Open Access Publications - School of Marine Science & Policy
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Item Tellurite and selenite processing by tellurite resistant marine microbes(Applied and Environmental Microbiology, 2025-10-01) Ollivier, Patrick; Hanson, Thomas; Tessier, Emmanuel; Amouroux, David; Church, ThomasUnderstanding microbial transformations of the group VIa/16 metalloids tellurium and selenium is important for the remediation of contaminated environments and has been proposed as a green route for Se/Te nanoparticle synthesis. We previously isolated several strains of aerobic tellurite resistant marine yeast and bacteria. Here, we explored the capability of these strains to metabolize selenite and mixtures of tellurite and selenite to quantify fate and identify volatile metabolic products. The experimental results indicate that selenite is metabolized differently than tellurite by the yeast Rhodotorula mucilaginosa and bacteria Bacillus spp. and Virgibacillus halodenitrificans. The production of volatile Se compounds appears to be positively correlated with selenite resistance. However, selenite fate, e.g., the proportion of volatilized or precipitated Se, was not predictable from tellurite resistance or fate of the same strain. Under non-aerated conditions, when cultures were provided mixtures of selenite and tellurite, tellurite strongly influenced the fate of selenite and the types of volatile products made. Tellurite in oxyanion mixtures appears to strongly inhibit Se volatilization and drive speciation to less complex Se volatiles. Mixtures boosted the production of Te and Se precipitates by Bacillus sp. strain 6A and the production of Te precipitates by Rhodotorula mucilaginosa strains 13B and decreased the production of both volatile Te and Se compounds. Dimethylselenide and dimethyltelluride are acutely toxic by inhalation and oral exposure, so understanding their production is a key consideration in any biologically based manufacture of Se/Te containing nanoparticles.Item Hydrographic and Activity Data From: Light Sensitivity of the Arctic Copepod Metridia Longa During Midnight Sun and Polar Night(2025-09-18) Lightfoot, Meaghan; Last, Kim S.; Cohen, Jonathan H.We sampled the water column hydrography at three locations in the Barents Sea and Kongsfjorden, Svalbard during May 2022 (Midnight Sun) and January 2023 (Polar Night), then collected the copepod Metridia longa for behavioral experiments. Sampling took place in May 2022 (Midnight Sun) and January 2023 (Polar Night) in the Barents Sea at two locations: 74.597 N, 29.057 E (Midnight Sun-shelf; MS-S) and 75.007 N, 15.117 E (Polar Night-shelf; PN-S). Further Polar Night sampling was conducted in Kongsfjorden, Svalbard at 78.967 N, 11.967 E (Polar Night-fjord; PN-F). For more details on sampling and instrumentation, see the paper associated with this dataset: Lightfoot et al. (2025) Biological Bulletin ##:###-###. (record will be updated when article is available) Collections of the copepod Metridia longa were used to measure irradiance and spectral activity responses of copepods in a novel laboratory locomotor activity apparatus. For more details on sampling, instrumentation, and experimental protocols see the paper associated with this dataset: Lightfoot et al. (2025) Biological Bulletin ##:###-###.(record will be updated when article is available)Item SOURCES OF DIC AND δ13C-DIC IN THE ROOSEVELT INLET(2025-01) Jordan A. WatsonThis study investigates biogeochemical variability in Roosevelt Inlet (Lewes, DE), where mixing between four water sources—Broadkill River (freshwater), Canary Creek (marsh), Lewes-Rehoboth Canal (brackish), and Delaware Bay (seawater)—shapes marine carbonate chemistry. The goal of this work is to use discrete endmember tide cycle sampling with continuous data logging to identify contributions of dissolved inorganic carbon (DIC) and δ¹³C-DIC from marshes and Delaware Bay to the Broadkill Estuary. Previous studies of DIC in coastal systems have rarely incorporated δ¹³C data, thereby limiting insight into carbon source attribution. To address this, we conducted five seasonal samplings at each water source where we combined discrete endmember high/low tide and high-resolution tide cycle sampling surveys on separate days and weeks within the same months. Measured pH, pCO₂, total alkalinity (TA), DIC, and δ¹³C-DIC identified physical and biological controls on marine carbonate chemistry. Isotopic signatures revealed the influence of organic matter decomposition, with δ¹³C values consistent with inputs from Spartina alterniflora (–13‰) and freshwater endmembers (–10‰). A two-endmember mixing model demonstrated seasonal effects on DIC and δ¹³C, where August and October values were driven by marsh-derived aerobic respiration rather than sulfate reduction. August and October low tides