Since there is no local management for Marine Protected Areas (MPAs) to prevent the establishment of macroalgae NIS, successful efforts to contrast their spread probably should concentrate in the conservation of resistant habitats. The study aimed to evaluate the role of depth and habitat in the spread of macroalgal non-indigenous species (NIS). A multifactorial sampling design was employed to compare the abundance of NIS macroalgae over a one-year period across different substrates and depths within a Mediterranean MPArea. Moreover, the ecological quality of macroalgal assemblages in relation to invasion was assessed through the ALien Biotic IndEX (ALEX). The NIS macroalgae found in the MPA, Caulerpa cylindracea, Acrothamnion preissii, Womersleyella setacea and Falkenbergia sp., were overall quite low in abundance and, accordingly, the ALEX index had generally high values. The substrate, depth and time significantly affected NIS abundance; however, the lack of significant interannual variability (December 2018–December 2019), both in pooled and separated NIS abundance, suggested that the occurrence of these four NISs will no further expand in the MPA at the scale of habitat. The highlighted patterns in NIS abundance suggest the importance of detailed sampling designs of monitoring taking into consideration different habitats and depths and using suitable sampling methods to assess NIS establishment and spread, such as those required by international directives.

由于没有海洋保护区（MPA）的本地管理机构来防止大型藻类NIS的建立，因此对比它们的扩散的成功努力可能应该集中在耐性生境的保护上。该研究旨在评估深度和栖息地在大型藻类非本地物种（NIS）传播中的作用。采用多因素采样设计来比较地中海MPArea中一年中跨不同底物和深度的NIS大型藻类的丰度。此外，通过ALien Biotic IndEX（ALEX）评估了与入侵有关的大型藻类组合的生态质量。在MPA，Caulerpa cylindracea，Acrothamnion preissii，Womersleyella setacea中发现的NIS大型藻类和Falkenbergia sp。的丰度总体较低，因此，ALEX指数通常具有较高的值。基质，深度和时间会显着影响NIS的丰度；但是，在合并和分离的NIS数量方面都没有重大的年际变化（2018年12月至2019年12月），这表明这四个NIS的发生在栖息地范围内在MPA中不会进一步扩大。NIS丰富度中突出显示的模式表明，监测的详细抽样设计的重要性，要考虑到不同的生境和深度，并使用适当的抽样方法来评估NIS的建立和传播，如国际指令所要求的。