Patchy Distribution Patterns of Harmful Algal Bloom Species Along Shandong Coast Uncovered via Metabarcoding Analysis of High‐Density Samples

Shandong Province has a long coastline with numerous bays with distinct ecological attributes. Rapid development of the marine economy poses a growing impact on the coastal ecosystems and frequent occurrences of diverse harmful algal blooms (HABs) threatening sustainable economic development as well as the safety of coastal ecosystems and human health. However, the composition of HAB species in this important ocean region remains unexplored. Using high‐density sampling along the Shandong coast region (SCR) and 18S ribosomal DNA V4‐based metabarcoding technology, combined with morphological verification, the diversity, relative abundance, and geographic distribution of HAB species in the SCR were ascertained. This study identified the presence of 95 potential HAB species in the SCR, with 40 HAB species identified for the first time in this region. The distribution patterns of HAB species in this coastal ecosystem showed strong localized and patchy patterns, reflecting the uniqueness of taxon‐specific ecological niches. For example, a key HAB species Noctiluca scintillans was detected in multiple disconnected zones. These results serve as a baseline for evaluating diversity and distribution of HAB species along the SCR, and for comparative studies of the diversity and distribution of HAB species in coastal regions of other provinces.