were dominated by marshland, producing high pCO₂ and low pH and dissolved oxygen (DO) values. December and February were influenced by the Delaware Bay endmember (–10‰), and reflected carbonate precipitation and cumulative aerobic processes, whereas April conditions indicated enhanced photosynthesis. Here, the mixing model effectively traced organic carbon sources and may be applicable to similar estuarine systems.Item Decadal Variability in the Core Strength of the South Pacific Convergence Zone(Geophysical Research Letters, 2025-08-25) Wang, Handa; Zhuang, Wei; Yan, Xiao-HaiThe South Pacific Convergence Zone (SPCZ), the primary rainfall source for South Pacific islands, exhibits decadal variability in its core region that remains insufficiently studied. Isolating sea surface temperature internal variability (SSTIV) from external forcing (1940–2013) reveals SSTIV is the dominant driver of SPCZ core strength variability (CSV), quantified via 10‐m wind convergence. Local SSTIV modulates CSV through thermodynamic feedbacks, whereas equatorial Pacific sea surface temperature (SST) anomalies exert limited remote influence. Regression analysis shows a 9.1 × 10 6 s 1 increase in CSV and a 1.7 mm day 1 increase in precipitation per 1°C SSTIV rise on decadal scales. Although external forcing significantly shapes SPCZ SST, its direct impact on CSV is counteracted by the tropical Pacific SST gradient. The strong sensitivity of CSV to internal SST variability, compared to its muted response to external forcing, underscores the pivotal role of internal climate variability in shaping SPCZ dynamics.Item Glacial-Interglacial Climate Cycles of Atmospheric Hg Deposition: Insights From Hg Isotopes in Loess-Paleosol Sequences on the Chinese Loess Plateau(Geophysical Research Letters, 2025-04-09) Xue, Wen; Xu, Zhidong; Cheng, Xing; Gou, Longfei; He, Maoyong; Jin, Zhangdong; Li, Miling; Fang, Linchuan; Yin, RunshengAs a highly volatile heavy metal, Hg is transported over long distances in the atmosphere and enters global ecosystems via Hg(II) wet deposition and Hg(0) dry deposition. The Chinese Loess Plateau develops loess-paleosol sequences (eolian deposits) reflecting glacial-interglacial cycles. Here, we investigate the Hg concentration and isotopic composition of loess-paleosol sequences covering three glacial-interglacial cycles (spanning 350–80 ka). Paleosol layers display higher THg, Δ199Hg, and Δ200Hg values than loess layers, meaning enhanced Hg(II) wet deposition during interglacials. Based on a Δ200Hg-based mixing model, Hg(II) wet and Hg(0) dry depositions account for 42% and 58% of Hg input into the Chinese Loess Plateau during interglacials but 21% and 79% during glacials, respectively. This work highlights a strong climatic control on atmospheric Hg deposition at glacial-interglacial time scales, and suggests that atmospheric Hg deposition will likely increase in middle latitudes without considering perturbations of anthropogenic emissions. Key Points - The atmospheric Hg deposition history was reconstructed using loess-paleosol sequences on the Chinese Loess Plateau - Glacial-interglacial cycles of atmospheric Hg deposition were reported for the first time in eolian deposits - Variations in summer and winter monsoons during glacial-interglacial cycles control atmospheric Hg deposition Plain Language Summary Mercury is a heavy metal pollutant that undergoes global transport in the atmosphere and enters global ecosystems via atmospheric deposition. This work for the first time observes glacial-interglacial cycles of Hg concentration and Hg isotopic ratios in loess-paleosol sequences on the Chinese Loess Plateau. The results provide strong evidence of climatic control on atmospheric Hg deposition. Variations in summer and winter monsoons during glacial-interglacial cycles regulate the intensity of atmospheric Hg deposition on the Chinese Loess Plateau. This work predicts that atmospheric Hg deposition will likely increase in middle latitudes without considering perturbations of anthropogenic emissions.Item Social Perceptions of Offshore Wind Energy through the Lens of Acceptance and Justice(Mainsheet, 2024-12-20) Howley, Shannon; Korein, EmmaThe offshore wind industry is rapidly expanding across the globe as countries aim to meet ambitious renewable energy targets and provide renewable energy to coastal population hubs. Offshore wind represents not only a transformation of energy markets but also ocean spaces with which individuals and communities have economic, personal, and cultural ties. Social science research can help understand the complexity of this human-technology interaction by exploring individuals’ perceptions of offshore wind projects and their effect on sociocultural systems. In this article, we review two theories that examine the social dimensions of offshore wind: social