Global Biogeochemical Cycles最新文献

{"title":"Tracing Pan-Canadian Arctic Water Masses and Dissolved Inorganic Carbon Cycling Using Stable and Radiocarbon Isotopes","authors":"L. Jasperse,&nbsp;B. G. T. Else,&nbsp;L. A. Miller,&nbsp;G. Nickoloff,&nbsp;J. Walker,&nbsp;A. E. Fox,&nbsp;B. D. Walker","doi":"10.1029/2024GB008179","DOIUrl":"https://doi.org/10.1029/2024GB008179","url":null,"abstract":"<p>The Canadian Arctic is warming four times faster than the global average, yet the impact of this perturbation on the marine carbon cycle remains unknown. Dissolved inorganic carbon (DIC) stable isotope (δ¹³C) and radiocarbon (Δ¹⁴C) values are powerful tools for tracing water mass transport, residence times and carbon cycling. While the hydrography of the Canadian Arctic Archipelago (CAA) is well documented, few DIC δ¹³C and Δ¹⁴C values exist for the region. Here, we present new DIC δ¹³C and Δ¹⁴C depth profiles from 19 stations across the CAA sampled in 2021 and place them into the context of five recently published Baffin Bay values. CAA DIC δ¹³C and Δ¹⁴C values ranged from −0.68‰ to +1.86‰, and −90.7 to +49.5‰, respectively. Several negative DIC Δ¹⁴C values (−44.7‰ and −51.9‰) were observed near the Mackenzie River, indicating riverine permafrost carbon is actively incorporated into the nearshore DIC pool. “Bomb” DIC Δ¹⁴C values in the Kitikmeot Sea were attributed to enhanced tidal mixing and heterotrophy together with high regional water mass residence times. A comparison of historical DIC Δ¹⁴C depth profiles from 2009 to 2021 reveals significant dilution of “bomb” ¹⁴C and minor contributions (2.1%–4.4%) of fossil anthropogenic CO₂ within Pacific Summer Water (PSW), Pacific Winter Water (PWW) and Atlantic Fram Strait Water (ATL_FS) in the Beaufort Sea. Finally, the contrast between deep Beaufort Sea and Baffin Bay DIC δ¹³C and Δ¹⁴C values reveal differences in residence time and carbon sources in the two regions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 4","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008179","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143707360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Appreciating GBC 2024 Reviewers","authors":"Isaac Santos,&nbsp;Katsumi Matsumoto,&nbsp;Zanna Chase","doi":"10.1029/2025GB008574","DOIUrl":"https://doi.org/10.1029/2025GB008574","url":null,"abstract":"<p>The Editors of the <i>Global Biogeochemical Cycles</i> express their appreciation to those who served as peer reviewers for the journal in 2024.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008574","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water Column Structure and Nutrient Supply on the Northwest Atlantic Shelf: A Nitrate Isotope Study","authors":"N. Lehmann,&nbsp;M. Kienast,&nbsp;C. Normandeau,&nbsp;P. Thamer,&nbsp;B. Dempsey,&nbsp;B. Thibodeau,&nbsp;C. Buchwald","doi":"10.1029/2024GB008409","DOIUrl":"https://doi.org/10.1029/2024GB008409","url":null,"abstract":"<p>The Northwest Atlantic continental shelf is a highly productive marine region with major uncertainties regarding the supply mechanisms of nutrients fueling productivity. This study uses nitrate isotopes (δ¹⁵N_NO3 and δ¹⁸O_NO3) from the Atlantic Zone Monitoring Program 2020 fall mission and an Optimum Multiparameter Analysis to evaluate on-shelf nutrient transport versus biological supply pathways across three transects from the Laurentian Channel to the central Scotian Shelf. Surface waters showed an imprint of remineralized production, with partial nitrification creating an isotopically light (δ¹⁵N_NO3 ≥2.7‰) surface lens extending from Cabot Strait across the coastal Scotian Shelf. A concurrent enrichment in δ¹⁵N_NO3 and δ¹⁸O_NO3 (&lt;8.5‰, &lt;7.4‰) alongside decreasing nitrate concentrations further indicated phytoplankton assimilation over the deep central shelf (overlying Emerald Basin), a process not observed across Cabot Strait or coastal shelf stations. Subsurface nutrients in Cabot Strait are highly regenerated (&lt;43%), with increased bottom water δ¹⁵N_NO3 signaling sedimentary denitrification in the deep Laurentian