Assessments of surface-pelagic drift communities and behavior of early juvenile sea turtles in the northern Gulf of Mexico

• Main Author: Hardy, Robert F.
• Format: Thesis
• Language: unknown
• Published: Digital Commons @ University of South Florida 2014
• Subjects: critical habitat; developmental habitat; Landsat; remote sensing; Sargassum; satellite telemetry; Marine Biology; Oceanography; North Atlantic
• Online Access: https://digitalcommons.usf.edu/etd/5367; https://digitalcommons.usf.edu/context/etd/article/6561/viewcontent/Hardy_usf_0206M_12579.pdf

Knowledge of species distribution and habitat associations are essential for conservation measures. Such information is lacking for many marine species due to their occupancy of broad and ephemeral habitats that are difficult to access for study. Sea turtles, specifically the surface-pelagic juvenile stage of some species, are a group for which significant knowledge gaps remain surrounding their distribution and habitat use. Recent research has confirmed the long-standing hypothesis that the surface-pelagic juvenile stage occurs within surface-pelagic drift communities (SPDC). Within the North Atlantic and surrounding basins, the holopelagic macroalgae Sargassum spp. dominates SPDC and serves as a remotely-detectable indicator of SPDC. The present study focuses on surface-pelagic habitats of four sea turtle species and addresses knowledge gaps using two approaches: habitat mapping and behavioral examination. Remote sensing techniques were used to identify SPDC, and satellite telemetry to examine behavior. This work was conducted in three parts and is presented in three chapters. Imagery collected from the Landsat satellites (5 and 7) was used to quantify the area of SPDC (km2). Approximately 1,800 Landsat images collected from 2003–2011 were examined for SPDC. The first chapter discusses the abundance, seasonality, and distribution of SPDC within the eastern Gulf of Mexico waters where surface-pelagic green, hawksbill, Kemp’s ridley, and loggerhead turtles are known to occur. SPDC was found year-round within the eastern Gulf of Mexico, and the amount of habitat peaked during summer months. The amount of SPDC within the eastern Gulf of Mexico varied annually with peaks in 2005, 2009, and 2011. High concentrations of SPDC were discovered within offshore waters of the northeastern Gulf of Mexico and southern West Florida Shelf. Within the second chapter, the behavior of 10 surface-pelagic juvenile Kemp’s ridleys was examined using satellite telemetry. Using remotely-sensed imagery, the sea surface habitats used by ...