AUTHOR=Lum Wai Mun , Sakamoto Setsuko , Yuasa Koki , Takahashi Kazuya , Kuwata Koyo , Kodama Taketoshi , Katayama Tomoyo , Leaw Chui Pin , Lim Po Teen , Takahashi Kazutaka , Iwataki Mitsunori 

TITLE=Comparative effects of temperature and salinity on growth of four harmful Chattonella spp. (Raphidophyceae) from tropical Asian waters

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1127871

DOI=10.3389/fmars.2023.1127871

ISSN=2296-7745

ABSTRACT=<p>In Asia, four harmful raphidophyte species, <italic>Chattonella malayana</italic>, <italic>C. marina</italic>, <italic>C. subsalsa</italic>, and <italic>C. tenuiplastida</italic>, coexist in the tropical waters but only <italic>C. marina</italic> was detected in temperate waters. This occurrence pattern pointed to a potentially distinct ecophysiological niche occupancy and possible species dispersion. The growth physiology of these species isolated from tropical Southeast Asia was investigated using unialgal cultures in ten temperatures (13.0–35.5°C) and five salinities (15–35) to better understand the factors driving their distribution. The highest maximum specific growth rates were observed in <italic>C. subsalsa</italic> (0.65 ± 0.01 d<sup>-1</sup>), followed by <italic>C. malayana</italic> (0.47 ± 0.03 d<sup>-1</sup>), <italic>C. marina</italic> (0.45 ± 0.02 d<sup>-1</sup>), and <italic>C. tenuiplastida</italic> (0.39 ± 0.01 d<sup>-1</sup>). Their optimal temperatures were 28.0, 30.5, 25.5, and 30.5°C, respectively, of which <italic>C. marina</italic> preferred colder water. <italic>C. subsalsa</italic> exhibited a wider growth temperature range (20.5–35.5°C), followed by <italic>C. marina</italic> (20.5–30.5°C), <italic>C. tenuiplastida</italic> (23.0–33.0°C), and <italic>C. malayana</italic> (25.5–33.0°C). Optimal salinities were similar between <italic>C. subsalsa</italic> and <italic>C. malayana</italic> (30), and between <italic>C. marina</italic> and <italic>C. tenuiplastida</italic> (25), but <italic>C. subsalsa</italic> and <italic>C. marina</italic> exhibited a similar growth salinity range of 15–35, while <italic>C. malayana</italic> and <italic>C. tenuiplastida</italic> was 20–35. High values of F<sub>v</sub>/F<sub>m</sub> were observed in <italic>C. subsalsa</italic> and <italic>C. marina</italic> (&gt; 0.5) in all tested conditions, but F<sub>v</sub>/F<sub>m</sub> of <italic>C. malayana</italic> and <italic>C. tenuiplastida</italic> were significantly lower at 20.5°C. All four species achieved a maximum cell density of &gt; 10<sup>4</sup> cells mL<sup>-1</sup> in their optimal conditions. Optimal temperatures in <italic>C. subsalsa</italic> and <italic>C. marina</italic> were identical to previous reports. The high adaptability of <italic>C. subsalsa</italic> in various temperatures and salinities suggests its high competitiveness and bloom potential. The high adaptability of <italic>C. marina</italic> in colder waters compared to other species likely contributes to its wide distribution in the temperate Asian waters. The narrow temperature window of <italic>C. malayana</italic> and <italic>C. tenuiplastida</italic> suggests their endemicity and limited distribution in the tropical waters. This study provides evidence about the occurrences and bloom potential of <italic>Chattonella</italic> spp. in Asia, but the endemicity versus dispersion issue remains unresolved.</p>