@article{corradino_schnetzer_2022, title={Grazing of a heterotrophic nanoflagellate on prokaryote and eukaryote prey: ingestion rates and gross growth efficiency}, volume={682}, ISSN={["1616-1599"]}, DOI={10.3354/meps13921}, abstractNote={Heterotrophic nanoflagellates (HNANs) play a pivotal role as consumers of picoplankton, remineralizers and carbon vectors, yet knowledge on how prey quantity and quality affect HNAN physiology remains limited. In a series of grazing experiments using an uncharacterized member of the HNAN assemblage, we found that growth (μ) and ingestion rate (IR) varied when offering heterotrophic bacteria (HB), Synechococcus spp. (Syn), Ostreococcus lucimarinus (Ost) or a combination of all 3 prey types. Highest average μ rates (1.8 d-1) were detected on HB at densities of ~106 cells ml-1 and maximum IR on Syn (485 pg C d-1) at ~106 cells ml-1. Independent of prey type, flagellate μ increased with IR up to ~50 pg C d-1. A relatively low P-content in Ost was linked to shifts in C:N:P ratios of the HNAN in the single-prey experiment and when Ost was offered as part of the mixed assemblage. Presented with a mixed diet, the highest contribution to daily C intake came from Ost with 50%, followed by HB with 46% and Syn with only 4%. C-based gross growth efficiencies (GGEs) were higher when feeding on HB and mixed prey, compared to both picophototrophs, while N- and P-based GGEs in mixed prey treatments markedly exceeded those when feeding on any single prey. The findings in this study corroborate the importance of investigating the biogeochemical role of HNANs in relation to prey availability and quality to refine estimates of energy transfer within the microbial loop.}, journal={MARINE ECOLOGY PROGRESS SERIES}, author={Corradino, Gabrielle L. and Schnetzer, Astrid}, year={2022}, month={Jan}, pages={65–77} }
 @article{shields_bianchi_osburn_kinsey_ziervogel_schnetzer_corradino_2019, title={Linking chromophoric organic matter transformation with biomarker indices in a marine phytoplankton growth and degradation experiment}, volume={214}, ISSN={["1872-7581"]}, DOI={10.1016/j.marchem.2019.103665}, abstractNote={The production and transformation of marine chromophoric dissolved organic matter (CDOM) provides a window into the marine biological pump as it is present at all depths and can be measured both in the field and via satellite. However, outside of lignin for terrestrial DOM, few studies have linked marine CDOM characteristics with biomarker indices. In this study, we quantified five fluorescent components of marine CDOM and base-extractable particulate organic matter (BEPOM) in a growth and degradation experiment using a natural plankton assemblage, and compared those results to bacterial abundances, hydrolytic enzyme activities, and amino acid concentrations and associated diagenetic indices. Rotating glass bottles containing plankton were sampled initially (day 0), during the mid-exponential (day 13) and stationary (day 20) growth phases, and again following a dark degradation period that lasted 42 days. Protein-like fluorescence (tryptophan-like and tyrosine-like) was correlated with the total amino acid concentrations for both the DOM and BEPOM through all phases of the incubation. However, tryptophan-like fluorescence showed a stronger correlation for aromatic amino acids. The concentration of particulate organic carbon changed significantly during each phase of the experiment and this substrate correlated with hydrolytic enzyme activities and bacterial abundance. This heterotrophy diagenetically altered the POM during the stationary phase and ultimately resulted in the increased production of more humic-like CDOM after degradation in the dark. Results from this study indicate that CDOM formation and cycling may play a prominent role in the ocean's nitrogen cycle.}, journal={MARINE CHEMISTRY}, author={Shields, Michael R. and Bianchi, Thomas S. and Osburn, Christopher L. and Kinsey, Joanna D. and Ziervogel, Kai and Schnetzer, Astrid and Corradino, Gabrielle}, year={2019}, month={Aug} }