Strombidium cf. basimorphum growth, ingestion, and photosynthetic responses to different irradiance and prey concentration

Published: 15-12-2020| Version 1 | DOI: 10.17632/wmm2wkcwwz.1
Contributor:
Erin Hughes

Description

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 (Acc_Com.xlsx) to three different prey densities (5000, 10000, and 40000 cells mL-1), and when allowed to deplete the prey (Starv_comp.xlsx). 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 significantly lower at the highest tested irradiance only when cultures were acclimated to the highest tested prey density. 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 (5×103 cells mL-1). The relative contribution of inorganic carbon uptake to the ciliate carbon budget was also highest in this treatment (81%). 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.

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Starv_comp: Experiments were terminated after 13 days, or after the ciliate density was < 5 cells mL-1. S. cf. basimorphum cultures were fed T. amphioxeia as prey; both organisms were acclimatized to each light condition for a minimum of 5 days prior to the initiation of all experiments. When the ciliate density reached ~ 175 cells mL-1, the experiment was initiated (day 0) by adding T. amphioxeia cells to the experimental cultures so that the algal density of the culture reached a saturating prey density of ~3-3.5×104 cells mL-1. The experiment was run in triplicate, with 200 mL of each culture contained within 500 mL glass culture flasks. Subsamples 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 cell densities, growth rates, photosynthetic rates, and chlorophyll content of both ciliates and algae, as well as to measure the ciliates’ cell volumes. Monocultures of Teleaulax 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. 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 triplicate 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 in order to measure cell volume, photosynthetic rate, and chlorophyll content as described previously.