De Battisti Davide, Balestri Elena, Pardi Giuseppina, Menicagli Virginia, Lardicci Claudio
Department of Biology, University of Pisa, Pisa, Italy.
Department of Earth Science, University of Pisa, Pisa, Italy.
Front Plant Sci. 2021 May 7;12:660658. doi: 10.3389/fpls.2021.660658. eCollection 2021.
Epiphytes colonizing adult seagrasses highly contribute to seagrass ecosystem functioning and plant growth. Yet, little information exists on epiphytic communities developing on seagrass seedlings. Moreover, for some species our knowledge about seedling performance is limited to early establishment phases, and the role of substrate type in affecting their growth is still unclear. These are considerable knowledge gaps, as seedlings play an important role in meadow expansion and recovery from disturbance. In this study, seedlings of , a keystone species of the Mediterranean, were grown in a shallow (1.5 m deep) coastal area along the Tuscany coast (Italy). After five years of growth (July 2009), seedlings were collected and, through multivariate analysis, we examined whether the epiphytic communities of leaves (both internal and external side) and rhizomes, as well as the growth characteristics differed between rock and sand substrate. The epiphytic communities of seedlings largely reflected those found on adult shoots. Epiphyte cover was similar between the two leaf sides, and it was higher on seedlings grown on rock than on sand, with encrusting algae dominating the community. No differences in epiphyte cover and community structure on rhizomes were found between substrates. Seedling growth characteristics did not differ between substrates, apart from the number of standing leaves being higher on rock than on sand. No correlation was found among epiphyte communities and seedling growth variables (i.e., leaf area, maximum leaf length, number of leaves, total number of leaves produced, rhizome length, total biomass, and root to shoot biomass ratio). Results indicate that epiphytes successfully colonize seedlings, and the surrounding micro-environment (i.e., substrate type) can influence the leaf epiphytic community. This study provides new valuable insights on the biological interactions occurring in seagrass ecosystems and highlights the need for better understanding the effects of seedling epiphytes and substrate on the formation of new meadows.
附生植物在成年海草上的定殖对海草生态系统功能和植物生长有很大贡献。然而，关于海草幼苗上附生群落发育的信息却很少。此外，对于一些物种，我们对其幼苗性能的了解仅限于早期建立阶段，而且基质类型对其生长的影响仍不清楚。这些都是相当大的知识空白，因为幼苗在草甸扩张和从干扰中恢复方面起着重要作用。在本研究中，地中海的关键物种的幼苗在意大利托斯卡纳海岸的浅海（1.5米深）沿海区域生长。经过五年的生长（2009年7月），收集了幼苗，并通过多变量分析，我们研究了叶片（内外侧）和根茎的附生群落以及岩石和沙子基质上的生长特征是否存在差异。幼苗的附生群落很大程度上反映了在成年枝条上发现的群落。叶片两侧的附生植物覆盖率相似，在岩石上生长的幼苗上的附生植物覆盖率高于沙子上的，结壳藻类在群落中占主导地位。不同基质上根茎的附生植物覆盖率和群落结构没有差异。除了直立叶片数量在岩石上高于沙子上外，不同基质上的幼苗生长特征没有差异。在附生群落和幼苗生长变量（即叶面积、最大叶长、叶片数量、产生的叶片总数、根茎长度、总生物量以及根与茎生物量比）之间未发现相关性。结果表明附生植物成功定殖在幼苗上，周围的微环境（即基质类型）会影响叶片附生群落。这项研究为海草生态系统中发生的生物相互作用提供了新的有价值的见解，并强调了更好地理解幼苗附生植物和基质对新草甸形成影响的必要性。
