About

Dr. Daniel C. O. Thornton is a biologist specializing in the role of microorganisms in shaping Earth's complex systems. His research spans the interface between ocean and atmosphere, focusing on how marine microorganisms contribute to the production of aerosols that influence atmospheric processes, including cloud formation and climate regulation. He aims to develop mechanistic models linking phytoplankton ecophysiology to aerosol properties and their capacity to act as cloud condensation nuclei and ice nuclei particles, with particular attention to marine biogenic aerosols as ice nucleating particles. Additionally, Dr. Thornton investigates the physiology and ecology of phytoplankton, especially diatoms, exploring how nutrient availability affects their growth, resource allocation, exopolymer production, and cell death. His work emphasizes understanding the biological and biogeochemical functions of phytoplankton, which are responsible for a significant portion of Earth's photosynthetic carbon fixation, and their role in marine ecosystems and climate processes.

Research topics

• Geology
• Oceanography
• Environmental science
• Environmental chemistry
• Meteorology
• Chemistry
• Atmospheric sciences
• Ecology
• Biology
• Geography

Selected publications

• Photophysiology data from smooth cordgrass (Sporobolus alterniflorus) measured in a North American saltmarsh using pulse amplitude modulated (PAM) fluorescence

  Data in Brief · 2025-03-15

  articleOpen access1st authorCorresponding

  Coastal saltmarshes play an important role as an interface between terrestrial and marine environments. Sporobolus alterniflorus (smooth cordgrass) occurs naturally along the east coast of North America, from Texas to Quebec, where it often forms extensive monospecific stands. Sporobolus alterniflorus is highly productive and is often the dominant plant in terms of biomass. This data set presents variable chlorophyll fluorescence measurements made in situ from the leaves of Sporobolus alterniflorus growing in a tidal saltmarsh ecosystem (North Inlet, South Carolina, United states). Measurements were made using pulse amplitude modulated (PAM) fluorescence. The data include raw measurements of variable fluorescence ( F t ) and maximum fluorescence ( F’ m ) made at 12 different actinic photosynthetic photon flux densities (PPFD). These data were used to calculate the quantum yield of photosystem II (Φ PSII ) and estimate electron transport rates (ETRs). Rapid light curves (RLCs) were fitted to the ETRs to parametrize the relationship between ETR and PPFD in S. alterniflorus under different environmental conditions. Measurements were made from S. alterniflorus culms growing at different positions on the shore and at different times of the day. These data provide a resource for researchers interested in the photophysiology and photosynthesis of Sporobolus alterniflorus , and saltmarsh ecology and management.

  PublisherDOI

• Biogeochemistry of phytoplankton RuBisCO in the ocean

  Frontiers in Marine Science · 2025-09-25

  articleOpen access1st authorCorresponding

  Form I Ribulose-1,5-bisphosphate oxygenase/carboxylase (RuBisCO) is the most abundant enzyme on Earth, playing a key role in carbon fixation during oxygenic photosynthesis. Using published sequence data, I show that there are significant differences in the amount of elemental resources (C, N and S) and energy required to synthesize the different Types of Form I RuBisCO. The shorter amino acid lengths of cyanobacterial RuBisCO had lower resource requirements to build the holoenzyme compared with eukaryotes. Consequently, the rise to dominance of eukaryote phytoplankton during the Neoproterozoic (1000–541 Ma) led to a shift to more expensive eukaryote RuBisCO. There are also significant differences in the elemental composition of RuBisCO between eukaryotes in different supergroups. Estimates of resource allocation were used to estimate how much C, N and S is associated with RuBisCO in the modern ocean. The marine cyanobacterium Prochlorococcus is the most numerically abundant photosynthetic organism on Earth and accounts for 7.3 – 8.9% of net ocean primary productivity. There are 2.11- 2.69 x 10 6 mol RuBisCO in Prochlorococcus , which amounts to 4 to 5% of the total RuBisCO pool in the ocean. The relatively low RuBisCO content compared with productivity indicates highly efficient photosynthesis in Prochlorococcus. The total marine RuBisCO reservoir is equivalent to 0.016 Pg C, 5.1 Tg N, and 0.4 Tg S. The estimated annual productivity of RuBisCO is equivalent to 0.725 - 0.890 Pg C yr -1 , 228–283 Tg N yr -1 , and 16.5 - 22.5 Tg S yr -1 . In the context of the marine nitrogen cycle, the amount of nitrogen fluxing through the pool of RuBisCO each year is equivalent to, or even higher, than the rate of biological nitrogen fixation (223 ± 30 Tg N yr −1 ). Turnover of RuBisCO is rapid, occurring every 6.6 to 8.2 days. In conclusion, RuBisCO is not only significant as the primary carbon fixation enzyme in the ocean, but also as a pool of chemical elements, particularly nitrogen.

