The influence of bioturbator activity on sediment bacterial structure and function is moderated by environment.

Bioturbation in coastal sediments plays a crucial role in biogeochemical cycling. However, a key knowledge gap is the extent to which bioturbation influences bacterial community diversity and ecosystem processes, such as nitrogen cycling. This study paired bacterial diversity, bioturbation activity and in situ flux measurements of oxygen and nitrogen from bioturbated sediments at six estuaries along the East coast of Australia. Bacterial community diversity, composition and predicted functional profiles were similar across burrow and surface sediments but were significantly influenced by bioturbator activity (measured as number of burrows) at sites with higher fine grain content. Sediment oxygen demand increased with bioturbator activity but changes in nitrogen cycling (as measured by fluxes and predicted bacterial functional gene analysis) were more spatially variable and were unrelated to bioturbator activity and bacterial community shifts. This study highlights how bioturbator activity influences bacterial community structure and functioning and what implications this has for biogeochemical cycles in estuarine sediments.