The Study Of HABs On Nonlinear Stochastic Dynamics And Stochastic Regression Analysis In Bohai Sea

The last-twenty-years is a "golden time" for the China's economy developing.Meanwhile the marine eutrophication state is becoming serious day by day. Theemergence frequency and influencing scale of HABs(harmful algal blooms) areincreasing in the coastal waters of China. Undoubtedly probing into the evolvingcourse of HABs ecosystem is one of the most important ways of exploring themechanism of HABs and accurate prediction of HABs .It is great importantto prevent the harm of HABs, reduce the economy loss and protect thehealth and safety of the people.In this thesis, stochastic stability theory and regression theory as an advancedapproach is used in the research of HABs' evolving process and HABs predication.The detailed research work is as follows:1 Based on food chain relationship of nutrition–autotrophy, we set up adynamical of stochastic model considering the relationship of nutrition–autotrophy, analyze the nonlinear stochastic dynamical stability of themodel solution by using stochastic average method ,FPK method,maxLyapunov exponent method. The conclusion is that random factors(excitations) is oneof the main reasons causing HABs and possibility of HABs is in direct ratio to theintensity of the random excitations.2 Import the concept of Resression Tree, and develop gradient boosting andstochastic theory to regression tree, we use Stochastic Gradient Boosting ofRegression Tree method to predict the HABs. The result indicate that theorder of impact between phytoplankton and environmental factors is airpressure, orthophosphate, field pH,dissolved oxygen, sea surfacetemperature, chlorophyll a, wind speed, silicate.nitrite, salinity,ammonium,oxygen demand, nitrate and biomass hardly-changed with weather.