Distribution of harmful dinoflagellate cysts in the surface sediments of Daya Bay of the South China Sea and their relationship to environmental factors.

Abstract To investigate the distribution of dinoflagellate cyst and their relationship with environmental factors, surface sediments were collected from 14 stations of Daya Bay of the South China Sea. In total, 44 cyst species and 3 uncertain taxa were identified and the total abundance ranged from 79 to 819 cysts g−1 dry weight (DW), showing a decreasing trend from the north-west to the south-east of the bay. Based on cluster analysis, three zones were identified. In Zone I (inner bay), the heterotrophic cyst dominated and warm-water species (Alexandrium minutum/affine and Gonyaulax spinifera) were observed. In Zone III (bay mouth), cyst assemblage was characterized by halophilic taxon Protoperidinium subinerme. Correlation analysis showed that seawater temperature, salinity and sediment particle size had the greatest impacts on the composition and distribution of cyst assemblage. Furthermore, several toxic species, including Lingulodinium polyedrum , Alexandrium spp. and Gymnodinium catenatum , were observed at most stations, indicating a wide distribution and potential risk of harmful algal blooms in Daya Bay. Highlights • Significant spatial distribution of dinoflagellate cyst in surface sediment was observed across the Daya Bay. • Seawater temperature, salinity, and sediment particle size had great impact on the composition and distribution of cysts. • Several toxic and harmful dinoflagellate species have only been observed as resting cyst in sediment. [ABSTRACT FROM AUTHOR]