Host-associated microbiomes (bacteria, archaea and small eukaryotes, represented by meiofauna, unicellular algae and fungi), can influence the fitness of their host and its susceptibility to environmental conditions and changes in various ways. They can alter the development and physiology of the host, promote disease resistance, increase the host's tolerance to stress and drought and modulate the niche spectrum. Due to their rapid replication, microbes can influence the phenotypic plasticity of their hosts very quickly - much faster than eukaryotic hosts can adapt through genetic recombination and natural selection. Therefore, host-associated microbiomes can serve as accelerators of the adaptability of eukaryotes to changing environmental conditions. To date, most microbiome studies have been conducted on individual hosts or specific environmental compartments. This limits a comprehensive understanding of the processes and functions carried out by the microbiome and its seasonal and spatial dynamics at the ecosystem level. In the previous phase of DynaCom, we performed metagenomic analyses along the land-sea gradient in addition to metabarcoding approaches to identify microbiome complexes of plants, beetles, polychaetes, soil and sediment from a highly dynamic coastal area in the Wadden Sea. We found that seasonality has the greatest influence, followed by zonation along the land-sea gradient, tides and finally circadian rhythms. Excitingly, we found the same bacterial strain Endozoicomonas in polychaetes after a natural heat stress, which presumably influences the heat resistance of corals.
In synthesis subproject 3 (SYN 3), we now want to determine and compare the similarities and differences of the analysed microbiomes from different zones and hosts at the land-sea transition. We will analyse the functional characteristics of microbiomes from hosts exposed to different temperatures, salinities and disturbances. To our knowledge, this is the first attempt to push the boundaries of microbiome analysis from single species to the ecosystem level to gain a holistic understanding of the potential abilities of specific microbiomes to improve the resilience of their hosts.