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Item Terrestrial Organic Matter Contributes to CO2 Production From Siberian Shelf Sediments(Journal of Geophysical Research: Biogeosciences, 2025-01-01) Sauerland, Lewis; Ray, Nicholas; Martens, Jannik; Tesi, Tommaso; Dudarev, Oleg; Gustafsson, Örjan; Semiletov, Igor; Wild, BirgitArctic climate warming is causing permafrost thaw and erosion, which may lead to enhanced inputs of terrestrial organic matter into Arctic Ocean shelf sediments. Degradation of terrestrial organic matter in sediments might contribute to carbon dioxide production and bottom water acidification. Yet, the degradability of organic matter in shallow Arctic Ocean sediments, as well as the contribution of terrestrial input, is poorly quantified. Here, potential organic matter degradation rates were investigated for 16 surface sediments from the Kara Sea, Laptev Sea, and the western East Siberian Sea and compared with physicochemical sediment properties including molecular biomarkers, stable and radioactive carbon isotopes, and grain size. Aerobic oxygen and carbon dioxide fluxes, measured in laboratory incubations of sediment slurry, showed high spatial variability and correlated significantly with organic carbon content as well as with the amount and degradation state of terrestrial organic matter. The dependency on terrestrial organic matter declined with increasing distance from land, indicating that the presence of terrestrial organic matter is likely a constraining factor for organic matter degradation in shallow shelf seas. However, sediment oxygen consumption rates, measured in incubations of intact sediment cores, also exhibited substantial spatial variability but were not related to organic carbon content or terrestrial influence. Oxygen consumption of intact sediments may be more strongly influenced by in situ redox conditions. Together with previous observations, our findings support that terrestrial organic matter is easily degradable in shelf sea sediments and might substantially contribute to aerobic carbon dioxide production and oxygen consumption. Plain Language Summary The Arctic climate is warming rapidly, which is leading to thawing of frozen deposits on land. These deposits contain large amounts of terrestrial organic matter that is being eroded and deposited into shallow ocean sediments. The breakdown of terrestrial organic matter in sediments might contribute to carbon dioxide release into the ocean water. There is insufficient knowledge on how fast this breakdown is happening and which parameters influence it. We investigated organic matter breakdown rates for sediment samples taken from shallow Siberian seas and compared them with sediment properties. Oxygen consumption and carbon dioxide release were measured in laboratory experiments and showed high variability between different samples. The release was related to the amount of terrestrial organic matter and its state of decomposition. This relationship decreased strongly for sediments further away from land. During a second incubation experiment, using intact sediment cores, oxygen consumption rates were measured and also showed high variability between samples. Oxygen consumption rates were not related to organic matter content. These findings support previous observations that terrestrial organic matter breaks down rapidly in shallow Arctic Ocean sediments and might also substantially contribute to the release of carbon dioxide and consumption of oxygen from the seawater. Key Points - Carbon dioxide fluxes from sediment slurry incubations showed high variability and were dependent on the input of terrestrial organic matter - Pronounced variability in oxygen consumption of intact sediment cores could not be explained by the input of terrestrial organic matterItem Kiska Alaska’s Underwater Battlefield: An Exploration of World War II-era Submerged Archaeological Sites(International Journal of Nautical Archaeology, 2024-11-26) Pietruszka, Andrew T.; Batchelor, Heidi; Breece, Mathew; Colbourn, Colin; Hess, Bob; Gallimore, Eric; Moline, Mark A.; Nager, Andy; White, Erik; Terrill, Eric J.This article details an exploratory remote-sensing survey to identify and document World War II-era submerged archaeological sites around Kiska Island, Alaska, underscoring their historical significance. The survey included 35 km2 of sidescan sonar coverage and 46 km2 of ship-based multibeam sonar survey. Data from the project provides a comprehensive inventory of submerged cultural resources associated with the Kiska Island National Historic Landmark. The plethora of World War II-era sites shows a rich, well-preserved maritime landscape akin to what has previously been noted in terrestrial surveys of the island. RESUMEN Este artículo detalla un estudio exploratorio mediante sensores remotos para identificar y documentar sitios arqueológicos sumergidos de la época de la Segunda Guerra Mundial alrededor de la isla Kiska (Alaska), que subraya su importancia histórica. El estudio incluyó 35 km2 de cobertura con un sonar de barrido lateral y 46km2 de prospección con un sonar multihaz a bordo de una embarcación. Los datos del proyecto proporcionan un inventario exhaustivo de los recursos culturales sumergidos asociados al Hito Histórico Nacional de la Isla Kiska. La plétora de sitios de la época de la Segunda Guerra Mundial muestra un paisaje marítimo rico y bien preservado, similar a lo que ha sido observado previamente en estudios terrestres en la isla. 摘要 本文详细介绍了为确认和记录阿拉斯加基斯卡岛周围二战时期水下考古遗址而进行的遥感勘测调查结果，并着重强调了这些遗址的历史意义。此次调查包括 35 平方公里的侧扫声呐和 46 平方公里的船载多波束声呐。该项目提供了一份与基斯卡岛国家历史地标相关的水下文化资源的详实总录。大量的二战时期遗址显示出丰富的、保存完好的海洋景观，这与之前对该岛进行的陆上调查发现类似。 