acceptance and energy justice. We then conduct a literature review of offshore wind research using these social acceptance and energy justice frameworks, with a focus on three groups of affected communities (coastal residents, tourists and recreationists, and commercial and recreational fishers) and compensation measures. We finish with a discussion of what the current literature reveals about the complex and diverse responses people have to offshore wind development in their community and the implications for future research.Item An approach to predicting linear trends in tagging-related mortality and tag loss during mark-recapture studies(Frontiers in Ecology and Evolution, 2025-04-30) McCutcheon, Jasper; Campbell, Brendan; Hudock, Rileigh E.; Motz, Noah; Windsor, Madison; Carlisle, Aaron; Hale, EdwardUsing tags within a mark-recapture framework allows researchers to assess population size and connectivity. Such methods have been applied in coastal zone habitats to monitor salt marsh restoration success by comparing the movement patterns of Mummichogs (Fundulus heteroclitus) between restored and natural marshes. Visible Implant Elastomer (VIE) tags are commonly used to tag small fish like Mummichogs, though the retention and survival of small fish using this method varies between studies, producing uncertainty during mark-recapture-based approaches. To address this, we conducted a laboratory experiment to determine the rate of tag loss and mortality of VIE tags on Mummichogs of two size classes (greater or less than 61 mm) and across different taggers. Tag loss and mortality increased over time, and the latter significantly varied between taggers. We then developed a predictive model, R package ‘retmort’, to account for the effect of this increase on mark-recapture studies. When adapted to a series of published works, our model provided rational estimates of tagging error for multiple species and tagging methods. Of the case studies the model was applied to (n = 26), 15 resulted in a percent standard error greater than 5%, signaling a significant percent of error due to uncounted, tagged animals. By not accounting for these individuals, recapture studies, particularly those that assess restoration efforts and coastal resilience, could underestimate the effects of those projects, leading to superfluous restoration efforts and erroneous recapture data for species with low tag retention and high mortality rates.Item Assessing Deep and Abyssal Ocean Heat Content Changes With a Dynamically Consistent Ocean State Estimate(Journal of Geophysical Research: Oceans, 2025-03-20) Zhang, Yang; Liang, Xinfeng; Chambers, Don P.; Huang, MinghaiBecause of the sparseness of existing observations, our understanding of deep (2,000–4,000 m) and abyssal (>4,000 m) ocean heat content (OHC) changes remains limited. Previous studies utilizing repeated hydrographic section measurements identified a global warming trend in these layers. However, studies based on a widely used ocean state estimate ECCO v4 (Estimating the Circulation and Climate of the Ocean, version 4) show a contradictory cooling trend in the deep and abyssal Pacific and Indian Oceans. To examine if the sparseness of hydrographic measurements results in this contrasting conclusion, we conducted a sampling experiment with ECCO v4. Our results show that the signs of the OHC trends in the deep and abyssal oceans from the full spatial-temporal data and the sampled data are generally consistent. The largest uncertainties mainly occur in regions where the deep ocean is dominated by newly formed deep-water masses or where hydrographic sections are extremely sparse, such as the Northwest Atlantic Ocean and the Southern Ocean. Our findings also indicate that the discrepancies between ECCO v4 and observations in deep and abyssal OHC changes are not likely a sampling issue, and further studies are needed to determine the reasons. Key Points - A sampling experiment was conducted to assess possible biases of deep and abyssal ocean heat content changes due to under-sampling - Deep and abyssal ocean heat content trends from sampled data are generally consistent with those from full spatial-temporal data - Under-sampling does not explain the differences between ECCO and observations in the deep and abyssal ocean heat content changes Plain Language Summary Deep and abyssal oceans are key heat reservoirs in the Earth System. However, the limited number of available observations constrains our understanding of changes in deep and abyssal ocean heat content (OHC). In addition, studies based on limited observations and a widely used ocean state estimate display contrasting trends in deep and abyssal OHC changes in the Pacific and Indian Oceans. Here, we conduct a sampling experiment with a state-of-the-art ocean synthesis product to explore if under-sampling