Now showing items 21-40 of 179

    • Climate Soundscapes

      Sandoval, Artemio Katooneh; Pearson, Heidi C. (Con Brio Chamber Series, 2022-11-19)
      Con Brio Chamber Series Presents CLIMATE SOUNDSCAPES Friday, November 18, 2022, 7:30 PM Kunéix Hidi Northern Light United Church Saturday, November 19, 2022, 2:00 PM Atrium at the APK State Library, Archives and Museum
    • Climate Soundscapes

      Pearson, Heidi C.; Sandoval, Artemio Katooneh (Con Brio Chamber Series, 2022-11-19)
      Con Brio Chamber Series Presents CLIMATE SOUNDSCAPES Friday, November 18, 2022, 7:30 PM Kunéix Hidi Northern Light United Church Saturday, November 19, 2022, 2:00 PM Atrium at the APK State Library, Archives and Museum
    • Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

      Beaudreau, Anne H.; Bergstrom, Carolyn A.; Whitney, Emily Jean; Duncan, Douglas H.; Lundstrom, Nina (Springer, 2022-03-23)
      Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.
    • Glacier runoff influences biogeochemistry and resource availabilityin coastal temperate rainforest streams: Implications for juvenile salmon growth

      Fellman, Jason B.; Bellmore, J. Ryan; Johnson, Connor; Dunkle, Matthew R.; Hood, Eran (Association for the Sciences of Limnology and Oceanography, 2022-10-01)
      Meltwater contributions to watersheds are shrinking as glaciers disappear, altering theflow, temperature, andbiogeochemistry of freshwaters. A potential consequence of this landscape change is that streamflow patternswithin glacierized watersheds will become more homogenous, potentially altering the capacity of watersheds tosupport Pacific salmon. To assess heterogeneity in stream habitat quality for juvenile salmon in a watershed inthe Alaska Coast Mountains, we collected organic matter and invertebrate drift and measured streamwater phys-ical and biogeochemical properties over the main runoff season in two adjacent tributaries, one fed mainly byrain and the other partially by glacier ice/snowmelt. We then used bioenergetic modeling to evaluate how tem-poral patterns in water temperature and invertebrate drift in each tributary influence juvenile salmon growthpotential. Across the study period, average invertebrate drift concentrations were similar in non-glacierizedMontana (0.33 mg m 3) and glacier-influenced McGinnis Creeks (0.38 mg m 3). However, seasonal patterns ofinvertebrate drift were temporally asynchronous between the two streams. Invertebrate drift and modeledfishgrowth were generally higher in McGinnis Creek in the spring and Montana Creek in the Summer. For juvenilesalmon, tracking these resource asynchronies by moving between tributaries resulted in 20% greater growththan could be obtained within either stream alone. These results suggest that hydrologic heterogeneity withinwatersheds may enhance the diversity of foraging and growth opportunities for mobile aquatic organisms,which may be essential for supporting productive and resilient natural salmon runs.
    • Seasonal and interannual variation in high‑latitude estuarine fsh community structure along a glacial to non‑glacial watershed gradient in Southeast Alaska

      Beaudreau, Anne H.; Bergstrom, Carolyn A.; Whitney, Emily Jean; Duncan, Douglas H.; Lundstrom, Nina (Springer, 2022-03-23)
      Along the Gulf of Alaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.
    • Blonde Indian: Audiobook

      Hayes, Ernestine (2023)
      In the spring, the bear returns to the forest, the glacier returns to its source, and the salmon returns to the fresh water where it was spawned. Drawing on the special relationship that the Native people of southeastern Alaska have always had with nature, Blonde Indian is a story about returning.
    • From canopy to consumer: what makes and modifes terrestrial DOM in a temperate forest