Channel. Conversely, subsurface nutrients on the Scotian Shelf were predominantly preformed (&lt;86%), sustained by Cold Intermediate Water from the Gulf of St. Lawrence and warm North Atlantic Central Water (NACW) from offshore. Derived water mass contributions and a distinct isotopically light subsurface layer offshore (δ¹⁵N_NO3 of &gt;4.2‰)−characteristic of N₂ fixation in shallow NACW−indicate a stronger NACW imprint on the central Scotian Shelf compared to the Laurentian Channel and eastern shelf. Our results confirm the importance of slope water advection in supplying subsurface nutrients to the shelf while highlighting the seasonal imprint of recycled production on near-shore surface waters during fall.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008409","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biological Responses to Ocean Acidification Are Changing the Global Ocean Carbon Cycle","authors":"R. C. Barrett,&nbsp;B. R. Carter,&nbsp;A. J. Fassbender,&nbsp;B. Tilbrook,&nbsp;R. J. Woosley,&nbsp;K. Azetsu-Scott,&nbsp;R. A. Feely,&nbsp;C. Goyet,&nbsp;M. Ishii,&nbsp;A. Murata,&nbsp;F. F. Pérez","doi":"10.1029/2024GB008358","DOIUrl":"https://doi.org/10.1029/2024GB008358","url":null,"abstract":"<p>Increased oceanic uptake of CO₂ due to rising anthropogenic emissions has caused lowered pH levels (ocean acidification) that are hypothesized to diminish biotic calcification and reduce the export of total alkalinity (<i>A</i>_T) as carbonate minerals from the surface ocean or their burial in coastal sediments. This “CO₂-biotic calcification feedback” is a negative feedback on atmospheric CO₂, as elevated levels of surface <i>A</i>_T increase the ocean's capacity to uptake CO₂. We detect signatures of this feedback in the global ocean for the first time using repeat hydrographic measurements and seawater property prediction algorithms. Over the course of the past 30 years, we find an increase in global surface <i>A</i>_T of 0.072 ± 0.023 μmol kg⁻¹ yr⁻¹, which would have caused approximately 20 Tmol of additional <i>A</i>_T to accumulate in the surface ocean. This finding suggests that anthropogenic CO₂ emissions are measurably perturbing the cycling of carbon on a planetary scale by disrupting biological patterns. More observations of <i>A</i>_T would be required to understand the effects of this feedback on a regional basis and to fully characterize its potential to reduce the efficiency of marine carbon dioxide removal technology.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008358","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical Weathering Rates, C-Q Relationships, Fluxes, Dam Impact and pCO2 Potential in the Ganga Headwaters: Insights From Weekly Time-Series Data","authors":"Shaifullah,&nbsp;Indra S. Sen","doi":"10.1029/2024GB008320","DOIUrl":"https://doi.org/10.1029/2024GB008320","url":null,"abstract":"<p>Predicted alterations to the hydrological cycle due to higher temperatures at the end of this century will impact riverine processes such as weathering, erosion, and sediment transport. The Himalayan River basins, with their steep slopes, heavy rainfall, and increasing river engineering projects, are excellent sentinels for monitoring climate change and human impacts on rivers. However, few attempts have been made to capture the river mountainous catchment interaction over shorter time scales (weeks to months) to capture pulses of enhanced chemical weathering rates and other riverine processes. Here, we present a weekly time-series record of dissolved inorganic constituents near the mouth of the Alaknanda and Bhagirathi rivers—the two headwater rivers of the Ganga River—with a weekly resolution during 2018–2019. We report new estimates of discharge-weighted concentrations and fluxes. We found chemical weathering rates of 98.2 ± 54.0 and 32.2 ± 20.4 t/km²/year and CO₂ consumption yields by silicate weathering of 3.7 ± 1.5 × 10⁵ and 1.8 ± 1.2 × 10⁵ mol CO₂/km²/year for the Alaknanda and Bhagirathi basins, respectively, which are significantly higher compared to the global chemical weathering rate and CO₂ consumption yield of ∼24 t/km²/year and ∼1 × 10⁵ mol CO₂/km²/year, respectively. We find that the concentration-discharge relationship shows both chemostatic and dilution trends, with the Tehri dam strongly influencing the hydrology of the Bhagirathi River. The alkalinity-DIC framework reveals that the Himalayan weathering acts as a net source of atmospheric pCO₂ over a timescale of 10⁵–10⁷ years. Further, we show that a sampling campaign spreaded well throughout the year is imperative in reducing uncertainties in flux estimation.