Identifier

etd-07012016-120651

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Approximately 2,300 petroleum platforms are currently operating in the Gulf of Mexico (GOM), and are estimated to provide an additional 4 to 12 km2 of artificial reef habitat. The ecological role of platforms has often been overlooked and little is known about the effect of artificial light from the active platforms on surrounding fish communities. This is the first study to address the potential impacts of artificial light on the trophic ecology of fish communities surrounding offshore platforms through gut content (GCA) and stable isotope (SIA) analyses. Red snapper (Lutjanus campechanus) were collected quarterly from February 2014 to November 2015 (n=424). Samples were taken at two active “lit” platforms and two unmanned “unlit” platforms located approximately 130 km from the coast of Louisiana. Results reveal seasonal, ontogenetic, and platform-type related differences. Although light was not a significant factor in the non-parametric GCA analysis, a higher abundance of fish prey items was observed in the diets at lit platforms. Trophic niche breadth analysis revealed significantly different niches between types of platforms. Higher δ15N at lit platforms corresponds to higher concentration of fish prey in the diets, compared to the lower δ15N associated with the abundance of tunicates in the diets at unlit platforms. A mixing model revealed that phytoplankton is the dominant carbon source in these oligotrophic, platform environments. Red snapper at lit platforms were slightly enriched in δ13C compared to those at unlit platforms. This could be attributable to the greater amount of green algae as a basal carbon source of individuals at lit platforms revealed by the mixing model, which is enriched in δ13C relative to phytoplankton. Feeding ecology of greater amberjack revealed fish to be the dominant prey items between lit and unlit platforms, and across both artificial and natural habitats. Trophic niche breadth analysis revealed significant differences between greater amberjack at lit and unlit platforms, which is likely attributable to the varying basal carbon resource. This study provides important information that may be used in the decision on installment or removal of platforms as fish habitats in the future and to assist with fisheries management.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Cowan Jr., James

DOI

10.31390/gradschool_theses.2997

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