Growth rates of Korean strains of 10 marine diatom species under different temperature and light conditions

Diatoms are major contributors to marine primary production and frequently dominate phytoplankton blooms. However, growth rate data remain limited for many diatom species, and strain-level variability remains insufficiently documented. We investigated the growth rates of ten marine diatom species isolated from Korean coastal waters under independently manipulated temperature (20 and 25°C) and light (50 and 100 μmol photons m-2 s-1) conditions, representative of conditions under which temperate marine diatoms actively grow. The species examined ranged from taxa for which published growth-rate data are limited or unavailable (Detonula pumila and Pleurosigma normanii), taxa with only a few published growth-rate studies (Chaetoceros peruvianus, Paralia sulcata, and Thalassiosira minuscula), and widely studied species (Cylindrotheca closterium, Phaeodactylum tricornutum, Skeletonema pseudocostatum, and Skeletonema dohrnii), as well as Navicula sp. Growth rates and maximum observed cell densities varied markedly among species, ranging from 0.20 to 1.78 d-1 and 0.1 × 104 to 583.5 × 104 cells mL-1, respectively. Responses to temperature and light differed markedly among species, with both the magnitude and direction of change varying substantially. Furthermore, growth rate and maximum observed cell density did not always respond consistently within the same species, indicating that these two growth-related traits may respond differently to environmental conditions. These findings demonstrate that responses to temperature and light vary substantially among marine diatoms and cannot be readily generalized across taxa. Comparisons with previous studies also suggest possible strain-level variability, emphasizing the need to consider both species- and strain-level variation when predicting phytoplankton responses to environmental change.