Limnology and Oceanography最新文献

{"title":"High benthic community respiration and ecosystem response to phytodetrital input in a subpolar fjord on the West Antarctic Peninsula","authors":"Marta M. Cecchetto, Craig R. Smith, Clifton C. Nunnally, Andrew K. Sweetman","doi":"10.1002/lno.12688","DOIUrl":"https://doi.org/10.1002/lno.12688","url":null,"abstract":"Glaciomarine fjords dominate the coastal margin of the West Antarctic Peninsula. Studies in similar habitats in the Arctic have shown that benthic biodiversity and ecosystem functioning in inner and middle fjord basins are reduced by turbidity and sedimentation disturbance caused by climate warming–enhanced glacial melting. In contrast, the inner and middle fjord basins along the West Antarctic Peninsula are characterized as productivity and biodiversity hotspots, but benthic ecosystem functions remain unevaluated. In 2015–2016, we conducted sediment respiration and <jats:sup>13</jats:sup>C pulse‐chase experiments to assess benthic ecosystem functions along a five‐station transect at ~ 500–600 m depths from the inner Andvord Bay fjord, through to Gerlache Strait, and onto the open continental shelf. Incubation samples from the inner and middle basins of Andvord Bay showed peaks in background seafloor respiration, benthic biomass, and uptake of labeled algal biomass compared to more outlying stations; the continental shelf exhibited the lowest levels of these variables, as well as dissolved inorganic carbon production. Macrofaunal community uptake was responsible for most of the C processing in the inner and middle parts of the fjord (&gt; 45%) while dissolved inorganic carbon was the dominant repository of processed C near the fjord mouth and on the continental shelf (&gt; 80%). The inner parts of Andvord Bay are hotspots of benthic C‐cycling and metabolism, in addition to biodiversity. Ongoing climate warming is likely to negatively impact these inner‐fjord hotspots by increasing meltwater input and sedimentation disturbance, yielding a reduction in the input and recycling of labile detritus at the seafloor in the inner‐middle fjord.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"53 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ocean conditions influence the quality of recruiting benthic marine invertebrate larvae—Insights from fatty acids","authors":"Minna Hiltunen, Michael Thomas, Alan L. Shanks, Aaron W. E. Galloway","doi":"10.1002/lno.12702","DOIUrl":"https://doi.org/10.1002/lno.12702","url":null,"abstract":"Many marine benthic invertebrates have a pelagic life stage, during which larvae need to accumulate enough reserves to complete metamorphosis to a settled benthic juvenile. Currently, very little is known about how ocean conditions affect quality of the larvae. We studied this for three settlement seasons (2017–2019) by collecting returning Dungeness crab (<jats:italic>Metacarcinus magister</jats:italic>) megalopae at the Oregon coast and analyzing them for fatty acid biomarkers. We found that the larvae are omnivorous and have versatile diets. The daily larval abundance was positively correlated with larval quality. Despite the relatively high day‐to‐day variation, we found pronounced seasonal and inter‐annual differences in the body condition (size and total fatty acid content) and biomarker composition of megalopae. Especially, the early season recruits of 2017 had lower content of lipids and polyunsaturated fatty acids known to be beneficial to crustaceans. This is likely related to lingering effects of the eastern Pacific marine heat wave (2014–2016) on pelagic communities. The larvae were rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) with lower levels in benthic juveniles, indicating an ontogenetic diet shift and likely lower availability of DHA and EPA in the benthic environment. The pulsed megalopa recruitment may provide substantial carbon and lipid inputs to the nearshore ecosystem as a form of pelagic subsidy. Our results reveal that ocean conditions may have an effect on the quality of returning larvae, which likely influence their recruitment performance and early juvenile success, and thus potentially also the population size and commercial catch 4 yr later.