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  • Biologically important areas II for cetaceans within U.S. and adjacent waters - Gulf of Alaska Region

    Wild, Lauren A.; Riley, Heather; Pearson, Heidi C.; Gabriele, Christine M.; Neilson, Janet L.; Szabo, Andy; Moran, John; Straley, Janice M.; DeLand, Sarah (Frontiers Media S. A., 2023-05-05)
    We delineated and scored Biologically Important Areas (BIAs) for cetacean species in the Gulf of Alaska region. BIAs represent areas and times in which cetaceans are known to concentrate for activities related to reproduction, feeding, and migration, and also the known ranges of small and resident populations. This National Oceanic and Atmospheric Association (NOAA)-led effort uses structured expert elicitation principles to build upon the first version of NOAA’s BIAs for cetaceans. Supporting evidence for these BIAs came from aerial-, land-, and vessel-based surveys; satellite-tagging data; passive acoustic monitoring; Indigenous knowledge; photo-identification data; and/or prey studies. A total of 20 BIAs were identified, delineated, and scored for six species: beluga whale (Delphinapterus leucas), fin whale (Balaenoptera physalus), gray whale (Eschrichtius robustus), humpback whale (Megaptera novaeangliae), North Pacific right whale (Eubalaena japonica), and sperm whale (Physeter macrocephalus). Of the 20 total BIAs, there were two small and resident populations, one migratory, and 17 feeding areas; no reproductive BIAs were identified. An additional five watch list areas were identified, a new feature to the second version of BIAs. In addition to more comprehensive narratives and maps, the BIA II products improve upon the first version by creating metadata tables and incorporating a scoring and labeling system which improves quantification and standardization of BIAs within and across regions. BIAs are compilations of the best available science and have no inherent regulatory authority. They have been used by NOAA, other federal agencies, and the public to support planning and marine mammal impact assessments, and to inform the development of conservation measures for cetaceans.
  • Internal gravity waves generated by subglacial discharge: Implications for tidewater glacier melt

    Cusack, J. M.; Jackson, R. H.; Nash, J. D.; Skyllingstad, E.; Pettit, E. C.; Sutherland, D. A.; Motyka, Roman J.; Amundson, J. M. (American Geophysical Union, 2023-06-13)
    Submarine melting has been implicated in the accelerated retreat of marine-terminating glaciers globally. Energetic ocean flows, such as subglacial discharge plumes, are known to enhance submarine melting in their immediate vicinity. Using observations and a large eddy simulation, we demonstrate that discharge plumes emit high-frequency internal gravity waves that propagate along glacier termini and transfer energy to distant regions of the terminus. Our analysis of wave characteristics and their correlation with subglacial discharge forcing suggest that they derive their energy from turbulent motions within the discharge plume and its surface outflow. Accounting for the near-terminus velocities associated with these waves increases predicted melt rates by up to 70%. This may help to explain known discrepancies between observed melt rates and theoretical predictions. Because the dynamical ingredients—a buoyant plume rising through a stratified ocean—are common to many tidewater glacier systems, such internal waves are likely to be widespread.
  • Alternative life-history strategy contributions to effective population size in a naturally spawning salmon population

