Photosynthetic efficiency and nutrient physiology of the diatom Thalassiosira pseudonana at three growth temperatures
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ORIGINAL PAPER
Photosynthetic efficiency and nutrient physiology of the diatom Thalassiosira pseudonana at three growth temperatures Samantha J. Gleich1,2 · Louis V. Plough1 · Patricia M. Glibert1 Received: 6 February 2020 / Accepted: 9 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Diatom cells utilize a variety of metabolic pathways to cope with internal energy imbalances caused by stressful environmental conditions. In this study, the model diatom species, Thalassiosira pseudonana, was grown in nutrient replete and nitrate (NO3−)- and dissolved silicate (Si)-depleted media at three growth temperatures (4, 17, 28 °C) to determine how nutrient enrichment and temperature affects diatom growth, photosynthetic efficiency, nitrate reductase (NR) enzyme activity, biogenic silica (bSiO2) deposition, and NR gene expression. Growth rates for nutrient-replete cultures were highest at 17 °C. Across all nutrient treatments, the cells grown at 17 °C had an average Fv/Fm of 0.44 ± 0.006, while the cells were grown at 4 °C and 28 °C had an average Fv/Fm of 0.37 ± 0.004 and 0.38 ± 0.01, respectively. Activity of NR was variable across treatments with no significant effect of temperature. The relative expression of the targeted NR gene was, on average, ~ 10 times higher in the 4 °C cultures and ~ 4 times higher in the 28 °C than in the 17 °C cultures, while the activity of the NR enzyme was generally highest in the cultures grown at 17 °C that were enriched with NO3−. Cells grown under nutrient-replete conditions had significantly higher bSiO2 deposition rates at 4 °C than cells grown at 17 and 28 °C. These data support the notion that cold, nutrient-replete conditions lead to increases in diatom silicification and that NR activity may be regulated downstream of mRNA transcription under specific environmental conditions.
Introduction Diatoms make substantial contributions to new production in marine and freshwater ecosystems and have been estimated to fix over 10 billion tons of inorganic carbon (C) in the oceans each year (Goldman 1993; Del Amo et al. 1997; Brzezinski et al. 1998; Smetacek 1998; Granum et al. 2005). In addition to the significant role that diatoms play in global primary production, these organisms are also important in the export of C from the euphotic zone and in the biogeochemical cycling of nutrients in aquatic ecosystems (Round Responsible Editor: S. Shumway. Reviewed by undisclosed experts. * Patricia M. Glibert [email protected] 1
Horn Point Laboratory, University of Maryland Center for Environmental Science, P.O. Box 775, Cambridge, MD 21613, USA
Present Address: Department of Biological Sciences, University of Southern California, 3616 Trousdale Parkway, AHF 301, Los Angeles, CA 90089‑0371, USA
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et al. 1990; Raven and Falkowski 1999; Ragueneau et al. 2006). Although diatoms are widely distributed and appear to be “cosmopolitan” in nature (Finlay and Fenchel 2004), they do have environmental preferences and changes in the surrounding environment can stre
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