Chang Jae Choi

Chang Jae Choi
University of Texas at Austin | UT · Marine Science Institute

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20
Publications
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1,995
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Publications

Publications (20)
Preprint
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Ecological interactions among phytoplankton occur in a moving fluid environment. Oceanic flows can modulate the competition and coexistence between phytoplankton populations, which in turn can affect ecosystem function and biogeochemical cycling. We explore the impact of submesoscale velocity gradients on phytoplankton ecology using observations, s...
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The marine picoeukaryote Bathycoccus prasinos has been considered a cosmopolitan alga, although recent studies indicate two ecotypes exist, Clade BI ( B. prasinos ) and Clade BII. Viruses that infect Bathycoccus Clade BI are known (BpVs), but not that infect BII. We isolated three dsDNA prasinoviruses from the Sargasso Sea against Clade BII isolate...
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Coral reefs are possible ‘sinks’ for microbes, however the removal mechanisms at play are not well understood. Here, we characterize pelagic microbial groups at CARMABI reef (Curaçao) and examine microbial consumption by three coral species: Madracis mirabilis, Porites astreoides, and Stephanocoenia intersepta . Flow cytometry analyses of water sam...
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Planktonic communities constitute the basis of life in marine environments and have profound impacts in geochemical cycles. In the North Atlantic, seasonality drives annual transitions in the ecology of the water column. Phytoplankton bloom annually in spring as a result of these transitions, creating one of the major biological pulses in productiv...
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Much is known about how broad eukaryotic phytoplankton groups vary according to nutrient availability in marine ecosystems. However, genus- and species-level dynamics are generally unknown, although important given that adaptation and acclimation processes differentiate at these levels. We examined phytoplankton communities across seasonal cycles i...
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The North Atlantic phytoplankton spring bloom is the pinnacle in an annual cycle that is driven by physical, chemical, and biological seasonality. Despite its important contributions to the global carbon cycle, transitions in plankton community composition between the winter and spring have been scarcely examined in the North Atlantic. Phytoplankto...
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Metacaspases and paracaspases are proteases that were first identified as containing a caspase-like structural fold (Uren et al., 2000). Like caspases, metacas-pases and paracaspases are multi-functional proteins regulating diverse biological phenomena, such as aging, immunity , proteostasis, and programmed cell death. The broad phylogenetic distri...
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Giant viruses are remarkable for their large genomes, often rivaling those of small bacteria, and for having genes thought exclusive to cellular life. Most isolated to date infect nonmarine protists, leaving their strategies and prevalence in marine environments largely unknown. Using eukaryotic single-cell metagenomics in the Pacific, we discovere...
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Many marine microbial eukaryotes combine photosynthetic with phagotrophic nutrition, but incomplete understanding of such mixotrophic protists, their functional diversity and underlying physiological mechanisms limits assessment and modeling of their roles in present and future ocean ecosystems. We developed an experimental system to study response...
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Marine algae perform approximately half of global carbon fixation, but their growth is often limited by the availability of phosphate or other nutrients1,2. As oceans warm, the area of phosphate-limited surface waters is predicted to increase, resulting in ocean desertification3,4. Understanding the responses of key eukaryotic phytoplankton to nutr...
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Bathycoccus and Ostreococcus are broadly distributed marine picoprasinophyte algae. We enumerated small phytoplankton using flow cytometry and qPCR assays for phylogenetically distinct Bathycoccus clades BI and BII and Ostreococcus clades OI and OII. Among 259 photic-zone samples from transects and time-series, Ostreococcus maxima occurred in the N...
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While considerable effort has been devoted to understanding the factors regulating the development of phytoplankton blooms, the mechanisms leading to bloom decline and termination have received less attention. Grazing and sedimentation have been invoked as the main routes for the loss of phytoplankton biomass, and more recently, viral lysis, parasi...
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Ocean surface warming is resulting in an expansion of stratified, low-nutrient environments, a process referred to as ocean desertification [1]. A challenge for assessing the impact of these changes is the lack of robust baseline information on the biological communities that carry out marine photosynthesis. Phytoplankton perform half of global bio...
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Algae of many taxa show evidence of intrinsically-driven mortality (cell death), especially in response to environmental stresses. Such cell death shows some similarities to forms described in animals and plants (e.g. apoptosis and necrosis), but clear definitions are elusive, even in these multicellular groups. Accumulating physiological and molec...
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The effects of intensity and timing of disturbances on recovery of marine benthic organisms were investigated on a rocky intertidal shore in Gwangyang Bay, Korea. We hypothesized that the recovery pattern of the benthic community structure would be affected by disturbance intensity and season. Twenty-eight permanent plots were set up, with disturba...
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Metacaspases are evolutionarily distant homologs of caspases that are found outside the metazoan and are known to have key roles in programmed cell death (PCD). Two types of metacaspases (types I and II) have been defined in plants based on their domain structures; these have similarities to metazoan 'initiator' and 'executioner' caspases. However,...
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Chlorophyll a fluorescence of microalgae is a compelling indicator of toxicity of dissolved water contaminants, because it is easily measured and responds rapidly. While different chl a fluorescence parameters have been examined, most studies have focused on single species and/or a narrow range of toxins. We assessed the utility of one chl a fluore...
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Measurements of the efficiency of photosystem (PS) II have become widespread in bio- logical oceanography, and various forms are used to assess the ‘health’ of marine phytoplankton and to help estimate primary productivity. Absolute values of PS II efficiency depend to some extent on the measuring system, but changes in PS II efficiency are most co...
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Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology....
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Dickeya dadantii (Erwinia chrysanthemi 3937) secretes exoenzymes, including pectin-degrading enzymes, leading to the loss of structural integrity of plant cell walls. A type III secretion system (T3SS) is essential for full virulence of this bacterium within plant hosts. The GacS/GacA two-component signal transduction system participates in importa...

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