      Behnke, Megan; Fellman, Jason B.; D'Amore, David V.; Gomez, S. M.; Spencer, R. G. M. (Springer, 2022-03-02)
      To investigate how source and processing control the composition of “terrestrial” dissolved organic matter (DOM), we combine soil and tree leachates, tree DOM, laboratory bioincubations, and ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry in three common landscape types (upland forest, forested wetland, and poor fen) of Southeast Alaska’s temperate rainforest. Tree (Tsuga heterophylla and Picea sitchensis) needles and bark and soil layers from each site were leached, and tree stemflow and throughfall collected to examine DOM sources. Dissolved organic carbon concentrations were as high as 167 mg CL−1 for tree DOM, suggesting tree DOM fluxes may be substantial given the hypermaritime climate of the region. Condensed aromatics contributed as much as 38% relative abundance of spruce and hemlock bark leachates suggesting coniferous trees are potential sources of condensed aromatics to surface waters. Soil leachates showed soil wetness dictates DOM composition and processing, with wetland soils producing more aromatic formulae and allowing the preservation of traditionally biolabile, aliphatic formulae. Biodegradation impacted soil and tree DOM differently, and though the majority of source-specific marker formulae were consumed for all sources, some marker formulae persisted. Tree DOM was highly biolabile (> 50%) and showed compositional convergence where processing homogenized DOM from different tree sources. In contrast, wetland and upland soil leachate DOM composition diverged and processing diversified DOM from different soil sources during bioincubations. Increasing precipitation intensity predicted with climate change in Southeast Alaska will increase tree leaching and soil DOM flushing, tightening linkages between terrestrial sources and DOM export to the coastal ocean.
    • From canopy to consumer: what makes and modifies terrestrial DOM in a temperate forest

      Behnke, Megan; Fellman, Jason B.; D'Amore, David V.; Gomez, S. M.; Spencer, R. G. M. (Springer, 2022-03-02)
      To investigate how source and processing control the composition of “terrestrial” dissolved organic matter (DOM), we combine soil and tree leachates, tree DOM, laboratory bioincubations, and ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry in three common landscape types (upland forest, forested wetland, and poor fen) of Southeast Alaska’s temperate rainforest. Tree (Tsuga heterophylla and Picea sitchensis) needles and bark and soil layers from each site were leached, and tree stemflow and throughfall collected to examine DOM sources. Dissolved organic carbon concentrations were as high as 167 mg CL−1 for tree DOM, suggesting tree DOM fluxes may be substantial given the hypermaritime climate of the region. Condensed aromatics contributed as much as 38% relative abundance of spruce and hemlock bark leachates suggesting coniferous trees are potential sources of condensed aromatics to surface waters. Soil leachates showed soil wetness dictates DOM composition and processing, with wetland soils producing more aromatic formulae and allowing the preservation of traditionally biolabile, aliphatic formulae. Biodegradation impacted soil and tree DOM differently, and though the majority of source-specific marker formulae were consumed for all sources, some marker formulae persisted. Tree DOM was highly biolabile (> 50%) and showed compositional convergence where processing homogenized DOM from different tree sources. In contrast, wetland and upland soil leachate DOM composition diverged and processing diversified DOM from different soil sources during bioincubations. Increasing precipitation intensity predicted with climate change in Southeast Alaska will increase tree leaching and soil DOM flushing, tightening linkages between terrestrial sources and DOM export to the coastal ocean.
    • Glacier runoff influences biogeochemistry and resource availabilityin coastal temperate rainforest streams: Implications for juvenile salmon growth

      Fellman, Jason B.; Bellmore, J. Ryan; Johnson, Connor; Dunkle, Matthew R.; Hood, Eran (Association for the Sciences of Limnology and Oceanography, 2022-10-01)
      Meltwater contributions to watersheds are shrinking as glaciers disappear, altering theflow, temperature, andbiogeochemistry of freshwaters. A potential consequence of this landscape change is that streamflow patternswithin glacierized watersheds will become more homogenous, potentially altering the capacity of watersheds tosupport Pacific salmon. To assess heterogeneity in stream habitat quality for juvenile salmon in a watershed inthe Alaska Coast Mountains, we collected organic matter and invertebrate drift and measured streamwater phys-ical and biogeochemical properties over the main runoff season in two adjacent tributaries, one fed mainly byrain and the other partially by glacier ice/snowmelt. We then used bioenergetic modeling to evaluate how tem-poral patterns in water temperature and invertebrate drift in each tributary influence juvenile salmon growthpotential. Across the study period, average invertebrate drift concentrations were similar in non-glacierizedMontana (0.33 mg m 3) and glacier-influenced McGinnis Creeks (0.38 mg m 3). However, seasonal patterns ofinvertebrate drift were temporally asynchronous between the two streams. Invertebrate drift and modeledfishgrowth were generally higher in McGinnis Creek in the spring and Montana Creek in the Summer. For juvenilesalmon, tracking these resource asynchronies by moving between tributaries resulted in 20% greater growththan could be obtained within either stream alone. These results suggest that hydrologic heterogeneity withinwatersheds may enhance the diversity of foraging and growth opportunities for mobile aquatic organisms,which may be essential for supporting productive and resilient natural salmon runs.
    • Watershed Classification Predicts Streamflow Regime and Organic Carbon Dynamics in the Northeast Pacific Coastal Temperate Rainforest

