Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

This dataset presents growth rates for Emiliania huxleyi thermal response curve across 12 temperatures from 8.5-28.6C. Global warming will be combined with predicted increases in thermal variability in the future surface ocean, but how temperature dynamics will affect phytoplankton biology and biogeochemistry is largely unknown. Here, we examine the responses of the globally important marine coccolithophore Emiliania huxleyi to thermal variations at two frequencies (1 d and 2 d) at low (18.5 °C) and high (25.5 °C) mean temperatures. Elevated temperature and thermal variation decreased growth, calcification and physiological rates, both individually and interactively. The 1 d thermal variation frequencies were less inhibitory than 2 d variations under high temperatures, indicating that high-frequency thermal fluctuations may reduce heat-induced mortality and mitigate some impacts of extreme high-temperature events. Cellular elemental composition and calcification was significantly affected by both thermal variation treatments relative to each other and to the constant temperature controls. The negative effects of thermal variation on E. huxleyi growth rate and physiology are especially pronounced at high temperatures. These responses of the key marine calcifier E. huxleyi to warmer, more variable temperature regimes have potentially large implications for ocean productivity and marine biogeochemical cycles under a future changing climate.

These data and methods are published in Wang, X., Fu, F., Qu, P., Kling, J. D., Jiang, H., Gao, Y., & Hutchins, D. A. (2019). How will the key marine calcifier Emiliania huxleyi respond to a warmer and more thermally variable ocean?. Biogeosciences, 16(22), 4393-4409. doi:10.5194/bg-2019-179.

Specific growth rates were calculated using change in fluorescence over time (verified using cell count data) and the equation μ=ln[N(T2)/N(T1)]/(T2-T1). N(T1) and N(T2) are the in vivo fluorescence values. Chlorophyll a, total particulate carbon (TPC), particulate organic carbon (POC),  particulate organic nitrogen (PON), and particulate organic carbon (POP) were filtered onto GF/F filters and analyzed following the methodology used in Fu et al., 2007. Particulate inorganic carbon was defined as the difference between TPC and POC after POC filters had been subjected to concentrated HCl fumes for 24 hours to remove all inorganic carbon. Calcification, photosynthesis, and carbon fixation rates were all measured following the procedures outlined in Feng et al., 2008.

All data was processed using either R (v 3.4.4) or Microsoft Excel 2016. 

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- unmerged Excel cells for Temperature and repeated value from preceding rows.
- removed 'C' from Temperature values
- changed param name 'growth rate (d-1)' to 'Growth_Rate'
- reduced Growth_Rate precision from 14 to 4 decimal places

NSF Award Abstract:
Microscopic plants called phytoplankton are key members of global oceanic ecosystems, since their photosynthesis supports the majority of the marine food chain and produces about as much oxygen as land plants. Because of this, oceanographers have often carried out experiments examining how factors such as temperature and carbon dioxide levels may affect phytoplankton growth. Most previous experiments have used constant levels of temperature and carbon dioxide, but it is clear from looking at measurements from real ocean ecosystems that these two factors often vary greatly over timescales of days to weeks. Using field and laboratory experiments along with computer modeling, this project will test how the growth of several major groups of phytoplankton differs under constant conditions of temperature and carbon dioxide, compared to conditions in which these factors fluctuate in intensity and frequency. This research will give marine scientists a better picture of how phytoplankton may respond to a varying natural environment today and in the future, and therefore help us to understand how ocean food webs function to support critical living resources such as fisheries. The project will train graduate and undergraduate students and a postdoctoral researcher, and the lead scientists will be involved in an ocean science education program for largely minority high school students from a downtown Los Angeles school district.

The goal of this project is to use laboratory culture and natural community experiments to understand how realistically fluctuating temperature and pCO2 conditions may affect globally important phytoplankton groups in ways that differ from the artificial constant exposures used in previous work. Culture experiments will test how the intensity and frequency of short-term thermal and carbonate fluctuations affects the growth responses of diazotrophic and picoplanktonic cyanobacteria, coccolithophores, and diatoms under both current and projected future environmental conditions. These lab results will be supported and extended by parallel experiments using mixed natural assemblages from the California upwelling regime, allowing us to test these same questions using phytoplankton communities that experience large seasonal shifts between highly dynamic thermal and carbonate system conditions during the spring upwelling season, and relatively much more static conditions during fall stratification events. These results will be synthesized using a new generation of numerical models that employ novel approaches to incorporating realistic environmental variations to allow more accurate predictions of phytoplankton responses to a dynamic environment in today's marine ecosystems, and in the future changing ocean.