Methylmercury (MeHg) is a global pollutant that can bioaccumulate and biomagnify along the aquatic food chain, causing adverse outcomes in humans and wildlife. Effective biomonitoring programs are needed to identify high exposure populations and to develop proper mitigation strategies. However, biomonitoring results showed high inter-individual variability in the relationship between MeHg exposure and body burden. Moreover, the gut microbiota can potentially play a role in MeHg transformations, and it is widely believed that the gut microbiota may be the underlying reason for the variability between and within a population. However, the microbially-mediated mechanisms of Hg transformation in the gastrointestinal environment is poorly understood. The overarching goal of my thesis is to investigate the role of gut microbiota in MeHg transformation in human, and the relationship between environmental pollutants and the gut microbiota of sentinel species such as river otters (Lontra canadensis) and seabirds (Arctic Tern [Sterna paradisaea], Black Guillemot [Cepphus grille], Common Eider [Somateria mollissima], Double-crested Cormorant [Phalacrocorax auratus], and Leach’s Storm Petrel [Oceanodroma leucorhoa]). My thesis consists of four research papers. In the first paper, I discovered that the gut microbiota`s ability to demethylate MeHg is significantly enhanced by altering the diet. In my second paper, I discovered a novel MeHg degradation pathway. In the third and fourth papers, I explored the effect of Hg and other environmental contaminant exposure on river otters and seabirds gut microbial community structures and found a relationship between prey selection and diet to the gut microbial structure. In conclusion, my thesis explores the relationship between diet, prey selection, environment contaminants and the humans and wildlife gut microbiota and contributes to understanding the gut microbiota’s role in biomonitoring of ecosystem and human health.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Dec. 7, 2009). Includes bibliographical references.

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Thesis (Ph. D.)--University of California, Davis, 2002. / Includes bibliographical references. Also available via the World Wide Web. (Restricted to UC campuses).

Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 48-49).

In the 1950s the otter started to decline in numbers and distribution in Sweden and other parts of Europe. In 1972 a game law came into force, listing otter as a species that if found dead should be reported and sent to the authorities. The numbers of dead otters reported from different areas indicate population status and distribution. Between 1970 and 2012, 832 otters were sent to the authorities, the majority (66%) during the last ten years. Most were killed in traffic accidents or drowned in fishing gear. However, the main cause of the decline is believed to be environmental contaminants. Experimental data show that a PCB residue level in muscle tissue of 12 mg/kg lw causes reproductive impairment in mink (Neovison vison), suggesting reproductive problems also in the highly PCB-exposed otters in Sweden. Since the bans of PCB and DDT in the mid-1970s, concentrations of these substances in otter and fish have decreased and the otter population is increasing. Few pathological changes in otters have been found that can be related to high contaminant concentrations. However, we found a correlation between elevated PCB concentrations and alterations in bone mineral density. No relationship was seen between DDE and bone parameters. The decline of the otter coincided with the decline of grey seals (Halichoerus grypus) and white-tailed sea eagles (Haliaeetus albicilla) in Sweden, all showing decreased reproductive outcome. Reproductive success started to increase for all of them around 1990 and during the same period concentrations of PCB and DDE have decreased in these species. The body condition among female otters has increased over the study period, indicating an improved health status. However, we found a high prevalence (71%) of cysts on the spermatic duct in otters collected between 1999 and 2012, possibly caused by endocrine disrupting chemicals. Although the organochlorine concentrations in otters have decreased, otters still face many problems. New threats to the otter population in Scandinavia are the perfluorinated chemicals, including PFOS and PFOA. Results in this thesis show an increasing trend for these compounds in otters up to 2011, including some extremely high concentrations of PFOS in otters from southern Sweden.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains vii, 137 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 71-76).

