World Aquaculture - December 2023

WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2023 17 that is competitive with terrestrial bioenergy feedstocks and fossil fuels remains a major obstacle in developing macroalgae as a biofuel feedstock (Navarrete et al. 2021). Ocean Era is located at The Natural Energy Laboratory of Hawai’i Authority (NELHA), a state-ofthe-art ocean science and technology park in Kailua-Kona, Hawai’i (Figure 1). The site has production tanks that range in size from 200L to 50,000L. NELHA provides tenants with ambient-temperature seawater from near the ocean’s surface (SSW), and cold (4-8° C) seawater drawn from a depth of up to 900m (DSW). The DSW is high in nutrients essential for seaweed to grow such as nitrate/nitrite (~560mg/L) and phosphate (~90mg/L). High rates of insolation year-round provide an advantage for increased productivity that is not seasonally limited. Irradiance on site is, on average, 2000 mmol/m2/s at the peak of the day, and the photoperiod is about 12:12 +/- 1hr year-round. The primary focus of the macroalgae research at Ocean Era is to advance healthy, responsible, and sustainable mariculture, particularly through the cultivation of tropical macroalgae species using minimal external inputs. The company is currently conducting land-based trials to test various parameters and model the performance of these species in an off-shore farm environment. To achieve this, the company carries out flume trials, subjecting the macroalgae to high water velocities to assess the impact of currents on their growth. Further details on these trials are discussed below. Currently, Ocean Era has focused on maximizing the production of several species of native Hawaiian macroalgae through testing various abiotic parameters including temperature, light intensity, stocking density, attachment strategies and nutrient additions with the pulsing of DSW or with finfish effluent. Several red (Rhodophyta) and green (Chlorophyta) macroalgal species including Halymenia hawaiiana, Gracilaria parvispora, Grateloupia filicina, Caulerpa lentillifera, and Ulva spp are currently in cultivation (Figure 2). Mariculture plays a vital role in sustaining humanity’s growing population, providing food, animal feed ingredients, and an array of chemical extracts (Hwang and Park 2020). Seaweed farming may prove to be an important tool in meeting the United Nations Sustainable Development Goals for environment, biodiversity, and climate targets (Duarte et al. 2022). Current annual global seaweed production is over 30 million tons and has grown 8 percent annually since 2014 (FAO 2020) with demand for seaweed projected to increase. There is also opportunity for seaweed to help decarbonize biomass production and alternatives to fossil fuel derived products. Macroalgae (limu in Hawaiian) has many traditional uses in Hawai’i, dating back to the archipelago’s early Polynesian settlers who gathered it from the wild (McDermid et al. 2019). Prior to Western contact, limu was a regular part of the diet, used as flavoring or spice in Hawaiian cooking, as well as having cultural significance for rituals, medicine and commerce (Abbott 1978, Reed 1907). Today, community groups in Hawai’i are working to preserve traditional limu uses, revitalize and maintain wild populations, and preserve cultural knowledge (McDermid et al. 2019). Coastal development, sewage-outfall, agricultural run-off, over-fishing, the spread of non-native species, and the decrease in groundwater that flows along the shoreline are severely altering the limu populations in the wild (Dailer et al. 2012, Dulai et al. 2021). There is a need to cultivate native species that can be used for food, to lessen the reliance on the already impacted wild stocks and to allow for scaleup of production to meet additional demands. Ocean Era Inc., a Hawai’i-based aquaculture company, started cultivating limu as part of the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) efforts to increase marine biomass production through the Macroalgae Inspiring Novel Energy Resources (MARINER) program. MARINER seeks to develop the technologies needed to grow and harvest large quantities of macroalgae offshore, for future biofuel production and to decrease dependence on fossil fuels. Achieving large-scale and year-round production of marine biomass at a price Tropical Seaweed Cultivation in Hawai’i Simona Augyte, M.J. MacMahon, Trevor Chambers, Jennica Lowell-Hawkins and Neil A. Sims FIGURE 1. Site location at NELHA showing macroalgae nursery, office, and flume tanks for testing growth performance under high velocity current regimes, with different SSW and DSW concentrations. (CONTINUED ON PAGE 18)