      Giesbrecht, Ian; Tank, Suzanne; Frazer, Gordon W.; Hood, Eran; Gonzalez Arriola, Santiago G.; Butman, David E.; D'amore, David V.; Hutchinson, David; Bidlack, Allison Lynn; Lertzman, Ken P. (American Geophysical Union, 2022-01-28)
      Watershed classification has long been a key tool in the hydrological sciences, but few studies have been extended to biogeochemistry. We developed a combined hydro-biogeochemical classification for watersheds draining to the coastal margin of the Northeast Pacific coastal temperate rainforest (1,443,062 km2), including 2,695 small coastal rivers (SCR) and 10 large continental watersheds. We used cluster analysis to group SCR watersheds into 12 types, based on watershed properties. The most important variables for distinguishing SCR watershed types were evapotranspiration, slope, snowfall, and total precipitation. We used both streamflow and dissolved organic carbon (DOC) measurements from rivers (n = 104 and 90 watersheds respectively) to validate the classification. Watershed types corresponded with broad differences in streamflow regime, mean annual runoff, DOC seasonality, and mean DOC concentration. These links between watershed type and river conditions enabled the first region-wide empirical characterization of river hydrobiogeochemistry at the land-sea margin, spanning extensive ungauged and unsampled areas. We found very high annual runoff (mean > 3,000 mm, n = 10) in three watershed types totaling 59,024 km2 and ranging from heavily glacierized mountain watersheds with high flow in summer to a rain-fed mountain watershed type with high flow in fall-winter. DOC hotspots (mean > 4 mg L−1, n = 14) were found in three other watershed types (48,557 km2) with perhumid rainforest climates and less-mountainous topography. We described four patterns of DOC seasonality linked to watershed hydrology, with fall-flushing being widespread. Hydro-biogeochemical watershed classification may be useful for other complex regions with sparse observation networks.
    • Whales in the carbon cycle: can recovery remove carbon dioxide?

      Pearson, Heidi C.; Savoca, Matthew S.; Costa, Daniel P.; Lomas, Michael W.; Molita, Renato; Pershing, Andrew J.; Smith, Craig R.; Villaseñor-Derbez, Juan Carlos; Wing, Stephen R.; Roman, Joe (Elsevier Ltd., 2022-03)
      The great whales (baleen and sperm whales), through their massive size and wide distribution, influence ecosystem and carbon dynamics. Whales directly store carbon in their biomass and contribute to carbon export through sinking carcasses. Whale excreta may stimulate phytoplankton growth and capture atmospheric CO2; such indirect pathways represent the greatest potential for whale-carbon sequestration but are poorly understood. We quantify the carbon values of whales while recognizing the numerous ecosystem, cultural, and moral motivations to protect them. We also propose a framework to quantify the economic value of whale carbon as populations change over time. Finally, we suggest research to address key unknowns (e.g., bioavailability of whale derived nutrients to phytoplankton, species- and region-specific variability in whale carbon contributions).
    • mtDNA heteroplasmy gives rise to a new maternal lineage in North Pacific humpback whales

      Pierszalowski, Sophie P.; Steel, Debbie J.; Gabriele, Christine M.; Neilson, Janet L.; Vanselow, Phoebe B. S.; Cedarleaf, Jennifer A.; Straley, Janice M.; Baker, C. Scott (Oxford University Press, 2022)
      Heteroplasmy in the mitochondrial genome offers a rare opportunity to track the evolution of a newly arising maternal lineage in populations of non-model species. Here, we identified a previously unreported mitochondrial DNA haplotype while assembling an integrated database of DNA profiles and photo-identification records from humpback whales in southeastern Alaska (SEAK). The haplotype, referred to as A8, was shared by only two individuals, a mature female with her female calf, and differed by only a single base pair from a common haplotype in the North Pacific, referred to as A-. To investigate the origins of the A8 haplotype, we reviewed n = 1,089 electropherograms (including replicate samples) of n = 710 individuals with A- haplotypes from an existing collection. From this review, we found 20 individuals with clear evidence of heteroplasmy for A-/A8 (parental/derived) haplotypes. Of these, 15 were encountered in SEAK, four were encountered on the Hawaiian breeding ground (the primary migratory destination for whales in SEAK) and one was encountered in the northern Gulf of Alaska. We used genotype exclusion and likelihood to identify one of the heteroplasmic females as the likely mother of the A8 cow and grandmother of the A8 calf, establishing the inheritance and germ-line fixation of the new haplotype from the parental heteroplasmy. The mutation leading to this heteroplasmy and the fixation of the A8 haplotype provide an opportunity to document the population dynamics and regional fidelity of a newly arising maternal lineage in a population recovering from exploitation.
    • Sharp decline in humpback whale (Megaptera novaeangliae) survival and reproductive success in southeastern Alaska during and after the 2014–2016 Northeast Pacifc marine heatwave

