Difference of interpretation of dynamics of diatoms community based on the morphological and metagenomic analyses in Tongyeong coast

Abstract

Diatom identification based on their morphology often leads to the misinferring of their ecological and biogeochemical roles, because it is difficult to positively identify the species when the presence of cryptic or nano-sized diatoms. Recently, next-generation sequencing (NGS) methods provide a chance to overcome the limitations from morphological analysis. We here examined the long-term dynamics of diatom communities at the site of Tongyeong coast during 45 months using a combination of LM and NGS methods. The number of species in each month is almost always higher in NGS than LM, while the accumulated total species number during 45 months are higher in LM than NGS. NGS method interestingly reproduce the diatom dynamics following Margalef’s mandala in a typical three stages during winter to spring: occurrence of nanoplanktonic diatoms such as Minidiscus comicus, Brockmaniella brockmannii and Skeletonema costatum in winter (December to February), following medium-sized Chaetoceros contortus, C. constrictus and C. diadema in spring (March to April), finally Leptocylindrus convexus and Cerataulina pelagica in late spring (May). While the seasonal dynamics of diatom did not present in LM method. Although in LM certain tendency of diatom dynamics are not able to monitored, it is able to detect the episodic event of diatom blooms such as Pseudo-nitzschia in late summer or autumn. With the combination of LM and NGS results, we illustrate and summarize the seasonal cycles of diatom assemblages in coastal water based on modified Grime’s C-S-R model.