    King, Erika M.; McPhee, Megan V.; Vulstek, Scott C.; Cunningham, Curry; Russell, Joshua R.; Tallmon, David (John Wiley & Sons, Inc., 2023-07-14)
    Alternative life-history tactics are predicted to affect within-population genetic processes but have received little attention. For example, the impact of precocious males on effective population size (Ne) has not been quantified directly in Pacific salmon Oncorhynchus spp., even though they can make up a large percentage of the total male spawners. We investigated the contribution of precocial males (“jacks”) to Ne in a naturally spawning population of Coho Salmon O. kisutch from the Auke Creek watershed in Juneau, Alaska. Mature adults that returned from 2009 to 2019 (~8000 individuals) were genotyped at 259 single-nucleotide polymorphism (SNP) loci for parentage analysis. We used demographic and genetic methods to estimate the effective number of breeders per year (Nb). Jack contribution to Nb was assessed by comparing values of Nb calculated with and without jacks and their offspring. Over a range of Nb values (108–406), the average jack contribution to Nb from 2009 to 2015 was 12.9% (SE = 3.8%). Jacks consistently made up over 20% of the total male spawners. The presence of jacks did not seem to influence Nb/N. The linkage disequilibrium Ne estimate was lower than the demographic estimate, possibly due to immigration effects on population genetic processes: based on external marks and parentage data, we estimated that immigrant spawners produced 4.5% of all returning offspring. Our results demonstrate that jacks can influence Nb and Ne and can make a substantial contribution to population dynamics and conservation of threatened stocks.
  • Reproductive success of jack and full-size males in a wild coho salmon population

    King, Erika M.; Tallmon, David; Vulstek, Scott C.; Russell, Joshua R.; McPhee, Megan V. (The Royal Society, 2023-04-05)
    Despite the wealth of research on Pacific salmon Oncorhynchus spp. life histories there is limited understanding of the lifetime reproductive success of males that spend less time at sea and mature at a smaller size (jacks) than full-size males. Over half of returning male spawners can be jacks in some populations, so it is crucial to understand their contribution to population productivity. We quantified adult-to-adult reproductive success (RS) of jacks and their relative reproductive success (RRS) compared to full-size males in a wild population of coho salmon in the Auke Creek watershed, Juneau, Alaska. We used genetic data from nearly all individuals (approx. 8000) returning to spawn over a decade (2009–2019) to conduct parentage analysis and calculate individual RS. The average adult-to-adult RS of jacks (mean = 0.7 and s.e. = 0.1) was less than that of full-size males (mean = 1.1 and s.e. = 0.1). Jack RRS was consistently below 1.0 but ranged widely (0.23 to 0.96). Despite their lower average success, jacks contributed substantially to the population by siring 23% of the total returning adult offspring (1033 of 4456) produced between 2009 and 2015. Our results imply that jacks can affect evolutionary and population dynamics, and are relevant to the conservation and management of Pacific salmon.
  • Strong correlations of sea ice cover with macroalgal cover along the Antarctic Peninsula: Ramifications for present and future benthic communities

    Amsler, Charles D.; Amsler, Margaret O.; Klein, Andrew; Galloway, Aaron W. E.; Iken, Katrin; McClintock, James B.; Heiser, Sabrina; Lowe, Alex T.; Schram, Julie; Whippo, Ross (University of California Press, 2023-11)
    Macroalgal forests dominate shallow hard bottom areas along the northern portion of the Western Antarctic Peninsula (WAP). Macroalgal biomass and diversity are known to be dramatically lower in the southern WAP and at similar latitudes around Antarctica, but few reports detail the distributions of macroalgae or associated macroinvertebrates in the central WAP. We used satellite imagery to identify 14 sites differing in sea ice coverage but similar in terms of turbidity along the central WAP. Fleshy macroalgal cover was strongly, negatively correlated with ice concentration, but there was no significant correlation between macroinvertebrate cover and sea ice. Overall community (all organisms) diversity correlated negatively with sea ice concentration and positively with fleshy macroalgal cover, which ranged from around zero at high ice sites to 80% at the lowest ice sites. Nonparametric, multivariate analyses resulted in clustering of macroalgal assemblages across most of the northern sites of the study area, although they differed greatly with respect to macroalgal percent cover and diversity. Analyses of the overall communities resulted in three site clusters corresponding to high, medium, and low fleshy macroalgal cover. At most northern sites, macroalgal cover was similar across depths, but macroalgal and macroinvertebrate distributions suggested increasing effects of ice scour in shallower depths towards the south. Hindcast projections based on correlations of ice and macroalgal cover data suggest that macroalgal cover at many sites could have been varying substantially over the past 40 years. Similarly, based on predicted likely sea ice decreases by 2100, projected increases in macroalgal cover at sites that currently have high ice cover and low macroalgal cover are substantial, often with only a future 15% decrease in sea ice. Such changes would have important ramifications to future benthic communities and to understanding how Antarctic macroalgae may contribute to future blue carbon sequestration.
  • A tropical cocktail of organic matter sources: Variability in supraglacial and glacier outflow dissolved organic matter composition and age across the Ecuadorian Andes

