Cross-domain biodiversity effects: linking diatom species and intraspecific richness, bacterial diversity, and biomass production

Interactions between bacteria and microalgae are important for the functioning of aquatic ecosystems, yet interactions based on the biodiversity of these two domains are relatively unknown. Specifically, it is unclear whether a positive biodiversity-productivity relationship in phytoplankton is largely facilitated by niche partitioning among the phytoplankton organisms themselves, or whether associated bacterial communities play an additional role in modifying these diversity effects. Moreover, effects of intraspecific diversity in phytoplankton communities on bacterial community diversity have not been tested. We factorially manipulated both species and intraspecific richness of three diatoms to test effects on biomass production and bacterial diversity of algae-bacteria communities. The results show that diatom intraspecific diversity has significant positive effects on culture biomass and the diversity of the associated free-living bacterial community, which are comparable in magnitude to species diversity effects. However, there were little to no effects of diatom diversity on attached/particle-associated bacterial diversity, or of bacterial diversity on biomass production. These results suggest a decoupling of bacterial diversity from the diatom diversity-productivity relationship and provide early insights regarding the relations between diversity across domains in aquatic ecosystems.

细菌与微藻的相互作用对水生生态系统的功能运转至关重要，但针对这两类生物域的生物多样性互作研究仍相对匮乏。
具体而言，目前尚不明确浮游植物（phytoplankton）正向的生物多样性-生产力关系，究竟主要由浮游植物自身的物种生态位分化所驱动，还是由相关联的细菌群落通过调控此类多样性效应来额外促成。此外，浮游植物群落的种内多样性对细菌群落多样性的影响尚未得到实验验证。
本研究采用析因实验设计，调控了3种硅藻（diatoms）的物种丰富度与种内丰富度，以此探究其对藻菌共生群落的生物量生产与细菌多样性的影响。
研究结果显示，硅藻的种内多样性对培养体系的生物量以及相关联的自由生活型细菌群落多样性均具有显著正向影响，其效应强度与物种多样性的影响相当。
但硅藻多样性对附着型/颗粒结合型细菌多样性几乎无影响，细菌多样性对生物量生产也未产生显著作用。
上述结果表明，细菌多样性与硅藻多样性-生产力关系之间存在解耦现象，同时为探究水生生态系统中跨域生物多样性之间的关联提供了初步的研究视角。