Billabongs or oxbow lakes are important wetland ecosystems with immense ecological and cultural value. River connectivity drives their ecological structure and function, but the connectivity of many billabongs has been reduced by channel modification and flow regulation. Here, we investigate how billabong connection, from natural and managed (environmental watering by Melbourne Water Corporation) high flow events in the lower Birrarung (Yarra River, Victoria), impacts dissolved oxygen concentrations and ecosystem metabolism. We collected near continuous data for dissolved oxygen and water temperature in the epilimnion of three urban billabongs from October 2023 until April 2024, each with different connection regimes. We also collected continuous weather data (e.g. irradiance, wind, humidity, rainfall) from floating weather stations which enabled us to model ecosystem metabolism before and after connection events. The impact of billabong connection on dissolved oxygen concentrations was variable and likely influenced by flood peak, the degree of stratification prior to connection, and ecosystem metabolism dynamics. All three billabongs were largely heterotrophic (net ecosystem production < 0 mg O2 L-1 d-1) throughout the study period. The impact of connection events on billabong ecosystem metabolism was variable, but gross primary production was often suppressed relative to the pre-connection period. This project has provided important insights into the immediate biogeochemical and ecological impacts of billabong flooding. Future work should focus on the longer-term and broader ecological impact of billabong flooding, including consequences for aquatic food-webs, which will inform future environmental water management.