  PublisherOA PDFDOI

• Effect of viral infection on the ice nucleation efficiency of marine coccolithophores

  Aerosol Science and Technology · 2024-11-22 · 3 citations

  articleOpen accessCorresponding

  A marine coccolithophore (Emiliania huxleyi) and coccolithovirus (EhV-207) were grown together in a marine aerosol reference tank (MART) to investigate how the viral lysis of phytoplankton affects the formation of immersion mode ice nucleating particles (INPs) in sea spray aerosol (SSA). The mean ice nucleation temperatures of SSA produced during viral infection were slightly lower (–28.5 °C) than pre-viral infection (–27.5 °C). Ice nucleation temperatures were relatively low, indicating that organic matter from E. huxleyi is less effective as an INP than phytoplankton examined in previous studies. E. huxleyi is covered in calcium carbonate coccoliths and contains high intracellular concentrations of dimethylsulfoniopropionate (DMSP). The ice nucleation efficiencies of purified components were measured to better understand this model system. Purified coccoliths were moderately effective INPs (–25.3 ± 0.4 °C at 5 x 10² mg L^-1 (mean ±pooled SD)) that showed a concentration effect, with lower freezing temperatures at lower concentrations. Coccoliths and DMSP were both weakly efficient INPs. In comparison, purified phytoplankton viruses (EhV-207 and CtenRNAV-01) infecting coccolithophores and diatoms, respectively, did not affect freezing at temperatures warmer than the procedural blank. Our results suggest that E. huxleyi, in contrast to diatoms and cyanobacteria, is not a significant source of immersion mode INPs to the marine atmosphere, despite its broad distribution in the global ocean and large-scale bloom formation.

  PublisherOA PDFDOI

• Effect of Aggregation and Molecular Size on the Ice Nucleation Efficiency of Proteins

  Environmental Science & Technology · 2024-02-26 · 12 citations

  articleOpen accessCorresponding

  Aerosol acts as ice-nucleating particles (INPs) by catalyzing the formation of ice crystals in clouds at temperatures above the homogeneous nucleation threshold (−38 °C). In this study, we show that the immersion mode ice nucleation efficiency of the environmentally relevant protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), occurs at temperatures between −6.8 and −31.6 °C. Further, we suggest that this range is controlled by the RuBisCO concentration and protein aggregation. The warmest median nucleation temperature (−7.9 ± 0.8 °C) was associated with the highest concentration of RuBisCO (2 × 10–1 mg mL–1) and large aggregates with a hydrodynamic diameter of ∼103 nm. We investigated four additional chemically and structurally diverse proteins, plus the tripeptide glutathione, and found that each of them was a less effective INP than RuBisCO. Ice nucleation efficiency of the proteins was independent of the size (molecular weight) for the five proteins investigated in this study. In contrast to previous work, increasing the concentration and degree of aggregation did not universally increase ice nucleation efficiency. RuBisCO was the exception to this generalization, although the underlying molecular mechanism determining why aggregated RuBisCO is such an effective INP remains elusive.

  PublisherOA PDFDOI

• Supplementary material to "Production of aerosol containing ice nucleating particles (INPs) by fast growing phytoplankton"

  2023-02-15

  preprint1st authorCorresponding
  PublisherDOI

• Ice nucleation catalyzed by the photosynthesis enzyme RuBisCO and other abundant biomolecules

  Communications Earth & Environment · 2023-02-25 · 27 citations

  articleOpen access

  Abstract Atmospheric aerosol and the cloud droplets and ice crystals that grow on them remain major sources of uncertainty in global climate models. A subset of aerosol, ice nucleating particles, catalyze the freezing of water droplets at temperatures warmer than −38 °C. Here we show that RuBisCO, one of the most abundant proteins in plants and phytoplankton, is one of the most efficient known immersion ice nucleating particles with a mean freezing temperature of −7.9 ± 0.3 °C. Further, we demonstrate RuBisCO is present in ambient continental aerosol where it can serve as an ice nucleating particle. Other biogenic molecules act as immersion ice nucleating particles, in the range of −19 to −26 °C. In addition, our results indicate heat denaturation is not a universal indicator of the proteinaceous origin of ice nucleating particles, suggesting current studies may fail to accurately quantify biological ice nucleating particle concentrations and their global importance.

