Graduation Year

2024

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Kendra Daly, Ph.D.

Committee Member

Mark Luther, Ph.D.

Committee Member

Brad Seibel, Ph.D.

Keywords

Appendicularia, Environmental variability, Gelatinous zooplankton, Vertical distribution

Abstract

Larvaceans are filter-feeding gelatinous zooplankton whose contributions to marine biogeochemical processes are poorly constrained. By frequently shedding their particle-rich houses and producing dense fecal pellets, larvaceans contribute large amounts of particulate organic matter to deeper waters and to the sea floor. Despite their importance, little is known about larvacean abundance, distribution, and carbon production in the highly productive northeastern Gulf of Mexico (NEGOM). To address this gap in knowledge, we collected images of larvaceans at discrete depths in the upper 300 m of the water column between August 2010 –2014 using the Shadowed Image Particle Profiling and Evaluation Recorder (SIPPER) camera imaging system. Larvacean abundance varied spatially, seasonally, and interannually with integrated abundances ranging from 6,934 - 548,319 ind. m-2 (0–100 m). Larvacean integrated abundance did not significantly (p = 0.98) vary spatially between on- and off-shelf stations. The majority of larvaceans (geometric mean of 70 - 72%) were found in the upper 50 m at off-shelf and on-shelf stations across all seasons. The maximum larvacean abundance occurred over the shelf slope during winter (548,319 ind. m-2), and coincided with a chlorophyll bloom, even though chlorophyll was not generally a consistent predictor of larvacean abundance in other seasons or years. However, the depth of larvacean maximum concentration frequently occurred above the depth of the chlorophyll maximum. The estimated daily total carbon produced by larvaceans was 262–5,345 mg C m-2 day-1 for an estimated lifetime total of 1,049 – 21,383 mg C m-2. This study serves as a seasonal baseline for larvacean abundance and distribution in the NEGOM.

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