Spatial and temporal characteristics of harmful algal blooms in Zhejiang Province waters during 1933–2018

Abstract

ABSTRACT Harmful algal bloom (HAB) data included events caused by toxic species and non-toxic species, and was collected from red tide outbreaks in the Zhejiang Province coastal waters during 1933–2018. The geostatistical tools in Geographic Information System (GIS) were used to analyse the spatial and temporal distributions of these red tide events and map the distribution of these events in the study area. The results show that: (1) three areas had very-high frequency of red tide: Shengshan waters, Eastern waters of Zhujiajian and Nanji Islands waters. (2) The red tide occurrences exhibited significant seasonality: May is the most likely time for a red tide outbreak in Zhejiang waters. (3) Prorocentrum donghaiense occurred 182 times, Karenia mikimotoi occurred 64 times and Skeletonema costatum occurred 59 times in the total events. Prorocentrum donghaiense and Karenia mikimotoi are the algae species that are most prone to forming red tides in Zhejiang waters. This study utilized a visual approach to identify the scope, distribution and characteristics of red tide in the Zhejiang Province coastal waters over the past 85 years more fully, thus providing useful information to support the monitoring and management programme for HABs.