Keywords: Phaeocystis globosa Ecotype Giant colony Genetic diversity Marker pigment

The haptophyte Phaeocystis globosa, an important causative agent of harmful algal blooms globally, exhibits varying morphological and physiological features and high genetic diversity, yet the relationship among these has never been elucidated. In this study, colony sizes and pigment profiles of 19 P. globosa isolates from the Pacific and Atlantic Oceans were determined. Genetic divergence of these strains was analyzed using the chlo-roplast rbcS-rpl27 intergenic spacer, a novel high-resolution molecular marker. Strains could be divided into four genetic clades based on these sequences, or two groups based on colony size and the identity of diagnostic pigments (19 & PRIME;-hexanoyloxyfucoxanthin, hex-fuco, and 19 & PRIME;-butanoyloxyfucoxanthin, but-fuco). Three strains from the South China Sea (SCS), all belonging to the same genetic clade, have unique biological features in forming giant colonies and possessing but-fuco as their diagnostic pigment. Based on these findings, we propose that these SCS strains should be a unique giant-colony ecotype of P. globosa. During the period 2016-2021, more than 1000 rbcS-rpl27 sequences were obtained from 16 P. globosa colony samples and 18 phytoplankton samples containing solitary P. globosa cells in the SCS. Phylogenetic analysis indicated that > 95% of the sequences from P. globosa colonies in the SCS were comprised of the giant-colony ecotype, whereas the genetic diversity of solitary cells was much higher. Results demonstrated that intense blooms of P. globosa featuring giant colonies in the SCS were mainly caused by this giant-colony P. globosa ecotype.

Automated summary

In this study, a high-performance graphene-based microwave absorption material was successfully fabricated using a multilayer resonant structure design and nano-2D material modification. The material exhibits excellent absorption performance in the frequency range of 2-18 GHz, with a maximum absorption rate exceeding 99.5% and a thickness of only 0.5 mm. Furthermore, the material shows good stability and repeatability. This study provides a new approach for the development of efficient, thin, and wideband graphene-based microwave absorption materials.