Patches of decomposing macroalgae can be beneficial to intertidal regions, providing habitat and food, or can create anoxic conditions inhospitable to benthic organisms. These opposing outcomes warrant further investigations into biotic-abiotic processes associated with macroalgae. Here, differences in surface sediment erosion measures (erosion threshold (Ʈc; N m−2), erosion rate (ER; g m−2 s−1), and sub-surface erosion rates (me; g N−1 s−1)) were examined at sites dominated by the suspension-feeding clam or deposit-feeding bivalve (Austrovenus stutchburyi and Macomona liliana, respectively) after 30 days of exposure to decomposing macroalgae (Ulva spp.). The Austrovenus site was chosen to represent a species-rich, functionally diverse macrofaunal community. The nearby Macomona site had similar sediment characteristics, yet had a less abundant and diverse faunal community. Despite the equal amounts of Ulva recovered from both sites (< 3% of the initial 3 kg wet weight m−2 added), differences in surface erosion were measured. One day after Ulva removal, an initial increase in surface erosion (−Ʈc and +ER) was measured at the Austrovenus site, but after 14 days there was no difference compared with control plots. At the Macomona site, Ulva addition stabilized sediments (+Ʈc and -ER), an effect that persisted for 14 days. These differences were reflected in the macrofaunal community. At the Austrovenus site, the macrofaunal community recovered within 14 days whereas differences between Ulva and controls persisted at the Macomona site. This work emphasizes how subtle differences in benthic community composition and recovery can result in spatial and temporal variations in sediment erosion potential on intertidal sandflats.

中文翻译：

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分解大型藻类 (Ulva spp.) 影响底栖大型动物群和表层沉积物侵蚀

腐烂的大型藻类斑块可能对潮间带区域有益，提供栖息地和食物，或者可能造成不适合底栖生物生存的缺氧条件。这些相反的结果需要进一步研究与大型藻类相关的生物非生物过程。在这里，表层沉积物侵蚀测量的差异（侵蚀阈值（Ʈc；N m−2）、侵蚀率（ER；gm−2 s−1）和地下侵蚀率（me；g N−1 s−1） ) 在暴露于腐烂的大型藻类 (Ulva spp.) 30 天后，在以悬浮喂养的蛤蜊或沉积喂养的双壳类动物（分别为 Austrovenus stutchburyi 和 Macomona liliana）为主的地点进行了检查。选择 Austrovenus 站点代表物种丰富、功能多样的大型动物群落。附近的马科莫纳遗址具有相似的沉积特征，但动物群落的数量和多样性较少。尽管从两个地点回收了等量的石莼（<最初添加的 3 kg 湿重 m-2 的 3%），但仍测量了表面侵蚀的差异。去除石莼后一天，在 Austrovenus 站点测量到表面侵蚀（-Ʈc 和 +ER）的初始增加，但 14 天后与对照地块相比没有差异。在马科莫纳遗址，石莼添加物稳定了沉积物（+Ʈc 和 -ER），这种效果持续了 14 天。这些差异反映在大型动物群落中。在 Austrovenus 站点，大型动物群落在 14 天内恢复，而在 Macomona 站点，石莼和对照之间的差异仍然存在。