Operation Crayweed — Restoring Sydney's Lost Underwater Kelp Forests

Crayweed (Phyllospora comosa), a golden seaweed that once formed dense underwater forests along Sydney's coastline, vanished from the city's reefs in the 1980s — likely due to poor water quality — and did not recover naturally even after water quality improved.

Since 2012, Operation Crayweed, led by UNSW Sydney's Centre for Marine Science and Innovation, has fixed fertile adult plants from healthy populations onto barren reefs with biodegradable mats; transplant stress triggers spawning and offspring attach permanently to the reef. Transplanting has taken place at nine locations spanning roughly 70 km of coastline.

Peer-reviewed monitoring found transplanted crayweed achieves survival and reproduction rates comparable to natural populations, restoring habitat that supports abalone, rock lobsters and other reef species.

The programme is funded by a durable, multi-funder model — NSW government trusts, the Australian Research Council, private foundations and UNSW's own research centre — now over a decade old.