Restoring Sydney’s
Underwater Forests

Crayweed’s scientific name is Phyllospora comosa, sometimes abbreviated as P. comosa.

Crayweed is found up and down Australia’s east coast, from Port Macquarie in the north to Tasmania in the south. It still exists here today, except for in Sydney where it disappeared completely from the coastline adjacent to the metropolitan area during the late 1970s and early 1980s (Coleman et al. 2008).

Crayweed’s disappearance coincided with high volumes of poorly treated sewage waste that was (until the late 1980s and early 1990s) released directly onto Sydney’s beaches and bays (Coleman et al. 2008).

Water quality has improved dramatically since that time, due largely to the construction of deep water sewage outfalls (Scanes & Phillip 1995; Sydney Water Report 2007), but crayweed has failed to recover in Sydney (Coleman et al. 2008).

Crayweed supports a unique component of coastal biodiversity, which is not supported by any other extant seaweed species. Therefore, once it’s lost from an ecosystem, many other organisms and ecosystem services are also lost. It also supports much higher abundances of abalone (7-10 times) than other seaweed species in the region (e.g. Ecklonia radiata) or barren habitat (Marzinelli et al. 2014).

Crayweed contributes uniquely to detrital food webs (Bishop et al. 2010), which support recreationally and commercially important fish species, including bream and mulloway. Crayweed has a specific diversity of microbes on its surface, compared to other seaweed species (Campbell et al. 2015).

We say around 2014, however, we first trialed crayweed restoration between February 2011 – May 2011 and repeat experiment set-up in August 2011). We found that survival rates of transplanted crayweed were similar to those in undisturbed, remnant populations (~70%; Campbell et al. 2014) and Rates of reproduction and the resulting numbers of babies (“recruits”) were very high – around 100/0.1 m2 (ten times higher), 6 and 12 months after transplantation (Campbell et al. 2014)

We transplant healthy and reproductive individuals into areas in which we deem to be receptive sites. The material itself won’t survive, our hope is that instead the crayweed reproduces at the new site creating baby crayweed or “craybies” that will attach to the rock and grow into reproductive adults themselves one day.

We do this using multiple methods from drilling in mats to receive full individuals, to attaching bags to place reproductive material into. We are always trialing new methods that allow us to give us the greatest chance of success in a given area.