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"41 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142360483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hot spots drive uptake and short-term processing of organic and inorganic carbon and nitrogen in intertidal sediments","authors":"Philip M. Riekenberg,&nbsp;Bradley D. Eyre,&nbsp;Marcel T. J. van der Meer,&nbsp;Joanne M. Oakes","doi":"10.1002/lno.12670","DOIUrl":"10.1002/lno.12670","url":null,"abstract":"<p>This study uses dual-labeled (¹³C and ¹⁵N) stable isotope applications to examine microbial uptake and short-term processing of carbon (C) and nitrogen (N) from organic and inorganic compounds in subtropical intertidal sediment. Four treatment applications were applied: (1) algal dissolved organic matter (DOM), (2) amino acid mixture, (3) glucose and <span></span><math>\u0000 <mrow>\u0000 <msubsup>\u0000 <mi>NH</mi>\u0000 <mn>4</mn>\u0000 <mo>+</mo>\u0000 </msubsup>\u0000 </mrow></math>, and (4) NaHCO₃ and <span></span><math>\u0000 <mrow>\u0000 <msubsup>\u0000 <mi>NH</mi>\u0000 <mn>4</mn>\u0000 <mo>+</mo>\u0000 </msubsup>\u0000 </mrow></math> to assess bioavailability effects on processing (1 vs. 2) and short-term processing for OM fixed via microphytobenthos only (pennate diatom dominated) (4) vs. material taken up by the entire microbial community (3) across 24 h. ¹³C from algal-DOM was preferentially used by the microbial community vs. ¹⁵N. At 24 h more ¹³C from algal-DOM remained in microbial biomass indicating use of labeled precursor molecules to form biomass. Conversely, ¹³C from the amino acid treatment was not incorporated into biomass and was either rapidly respired to DIC or discarded as the in situ microbial community preferentially used and retained ¹⁵N from amino acids. Short-term export of ¹³C as CO₂ from glucose was lower than from microphytobenthos-C, while retention of ¹⁵N from <span></span><math>\u0000 <mrow>\u0000 <msubsup>\u0000 <mi>NH</mi>\u0000 <mn>4</mn>\u0000 <mo>+</mo>\u0000 </msubsup>\u0000 </mrow></math> was similar between treatments (3 and 4) despite doubling the application N concentration, suggesting potentially higher glucose-stimulated ¹⁵N export via nitrification–denitrification that was not confirmed via flux measurements in this study. Despite careful site selection for similar tidal exposure and sediment types among the three estuaries, the uptake and processing of labeled substrate varied substantially between replicates and sites which challenged traditional statistical analysis. Disproportionate processing of substrates occurring in sediment hotspots of microbial activity can cause variability spanning orders of magnitude which was found to be widespread through comparison of our results against 19 previous studies in intertidal settings. Development of robust analytical techniques to handle variability from abiotic and biotic factors will allow greater clarity surrounding in situ biogeochemical processing in intertidal environments.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2243-2262"},"PeriodicalIF":3.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142325586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Connectivity between Siberian river runoff and the lower limb of the Atlantic Meridional Overturning Circulation","authors":"Caroline V. B. Gjelstrup, Paul G. Myers, Craig M. Lee, Kumiko Azetsu‐Scott, Colin A. Stedmon","doi":"10.1002/lno.12696","DOIUrl":"https://doi.org/10.1002/lno.12696","url":null,"abstract":"Freshwater from the Arctic participates in the globally important Atlantic Meridional Overturning Circulation (AMOC). We use high‐resolution, in situ observations of dissolved organic matter (DOM) fluorescence to trace the origins of freshwater and organic carbon in the densest component of the AMOC, namely Denmark Strait Overflow Water (DSOW). We find a distinct terrestrial DOM signal in DSOW and trace it upstream to the Siberian shelves in the Arctic Ocean. This implies a riverine origin of freshwater in DSOW. We estimate that the Siberian Shelf water contribution constitutes approximately 1% of DSOW. Ocean circulation modeling confirms the inferred pathway and highlights Denmark Strait as an important location for the entrainment of the riverine signal into DSOW. Our proposed method can be deployed on a range of observing systems to elucidate freshwater dispersion across the Arctic and subarctic, thereby contributing to the broader discussion on freshwater impacts and organic carbon sequestration in the AMOC.