Department of Biology, University of Pisa, via Derna 1, 56126 Pisa, Italy.
Department of Biology, University of Pisa, via Derna 1, 56126 Pisa, Italy.
Sci Total Environ. 2021 Feb 25;757:143812. doi: 10.1016/j.scitotenv.2020.143812. Epub 2020 Nov 19.
Plastics are found in marine environments worldwide, and their effects on macrophytes (seagrasses and macroalgae) colonizing sandy bottoms are still poorly known. Seagrass meadows are valuable but declining ecosystems due to local and global-change related stressors, including sediment disturbance and introduced macroalgae. Understanding whether plastics pose a further threat to seagrasses is critically important. In two simultaneous additive experiments performed in an aquaculture tank, we examined the individual and combined effects of macroplastics (non-biodegradable high-density polyethylene and biodegradable starch-based) and sedimentation (no and repeated sedimentation) on the performance (in terms of biomass and architectural variables) of a native Mediterranean seagrass (Cymodocea nodosa) and an introduced macroalga (Caulerpa cylindracea), and on the intensity of their interactions. Macroplastics were still present in sediments after 18 months. Cymodocea nodosa produced a greater biomass and longer horizontal rhizome internodes forming clones with more spaced shoots probably to escape from plastics. Plastics prevented C. nodosa to react to sedimentation by increasing vertical rhizome growth. Under C. cylindracea invasion, C. nodosa allocated more biomass to roots, particularly to fine roots. In the presence of C. nodosa, C. cylindracea performance was reduced. High-density polyethylene (HDPE) plastic and sedimentation shifted species interactions from competitive to neutral. These results suggest that both HDPE and biodegradable starch-based macroplastics, if deposited on marine bottoms, could make seagrasses vulnerable to sedimentation and reduce plant cover within meadows. HDPE plastic and sedimentation could contribute to the decline of seagrass habitats by facilitating the spread of non-native macroalgae within meadows. Overall, the study highlights the urgent need to implement more effective post-marketing management actions to prevent a further entering of plastics in natural environments in the future, as well as to establish to conservation measures specifically tailored to protect seagrass habitats from plastic pollution.
塑料在全球的海洋环境中都有发现，其对在沙质底部定殖的大型植物（海草和大型藻类）的影响仍知之甚少。由于包括沉积物干扰和引入的大型藻类在内的地方和全球变化相关胁迫，海草草甸是有价值但正在减少的生态系统。了解塑料是否对海草构成进一步威胁至关重要。在水产养殖箱中同时进行的两项附加实验中，我们研究了大型塑料（不可生物降解的高密度聚乙烯和可生物降解的淀粉基）和沉降（无沉降和重复沉降）对本地地中海海草（Cymodocea nodosa）和引入的大型藻类（Caulerpa cylindracea）的性能（生物量和结构变量）的单独和联合影响，以及它们相互作用的强度。18 个月后，沉积物中仍存在大型塑料。Cymodocea nodosa 产生的生物量更大，水平根茎节间更长，形成的克隆具有更多间隔的芽，可能是为了逃避塑料。塑料通过增加垂直根茎生长，使 C. nodosa 无法对沉降做出反应。在 C. cylindracea 入侵的情况下，C. nodosa 将更多的生物量分配到根部，特别是细根。在存在 C. nodosa 的情况下，C. cylindracea 的表现会降低。高密度聚乙烯（HDPE）塑料和沉降将物种间的相互作用从竞争转为中性。这些结果表明，如果沉积在海底，高密度聚乙烯和可生物降解的淀粉基大型塑料都可能使海草容易受到沉降的影响，并减少草地内的植物覆盖率。HDPE 塑料和沉降可能会通过促进非本地大型藻类在草地内的传播，导致海草栖息地的减少。总的来说，该研究强调迫切需要实施更有效的上市后管理行动，以防止未来更多的塑料进入自然环境，以及制定专门针对保护海草栖息地免受塑料污染的保护措施。
