BEGIN:VCALENDAR VERSION:2.0 X-WR-CALNAME:EventsCalendar PRODID:-//hacksw/handcal//NONSGML v1.0//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/New_York LAST-MODIFIED:20240422T053451Z TZURL:https://www.tzurl.org/zoneinfo-outlook/America/New_York X-LIC-LOCATION:America/New_York BEGIN:DAYLIGHT TZNAME:EDT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 DTSTART:19700308T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU END:DAYLIGHT BEGIN:STANDARD TZNAME:EST TZOFFSETFROM:-0400 TZOFFSETTO:-0500 DTSTART:19701101T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU END:STANDARD END:VTIMEZONE BEGIN:VEVENT CATEGORIES:SMAST,Thesis/Dissertations DESCRIPTION:Department of Estuarine and Ocean Sciences MS Thesis Defense "O ptical Characterization of Particle Size Distributions and Their Relations hip to Phytoplankton Pigment Composition in the Northern Gulf of Mexico" B y:  Kara Falvey Advisor Steven Lohrenz (UMass Dartmouth) Committee Member s Geoffrey Cowles (UMass Dartmouth), and Jefferson Turner (UMass Dartmouth ), Friday May 1, 2026 12:00 PM SMAST East 102-103 836 S. Rodney French Blv d, New Bedford and via Zoom Abstract: Optical characterization of particle size distributions, particle volumes, and particle number concentrations was conducted and compared to phytoplankton size classes as inferred from phytoplankton pigment composition in the region of the northern Gulf of Me xico (nGOM) influenced by the Mississippi and Atchafalaya River systems. U sing a Laser In-Situ Scattering and Transmissometer (LISST 100X), we acqui red vertical profiles of particle concentration and size from nearshore es tuarine regions to open ocean waters. Profiles of spectral beam attenuatio n using an underwater absorption and attenuation spectrometer (AC-9) were acquired alongside the LISST measurements. These optical observations were compared to phytoplankton size classes as inferred from phytoplankton pig ment composition. Strong spatial gradients in particle volume and number c oncentration were observed in conjunction with variations in the magnitude of beam attenuation, with higher values in the estuary and inner shelf wa ters. The observed relationship between the spectral slope of the beam att enuation, γ, corrected for colored dissolved organic matter (CDOM) absorp tion, and the slope of the LISST-derived particle size distribution, ξ, f ollowed general theoretical expectations, although there were notable devi ations, particularly at estuary and inner shelf stations. The near-surface particle number and volume concentrations were examined in relation to wa ter mass type as well as in relation to phytoplankton composition and size class as inferred from high-pressure liquid chromatography (HPLC) pigment analyses. Near-surface particle volume and number concentration were high est in estuary waters as compared to outer shelf waters. The median fracti on of total chlorophyll associated with the microphytoplankton size fracti on (20 – 200 μm) was lower for mid-shelf stations compared to estuary a nd inner shelf stations. The median total volume fraction of larger partic les in the size range (20 – 200 μm) for inner and mid-shelf stations wa s significantly lower than for estuary stations. Outer shelf stations demo nstrated relatively large variability in chlorophyll fractions associated with the different size classes. Subsurface peaks were evident in vertical profiles of particle volume and number concentration and coincided with d istinct in phytoplankton pigment composition, providing insight about vert ical variations in community composition in relation to physical gradients . These findings provide novel information about particle characteristics and their relationship to phytoplankton composition in the nGOM. Join Meet ing https://umassd.zoom.us/j/92975455209 Note: Meeting ID and passcode req uired, email contact to obtain. For additional information, please contact Callie Rumbut at c.rumbut@umassd.edu\nEvent page: https://www.umassd.edu/ events/cms/optical-characterization-of-particle-size-distributions-and-the ir-relationship-to-phytoplankton-pigment-composition-in-the-northern-gulf- of-mexico-by-kara-falvey.php\nEvent link: https://umassd.zoom.us/j/9297545 5209 X-ALT-DESC;FMTTYPE=text/html:

