Showing 1 - 10 of 13 Items

• Embargo End Date: 2025-05-14

Date: 2020-01-01

Creator: Emma Victoria Bertke

Access: Embargoed

Date: 2018-05-01

Creator: Madeline Schuldt

Access: Access restricted to the Bowdoin Community

• Embargo End Date: 2029-05-16

Date: 2024-01-01

Creator: Nicholas Takaki Tienhui Yoong

Access: Embargoed

Date: 2022-01-01

Creator: Matthew L. Thomas

Access: Open access

This study investigates the potential benefits of using a broad, multi-ecosystem analysis in the licensing and relicensing of hydropower facilities. Specifically, it considers the impact of river herring restoration on coastal food webs and cod and other groundfish populations in the Gulf of Maine. The past two decades of research on fisheries management, ecosystem connectivity, and the connection between river herring and groundfish in the Gulf of Maine have resulted in a better understanding of the ways in which human activities, such as dam building, influence ecological processes. The paper analyzes two case studies of six Maine dams currently engaged in the Federal Energy Regulatory Commission’s (FERC) hydroelectric dam relicensing process. The analysis illustrates the shortcomings of the Federal Power Act’s provisions that address the balancing of ecological and power generation concerns. Following the case studies, a series of policy recommendations are presented to encourage a more transparent and predictable relicensing process that adequately values both ecological and power generation goals. Changes are suggested for both the FERC process itself and the process by which state and federal resource agencies may provide comments regarding how a proposed dam licensing or relicensing affects natural resources under their jurisdiction. The proposed policy recommendations will increase the resilience of natural systems as they adapt to climate impacts.

Date: 2016-10-01

Creator: Thomas G. Huntington, William M. Balch, George R. Aiken, Justin Sheffield, Lifeng, Luo, Collin S. Roesler, Philip Camill

Access: Open access

Ongoing climate change is affecting the concentration, export (flux), and timing of dissolved organic carbon (DOC) exported to the Gulf of Maine (GoM) through changes in hydrologic regime. DOC export was calculated for water years 1950 through 2013 for 20 rivers and for water years 1930 through 2013 for 14 rivers draining to the GoM. DOC export was also estimated for the 21st century based on climate and hydrologic modeling in a previously published study. DOC export was calculated by using the regression model LOADEST to fit seasonally adjusted concentration discharge (C-Q) relations. Our results are an analysis of the sensitivity of DOC export to changes in hydrologic conditions over time since land cover and vegetation were held constant over time. Despite large interannual variability, all rivers had increasing DOC export during winter and these trends were significant (p < 0.05) in 10 out of 20 rivers for 1950 to 2013 and in 13 out of 14 rivers for 1930 to 2013. All rivers also had increasing annual export of DOC although fewer trends were statistically significant than for winter export. Projections for DOC export during the 21st century were variable depending on the climate model and greenhouse gas emission scenario that affected future river discharge through effects on precipitation and evapotranspiration. The most consistent result was a significant increase in DOC export in winter in all model-by-emission scenarios. DOC export was projected to decrease during the summer in all model-by-emission scenarios, with statistically significant decreases in half of the scenarios.

Date: 2024-01-01

Creator: Brielle Martin

Access: Access restricted to the Bowdoin Community

Date: 2017-05-01

Creator: Aidan Fisher Coyle

Access: Open access

Hybrid zones provide natural laboratories to study how specific genes, and interactions among genes, may influence fitness. On the east coast of North America, two separate populations of the European green crab (Carcinus maenas) have been introduced in the last two centuries. An early invasion from Southern Europe colonized New England around 1800, and was followed by a second invasion from Northern Europe to Nova Scotia in the early 1980s (Roman 2006). As these populations hybridize, new combinations of genes potentially adapted to different ends of a thermal spectrum are created in a hybrid zone. To test the hypothesis that mitochondrial and nuclear genes have effects on thermal tolerance, I measured response to cold stress in crabs collected from locations between southern Maine and northern Nova Scotia, and then genotyped the mitochondrial CO1 gene and two nuclear SNPs. Three mitochondrial haplotypes, originally from Northern Europe, had a strong effect on the ability of crabs to right themselves at a temperature of 4.5ºC. Crabs carrying these three haplotypes were 20% more likely to right compared to crabs carrying the haplotype from Southern Europe. The two nuclear SNPs, which were derived from transcriptome sequencing and were strong outliers between Northern and Southern European C. maenas populations, had no effect on righting response at low temperature. These results add C. maenas to the short list of ectotherms in which mitochondrial variation affects thermal tolerance, and suggests that natural selection is shaping the structure of the hybrid zone between the northern and southern populations This discovery of linkage between mitochondrial genotype and thermal tolerance also provides potential insight into the patterns of expansion for invasive populations of C. maenas around the world.

• Embargo End Date: 2026-05-18

Date: 2023-01-01

Creator: Bridget Marjorie Patterson

Access: Embargoed

Date: 2019-01-01

Creator: Aidan F. Coyle, Erin R. Voss, Carolyn K. Tepolt, David B. Carlon

Access: Open access

Hybrid zones provide natural experiments in recombination within and between genomes that may have strong effects on organismal fitness. On the East Coast of North America, two distinct lineages of the European green crab (Carcinus maenas) have been introduced in the last two centuries. These two lineages with putatively different adaptive properties have hybridized along the coast of the eastern Gulf of Maine, producing new nuclear and mitochondrial combinations that show clinal variation correlated with water temperature. To test the hypothesis that mitochondrial or nuclear genes have effects on thermal tolerance, we first measured the response to cold stress in crabs collected throughout the hybrid zone, then sequenced the mitochondrial CO1 gene and two nuclear single nucleotide polymorphisms (SNPs) representative of nuclear genetic lineage. Mitochondrial haplotype had a strong association with the ability of crabs to right themselves at 4.5°C that was sex specific: haplotypes originally from northern Europe gave male crabs an advantage while there was no haplotype effect on righting in female crabs. By contrast, the two nuclear SNPs that were significant outliers in a comparison between northern and southern C. maenas populations had no effect on righting response at low temperature. These results add C. maenas to the shortlist of ectotherms in which mitochondrial variation has been shown to affect thermal tolerance, and suggest that natural selection is shaping the structure of the hybrid zone across the Gulf of Maine. Our limited genomic sampling does not eliminate the strong possibility that mito-nuclear co-adaptation may play a role in the differences in thermal phenotypes documented here. Linkage between mitochondrial genotype and thermal tolerance suggests a role for local adaptation in promoting the spread of invasive populations of C. maenas around the world.

Date: 2023-01-01

Creator: Meghan Gonzalez

Access: Access restricted to the Bowdoin Community