Distribution of dinoflagellate cysts in the modern sediments from the coastal aquaculture area and its adjacent oceanic shelf in southeast China

Abstract

Changes in nutrient loading due to coastal aquaculture and the targeted expansion of monitoring programs over the past few decades have amply demonstrated a marked increase in harmful algal blooms (HABs). In this study, viable dinoflagellate cyst composition and assemblages were investigated by evaluating and classifying their distribution patterns in surface sediments of the Fujian aquaculture coastal region of southeast China. The surface sediment at 5 stations during the spring and summer of 2019 to classify the dinoflagellate cysts present and identified 36 species representing six known and three uncertain taxa groups. The highest cyst was recorded at coastal station P11 in the spring (744.7 cysts g−1 DW), while the lowest cyst was observed at coastal station P5 in spring (50.9 cysts g−1 DW). The number and abundance of the heterotrophic species were greater than the autotrophic species, with the highest species volume belonging to the protoperidinioid group. We also detected potentially harmful algae bloom cysts that hold the potential to form their initial blooms in the sediments. It is important to note that six dinoflagellate cysts were found in the waters along the Fujian coast, as compared to historical data. Although the abundance of these cysts was not high, their presence indicates a potentially grave risk for toxic red tides. More alarmingly, these results suggest that seedbeds may trigger future blooms and outbreaks of toxic species in the present study area.