More than half of the 153 documented toxic harmful algal bloom species (HABs) are found in the Gulf of Mexico and most of these HABs are observed on the Texas coast. Using a metabarcoding approach, samples from the Texas Observatory for Algal Succession Time series (TOAST) were examined for the presence of HABs. Metabarcoding is a rapid and effective means to investigate microplankton community composition and species diversity. In this study we compared HAB diversity estimated from 18S long-read sequences obtained from the minION with diversity estimated from MiSeq short sequences using V4 and V8-V9 markers of 18S rDNA. Seasonal variation in diversity over the four-year period 2019-2022 at TOAST was compared with results from a 1-day cruise along the Texas coast one month after the extreme flooding event following Hurricane Harvey (2017) and a sample collected one month after Hurricane Nicholas (2021). Results show that full-length sequences provide improved discrimination among closely related species and that the diversity of HAB species increases after an extreme event. Given the anticipated increase in the number and intensity of hurricanes with climate change, it is important to determine how this will impact the diversity and potential for blooms of harmful algae in the Gulf of Mexico as well as other parts of the world.
Campbell et al. (Fri,) studied this question.