摘要 本文詳細介紹了為確認和記錄阿拉斯加基斯卡島周圍二戰時期水下考古遺址而進行的遙感勘測調查結果，並著重強調了這些遺址的歷史意義。此次調查包括 35 平方公裏的側掃聲呐和 46 平方公裏的船載多波束聲呐。該項目提供了一份與基斯卡島國家歷史地標相關的水下文化資源的詳實總錄。大量的二戰時期遺址顯示出豐富的、保存完好的海洋景觀，這與之前對該島進行的陸上調查發現類似。 المُستخلص تتناول هذه المقالة تفاصيل المسح الاستكشافي بالاستشعار عن بعد لتحديد وتوثيق المواقع الأثرية المغمورة بالمياه في حقبة الحرب العالمية الثانية حول جزيرة كيسكا بألاسكا، مؤكداً علي أهميتها التاريخية. ولقد شَمل المسح ٣٥ كيلومتراً مربعاً باستخدام السونار الجانبي و٤٦ كيلومتراً مربعاً من مسح قائم على السُفن باستخدام السونار مُتعدد الحزم. وتوفر بيانات المشروع مَخزوناً شاملاً للموارد الثقافية المغمورة المرتبطة بالمعلم التاريخي الوطني لجزيرة كيسكا. هذا إلي جانب أن وفرة المواقع التي تعود إلى حقبة الحرب العالمية الثانية تُظهر مشهداً بحرياً غنياً ومحفوظاً جيداً يشبه ما تمت ملاحظته سابقاً في المسوحات الأرضية للجزيرة.Item Enhanced Net Community Production With Sea Ice Loss in the Western Arctic Ocean Uncovered by Machine-Learning-Based Mapping(Geophysical Research Letters, 2024-11-23) Zhou, Tianyu; Li, Yun; Ouyang, Zhangxian; Cai, Wei-Jun; Ji, RubaoIn the Arctic Ocean (AO), net community production (NCP) has displayed spatially heterogeneous responses to sea ice reduction and associated environmental changes. Using a random forest machine learning model trained with >42,000 in situ measurements and concurrent, collocated environmental predictors, we reconstructed 19 years of 8‐day, 6‐km NCP maps. During 2015–2021, the integrated NCP between late‐May and early‐September (intNCP) over the western AO was 10.95 ± 3.30 Tg C per year, with interannual variations positively tracking open water area. While the relationship between intNCP and open water area was quasi‐linear at high latitudes, strong nonlinearity was detected on the inflow shelf. The nonlinearity highlights that the intNCP increase resulted from area gain could be compounded by sea‐ice loss induced ecosystem adjustments. Additional retrospective analysis for 2003–2014 suggests a potential long‐term increase of export production and efficiency in the western AO with sea ice loss. Key Points: • A multiyear, gap‐free net community production (NCP) product was con- structed using a machine learning model for the western Arctic Ocean • Seasonally and regionally integrated NCP responded to sea ice loss quasi‐ linearly at high latitudes but non- linearly on the inflow shelf • Compared with the 2010s, carbon export production has increased in recent years, accompanying sea ice loss in the western Arctic Ocean Plain Language Summary Net community production (NCP) refers to the portion of phytoplankton production that remains unused by consumers and can be exported to the deeper part of the ocean. In the western Arctic Ocean (AO), NCP patterns are uneven due to complex interactions between the physical environment and the ecosystem. In this study, we developed a machine learning model of NCP in the western AO. The model used publicly available underway measurements and the associated environmental variables to create long‐term, high‐resolution maps of NCP. For the period of 2015–2021, we found that the integrated NCP between late‐ May and early‐September (intNCP) was 10.95 ± 3.30 Tg C per year in the western AO. intNCP varied from year to year and was higher when the open water area was larger. Notably, on the inflow shelf, intNCP increased at a faster rate than a linear relationship would suggest, due to both area expansion and ecosystem adjustments induced by sea ice loss. Our findings indicate that with long‐term sea ice loss, the western AO is likely to export more phytoplankton production to deeper ocean waters.Item Marine recreational fishery trends in total catch, catch per unit effort, and release rates in Delaware during 1981–2021(Fisheries Management and Ecology, 2024-09-25) Whaley, Nicholas; Fontana, Julia; Hicks, Matthew; Marsaly, Benjamin Paul; Smoot, Timothy; Bandlow, Serena; Carlisle, Aaron; Hale, EdwardThe impact of recreational fisheries on marine ecosystems is often overshadowed by commercial fisheries, although recreational fishing harvest can be substantial, especially for species that are either overfished or experiencing overfishing. Delaware is a small coastal state with ~1,000,000 residents and nearly 272,000 resident and non-resident anglers. We used publicly available data for Delaware's recreational fisheries during 1981–2021 to determine the nine most caught fish species and to evaluate trends in total numbers caught, harvested, released, and catch per unit effort (CPUE). The top nine most frequently captured fish by recreational anglers were Summer Flounder (Paralichthys dentatus), Atlantic Croaker (Micropogonias undulatus), Bluefish (Pomatomus saltatrix), Black Sea Bass (Centropristis striata), Weakfish (Cynoscion regalis), White Perch (Morone americana), Tautog (Tautoga onitis), Striped Bass (Morone saxatilis), and Spot (Leiostomus xanthurus). The proportion of fish released increased through time for all nine species, suggesting that the recreational fishery in Delaware is transitioning from a harvest-oriented to a catch-and-release-oriented fishery. Observations of higher release rates in recreational fisheries of Delaware are consistent with the findings elsewhere in the world for freshwater and marine systems.Item Using DIC-δ13C Pair to Constrain Anthropogenic Carbon Increase in the Southeastern Atlantic Ocean Over the Most Recent Decade (2010–2020)(Journal of Geophysical Research: Oceans, 2024-11-12) Gao, Hui; Jin, Meibing; Zhao, Hui; Hussain, Najid; Cai, Wei-JunThe southeastern Atlantic Ocean is a crucial yet understudied region for the ocean absorption of anthropogenic carbon (Canth). Data from the A12 (2020) and A13.5 (2010) cruises offer an opportunity to examine changes