CRAYWEED RESTORATION PROJECT
Seaweeds (Macroalgae) are the 'trees' of temperate marine ecosystems, providing food and shelter for other organisms and coastal supporting biodiversity.
In many parts of the world (including here in Australia), seaweed forests are declining or disappearing altogether. Declines are typically linked to human impacts in these ecosystems, including climate change and pollution. Even if the processes that cause declines are managed, ecosystems may not recover naturally.
Our aim is to help reestablish important seaweed forests onto reefs where they were once dormant, whilst learning about the ecology and biology of these critical organisms.
Crayweed (Phyllospora comosa) was once abundant along the coastline of Sydney, Australia’s largest city. Crayweed formed dense forests in the shallow waters of many rocky bays around the city, but disappeared completely some time during the 1980s. This loss of approximately 70 km of dense, underwater forest went unnoticed and unreported in the scientific literature until 2008, when Coleman et al. published an article describing a conspicuous gap in the distribution of crayweed in south-eastern Australia, matching the extent of the Sydney metropolitan area.
Crayweed supports unique biodiversity, including commercially important species like lobster and abalone (Marzinelli et al. 2013). It also contributes to detritus in soft sediment habitats (Bishop et al. 2010), which underpins food webs of key fish species including mulloway and bream.
The local disappearance of crayweed from the most urbanised stretch of coastline on the Australian continent was linked to the high volumes of poorly treated sewage that used to flow onto Sydney’s shores before the construction of deep ocean outfalls in the 1990s. These outfalls and improvements in wastewater treatment practises have vastly increased water quality around Sydney since the 1980s but despite this, crayweed has failed to recover.
In pilot experiments, we tested hypotheses about whether the marine environment in Sydney, where crayweed once thrived, has now improved to the extent that it can survive there again, by transplanting crayweed from extant populations to the north and south of Sydney, back onto Sydney reefs. The transplanted crayweed not only survived similarly well to those in natural populations, they reproduced more effectively (Campbell et al. 2014).
Our overall aim is to help re-establish self-sustaining populations of crayweed at places in Sydney from where it has disappeared, by transplanting fertile adults and are currently running experiments to find the optimal methodology to do just this. Additionally, by restoring seaweed populations, we aim to enhance coastal biodiversity, improving the ecological and commercial value of marine environments around Sydney.