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Caulerpa filiformis is a green seaweed found in New South Wales (NSW, Australia), South Africa, Mozambique and Peru. It has been suggested that the abundance of the species has increased in NSW over recent decades. Extensive aerial and diver surveys identified a 500-km northerly extension to the range of C. filiformis in NSW (to 28°21′S) compared with previous records. The alga has a disjunct distribution with small isolated populations around rocky headlands in far northern NSW, but then no apparent populations for 350km southwards. The far northern populations could be the result of recent human-mediated transport (a species introduction), or were simply not detected previously. The increased distribution around the previous northerly limit is likely a natural range expansion. The distribution of C. filiformis in NSW and globally seems confined to a temperature range of ~16–23°C. We found no relationship between abundance of C. filiformis and human population or oceanic chlorophyll-a (a surrogate for nutrient availability). We demonstrate that C. filiformis is predominately subtidal, being found along sections of coastline where there is a mixture of rocky reefs and beaches. It is argued that sand movement may have facilitated increases in abundance of C. filiformis.

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Summary There is now considerable evidence that, as the climate continues to warm, bushfires are becoming more common and severe, particularly in regions such as south‐eastern Australia. The extraordinary Australian bushfires over the summer of 2019/2020 resulted in the burning of habitats such as highland peat swamps and intertidal estuarine wetlands over unprecedented spatial scales. Across New South Wales, these bushfires affected 183 ha of saltmarshes and 23 ha of mangroves in 19 estuaries. The percentage of fire‐affected saltmarsh ranged from 51% to 81% in the worst impacted estuaries, although typically ≤15% of mapped saltmarsh was damaged. Just over 50% of mangroves were burnt in Wonboyn Lake (although this constituted <0.2 ha), whereas in all other estuaries, ≤5% of mangroves were burnt. At the state‐wide scale, the likelihood of saltmarshes being affected by fire was unrelated to adjacent terrestrial vegetation; however, mangroves adjacent to burnt wet sclerophyll forest were more likely to burn than not. Burnt mangroves were almost exclusively associated with extreme or high severity fires in adjacent terrestrial vegetation, yet saltmarshes were also impacted in some cases by moderate or low‐intensity fires. Many species of saltmarsh plants had re‐sprouted or germinated after 6–24 months, but the extent of any recovery or changes in species composition were not quantified. The majority of fire‐affected mangrove trees appeared to be dead 24 months after the fires, despite observations of epicormic growth on some trees after six months. Bushfire impacts to estuarine wetlands are likely to become more frequent and results from our work can help target hazard reduction burning that might be considered for minimising damage to mangroves. More work is required to better understand potential longer term impacts and the capacity for natural recovery of estuarine wetlands from bushfires.

1. Although it is well established that human activities are linked to the loss of seagrasses worldwide, the influence of anthropogenic disturbances on the habitat fragmentation of seagrass meadows is less understood. This information is essential to identify how humans are modifying seascapes and what disturbances pose the greatest risk to seagrasses, which is pertinent given the rapid urbanization occurring in coastal areas. This study examined how the habitat fragmentation of an endangered seagrassPosidonia australis varied in relation to several anthropogenic disturbances (i.e. human population, marine infrastructure, terrestrial run-off and catchment land-usage) within 10 estuaries across 620 km of coastline in New South Wales, Australia.3. When comparing between estuaries, the fragmentation of P. australis meadows was significantly greater in estuaries adjacent to highly populated metropolitan centresgenerally in the Greater Sydney region. At sites within estuaries, the density of boat moorings was the most important predictor of habitat fragmentation, but there was also evidence of higher fragmentation with increased numbers of jetties and oyster aquaculture leases.4. These results suggest that the fragmentation of seagrass meadows will become more pervasive as the human population continues to grow and estuarine development increases. Strategies to mitigate anthropogenic disturbances on seagrass meadow fragmentation could include prohibiting the construction of boat moorings and other artificial structures in areas where seagrasses are present or promoting environmentally friendly designs for marine infrastructure. This knowledge will support ongoing management actions attempting to balance coastal development and the conservation of seagrasses.