Formational Mechanism Of Detritus In Seaweed Bed And Ecological Conservation Function Application Of Island Reef Water

Reef island water area is one of the most important components of offshore ecosystems worldwide.Although it merely covers a small proportion of the whole sea area,it plays a significant role in fields such as supply of marine food and enhancement of living resources,healthiness of local marine ecosystem and social stability of fishing areas.Island reef has higher marine stock biomass and biodiversity than adjacent sea areas,often reveal the phenomenon that biomass and biodiversity decrease progressively along offshore distance-gradient(e.g.,ecological radiation effect).Aims to understanding the material basis and mechanisms of above phenomenon,we propose following hypothesis: the high marine stock biomass,biodiversity and ecological radiation effect of island reef are based on high primary productivity,trophic diversity of macroalgae and transportation patterns of macroalgae detritus.Under bottom-up and functional ecology framework,we choose macroalgae and its detritus as indicators of functional traits,using underwater macroalgae degradation observation experiment,stable isotope analysis and gut content analysis to investigate the food web(including grazing food chain and detritus food chain)in seaweed bed.Our study concluding three sections: 1.Ecological process of macroalgae degradation: using integration of stable isotope analysis and underwater macroalgae degradation observation experiment,we investigate the changes of stable isotope values during macroalgae degradation process and sediment stable isotope along off-shore gradient.2.Detritus food chain and primary-secondary production interaction study: we used integration of food preference observation experiment and stable isotope analysis to determine the respective macroinvertebrate dietary ecology type in seaweed bed by dietary observation and identify the real dietary source of potential source and quantify estimation the diet contribution to macroinvertebrate in seaweed bed all-year-round by SIMMs.Furthermore,we verify results of dietary observation and SIMMs dietary contribution evaluation by investigation of ?13C and ?15N stable isotope signature of trophic sources and consumers,furthermore,attempt to solve the uncertainty and discrepancies between the traditional stable isotope technique assumption and dietary ecology of consumer-diet interaction.Based on above analysis,we also investigate a new framework cooperate dietary observation data and stable isotope analysis data,named D-SIMM,to recalculate the trophic resource contribution of different potential trophic source in different discipline.3.we suggest using diet mixture model to solve the problem in diet fraction estimation of high trophic level species.The diet mixture model represents a beneficial new method to quantitatively estimate prey contributions to predator diets using stomach content data.It advances the statistical modeling of these data by providing a robust,likelihood-based method that can be applied to complex data.The model was applied to those species,especially the high trophic level species that could do stomach content analysis and available to get clarified data of stomach content.Also,in this study,we present a stepwise framework integrated dietary process-based stable isotope mixture model and Diet mixture model to estimate the seaweed bed habitat food web structure.Still we suggest a framework combining bottom-up theory and marine ranching construction.In summary,this research will provide basic theories of scientific management and marine ranching construction MPA(marine protected area)design.1)Ecological process of macroalgae degradation Integration of stable isotope analysis and underwater macroalgae degradation observation experiment showed: macroalgae's C content,N content and C/N ratios depleted during degradation process,as for ?13C and ?15N during degradation process,there were no significant variation.Furthermore,trophic level changes by 0.4 for benthos herbivores in seaweed bed.In accordance with three macroalgal life history stages: germinate and grow,mature and bloom,and decay and die.The sources and variations of the SOM were determined by carbon and nitrogen stable isotope analysis using the molar carbon-to-nitrogen(C/N)ratio and stable isotope composition(?13C and ?15N)as indicators.SOM was mainly derived from the mixed contribution of phytoplankton and macroalgae.The ?13C values of the SOM were significantly different at the various water depths in summer and the ?13C values of the SOM showed temporal variations,whereas spatial variations alone depth gradient were found in seaweed bed.According to the relations among the ?13C,?15N,and C/N,the and it was attributed to the contribution of phytoplankton in October and the following May.In summer,macroalgae,on average,contributed up to 53.71% of the SOM from the seaweed bed,as estimated by the carbon stable isotope mass-balance mixing model and the proportion of macroalgae detritus in the SOM was significantly affected by macroalgae coverage.2)Detritus food chain and primary-secondary production interaction study Although stable isotope analysis on food web,especially determine the trophic source and food web structure have been relatively studied in last decades.It has been recognized that