Study On The Influence Of Monochromatic LED Light Source On Physiological And Biochemical Characteristic Of Seaweed

Seaweed provides a variety of ecosystem services and functions which support the sustainable development for human beings. However,localized human activities and global change are currently putting high pressure on the near-shore ecosystems, and the intensification, high-density and high-output of modern mariculture and excess fertilizer application retain large amounts of nutrients and contaminants in seaweed cultivation area, increasing the turbidity of the seawater. Therefore, there is now a pressing need for innovations to facilitate seaweed cultivation through enhancing light supply. Here this study respectively investigated the effects of five artificial light sources (white, red, green and blue LEDs and fluorescent light) on physiological and biochemical of seaweed (Sargassum horneri, Ulva pertusa and Sargassum fusiforme)through three sections, last but not least, we calculated the cost and benefit of applying the LED lighting in S. fusiforme cultivation. Our study will provide theoretical basis in selecting suitable light source or supplementary lighting for seaweed cultivation indoor/outdoor. The main conclusions are as follows:1. Results showed that for all LED light sources, maximum biomass accumulation of S. horneri were achieved under the photoperiod of 24L:0D. The surface absorption spectrum of S. horneri and the emission spectrum of four kinds of LED light sources were also analyzed. The surface absorption spectrum of S. horneri showed a wide peak in blue emission region and a sharp peak in red emission region, respectively. Therefore,blue-LED light could satisfy the growth of S. horneri and would be ideal supplementary light for S. horneri cultivation.2. The growth, photosynthesis pigments and soluble protein (SP) concentration of U. pertusa were significantly affected by light sources. The SGR of U. pertusa under white and blue LED were higher than those exposed to red, green LED and traditional fluorescent light. The maximum SGR, which under white LED,was 5.25 % d-1 while the SGR of U. pertusa under traditional fluorescent was only 3.6 %d-1. The Chi a concentration of U. pertusa under white LED and traditional fluorescent light were significantly lower than those under red and blue LED, the significance of Chi a concentration under green LED was only different with red LED. The SP concentration of U. pertusa under red,green and blue LED were significantly higher than those under white LED and traditional light, and there is no significant difference among red, green and blue LED while the SP concentration of U. pertusa under traditional was lowest.3. The growth, photosynthesis pigments and soluble protein (SP) concentration of S. fusiforme were also significantly affected by light sources. The SGR of S. fusiforme under white LED was significantly higher than those under red, green, blue LED and traditional fluorescent light. The maximum SGR, which under white LED, was 3.24 %while the SGR ofS.fusiforme under red LED was only 1.37 % d-1. The Ch1 a concentration of S. fusiforme under traditional fluorescent light was lowest, only 0.41 mg g-1 FW, a significant difference. and the Ch1 a concentration under green and blue LED were significantly higher than those under white LED. The Car concentration of S. fusiforme under traditional fluorescent light was 0.16 mg g’1 FW, which was also lowest. The SP concentration of S. fusiforme under traditional fluorescent light,which was only 4.1 mg g-1 FW, was significantly lower than white, red, green and blue LED.4. The total cost of applying the LED light source in 100 m2 aquaculture area of S.fusiforme was 1000.8 CNY, while the total benefits valued equal to 6293.6 CNY.Therefore, the final net income was ～5293 CNY, almost gained 300% value than traditional culture.In conclude, the sensitivity of seaweed showed diversity to light spectrum. The common as well as differences of physiological and biochemical characteristic of brown algae S. horneri, green algae U. pertusa and brown algae S. fusiforme manifested under LED light. In addition, this study indicated traditional fluorescent would be replaced by LED light in seaweed cultivation or aquaculture.