    Holt, Amy D.; Kellerman, Anne M.; Battin, Tom I.; McKenna, Amy M.; Hood, Eran; Andino, Patricio; Crespo-Perez, Veronica; Peter, Hannes; Schon, Martina; De Staercke, Vincent; et al. (American Geophysical Union, 2023-05-09)
    The biogeochemistry of rapidly retreating Andean glaciers is poorly understood, and Ecuadorian glacier dissolved organic matter (DOM) composition is unknown. This study examined molecular composition and carbon isotopes of DOM from supraglacial and outflow streams (n = 5 and 14, respectively) across five ice capped volcanoes in Ecuador. Compositional metrics were paired with streamwater isotope analyses (δ18O) to assess if outflow DOM composition was associated with regional precipitation gradients and thus an atmospheric origin of glacier DOM. Ecuadorian glacier outflows exported ancient, biolabile dissolved organic carbon (DOC), and DOM contained a high relative abundance (RA) of aliphatic and peptide-like compounds (≥27%RA). Outflows were consistently more depleted in Δ14C-DOC (i.e., older) compared to supraglacial streams (mean −195.2 and −61.3‰ respectively), perhaps due to integration of spatially heterogenous and variably aged DOM pools across the supraglacial environment, or incorporation of aged subglacial OM as runoff was routed to the outflow. Across Ecuador, Δ14C-DOC enrichment was associated with decreased aromaticity of DOM, due to increased contributions of organic matter (OM) from microbial processes or atmospheric deposition of recently fixed and subsequently degraded OM (e.g., biomass burning byproducts). There was a regional gradient between glacier outflow DOM composition and streamwater δ18O, suggesting covariation between regional precipitation gradients and the DOM exported from glacier outflows. Ultimately, this highlights that atmospheric deposition may exert a control on glacier outflow DOM composition, suggesting regional air circulation patterns and precipitation sources in part determine the origins and quality of OM exported from glacier environments.
  • Tree-ring derived avalanche frequency and climate associations in a high-latitude, maritime climate

    Peitzsch, Erich H.; Hood, Eran; Harley, John R.; Stahle, D. K.; Kichas, Nickolas E.; Wolken, Gabriel (American Geophysical Union, 2023-07-28)
    Snow avalanches are a natural hazard in mountainous areas worldwide with severe impacts that include fatalities, damage to infrastructure, disruption to commerce, and landscape disturbance. Understanding long-term avalanche frequency patterns, and associated climate and weather influences, improves our understanding of how climate change may affect avalanche activity. We used dendrochronological techniques to evaluate the historical frequency of large magnitude avalanches (LMAs) in the high-latitude climate of southeast Alaska, United States. We collected 434 cross sections throughout six avalanche paths near Juneau, Alaska. This resulted in 2706 identified avalanche growth disturbances between 1720 and 2018, which allowed us to reconstruct 82 years with LMA activity across three sub-regions. By combining this tree-ring-derived avalanche data set with a suite of climate and atmospheric variables and applying a generalized linear model to fit a binomial regression, we found that February and March precipitation and the Oceanic Niño Index (ONI) were significant predictors of LMA activity in the study area. Specifically, LMA activity occurred during winters with substantial February and March precipitation and neutral or negative (cold) ONI values, while years not characterized by LMAs occur more frequently during warm winters (positive ONI values). Our examination of the climate-avalanche relationship in southeast Alaska sheds light on important climate variables and physical processes associated with LMA years. These results can be used to inform long-term infrastructure planning and avalanche mitigation operations in an urban area, such as Juneau, where critical infrastructure is subject to substantial avalanche hazard.
  • Small, coastal temperate rainforest watersheds dominate dissolved organic carbon transport to the Northeast Pacific Ocean

