Of particular concern is the predicted contractions of species in the genus Cystophora, which is the second largest genus of fucoids globally (23 species, after Sargassum Guiry and Guiry 2022) and is endemic to Australasia.Ĭystophora spp. 2016), with ocean warming threatening severe range contractions in the coming decades (Martínez et al. 2009 Phillips and Blackshaw 2011 Smale and Wernberg 2013 Wernberg et al. A range of anthropogenic pressures has precipitated declines and local extirpations of several of these species (Coleman et al. Temperate Australia features one of the richest marine floras in the world, including an unparallel and highly endemic diversity of forest-forming algae (> 60 species). 2020), as well as nearshore food webs and coastal carbon cycling (Gouvêa et al. Importantly, fucoid forests play important roles in supporting temperate biodiversity (Taylor and Cole 1994 Fraser et al. 2022), but remain comparatively understudied (Coleman and Wernberg 2017). Forests formed by fucoid algae (order Fucales) are more globally widespread and diverse than kelp forests (Fragkopoulou et al. Yet, studies on subtidal canopy-forming algae have mostly focused on charismatic and well-studied species (mostly kelps), with little being known about other canopy-forming groups (Shepherd and Edgar 2013). 2005), with non-urbanized areas typically avoiding most declines (Benedetti-Cecchi et al. Losses and local extirpations have been particularly widespread in areas with intense human pressure such as heavily urbanized coasts (Kautsky et al. 2021), with negative consequences for ecosystem functioning and their associated fauna and flora. Declines and local extirpations of these seaweeds are however becoming increasingly prevalent as anthropogenic impacts increase on the marine environment (Thibaut et al. Subtidal canopy-forming kelps and fucoids form impressive underwater forests across temperate and polar latitudes. Increasing human impacts and further warming in the region threaten several species with further extirpation, some of which are endemic to the area and play unique ecological roles. decline are unknown, but likely involve gradual warming, marine heatwaves, and rapid urbanization. These losses are among the largest reported for any forest-forming species in the Australian continent. Three species experienced apparent functional contractions across > 250 km of coastline, with some losing approximately 8% of their global distribution. Despite the sampling effort quadrupling in contemporary times, most historically common species were found to be absent or exceedingly rare across their rear (warm) range edge, suggesting their functional extinction.
To do so, I use a combination of field surveys, records from the literature, anecdotal evidence, and herbaria collections spanning a period of > 150 years. Here, I examine the biogeography of the second-largest genus of fucoids globally ( Cystophora), which is endemic to Australasia. In contrast, comparatively little is known about marine forests formed by fucoid macroalgae, despite them being more diverse and globally widespread. Declines of canopy-forming macroalgae in response to a variety of anthropogenic stressors are increasingly prevalent in temperate latitudes, with most research efforts focusing on kelp forests.
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