Uptake of Inorganic and Organic Nitrogen Sources by Dinophysis acuminata and D. acuta

Abstract

Dinoflagellate species of Dinophysis are obligate mixotrophs that require light, nutrients, and prey for sustained growth. Information about their nitrogenous nutrient preferences and their uptake kinetics are scarce. This study aimed to determine the preferred nitrogen sources in cultures of D. acuminata and D. acuta strains from the Galician Rías Baixas (NW Spain) and to compare their uptake kinetics. Well-fed versus starved cultures of D. acuminata and D. acuta were supplied with N15 labeled inorganic (nitrate, ammonium) and organic (urea) nutrients. Both species showed a preference for ammonium and urea whereas uptake of nitrate was negligible. Uptake rates by well-fed cells of D. acuminata and D. acuta were 200% and 50% higher, respectively, than by starved cells. Uptake of urea by D. acuminata was significantly higher than that of ammonium in both nutritional conditions. In contrast, similar uptake rates of both compounds were observed in D. acuta. The apparent inability of Dinophysis to take up nitrate suggests the existence of incomplete nitrate-reducing and assimilatory pathways, in line with the paucity of nitrate transporter homologs in the D. acuminata reference transcriptome. Results derived from this study will contribute to understand Harmful Algal Blooms succession and differences in the spatio-temporal distribution of the two Dinophysis species when they co-occur in stratified scenarios.

Niche differentiation of Dinophysis acuta and D. acuminata in a stratified fjord

“…These preferences were confirmed in laboratory experiments (Hattenrath-Lehmann and Gobler 2015). García-Portela et al (2020) showed that neither D. acuminata nor D. acuta take up nitrate. A review of transcriptomic databases showed a paucity of nitrate transporter homologs in D. acuminata.…”

“…These observation suggested that the two species have different physiological and behavioural adaptations. Laboratory culture studies confirmed the different responses of the two species to light intensity and quality (García-Portela et al, 2018;Kim et al, 2008), turbulence (García-Portela et al, 2019) and nitrogen sources (García-Portela et al, 2020;Hattenrath-Lehmann and Gobler, 2015).…”

Acquired Phototrophy and Its Implications for Bloom Dynamics of the Teleaulax-Mesodinium-Dinophysis-Complex

“…All the plankton functional types could uptake NH 4 + . All except Dinophysis could also use NO 3 − as this genus seems unable to use this N-source García-Portela et al, 2020). However, the construct of the Dinophysis model is based on the generic construct of a pSNCM (Anschütz and Flynn, 2020) and, therefore, should evidence of Dinopysis using NO 3 − become available, then the model can be readily modified to enable NO 3 − uptake for Dinophysis just as it is enabled for the other pSNCM, Mesodinium.…”

Effect of a short-term salinity stress on the growth, biovolume, toxins, osmolytes and metabolite profiles on three strains of the Dinophysis acuminata-complex (Dinophysis cf. sacculus)

“…Since the successful mixotrophic culture of D. acuminata by Park et al in 2006, several laboratory studies have been carried out on Dinophysis about the effects of (1) abiotic factors, such as nutrient availability, concentration and uptake (e.g. Nagai et al, 2008, García-Portela et al, 2020, temperature (e.g. Basti et al, 2018, Kamiyama et al, 2010, salinity (Fiorendino et al, 2020), light intensity and quality (e.g.…”

“…Smith et al, 2018), prey concentration (e.g. Kim et al, 2008, Smith et al, 2018 and prey exudates (Gao et al, 2019;Nagai et al, 2011), nutritional status (García-Portela et al, 2020) or (3) geographical origin (Fux et al, 2011) on the physiology and/or toxicity. Nevertheless, laboratory studies exploring the short-term effect of salinity stress on physiology and metabolites production (including toxins) are still lacking.…”