Primarily Evaluation On The Performance In Ecological COnservation And Effects Of Ecosystem Of Li Island Artificial Reefs

This article evaluates the performance in ecological conservation of artificial reef approached not only to the pre- and post- deployment investigation on ecological factors from 2006 to 2008, but also to the contrast of that between reef regions (near shore, NA; off shore, FA) and no-reef regions (near shore, NN; off shore, FN) in the four quarters of both 2009 and 2010. The dynamic of algae attaching to natural reef and reefs of different types as well as dynamic of nekton communities in artificial reefs and control regions are studied along with the relationship between dynamic of communities and environment factors. Moreover, the ecosystem effects of artificial reefs are assessed based upon the ecosystem health evaluation and valuation of ecosystem services. The main results indicate that:Results of the comprehensive surveys from 2006 to 2008 exhibit that the contents of pH and DO significantly increased after casting reefs in reef regions, where the contents of DO in 2007 and 2008 were 1.75 and 1.53 times more than that in 2006, respectively. Contents of COD and BOD5 in reef regions were above the normal levels in 2007, while they decreased in 2008. The content of NH4-N didn't change obviously during the survey periods. Nevertheless, in comparison with no-reef regions, the content of chlorophyll a, together with the kinds and biomass of both benthos and nekton somewhat increase in reef regions.The survey of the four quarters of 2009 and 2010 in reef regions and no-reef regions reveal that the indices of DO, COD and BOD5 in reef regions were higher than those in no-reef area,while where contents of NH4-N, PO4-P and SiO3-Si were just the reverse. In 2009, more content of chlorophyll a was possessed in reef regions than that in no-reef regions. Further more, the no-reef regions showed lower level on content of chlorophyll a compared with FA in February and NA in both August and October during 2009. On the contrary, contents of chlorophyll a in all regions (NA, FA, NN and FN) of the four quarters during 2010 showed no significant difference, except that the content of chlorophyll a in FN was lower than all the other three regions remarkably. And the reef regions also displayed a good effect of ecological radiation on no-reef region in 2010. Coscinodiscus and Rhizosolenia and Noctiluc were the dominate phytoplankton species in the survey. In 2009, the quantity of phytoplankton observed in reef regions was obviously more than that in no-reef regions. Also more quantity of phytoplankton was found in reef regions than in no-reef regions with the exception of no significant variation detected between NN and NA in both February and November. Calanus and Crassa acted as the dominate zooplankton species, and all reef regions have more biomass of zooplankton than that in no-reef regions. The kinds and biomass of benthos, nekton were on a higher level than that in no-reef regions, except for no considerable difference on the kinds of nekton found among all the regions in spring and autumn. Generally, the artificial reef exhibited the effect of ecological conservation to some degree.The algae community developed and has reached the step of maturity after 3 years of artificial reef deployment through investigation. The biomass, species numbers and the diversity index in summer and autumn were all higher than those in spring and winter. And the result of similarity analysis exhibited that: 1) there was high similarity in the summer and autumn communities, more than that in the spring and winter communities; 2) The communities of algae on the same habitat in the summer and autumn are much more similar with each other; 3) The communities of algae on rock reef are similar with that on natural reef. Study on the relationship of the environment factors and the alga communities revealed that, temperature, silicate and DO were the first important factors, while N,P nutrients were of secondary importance. The second and third important factors that influent the communities of algae on distinct habitats were different. On natural reef, the amount of N,P nutrients were second and third important factors. And the level of pH and DO were the second and third important factors on artificial reef. Rock reef was the best selection to build artificial alga-field in this area.According to the study of the dynamic of, results showed that fish played a leading role in nekton communities especially the rocky fish which were absolutely dominant species in them. The community structures of the nekton in spring and autumn showed high similarity with that in no-reef regions,but communities structure of nekton in summer and winter, more complex, are distinct from their control regions. For the communities, temperature was the first important factor among which affected the nekton communities,besides depth was a very important factors which affect the communities of different regions in same season.The Li Island artificial reef ecosystem become healthy from the pre-casting time to the post-casting time,with time going on the artificial reef ecosystem will be further improved. The Li Island artificial reef ecosystem services are valued at 54.78795 million Yuan per year from all 8 services of 3 types ,which is more than the average value of the global ocean ecosystem. The value of ocean ecosystem will increase through casting reefs, scientific management and cultivation of marine organisms.