Experimental assessment of growing substrates for the early life stages of five large brown seaweeds

Abstract

Seaweed cultivation, especially for large brown algae (LBA; e.g. Laminariales, Fucales) is in development in many regions worldwide. Identifying appropriate growing substrates is a key step for establishing successful seaweed cultivation. We investigated the effects of four substrates with aquaculture and restoration potential on the density and length of recruits of five LBA in a series of 42‐day‐long experiments. The substrates assessed were green‐lipped mussel shells ( Perna canaliculus ), concrete gravel, fibreglass, and polyester twine. Reproductive material used to produce spores or gametes for experiments was sourced from the wild and collected in three seasons: early winter (June), late winter (August) and spring (October) in 2023. The LBA recruited and grew on all substrates. Ecklonia radiata had the greatest density and length on mussels and fibreglass. Macrocystis pyrifera had the lowest density and length on fibreglass. Landsburgia quercifolia had the greatest density and length on concrete and mussels. Cystophora retroflexa were most dense on fibreglass and twine but were longest on concrete and mussels. Cystophora scalaris were most dense on twine but grew the longest on mussels. Our study demonstrated that optimal growing substrates for LBA are species‐specific and identified novel, recycled materials for growing LBA for aquaculture or restoration purposes.

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