Instituto de Investigaciones Marinas (IIM), CSIC, C/Eduardo Cabello 6, 36208, Vigo, Spain.
Laboratoire des Sciences de l'Environnement Marin, UMR 6539, Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, 29280, Plouzané, France.
Sci Rep. 2023 Jan 20;13(1):1178. doi: 10.1038/s41598-023-27411-y.
Diatoms play a key role in the marine silica cycle, but recent studies have shown that sponges can also have an important effect on this dynamic. They accumulate large stocks of biogenic silica within their bodies over long periods, which are thought to vary little on an intra-annual scale. The observation of an abrupt decline in sponge biomass in parallel with large increases in abundance of a spongivorous nudibranch (Doris verrucosa) led us to conduct a year-long study on the effect of nudibranch predation on the silicon budget of a sponge (Hymeniacidon perlevis) population. After 5 months of predation, the abundance of sponge individuals did not change but their biomass decreased by 95%, of which 48% was explained by nudibranch predation. About 97% of sponge spicules ingested by nudibranchs while feeding was excreted, most of them unbroken, implying a high rate of sponge silica deposition in the surrounding sediments. After predation, sponges partially recovered their biomass stocks within 7 months. This involved a rapid growth rate and large assimilation of dissolved silicon. Surprisingly, the highest rates of silicon absorption occurred when dissolved silicon concentration in seawater was minimal (< 1.5 µM). These findings suggest that the annual sponge predation-recovery cycle triggers unprecedented intra-annual changes in sponge silicon stocks and boosts the cycling of this nutrient. They also highlight the need for intra-annual data collection to understand the dynamics and resilience of sponge ecosystem functioning.
硅藻在海洋硅循环中起着关键作用，但最近的研究表明，海绵也可能对这一动态产生重要影响。它们在很长一段时间内会在体内积累大量的生物硅，这些硅的积累量在年内的变化很小。我们观察到海绵生物量的突然下降与食海绵的裸鳃类动物（Doris verrucosa）丰度的大幅增加同时发生，这促使我们对裸鳃类动物捕食对海绵（Hymeniacidon perlevis）种群硅预算的影响进行了为期一年的研究。在 5 个月的捕食后，海绵个体的丰度没有变化，但它们的生物量减少了 95%，其中 48%是由裸鳃类动物捕食造成的。当裸鳃类动物在进食时摄入的海绵骨针中，约有 97%被排泄出来，其中大部分没有破碎，这意味着周围沉积物中有很高的海绵硅沉积率。捕食后，海绵在 7 个月内部分恢复了生物量储备。这涉及到快速的生长速度和大量溶解硅的同化。令人惊讶的是，当海水中溶解硅的浓度最低（<1.5µM）时，硅的吸收速率最高。这些发现表明，每年的海绵捕食-恢复周期会引发海绵硅储量前所未有的年内变化，并促进了这种营养物质的循环。它们还强调了需要进行年内数据收集，以了解海绵生态系统功能的动态和弹性。
