Marine ecosystem engineers such as seagrasses and bivalves create important coastal habitats sustaining high biodiversity and ecosystem services. Restoring these habitats is difficult due to the importance of feedback mechanisms that can require large-scale efforts to ensure success. Incorporating facilitative interactions could increase the feasibility and success of small-scale restoration efforts, which would limit pressure on donor sites and reduce costs and time associated with restoration. Here, we tested two methods for providing facilitation in small-scale eelgrass (Zostera marina) restoration plots across northern Europe: (1) co-restoration with blue mussels (Mytilus edulis, M. trossulus); and (2) the use of biodegradable establishment structures (BESEs). Eelgrass-mussel co-restoration showed promise in aquaria, where eelgrass growth was nearly twice as high in treatments with medium and high mussel densities than in treatments without mussels. However, this did not translate to higher shoot length or shoot densities in subsequent field experiments. Rather, hydrodynamic exposure limited both eelgrass and mussel survival, especially in the most exposed sites. The use of BESEs showed more potential in enabling small-scale restoration success: they effectively enhanced eelgrass survival and reduced mussel loss, and showed potential for enabling mussel recruitment in one site. However, eelgrass planted in BESE plots along with mussels had a lower survival rate than eelgrass planted in BESE plots without mussels. Overall, we show that though co-restoration did not work at small scales, facilitation by using artificial structures (BESEs) can increase early eelgrass survival and success of small-scale eelgrass and bivalve restoration.

中文翻译：

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将促进性互动纳入小规模鳗草恢复——挑战和机遇

海草和双壳类等海洋生态系统工程师创造了重要的沿海栖息地，以维持高度的生物多样性和生态系统服务。由于反馈机制的重要性，可能需要大规模的努力才能确保成功，因此恢复这些栖息地很困难。纳入促进性互动可以提高小规模恢复工作的可行性和成功率，这将限制捐助地点的压力并减少与恢复相关的成本和时间。在这里，我们测试了两种为整个北欧小规模鳗草 ( Zostera marina ) 恢复地块提供便利的方法：(1) 与蓝贻贝 ( Mytilus edulis , M. trossulus ) 共同恢复); (2) 使用可生物降解的企业结构 (BESE)。鳗草-贻贝共同修复在水族馆中显示出希望，在中等和高密度贻贝的处理中，鳗草的生长速度几乎是没有贻贝的处理的两倍。然而，这并没有在随后的田间试验中转化为更高的枝条长度或枝条密度。相反，水动力暴露限制了鳗草和贻贝的存活，尤其是在暴露最多的地方。BESE 的使用在实现小规模修复成功方面显示出更大的潜力：它们有效地提高了鳗草的存活率并减少了贻贝损失，并显示出在一个地点实现贻贝补充的潜力。然而，与贻贝一起种植在 BESE 地块中的鳗草的成活率低于在没有贻贝的 BESE 地块中种植的鳗草。全面的，