Effects of light and temperature on the growth of Takayama helix (Dinophyceae): mixotrophy as a survival strategy against photoinhibition

Abstract

Takayama helix is a mixotrophic dinoflagellate that can feed on diverse algal prey. We explored the effects of light intensity and water temperature, two important physical factors, on its autotrophic and mixotrophic growth rates when fed on Alexandrium minutum CCMP1888. Both the autotrophic and mixotrophic growth rates and ingestion rates of T. helix on A. minutum were significantly affected by photon flux density. Positive growth rates of T. helix at 6–58 μmol photons · m−2 · s−1 were observed in both the autotrophic (maximum rate = 0.2 · d−1) and mixotrophic modes (0.4 · d−1). Of course, it did not grow both autotrophically and mixotrophically in complete darkness. At ≥247 μmol photons · m−2 · s−1, the autotrophic growth rates were negative (i.e., photoinhibition), but mixotrophy turned these negative rates to positive. Both autotrophic and mixotrophic growth and ingestion rates were significantly affected by water temperature. Under both autotrophic and mixotrophic conditions, it grew at 15–28°C, but not at ≤10 or 30°C. Therefore, both light intensity and temperature are critical factors affecting the survival and growth of T. helix.

Eco-Evolutionary Perspectives on Mixoplankton

“…Higher temperature implies higher metabolic rates and concomitantly an increased need for energy, and possible stress incurrence. Studies have indeed shown higher ingestion rates in response to temperature increase in many species (Princiotta et al, 2016;Cabrerizo et al, 2019;Ok et al, 2019). This validates the applicability of the general theory of metabolism in marine protists.…”

“…Karlodinium veneficum, and some other dinoflagellates, cannot grow (or are only sustained) in the dark even when prey is available, that is to say, it is an obligate phototroph. Other dinoflagellate species, or chrysophytes such as Ochromonas sp., can grow in constant darkness if supplied with food (Caron et al, 1993;Ok et al, 2019). Thus, predation can, but does not always, compensate for the inability to use chloroplasts in the dark.…”

Comparative Transcriptome Analysis of the Phototrophic Dinoflagellate Biecheleriopsis adriatica Grown Under Optimal Temperature and Cold and Heat Stress

“…Temperature is a major factor affecting dinoflagellate survival, growth rate, and abundance (Hinder et al, 2012;Kohli et al, 2014;Ok et al, 2019;Jang and Jeong, 2020;You et al, 2020). In particular, many dinoflagellates cannot survive in very cold or hot waters (Matsubara et al, 2007;Kibler et al, 2012;Xu et al, 2016;Lim et al, 2019;Kang et al, 2020a).…”

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

“…Thus, the amount of photons produced by a continuous light at 100 μmol photons m -2 s -1 is equivalent to that at 140 μmol photons m -2 s -1 under 14-h light : 10-h dark cycle. The autotrophic growth of the mixotrophic dinoflagellate Takayama helix is known to be inhibited at 115 μmol photons m -2 s -1 under 14-h light : 10-h dark cycle (Ok et al 2019). Therefore, it is worthwhile to explore possible inhibition of growth of A. fraterculus at high light intensities under 14-h light : 10-h dark cycle to test this hypothesis.…”