    McNicol, Gavin; Hood, Eran; Butman, David E.; Tank, Suzanne; Giesbrecht, Ian J. W.; Floyd, William; D'Amore, D.; Fellman, Jason; Cebulski, Alex; Lally, A.; et al. (American Geophysical Union, 2023-06-26)
    The northeast Pacific Coastal Temperate Rainforest (NPCTR) extending from southeast Alaska to northern California is characterized by high precipitation and large stores of recently fixed biological carbon. We show that 3.5 Tg-C yr−1 as dissolved organic carbon (DOC) is exported from the NPCTR drainage basin to the coastal ocean. More than 56% of this riverine DOC flux originates from thousands of small (mean = 118 km2), coastal watersheds comprising 22% of the NPCTR drainage basin. The average DOC yield from NPCTR coastal watersheds (6.20 g-C m−2 yr−1) exceeds that from Earth's tropical regions by roughly a factor of three. The highest yields occur in small, coastal watersheds in the central NPCTR due to the balance of moderate temperature, high precipitation, and high soil organic carbon stocks. These findings indicate DOC export from NPCTR watersheds may play an important role in regional-scale heterotrophy within near-shore marine ecosystems in the northeast Pacific.
  • Stream hydrology and a pulse subsidy shape patterns of fish foraging

    Fitzgerald, Kevin A.; Bellmore, J. Ryan; Fellman, Jason; Cheng, Matthew L. H.; Delbecq, Claire E.; Falke, Jeffery A. (British Ecological Society, 2023-10-30)
    1. Pulsed subsidy events create ephemeral fluxes of hyper-abundant resources that can shape annual patterns of consumption and growth for recipient consumers. However, environmental conditions strongly affect local resource availability for much of the year, and can heavily impact consumer foraging and growth patterns prior to pulsed subsidy events. Thus, a consumer's capacity to exploit pulse subsidy resources may be influenced by antecedent environmental conditions, but this has rarely been shown in nature and is unknown in aquatic ecosystems. 2. Here, we sought to understand the importance of hydrologic variation and a salmon pulse subsidy on the foraging and growth patterns of two stream salmonids in a coastal southeast Alaska drainage. 3. To do this, we sampled fish stomach contents at a high temporal frequency (daily–weekly measurements) and analyzed fish consumption rates in relation to streamflow and pulse subsidy resource availability. We then explored the influence of interannual hydrologic variation on access to pulse subsidy resources (i.e. whether fish exceeded an egg consumption gape limit) in a bioenergetic simulation. 4. Prior to Pink Salmon spawning, Dolly Varden and Coho Salmon displayed distinct and nonlinear flow-foraging relationships, where forage for both species consisted primarily of macroinvertebrates. During this time period, consumption maxima coincided with baseflow and the highest observed flow conditions, and consumption minima were observed at severe low-water and intermediate flow values. After salmon spawning began, forage was not significantly related to flow and consisted primarily of salmon eggs. Further, consumption rates increased overall, and foraging patterns did not appear to be affected by flow in either species. Bioenergetic simulations revealed that patterns of interannual hydrologic variation may shift Coho Salmon growth trajectories among years. 5. Together, our results suggest that access to marine pulse subsidy resources may depend on whether antecedent hydrologic conditions are suitable for juvenile salmonids to grow large enough to consume salmon eggs by the onset of spawning.
  • The role of glacier erosion in riverine particulate organic carbon export

