Environmental and Marine Biology, Faculty of Science and Engineering, Åbo Akademi University, Åbo, Finland.
University of Gothenburg, Department of Marine Sciences, Fiskebäckskil, Sweden.
PLoS One. 2019 Sep 3;14(9):e0222020. doi: 10.1371/journal.pone.0222020. eCollection 2019.
Propagule dispersal is an integral part of the life cycle of seagrasses; important for colonising unvegetated areas and increasing their spatial distribution. However, to understand recruitment success, seed dispersal and survival in habitats of different complexity remains to be quantified. We tested the single and synergistic effects of three commonly distributed ecosystem engineers-eelgrass (Zostera marina), oysters (Magellana gigas) and blue mussels (Mytilus edulis)-on trapping of Z. marina seeds in a hydraulic flume under currents. Our results suggest that seed retention increases with habitat complexity and further reveal insights into the underlying mechanisms. In eelgrass canopy, trapping occurred mostly through direct blocking of a seed's pathway, while trapping in bivalve patches was mainly related to altered hydrodynamics in the lee side, i.e. behind each specimen. With increasing flow velocity (24-30 cm s-1 in eelgrass canopy, 18-30 cm s-1 in bivalve patches), modifications of the sediment surface through increased turbulence and erosive processes became more important and resulted in high seed trapping rates. Furthermore, we show that while monospecific patches of seagrass and bivalves had different trapping optima depending on flow velocities, intermixing resulted in consistently high trapping rates throughout the investigated hydrodynamic gradient. Our results highlight the importance of positive interactions among ecosystem engineers for seed retention and patch emergence in eelgrass.
扩散体是海草生命周期的一个组成部分；对于开拓无植被地区和增加其空间分布很重要。然而，为了了解繁殖成功、种子传播和在不同复杂程度的栖息地中的生存情况，仍需要进行量化研究。我们在水流作用下的水力水槽中，测试了三种常见的生态系统工程师——鳗草（Zostera marina）、牡蛎（Magellana gigas）和贻贝（Mytilus edulis）——对鳗草种子捕获的单一和协同作用。我们的研究结果表明，随着栖息地复杂性的增加，种子保留率增加，并进一步揭示了潜在的机制。在鳗草冠层中，捕获主要通过直接阻挡种子的路径来实现，而在双壳类斑块中的捕获主要与背风侧（即每个标本的背面）的水动力变化有关。随着流速的增加（鳗草冠层中为 24-30cm/s，双壳类斑块中为 18-30cm/s），通过增加湍流和侵蚀过程对沉积物表面的修改变得更加重要，从而导致高种子捕获率。此外，我们还表明，虽然单一种群的海草和双壳类斑块具有不同的捕获最佳流速，但混合后，在整个研究的水动力梯度中始终保持较高的捕获率。我们的研究结果强调了生态系统工程师之间的积极相互作用对于鳗草中种子保留和斑块出现的重要性。