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"14 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142325585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonality of zooplankton active flux in subtropical waters","authors":"Santiago Hernández‐León, Airam Sarmiento‐Lezcano, María Couret, Laia Armengol, Ione Medina‐Suárez, Effrosyni Fatira, Víctor Tuset, Abdallahi Limam, Antonio Sánchez Díez, Javier Díaz‐Pérez, José María Landeira","doi":"10.1002/lno.12689","DOIUrl":"https://doi.org/10.1002/lno.12689","url":null,"abstract":"The biological carbon pump (BCP) is the mechanism by which the ocean transports organic matter below the mixed layer, exporting or sequestering it for years to millennia. Physical transport of dissolved and particulate organic carbon, the sinking of particles, and the carbon transported by diel and seasonal vertical migrants are the three main mechanisms of the BCP. In the study of active flux, seasonality is almost unknown and changes in ocean productivity during the annual cycle could promote differences in this transport. Here, we show the results of a cruise performed during spring in the Canary Current System, where we studied zooplankton active flux in two transects from the coastal zone off Northwest Africa toward the ocean. We measured biomass and the enzymatic activity of the electron transfer system (ETS) as a proxy for respiration in the water column down to a depth of 900 m. Compared with a previous survey during fall, we found higher values of specific ETS activity in the mesopelagic zone, promoting a higher active flux. Our results showed that the seasonality of active flux is driven not only by differences in biomass but also by differences in respiration rates in the mesopelagic zone, mainly due to differences in zooplankton body size. A review of the zooplankton active flux values around the Canary Islands showed a fourfold increase during spring compared with other seasons. This small window of higher flux should be considered in models of active carbon export in the ocean.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"35 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142317585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantifying bivalve phytoplankton depletion in a eutrophic system: an integrated approach","authors":"Daniel Taylor,&nbsp;Hans Jakobsen,&nbsp;Maren Moltke Lyngsgaard,&nbsp;Miroslaw Darecki,&nbsp;Mortimer Werther,&nbsp;Marie Maar,&nbsp;Camille Saurel","doi":"10.1002/lno.12680","DOIUrl":"10.1002/lno.12680","url":null,"abstract":"<p>The removal of organic particulate matter, predominantly phytoplankton, in eutrophic coastal seas and estuaries is considered an ecosystem service performed by large bivalve assemblages. Mussel farming has been proposed as a measure to mitigate eutrophication, as filtration directly reduces the concentration of chlorophyll <i>a</i> (Chl <i>a</i>), a primary ecological indicator. Seston depletion is typically assessed by in situ investigation, which generally lacks spatiotemporal coverage of features relative to greater ecosystem dynamics. To assess the scale and structure of this service, the present study couples multiple measurement approaches, including moored stations, synoptic transect surveys, flow cytometry, a preliminary drone survey technique, and satellite remote sensing within and around a large mussel farm. Significant depletion patterns were observed with all methods, and mixing gradients could be detected hundreds of meters beyond the farm, with repeatable patterns but distinct findings between methods. The intensity of the depletion signal was correlated with mussel biomass loads, ambient conditions, and hydrodynamic regimes, ranging from 5% to 91% relative Chl <i>a</i> depletion and Secchi depth increases of up to 2 m. Changes in particle size distributions were impacted in all downstream areas, as well as phytoplankton diversity. Observed depletion gradients with satellite imagery were consistent with other measurements and can be used to complement in situ field measurements. The findings of this study, will inform carrying capacity assessments, farm configuration, and development of impact assessment programs on seston removal for bivalve aquaculture.