Culture Technique Study On Sargassum Thunbergii In Pond

Sargassum thunbergii belongs to Phaeophyta, Cyclosporeae, Fucales, Sargassaceae, Sargassum, and is a common kind of wild macroalga along the coast of China. It is rich in brown algae polyphenols, polysaccharides active substances and has a wide range of potential application in medical, health care, chemical and other industries. S. thunbergii has the absorbability of arsenic, zinc, cadmium and is able to purify some harmful substances in seawater such as ammonia-nitrogen, nitrite-nitrogen and phosphates. Due to the long frond and less mucus, S. thunbergii is a good combination of species with proliferative fishing reef. This alga grows fast in spring and autumn.and is suitable to aquaculture in cofferdams or artificial reef pond alongwith sea cucumber, abalone, etc.In recent years, along with the rapid development of mariculture, the negative impact of offshore ecological environment has increased seriously. Domestic and foreign scholars generally believe that large-scale seaweeds aquaculture is one of effective measures to absorb and utilize nutrients, purify water and delay eutrophication in seawater. As large seaweed, S. thunbergii has high research application and economic value,'Culture technique study on S. thunbergii in pond'is sub-topics of'Beach culturing pollution control and clean-production technology research and development'. The research focuses on two parts, one is ecological observation of S. thunbergii culture technique in pond, and the other is to clean seawater ammonia-nitrogen, nitrite-nitrogen, phosphates and other harmful substances. This study mainly investigates ecology observation part of'Culture technique study on S. thunbergii in pond' and select three kinds of seed, including natural wild seedlings, laboratory and ponds culturing artificial seedlings, to perform growth comparative test. Designs of experiment conditions are as follow:different water-layer growth comparative test, different water flow growth comparative test, frond length and body wet weight comparative test, effects of temperature and illumination intensitys on the growth rate, at meantime, careful observion of S. thunbergii fertilized egg's development process, research temperature and light intensitys'effects on the young sporophyte growth and development, compare S. thunbergii growth with different algae adherence.The main results are summarized as follows:1. Under the same experimental conditions, the growth of natural and artificial seedlings is mesured, and the results showed that natural wild seedlings grows fastest, winter seedings grows secondly (The curtain seedings arrived in last October from Rongcheng to Jiaonan), artificial seedlings grows slowest. Meanwhile, S. thunbergii's acceleration growth phase is in April and May, from early June, the curtain seedings become shorten. Analyze the reasons, may be due to curtain back light is too dark that lead part of S. thunbergii grow recession.2. Different water-layer growth comparative test. Four different water depth conditions (0-20 cm,40-60 cm,80-100 cm and 150-200 cm) are set for growth of S. thunbergii. The water depth of 40-60 cm is most suitable for the growth of alga and the light intensity in around 4000 lx-6000 lx,0-20 cm is secondly, the worst is 150-200 cm. Growth become shorten is in last May, and this growth recession may be due to insufficient light and constant rising water temperature. The other water layers S. thunbergii appears grow slow after mid-May. With the water temperature increasing, S. thunbergii grows more lateral branches, so the overall length grow slow.3. S. thunbergii is studied under four different water flows,1 m/s,0.5 m/s,0.3 m/s and 0 m/s. The results showed that growth rate was faster in flowing water than standing water,1 m/s compared with 0.5 m/s, fast-growing 18% and fast-growing 37% at flow velocity of 1 m/s compared with 0.3 m/s, and that means growth rate depended on the water flow. Due to limited conditions, no research is carried out more than 1 m/s.4. Frond length and body wet weight comparative test is studied during the culture of S. thunbergii. The results showed that before mid-May, frond length grew faster and body wet weight grew slower, however after mid-May, frond length grew slower, body wet weight grew faster. The reasons maybe due to lateral branches growth of S. thunbergii after mid-May.5. During the period of late March to early June, as per the rising of water temperature, the results showed that S. thunbergii grew faster at the pond temperature of 12℃-18℃, however,18℃-24℃grew slower, upper 24℃degree, S. thunbergii start to decay. That means that the temperature of 12℃-18℃is the suitable for the growth of S. thunbergii, and upper 24℃, alga will stop growing and start decaying.6. Research of S. thunbergii's growth under different illumination intensity. Results showed that frond length and body wet weight grew better at illumination intensity 4000-6000 lx, but more than 10000 lx, below 3000 lx and lower than 1000 lx, frond length and body wet weight grew slower and no receptacle appeared in the whole growth process, S. thunbergii stopped growing from mid-May and turn up to hollowing and decaying.