Parasitism in ecosystem engineer species: a key factor controlling marine ecosystem functioning

1. Although parasites represent a substantial part of marine communities’ biomass and diversity, their influence on ecosystem functioning, especially via the modification of host behaviour, remains largely unknown. Here, we explored the effects of the bopyrid ectoparasite Gyge branchialis on the engineering activities of the thalassinid crustacean Upogebia pusilla and the cascading effects on intertidal ecosystem processes (e.g. sediment bioturbation) and functions (e.g. nutrient regeneration).

2. Laboratory experiments revealed that the overall activity level of parasitized mud shrimp is reduced by a factor 3.3 due to a decrease in time allocated to burrowing and ventilating activities (by a factor 1.9 and 2.9 respectively).

3. Decrease in activity level led to strong reductions of bioturbation rates and biogeochemical fluxes at the sediment-water interface.

4. Given the worldwide distribution of mud shrimp and their key role in biogeochemical processes, parasite-mediated alteration of their engineering behaviour has undoubtedly broad ecological impacts on marine coastal systems functioning.

5. Our results illustrate further the need to consider host-parasite interactions (including trait-mediated indirect effects) when assessing the contribution of species to ecosystem properties, functions and services.

Methods
For more details, please see section 2. Materials and methods in the paper.

1. 尽管寄生虫在海洋群落的生物量与多样性中占据可观份额，但其对生态系统功能的影响，尤其是通过修饰宿主行为所介导的作用，在很大程度上仍未得到充分解析。本研究探讨了鳃虱类（bopyrid）外寄生虫Gyge branchialis对蝼蛄虾总科甲壳动物Upogebia pusilla的生态工程活动的影响，及其对潮间带生态系统过程（如沉积物生物扰动）与功能（如营养盐再生）的级联效应。
2. 室内实验结果显示，被寄生的泥虾整体活动水平降至原水平的1/3.3，这是由于其分配至掘穴与通风活动的时间分别减少至原水平的1/1.9与1/2.9。
3. 活动水平的下降显著降低了沉积物-水界面的生物扰动速率与生物地球化学通量。
4. 鉴于泥虾在全球范围内广泛分布，且在生物地球化学过程中发挥关键作用，寄生虫介导的其生态工程行为改变，无疑会对海洋沿岸系统的功能产生广泛的生态影响。
5. 本研究结果进一步表明，在评估物种对生态系统属性、功能与服务的贡献时，需纳入宿主-寄生虫相互作用（包括性状介导的间接效应）的考量。
研究方法
如需获取详细实验步骤，请参见本文第2节“材料与方法”。