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2436-2452"},"PeriodicalIF":3.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12680","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142275567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"The interaction between vegetation patchiness and tidal flows in a shortleaf seagrass meadow","authors":"Tiago D. da Silva,&nbsp;Julia C. Mullarney,&nbsp;Conrad A. Pilditch,&nbsp;Giovanni Coco","doi":"10.1002/lno.12679","DOIUrl":"10.1002/lno.12679","url":null,"abstract":"<p>Seagrasses are critical coastal habitats that provide numerous ecosystem services. The inherent patchiness within meadows exerts a significant influence on the flow-vegetation interaction, which, in turn, affects the array of services provided by these environments. We present field observations of vegetation distribution and hydrodynamic measurements within and surrounding an approximately 2 m diameter gap (bare sediment) in a fragmented seagrass meadow. We show that variability in mean flows and turbulence is correlated with meadow structure at small (O (10⁰ m)) and large (O (10² m)) spatial scales. Our observations reveal that bare gaps within seagrass meadows lead to faster flows and lower bed elevations. Despite slower flow speeds above the dense seagrass adjacent to the gap, the rates of dissipation of turbulent energy above the vegetation are typically around an order of magnitude larger than above the bare bed. Associated with this enhanced dissipation of turbulent energy, we observed a dominance of down-deceleration events promoting fluid exchange and mixing and driving mass flux into the canopy. Analysis of directional variograms demonstrates that the major continuity axis within NDVI (normalized difference vegetation index) imagery (used as a proxy for vegetation biomass) coincides with the major axis of flow on both gap and meadow scales. Conversely, along the axis of minor flow variance, vegetation remains dense and exhibits greater uniformity. These findings indicate a feedback mechanism between seagrass meadow patchiness and spatial structure through flow modification, which may be beneficial for plant development.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2422-2435"},"PeriodicalIF":3.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12679","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142275555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Source partitioning of dissolved inorganic carbon addition to Pacific Winter Water in the western Arctic Ocean","authors":"Zhangxian Ouyang, Amane Fujiwara, Shigeto Nishino, Akihiko Murata, Qian Li, Mariko Hatta, Yun Li, Najid Hussain, Wei‐Jun Cai","doi":"10.1002/lno.12684","DOIUrl":"https://doi.org/10.1002/lno.12684","url":null,"abstract":"Pacific Winter Water (PWW) with high dissolved inorganic carbon (DIC) is the key water mass in which subsurface acidification occurs in the western Arctic Ocean. To investigate and partition carbon sources added to PWW across the Chukchi shelf to the adjacent Canada Basin, we investigated the distributions of DIC and its stable isotope (δ<jats:sup>13</jats:sup>C‐DIC) with other hydrographic and biogeochemical parameters during the Mirai cruise in the late summer of 2021. Using a four‐end‐member mixing model, we deciphered the water masses and separated DIC changes induced by biological processes from those induced by conservative mixing. We demonstrated that DIC dynamics in PWW were mainly controlled by the biological decomposition of organic carbon (OC). A mass balance model analysis of DIC and δ<jats:sup>13</jats:sup>C‐DIC suggested that the apparent δ<jats:sup>13</jats:sup>C signature of the respired organic carbon (δ<jats:sup>13</jats:sup>C<jats:sub>OCx</jats:sub>) within PWW was −22.2‰ ± 1.1‰ on the shelf and −25.6‰ ± 1.6‰ in the basin. Therefore, we concluded that marine‐origin OC was the dominant carbon source that was decomposed in the Chukchi shelf bottom water, while respired terrestrial‐origin carbon made a major contribution to DIC pool in the basin PWW. We proposed that terrestrial OC from the Chukchi and Beaufort coastal seas could be an important carbon source, which was associated with winter water formation on the shelves and influenced by Beaufort Gyre state shift and circulation changes. This unconventional finding has important ramifications for the prediction of the future state of ocean acidification in the western Arctic Ocean.