Preliminary assessment on the effects of the commercial seaweed extract, AMPEP, on growth and thermal tolerance of the kelp Saccharina spp. from the Northwest Atlantic

Acadian Seaplants, Ltd., marine plant extract powder (AMPEP) is a commercially available extract derived from the brown seaweed, Ascophyllum nodosum. This extract is widely applied to increase the performance of land crops and has been reported to enhance growth of some seaweed crops. To assess the effects of AMPEP on the growth and thermal tolerance of Saccharina latissima and S. angustissima cultivars, we performed two experiments. First, juvenile sporophytes were dipped (i.e., 30 or 60 min) in AMPEP solutions of different concentrations (0.001, 0.005, 0.05, 1, and 5 g L-1). Sporophytes were then cultivated in half strength Provasoli's enriched seawater (PES) and allowed to grow at different temperatures (12, 16, 19, 23, and 25 +/- 1 degrees C) for 20 days using a temperature gradient table. Photoperiod was maintained at 12:12 L:D with photosynthetically active radiation (PAR) of 90 +/- 10 mu mol photons m(-2) s(-1). Results show a differential response between the two species tested. Sporophytes of both species cultured at 23 and 25 degrees C died during the first 7 days post dipping in AMPEP. After the 20-day period, the surviving sporophytes were transferred to an incubator set at 18 +/- 1 degrees C (i.e., LT50 after 20 days). These sporophytes remained for 14 additional days to assess for any delayed effect on thermal tolerance, with treated sporophytes showing a higher percentage of survival and growth than control sporophytes never exposed to AMPEP. Furthermore, after the 14-day incubation at 18 degrees C, treated sporophytes of both species showed blades more than three times thicker than control sporophytes. These preliminary results indicate that AMPEP may enhance the growth capacity of S. latissima and S. angustissima when exposed to suboptimal temperatures, allowing them to overcome heat stress more effectively while maintaining growth.