Dynamic Energy Budget Modeling And Growth Prediction Of Kelp Saccharina Japonica

As aquaculture production has beeing increasing rapidly in recent years,the ecological and environmental problems become more and more serious.For example,in certain aquaculture areas,cultured shellfish become thinner and mass-mortality ocurrs from time to time,erosion starts earlier in cultured kelp Saccharina japonica,and the relaince on chemical treatments in cultured fish have resulted in drug resistance.The series of ecological problems are mainly caused by excessive high density of aquaculture,which may have exceeded the environmental carrying capacity,as well as by the lack of scientific planning and management in aquaculture areas.The issue of aquaculture carrying capacity,that is,the carrying capacity of resource and environment for aquaculture,has become a worldwide concern and a key scientific question for sustainable aquaculture development.In this paper,evolvement of the concept of aquaculture carrying capacity and environmental carrying capacity are elucidated briefly,exemplary work on aquaculture carrying capacity are introduced,comparative studies on carrying capacity for difference aquaculture species,different kind of water bodies and different culture models are made,the development of assessment methods and modeling of aquaculture carrying capacity are analyzed,and its related issues and prospective application in aquaculture governance are discussedin order to promote carrying capacity-based aquaculture spatial planning.In one sense,scientific evaluation and comprehensive application of aquaculture carrying capacity may rely upon the fundamental study on the target species and its requirement of the environmental parameters,and the projected growth of these organisms.Before conducting this study,an overview of the biological characteristics and value of kelp were made.Kelp aquaculture technology and its environmental suitability indicators for cultivation were then summarised,along with the seaweed growth models developed in China and abroad.Taking Sanggou Bay as an example,which is an important aquaculture area along the Yellow Sea and Bohai Sea Coast in China,a Dynamic Energy Budget(DEB)growth model was established for the kelp under large-scale longline culture.So far,international research on kelp mainly focuses on the effects of single environmental parameters such as nutrients,light,and temperature on the growth and photosynthesis of kelp,but there is a lack of model application based on kelp growth curves,as an integrated function of all these environmental parameters.In our study,the key process of the analysis of kelp growth and its relationship with environmental parameters was descrived via the visualization software STELLA.The model can simulate and predict the growth in blade length and dry weight of kelp.This DEB models was also used to analyze the sensitivity of various environmental factors which may affect kelp production.The result may provide reference for optimization of parameters and functions of the model,asl well as for aquaculture suitability assessment of the target organisms.The net growth of kelp depends on two processes including growth and consumption,which,as reflected in the DEB growth model of kelp,equals the difference between gross growth and total consumption.The gross growth is defined as a function of light,temperature,salinity,and internal nutrients(including N and P),while the total consumption includes respiration and kelp erosion.Kelp erosion is the temperature-light intensty related physiological erosion,which is also a genetic property and a survival mechanism.Therefore,kelp pathological erosion was not considered in our model.The parameters in the model were calibrated on the basis of the published literature.At the same time,in order to verify the model simulation results,the environmental parameters and kelp growth data were collected at three sampling stations in Sanggou Bay: the high,middle,and low zones,which were identified according to physical oceanographic characteristics of the water body.As the model demonstrated the need to consider the effect of light intensity on kelp growth,we used TPM to reflect the change of k,so as to optimize dynamic descriptions of the light extinction coefficient in the water column(k).By comparing the actual measurement values of the growth of kelp in the high,middle,and low zones,and the simulation values of the growth curve simulated by model,it was found that the model can predict the growth of kelp very well,and the goodness of fit for length and dry weight(R2)were 0.936,0.963,respectively.As a result,our DEB model can simulate the growth of kelp under different environmental conditions.The individual DEB growth model of kelp can be further evolved into a population growth model,which,in combination with economic sub-models,may contribute to the establishment of aquaculture ecological model,and provide a certain basis for spatial planning and management of aquaculture areas.