Range and habitat associations of the native macroalga Caulerpa filiformis in New South Wales, Australia

Abstract

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.

Invasion-mediated effects on marine trophic interactions in a changing climate: positive feedbacks favour kelp persistence

“…In particular, ocean warming is predicted to increase the metabolism of herbivores [8,34,37], intensifying the pressure on key native macrophytes in temperate rocky reef systems, as tropical herbivores expand into temperate latitudes [2,36]. Concurrently, native tropical algae are expanding their distribution into temperate habitats prompting novel shifts in competitive and trophic interactions [38][39][40]. While we have an emerging understanding of climate-mediated impacts of range expanding consumers on native algae [2,36], the impacts and consequences of range expanding algae on competitive and trophic interactions are poorly known.…”

“…Caulerpa filiformis is a green alga found in South Africa, Mozambique, Peru and Australia [38][39][40][41]. On the east coast of Australia, C. filiformis has become locally abundant on temperate shallow rocky reefs well outside its historic distribution [40][41][42]. These range expansions have negative effects on co-occurring macrophytes [43] representing a similar invasive behaviour as Caulerpa taxifolia and Caulerpa racemosa in southeastern Australia, the Mediterranean and United States [44,45].…”

Forgotten underwater forests: The key role of fucoids on Australian temperate reefs

“…Indeed, both natural and experimental Phyllospora canopy removals in Tasmania result in rapid establishment of the invasive kelp, Undaria pinnitifida which benefits from available space and increased light following canopy loss (Valentine & Johnson, ). Similarly, it is hypothesized that loss of Phyllospora in the Sydney region (Coleman, Kelaher, et al., ) may have facilitated a local proliferation of the range expanding, Caulerpa filiformis which exclusively occupies Phyllospora's former habitat (Glasby, Gibson, West, Davies, & Voerman, ). Interestingly, expanding beds of C. filiformis can then have cascading effects on nearby Sargassum beds, negatively influencing photosynthetic condition (Zhang, Glasby, Ralph, & Gribben, ) and decreasing the abundance of epifauna (Lanham, Gribben, & Poore, ).…”

Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world

“…However, the translocation of species for aquaculture or the aquarium trade is also an important vector (Naylor et al 2001). A more recent phenomenon is the rapid expansion of many native species within (Zhang et al 2014;Glasby et al 2015) and outside their traditional range (Booth et al 2007). Far less is known about the establishment processes of these species, although propagule pressure (Lockwood et al 2005), changes in resource availability (e.g.…”