      Gabriele, Christine M.; Amundson, Courtney L.; Nielson, Janet L.; Straley, Janice M.; Baker, C. Scott; Danielson, Seth Lombard (Springer, 2022-03-10)
      Understanding the ecosystem efects of ocean warming is increasingly important as marine heatwaves become more common and increase in severity. Here, we used Glacier Bay National Park long-term monitoring data (1985–2020) to investigate a sudden, sharp decline in humpback whale reproductive success and survival following the onset of the 2014–2016 Northeast Pacifc marine heatwave (PMH). Oceanographic data confrm a persistent warm-water anomaly in 2015–2016 in Glacier Bay, months later than the PMH was documented in the North Pacifc. We assessed changes in demographic parameters pre- and post-PMH using whale and calf counts and multi-state closed population capture–recapture models. Non-calf abundance decreased by 56% between 2013 and 2018, followed by increases in 2019–2020. The predicted proportion of females in the population declined in 2015–2017 (0.40–0.44). For 5 years during and after the heatwave (2015–2019) calf production was far lower than historic levels (0.041 calves per adult female, in contrast to 0.27 pre-PMH). Calf survival dropped tenfold beginning with calves born in 2013 (0.396–0.032) and midsummer calf losses occurred at an unprecedented rate starting in 2014. Non-calf survival declined from 0.982 pre-PMH to 0.899 post-PMH, lower than any value reported for this species. We surmise that documented changes to the forage fsh and zooplankton prey base during and after the PMH were the main driver of reduced humpback whale survival and reproductive success. Humpback whale abundance and productivity in southeastern Alaska will likely take years to recover from the PMH, assuming a return to favorable feeding conditions. Our work highlights this population’s continued vulnerability as the climate warms into previously unobserved states.
    • Long-period variability in ice-dammed glacier outburst floods due to evolving catchment geometry

      Jenson, Amy; Amundson, Jason M.; Kingslake, Jonathan; Hood, Eran (Copernicus Publications on behalf of the European Geosciences Union, 2022-01-25)
      We combine a glacier outburst flood model with a glacier flow model to investigate decadal to centennial variations in outburst floods originating from ice-dammed marginal basins. Marginal basins can form due to the retreat and detachment of tributary glaciers, a process that often results in remnant ice being left behind. The remnant ice, which can act like an ice shelf or break apart into a pack of icebergs, limits a basin’s water storage capacity but also exerts pressure on the underlying water and promotes drainage. We find that during glacier retreat there is a strong, nearly linear relationship between flood water volume and peak discharge for individual basins, despite large changes in glacier and remnant ice volumes that are expected to impact flood hydrographs. Consequently, peak discharge increases over time as long as there is remnant ice remaining in a basin, and peak discharge begins to decrease once a basin becomes ice-free. Thus, similar size outburst floods can occur at very different stages of glacier retreat. We also find that the temporal variability in outburst flood magnitude depends on how the floods initiate. Basins that connect to the subglacial hydrological system only after reaching flotation depth yield greater long-term variability in outburst floods than basins that are continuously connected to the subglacial hydrological system (and therefore release floods that initiate before reaching flotation depth). Our results highlight the importance of improving our understanding of both changes in basin geometry and outburst flood initiation mechanisms in order to better assess outburst flood hazards and their impacts on landscape and ecosystem evolution.
    • Long-period variability in ice-dammed glacier outburst floods due to evolving catchment geometry