in dissolved inorganic carbon (DIC), its stable isotope (δ13C), and Canth over the past decade within a limited region (1∼3°E, 32∼42°S). For the decade of 2010–2020, Canth invasion was observed from the sea surface down to 1,200 m based on both DIC and δ13C data. The mean Canth increase rate (1.08 ± 0.26 mol m−2 yr−1) during this period accelerated from 0.87 ± 0.05 mol m−2 yr−1 during the previous period (1983/84–2010). The δ13C-based Canth increase closely matches the DIC-based estimation below 500 m but is 26% higher in the upper ocean. This discrepancy is likely due to δ13C's longer air-sea exchange timescale, seasonal variability in the upper ocean, and the chosen ratio of anthropogenically induced changes in δ13C and DIC. Finally, column inventory changes based on the two methods also exhibit very similar mean Canth uptake rates. The paired DIC concentration and stable isotope dataset may enhance our ability to constrain Canth accumulation and its controlling mechanisms in the ocean. Key Points - Anthropogenic carbon uptake rate estimated from δ13C matches with that from dissolved inorganic carbon except in the surface in the southeastern Atlantic Ocean - Anthropogenic carbon changes exhibit significant vertical variations depending on water masses and circulation - Anthropogenic carbon increase rate during 2010–2020 has accelerated ∼19% from that during 1983/84–2010 in the study region Plain Language Summary The stable carbon isotope signal (δ13C) of oceanic dissolved inorganic carbon (DIC) is a sensitive tracer for the absorption of anthropogenic carbon from the atmosphere. We collected δ13C data from a limited region in the southeastern Atlantic Ocean and used them to examine the anthropogenic carbon changes over the most recent decade. From 2010 to 2020, anthropogenic carbon invasion can be found from the sea surface to a depth of 1,200 m with an accelerated increase rate compared to the period from 1983/84 to 2010. The δ13C-based estimation of anthropogenic carbon increase matches closely with the DIC-based estimation below 500 m but is significantly higher in the upper ocean. This discrepancy likely arises from differences in equilibrium timescales, the ratio of the anthropogenic δ13C/DIC change, and different influences by seasonal variability in the upper ocean. Nonetheless, the entire water column inventory changes based on both two methods show very close mean anthropogenic carbon uptake rates.Item pH Distributions and Determining Processes Along the U.S. East Coast(Journal of Geophysical Research: Oceans, 2024-09-11) Li, Xinyu; Xu, Yuan-Yuan; Cai, Wei-JunpH is a key index in ocean biogeochemical and acidification research. However, there remains a limited understanding of the spatial patterns and drivers of pH across different coastal oceans. In this study, we present the distribution of spectrophotometric pHT (in total proton scale) from a synoptic summer cruise in 2018. We examine the processes controlling pHT along the U.S. East Coast, covering the South Atlantic Bight (SAB), Mid-Atlantic Bight (MAB), and Gulf of Maine (GoM). Our findings reveal a continuous low pHT band associated with the oxygen minimum and CO2 maximum zone along the slope of the entire east coast, extending from the bottom layer (∼1,000 m) in the SAB to the middle layer (300–500 m) in the MAB and GoM. We also identified unique low pHT features in each subregion, including an onshore upwelling of the low pHT slope water in the SAB, a seasonal low pHT feature on the bottom of the MAB shelf associated with the Cold Pool water, and an inflow of low pHT slope water to the bottom of the GoM. Our findings suggest that net biological production plays a prominent role in regulating sea-surface pHT, driving it away from the air-sea equilibrated pHT and mitigating the pHT decrease caused by the anthropogenic carbon dioxide (CO2) uptake. Furthermore, net biological respiration dominates the interior pHT distributions. Our analysis provides new insights and establishes a foundation for interpreting future pH changes in response to processes such as water masses shifting, ocean warming, and anthropogenic carbon uptake in coastal oceans. Key Points - The subsurface pH minimum layer extends from the slope bottom in the south to the middle layer of the slope in the north - Each subregion has a distinct low-pH feature, including onshore upwelling, Cold Pool water, and Gulf bottom water - Surface pH deviates from air-sea gas equilibrium due to net biological production, while interior ocean pH is dominated by respiration Plain Language Summary Given that pH is a crucial index for assessing ocean acidification, understanding pH distribution patterns and its controlling factors in coastal oceans is essential. This study investigates pH from a summer 2018 cruise along the entire U.S. East Coast. We found that the surface-water pH deviates from the atmospheric equilibrium, primarily due to net biological production. Subsurface pH patterns are also mainly controlled by biological factors. Along the slope, a continuous low pH band is associated with the oxygen minimum zone, extending from the bottom in the SAB to the middle depth in the MAB and GoM. On the shelf, each subregion has unique subsurface low pH features, including a shoreward upwelling of the low pH slope water in the SAB, a seasonal low pH feature in the MAB Cold Pool, and an inflow of low pH slope water in the bottom of GoM. This research provides new insights into the processes controlling pH distribution and lays a foundation for interpreting current and future pH decadal trends in the context of climate change.Item Influence of reef habitat on coral microbial associations(Environmental