    Behnke, Megan; Fellman, Jason B.; Nagorski, Sonia; Spencer, Robert G. M.; Hood, Eran (American Geophysical Union, 2023-11-01)
    Biospheric particulate organic carbon (POCbio) burial and rock petrogenic particulate organic carbon (POCpetro) oxidation are opposing long-term controls on the global carbon cycle, sequestering and releasing carbon, respectively. Here, we examine how watershed glacierization impacts the POC source by assessing the concentration and isotopic composition (δ13C and Δ14C) of POC exported from four watersheds with 0%–49% glacier coverage across a melt season in Southeast Alaska. We used two mixing models (age-weight percent and dual carbon isotope) to calculate concentrations of POCbio and POCpetro within the bulk POC pool. The fraction POCpetro contribution was highest in the heavily glacierized watershed (age-weight percent: 0.39 ± 0.05; dual isotope: 0.42 (0.37–0.47)), demonstrating a glacial source of POCpetro to fjords. POCpetro was mobilized via glacier melt and subglacial flow, while POCbio was largely flushed from the non-glacierized landscape by rain. Flow normalized POCbio concentrations exceeded POCpetro concentrations for all streams, but surprisingly were highest in the heavily glacierized watershed (mean: 0.70 mgL−1; range 0.16–1.41 mgL−1), suggesting that glacier rivers can contribute substantial POCbio to coastal waters. Further, the most heavily glacierized watershed had the highest sediment concentration (207 mgL−1; 7–708 mgL−1), and thus may facilitate long-term POCbio protection via sediment burial in glacier-dominated fjords. Our results suggest that continuing glacial retreat will decrease POC concentrations and increase POCbio:POCpetro exported from currently glacierized watersheds. Glacier retreat may thus decrease carbon storage in marine sediments and provide a positive feedback mechanism to climate change that is sensitive to future changes in POCpetro oxidation.
  • Trees in the stream: Determining patterns of terrestrial dissolved organic matter contributions to the Northeast Pacific Coastal Temperate Rainforest

    Behnke, Megan; Fellman, Jason B.; D'Amore, David V.; Spencer, Robert G. M. (American Geophysical Union, 2023-04-10)
    Dissolved organic matter (DOM) composition in small watersheds depends on complex antecedent conditions that ultimately influence DOM generation, processing, and stability downstream. Here, we used ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry and total dissolved nitrogen and dissolved organic carbon concentrations to investigate how DOM is produced in distinct sub-catchment types (poor fen, forested wetland, and upland forest) and transported through a watershed in the northeast Pacific coastal temperate rainforest (NPCTR). We traced a suite of previously identified source-specific marker formulae from vegetation and soil downstream and used them to test models of terrestrial DOM inputs. Marker formulae escaped microbial degradation and were exported from the watershed, demonstrating strong land-to-ocean connectivity through the transfer of unmodified tree DOM from specific tree species into the marine environment. Simple hydrologic and temperature variables were better able to predict inputs of soil-sourced DOM into the stream network than tree-sourced DOM, highlighting the role of antecedent conditions (e.g., plant growth stage) in DOM source availability and hydrologic flow connectivity, particularly for plant-derived material. Forested wetland pore waters featured thousands of nitrogen-containing molecular formulae that potentially provide a path of direct organic nitrogen uptake to organisms. The modified aromaticity index peaked in midsummer (up to 0.55 for fen headwaters) suggesting DOM inputs from freshly produced vegetation provide a strong summertime terrestrial signal. As the climate changes, new watershed-scale conditions may further complicate predictions of DOM source availability, flow connectivity, and downstream fate in NPCTR watersheds.
  • Parity of polynomial multiplier sequences for the Chebyshev basis.