      Jenson, Amy; Amundson, Jason M.; Kingslake, Jonathan; Hood, Eran (Copernicus Publications on behalf of the European Geosciences Union, 2022-01-25)
      We combine a glacier outburst flood model with a glacier flow model to investigate decadal to centennial variations in outburst floods originating from ice-dammed marginal basins. Marginal basins can form due to the retreat and detachment of tributary glaciers, a process that often results in remnant ice being left behind. The remnant ice, which can act like an ice shelf or break apart into a pack of icebergs, limits a basin’s water storage capacity but also exerts pressure on the underlying water and promotes drainage. We find that during glacier retreat there is a strong, nearly linear relationship between flood water volume and peak discharge for individual basins, despite large changes in glacier and remnant ice volumes that are expected to impact flood hydrographs. Consequently, peak discharge increases over time as long as there is remnant ice remaining in a basin, and peak discharge begins to decrease once a basin becomes ice-free. Thus, similar size outburst floods can occur at very different stages of glacier retreat. We also find that the temporal variability in outburst flood magnitude depends on how the floods initiate. Basins that connect to the subglacial hydrological system only after reaching flotation depth yield greater long-term variability in outburst floods than basins that are continuously connected to the subglacial hydrological system (and therefore release floods that initiate before reaching flotation depth). Our results highlight the importance of improving our understanding of both changes in basin geometry and outburst flood initiation mechanisms in order to better assess outburst flood hazards and their impacts on landscape and ecosystem evolution.
    • Seismic Mapping of Subglacial Hydrology Reveals Previously Undetected Pressurization Event

      Labedz, Celeste R.; Bartholomaus, Timothy, C.; Amundson, Jason M.; Gimbert, Florent; Karplus, Marianne; Tsai, Victor C.; Veitch, Stephen A. (American Geophysical Union, 2022-02-11)
      Understanding the dynamic response of glaciers to climate change is vital for assessing water resources and hazards, and subglacial hydrology is a key player in glacier systems. Traditional observations of subglacial hydrology are spatially and temporally limited, but recent seismic deployments on and around glaciers show the potential for comprehensive observation of glacial hydrologic systems. We present results from a high-density seismic deployment spanning the surface of Lemon Creek Glacier, Alaska. Our study coincided with a marginal lake drainage event, which served as a natural experiment for seismic detection of changes in subglacial hydrology. We observed glaciohydraulic tremor across the surface of the glacier that was generated by the subglacial hydrologic system. During the lake drainage, the relative changes in seismic tremor power and water flux are consistent with pressurization of the subglacial system of only the upper part of the glacier. This event was not accompanied by a significant increase in glacier velocity; either some threshold necessary for rapid basal motion was not attained, or, plausibly, the geometry of Lemon Creek Glacier inhibited speedup. This pressurization event would have likely gone undetected without seismic observations, demonstrating the power of cryoseismology in testing assumptions about and mapping the spatial extent of subglacial pressurization.
    • Subglacial Discharge Reflux and Buoyancy Forcing Drive Seasonality in a Silled Glacial Fjord

      Hager, Alexander O.; Sutherland, David A.; Amundson, Jason M.; Jackson, Rebecca H.; Kienholz, Christian; Motyka, Roman J.; Nash, Jonathan D. (American Geophysical Union, 2022-04-19)
      Fjords are conduits for heat and mass exchange between tidewater glaciers and the coastal ocean, and thus regulate near-glacier water properties and submarine melting of glaciers. Entrainment into subglacial discharge plumes is a primary driver of seasonal glacial fjord circulation; however, outflowing plumes may continue to influence circulation after reaching neutral buoyancy through the sill-driven mixing and recycling, or reflux, of glacial freshwater. Despite its importance in non-glacial fjords, no framework exists for how freshwater reflux may affect circulation in glacial fjords, where strong buoyancy forcing is also present. Here, we pair a suite of hydrographic observations measured throughout 2016–2017 in LeConte Bay, Alaska, with a three-dimensional numerical model of the fjord to quantify sill-driven reflux of glacial freshwater, and determine its influence on glacial fjord circulation. When paired with subglacial discharge plume-driven buoyancy forcing, sill-generated mixing drives distinct seasonal circulation regimes that differ greatly in their ability to transport heat to the glacier terminus. During the summer, 53%–72% of the surface outflow is refluxed at the fjord's shallow entrance sill and is subsequently re-entrained into the subglacial discharge plume at the fjord head. As a result, near-terminus water properties are heavily influenced by mixing at the entrance sill, and circulation is altered to draw warm, modified external surface water to the glacier grounding line at 200 m depth. This circulatory cell does not exist in the winter when freshwater reflux is minimal. Similar seasonal behavior may exist at other glacial fjords throughout Southeast Alaska, Patagonia, Greenland, and elsewhere.
    • Risks of mining to salmonid-bearing watersheds

