Physiology of the mixotrophic dinoflagellate Fragilidium subglobosum. I. Effects of phagotrophy and irradiance on photosynthesis and carbon content

Abstract

Photosynthesis was measured for the mixotrophic dinoflagellate Fragilidium subglobosum grown with and without prey (Ceratium lineatum), at 5 different irradiances. Photosynthetic rates were measured in phototrophically and mixotrophically grown cultures by use of the single-cell 14 C uptake technique. Photosynthetic rates were reduced by 48 to 69% and cellular chlorophyll a (chl a) content was reduced by 13 to 67% in food-replete mixotrophic cultures as compared with strictly phototrophic cultures grown at the same irradiances. Under the same conditions, chl anormalized photosynthetic rates were thus 7 to 49% lower in mixotrophic cultures than in strictly phototrophic cultures. It is, therefore, suggested that either the photosynthetic apparatus becomes less efficient when the cells are phagotrophically active or the chl a-normalized photosynthesis is reduced because fed cells contain photosynthetically inactive chl a in their food vacuoles. When food is abundant, the greater part of the gross carbon uptake of F. subglobosum is acquired through phagotrophy even at irradiances saturating for photosynthesis.

Intraspecific variability in Karlodinium veneficum: Growth rates, mixotrophy, and lipid composition

“…However, when nutrients are provided in excess, low light levels (or darkness) should trigger an enhanced feeding response in either mixotrophy mode, as previously observed for dinoflagellates (Bird and Kalff, 1989;Jones et al, 1993;Skovgaard, 1996;Legrand et al, 1998). In our experiments, and similar to those of Skovgaard et al (2000) with Fragilidium subglobosum, no significant differences in ingestion rates after 2 days of light deprivation were noted, although the growth rates of the dinoflagellates were certainly adversely affected. By contrast, Li et al (1999) observed a negative effect of low light intensities on K. veneficum feeding activity.…”

High resilience of two coastal plankton communities to twenty-first century seawater acidification: Evidence from microcosm studies

“…Photosynthetic activity was determined four times using a slightly modified version of Skovgaard et al (2000). Twenty microlitres of an NaH 14 CO 3 stock solution (specific activity 0100 mCi ml (1 , Carbon 14 centralen, Denmark) were added to a 3 ml sample in a glass scintillation vial.…”

Phased cell division and facultative mixotrophy of the marine dinoflagellate Fragilidium duplocampanaeforme and its trophic interactions with the dinoflagellates Dinophysis spp. and a ciliate Mesodinium rubrum

“…Fragilidium fissile, Fragilidium heterolobum, Fragilidium lacustre, Fragilidium mexicanum, and Fragilidium subglobosum (Lindemann, 1924;Balech, 1959Balech, , 1988Balech, , 1990Von Stosch, 1969) until Né zan and Chomé rat (2009) recently added a new species, Fragilidium duplocampanaeforme, to the genus. Among the six species, only one species, F. subglobosum, has been relatively intensively studied for its mixotrophy (herein defined as a combination of phototrophy and phagotrophy) by a few Danish and Korean research groups over several years (Skovgaard, 1996a,b;Hansen and Nielsen, 1997;Jeong et al, 1997Jeong et al, , 1999Hansen et al, 2000;Skovgaard et al, 2000). By comparison, other Fragilidium species have been received relatively less attention although they have also been observed or thought to be mixotrophs (Balech and Ferrando, 1964;Eppley and Harrison, 1975;Balech, 1988Balech, , 1990Jeong et al, 1997Jeong et al, , 1999.…”