Nitrogen-cycling genes in oyster reefs and surrounding sediments: Relationships with environmental factors and respective nitrogen rates.

To investigate nitrogen (N) cycling in oyster reef habitats along the East coast of Australia, we assessed N-cycling gene abundances in oyster shell biofilms and surrounding sediments, and explored their correlation with environmental factors and respective N rates. We found higher abundances of the denitrification gene nosZII in oyster shell biofilms, while there were not significant differences in the denitrification genes nirS and nirK between oyster biofilms and sediments. Additionally, oyster shell biofilms had a lower (nirS + nirK)/nosZII ratio, indicating a greater capacity for N removal and limited nitrous oxide release compared to sediments.

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.

Influence of habitat features on the colonisation of native and non-indigenous species.

Marine artificial structures provide substrates on which organisms can settle and grow. These structures facilitate establishment and spread of non-indigenous species, in part due to their distinct physical features (substrate material, movement, orientation) compared to natural habitat analogues such as rocky shores, and because following construction, they have abundant resources (space) for species to colonise. Despite the perceived importance of these habitat features, few studies have directly compared distributions of native and non-indigenous species or considered how functional identity and associated environmental preferences drive associations.

Recruitment of a threatened foundation oyster species varies with large and small spatial scales.

Understanding how habitat attributes (e.g., patch area and sizes, connectivity) control recruitment and how this is modified by processes operating at larger spatial scales is fundamental to understanding population sustainability and developing successful long-term restoration strategies for marine foundation species-including for globally threatened reef-forming oysters.