models used to evaluate source-consumer contribution is based on a multivariate beta distribution,known as the Dirichlet distribution,neither conclude the pi = 0 and pi = 1 situation.Namely,in previous stable isotope models,scientist assumed every potential trophic source makes contribution to consumer.However,animals have various dietary preference and some trophic resource in habitat may have no contribution to consumers,but less is known above species-specific dietary process effects on stable isotope analysis,especially for trophic contribution estimation.In this section we developed methods to determining consumer's “real potential trophic source” and “discrimination factors” by using lab-based observations and reviews of lab-based discrimination experiments.Furthermore,we presented a process integrate lab-based dietary preference observation and stable isotope mix model(SIMM),named dietary process-based SIMM(D-SIMM)for trophic contribution estimation.The trophic source contribution of three representative macroinvertebrate species sea urchin: Anthocidaris crassispina,Gastropod: Turbo cornutus,mussel: Septifer virgatus were estimated and validated using SIMM and D-SIMM.For comparative purpose,standardized convex hull area(TA)of species-specific trophic sources and consumers,standard ellipses area(SEA)of potential trophic source group were calculated and compared between SIMM and D-SIMM.We found significant species-specific dietary preference between consumers,resulting systematic difference of TA,SEA and trophic source contribution estimation between SIMM and D-SIMM.As such,dietary process-based SIMM explained pi = 0 of certain trophic source situation,which was often causing uncertainty and ignored in previous SIMM.We also found species-specific discrimination factor should be noticed during trophic source estimation.For estimation of trophic source contribution to consumers,our finding implied that dietary preference of consumer should be fully considered before SIMM analysis.In conclusion,D-SIMM is a more ecological process and robust measure to validate trophic source estimation.Additionally,taking our result of high MAC coverage in seaweed bed and high detritus contribution of MAC to SOM into consideration,combining with estimations of source contribution,we suggest that MAC and its debris is the key trophic source for T.Cornutus,A.crassispina and S.virgatus in seaweed bed habitat.3)food web structure and ecosystem function of island reef seaweed habitat has higher marine stock biomass and biodiversity in every trophic level than adjacent sea areas,in view of functional redundancy,we can consider the relationship of functional redundancy to other concepts in the food web structure,and discuss problem and limitation in both analysis methods and effects of species redundancy on ecosystem function.Our results suggest seaweed bed is more stable and supply high biodiversity ecosystem function than other habitats.For size-spectrum structure in seaweed bed,in our study,we found that the size spectrum of primary production and secondary production were significantly larger than pelagic ecosystem,this phenomenon seems against the conclusion “Greater biomass production by pelagic secondary carnivores supplies more food to potential tertiary carnivores in pelagic habitats than in terrestrial,permitting them to support a fifth trophic level in ecosystems with one-celled primary producers”.In our opinion,the trophic length or trophic level have correlation with the size-spectrum of each level,especially the baseline size spectrum of primary and secondary production.In the coastal waters,the large size spectrum of primary and secondary production may shorten the trophic length and the conclusion of metabolic efficiency in previous study should be revaluated.we summarized the main current techniques of “marine ranching” framework,integrated the relative techniques and framework of bottom-up theory,and proposed marine ranching technical procedure.It entails artificial reef,seaweed reef,float artificial reef,combined marine livestock ecological marine ranching habitat construction,enhancement and enhancement of prey and stock.marine spatial planning to analysis the practical applicability of both relative techniques and technical procedure integration.The above framework and specific technical procedures are proving especially useful and with reference significance in regards to scientific and practical applicability of marine ranching construction.Our researches have three innovations as following:For research methods,to our knowledge,our study is the first study focus on key ecological processes affect estimation of mixture model,such as macroalgae degradation and food preference and establish ecological processes based stable and diet mixture models to quantitative examine an entire community food web structure and function.For our conclusion,our result is the first case study that prove the importance and mechanism of macroalgae and macroalgae detritus in support ecosystem function like support high biomass and diversity For the application of research results,our research framework first establish fundamental food web including graze food chain and detritus food chain and supply a framework that integrated the relative techniques and framework of bottom-up theory,and proposed marine ranching technical procedure.