Recovering kelp forests using newly constructed oyster reef restorations: adapting a kelp transplant method

Transplanting adult kelp is one of several key methods for kick‐starting the restoration of kelp forests. This study explores the efficacy and obstacles of adapting a kelp transplant method developed for Ecklonia radiata , a key habitat‐forming kelp on temperate coastlines across Australia. Specifically, we assessed whether a method for attaching kelp to concrete structures could be adapted to establish kelp forests on boulder reefs that were constructed to restore oyster reefs; an oyster restoration strategy that is increasingly used worldwide. Adult kelp were attached to reef boulders using recycled rubber straps and positioned on two oyster reef restorations with distinct environmental and structural conditions. Reef boulders were selected based on their size and shape such that they could be easily moved and secured on constructed reefs by an individual diver. After 10–15 months (depending on site), we assessed transplant survival, recruitment of juvenile kelp, and percentage cover of competitive turf algae. We found that transplant survival was highly variable (0–100%) and site‐dependent, with survival particularly low at sites with higher hydrodynamic energy. Kelp recruitment was site dependent, with high recruitment (up to 46 sporophytes/m 2 ) on reefs cohabited by oysters, and no recruitment in their absence. Turf cover varied from 5 to 100%, with a reduction in turf related to increased kelp recruitment. This transplant method shows genuine promise for rapidly establishing small kelp patches on boulder reefs, though environmental factors such as wave exposure must be carefully considered.