Effects Of The Oligoguluronate On Physiological Responses Of Saccharina Japonica

China is by far the largest producer, in terms of the cultivation scale and production volume of S. japonica. It accounted for 60% of the total production of the world. The artificially intensively cultivated S. japonica might favor disease outbreaks, which regularly lead to the destructive loss of 25-30% of the volume at a regional scale. Like terrestrial plants, breeding and disease prevention is the focus of research in aquaculture. Therefore, for the disease outbreak of the S. japonica, screening effective, safe and non-polluting immune elicitor for kelp which can promote sporeling growth and improve immune disease resistance of S. japonica that is applied to the sporeling production of kelp, not only can provide health and high quality sporelings for seaweed farming, but also can help preventing the disease outbreak of kelp.Alginate oligosaccharide has been confirmed as a signal molecule with multiple functions that can regulate the growth, development, reproduction and activate defense reactions of plant. Research of the alginate oligosaccharides on the immune elicitor has attracted wide attention in the world. According to our previous study, oligoguluronate, the alginate degradating products can induce sporophytes of Laminaria digitata to produce different defense responses. So whether oligoguluronate can be one kind immune elicitor of S. japonica that can promote seedling and cultivated kelp growth and improve disease resistance? Therefore, in this study we investigatted the effects of oligogulurnate prepared by partial acid hydrolysis on the growth of sporelings and adults, decay of blades, the biomass of epibionts and endobionts of S.japonica. Results are as follows:1. Detecting the production of H2O2 in the medium of S. japonic induced by the different concentrations of oligogulurnate using luminol fluorescence detection method. The necessary concentration for oligogulurnate that can be an immunity elicitor is greater than or equal 10 μmol.2. Treating the sporelings with 50 μM oligogulurnate weekly, biweekly and fourweekly during the nursering period of S.japonica in 2012 and 2013. The growth and the density of the sporelings that were treated by 50 μM oligogulurnate weekly are higher than the control and other treated groups.3. Treating the adults with 50 μM oligogulurnate biweekly and fourweekly during the culture period of S.japonica. The growth of the adults treated by fourweekly is up to 2.5 cm per week which was higher than the control and biweekly treated groups. The cover rate of endobionts in the adults that treated by biweekly was 12% which wass significantly less than the controls and fourweekly treated groups. But the covering rate of epibionts on the adults was 19% which was significantly higher than the control and fourweekly treated groups. The associated bacteria on the surface of S japonica treated by 50 μM oligogulurnate wa just 3.0×107 inds/cm2, which was significantly less than the control (1.3×108 inds/cm2). But the decay rate of blades was higher than the control and fourweekly treated groups.Our results show that:the effective concentration of oligogulurnate can promote the growth of sporelings and cultivated adults of S japonica. But there are both benefits and disadvantages for the effects of physiological responses on the cultivated adults of S japonica. So screening effective, safe, non-polluting immunity elicitosr for kelp needs further study.