Strombidium cf. basimorphum growth, ingestion, and photosynthetic responses to different irradiance and prey concentration
This data was generated as part of a study in which inorganic carbon uptake, growth, and ingestion rates were measured for S. cf. basimorphum under three different irradiances (10, 40, and 120 μmol photons m–2 s–1) when acclimated to three different prey densities (5000, 10000, and 40000 cells mL-1), and when allowed to deplete the prey. After prey depletion, cultures survived without prey longest (~6 days) at the medium test irradiance (40 μmol photons m–2 s–1), while inorganic carbon uptake rates and cellular chl-a content declined fastest at the highest test irradiance. This indicates that the ciliates may be unable to maintain the chloroplasts functionally without replacement at high irradiances. Ingestion rates were not shown to be significantly influenced by irradiance. The maximum gross growth efficiency (GGE) in this study (1.1) was measured in cultures exposed to the medium test irradiance and lowest prey density treatment (5×10^3 cells mL-1). The relative contribution of inorganic carbon uptake to the ciliate carbon budget was also highest in this treatment (42%). A secondary GGE peak (0.99) occurred when cultures were exposed to the highest test irradiance and the medium prey density. These and other results suggest that S. cf. basimorphum and other generalist non-constitutive mixotrophs can flexibly exploit many different environmental conditions across the globe. Units can be found in the first mention of each parameter for every sheet. V2: Corrected a mistake in the notes: the variable Lchla was measured in [µg chl-a/ L] not [pg chl-a/L]. Added missing biovolume information. V3: Combined datasheets into a single more easily accessible file, elaborated on variable and data explanations in the notes, and ensured consistency in column naming across both experiments; description and methods changed to reflect the corresponding article's updated text.
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Both experiments utilized three light levels: 10, 40, and 120 μmol photons m–2 s–1 Starvation Data: Experiments were terminated after 13 days, or after the ciliate density was < 5 cells mL-1. For a minimum of five days before the initiation of experiments for each light condition, 800 mL of S. cf. basimorphum mixed culture (contained in a 1L glass culture flask) were acclimatized to the experimental irradiance and fed light-acclimatized T. amphioxeia cells at prey concentrations that were replenished daily to 4×10^4 cells mL-1. When the ciliate density reached approximately 175 cells mL-1, the experiment was initiated (day 0) by splitting the acclimated culture into three 200 mL triplicates that were contained in 500 mL glass culture flasks. Then, T. amphioxeia cells were added to the experimental cultures so that the algal density of the culture reached a saturating prey density of ~3-3.5×10^4 cells mL-1. Subsamples (5 to 10 mL) were collected, at minimum, on days 2, 5, 7, and 9, as well as every 2 days thereafter until the termination of each experiment. These subsamples were used to measure the densities (individuals mL-1), growth rates (cell divisions d-1), photosynthetic rates (pg C cell-1 h-1), and chlorophyll content (pg chl-a cell-1) of both ciliates and algae, as well as to measure the ciliates’ cell volumes (µm3). Monocultures of T. amphioxeia were run in parallel with the mixed cultures until there were no measurable prey densities within ciliate cultures. Algal density and growth were measured in the monocultures before they were diluted with fresh f/20 media on each sampling day to match the algal densities found in the experimental cultures. The monocultures were also sampled for photosynthetic rate and chlorophyll content on the same days as the experimental cultures. Acc_comp: Cultures were acclimatized to each light condition for a minimum of 5 days prior to the initiation of all experiments. The duration of the experiment was 5 days, with days 1 and 2 serving to acclimatize cultures to the experimental prey densities. Monocultures of T. amphioxeia were run as controls alongside mixed cultures. The experiments were carried out at the same light levels as for the starvation experiment. S. cf. basimorphum density was maintained at 15 individuals mL-1. Ciliate and prey density were adjusted every day by dilution with fresh media and addition of algae from monocultures. During days 1-2, 800 mL of both the mixed cultures and control monocultures were kept in 1 L glass culture flasks. At the end of day 2, the acclimatized cultures were split into triplicates by placing 200 mL of each culture into 500 mL glass culture flasks. Subsamples (5-10 mL) were taken daily at a fixed time for all 5 days of the experiment to discern algal and ciliate densities. On days 3-5 of the experiment, additional subsamples were taken to measure cell volume, photosynthetic rate, and chlorophyll content.