The suitability of Ulva fasciata, Ulva compressa, and Hypnea musciformis for production in an outdoor spray cultivation system, with respect to biomass yield and protein content
. JOURNAL OF APPLIED PHYCOLOGY 2020
Land-based seaweed ponds can produce 500-700 t of fresh weight (FW) ha(-1) year(-1), but their profitability can be cut by the cost of pond construction, including ground leveling, infrastructure cost, and water agitation. A potentially cost-effective, land-based seaweed culture approach where seaweed grow on substrates by spray culture has been examined. We measured the yield and biomass quality of three intertidal cultivable seaweeds, Ulva fasciata, Ulva compressa, and Hypnea musciformis, in spray (known elsewhere also as film or drip culture) and pond culture approaches, varying surface inclination and nutrient loading. These technical details are necessary for the evaluation of the approach and for upscaling. The best yield (up to 84 g FW m(-2) day(-1), 44-84% of yield in ponds) and quality (protein content and additional parameters) of spray-grown U. fasciata was obtained on 6 degrees-inclined trays with highly fertilized water. The highest protein content (24.5%), but with reduced yield, was obtained on 80 degrees-inclined trays. H. musciformis and U. compressa, apparently thanks to their stringy morphologies, yielded in spray culture up to 286 g FW m(-2) day(-1) and 172 g FW m(-2) day(-1), respectively. The overall quality and resilience of spray-grown algae profited from nutrient enrichment, and the best yields were achieved with enrichment of 10 g N and 1 g P m(-2) day(-1) in H. musciformis and 15 g N and 1.5 g P m(-2) day(-1) in both Ulva species. Biomass growth occurred in layers, which visibly differed in color and consistency. A thin bleached top thalli layer protected the biomass below from dehydration and bleaching and allowed there a high photosynthetic rate. A spray culture of Ulva sp. on seawater-sprayed cement tiles, with minimal maintenance, yielded up to 50 g FW m(-2) of tile day(-1). Economically, spray culture appears to be particularly suitable to the stringy algae.