Microbiology Reports, 2024-11-08) Gantt, Shelby E.; Kemp, Keri M.; Colin, Patrick L.; Hoadley, Kenneth D.; LaJeunesse, Todd C.; Warner, Mark E.; Kemp, Dustin W.Corals have complex symbiotic associations that can be influenced by the environment. We compare symbiotic dinoflagellate (family: Symbiodiniaceae) associations and the microbiome of five scleractinian coral species from three different reef habitats in Palau, Micronesia. Although pH and temperature corresponded with specific host-Symbiodiniaceae associations common to the nearshore and offshore habitats, bacterial community dissimilarity analyses indicated minimal influence of these factors on microbial community membership for the corals Coelastrea aspera, Psammocora digitata, and Pachyseris rugosa. However, coral colonies sampled close to human development exhibited greater differences in microbial community diversity compared to the nearshore habitat for the coral species Coelastrea aspera, Montipora foliosa, and Pocillopora acuta, and the offshore habitat for Coelastrea aspera, while also showing less consistency in Symbiodiniaceae associations. These findings indicate the influence that habitat location has on the bacterial and Symbiodiniaceae communities comprising the coral holobiont and provide important considerations for the conservation of coral reef communities, especially for island nations with increasing human populations and development. Graphical Abstract available at: https://doi.org/10.1111/1758-2229.70051 In Palau, Micronesia, temperature and pH influence coral-Symbiodiniaceae associations but do not affect coral microbial community membership across nearshore and offshore reef habitats. Coral colonies near human development exhibited higher microbial diversity, greater bacterial community similarity across genera, and less consistent Symbiodiniaceae associations compared to both nearshore and offshore habitats. These findings reveal how habitat and proximity to urban development affect coral symbioses, offering insights for coral reef conservation as human development increases in coastal environments.Item Expanded Understanding of the Western Antarctic Peninsula Sea-Ice Environment Through Local and Regional Observations at Palmer Station(Journal of Geophysical Research: Oceans, 2024-11-07) Goodell, E.; Stammerjohn, S.; Meredith, M.; Moffat, C.; Eveleth, R.The Western Antarctic Peninsula (WAP) has been experiencing rapid regional warming since at least the 1950s, however, the impacts of this warming at the local scale are variable and nuanced. Previous studies that have linked sea-ice variability to biogeochemical cycles and food web dynamics often combine local-scale biogeochemical data with coarse-resolution regional satellite sea-ice data, which may not adequately capture local sea-ice conditions. In this study, we analyzed local-scale in situ sea-ice observations collected as part of a 28-year record (1992–2020) from the Palmer Long-Term Ecological Research site at Anvers Island, mid-WAP, in conjunction with isotopically-derived sea-ice meltwater (SIM) fractions and satellite-derived sea-ice motion and concentration, to quantify the variability and long-term trends in local sea-ice behavior. In situ sea ice observations at Palmer Station displayed higher variability than satellite observations and showed no significant declines over this time, despite region-wide declines identified in prior studies. Higher spring SIM fractions were attributed to strong northward sea-ice motion throughout the winter. Applying these local-scale sea-ice insights to similarly scaled stratification and chlorophyll-a measurements, we found that a longer-lasting, more consistent sea-ice pack led to greater water column stratification following the spring sea-ice retreat. Greater sea-ice persistence and stronger stratification led to larger peaks in chlorophyll-a, though sea-ice metrics did not explain the positive temporal trends in either stratification strength or chlorophyll-a. Through this study, we identify how local sea-ice observations and meltwater data can enhance satellite data to build an understanding of the intricate connections between ice, water column dynamics, and phytoplankton. Key Points - Local-scale sea-ice measurements at Palmer Station show higher daily and interannual variability than satellite-based measurements - Northwestward winter ice movement typically preceded elevated spring sea-ice meltwater near Palmer Station - Local sea-ice retreat influences water column stratification and Chlorophyll-a but does not explain increasing trends in these parameters Plain Language Summary The western coast of the Antarctic Peninsula is one of the fastest-warming places on the planet. The coastal ocean here is home to large amounts of marine algae (phytoplankton), which supports a rich ecosystem. Prior studies have noted that sea ice plays a role in determining how abundant phytoplankton are in the water, but these studies typically use sea-ice measurements from regional-scale satellites, which do not always provide details about how sea ice is behaving at the local scale. Here, we analyze a daily sea-ice record that was acquired locally through visual observation, as well as local-scale ocean water samples that detect how much sea-ice meltwater is present. We found that, despite regional warming, high year-to-year variability masks long-term trends in the local sea-ice record, and that the movement of sea ice during winter influences how much sea ice melts in place when it retreats in the spring. We also found that years with greater winter sea-ice coverage led to summers with more ideal conditions for phytoplankton growth (e.g., shallower