Study Of Shallow Cultivation And The Biological Characteristics Of Gracilaria Lichenoides

Seaweed can absorb the N and P elements in the water effectively, restore the ocean ecosystem, and do it has an ecological prevention function for red tide. In this paper, we cultured the Gracilaria lichenoides in the shallow sea, and measured N, P and agar content in its tissue, as well the photosynthetic capacity. Then we studied the effect of temperature on the water quality purification of Gracilaria lichenoides and the competition on nutrients between phaeocystis algae and cultured in the co-culture system. The results are as follows:1. Study of Gracilaria lichenoides’shallow sea culture and photosynthesisWe planted Gracilaria lichenoides in May, July, August and October of 2014, and found that the growth rate increased by monthly, especially in autumn. The highest growth rate reached 6.4%/day, which is 2.3 times as that in spring. Forrope culture pattern, the maximum growth rate reached 6.59%/day, which is 5.4 times as captive culture. The photosynthetic oxygen production rate reached a maximum in July, September the second, followed by May to a minimum. Suspension depths directly affect the photosynthesis efficiency of Gracilaria lichenoides. Additionally, N and P nutrients can increase the photosynthesis rate of Gracilaria lichenoides.2. Measure of N and P content in Gracilaria lichenoides tissue and extraction of agarThe highest content of N and P in Gracilaria lichenoides is in September (3.226%, 2.656%), and lowest is in May (1.099%,0.708%). The content of agar in July reached the highest,20.43%, and lowest in September,16.00%. Among the four kinds of seaweeds, asparagus got the highest nitrogen content, and Gracilaria blodgettii the lowest.But the the phosphorus content of Gracilaria blodgettii was 1.010%, and Gracilaria bursa-pastoris phosphorus was only 0.796%.3. Influence of temperature on Gracilaria lichenoides’s water purificationGracilaria lichenoides had a rapid absorption process of three forms of nitrogen in aquaculture wastewater within 72hours, especially NH4-N. Gracilaria lichenoides grew very fast in aquaculture wastewater. When we proceeded the 5th day, all the Gracilaria lichenoides achieved the maximum net daily growth. Under the condition of three different temperatures, Gracilaria lichenoides had the fastest absorption of four different forms of nitrogen and the net growth was higher than the other two groups when it is under 25℃.4. The nutrient competition between Phaeocystis globosa and Gracilaria lichenoides in the co-culture systemIn co-culture system, lower biomass (0.5g/L, lg/L) would promote the growth of Phaeocystis globosa, while higher biomass (2g/l,4g/L) would constrain the growth of Phaeocystis globosa, especially what it is 4g/L. Compared with Phaeocystis globosa, Gracilaria lichenoides can PO34-P、NO3-N faster.