The feasibility of scalable coastal and offshore kelp mariculture in Alaska

Stekoll M ¹ , Lindell S ² , Bailey D ² , Yarish C ^5,10 , Goudey C ⁴ , Manganelli D ⁴ , Roberson L ³ , Decker J ⁶ , Dewhurst T ⁷ , Barbery K ¹⁰ , Li Y ⁵ , Marty Rivera M ⁵ , Perry B ¹¹ , Pryor A ⁸ , Mangini N ⁹ , Kite-Powell H ² , Peeples T ¹

¹ University of Alaska Fairbanks, Juneau AK, USA ² Woods Hole Oceanographic Institution, Woods Hole MA, USA ³ Marine Biological Laboratory, Woods Hole MA, USA ⁴ CA Goudey & Associates, Newburyport MA, USA ⁵ University of Connecticut, Stamford CT, USA ⁶ Alaska Fisheries Development Foundation, Wrangell AK, USA ⁷ Kelson Marine, Scarborough ME, USA ⁸ Kodiak Kelp Company, Kodiak AK, USA ⁹ Kodiak Island Sustainable Seaweed, Kodiak AK, USA ¹⁰ GreenWave, New Haven CT, USA ¹¹ Blue Evolution, San Francisco CA, USA.

The mariculture of seaweeds is becoming increasingly popular in Alaska.  With funds from the ARPA-E MARINER program, we tested different seaweed farm designs, seeding methods and harvest approaches for a scalable solution for the mariculture of Saccharina latissima (sugar kelp). Farm designs were based on catenary structures with or without the use of spreader bars with variable spacing of growlines.  Initial results show that line spacing can be as short as 1 meter with no adverse effects on yield.  There was no statistical difference in the growth of Saccharina whether in the middle or the outside of the array. Sagging caused by the weight of the mature fronds resulted in slower growth at depth. We have experimented with several “direct seeding” methods – spraying or painting both gametophytes and embryonic sporophytes on several different substrates, including the growlines. Some success was demonstrated with the outplanting of directly seeded growlines.  Our cooperating farmers tested various approaches for harvesting mature kelps.  One innovation that has worked well is the use of large bags for holding the freshly harvested fronds. Although the weight of the fronds on the growlines causes the lines to sink, the bags packed with the harvested fronds float, allowing for easy loading onto the transfer vessel.  Another advance in harvesting is a specially built harvest vessel, the Kelp Buddy, which was in operation for our last two seasons. We also employed a large seiner that was modified for harvesting the growlines.