Seagrasses, a polyphyletic group of about 60 marine angiosperm species, are the foundation of diverse and functionally important marine habitats along sheltered sedimentary coasts. As a novel ecological function with high societal relevance, a role of the seagrass leaf canopy for reducing potentially harmful bacteria has recently been hypothesized in tropical regions, but data for temperate regions are lacking. Here, we tested whether or not the abundance of general bacteria and more specifically, those belonging to the genus Vibrio were reduced within temperate Zostera marina (eelgrass) meadows compared to adjacent sand flats and sampled 5 sites in the south-western Baltic Sea using SCUBA. Compared to non-vegetated area, we found an average reduction of 39% for all Vibrio and 63% for the potentially harmful V. vulnificus/cholerae subtype based on robust plate counting data on Vibrio selective agar. The underlying mechanism of the reduction in bacterial load is currently elusive and clearly merits further study. Our results underline the critical importance of seagrasses in maintaining shallow water ecosystem functioning including water quality and provide further motivation for their protection and restoration.

海草是一个由大约 60 种海洋被子植物组成的多系群，是庇护沉积海岸沿线多样化和具有重要功能的海洋栖息地的基础。作为一种具有高度社会相关性的新型生态功能，最近在热带地区假设海草叶冠在减少潜在有害细菌方面的作用，但缺乏温带地区的数据。在这里，我们测试是否丰度一般细菌的和更具体地，那些属于埃希弧菌中温带内减少叶藻（鳗草）草地使用SCUBA相比相邻砂单位和采样5位点在西南部波罗的海. 与非植被区域相比，我们发现所有区域平均减少了 39%弧菌和 63% 的可能有害的创伤弧菌/霍乱亚型基于弧菌选择性琼脂的稳健平板计数数据。减少细菌负荷的潜在机制目前难以捉摸，显然值得进一步研究。我们的研究结果强调了海草在维持浅水生态系统功能（包括水质）方面的重要性，并为它们的保护和恢复提供了进一步的动力。