Feeding by common heterotrophic protists on the mixotrophic alga <i>Gymnodinium smaydae</i> (Dinophyceae), one of the fastest growing dinoflagellates

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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.

Section: Discussionsupporting

confidence: 53%

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

Lee¹,

Jeong²,

Kang³

et al. 2019

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“…The growth and ingestion rates of G. smaydae on H. rotundata and H. steinii in the laboratory have been previously reported (Lee et al 2014a). Furthermore, the growth and ingestion rates of the heterotrophic dinoflagellate O. marina on G. smaydae have also been reported (Jeong et al 2018). However, understanding the population dynamics of G. smaydae and its roles in the marine planktonic community was difficult owing to the lack of abundance of G. smaydae in the field.…”

Section: Stmentioning

confidence: 96%

“…Some heterotrophic protists such as the common heterotrophic dinoflagellates Oxyrrhis marina and Gyrodinium dominans and the naked ciliate Pelagostrobilidium sp. are able to feed on G. smaydae, but are not preferred prey for these predators (Jeong et al 2018). Therefore, based on the results of previous laboratory experiments, the population dynamics of G. smaydae can be suggested to be affected by prey availability, water temperature, and light intensity.…”

Section: Introductionmentioning

confidence: 99%

Spatial-temporal distributions of the newly described mixotrophic dinoflagellate Gymnodinium smaydae in Korean coastal waters

Lee¹,

Jeong²,

Ok³

et al. 2020

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Gymnodinium smaydae is a newly described mixotrophic dinoflagellate that feeds on only Heterocapsa spp. and Scrippsiella acuminata among 19 tested algal prey. It is one of the fastest growing dinoflagellates when feeding, but does not grow well without prey. To investigate its spatial-temporal distributions in Korean waters, we quantified its abundance in water samples that were seasonally collected from 28 stations along the Korean Peninsula from April 2015 to October 2018, using quantitative real-time polymerase chain reactions. This dinoflagellate had a wide distribution, as reflected by the detection of G. smaydae cells at 23 of the sampling stations. However, this distribution had a strong seasonality; it was detected at 21 stations in the summer and only one station in winter. The abundance of G. smaydae was significantly and positively correlated with chlorophyll a concentration as well as with water temperature. However, there were no significant correlations between the abundance of G. smaydae and salinity, concentrations of nutrients, or dissolved oxygen concentration. During the study period, G. smaydae was present when water temperatures were 7.6-28.0°C, salinities were 9.6-34.1, concentrations of NO 3 were not detectable-106.0 μM, and concentrations of PO 4 were not detectable-3.4 μM. The highest abundance of G. smaydae was 18.5 cells mL-1 in the coastal waters of Jinhae in July 2017 when the chlorophyll a concentration was 127 mg m-3 and water temperature was 23.8°C. Therefore, the spatialtemporal distribution of G. smaydae in Korean coastal waters may be affected by chlorophyll a concentration and water temperature.

“…Heterotrophic dinoflagellates (HTDs) and ciliates are major heterotrophic protist groups (Jeong et al 1999, volumes of the HTD predators were estimated using the methods of Jang et al (2016) for A. glandula; Kim and Jeong (2004) and Yoo et al (2013b) for G. dominans and G. moestrupii, respectively; Jeong et al (2007) for L. masanensis and P. piscicida; Ok et al (2017) for O. rotunda; Jeong et al (2008b) for O. marina; Jeong et al (2001b) for P. kofoidii; Kim et al (2019) for Strombidinopsis sp. ; and Jeong et al (2018b) for Pelagostrobilidium sp. (Table 1).…”

Section: Preparation Of Experimental Organismsmentioning

confidence: 99%

“…are also common naked ciliates in many marine environments (Strom and Buskey 1993, Claessens et al 2008, Taylor et al 2008, Watts et al 2010, Calbet et al 2013, Tillmann and Hoppenrath 2013, Yoo et al 2013b). There are usually large variations in feeding occurrence and growth and ingestion rates of heterotrophic protist predator species when diverse prey species are provided (Hansen 1992, Menden-Deuer et al 2005, Jeong et al 2018a, 2018b. Thus, it is worthwhile to explore the interactions between B. adriatica and these potential heterotrophic protist predators.…”

Section: Introductionmentioning

confidence: 99%

Feeding by common heterotrophic protists on the phototrophic dinoflagellate Biecheleriopsis adriatica (Suessiaceae) compared to that of other suessioid dinoflagellates

Kang¹,

Jeong²,

Jang³

et al. 2019

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The species in the dinoflagellate order Suessiales have 5-24 latitudinal paraplate series and include many fossil and extant species. There have been a few studies on the ecophysiology of the phototrophic species Biecheleriopsis adriatica, and no study on its predators. Thus, we explored the feeding occurrence by common heterotrophic protists on B. adriatica and the growth and ingestion rates of the heterotrophic dinoflagellate Oxyrrhis marina on B. adriatica BATY06 as a function of prey concentration. The common heterotrophic dinoflagellates Aduncodinium glandula, O. marina, Gyrodinium dominans, Gyrodinium moestrupii, Luciella masanensis, Pfiesteria piscicida, and Oblea rotunda and two naked ciliates Strombidinopsis sp. and Pelagostrobilidium sp. were able to feed on B. adriatica, but the heterotrophic dinoflagellate Polykrikos kofoidii was not. However, B. adriatica supported the positive growth of O. marina, but did not support that of G. dominans and O. rotunda. With increasing prey concentrations, the growth and ingestion rates of O. marina on B. adriatica increased and became saturated. The maximum growth rate of O. marina on B. adriatica was 0.162 d-1. Furthermore, the maximum ingestion rate of O. marina on B. adriatica was 0.2 ng C predator-1 d-1 (2.0 cells predator-1 d-1). In the order Suessiales, the feeding occurrence by common heterotrophic protists on B. adriatica is similar to that on Effrenium voratum and Biecheleria cincta, but different from that on Yihiella yeosuensis. However, the growth and ingestion rates of O. marina on B. adriatica are considerably lower than those on E. voratum and B. cincta, but higher than those on Y. yeosuensis. Therefore, B. adriatica may be less preferred prey for O. marina than E. voratum and B. cincta, but more preferred prey than Y. yeosuensis.