Lowenstein
Daniel P.
Lowenstein
Daniel P.
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ArticleWhole community metatranscriptomes and lipidomes reveal diverse responses among antarctic phytoplankton to changing ice conditions(Frontiers Media, 2021-02-18) Bowman, Jeff S. ; Van Mooy, Benjamin A. S. ; Lowenstein, Daniel P. ; Fredricks, Helen F. ; Hansel, Colleen M. ; Gast, Rebecca J. ; Collins, James R. ; Couto, Nicole ; Ducklow, Hugh W.The transition from winter to spring represents a major shift in the basal energy source for the Antarctic marine ecosystem from lipids and other sources of stored energy to sunlight. Because sea ice imposes a strong control on the transmission of sunlight into the water column during the polar spring, we hypothesized that the timing of the sea ice retreat influences the timing of the transition from stored energy to photosynthesis. To test the influence of sea ice on water column microbial energy utilization we took advantage of unique sea ice conditions in Arthur Harbor, an embayment near Palmer Station on the western Antarctic Peninsula, during the 2015 spring–summer seasonal transition. Over a 5-week period we sampled water from below land-fast sea ice, in the marginal ice zone at nearby Palmer Station B, and conducted an ice removal experiment with incubations of water collected below the land-fast ice. Whole-community metatranscriptomes were paired with lipidomics to better understand how lipid production and utilization was influenced by light conditions. We identified several different phytoplankton taxa that responded similarly to light by the number of genes up-regulated, and in the transcriptional complexity of this response. We applied a principal components analysis to these data to reduce their dimensionality, revealing that each of these taxa exhibited a strikingly different pattern of gene up-regulation. By correlating the changes in lipid concentration to the first principal component of log fold-change for each taxa we could make predictions about which taxa were associated with different changes in the community lipidome. We found that genes coding for the catabolism of triacylglycerol storage lipids were expressed early on in phytoplankton associated with a Fragilariopsis kerguelensis reference transcriptome. Phytoplankton associated with a Corethron pennatum reference transcriptome occupied an adjacent niche, responding favorably to higher light conditions than F. kerguelensis. Other diatom and dinoflagellate taxa had distinct transcriptional profiles and correlations to lipids, suggesting diverse ecological strategies during the polar winter–spring transition.
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ArticleTargeted and untargeted lipidomic analysis of haptophyte cultures reveals novel and divergent nutrient-stress adaptations(Elsevier, 2021-11-11) Lowenstein, Daniel P. ; Mayers, Kyle M. J. ; Fredricks, Helen F. ; Van Mooy, Benjamin A. S.Lipids comprise a significant, highly plastic proportion of the biomass in haptophytes, a ubiquitous, globally significant, and genetically diverse clade of photosynthetic microalgae. Recent studies have investigated the cellular lipidomes of disparate, individual species of haptophytes under nutrient-replete and nutrient-limited conditions, but have not investigated how lipidomes vary across the larger evolutionary clade or its ecological functional groups. We cultured eight species of haptophytes, including five strains of Emiliania huxleyi, for analysis via high performance liquid chromatography–high resolution accurate mass–mass spectrometry (HPLC–HRAM–MS), and performed untargeted computational and hierarchical cluster analyses on their lipidomes. We identified similarities and differences in lipidomes along both evolutionary and ecological lines, and identified potential biomarkers for haptophyte sub-clades, including 38 glycosphingolipids, seven betaine-like lipids, and three phosphatidyl-S,S-dimethylpropanethiol (PDPT) sulfo-phospholipids. We also provide the first evidence for the glycolipid, glucuronosyldiacylglycerol, in eukaryotic microalgae. We conducted a more targeted study of four haptophyte species under nitrogen- and phosphorus-limited conditions to investigate their lipidomic responses to nutrient stress. Under N- and P-limitation, the species exhibited disparate lipidomic responses. Uniquely, in response to N-limitation, E. huxleyi CCMP 374 heavily upregulated PDPT from 3.6 ± 0.9% to 10.4 ± 1.5% of quantified polar lipids. These previously uncharacterized lipidomes and responses to nutrient limitation reflect divergent evolutionary strategies and challenge popular phenotypic extrapolations between species.
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ArticleSeasonal mixed layer depth shapes phytoplankton physiology, viral production, and accumulation in the North Atlantic(Nature Research, 2021-11-17) Diaz, Ben P. ; Knowles, Benjamin ; Johns, Christopher T. ; Laber, Christien P. ; Bondoc, Karen Grace V. ; Haramaty, Liti ; Natale, Frank ; Harvey, Elizabeth L. ; Kramer, Sasha J. ; Bolaños, Luis M. ; Lowenstein, Daniel P. ; Fredricks, Helen F. ; Graff, Jason R. ; Westberry, Toby K. ; Mojica, Kristina D. A. ; Haëntjens, Nils ; Baetge, Nicholas ; Gaube, Peter ; Boss, Emmanuel S. ; Carlson, Craig A. ; Behrenfeld, Michael J. ; Van Mooy, Benjamin A. S. ; Bidle, Kay D.Seasonal shifts in phytoplankton accumulation and loss largely follow changes in mixed layer depth, but the impact of mixed layer depth on cell physiology remains unexplored. Here, we investigate the physiological state of phytoplankton populations associated with distinct bloom phases and mixing regimes in the North Atlantic. Stratification and deep mixing alter community physiology and viral production, effectively shaping accumulation rates. Communities in relatively deep, early-spring mixed layers are characterized by low levels of stress and high accumulation rates, while those in the recently shallowed mixed layers in late-spring have high levels of oxidative stress. Prolonged stratification into early autumn manifests in negative accumulation rates, along with pronounced signatures of compromised membranes, death-related protease activity, virus production, nutrient drawdown, and lipid markers indicative of nutrient stress. Positive accumulation renews during mixed layer deepening with transition into winter, concomitant with enhanced nutrient supply and lessened viral pressure.
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ArticleRotoBOD─quantifying oxygen consumption by suspended particles and organisms(American Chemical Society, 2024-05-08) Karthauser, Clarissa ; Fucile, Paul D. ; Maas, Amy E. ; Blanco-Bercial, Leocadio ; Gossner, Hannah ; Lowenstein, Daniel P. ; Niimi, Yuuki J. ; Van Mooy, Benjamin A. S. ; Bernhard, Joan M. ; Buesseler, Kenneth O. ; Sievert, Stefan M.Sinking or floating is the natural state of planktonic organisms and particles in the ocean. Simulating these conditions is critical when making measurements, such as respirometry, because they allow the natural exchange of substrates and products between sinking particles and water flowing around them and prevent organisms that are accustomed to motion from changing their metabolism. We developed a rotating incubator, the RotoBOD (named after its capability to rotate and determine biological oxygen demand, BOD), that uniquely enables automated oxygen measurements in small volumes while keeping the samples in their natural state of suspension. This allows highly sensitive rate measurements of oxygen utilization and subsequent characterization of single particles or small planktonic organisms, such as copepods, jellyfish, or protists. As this approach is nondestructive, it can be combined with several further measurements during and after the incubation, such as stable isotope additions and molecular analyses. This makes the instrument useful for ecologists, biogeochemists, and potentially other user groups such as aquaculture facilities. Here, we present the technical background of our newly developed apparatus and provide examples of how it can be utilized to determine oxygen production and consumption in small organisms and particles.