is the reason for the contrasting results. We found that the OHC changes estimated from the repeated hydrographic sections are generally reliable, suggesting that the current sampling framework is not likely the cause of the opposite OHC trends in studies based on observational data and the ocean state estimate. Significant uncertainties do exist and primarily appear in regions such as the Northwest Atlantic and Southern Ocean. Our findings provide a valuable reference for understanding deep and abyssal ocean changes as well as for designing and implementing future global ocean observational systems.Item Considerations for using sharks as ocean observing platforms(ICES Journal of Marine Science, 2025-02-07) Wiernicki, Caroline J.; Curtis, Tobey H.; Block, Barbara A.; Shivji, Mahmood S.; Vaudo, Jeremy J.; Wetherbee, Bradley M.; Holland, Kim N.; Pinti, Jérôme; Oliver, Matthew J.; Carlisle, Aaron B.The combination of animal-borne telemetry and oceanographic sensor technologies creates an opportunity for marine animals to serve as ocean observing platforms (OOPs), carrying tags that record in situ oceanographic data as they naturally move. In this study, we create a blueprint of shark OOP species selection, quantifying and comparing the potential for species to transmit collected data, the environmental ranges various candidates are expected to encounter, and the oceanographic features they may be expected to resolve. Metrics of data satellite transmission probability, movement behaviors, and environmental sampling ranges are calculated combining historically collected satellite tag data for 11 shark species tagged in the Atlantic and Pacific Ocean basins. Species with the highest satellite data transmission potential include shortfin mako (Atlantic and Pacific) and blue (Pacific) sharks. These species also demonstrated overlap in time and length scales for area-restricted search-like movement behaviors with several mesoscale ocean features, including hurricanes and upwelling events. Additional comparisons of decorrelation time scales between theoretical shark versus glider sampling platforms suggest that shark OOPs have the ability to provide three times more uncorrelated water column temperature and conductivity profiles than gliders at 15% of the operational cost.Item A global dataset of nitrogen fixation rates across inland and coastal waters(Limnology and Oceanography Letters, 2025-01-23) Fulweiler, Robinson W.; Berberich, Megan E.; Rinehart, Shelby A.; Taylor, Jason M.; Kelly, Michelle C.; Ray, Nicholas E.; Oczkowski, Autumn; Balint, Sawyer J.; Geisser, Alexandra H.; Mahoney, Catherine R.; Benavides, Mar; Church, Matthew J.; Loeks, Brianna; Newell, Silvia E.; Olofsson, Malin; Oppong, Jimmy C.; Roley, Sarah S.; Vizza, Carmella; Wilson, Samuel T.; Groffman, Peter M.; Scott, J. Thad; Marcarelli, Amy M.Biological nitrogen fixation is the conversion of dinitrogen (N2) gas into bioavailable nitrogen by microorganisms with consequences for primary production, ecosystem function, and global climate. Here we present a compiled dataset of 4793 nitrogen fixation (N2-fixation) rates measured in the water column and benthos of inland and coastal systems via the acetylene reduction assay, 15N2 labeling, or N2/Ar technique. While the data are distributed across seven continents, most observations (88%) are from the northern hemisphere. 15N2 labeling accounted for 67% of water column measurements, while the acetylene reduction assay accounted for 81% of benthic N2-fixation observations. Dataset median area-, volume-, and mass-normalized N2-fixation rates are 7.1 μmol N2-N m−2 h−1, 2.3 × 10−4 μmol N2-N L−1 h−1, and 4.8 × 10−4 μmol N2-N g−1 h−1, respectively. This dataset will facilitate future efforts to study and scale N2-fixation contributions across inland and coastal aquatic environments. Scientific Significance Statement Here we provide and describe a dataset of global nitrogen fixation rates for the water column and benthos of inland and coastal waters. This dataset is useful for understanding how nitrogen fixation varies across these ecosystems and is a resource for focusing future research questions. We anticipate this is the first version of this dataset that will continue to develop with newly published rates and expanded data on environmental drivers.Item Characterizing Storm-Induced Coastal Flooding Using SAR Imagery and Deep Learning(IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2025-01-21) Edwing, Deanna; Meng, Lingsheng; Lv, Suna; Yan, Xiao-HaiFlooding is among the most common yet costly worldwide annual disasters. Previous studies have proven that synthetic aperture radar (SAR) is an effective tool for flooding observation due to its high-resolution and timely observations, and deep learning-based models can accurately extract water bodies from SAR imagery. However, many