After steep declines due to overharvest and habitat loss, North American river otter (Lontra canadensis) populations have been increasing in most of the U.S. Radiotelemetry is an essential tool for understanding river otter habitat use, survival rates, and sources of mortality, which is important for successfully managing these growing populations. Surgically implanting radiotransmitters is standard for river otters, but strict requirements for the handling and transport of DEA-scheduled drugs for sedation, and the lack of accessible surgery suites, can limit researchers. My objectives were to: (1) develop a non-scheduled drug combination to sedate river otters and surgically implant intra-abdominal transmitters in a field setting, (2) determine survival rates and causes of mortality for river otters, and (3) quantify fourth order habitat selection at river otter daytime resting sites. During 2018-2020, I surgically implanted 24 river otters with transmitters in southern Illinois and monitored them via radiotelemetry to determine survival and causes of mortality. The effectiveness of the drug combination of Dexmedetomidine and Nalbuphine for chemically immobilizing river otters was tested to determine the appropriate dosage. I used homing to track river otters to 132 daytime resting sites where I described the structure used, closest water type, and distance to water; for 51 of these resting sites I also measured understory cover, overstory cover, distance to water, and presence of river otter and beaver sign. These 51 sites were paired with 1-4 random riparian locations, where I measured the same habitat variables. I then modeled habitat selection of daytime resting sites using conditional logistic regression. A combination of 0.06 mg dexmedetomidine/kg and 1.2 mg nalbuphine/kg injected intramuscularly followed by a 10-15 min induction period was sufficient to chemically immobilize river otters enough for further sedation with 1-4% isoflurane gas. Surgery in the field was successful, with only 2 sedation-related mortalities recorded. Estimated river otter survival was 0.84 ± 0.09 with no difference between males (0.83 ± 0.11) and females (0.86 ± 0.13) ( = 0, P = 0.900) and or between protected areas (0.80 ± 0.10) and harvested areas (0.83 ± 0.15) ( = 0.3, P = 0.600). Four river otters died (2 harvest, 2 unknown causes) during my study. Daytime rest sites were located in non-enclosed vegetation (n = 54) as well as enclosed sites, such as bank dens (n = 39), beaver lodges (n = 33), and wood piles (n = 6). River otters selected for greater understory cover at all sites, though enclosed sites had less understory cover than non-enclosed sites (all P ≤ 0.001). The top habitat selection model included the parameters understory cover and the beaver sign but did not include canopy cover. My study offers a novel way to sedate river otters without DEA-scheduled drugs, updates information about river otter survival, and provides new information on fourth order habitat selection at daytime resting sites.

Polycyclic aromatic compounds (PACs) are a group of chemicals encompassing thousands of different aromatic, alkyl aromatic and heterocyclic hydrocarbons (i.e.- containing N, S, or O- atoms); 16 of which have been designated as priority pollutants due to their toxicity and prevalence. Several studies have highlighted increases in the concentrations of C1-C4 alkylated PACs and heterocyclic aromatic hydrocarbons such as dibenzothiophenes in the atmosphere, water, soil and sediments, plants, wildlife and fish in the Athabasca Oil Sands Region (AOSR). Although there has been considerable research attention related to the toxic, carcinogenic and mutagenic properties of PACs, there is an increasing awareness that these chemicals may also have profound endocrine disrupting properties in wildlife. North American river otter (Lontra canadensis) are good indicators of ecosystem health due to their ecology and sensitivity to environmental pollutants. In this thesis, we first demonstrated the utility of adopting paleotoxicological frameworks in defining environmental baseline levels of PACs and likely biological effects from exposure to these complex environmental mixtures. These methods allowed us to reconstruct historical PAC deposition patterns to impacted areas while simultaneously determining likely biological effects such as endocrine disruption. Next, we showed how PACs exhibited trophic dilution in a Boreal food chain dominated by river otters. Snails, prey and predator fish, as well as river otters were collected from four main study areas in the AOSR in northeastern Alberta, Canada. Bioaccumulation factors such as biota-sediment accumulation factors (BSAF) and trophic magnification factors (TMF) were used to evaluate the partitioning behavior of PACs in the environment and subsequent risks to biota. Our results revealed localized enrichment of certain PACs and subsequent metabolism in higher order vertebrates. Finally, we successfully combined ecotoxicological and physiological analyses paired with population genetic estimates to investigate endocrine disruption and population-level responses to exposure to PACs. River otters are known for their habitual use of latrine sites. Latrine sites represent a unique opportunity for biomonitoring programs to study river otters using indirect sampling methods. In this thesis, PACs were characterized and evaluated in sediment, lower and higher trophic biota with demonstrated impacts on endocrine processes and river otter population health. Effects-based assessments such as the ones presented in this thesis are more powerful for environmental monitoring programs than stressor-based assessment methods (such as describing presence/absence or levels of contaminants) as they provide greater biological context to monitoring data. In turn, these are helpful in selecting triggers for environmental effects monitoring or adaptive management programs.

The purpose of this thesis is to document river otter (Lutra canadensis) distribution and reintroduction potential in northern Utah. Distribution was studied using data from 3 sources: 1) otter sighting records from Utah Division of Wildlife Resources; 2) surveys of Utah furbearer trappers and natural resources personnel; and 3) searches of streams for otter sign. Potential for river otter habitat/reintroduction was evaluated by assessing food, cover, and reintroduction attributes. Streams were ranked using an evaluation system based on data from the otter literature. Forty-six positive otter sightings were made in Utah by trappers, natural resources personnel, and the public, 1964-1988. Only 1.3% of 844.4 km of northern Utah streams had otter sign during winter and summer searches. General characteristics of northern Utah streams such as habitat type and stream gradient are suitable for river otters. However, stream alterations and livestock grazing have negatively impacted potential otter habitat. Ninety-four percent of the studied streams are presently unacceptable for reintroductions. Escape cover is the most limited habitat attribute, but food appears to be available in adequate quantities. We recommend no otter reintroductions be made until riparian zones are rehabilitated and protected. Reestablishment of stream bank vegetation is essential to provide escape cover for reintroduced otters. We also recommend control of pollution inputs and no further construction of reservoirs. Surveys of otter distribution and evaluation of potential reintroduction should be done on the Colorado River drainage in Utah.