In 1987, the most comprehensive historical record of seagrass distribution in the Noosa River estuary in Southeast Queensland was completed, finding 47 ha of dense and 923 Ha of sparse and patchy seagrass. In November 2020, the seagrass distribution and condition was assessed throughout the estuary, using a combination of direct assessment, and remote georeferenced photo transects and spot checks. The predominantly sandy estuary still has several large seagrass meadows dominated by eel grass (Zostera muelleri sub sp. capricorni) and occasional sparse patches of Halophila ovalis, covering 56 ha of seagrass. However, there was an 83% decline in total extent between 1987 and 2020.
To assess historical changes and resilience of seagrass throughout the estuary, the distribution was mapped from suitable orthorectified aerial and satellite imagery from 1989, 2006, and 2008-2009. A stepwise decline in some reaches occurred over time; however, the response to environmental stressors differed among reaches, due likely to differences in environmental stressors across the estuary. This provided an opportunity to assess the likely mechanisms of decline in seagrass over the past 30 years that will inform future management initiatives to maximise natural or assisted recovery of seagrass and to improve seagrass resilience to future environmental changes.