    Piotrowski, Andrzej; Shterenberg, Joshua (2023)
  • A collaborative and near-comprehensive North Pacific humpback whale photo-ID dataset

    Cheeseman, T.; Southerland, Ken; Acebes, Jo Marie; Audley, Katherina; Barlow, Jay; Bejder, Lars; Birdsall, Caitlin; Bradford, Amanda L.; Byington, Josie K.; Calambokidis, John; et al. (Springer Nature Limited, 2023-06-23)
    We present an ocean‑basin‑scale dataset that includes tail fluke photographic identification (photo‑ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo‑ID catalogs, supplemented with community science data. Data from throughout the North Pacific were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre‑processing using a recently developed image recognition algorithm based on machine learning through artificial intelligence; this system is capable of rapidly detecting matches between individuals with an estimated 97–99% accuracy. For the 2001–2021 study period, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average of 87% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin‑wide studies of a keystone marine mammal in a time of rapid ecological change.
  • Impact of the 2014–2016 marine heatwave on US and Canada West Coast fisheries: Surprises and lessons from key case studies

    Free, Christopher M.; Anderson, Sean C.; Hellmers, Elizabeth A.; Muhling, Barbara A.; Navarro, M.O.; Richerson, Kate; Rogers, Lauren A.; Satterthwaite, William H.; Thompson, Andrew R.; Burt, Jenn M.; et al. (Wiley, 2023-04-04)
    Marine heatwaves are increasingly affecting marine ecosystems, with cascading impacts on coastal economies, communities, and food systems. Studies of heatwaves provide crucial insights into potential ecosystem shifts under future climate change and put fisheries social-ecological systems through “stress tests” that expose both vulnerabilities and resilience. The 2014–16 Northeast Pacific heatwave was the strongest and longest marine heatwave on record and resulted in profound ecological changes that impacted fisheries, fisheries management, and human livelihoods. Here, we synthesize the impacts of the 2014–2016 marine heatwave on US and Canada West Coast fisheries and extract key lessons for preparing global fisheries science, management, and industries for the future. We set the stage with a brief review of the impacts of the heatwave on marine ecosystems and the first systematic analysis of the economic impacts of these changes on commercial and recreational fisheries. We then examine ten key case studies that provide instructive examples of the complex and surprising challenges that heatwaves pose to fisheries social-ecological systems. These reveal important insights into improving the resilience of monitoring and management and increasing adaptive capacity to future stressors. Key recommendations include: (1) expanding monitoring to enhance mechanistic understanding, provide early warning signals, and improve predictions of impacts; (2) increasing the flexibility, adaptiveness, and inclusiveness of management where possible; (3) using simulation testing to help guide management decisions; and (4) enhancing the adaptive capacity of fishing communities by promoting engagement, flexibility, experimentation, and failsafes. These advancements are important as global fisheries prepare for a changing ocean
  • A collaborative and near‑comprehensive North Pacifc humpback whale photo‑ID dataset

    Cheeseman, T.; Southerland, Ken; Acebes, Jo Marie; Audley, Katherina; Barlow, Jay; Bejder, Lars; Birdsall, Caitlin; Bradford, Amanda L.; Byington, Josie K.; Calambokidis, John; et al. (Springer Nature Limited, 2023-06-23)
    We present an ocean-basin-scale dataset that includes tail fuke photographic identifcation (photo-ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacifc Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs, supplemented with community science data. Data from throughout the North Pacifc were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre-processing using a recently developed image recognition algorithm based on machine learning through artifcial intelligence; this system is capable of rapidly detecting matches between individuals with an estimated 97–99% accuracy. For the 2001–2021 study period, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average of 87% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin-wide studies of a keystone marine mammal in a time of rapid ecological change.
  • Juneau, Alaska’s Successful Response to COVID-19: A Case Study of Adaptive Leadership in a Complex System