and more stratified water), though sea ice does not appear to be the primary driver behind recent increases in phytoplankton.Item Genome editing in ubiquitous freshwater Actinobacteria(Applied and Environmental Microbiology, 2024-10-16) Bairagi, Nachiketa; Keffer, Jessica L.; Heydt, Jordan C.; Maresca, Julia A.Development of genome-editing tools in diverse microbial species is an important step both in understanding the roles of those microbes in different environments, and in engineering microbes for a variety of applications. Freshwater-specific clades of Actinobacteria are ubiquitous and abundant in surface freshwaters worldwide. Here, we show that Rhodoluna lacicola and Aurantimicrobium photophilum, which represent widespread clades of freshwater Actinobacteria, are naturally transformable. We also show that gene inactivation via double homologous recombination and replacement of the target gene with antibiotic selection markers can be used in both strains, making them convenient and broadly accessible model organisms for freshwater systems. We further show that in both strains, the predicted phytoene synthase is the only phytoene synthase, and its inactivation prevents the synthesis of all pigments. The tools developed here enable targeted modification of the genomes of some of the most abundant microbes in freshwater communities. These genome-editing tools will enable hypothesis testing about the genetics and (eco)physiology of freshwater Actinobacteria and broaden the available model systems for engineering freshwater microbial communities. IMPORTANCE To advance bioproduction or bioremediation in large, unsupervised environmental systems such as ponds, wastewater lagoons, or groundwater systems, it will be necessary to develop diverse genetically amenable microbial model organisms. Although we already genetically modify a few key species, tools for engineering more microbial taxa, with different natural phenotypes, will enable us to genetically engineer multispecies consortia or even complex communities. Developing genetic tools for modifying freshwater bacteria is particularly important, as wastewater, production ponds or raceways, and contaminated surface water are all freshwater systems where microbial communities are already deployed to do work, and the outputs could potentially be enhanced by genetic modifications. Here, we demonstrate that common tools for genome editing can be used to inactivate specific genes in two representatives of a very widespread, environmentally relevant group of Actinobacteria. These Actinobacteria are found in almost all tested surface freshwater environments, where they co-occur with primary producers, and genome-editing tools in these species are thus a step on the way to engineering microbial consortia in freshwater environments.Item Global fishing patterns amplify human exposures to methylmercury(Proceedings of the National Academy of Sciences, 2024-09-23) Li, Mi-Ling; Thackray, Colin P.; Lam, Vicky W. Y.; Cheung, William W. L.; Sunderland, Elsie M.Significance Methylmercury (MeHg) is a potent neurotoxicant that adversely affects human health. Wild-caught marine species sold in the global commercial seafood market are the main MeHg exposure source for many populations. Here, we identify where and how much MeHg is extracted from the ocean during global marine fisheries harvests. We find that the geographic distribution of MeHg “fished” from the oceans predominantly reflects the harvesting locations of large pelagic species. Expansion of multinational industrial fisheries, particularly in low-latitude ecosystems, has exacerbated MeHg exposures for global seafood consumers. This work reveals that most subsistence fishing populations likely exceed exposure thresholds for MeHg and highlights the disproportionate impacts of global mercury pollution on subsistence fisheries in developing countries. Abstract Global pollution has exacerbated accumulation of toxicants like methylmercury (MeHg) in seafood. Human exposure to MeHg has been associated with long-term neurodevelopmental delays and impaired cardiovascular health, while many micronutrients in seafood are beneficial to health. The largest MeHg exposure source for many general populations originates from marine fish that are harvested from the global ocean and sold in the commercial seafood market. Here, we use high-resolution catch data for global fisheries and an empirically constrained spatial model for seafood MeHg to examine the spatial origins and magnitudes of MeHg extracted from the ocean. Results suggest that tropical and subtropical fisheries account for >70% of the MeHg extracted from the ocean because they are the major fishing grounds for large pelagic fishes and the natural biogeochemistry in this region facilitates seawater MeHg production. Compounding this issue, micronutrients (selenium and omega-3 fatty acids) are lowest in seafood harvested from warm, low-latitude regions and may be further depleted by future ocean warming. Our results imply that extensive harvests of large pelagic species by industrial fisheries, particularly in the tropics, drive global public health concerns related to MeHg exposure. We estimate that 84 to 99% of subsistence fishing entities globally likely exceed MeHg exposure thresholds based on typical rates of subsistence fish consumption. Results highlight the need for both stringent controls on global pollution and better accounting for human nutrition in fishing choices.Item Testing the waters: the state of U.S. shellfish permitting regulations(Animal Frontiers, 2024-09-05) Hurley, Benjamin M.; Oremus, Kimberly L.; Birkenbach, Anna M.Implications - Permitting and regulatory hurdles