Land use practices and physical alterations of ecosystems result in habitat loss and fragmentation, while chemical alterations, such as pollutant input, reduce habitat quality and health of exposed organisms. Here, I investigated the effects of watershed- and local-scale environmental variables on the occupancy, abundance, and mercury accumulation of a threatened aquatic species (Macrochelys temminckii, i.e., alligator snapping turtle) within the southwestern periphery of its distribution. Hierarchical modeling suggested the distribution of the species is more affected by watershed-scale land-cover than local habitat, and provided a baseline estimate of average species abundance across its range in eastern Texas. Abundance and occupancy were predicted by geographic location, and occupancy associated positively with forest cover. Mercury concentrations were predicted by environmental features at multiple scales, whereas body size had little effect. This research corroborates evidence that land use impacts aquatic species, as well as the susceptibility of aquatic systems to mercury accumulation.
","abstract_html":"<p>Land use practices and physical alterations of ecosystems result in habitat loss and fragmentation, while chemical alterations, such as pollutant input, reduce habitat quality and health of exposed organisms. Here, I investigated the effects of watershed- and local-scale environmental variables on the occupancy, abundance, and mercury accumulation of a threatened aquatic species (<em>Macrochelys temminckii</em>,<em> </em>i.e., alligator snapping turtle) within the southwestern periphery of its distribution. Hierarchical modeling suggested the distribution of the species is more affected by watershed-scale land-cover than local habitat, and provided a baseline estimate of average species abundance across its range in eastern Texas. Abundance and occupancy were predicted by geographic location, and occupancy associated positively with forest cover. Mercury concentrations were predicted by environmental features at multiple scales, whereas body size had little effect. This research corroborates evidence that land use impacts aquatic species, as well as the susceptibility of aquatic systems to mercury accumulation.</p>","abstract_has_math":false,"creators":["Rosenbaum, David"],"institution":null,"degree_name":"Master of Science - Forestry","degree_level":"Thesis","degree_discipline":"Forestry","degree_department":null,"school":null,"contributors":["Yanli Zhang","Christopher M. Schalk","Daniel Saenz"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-05-07T07:00:00Z","date_published":"2022-05-07T07:00:00Z","updated_at":"2026-07-24T04:30:37Z","subjects":["occupancy","abundance","occupancy model","wildlife monitoring","conservation","ecology","mercury","Biodiversity","Forest Management","Population Biology","Zoology"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarworks.sfasu.edu/etds/444","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Yanli Zhang","Christopher M. Schalk","Daniel Saenz"]},{"key":"dc:creator","label":"Author","values":["Rosenbaum, David"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2023-05-03T07:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Forestry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science - Forestry"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["occupancy","abundance","occupancy model","wildlife monitoring","conservation","ecology","mercury","Biodiversity","Forest Management","Population Biology","Zoology"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarworks.sfasu.edu/etds/444"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Land use practices and physical alterations of ecosystems result in habitat loss and fragmentation, while chemical alterations, such as pollutant input, reduce habitat quality and health of exposed organisms. Here, I investigated the effects of watershed- and local-scale environmental variables on the occupancy, abundance, and mercury accumulation of a threatened aquatic species (Macrochelys temminckii, i.e., alligator snapping turtle) within the southwestern periphery of its distribution. Hierarchical modeling suggested the distribution of the species is more affected by watershed-scale land-cover than local habitat, and provided a baseline estimate of average species abundance across its range in eastern Texas. Abundance and occupancy were predicted by geographic location, and occupancy associated positively with forest cover. Mercury concentrations were predicted by environmental features at multiple scales, whereas body size had little effect. This research corroborates evidence that land use impacts aquatic species, as well as the susceptibility of aquatic systems to mercury accumulation.
"]},{"key":"dc:title","label":"Title","values":["Detection, Occupancy, Abundance, and Mercury Accumulation of the Alligator Snapping Turtle (Macrochelys temminckii) in Texas"]}]}],"canonical_facts":{"dc:contributor":["Yanli Zhang","Christopher M. Schalk","Daniel Saenz"],"dc:creator":["Rosenbaum, David"],"dc:date.available":["2023-05-03T07:00:00Z"],"dc:description.abstract":["Land use practices and physical alterations of ecosystems result in habitat loss and fragmentation, while chemical alterations, such as pollutant input, reduce habitat quality and health of exposed organisms. Here, I investigated the effects of watershed- and local-scale environmental variables on the occupancy, abundance, and mercury accumulation of a threatened aquatic species (Macrochelys temminckii, i.e., alligator snapping turtle) within the southwestern periphery of its distribution. Hierarchical modeling suggested the distribution of the species is more affected by watershed-scale land-cover than local habitat, and provided a baseline estimate of average species abundance across its range in eastern Texas. Abundance and occupancy were predicted by geographic location, and occupancy associated positively with forest cover. Mercury concentrations were predicted by environmental features at multiple scales, whereas body size had little effect. This research corroborates evidence that land use impacts aquatic species, as well as the susceptibility of aquatic systems to mercury accumulation.
"],"dc:identifier":["https://scholarworks.sfasu.edu/etds/444"],"dc:subject":["occupancy","abundance","occupancy model","wildlife monitoring","conservation","ecology","mercury","Biodiversity","Forest Management","Population Biology","Zoology"],"dc:title":["Detection, Occupancy, Abundance, and Mercury Accumulation of the Alligator Snapping Turtle (Macrochelys temminckii) in Texas"],"thesis:degree_discipline":["Forestry"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science - Forestry"]},"updated_at":"2026-07-24T04:30:37Z"}