previous flood analyses do not account for influences of tides and permanent water bodies, and the comprehensive characteristics of coastal storm flooding are still not fully understood. This study therefore presents a novel approach for isolating storm-induced flood waters in coastal regions from SAR imagery through the identification and removal of permanent water bodies and tidal inundation. This methodology is applied to the Delaware Bay region, with ancillary geospatial data used to determine resulting landcover impacts. Results indicate that flooding primarily impacts agricultural and marsh regions, as well as urban areas like airports and road systems adjacent to rivers or large inland bays. The sensitivity impacts of tides on flood estimates reveals that estimates significantly increase if included in analysis, highlighting the importance of their removal prior to flood identification. Finally, exploration into intense coastal storm events in the Delaware Bay region reveal the importance of storm characteristics like high water levels, wind, and precipitation in generating extreme flooding conditions. The case study presented here has important implications for other coastal regions and provides an innovative and comprehensive approach to coastal storm flood identification and characterization which can benefit coastal managers, emergency responders, coastal communities, and researchers interested in coastal flood hazards.Item Bacteria-Produced Algicide for Field Control of Toxic Dinoflagellates Does Not Cause a Cortisol Stress Response in Two Estuarine Fish Species(Marine Biotechnology, 2025-01-14) Simons, Victoria E.; Targett, Timothy E.; Gaffney, Patrick M.; Coyne, Kathryn J.Application of algicides produced by naturally occurring bacteria is considered an environmentally friendly approach to control harmful algal blooms. However, few studies assess the effects of bacterial algicides on non-target species, either independently or with other stressors. Here, we measured sub-lethal effects of dinoflagellate-specific algicide IRI-160AA on the estuarine fish Fundulus heteroclitus and Menidia menidia in laboratory experiments. Plasma cortisol levels were measured to test whether a neuroendocrine stress response was induced in these fish following exposure to the algicide alone, and in combination with diel-cycling hypoxia and/or pH, at 25 and 30 °C. Results show that exposure to IRI-160AA does not significantly affect cortisol levels in either species, at either temperature tested, whether exposure occurs independently or with co-occurring hypoxia and/or pH cycles as potential multiple stressors. These results support the application of IRI-160AA as an environmentally friendly approach to control harmful algal blooms in estuarine environments.Item Private versus Public Flood Insurance: Differences in Premiums and Uptake Observed in Two Coastal Housing Markets Using Survey Data(Marine Resource Economics, 2025-01-01) Fielding, Samuel; Parsons, GeorgeUsing a natural experiment created by the 1982 Coastal Barrier Resources Act (CBRA), we measure the extent to which insurance premiums vary between private and publicly backed flood insurance policies. The CBRA resulted in homeowners living in neighboring housing markets in which some have access to the federally backed National Flood Insurance Program (NFIP) and others do not. Flood risks and other features of the neighborhoods are otherwise indistinguishable. Those without access to publicly backed insurance must purchase private insurance if they desire coverage. We compare insurance premiums and uptake in the two markets and find that premiums for private coverage are significantly higher than public rates (after controlling for other factors in a reduced-form regression), implying a subsidy by NFIP. We also find a much lower uptake of insurance in the areas without federally backed insurance. Our results are based on a mail survey of residents in two US coastal communities with a 50% response rate: North Bethany Beach, Delaware, and North Topsail Beach, North Carolina. We also present results related to perceptions of flood hazards, of being under- or overinsured, and measures taken to mitigate flood damage.Item Comparative metagenomics of tropical reef fishes show conserved core gut functions across hosts and diets with diet-related functional gene enrichments(Applied and Environmental Microbiology, 2025-01-22) Wu, Derek G.; Harris, Cassandra R.; Kalis, Katie M.; Bowen, Malique; Biddle, Jennifer F.; Farag, Ibrahim F.Fish gut microbial communities are important for the breakdown and energy harvesting of the host diet. Microbes within the fish gut are selected by environmental and evolutionary factors. To understand how fish gut microbial communities are shaped by diet, three tropical fish species (hawkfish, Paracirrhites arcatus; yellow