Growth rates and nitrate uptake of co-occurring red-tide dinoflagellates <italic>Alexandrium affine</italic> and <italic>A. fraterculus</italic> as a function of nitrate concentration under light-dark and continuous light conditions

Abstract

The dinoflagellate genus Alexandrium is known to often form harmful algal blooms causing human illness and largescale mortality of marine organisms. Therefore, the population dynamics of Alexandrium species are of primary concern to scientists and aquaculture farmers. The growth rate of the Alexandrium species is the most important parameter in prediction models and nutrient conditions are critical parameters affecting the growth of phototrophic species. In Korean coastal waters, Alexandrium affine and Alexandrium fraterculus, of similar sizes, often form red-tide patches together. Thus, to understand bloom dynamics of A. affine and A. fraterculus, growth rates and nitrate uptake of each species as a function of nitrate (NO 3) concentration at 100 μmol photons m-2 s-1 under 14-h light : 10-h dark and continuous light conditions were determined using a nutrient repletion method. With increasing NO 3 concentration, growth rates and NO 3 uptake of A. affine or A. fraterculus increased, but became saturated. Under light : dark conditions, the maximum growth rates of A. affine and A. fraterculus were 0.45 and 0.42 d-1 , respectively. However, under continuous light conditions, the maximum growth rate of A. affine slightly increased to 0.46 d-1 , but that of A. fraterculus largely decreased. Furthermore, the maximum nitrate uptake of A. affine and A. fraterculus under light : dark conditions were 12.9 and 30.1 pM cell-1 d-1 , respectively. The maximum nitrate uptake of A. affine under continuous light conditions was 16.4 pM cell-1 d-1. Thus, A. affine and A. fraterculus have similar maximum growth rates at the given NO 3 concentration ranges, but they have different maximum nitrate uptake rates. A. affine may have a higher conversion rate of NO 3 to body nitrogen than A. fraterculus. Moreover, a longer exposure time to the light may confer an advantage to A. affine over A. fraterculus.

Molecular Identification and Toxin Analysis of Alexandrium spp. in the Beibu Gulf: First Report of Toxic A. tamiyavanichii in Chinese Coastal Waters

“…Two strains of Beibu Gulf A. affine were lost during culture maintenance, so PSTs could not be analyzed. Current literature suggests that A. affine is largely nontoxic [ 16 , 44 ] or only potentially toxic [ 45 ]. However, A. affine strains with low PST toxin content (<1.0–2.28 fmol/cell), including NeoSTX, STX, and GTX1-4, have been isolated from Ha Long Bay, Vietnam, near the Beibu Gulf [ 46 ].…”

Saturating relationship between phytoplankton growth rate and nutrient concentration explained by macromolecular allocation

“…We used data from published papers with 12 species of phytoplankton inlcuding Alexandrium affine, Alexandrium fracterculus, Anomoeoneis costata, Asterionella formosa, Cyclotella quillensis, Cyclotella sp , Cymbella pusilla, Fragilaria crotonensis, Microcystis aeruginosa, Staurosirella pinnata, Synechocystis sp. PCC6803 , and Tetracyclus glans under nitrogen limited conditions ( Kim et al., 2015 ; Lee et al., 2019 ; Michel et al., 2006 ; Saros and Fritz, 2000 ; Sugimoto et al., 2015 ) (Table S1). Together, these provided a large range of phytoplankton taxa grown under NO 3 − limited conditions to test with both methods.…”

“…PCC6803 ( Kim et al., 2015 ). (B) Alexandrium fracterculus ( Lee et al., 2019 ). (C) Fragilaria crotonensis ( Michel et al., 2006 ).…”

Feeding by common heterotrophic protist predators on seven <italic>Prorocentrum</italic> species

“…The growth and mortality of red-tide dinoflagellates due to predation are two critical parameters in their population dynamics (Franklin et al 2006, Jeong et al 2015. While there have been many studies reporting the growth rates of red-tide dinoflagellates, there have been fewer studies on their mortality due to predation (Smayda 1997, Matsubara et al 2007, Lee et al 2019a; the mortality of red-tide dinoflagellates due to predation should be explored.…”