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Century-Long Analysis of Nitrogen and Phosphorus Surplus in French Agriculture: Trends and Drivers","authors":"H. Guejjoud,&nbsp;F. Curie,&nbsp;C. Grosbois","doi":"10.1029/2024GB008184","DOIUrl":"https://doi.org/10.1029/2024GB008184","url":null,"abstract":"<p>This study provides the longest trend analysis of Nitrogen (N) and phosphorus (P) surplus in France from 1920 to 2020, modeled with the CaSSiS model at both national and departmental levels. At the national scale, the century long average annual N surplus is about 37 ± 13 kg N per ha of utilized agricultural area (UAA) per year, while P surplus averages about 9 ± 7 kg P ha UAA⁻¹ year⁻¹. However, significant periods of change correspond to important agricultural and economic events such as the World Wars and major agri-environmental reforms. Analysis of N and P use efficiency (NUE and PUE, respectively) revealed varying trends over time. NUE averaged 67%, ranging from 52% to 78%, while PUE exhibited larger fluctuations, ranging from 30% to 130%. At the departmental level, N surplus fluctuated between −15 and 140 kg N ha UAA⁻¹, and P surplus ranged from −15 to 41 kg P ha UAA⁻¹. Temporal trends revealed an increase in N surplus in 96% of departments from 1920 to 1990, followed by a decline in about 89% of departments from 1990 to 2020. P surplus increased in all departments until 1974, followed by a consistent decrease. Analysis of five contrasting French departments highlighted the impact of agricultural practices on nutrient surplus. These findings underscore the importance of tailored nutrient management strategies to achieve balanced inputs and outputs, promoting sustainable agriculture and minimizing environmental impacts. This study contributes valuable insights for informed decision-making in nutrient management policies and practices.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008184","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Riverine Particulate Carbon, Nitrogen, and Phosphorus Are Decoupled From Land Cover at the Continental Scale","authors":"Benjamin Trost,&nbsp;Arial J. Shogren,&nbsp;Zacharie T. Loveless,&nbsp;David W. P. Manning,&nbsp;Jonathan P. Benstead","doi":"10.1029/2024GB008278","DOIUrl":"https://doi.org/10.1029/2024GB008278","url":null,"abstract":"<p>While inland freshwater networks cover less than 4% of the Earth's terrestrial surface, these ecosystems play a disproportionately large role in the global cycles of [C]arbon, [N]itrogen, and [P]hosphorus, making streams and rivers critical regulators of nutrient balance at regional and continental scales. Foundational studies have established the relative importance of the hydrologic regime, land cover, and instream removal processes for controlling the transport and processing of C, N, and P in river networks. However, particulate C, N, and P can make up a large proportion of the total material in large rivers and during high flows. To constrain the patterns of the biogeochemistry of riverine particulates, we characterized and modeled dissolved and particulate concentration variability at the continental scale using open-access data from 27 National Ecological Observatory Network (NEON) sites across the United States. We analyzed these data using Boosted Regression Trees (BRTs) to statistically identify if land cover characteristics could predict nutrient quantity and quality of stream particulates. The BRT models revealed that land cover does not strongly predict particulate dynamics across NEON sites but indicate that instream processes might be more important than catchment characteristics alone. In addition, our study demonstrates the consistent importance of particulates relative to dissolved forms, highlighting their likely significance for biogeochemical processes along the freshwater continuum.