fold. Our findings have important implications for seagrass ecology, because these putative pathogens likely negatively affect ecosystem functioning, as well as current restoration and conservation efforts.疫霉属（Phytophthora）物种是极具致病力的陆生植物病原菌，每年对农业作物造成数十亿美元的经济损失，并破坏全球脆弱的陆地生态系统。然而，学界对其海洋近缘类群的分布与致病性却几乎一无所知。这一现状颇为出人意料，因为海洋植物是全球近岸带的关键生境（包括红树林、盐沼、海草床），而病害可能正是这些正快速衰退的生态系统在保护与修复过程中面临的重要瓶颈。本研究首次报道了北大西洋与地中海区域内，疫霉属与海疫霉属（Halophytophthora）物种对常见海草物种大叶藻（Zostera marina，俗称鳗草）的广泛侵染现象。此外，我们在多种环境条件下开展全因子实验室实验，检测了海疫霉未定种Zostera（Halophytophthora sp. Zostera）与双子疫霉（Phytophthora gemini）对大叶藻种子萌发的影响。研究结果显示，疫霉属物种分布广泛：我们在北大西洋与地中海沿岸6个国家的海草床中均检出了这类卵菌（oomycetes）。海疫霉未定种Zostera、双子疫霉，或二者共同侵染，均显著抑制了大叶藻的有性繁殖，使种子萌发率降低了6倍。本研究发现对海草生态学具有重要意义：这些潜在病原菌可能对生态系统功能产生负面影响，同时也会干扰当前的海草修复与保护工作。