    Powell, James E.; Orttung, Robert W.; Topkok, Sean Asiqłuq; Akselrod, Hana; Little, Joseph; Wilcox, Peggy (Sage, 2022)
    Juneau, Alaska, kept COVID-19 deaths lower than in other similar jurisdictions. We argue that adaptive leadership—the early decisions and actions of Juneau’s leaders, effective communications, and emergent new collaborative structures—in the context of municipal ownership of key assets enabled Juneau’s success. The result of 61 interviews and follow-up research, this case study contributes a better understanding of which institutional design, communication, and collaborative factors mattered in responding to the pandemic. Adaptive leadership provides a better explanation for Juneau’s success than alternatives that focus on its isolation, home-rule status, and socio-economic structure.
  • A new conceptual framework for the transformation of groundwater dissolved organic matter

    McDonough, Liza K.; Andersen, Martin S.; Behnke, Megan; Rutlidge, Helen; Oudone, Phetdala; Meredith, Karina; O’Carrol, Denis M.; Santos, Isaac R.; Marjo, Christopher E.; Spencer, Robert G. M.; et al. (Nature Communications, 2022-04-20)
    Groundwater comprises 95% of the liquid fresh water on Earth and contains a diverse mix of dissolved organic matter (DOM) molecules which play a significant role in the global carbon cycle. Currently, the storage times and degradation pathways of groundwater DOM are unclear, preventing an accurate estimate of groundwater carbon sources and sinks for global carbon budgets. Here we reveal the transformations of DOM in aging groundwater using ultra-high resolution mass spectrometry combined with radiocarbon dating. Long-term anoxia and a lack of photodegradation leads to the removal of oxidised DOM and a build-up of both reduced photodegradable formulae and aerobically biolabile formulae with a strong microbial signal. This contrasts with the degradation pathway of DOM in oxic marine, river, and lake systems. Our findings suggest that processes such as groundwater extraction and subterranean groundwater discharge to oceans could result in up to 13 Tg of highly photolabile and aerobically biolabile groundwater dissolved organic carbon released to surface environments per year, where it can be rapidly degraded. These findings highlight the importance of considering groundwater DOM in global carbon budgets.
  • Effects of spatially heterogeneous lakeside development on nearshore biotic communities in a large, deep, oligotrophic lake

    Meyer, Michael F.; Ozersky, Ted; Woo, Kara H.; Shchapov, Kirill; Galloway, Aaron W. E.; Schram, Julie B.; Rosi, Emma J.; Snow, Daniel D.; Timofeyev, Maxim A.; Karnaukhov, Dmitry Yu.; et al. (Association for the Sciences of Limnology and Oceanography, 2022)
    Sewage released from lakeside development can reshape ecological communities. Nearshore periphyton can rapidly assimilate sewage-associated nutrients, leading to increases of filamentous algal abundance, thus altering both food abundance and quality for grazers. In Lake Baikal, a large, ultra-oligotrophic, remote lake in Siberia, filamentous algal abundance has increased near lakeside developments, and localized sewage input is the suspected cause. These shifts are of particular interest in Lake Baikal, where endemic littoral biodiversity is high, lakeside settlements are mostly small, tourism is relatively high ( 1.2 million visitors annually), and settlements are separated by large tracts of undisturbed shoreline, enabling investigation of heterogeneity and gradients of disturbance. We surveyed sites along 40 km of Baikal’s southwestern shore for sewage indicators—pharmaceuticals and personal care products (PPCPs) and microplastics—as well as periphyton and macroinvertebrate abundance and indicators of food web structure (stable isotopes and fatty acids). Summed PPCP concentrations were spatially related to lakeside development. As predicted, lakeside development was associated with more filamentous algae and lower abundance of sewage-sensitive mollusks. Periphyton and macroinvertebrate stable isotopes and essential fatty acids suggested that food web structure otherwise remained similar across sites; yet, the invariance of amphipod fatty acid composition, relative to periphyton, suggested that grazers adjust behavior or metabolism to compensate for different periphyton assemblages. Our results demonstrate that even low levels of human disturbance can result in spatial heterogeneity of nearshore ecological responses, with potential for changing trophic interactions that propagate through the food web.
  • 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

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