Exploratory evaluation of the effects of Kelpak® seaweed extract on cultivated kelp Saccharina spp. exposed to sublethal and lethal temperatures

Kelpak®is a seaweed extractfromthe phaeophyte,Eckloniamaxima,used to enhance growthand production of terrestrial plants. It is also beneficial for some red and green seaweeds. Assuch, we assessed if Kelpak® could enhance growth and thermal tolerance of the brownseaweeds,Saccharina latissimaandS. angustissima. Juvenile sporophytes were dipped (30 or 60min) in Kelpak®solutions of different concentrations (0.001, 0.005, 0.05, 1 and 5ml L-1). Thesesporophytes were then cultivated in half-strength PES at different temperatures (12, 16, 19, 23and 25°C±1) for 20 days. The surviving sporophytes were then moved to 18 ± 1°C and cultivatedfor 14 additional days. Results show that temperature was the main factor driving survival andgrowth. Both species exposed to the temperatures of 23and 25°Cdied during the first seven days.Furthermore, no significant differences were observed in growth of sporophytes at thetemperatures of 12 and 16°C. Results also show that treated sporophytes exposed to 18°C, thesublethal temperature, particularlyofS. angustissimashowed a higher survival and overall vigorthan non-treated sporophytes. These results indicate that Kelpak®may enhance thermal toleranceand growth ofS. latissimaandS. angustissimaexposed to sublethal temperatures.