Spatial and temporal dynamics of microbial communities under environmental perturbation

微底栖植物及其伴生的原核生物是浅海沉积物底栖生物食物网的基础。这些微生物群落的生物量和组成在时间和空间尺度上变化很大。特别是在东南沿海地区，由于潮汐和频繁的干扰，如热浪或暴雨洪水，导致环境条件迅速变化。基于其巨大的性状变异，微生物群落使用各种策略来应对这种变化的环境，包括在沉积物中的垂直迁移。然而，在这种动态景观中，物种相互作用与空间结构群落特征分布之间的关系仍然缺乏理解，这阻碍了我们对这些群落如何应对环境变化的预测能力。因此，在DynaCom的第二阶段，我们的项目追求两个主要目标：1)评估自然环境波动和随机干扰对Spiekeroog背障潮滩底栖海洋食物网微生物群落时空特征分布和功能的影响；2)具体了解MPB、原核生物和大型底栖动物消费者（MZB, SP 5）对热浪响应的特征相互作用。考虑到全球变化下瓦登海生态系统中微生物食物网的巨大功能相关性。我们将在项目第一年的春季和夏季在Spiekeroog的潮滩进行实地采样活动，以确定在高度变化的浅海和更稳定的浅海地带，微生物群落和MZB（与SP 5合作）的空间（沉积物垂直）和时间（超过日和潮汐周期）周转。然后，中观实验将用于研究在不同放牧制度下（放牧者在流动性和压力适应方面存在差异），原核生物、MPB和MZB之间相互作用对热浪的响应变化。伴随的实验室生物分析将进行，以获得生物体的特定特征（例如，耐温性，可食性），以促进我们对在中观实验和现场观察到的相互作用动力学的理解。此外，在项目的最后阶段，我们将确定Spiekeroog实验岛屿上的微生物群落的稳定性，以应对冬季风暴和潮汐强迫引起的物理干扰。

Microphytobenthos (MPB) and their associated prokaryotes provide the basis of the benthic food web in shallow coastal marine sediments. These microbial communities are highly variable in biomass and composition on temporal and spatial scales. Especially the eulittoral is characterized by rapidly changing environmental conditions induced by the tides and frequent disturbances such as heatwaves or storm floods. Based on their large trait variation, microbial communities use various strategies to cope with this variable environment, including vertical migration in the sediment. However, there is still a substantial lack of understanding of how species interactions relate to trait distribution of spatially structured communities in such dynamic landscapes, hampering our predictive capacity of how these communities will respond to environmental change.In the second phase of DynaCom, our project therefore pursues two major goals: 1) to evaluate the effect of natural environmental fluctuations and stochastic disturbances on the temporal and spatial trait-based distribution and functioning of microbial communities in a benthic marine food web of the backbarrier tidal flat on Spiekeroog, and 2) to specifically understand the trait-based interactions of MPB, prokaryotes and macrozoobenthos consumers (MZB, SP 5) in response to a heatwave, given the large functional relevance of microbial food webs in the Wadden Sea ecosystem under global change. We will conduct field sampling campaigns in the tidal flat on Spiekeroog in spring and summer of the first year of the project to determine spatial (vertical in the sediment) and temporal (over diurnal and tidal cycles) turnover of microbial communities and MZB (in collaboration with SP 5) in the highly variable eulittoral and the more stable sublittoral zone. Mesocosm experiments will then serve to investigate changes in the interactions between prokaryotes, MPB and MZB in response to a heatwave under different grazing regimes (grazers differing in mobility and stress-adaptation). Accompanying laboratory bioassays will be conducted to derive specific traits of the organisms (e.g. temperature tolerance, edibility) to foster our understanding of the interactive dynamics observed in the mesocosm experiments and in the field. Furthermore, we will determine the stability of microbial communities at the experimental islands on Spiekeroog in response to physical disturbances induced by winter storms and tidal forcing after the deconstruction of the wave breakers in the last phase of the project.