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008278","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143645936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Blue Carbon Stocks Along the Pacific Coast of North America Are Mainly Driven by Local Rather Than Regional Factors","authors":"Christopher N. Janousek,&nbsp;Johannes R. Krause,&nbsp;Judith Z. Drexler,&nbsp;Kevin J. Buffington,&nbsp;Katrina L. Poppe,&nbsp;Erin Peck,&nbsp;Maria Fernanda Adame,&nbsp;Elizabeth B. Watson,&nbsp;James Holmquist,&nbsp;Scott D. Bridgham,&nbsp;Scott F. Jones,&nbsp;Melissa Ward,&nbsp;Cheryl A. Brown,&nbsp;Lisa Beers,&nbsp;Matthew T. Costa,&nbsp;Heida L. Diefenderfer,&nbsp;Amy B. Borde,&nbsp;Lindsey Sheehan,&nbsp;John Rybczyk,&nbsp;Carolyn Prentice,&nbsp;Andrew B. Gray,&nbsp;Alejandro Hinojosa-Corona,&nbsp;Ana Carolina Ruiz-Fernández,&nbsp;Joan-Albert Sanchez-Cabeza,&nbsp;Karen E. Kohfeld,&nbsp;Paula Ezcurra,&nbsp;Jonathan Ochoa-Gómez,&nbsp;Karen M. Thorne,&nbsp;Marlow G. Pellatt,&nbsp;Aurora M. Ricart,&nbsp;Amanda M. Nahlik,&nbsp;Laura S. Brophy,&nbsp;Richard F. Ambrose,&nbsp;Mira Lutz,&nbsp;Craig Cornu,&nbsp;Stephen Crooks,&nbsp;Lisamarie Windham-Myers,&nbsp;Margot Hessing-Lewis,&nbsp;Fredrick T. Short,&nbsp;Stephen Chastain,&nbsp;Trevor Williams,&nbsp;Tristan Douglas,&nbsp;Elizabeth Fard,&nbsp;Lauren Brown,&nbsp;Michelle Goman","doi":"10.1029/2024GB008239","DOIUrl":"https://doi.org/10.1029/2024GB008239","url":null,"abstract":"<p>Coastal wetlands, including seagrass meadows, emergent marshes, mangroves, and temperate tidal swamps, can efficiently sequester and store large quantities of sediment organic carbon (SOC). However, SOC stocks may vary by ecosystem type and along environmental or climate gradients at different scales. Quantifying such variability is needed to improve blue carbon accounting, conservation effectiveness, and restoration planning. We analyzed SOC stocks in 1,284 sediment cores along &gt;6,500 km of the Pacific coast of North America that included large environmental gradients and multiple ecosystem types. Tidal wetlands with woody vegetation (mangroves and swamps) had the highest mean stocks to 1 m depth (357 and 355 Mg ha⁻¹, respectively), 45% higher than marshes (245 Mg ha⁻¹), and more than 500% higher than seagrass (68 Mg ha⁻¹). Unvegetated tideflats, though not often considered a blue carbon ecosystem, had noteworthy stocks (148 Mg ha⁻¹). Stocks increased with tidal elevation and with fine (&lt;63 μm) sediment content in several ecosystems. Stocks also varied by dominant plant species within individual ecosystem types. At larger scales, marsh stocks were lowest in the Sonoran Desert region of Mexico, and swamp stocks differed among climate zones; otherwise stocks showed little correlation with ecoregion or latitude. More variability in SOC occurred among ecosystem types, and at smaller spatial scales (such as individual estuaries), than across regional climate gradients. These patterns can inform coastal conservation and restoration priorities across scales where preserving stored carbon and enhancing sequestration helps avert greenhouse gas emissions and maintains other vital ecosystem services.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008239","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143638706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Agricultural Land Use Impacts Aquatic Greenhouse Gas Emissions From Wetlands in the Canadian Prairie Pothole Region","authors":"L. A. Logozzo,&nbsp;C. Soued,&nbsp;L. E. Bortolotti,&nbsp;P. Badiou,&nbsp;P. Kowal,&nbsp;B. Page,&nbsp;M. J. Bogard","doi":"10.1029/2024GB008209","DOIUrl":"https://doi.org/10.1029/2024GB008209","url":null,"abstract":"<p>The Prairie Pothole Region (PPR) is the largest wetland complex in North America, with millions of wetlands punctuating