The seaweed Caulerpa cylindracea (Sonder) is one of the most successful marine bioinvaders worldwide. Caulerpa cylindracea can influence the quantity and biochemical composition of sedimentary organic matter (OM). However, it is still unknown if the effects of C. cylindracea on both OM and small metazoans (i.e. meiofauna) can change according to different sediment deposition rates. To provide insights on this, we investigated the biochemical composition of sediments along with the abundance and composition of meiofaunal assemblages in sediments colonized and not-colonized by the seaweed C. cylindracea under different regimes of sediment deposition. Our results show that the presence of the invasive alga C. cylindracea could alter quantity, biochemical composition, and nutritional quality of organic detritus and influence the overall functioning of the benthic system, but also that the observed effects could be context-dependent. In particular, we show that the presence of C. cylindracea could have a positive effect on meiofaunal abundance wherever the sediment deposition rates are low, whereas the contextual presence of high to medium sedimentation rates can provoke an accumulation of sedimentary organic matter, less favourable bioavailability of food for the benthos, and consequent negative effects on meiofauna.

海藻Caulerpa cylindracea（Sonder）是全球最成功的海洋生物入侵者之一。Caulerpa cylindracea可以影响沉积有机物（OM）的数量和生化组成。然而，仍然不确定圆头梭菌对OM和小型后生动物（即meiofauna）的影响是否会根据不同的沉积物沉积速率而改变。为了提供有关此方面的见解，我们调查了在不同沉积物沉积方式下，由海藻C. cindindracea定殖和未定殖的沉积物中的沉积物的生化组成以及藻类组合的丰度和组成。我们的结果表明，入侵藻类C. cindindracea的存在可能会改变有机碎屑的数量，生化成分和营养质量，并影响底栖系统的整体功能，而且所观察到的影响可能与环境有关。特别是，我们表明，存在C. cylindracea的可能对meiofaunal丰度具有积极作用的任何地方泥沙淤积率很低，而高至中等沉积速率的上下文存在可引发沉积有机质的积累，不太有利的生物利用度底栖动物的食物，对鱼类的负面影响。