Macroalgal aquaculture is a priority in the blue economy for its potential to enhance local economies, provide food security, and development nutrition and biotechnical products. Since 2016, the seaweed farming industry in the United States has expanded by a factor of 40, growing from 18.5 tons to 740 tons. Despite this growth in the US, farming protocols and methods are still in development, particularly when catering to diverse environments and target species. This project aims to establish a robust cultivation protocol for the winged kelp Alaria marginata by comparing multiline and single longline systems along a depth gradient in an embayment. Estuarine systems such as Humboldt Bay offer a more protected environment for kelp aquaculture in comparison to more exposed environments and may provide more stable nutrient levels due to coastal proximity. However, they can also experience more fluctuations in salinity and temperature. Insights from the first year and comparative analyses will inform the second year’s strategy, aiming to maximize biomass production and optimize cultivation protocol within the best growing season.
A. marginata sporophylls were collected from local populations and spawned in a controlled environment. Spores were settled on Matsuura Cremona twine spooled around 2-inch PVC to seed farm lines. Two farm systems were used: 1) a single-long-line system, where there is a single 107 m length of grow line attached to buoys, and 2) a multi-long-line system, where five 61 m grow lines were spaced 0.76 m apart using a 3.05 m aluminum spreader bar. The multi-long-line system allows the assessment of growth of more biomass in a smaller area while also allowing for a depth analysis. Biweekly measurements for blade length and width were taken randomly along the length of each grow-line. Water quality measurements were also taken.
In the first targeted growing season (July 2024 to September 2024), mortality occurred over time; By the sixth week, only two individuals remained on the entirety of a 107-meter grow line. Temperatures of 18 °C, a maximum of 0.1 nitrates ppm, and a maximum of 1.0 phosphates ppm likely limited growth and survival. Gametophyte banking will be utilized to outplant during times of the year when naturally occurring sporophylls are not present so that optimized growing season can be determined.