are still major barriers to aquaculture expansion. - There are tradeoffs between improved regulatory efficiency/economic outcomes and environmental oversight. - Existing approaches to shellfish permitting have received mixed criticisms, but identifying an optimal approach to permitting reform requires further research. Introduction Aquaculture produces roughly half of the seafood consumed worldwide, yet in the United States, the industry remains strikingly limited relative to its potential capacity (Lester et al., 2021). At present, U.S. marine aquaculture (mariculture) consists mostly of small-scale shellfish farming within state waters, with some states boasting well-established shellfish industries and others having entered the industry in earnest only in the last decade. As states deploy a diverse range of strategies to foster and govern their nascent industries, their experiences can yield valuable insights as to how regulations can best balance industry growth with environmental protection.Item Accurately interpreting IPCC assessments—Response(Science, 2024-08-08) Kotchen, Matthew J.; Rising, James A.; Wagner, GernotBlok et al. characterize our Policy Forum as an indictment of the Intergovernmental Panel on Climate Change’s (IPCC’s) estimates of mitigation costs, but that was not our intention. We agree with Blok et al.’s call to continually update the economics-focused integrated assessment models. This action, along with more cross-validation between bottom-up and top-down approaches, is precisely the goal of the piece.Item Entropy Analysis of Implicit Heat Fluxes in Multi-Temperature Mixtures(Entropy, 2024-08-24) Kirwan, A. D., Jr.; Massoudi, MehrdadWe propose new implicit constitutive relations for the heat fluxes of a two-temperature mixture of fluids. These relations are frame-indifferent forms. However, classical explicit forms of the stress tensors and the interaction forces (specified as explicit forms of constitutive relations) as given in mixture theory are used. The focus here is to establish constraints imposed on the implicit terms in the heat fluxes due to the Second Law of Thermodynamics. Our analysis establishes that the magnitude of the explicit entropy production is equal to or greater than that of the implicit entropy production.Item Lateral Transport Controls the Tidally Averaged Gravitationally Driven Estuarine Circulation: Tidal Mixing Effects(Journal of Physical Oceanography, 2024-08-01) Kukulka, Tobias; Chant, Robert J.In classic models of the tidally averaged gravitationally driven estuarine circulation, denser salty oceanic water moves up the estuary near the bottom, while less dense riverine water flows toward the ocean near the surface. Traditionally, it is assumed that the associated pressure gradient forces and salt advection are balanced by vertical mixing. This study, however, demonstrates that lateral (across the estuary width) transport processes are essential for maintaining the estuarine circulation. This is because for realistic estuarine bathymetry, the depth-integrated salt transport up the estuary is enhanced in the deeper estuary channel. A closed salt budget then requires the lateral transport of this excess salt in the deeper channel toward the estuarine flanks. To understand how such lateral transport affects the estuarine salt and momentum balances, we devise an idealized model with explicit lateral transport focusing on tidally averaged lateral mixing effects. Solutions for the along-estuary velocity and salinity are nondimensionalized to depend only on one single nondimensional parameter, referred to as the Fischer number, which describes the relative importance of lateral to vertical tidal mixing. For relatively strong lateral tidal mixing (greater Fischer number), salinity and velocity variations are predominantly vertical. For relatively weak lateral tidal mixing (smaller Fischer number), salinity and velocity variations are predominantly lateral. Overall, lateral transport greatly affects the estuarine circulation and controls the estuarine salinity intrusion length, which is demonstrated to scale inversely with the Fischer number.Item Leptothrix ochracea genomes reveal potential for mixotrophic growth on Fe(II) and organic carbon(Applied and Environmental Microbiology, 2024-08-12) Tothero, Gracee K.; Hoover, Rene L.; Farag, Ibrahim F.; Kaplan, Daniel I.; Weisenhorn, Pamela; Emerson, David; Chan, Clara S.Leptothrix ochracea creates distinctive iron-mineralized mats that carpet streams and wetlands. Easily recognized by its iron-mineralized sheaths, L. ochracea was one of the first microorganisms described in the 1800s. Yet it has never been isolated and does not have a complete genome sequence available, so key questions about its physiology remain unresolved. It is debated whether iron oxidation can be used for energy or growth and if L. ochracea is an autotroph, heterotroph, or mixotroph. To address these issues, we sampled L. ochracea-rich mats from three of its typical environments (a stream, wetlands, and a drainage channel) and reconstructed nine high-quality genomes of L. ochracea from metagenomes. These genomes contain iron oxidase genes cyc2 and mtoA, showing that L. ochracea has the potential to conserve energy from iron oxidation. Sox genes confer potential to oxidize sulfur for energy. There are genes for both carbon fixation (RuBisCO) and utilization of sugars and organic acids (acetate, lactate, and formate). In silico stoichiometric metabolic models further demonstrated the potential for growth using sugars and organic acids. Metatranscriptomes showed a high expression of genes for iron oxidation; aerobic respiration; and utilization of