2001-2020年福建沿海赤潮灾害分级和时空分布特征研究

The spatial-temporal distribution and hazard grading of red tides in Fujian coast waters during 2001-2020

利用2001-2020年福建沿海赤潮事件记录资料和自然灾害风险判定方法,根据赤潮成灾面积、持续时间、危害类型、渔业直接经济损失等指标综合计算赤潮灾害指数。基于自然断点法,对赤潮灾害指数进行Ⅰ级、Ⅱ级、Ⅲ级、Ⅳ级等4个灾害级别分等定级。系统分析了福建沿海赤潮生物种类、时空分布特征和演变规律。结果表明:(1)2001-2020年福建沿海赤潮以灾害程度较轻的Ⅰ级和Ⅱ级为主,灾害程度较重的Ⅲ级和Ⅳ级仅占总次数的8.9%,但其造成的渔业直接经济损失达总损失的95.0%。(2)赤潮暴发次数和面积总体呈现下降趋势,但Ⅲ级和Ⅳ级灾害频次呈现波动特征。(3)季节尺度上表现为单波峰特征,5-6月是赤潮灾害最为严重的时段,赤潮暴发次数、面积和持续时间占总体的比例分别为73.3%、84.6%和74.9%,Ⅲ级和Ⅳ级灾害占总次数的95.2%。(4)空间尺度上,福州、宁德、厦门沿海赤潮累计次数和规模较大,但Ⅲ级和Ⅳ级赤潮灾害主要分布在泉州以北的福建沿海,泉州以南的福建海域赤潮灾害级别整体较低。(5)2001-2020年福建沿海赤潮原因种逐渐增多,硅藻占比减小、甲藻占比升高,有毒赤潮主要出现在宁德、福州、泉州海域,以米氏凯伦藻(Karenia mikimotoi)引发居多。(6)硅藻赤潮主要暴发在峡湾和海湾海域,而甲藻赤潮在峡湾、海湾和开阔的近岸海域均易暴发,近年来甲藻赤潮暴发位置呈现由福建北部向南部沿海扩张的趋势。引起这些变化的原因据推测与全球气候变化及福建近岸海域环境的变化密切相关。

Based on historical records of red tides in Fujian coast waters(2001-2020)and the method of natural disaster risk determination,the disaster index of red tide is comprehensively calculated according to inundated area,duration,category,and direct economic loss of fishery.Using the natural breakpoint method,the red tide along Fujian coast waters can be divided into four level(gradeⅠ,Ⅱ,Ⅲ,andⅣ).The biological species,temporal and spatial distribution characteristics,evolution law of red tide in Fujian coast waters are analyzed.The results showed that:(1)The red tide of gradeⅠandⅡwere the main disaster in Fujian coast waters.Red tide of gradeⅢorⅣonly accounted for 8.9%of total occurrence,which caused 95.0%of direct economic fishery loss.(2)The frequency and scale of red tide were decreasing,but the frequency of red tide of gradeⅢandⅣappeared an obvious fluctuation.(3)At seasonal scale,the red tide was characterized by a single peak at inter-season-al scales.The frequent occurrence of red tide was in May and June.The times,area,and duration of red tide in these two month accounted for 73.3%,84.6%and 74.9%,respectively.And the red tide of gradeⅢandⅣaccounted for 95.2%of the total number.(4)At spatial scale,the incidence of red tide most occurred in Fuzhou,Ningde,and Xiamen coast.Red tide of gradeⅢandⅣwere mainly distributed in the north of Quanzhou.The disaster grade of red tide in south of Quanzhou was lower.(5)The biological species of red tide increased during the recent 20 years.The proportion of diatom decreased,while the proportion of dinoflagellate increased.Toxic red tides,especially Karenia mikimotoi,mainly occurred in Ningde,Fuzhou and Quanzhou coast waters.(6)Diatom mainly occurred in fjords and bays,and dinoflagellate may also occur in open coast waters.In recent years,the location of dinoflagellate had expanded from north to south.These changes was assumed to be closely related to the changes of global climate and coastal environment in Fujian coast waters.