Influence of entrance regime on vegetation profiles and carbon storage in south-eastern New South Wales ICOLLs

Estuarine vegetation is recognised for its ability to mitigate climate change through carbon sequestration and storage. Within Intermittently Closed and Open Lakes and Lagoons (ICOLLs), cycles of wetting and drying of estuarine vegetation, related to entrance opening and closure (regime), cause changes in vegetation composition and distribution. The influence of entrance regimes on estuarine vegetation and carbon storage has not been widely investigated. Previous studies have focused on carbon storage within open estuaries and tend to ignore spatial variation in estuarine vegetation and, in the case of ICOLLs, the impacts of intermittent entrance regimes on carbon storage. This study aims to establish how different entrance regimes influence estuarine vegetation and associated carbon storage within four NSW ICOLLs. The entrance regime was identified, and the structural and spatial variation in estuarine vegetation was delineated. This was complemented with a soil carbon assessment, which allowed for comparisons between vegetation zones and ICOLLs. Results showed considerable variation in carbon storage both within, and between, the studied ICOLLs. Carbon storage was related to vegetation zones, which varied considerably due to individual characteristics of each ICOLL, including the entrance regime. The relative contribution of vegetation zones to carbon storage was identified, showing substantial carbon storage within Casuarina and/or Melaleuca vegetation zones, a largely unstudied area throughout the literature. The study showed that generalising carbon storage within an estuary or between estuaries may be erroneous due to the high carbon variability within ICOLLs. The study makes a number of recommendations relating to ICOLL management and policy.