lactate, acetate, and sugars, as well as RuBisCO, supporting mixotrophic growth in the environment. In summary, our results suggest that L. ochracea has substantial metabolic flexibility. It is adapted to iron-rich, organic carbon-containing wetland niches, where it can thrive as a mixotrophic iron oxidizer by utilizing both iron oxidation and organics for energy generation and both inorganic and organic carbon for cell and sheath production. IMPORTANCE Winogradsky's observations of L. ochracea led him to propose autotrophic iron oxidation as a new microbial metabolism, following his work on autotrophic sulfur-oxidizers. While much culture-based research has ensued, isolation proved elusive, so most work on L. ochracea has been based in the environment and in microcosms. Meanwhile, the autotrophic Gallionella became the model for freshwater microbial iron oxidation, while heterotrophic and mixotrophic iron oxidation is not well-studied. Ecological studies have shown that Leptothrix overtakes Gallionella when dissolved organic carbon content increases, demonstrating distinct niches. This study presents the first near-complete genomes of L. ochracea, which share some features with autotrophic iron oxidizers, while also incorporating heterotrophic metabolisms. These genome, metabolic modeling, and transcriptome results give us a detailed metabolic picture of how the organism may combine lithoautotrophy with organoheterotrophy to promote Fe oxidation and C cycling and drive many biogeochemical processes resulting from microbial growth and iron oxyhydroxide formation in wetlands.Item Hypoxia Triggered by Expanding River Plume on the East China Sea Inner Shelf During Flood Years(Journal of Geophysical Research: Oceans, 2024-07-31) Li, Dewang; Chen, Jianfang; Wang, Bin; Jin, Haiyan; Shou, Lu; Lin, Hua; Miao, Yanyi; Sun, Qianwen; Jiang, Zhibing; Meng, Qicheng; Zeng, Jiangning; Zhou, Feng; Cai, Wei-JunThe frequency of riverine floods is predicted to increase in East Asia. However, the response of coastal hypoxia (<63 μmol L−1) to floods has not been well understood. In the summer of 2020, characterized by one of the most significant Changjiang water fluxes in three decades, we conducted a cruise during the flood period on the East China Sea inner shelf. Our observations revealed severe bottom hypoxia with a maximum spatial coverage of ∼11,600 km2 and a minimum dissolved oxygen concentration (DO) of 21 μmol L−1. In the surface layer, the relationships between salinity and nitrate, dissolved inorganic carbon (DIC) indicated significant organic matter production, validated by a high-Chlorophyll-a (Chl a) patch (>5 μg L−1). Furthermore, the significant relationship between apparent oxygen utilization and DIC of deep waters reveals that the organic matter decomposition primarily drove the hypoxia during the flood period. Episodic wind events also influenced bottom DO and DIC, by transporting surface waters to the deep. Multiple-years data set shows that the average Changjiang nitrate flux during flood years is about 1.4 times that during non-flood years. The flood waters mix with estuarine waters, forming the high-nutrient plume waters, which expanded farther offshore during the flood period. While high turbidity remained confined to the inner estuary. Consequently, the high-Chl a area significantly expanded, which significantly exacerbated the hypoxia. Key Points - We observed a maximum hypoxia area of ∼11,600 km2, and a minimum dissolved oxygen of 21 μmol L−1 during the flood period in 2020 - Significant nitrate removal and surface Chlorophyll a exceeding 29 μg L−1 suggested intense biological production during the flood period - The expansion of high-Chl a plume area during flood periods surpasses that of non-flood periods, contributing to hypoxia area increase Plain Language Summary Coastal waters are severely threatened by hypoxia, which impacts the growth, reproduction, and migration of marine organisms. Nutrient inputs from river basins are one of the major controlling factors of hypoxia in coastal oceans. The frequency and intensity of floods in river basins are projected to increase in the context of global warming in East Asia. However, the relationship between floods and coastal hypoxia is not well documented. The year 2020 witnessed lots of riverine flood events across Asian countries, which provided us with an excellent opportunity to reveal the influences of flood on hypoxia development on the shelf. In 2020, the August nitrate flux of Changjiang was 1.5 times higher compared to that in non-flood years. We observed maximum hypoxic waters covering 11,600 km2 with a minimum DO of 21 μmol L−1 on the East China Sea inner shelf. Historical data showed that the floods led to the expansion of the high-nutrient plume area, resulting in high biological production in the plume, and a nearly doubling of the hypoxia extent in the bottom waters. With the growing risk of intensive floods, hypoxia is likely to aggravate in coastal waters.Item The source and accumulation of anthropogenic carbon in the U.S. East Coast(Science Advances, 2024-08-09) Li, Xinyu; Wu, Zelun; Ouyang, Zhangxian; Cai, Wei-JunThe ocean has absorbed anthropogenic carbon dioxide (Canthro) from the atmosphere and played an important role in mitigating global warming. However, how much Canthro is accumulated in coastal oceans and where it comes from have rarely been addressed with observational data. Here, we use a high-quality carbonate dataset (1996–2018) in the U.S. East Coast to address these questions. Our work shows that the offshore slope waters have the highest Canthro accumulation changes (ΔCanthro) consistent with water mass age and properties. From offshore to