      Sergeant, Christopher, A.; Sexton, Erin K.; Moore, Jonathan W.; Westwood, Alana R.; Nagorski, Sonia; Ebersole, Joseph L.; Chambers, David M.; O'Neal, Sarah L.; Malison, Rachel L.; Hauer, F. Richard; et al. (American Association for the Advancement of Science, 2022-07-01)
      Mining provides resources for people but can pose risks to ecosystems that support cultural keystone species. Our synthesis reviews relevant aspects of mining operations, describes the ecology of salmonid-bearing watersheds in northwestern North America, and compiles the impacts of metal and coal extraction on salmonids and their habitat. We conservatively estimate that this region encompasses nearly 4000 past producing mines, with present-day operations ranging from small placer sites to massive open-pit projects that annually mine more than 118 million metric tons of earth. Despite impact assessments that are intended to evaluate risk and inform mitigation, mines continue to harm salmonid-bearing watersheds via pathways such as toxic contaminants, stream channel burial, and flow regime alteration. To better maintain watershed processes that benefit salmonids, we highlight key windows during the mining governance life cycle for science to guide policy by more accurately accounting for stressor complexity, cumulative effects, and future environmental change.
    • Evolution of marine organisms under climate change at different levels of biological organisation.

      Harvey, Ben P.; Al-Janabi, Balsam; Broszeit, Stefanie; Cioffi, Rebekah; Kumar, Amit; Aranguren-Gassi, Maria; Bailey, Allison; Green, Leon; Gsottbauer, Carina M.; Hall, Emilie F.; et al. (Multidisciplinary Digital Publishing Institute, 2014)
      Research to date has suggested that both individual marine species and ecological processes are expected to exhibit diverse responses to the environmental effects of climate change. Evolutionary responses can occur on rapid (ecological) timescales, and yet studies typically do not consider the role that adaptive evolution will play in modulating biological responses to climate change. Investigations into such responses have typically been focused at particular biological levels (e.g., cellular, population, community), often lacking interactions among levels. Since all levels of biological organisation are sensitive to global climate change, there is a need to elucidate how different processes and hierarchical interactions will influence species fitness. Therefore, predicting the responses of communities and populations to global change will require multidisciplinary efforts across multiple levels of hierarchy, from the genetic and cellular to communities and ecosystems. Eventually, this may allow us to establish the role that acclimatisation and adaptation will play in determining marine community structures in future scenarios.
    • Seawater acidification more than warming presents a challenge for two Antarctic macroalgal-associated amphipods

      Schram, Julie B.; Schoenrock, Kathryn M.; McClintock, James B.; Amsler, Charles D.; Angus, Robert A. (Inter-Research, 2016-07-08)
      Elevated atmospheric pCO2 concentrations are triggering seawater pH reductions and seawater temperature increases along the western Antarctic Peninsula (WAP). These factors in combination have the potential to influence organisms in an antagonistic, additive, or synergistic manner. The amphipods Gondogeneia antarctica and Paradexamine fissicauda represent prominent members of macroalgal-associated mesograzer assemblages of the WAP. Our primary objective was to investigate amphipod behavioral and physiological responses to reduced seawater pH and elevated temperature to evaluate potential cascading ecological impacts. For 90 d, amphipods were exposed to combinations of seawater conditions based on present ambient (pH 8.0, 1.5°C) and predicted end-of-century conditions (pH 7.6, 3.5°C). We recorded survival, molt frequency, and macroalgal consumption rates as well as change in wet mass and proximate body composition (protein and lipid). Survival for both species declined significantly at reduced pH and co-varied with molt frequency. Consumption rates in G. antarctica were significantly higher at reduced pH and there was an additive pH−temperature effect on consumption rates in P. fissicauda. Body mass was reduced for G. antarctica at elevated temperature, but there was no significant effect of pH or temperature on body mass in P. fissicauda. Exposure to the pH or temperature levels tested did not induce significant changes in whole body biochemical composition of G. antarctica, but exposure to elevated temperature resulted in a significant increase in whole body protein content of P. fissicauda. Our study indicates that while elevated temperature causes sub-lethal impacts on both species of amphipods, reduced pH causes significant mortality.