tang, Zebrasoma flavescens; and triggerfish, Rhinecanthus aculeatus) were fed piscivorous (fish meal pellets), herbivorous (seaweed), and invertivorous (shrimp) diets, respectively. From fecal samples, a total of 43 metagenome assembled genomes (MAGs) were recovered from all fish diet treatments. Each host-diet treatment harbored distinct microbial communities based on taxonomy, with Proteobacteria, Bacteroidota, and Firmicutes being the most represented. Based on their metagenomes, MAGs from all three host-diet treatments demonstrated a baseline ability to degrade proteinaceous, fatty acid, and simple carbohydrate inputs and carry out central carbon metabolism, lactate and formate fermentation, acetogenesis, nitrate respiration, and B vitamin synthesis. The herbivorous yellow tang harbored more functionally diverse MAGs with some complex polysaccharide degradation specialists, while the piscivorous hawkfish’s MAGs were more specialized for the degradation of proteins. The invertivorous triggerfish’s gut MAGs lacked many carbohydrate-degrading capabilities, resulting in them being more specialized and functionally uniform. Across all treatments, several MAGs were able to participate in only individual steps of the degradation of complex polysaccharides, suggestive of microbial community networks that degrade complex inputs. IMPORTANCE The benefits of healthy microbiomes for vertebrate hosts include the breakdown of food into more readily usable forms and production of essential vitamins from their host's diet. Compositions of microbial communities in the guts of fish in response to diet have been studied, but there is a lack of a comprehensive understanding of the genome-based metabolic capabilities of specific microbes and how they support their hosts. Therefore, we assembled genomes of several gut microbes collected from the feces of three fish species that were being fed different diets to illustrate how individual microbes can carry out specific steps in the degradation and energy utilization of various food inputs and support their host. We found evidence that fish gut microbial communities share several core functions despite differences in microbial taxonomy. Herbivorous fish harbored a functionally diverse microbial community with plant matter degraders, while the piscivorous and invertivorous fish had microbiomes more specialized in protein degradation.Item Identifying potential introduced and natural sources of pollution in Delaware watersheds(Applied and Environmental Microbiology, 2024-12-17) Bowen, Malique; Main, Christopher R.; Farag, Ibrahim F.; Biddle, Jennifer F.Managing water quality with microbial impairment caused by Enterococcus poses unique challenges regarding the determination of fecal host origin. Most water monitoring is performed based on Enterococcus counts that neither detect the location of the introduction of pollution nor identify the type of contaminating Enterococcus. The use of sequenced-based microbial source tracking could allow for identification of fecal origin and potential remediation of pollution. The state of Delaware has numerous waterways with high microbial impairment from unknown sources, so we used sequence-based microbial source tracking to investigate potential microbial pollution in three watersheds with significant variation in land use and population density. In this study, we use a 16S rRNA sequence reference library of microbial communities from relevant fecal sources (wild animal, domestic animal, sediment, and septic/wastewater) to determine the most likely sources of microbial impairment in three Delaware watersheds. This study assigned sources of microbial contamination to mostly human-related sources (septic and wastewater) or unknown sources indicating that waste infrastructure may have a larger influence on microbial community structure in Delaware watersheds than previously considered. Our results suggest that long-term source tracking is valuable for ruling out native or domesticated animals as contributors to water pollution. IMPORTANCE Traditional microbial pollution monitoring utilizes specific fecal indicator bacteria that need to grow in the laboratory for detection. Here, we show the use of sequence information from whole microbial communities and an expanded reference library in microbial source tracking. Expanding the host detection range by including the whole microbial community may allow for a wider range of potential fecal origin identification even when specific fecal indicators are absent or in low concentration. We show that many Delaware waterways bear the signature of human influence compared to natural sources. In addition, the robust reference library built in this study can be used to conduct source tracking studies in the mid-Atlantic USA.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.