Abstract:

We examined particle size after sunlight irradiation in three natural seawaters, eight marine microbial exopolymeric substance solutions, and five standard biopolymer solutions. We found that protein-containing dissolved organic matter (DOM) polymers and reactive oxygen species play important roles in aggregate formation during irradiation. This dataset is related to GRIIDC dataset R4.x263.000:0044.

Suggested Citation:

Luni Sun, Meng-Hsuen Chiu, Wei-Chun Chin, Peter H. Santschi. 2018. Particle size of light induced aggregates using flow cytometry. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7TM78M3

Publications:

Sun, L., Chin, W.-C., Chiu, M.-H., Xu, C., Lin, P., Schwehr, K. A., … Santschi, P. H. (2019). Sunlight induced aggregation of dissolved organic matter: Role of proteins in linking organic carbon and nitrogen cycling in seawater. Science of The Total Environment, 654, 872–877. doi:10.1016/j.scitotenv.2018.11.140

Purpose:

To investigate the possibility of light induced aggregation of natural seawaters and relevant roles of protein-containing DOM.

Data Parameters and Units:

EPS=exopolymeric substance ASW=artificial seawater GOM=gulf of Mexico ss1= S. stellate 1; ss2= S. stellate 2; amp= Amphora sp.; tp1= Thalassiosira Pseudonana1; tp2= Thalassiosira Pseudonana2; pg= Phaeocystis Globosa; pt=P. tricornutum; GOM EPS=EPS obtained from GOM seawater; DMSO= Dimethyl sulfoxide; Dark=no exposure; Light=under irradiation; In each sample: FSC: forward scattering SSC: side scattering FSC-H: forward scattering– height FSC-W: forward scattering- width. SSC-A: side scattering- area SSC-H: side scattering- height SSC-W: side scattering- width FITC-A: fluorescein isothiocyanate- area FITC-H: fluorescein isothiocyanate- area DAPI (4',6-diamidino-2-phenylindole)-area DAPI (4',6-diamidino-2-phenylindole)-height Alexa Fluor 647-A: alexa fluorescent wave length 647 nm- area Time: the time (second) that the particle pass through the laser Event: represent the particle counts The number 1,2,3 in the end of sample name means replicate number

Methods:

The GOM seawater was collected from NOAA National Marine Fisheries Laboratory (Galveston, TX) and the SF seawater was collected at Torpedo Wharf of San Francisco Bay (San Francisco, CA). EPS were obtained from bacteria S. stellata and GOM, and four phytoplankton Amphora sp., Thalassiosira pseudonana, Phaeocystis globose, and P. tricornutum followed the procedures described in previous studies. The natural EPS and standard polymers including fetuin (CAS 9014817, Sigma), dextran (CAS 9004540, Sigma), alginic acid (EC 2326801, Fluka), and lipopolysaccharide (EC 2974730, Sigma) were dissolved in ASW (final concentration 2 mg/L). The effects of reactive oxygen species were tested by adding quenchers sodium pyrite (for hydrogen peroxide) and DMSO (for HO) to GOM seawater respectively (final concentration 1 mM). All samples were passed through a 0.2 μm polycarbonate filter (Millipore) to remove any particles before irradiation in 250 mL quartz flasks in a circulating water bath (22±1 ºC) under natural sunlight, with a mean light dose of 1.2 Wm−2 of UVB, 16 Wm−2 of UVA, and 840 Wm−2 of PAR measured by radiometer (Solarmeter Ltd). One set of flasks were wrapped with foil to be used as dark controls. After 1 h, all samples were harvested for further analysis. The particle sizing was measured by flow cytometry. 1 mL sample was injected onto LSR2 flow cytometer (BD Biosciences). The instrument was set to collect 10,000 count events and recorded signals from forward-scattering and side-scattering. The particles size distribution was determined by the forward- and side-scatter profile, x-axis and y-axis, respectively. Grouping by quarters, the associated numbers of Q1 to Q4 represent the relative population percentage. The Q2 represents the fraction of large-sized particles (average size around µm); Q2 was adjusted along x-axis to be the same for the dark and irradiated sample. The data is the particle sizing within Q2 quarter.

Instruments:

Flow cytometry: LSR2 flow cytometer (BD Biosciences).

Individual Files: