Risk Assessment Of Harmful Algal Blooms

As a kind of marine ecological hazard,harmful algal blooms(HABs)will not only threaten the safety of the ecological environment in the coast sea area,cause partial disruption of the marine food chain and destroy the balance of the ecosystem,but also damage human health and economic development.HABs takes manpower,material and financial resources originally used to develop economy for disaster relief,disaster resistance and post-disaster recovery.It has drawn wide attention of governments and scientific community in various countries.At present,HABs,which is a public nuisance in the world,have occurred frequently in many coastal waters of the world.It has spread all over the coastal provinces and cities in China,causing China to become one of the countries seriously affected by HABs.In this context,it is necessary to carry out research on the risk assessment of HABs in order to maintain the safety of marine ecological environment and ensure the healthy economic development.Research area,Ningde coast,is located in the northeastern coast of Fujian Province,including Jiaocheng,Fu'an,Xiapu and Fuding coastal waters and beaches.Ningde coast,with Sandu Bay,Shacheng Harbor,Sansha Bay,Funing Bay and Qingchuan Bay and many other harbor,has excellent natural environment,rich marine resources and diverse ecological types.With its unique geographical and environmental advantages,Ningde coast has become an important base for aquaculture industry.However,because of the rapid development of the marine aquaculture industry,HABs occurred frequently in Ningde sea area in recent years,which seriously damaging the marine ecological balance and aquatic resources.According to the 2014 marine environmental monitoring and evaluation results of Ningde Sansha Bay HABs monitoring area:(1)most of the phosphate,inorganic nitrogen content of the HABs monitoring area can only meet the third or fourth class of sea water quality standard;(2)some sites even exceed the fourth class of sea water quality standard;(3)all stations in the monitoring months are mostly in high level of eutrophication,which can easily lead to HABs and affect the development of marine economy.In the past,the marine eco-environmental quality,biological community,HABs characteristics,causes and prediction of coastal waters in Ningde have been studied,but the risk of HABs has not been reported yet.In view of this,this study took the Ningde coast,Fujian Province as the research object to carry on risk assessment of HABs.The index systems of risk assessment of HABs were established based on leading,measurable and available principles.The weighs of evaluation indexes were determined by entropy method.In addition,hazard assessment model,disaster inducing fator assessment model,vulnerability assessment of disaster-bearing body model and risk assessment model were set up,respectively.Finally,we utilized GIS platform to realize visualization of the assessment results.This study provided the basis for management of HABs and planning of aquaculture industry of Ningde coastal area.The main conclusions of this study are as follows:(1)The bays of Ningde are in different levels of eutrophication.The eutrophication degree of Shacheng Harbor,Qingchuan Bay,Dongwuyang Bay,Guanjingyang Bay and Lumen Harbour are most serious.The overall trend is reduced from coast to outer sea.(2)The risk of HABs in Ningde coast is evaluated by regional disaster system and theory of geostatistical analysis.The evaluation index system is consist of the disaster factors,disaster inducing factors and disaster-bearing bodies.The weight of each indicator is determined by entropy method.Entropy method is an objective and scientific analysis method.Entropy method,as it reflects the utility value of index information entropy profoundly,has higher credibility than the widely used subjective analytic methods such as analytic hierarchy process and Delphi method.(3)The result show that harmful algal blooms risk degree is the same as the trend of eutrophication.The extreme value of HABs hazard degree is distributed in Shacheng Harbour,Qingchuan Bay,Dongwuyang Bay,Guanjingyang Bay,Sandu Bay,Lumen Harbour.The overall trend is reduced from coast to outer sea.The hazard of HABs is high in Sansha Bay.In terms of the vulnerability of disaster-bearing bodies,Fuding coast is highly vulnerable area,Jiaocheng coast and Xiapu coast are medium vulnerable areas,and Fu'an coast is low vulnerability area.At the risk level of the HABs,the extreme high risk of HABs are located in the vicinity of Qinghchuan Bay and the inside of Shacheng Harbour.The outside of Shacheng Harbour,Dongwuyang Bay,Guanjingyang Bay,Sanduao Bay located in Sansha Bay are high risk.The HABs risk in the Baima Harbour located in Sansha Bay is low.Funing Bay is moderately risky.The results of the assessment are consistent with the historical data of HABs,the actual situation of Ningde coast and the conclusions of the relevant literatures,which proves that the methods we used are feasible and practical.This study can provide technical support for HABs disaster monitoring,disaster prevention and mitigation and mariculture of Ningde coast.(4)On the platform of GIS,we realized the visualization of hazard degree of disaster-causing factors of HABs disaster,vulnerability degree of disaster-bearing body and risk of HABs disaster in Ningde coast,which made the evaluation results more intuitive.