Department of Estuarine and Oce an Sciences

\n

MS Thesis Defense

\n

"Optical Characterization of Particle Size Distributions and Their Relationship to Phytoplankton Pigme nt Composition in the Northern Gulf of Mexico"

\n

By:  Kara Falvey\n

Advisor

\n

Steven Lohrenz (UMass Dartmouth)

\n

Committee Members

\n

Geoffrey Cowles (UMass Dartmouth)\, and Jefferson Turner ( UMass Dartmouth)\,

\n

Friday May 1\, 2026

\n

12:00 PM

\n

SM AST East 102-103

\n

836 S. Rodney French Blvd\, New Bedford

\n

a nd via Zoom

\n

Abstract:

\n

Optical characterization of particle size distributions\, particle volumes\, and particle number concentration s was conducted and compared to phytoplankton size classes as inferred fro m phytoplankton pigment composition in the region of the northern Gulf of Mexico (nGOM) influenced by the Mississippi and Atchafalaya River systems. Using a Laser In-Situ Scattering and Transmissometer (LISST 100X)\, we ac quired vertical profiles of particle concentration and size from nearshore estuarine regions to open ocean waters. Profiles of spectral beam attenua tion using an underwater absorption and attenuation spectrometer (AC-9) we re acquired alongside the LISST measurements. These optical observations w ere compared to phytoplankton size classes as inferred from phytoplankton pigment composition. Strong spatial gradients in particle volume and numbe r concentration were observed in conjunction with variations in the magnit ude of beam attenuation\, with higher values in the estuary and inner shel f waters. The observed relationship between the spectral slope of the beam attenuation\, γ\, corrected for colored dissolved organic matter (CDOM) absorption\, and the slope of the LISST-derived particle size distribution \, ξ\, followed general theoretical expectations\, although there were no table deviations\, particularly at estuary and inner shelf stations. The n ear-surface particle number and volume concentrations were examined in rel ation to water mass type as well as in relation to phytoplankton compositi on and size class as inferred from high-pressure liquid chromatography (HP LC) pigment analyses. Near-surface particle volume and number concentratio n were highest in estuary waters as compared to outer shelf waters. The me dian fraction of total chlorophyll associated with the microphytoplankton size fraction (20 – 200 μm) was lower for mid-shelf stations compared t o estuary and inner shelf stations. The median total volume fraction of la rger particles in the size range (20 – 200 μm) for inner and mid-shelf stations was significantly lower than for estuary stations. Outer shelf st ations demonstrated relatively large variability in chlorophyll fractions associated with the different size classes. Subsurface peaks were evident in vertical profiles of particle volume and number concentration and coinc ided with distinct in phytoplankton pigment composition\, providing insigh t about vertical variations in community composition in relation to physic al gradients. These findings provide novel information about particle char acteristics and their relationship to phytoplankton composition in the nGO M.

\n

Join Meeting

\n

https://umassd.zoom.us/j/92975455209

\n

Note: Meeting ID and passcode required\, email contact to obtain.

\n

For additional information\, please contact Callie Rumbut at c.rumbut@u massd.edu

Event page: https://www.umassd.edu/events/cms/optical-characterization -of-particle-size-distributions-and-their-relationship-to-phytoplankton-pi gment-composition-in-the-northern-gulf-of-mexico-by-kara-falvey.php
Event link: https://umassd .zoom.us/j/92975455209

DTSTAMP:20260409T164807 DTSTART;TZID=America/New_York:20260501T120000 DTEND;TZID=America/New_York:20260501T130000 LOCATION:SMAST 101-103 SUMMARY;LANGUAGE=en-us:"Optical Characterization of Particle Size Distribut ions and Their Relationship to Phytoplankton Pigment Composition in the No rthern Gulf of Mexico" by Kara Falvey UID:15882abac96fb5e8d81f3d61f8e8ef41@www.umassd.edu END:VEVENT END:VCALENDAR