| Macro algae such as Phylum Phaeophyta and Phylum Chlorophyta are important primary productivity source of off-shore ecosystem.In some areas,kelp bed are widely covered all over the world’s rocky reef coastline.Kelp bed provides good growth place and reproduction field for many small fish and economic fish juveniles,also gathered large quantities of macrobenthos like sea urchins and snails.Nitrogen,Phosphorus and other nutrients are fixed through macro algae,otherwise,seawater eutrophication are generated certain mitigation effect,inhibit the role of red tide,and improve the coastal water quality to restore economic fish habitat.Produce high ecological value and economic value.The primary consumers,represented by large benthic animals,are the key link of the energy flow of the food web of the large algae field,which is the important biological community connecting the producers and consumers,in the kelp bed food web.Macro Benthic fauna play a "middleman" role in the off-shore ecosystem food web.On the one hand,some benthic animals swallow the soil,absorb the organic matter in the sediment as a nutrient,stir seawater evenly,promote the decomposition of organic matter,reduce the water content of organic matter,accelerate the flow of self-purification process.To improve the water nutritional quality.On the other hand,macro benthic animals as consumers directly feeding large kelp,digestion and excretion to accelerate kelp decomposition debris.Contributed a lot of organic debris,as an important source of kelp primary productivity to support high species richness in kelp bed ecosystem.Otherwise,organic debris provided an important basis for the enhancement of species richness and species diversity in the whole sea area.A large number of kelp debris drift into the seabed sediments,which enrich the seabed sediment species.We selected key species of benthic food web in seaweed was used as the entry point,and the natural decomposition process of kelp was analyzed by carbon and nitrogen stable isotope techniques.The key link of the energy flow of benthic food web was analyzed,in order to provide data support for the stable isotope research of kelp bed and its biological resources for seaweed field.The results are as follows:1.Changes in overall δ13C,δ15N signatures and C content,N content,C/N ratios of five dominating kelp(U.pertusa,C.tenuissima,G.livida,S.vachellianum and H.fusifarme)litters in litter bags during degradation were examined.Kelp litters completely rotted over 42 days in the field near GouQi Island,both organic C content,N content and C/N ratios depleted after decomposition,as for δ13C and δ15N,there were no significant variation.We divided the whole kelp degradation into two periods which are leaching degradation period(0~11days)and microbiological degradation period(11~42days).Furthermore,trophic level changes by 0.4 in four benthonic herbivores as a result of degradation of macroalgae.It’s a significant deviation in macroalgae based kelp bed ecosystem food web establishment.2.Nutrient enrichment(trophic fraction)is relying on isotope technology to calculate the biological trophic level essential data.Macro benthos Torbo cornutus was selected for the long-term single feeding experiment.The results showed that the enrichment of carbon and nitrogen in foot abdominal muscle was 2.5 ‰ and 1.0 ‰,respectively.The enrichment of carbon and nitrogen in the stomach was 4.1 ‰ and 0.8 ‰,respectively.And the changes of carbon and nitrogen stable isotopes were discussed in different feeding time.3.In order to clarify the utilization strategy of macrobenthos in the kelp bed,the orthogonal feeding experiment of double bait was designed to analyze the feeding preference of four large seaweeds on the potential food.C.tenuissima > H.fusifarme > S.vachellianum> U.pertusa.The relationship between morphological features and feeding organs was analyzed by field-Weight> shell high> shell height> shell width,and comprehensive analysis of the feeding habits of the Torbo cornutus. |
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