  PublisherOA PDFDOI

• Reply on RC1

  2023-06-05

  peer-reviewOpen access1st authorCorresponding

  <strong class="journal-contentHeaderColor">Abstract.</strong> Sea spray aerosol contains ice nucleating particles (INPs), which affect the formation and properties of clouds. Here, we show that aerosols emitted from fast growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (&minus;38.0 ^∘C) of pure water. Aerosol sampled over phytoplankton cultures grown in a marine aerosol reference tank (MART) induced nucleation and freezing at temperatures as high as &minus;15.0 ^∘C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phytoplankton: a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (&minus;28.5 ^∘C and below) when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II (<em>&Phi;</em>_PSII), an indicator of the physiological status of phytoplankton. High values of &Phi;_PSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. In the North Atlantic Ocean, high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 days at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 day^-1) were greatest over the 24 hours preceding the warmest mean ice nucleation temperature (&minus;25.5 ^∘C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs, and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

  PublisherDOI

• Production of aerosol containing ice nucleating particles (INPs) by fast growing phytoplankton

  2023-02-15 · 1 citations

  preprintOpen access1st authorCorresponding

  Abstract. Sea spray aerosol contains ice nucleating particles (INPs), which affect the formation and properties of clouds. Here, we show that aerosols emitted from fast growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (−38.0 ∘C) of pure water. Aerosol sampled over phytoplankton cultures grown in a marine aerosol reference tank (MART) induced nucleation and freezing at temperatures as high as −15.0 ∘C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phytoplankton: a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (−28.5 ∘C and below) when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II (ΦPSII), an indicator of the physiological status of phytoplankton. High values of ΦPSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. In the North Atlantic Ocean, high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 days at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 day-1) were greatest over the 24 hours preceding the warmest mean ice nucleation temperature (−25.5 ∘C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs, and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

  PublisherDOI

• Production of ice-nucleating particles (INPs) by fast-growing phytoplankton

  Atmospheric chemistry and physics · 2023-10-11 · 13 citations

  articleOpen access1st authorCorresponding

  Abstract. Sea spray aerosol contains ice-nucleating particles (INPs), which affect the formation and properties of clouds. Here, we show that aerosols emitted from fast-growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (−38.0 ∘C) of pure water. Aerosol sampled over phytoplankton cultures grown in a Marine Aerosol Reference Tank (MART) induced nucleation and freezing at temperatures as high as −15.0 ∘C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phytoplankton, namely a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (−28.5 ∘C and below), which were not different from the freezing temperatures of procedural blanks, when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II (ΦPSII), an indicator of the physiological status of phytoplankton. High values of ΦPSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. For comparison, field measurements in the North Atlantic Ocean showed that high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 d at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 d−1) were greatest over the 24 h preceding the warmest mean ice nucleation temperature (−25.5 ∘C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

  PublisherOA PDFDOI

• Reply on RC2

  2023-06-05

  peer-reviewOpen access1st authorCorresponding

  <strong class="journal-contentHeaderColor">Abstract.</strong> Sea spray aerosol contains ice nucleating particles (INPs), which affect the formation and properties of clouds. Here, we show that aerosols emitted from fast growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (&minus;38.0 ^∘C) of pure water. Aerosol sampled over phytoplankton cultures grown in a marine aerosol reference tank (MART) induced nucleation and freezing at temperatures as high as &minus;15.0 ^∘C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phytoplankton: a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (&minus;28.5 ^∘C and below) when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II (<em>&Phi;</em>_PSII), an indicator of the physiological status of phytoplankton. High values of &Phi;_PSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. In the North Atlantic Ocean, high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 days at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 day^-1) were greatest over the 24 hours preceding the warmest mean ice nucleation temperature (&minus;25.5 ^∘C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs, and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

  PublisherOA PDFDOI

Recent grants

• Identification of Ice Nucleation Sources from Marine Phytoplankton

  NSF · $925k · 2021–2026

• Effect of Temperature on Extracellular Polymeric Substance Production (EPS) by Diatoms

  NSF · $365k · 2007–2012

Frequent coauthors

• Sarah D. Brooks

  Texas A&M University

  19 shared

• Alyssa N. Alsante

  Texas A&M University

  10 shared

• Graham J. C. Underwood

  University of Essex

  8 shared

• Thomas S. Bianchi

  University of Florida

  7 shared

• Elise K. Wilbourn

  Sandia National Laboratories California

  7 shared

• Jessica Mirrielees

  Texas A&M University

  7 shared

• DB Nedwell

  University of Essex

  6 shared

• Jie Chen

  Changsha University of Science and Technology

  6 shared

Labs

• Thornton LabPI