nearshore, ΔCanthro decreases with salinity to near zero in the subsurface, indicating no net increase in the export of Canthro from estuaries and wetlands. Excesses over the conservative mixing baseline also reveal an uptake of Canthro from the atmosphere within the shelf. Our analysis suggests that the continental shelf exports most of its absorbed Canthro from the atmosphere to the open ocean and acts as an essential pathway for global ocean Canthro storage and acidification.Item Development of an efficient, effective, and economical technology for proteome analysis(Cell Reports: Methods, 2024-06-11) Martin, Katherine R.; Le, Ha T.; Abdelgawad, Ahmed; Yang, Canyuan; Lu, Guotao; Keffer, Jessica L.; Zhang, Xiaohui; Zhuang, Zhihao; Asare-Okai, Papa Nii; Chan, Clara S.; Batish, Mona; Yu, YanbaoHighlights • Rapid, robust, and cost-effective alternative to proteomics sample preparation • Versatile filter devices can meet a wide range of proteomics analysis needs • On-filter in-cell digestion facilitates low-input proteomics • Ready-to-go E3 and E4 filter devices are available Motivation Conventional proteomics sample processing methods often have high technical barriers to broad biomedical scientists, leading to difficulties for quick adoption and standardization. Existing protocols are also typically associated with costly reagents and accessories, making them less feasible for resource-limited settings as well as for clinical proteomics and/or core facilities where large numbers of samples are usually processed. Thus, there is a strong unmet need for an easy-to-use, reliable, and low-cost approach for general proteomics sample preparation. Summary We present an efficient, effective, and economical approach, named E3technology, for proteomics sample preparation. By immobilizing silica microparticles into the polytetrafluoroethylene matrix, we develop a robust membrane medium, which could serve as a reliable platform to generate proteomics-friendly samples in a rapid and low-cost fashion. We benchmark its performance using different formats and demonstrate them with a variety of sample types of varied complexity, quantity, and volume. Our data suggest that E3technology provides proteome-wide identification and quantitation performance equivalent or superior to many existing methods. We further propose an enhanced single-vessel approach, named E4technology, which performs on-filter in-cell digestion with minimal sample loss and high sensitivity, enabling low-input and low-cell proteomics. Lastly, we utilized the above technologies to investigate RNA-binding proteins and profile the intact bacterial cell proteome. Graphical abstract available at: https://doi.org/10.1016/j.crmeth.2024.100796Item Novel CTD tag establishes shark fins as ocean observing platforms(Scientific Reports, 2024-06-15) Pagniello, Camille M. L. S.; Castleton, Michael R.; Carlisle, Aaron B.; Chapple, Taylor K.; Schallert, Robert J.; Fedak, Michael; Block, Barbara A.Animal-borne tags are effective instruments for collecting ocean data and can be used to fill spatial gaps in the observing network. We deployed the first conductivity, temperature, and depth (CTD) satellite tags on the dorsal fin of salmon sharks (Lamna ditropis) to demonstrate the potential of sharks to monitor essential ocean variables and oceanographic features in the Gulf of Alaska. Over 1360 km and 36 days in the summer of 2015, the salmon shark collected 56 geolocated, temperature-salinity profiles. The shark swam through a plume of anomalously salty water that originated from the “Blob” and encountered several mesoscale eddies, whose subsurface properties were altered by the marine heatwave. We demonstrate that salmon sharks have the potential to serve as submesoscale-resolving oceanographic platforms and substantially increase the spatial coverage of observations in the Gulf of Alaska.Item Obliquity Dominance in Early Pleistocene Sediments From the Antarctic Zone of the Southern Ocean (Indian Ocean Sector)(Paleoceanography and Paleoclimatology, 2024-05-26) Billups, K.; Münch, B.; Garrioch, I.; Bradtmiller, L.We constructed a record of percent biogenic silica (opal) accumulation at Ocean Drilling Program Site 745B located in the Indian Ocean sector of the Antarctic Zone of the Southern Ocean. The record spans the majority of the early Pleistocene (1.1–2.6 Ma). Orbital-scale sampling affords a look at the relative importance of obliquity versus precession variability through a time interval that is characterized by obliquity pacing in early Pleistocene δ18O records. Variations in the site's magnetic susceptibility record closely resemble those in the benthic foraminiferal δ18O stack (Lisiecki & Raymo, 2005, https://doi.org/10.1029/2004pa001071) and provide orbital-scale age control. Between 1.1 and 1.8 Ma, obliquity-related 41 kyr spectral peaks dominate with relatively little power at precession periods (23–19 kyr) in all records. Between 1.8 and 2.6 Ma, only the δ18O and magnetic susceptibility data display a distinct 41 kyr peak, while the opal lacks spectral power at any of the orbital periodicities. The lack of more pronounced precession-scale variations in the two proxy records is consistent with observations in foraminiferal δ18O records. A low or absent response to precession in these records appears to be due to environmental control. Lack of orbital forcing in the opal record before 1.8 Ma may reflect both a more southerly location of the polar frontal zone with respect to the site, and thus the site's position outside the region of wind-driven upwelling, and/or upwelling waters undersaturated with respect to silica prior to the establishment of the opal belt at about 2 Ma.