Villareal Tracy A.

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Villareal
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Tracy A.
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  • Article
    A novel immunofluorescence flow cytometry technique detects the expansion of brown tides caused by Aureoumbra lagunensis to the Caribbean Sea
    (American Society for Microbiology, 2014-06-06) Koch, Florian ; Kang, Y. ; Villareal, Tracy A. ; Anderson, Donald M. ; Gobler, Christopher J.
    During the past 3 decades, brown tides caused by the pelagophytes Aureococcus anophagefferens and Aureoumbra lagunensis have caused ecological and economic damage to coastal ecosystems across the globe. While blooms of A. lagunensis had previously been confined to Texas, in 2012, an expansive brown tide occurred on Florida's East Coast, causing widespread disruption within the Indian River and Mosquito Lagoons and generating renewed interest in this organism. A major impediment to detailed investigations of A. lagunensis in an ecosystem setting has been the absence of a rapid and reliable method for cell quantification. The combination of their small size (3 to 5 μm) and nondescript extracellular features makes identification and enumeration of these cells with conventional methods a challenge. Here we report the development of an immunological-based flow cytometry method that uses a fluorescently labeled antibody developed against A. lagunensis. This method is species specific, sensitive (detection limit of 1.5 × 103 cells ml−1), precise (1% relative standard deviation of replicated samples), and accurate (108% ± 8% recovery of spiked samples) over a wide range of cell concentrations. Furthermore, this method effectively quantifies A. lagunensis in both glutaraldehyde- and formalin-preserved samples, yields a high throughput of samples (∼35 samples h−1), and is cost-effective, making it an ideal tool for managers and scientists. This method successfully documented the recurrence of a brown tide bloom in Florida in 2013. Bloom densities were highest in June (>2.0 × 106 cells ml−1) and spanned >60 km from the Ponce de Leon inlet in the northern Mosquito Lagoon south to Titusville in the Indian River Lagoon. Low levels of A. lagunensis cells were found >250 km south of this region. This method also quickly and accurately identified A. lagunensis as the causative agent of a 2013 brown tide bloom in Guantanamo Bay, Cuba, and thus should prove useful for both quantifying the dynamics of ongoing blooms of A. lagunensis as well as documenting new outbreaks of this harmful alga.
  • Dataset
    Event logs from R/V Oceanus, R/V Endeavor cruises OC468-02, EN496, EN509, EN510 in the Gulf of Mexico; 2010-2012 (GoMX - N2 Fixation project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-10-29) Montoya, Joseph P. ; Villareal, Tracy A.
    Event logs from R/V Oceanus, R/V Endeavor cruises OC468-02, EN496, EN509, EN510 in the Gulf of Mexico; 2010-2012 (GoMX - N2 Fixation project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3895
  • Article
    Upward nitrate transport by phytoplankton in oceanic waters : balancing nutrient budgets in oligotrophic seas
    (PeerJ, 2014-03-13) Villareal, Tracy A. ; Pilskaln, Cynthia H. ; Montoya, Joseph P. ; Dennett, Mark R.
    In oceanic subtropical gyres, primary producers are numerically dominated by small (1–5 µm diameter) pro- and eukaryotic cells that primarily utilize recycled nutrients produced by rapid grazing turnover in a highly efficient microbial loop. Continuous losses of nitrogen (N) to depth by sinking, either as single cells, aggregates or fecal pellets, are balanced by both nitrate inputs at the base of the euphotic zone and N2-fixation. This input of new N to balance export losses (the biological pump) is a fundamental aspect of N cycling and central to understanding carbon fluxes in the ocean. In the Pacific Ocean, detailed N budgets at the time-series station HOT require upward transport of nitrate from the nutricline (80–100 m) into the surface layer (∼0–40 m) to balance productivity and export needs. However, concentration gradients are negligible and cannot support the fluxes. Physical processes can inject nitrate into the base of the euphotic zone, but the mechanisms for transporting this nitrate into the surface layer across many 10s of m in highly stratified systems are unknown. In these seas, vertical migration by the very largest (102–103 µm diameter) phytoplankton is common as a survival strategy to obtain N from sub-euphotic zone depths. This vertical migration is driven by buoyancy changes rather than by flagellated movement and can provide upward N transport as nitrate (mM concentrations) in the cells. However, the contribution of vertical migration to nitrate transport has been difficult to quantify over the required basin scales. In this study, we use towed optical systems and isotopic tracers to show that migrating diatom (Rhizosolenia) mats are widespread in the N. Pacific Ocean from 140°W to 175°E and together with other migrating phytoplankton (Ethmodiscus, Halosphaera, Pyrocystis, and solitary Rhizosolenia) can mediate time-averaged transport of N (235 µmol N m-2 d-1) equivalent to eddy nitrate injections (242 µmol NO3− m-2 d-1). This upward biotic transport can close N budgets in the upper 250 m of the central Pacific Ocean and together with diazotrophy creates a surface zone where biological nutrient inputs rather than physical processes dominate the new N flux. In addition to these numerically rare large migrators, there is evidence in the literature of ascending behavior in small phytoplankton that could contribute to upward flux as well. Although passive downward movement has dominated models of phytoplankton flux, there is now sufficient evidence to require a rethinking of this paradigm. Quantifying these fluxes is a challenge for the future and requires a reexamination of individual phytoplankton sinking rates as well as methods for capturing and enumerating ascending phytoplankton in the sea.
  • Preprint
    High concentrations of marine snow and diatom algal mats in the North Pacific Subtropical Gyre : implications for carbon and nitrogen cycles in the oligotrophic ocean
    ( 2005-08-02) Pilskaln, Cynthia H. ; Villareal, Tracy A. ; Dennett, Mark R. ; Darkangelo-Wood, C. ; Meadows, G.
    A Video Plankton Recorder (VPR) and remotely operated vehicle (ROV) were utilized on three cruises in the oligotrophic North Pacific Subtropical Gyre (NPSG) between 1995 and 2002 to quantify the size and abundance of marine snow and Rhizosolenia diatom mats within the upper 305 m of the water column. Quantitative image analysis of video collected by the VPR and an ROV-mounted particle imaging system provides the first transect of marine snow size and abundance across the central North Pacific gyre extending from 920 km NW of Oahu to 555 km off Southern California. Snow abundance in the upper 55 m was surprisingly high for this oligotrophic region, with peak values of 6.0-13.0 x 103 aggregates m-3 at the western and eastern-most stations. At stations located in the middle of the transect (farthest from HI and CA), upper water column snow abundance displayed values of ~0.5-1.0 x 103 aggregates m-3. VPR and ROV imagery also provided in-situ documentation of the presence of nitrogen-transporting, vertically migrating Rhizosolenia mats from the surface to >300 m with mat abundances ranging from 0-10 mats m-3. There was clear evidence that Rhizosolenia mats commonly reach sub-nutricline depths. The mats were noted to be a common feature in the North Pacific gyre, with the lower salinity edge of the California Current appearing to be the easternmost extent of their oceanic distribution. Based on ROV observations at depth, flux by large (>1.5 cm) mats is revised upward 4.5 fold, yielding an average value of 40 µmol N m-2 d-1, a value equaling previous estimates that included much smaller mats visible only to towed optical systems. Our results suggest that the occurrence across a broad region of the NPSG of particulate organic matter (POM) production events represented by high concentrations of Rhizosolenia mats, associated mesozooplankton, and abundant detrital marine aggregates may represent significant stochastic components in the overall carbon, nitrogen and silica budgets of the oligotrophic subtropical gyre. Likewise, their presence has important implications for the proposed climate-driven, ecosystem reorganization or domain shift occurring in the NPSG.