Spatial Distribution of Phytoplankton Community Composition and Their Correlations with Environmental Drivers in Taiwan Strait of Southeast China

Yong Zhang,Jin-Zhu Su,Kai G. Schulz,Yu-Ping Su,Hong Lin,Balaji P. Barathan,Wan-Ning Zheng,Yang-Chun Xu

doi:10.3390/d12110433

Abstract

Large-scale dinoflagellate blooms have appeared in recent decades in the Taiwan Strait, Southeast China. To study spatial variability of phytoplankton community composition, physical and chemical environmental drivers in surface seawater of the Taiwan Strait, we conducted cruises in May and July 2019. Cell numbers of dinoflagellates were significantly higher than that of diatoms in most sampling stations during the cruise in May, whereas diatoms were the major contributor to autotrophic biomass in July. Phytoplankton community shifted from a dinoflagellate- and diatom-dominated system in May to diatom dominance in July. The dominant phytoplankton species (genera) were the harmful algal bloom dinoflagellates Prorocentrum donghaiense and Scrippsiella trochoidea and the diatoms Coscinodiscus in May, and Rhizosolenia, Pseudo-nitzschia, and Guinardia in July. Cell densities of dinoflagellates and P. donghaiense reduced exponentially with increasing seawater temperature and salinity and decreasing dissolved inorganic nitrogen (DIN) concentrations. Based on the results of our work and previous studies, it becomes obvious that harmful dinoflagellate blooms are likely to be a major component of the planktonic food web in the Taiwan Strait at a temperature of 17.0–23.0 °C, a salinity of 29.0–33.0 psu, and a DIN concentration higher than 2.0 μmol L–1.

Highlights

Large-scale harmful algal blooms (HABs) have become frequent worldwide and often cause the seawater to be reddish-brown, the name red tides [1]
Measured dissolved oxygen (DO) concentrations showed an opposite trend to surface seawater temperature (SST), with the values decreasing from 8.90 mg L–1 at station M15 to 8.20 mg L–1 at station P17 (Figure 2c). pHTotal values varied from
Our results indicate that when temperature and salinity was lower than 23.0 ◦ C and 33.0 psu, respectively, dinoflagellates had a competitive advantage in Taiwan Strait (Figure S1)

Summary

Introduction

Large-scale harmful algal blooms (HABs) have become frequent worldwide and often cause the seawater to be reddish-brown, the name red tides [1]. Several studies have put forward hypotheses for the formation and dispersion of dinoflagellate blooms [7,8,9,10] They divided large-scale dinoflagellate blooms into four stages: initiation, development, proliferation, and dispersion [11]. Long-term monitoring studies have confirmed that temperature and salinity have large impacts on cell proliferation of dinoflagellates and play crucial roles in the occurrence and demise of blooms [7,12]. A zero-dimensional numerical model suggests that in comparison to temperature and light intensity, phosphate limitation is the major factor leading to the formation of dinoflagellate blooms, and high nitrate concentration play an important role for its development and proliferation [8,13].

Methods

Results

Discussion

Conclusion