Two decades of monitoring within a temperate marine park shows no-take zone and climate-change impacts on fish, invertebrates and coral cover

Context Marine protected areas are used to conserve biodiversity, but their effectiveness can be affected by climate change. Aims The Port Stephens–Great Lakes Marine Park in Australia was used to examine whether marine park zoning delivers ecological benefits and whether these benefits are affected by climate change. Methods Surveys of rocky reefs were conducted from 2007 to 2024, comparing no-take sanctuary zones (SZs) with adjacent fished habitat protection zones (HPZs). Underwater visual census surveys quantified fish and invertebrates, fish biomass, and coral cover, with multivariate analyses being applied to detect temporal and zoning effects. Key results Analyses identified that targeted fish biomass declined in HPZs but was maintained in SZs, suggesting that no-take zoning reduced fishing impacts. Tropicalisation of fish assemblages was evident and urchin densities declined across all zones. Coral cover and density rose significantly from 2012 to 2024. Conclusions Results indicated that zoning provides increased protection in SZs, compared with HPZs, and conserved biodiversity across all zones. However, zoning has not buffered against the impacts of climate change, which is reshaping ecosystems through tropicalisation of fish and benthic communities. Implications Monitoring, and adaptive management to mitigate climate-change impacts, is essential to assess and maintain biodiversity in marine protected areas.