{"663101":{"#nid":"663101","#data":{"type":"event","title":"PhD Defense by  Madison Willert","body":[{"value":"\u003Cp\u003EIn partial fulfillment of the requirements for the degree of\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EDoctor of Philosophy in Biology\u003C\/p\u003E\r\n\r\n\u003Cp\u003EIn the\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EMadison Willert\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EWill defend her dissertation\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003EAnthropogenic-Mediated Simplification of Marine Food Webs\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E28 November 2022\u003C\/p\u003E\r\n\r\n\u003Cp\u003E12:30 PM\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Ca href=\u0022https:\/\/smithsonian.zoom.us\/j\/6458666440?pwd=VWNUeGVZT25iOFFTaGN5ODY1anhidz09\u0022\u003Ehttps:\/\/smithsonian.zoom.us\/j\/6458666440?pwd=VWNUeGVZT25iOFFTaGN5ODY1anhidz09\u003C\/a\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EMeeting ID: 645 866 6440, Passcode: 274690\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003Cstrong\u003EThesis Advisor:\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EMark Hay, Ph.D.\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\r\n\r\n\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cstrong\u003ECommittee Members:\u003C\/strong\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EJoseph Montoya, Ph.D.\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\r\n\r\n\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003ELin Jiang, Ph.D.\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\r\n\r\n\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003ECarole Baldwin, Ph.D.\u003C\/p\u003E\r\n\r\n\u003Cp\u003ENational Museum of Natural History\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESmithsonian Institution\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EChristine France, Ph.D.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EMuseum Conservation Institute\u003C\/p\u003E\r\n\r\n\u003Cp\u003ESmithsonian Institution\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EABSTRACT: Anthropogenic-mediated stressors such as overexploitation, habitat destruction, climate change, and species introductions are changing food webs in marine ecosystems. In this dissertation, I first evaluate how these stressors are shifting trophic interactions via increased dietary overlap and interspecific competition within trophic levels, truncation of nutrient flow between trophic levels and ecosystems, and simplification and compression of entire food webs. Stable isotope analysis is a powerful tool to measure species\u0026rsquo; trophic positions and thus, food web shifts over time and space. I show that \u003Cem\u003E\u0026delta;\u003C\/em\u003E15N values and \u003Cem\u003E\u0026delta;\u003C\/em\u003E13C values from formalin-preserved seaweeds are generally reliable, validating stable isotope analysis of herbarium specimens. Seaweeds are useful as nutrient baselines for trophic ecology studies, as well as for assessing nutrient runoff and pollution; this finding shows that preserved herbarium specimens can be used in these types of studies to reconstruct food webs of the past. I then use nitrogen stable isotope analysis of both herbarium specimens and museum fish specimens from New England, USA to show that the common piscivore \u003Cem\u003ECentropristis striata \u003C\/em\u003E(black sea bass) and the common benthivore \u003Cem\u003EStenotomus chrysops \u003C\/em\u003E(scup) have experienced significant declines in trophic position in this area since pre-1950. \u003Cem\u003EC. striata \u003C\/em\u003Edeclined almost a full trophic level and \u003Cem\u003ES. chrysops \u003C\/em\u003Edeclined half a trophic level, and these species are now converging on similar trophic positions coincident with the increase in destructive bottom fishing in New England. Next, I used nitrogen stable isotope analysis of \u0026gt;1000 museum fish specimens from coral reefs worldwide to assess dietary changes of common coral reef mesopredators since 1850 in regions of both the tropical Atlantic and the Indo-Pacific. I found that trophic instability has been common in the tropical Atlantic during the 20th century, with the trophic position of most Atlantic species decreasing further going into the 21st century. Unlike in the Atlantic, historically unstable species in the Indo-Pacific are now increasing in their trophic positions; this suggests that relatively higher levels of overfishing and coral loss in the tropical Atlantic are reflected in greater mesopredator trophic instability. Finally, I used nitrogen and carbon stable isotope analysis of vertebrae from \u003Cem\u003ESphyrna mokarran \u003C\/em\u003E(great hammerhead) and \u003Cem\u003ESphyrna lewini \u003C\/em\u003E(scalloped hammerhead) sharks to evaluate ontogenetic shifts in these two species in the U.S. South Atlantic and the eastern Gulf of Mexico. \u003Cem\u003ES. lewini \u003C\/em\u003Eoccupies a high trophic position throughout its life, reaching peak predator status as a subadult and occupying more offshore pelagic habitats. Despite its larger body size, \u003Cem\u003ES. mokarran \u003C\/em\u003Eoccupies a lower trophic position and relies more on benthic and inshore habitats, especially in the juvenile stage. I elucidated the nuances of these predators\u0026rsquo; trophic ecology and found no evidence of within- species differences in sex or location with regards to dietary habits. A better understanding of individual species\u0026rsquo; trophic ecology, as well as historic human impacts on marine food webs, is crucial to maintaining and promoting healthy ecosystems into the future.\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Anthropogenic-Mediated Simplification of Marine Food Webs"}],"uid":"27707","created_gmt":"2022-11-11 16:20:42","changed_gmt":"2022-11-11 16:20:42","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2022-11-28T12:30:00-05:00","event_time_end":"2022-11-28T14:00:00-05:00","event_time_end_last":"2022-11-28T14:00:00-05:00","gmt_time_start":"2022-11-28 17:30:00","gmt_time_end":"2022-11-28 19:00:00","gmt_time_end_last":"2022-11-28 19:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}