Program

Brown tides caused by the excessive growth of the pelagophyte Aureococcus anophagefferens have occurred frequently in Qinhuangdao, China, since 2009. In this study, we conducted environmental sampling to characterize the environmental factors of the coastal waters of Qinhuangdao and measured the abundance of A. anophagefferens and M. polymorphus using real-time quantitative PCR. Our primary objectives were to (1) investigate temporal and spatial variations of A. anophagefferens and M. polymorphus in our study area; (2) explore the potential links between the abundance of A. anophagefferens and M. polymorphus and environmental parameters; and (3) understand the influence of brown tides on phytoplankton community composition. The results showed that A. anophagefferens reached peak densities in July. Brown tides occurred in the coastal waters of Funing and Changli, and the main affected areas shifted from south to north throughout the experiment. The A. anophagefferens brown tide event was not monospecific, as M. polymorphus and Prorocentrum minimum were also observed. A redundancy analysis (RDA) indicated that decreasing concentrations of dissolved inorganic nitrogen (DIN) and increasing concentrations of the available organic nitrogen compounds (urea, dissolved free amino acids (DFAA) and dissolved combined amino acids (DCAA)) from March to June may have resulted in the outbreak of the brown bloom of A. anophagefferens, coinciding with a reduction in the community diversity of phytoplankton in the coastal waters of Qinhuangdao.