Passive acoustic monitoring tools have the potential to provide insights into community structure as devices can autonomously collect data on the acoustic presence of species. Data can provide information on local species diversity, residency times and patterns in species co-occurrence. Here, we apply multiple biodiversity measures to explore how marine mammal community composition develops over time using information derived from multi-year passive acoustic data from 6 sites throughout the Atlantic sector of the Southern Ocean, the Weddell Sea. Overall species richness showed relatively little variation over time, showing that a substantial number of species remains in Antarctic waters throughout austral winter, but community composition showed almost complete seasonal overturn, recognizing that species replace each other throughout the year. For all 6 sites, community dissimilarity increased with increasing temporal distance reflecting temporal trends in community composition beyond seasonality. Species co-occurrence analyses showed that a number of species exhibited either consistently positive or negative relations, while at the recording site off the Western Antarctic Peninsula, some relations were inversed compared to the oceanic sites. Patterns in co-occurrence are suggestive of predator-prey relationships between species, inter-specific interference with respect to prey species as well as acoustic interference between co-occurring marine mammal species.