the landscapes of Canada and the United States. Here, wetlands have been dramatically impacted by agricultural land use, with unclear implications for regional to global greenhouse gas (GHG) emissions budgets. By surveying wetlands across all three Canadian prairie provinces in the PPR, we show that emissions patterns of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) from aquatic habitats differ among wetlands embedded in cropland versus perennial landcover. Wetlands in cropped landscapes had double the aquatic diffusive emissions (20.6 ± 31.5 vs. 9.4 ± 17.3 g CO₂-<i>eq</i> m⁻² d⁻¹) largely driven by CH₄. Structural equation modeling showed that all three GHGs responded differently to the surrounding landscape properties. Emissions of CH₄ were the most sensitive to land use, responding positively to the elevated phosphorus content and lower sulfate content in cropped settings, despite higher organic matter content in wetlands in perennial landscapes. Aquatic N₂O emissions were negligible, while CO₂ emissions were high, but not strongly related to agricultural land use. While our estimates of aquatic CH₄ emissions from PPR wetlands were high (18.2 ± 41.4 mmol CH₄ m⁻² d⁻¹), accounting for fluxes from vegetated and soil habitats would lead to whole-wetland emissions rates that are lower and comparable to wetlands in other biomes. Our study represents an important step toward understanding wetland emission responses to land use in the PPR and other wetland-rich agricultural landscapes.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008209","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contributions of Vertically Migrating Metazoans to Sinking and Suspended Particulate Matter Fuel N2 Production in the Eastern Tropical North Pacific Oxygen Deficient Zone","authors":"Clara A. Fuchsman,&nbsp;Megan E. Duffy,&nbsp;Jacob A. Cram,&nbsp;Paulina Huanca-Valenzuela,&nbsp;Benjamin P. Gregory,&nbsp;Louis V. Plough,&nbsp;James J. Pierson,&nbsp;Catherine L. Fitzgerald,&nbsp;Allan H. Devol,&nbsp;Richard G. Keil","doi":"10.1029/2024GB008365","DOIUrl":"https://doi.org/10.1029/2024GB008365","url":null,"abstract":"<p>Oxygen Deficient Zones (ODZs) are the largest pelagic sinks of N containing nutrients in the ocean. The offshore Eastern Tropical North Pacific (ETNP) ODZ has been shown to be limited by organic matter. We propose zooplankton/forage fish as a key source of particulate and dissolved organic matter for N₂ production that has previously been ignored. We examined data sets from four cruises (April 2012, January 2017, April 2018, October 2019) at a station in the central ETNP. Backscattering data were used to determine zooplankton vertical migration depths (250–450 m, maximum at 270–280 m). Metazoan DNA concentrations, as measured by quantitative PCR, had a reproducible maximum at 270–280 m, confirming that these signals indicate the presence of zooplankton/forage fish. Additionally, a large maximum in sinking pteropod shells was found at 270 m, indicating that pteropods were part of the migrating community. While crustacean zooplankton have been shown to reduce respiration and excretion of ammonium under anoxia, we found intermittently measurable ammonium concentrations at 270 m. Here we show signatures consistent with organic matter of zooplankton/forage fish origin in the C:N and δ¹³C of suspended and sinking organic matter at the vertical migration depth that suggest transportation to these depths by migrating zooplankton/forage fish. Also coincident with the migration maximum was a reproducible-between-years maximum in the biological N₂ gas, and a repeatable shoulder on the nitrite maximum, which suggest that the migrating zooplankton partially fuels N loss. Thus, zooplankton/forage fish appear to be one source of organic matter which can fuel N₂ production in ODZs.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 3","pages":""},"PeriodicalIF":5.4,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008365","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143554884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}