‘Crayweed’ (Phyllospora comosa) forms dense underwater canopies on shallow reefs along Australia’s East coast from Port Macquarie to Tasmania, forming rich habitat that supports a plethora of marine ecosystems. After anthropogenic pollution contributed to massive declines in metropolitan Sydney crayweed populations in the 1980s, our own Operation Crayweed has been working hard to restore the vibrant seaweed forests in our back yard.

However, with ocean warming and marine heatwaves increasing, seaweed populations are increasingly threatened and crayweed is in hot water. ⁠While restoration has helped to recover lost populations, restored crayweed is now at risk of being wiped out by heat stress during marine heat waves. As we anticipate warmer and harsher future ocean conditions, the need for increasing the resilience of our crayweed is front of mind, and improving their capacity to resist stressors is key for maintaining crayweed forests. ⁠

Catalina collecting crayweed samples.
Catalina running experiments in the SIMS research aquarium.

Catalina Musrri, PhD candidate at the University of Sydney, aims to find the populations of crayweed (genotypes) that are best adapted to temperature by comparing the responses of crayweed genotypes from northern edge and central populations. ⁠By identifying the genotypes that are less susceptible to heat stress and more likely to survive marine heat waves, there is the potential to prioritise transplantation of favoured genotypes in restoration campaigns. Hence, increasing the abundance of resilient crayweed and hopefully giving our crayweed forests the best chance of survival in future ocean conditions.

So far, she has run experiments in the SIMS research aquarium and tested the responses of juvenile crayweed (~6 months) and germlings (a week old) from Port Macquarie, Forster, Palm Beach and Cronulla to marine heatwaves to understand if different genotypes have varying tolerance to increasing temperature.

We look forward to seeing what Cata’s research uncovers and adapting our own restoration initiatives to sustain NSW’s crayweed forests and allow supported ecosystems to thrive.

Catalina sexing crayweed samples.