Data_Sheet_1_Recolonization Dynamics of Warm Affinity Halophila nipponica in a Temperate Seagrass Meadow With Zostera marina.PDF

Because Halophila nipponica has only recently been reported in the temperate coastal waters of the northwestern Pacific, the recolonization dynamics of this species have not yet been investigated in temperate seagrass meadows. H. nipponica typically occurs in monoculture or in mixed meadows with Zostera marina, the most abundant seagrass species in this region. In this study, un-bordered and bordered gaps (0.5 × 0.5 m) were created in a mixed seagrass meadow of H. nipponica and Z. marina at Namhae Island on the southern coast of Korea to compare recolonization dynamics of the two species. Un-bordered gaps were marked using only a steel stake at each corner, while the margins of the bordered gaps were blocked to a sediment depth of approximately 20 cm using stainless steel blades to prevent penetration of seagrass rhizomes. Shoot densities of Z. marina and H. nipponica were measured in the gaps and in natural reference plots to estimate percent recolonized. In the bordered gaps, a few Z. marina seedlings and H. nipponica fragments were observed during winter, but no shoots of either species survived to the end of experiment. In the un-bordered gaps, the density of H. nipponica increased rapidly, with approximately 60% recovery after 2 months and reaching 85% after 10 months through only asexual reproduction via clonal growth. By contrast, recolonization of Z. marina was much slower than that of H. nipponica, with only approximately 25% recovery after 10 months through vegetative growth and recruitment of a few seedlings. Thus, small fast-growing H. nipponica rapidly recolonized, compared to relatively large slow-growing Z. marina in the small-size gaps. Asexual reproduction was the principle reproductive mechanism for the recolonization of both Z. marina and H. nipponica at the study site. According to our results, gaps created naturally and anthropogenically in mixed seagrass meadows may be primarily recolonized by H. nipponica rather than Z. marina, leading to a change in the seagrass ecosystem structure in Korean coastal waters.

鉴于卤蕨属的日本种（Halophila nipponica）仅在近期被报道出现在西北太平洋温带沿海水域，该物种在温带海草群落中的再殖民动态尚未得到研究。日本种通常以单一栽培或与泽泻属（Zostera marina）混合在海草群落中，后者是该地区最丰富的海草物种。在本研究中，于韩国南部海岸的南浔岛上的日本种和泽泻属混合海草群落中，通过创建无边界和有边界的缺口（0.5 × 0.5 米）来比较两种物种的再殖民动态。无边界缺口仅在每个角落使用钢桩标记，而有边界缺口的边缘则用不锈钢刀片阻隔至约20厘米的沉积物深度，以防止海草根茎的穿透。在缺口和自然参考样地中测量了泽泻属和日本种的植株密度，以估算再殖民百分比。在有边界缺口中，冬季观察到一些泽泻属幼苗和日本种碎片，但两种物种的植株均未在实验结束时存活。在无边界缺口中，日本种的密度迅速增加，仅通过无性繁殖，通过克隆生长，两个月后恢复约60%，十个月后恢复至85%。相比之下，泽泻属的再殖民速度远慢于日本种，十个月后仅通过营养生长和少数幼苗的萌发，恢复约25%。因此，相对于生长较慢且体型较大的泽泻属，体型较小且生长快速的日本种在小尺寸缺口中迅速再殖民。无性繁殖是该研究地点泽泻属和日本种再殖民的主要繁殖机制。根据我们的研究结果，混合海草群落中自然形成和人为形成的缺口可能主要被日本种而非泽泻属再殖民，导致韩国沿海水域海草生态系统结构的改变。