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"11 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142236586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ecological patterns of benthic foraminiferal communities driven by seasonal and spatial environmental gradients in an Arctic fjord","authors":"Corentin Guilhermic, Maria Pia Nardelli, Aurélia Mouret, Antonio Pusceddu, Agnès Baltzer, Hélène Howa","doi":"10.1002/lno.12691","DOIUrl":"https://doi.org/10.1002/lno.12691","url":null,"abstract":"Arctic fjords, being transitional areas between glacier‐covered land and the ocean, are characterized by strong environmental gradients. The seasonal melting of glaciers generates strong turbidity and primary production antagonist gradients, which can affect benthic habitats. Two sampling campaigns were carried out in Kongsfjorden (Svalbard, Arctic Ocean) in May and August 2021 to investigate seasonal changes in benthic foraminifera spatial distribution and ecosystem functioning along a longitudinal transect of 10 km from the Kronebreen tidewater glacier front. Concurrently, organic matter quantity and biochemical composition, sediment grain size, and physical parameters of the water masses were investigated as possible driving factors of benthic ecosystem responses. In a previous study, three statistically determined foraminiferal biozonations (glacier proximal, medial, and distal) were observed on the basis of their species content within the closest 10 km from the glacier front, presenting similar assemblages in both seasons. Our results indicate that foraminiferal distribution at the local scale is mainly driven by physical and geochemical gradients induced by melting waters and sediment discharges from the tidewater glacier occurring during summer. Due to the climate change, the melting season is expected to last longer and increasing global temperature will much probably accelerate the melting processes. Our findings strongly support the use of foraminifera as bioindicators to monitor the effects of ongoing climate change on the benthic ecosystems of Arctic fjords and, accessorily, as proxies for reconstructing glacier front positions in the recent past.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"7 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142236293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal trends in Subantarctic plankton δ13C and δ15N are driven by phytoplankton dynamics and nutrient preference","authors":"Luca Stirnimann, Thomas G. Bornman, Hans M. Verheye, Sarah E. Fawcett","doi":"10.1002/lno.12685","DOIUrl":"https://doi.org/10.1002/lno.12685","url":null,"abstract":"The carbon and nitrogen isotope ratios (δ<jats:sup>13</jats:sup>C and δ<jats:sup>15</jats:sup>N) of marine plankton record biogeochemical processes at the base of the food web. In the Southern Ocean, such data, predominantly from summer, have been used to infer surface CO<jats:sub>2</jats:sub> concentrations and the potential for biological carbon export. However, variability in plankton δ<jats:sup>13</jats:sup>C and δ<jats:sup>15</jats:sup>N remains poorly understood, with the lack of seasonal measurements from the Southern Ocean emerging as a particular limitation. Here, we investigate the δ<jats:sup>13</jats:sup>C and δ<jats:sup>15</jats:sup>N of suspended particulate matter (SPM) and zooplankton collected from the Subantarctic Ocean in winter, summer, and autumn. The low summertime δ<jats:sup>13</jats:sup>C<jats:sub>SPM</jats:sub> and δ<jats:sup>15</jats:sup>N<jats:sub>SPM</jats:sub> can be explained by strong diatom reliance on nitrate supplied during winter mixing. A subsequent increase in δ<jats:sup>13</jats:sup>C<jats:sub>SPM</jats:sub> and decrease in δ<jats:sup>15</jats:sup>N<jats:sub>SPM</jats:sub> by autumn is consistent with iron limitation in mid‐ to late‐summer favoring diatom succession by nano‐phytoplankton that consume mainly recycled ammonium. By winter, bacterial decomposition of biomass outpaces new biomass production, decreasing δ<jats:sup>13</jats:sup>C<jats:sub>SPM</jats:sub> and raising δ<jats:sup>15</jats:sup>N<jats:sub>SPM</jats:sub>. The δ<jats:sup>13</jats:sup>C and δ<jats:sup>15</jats:sup>N of contemporaneously sampled zooplankton generally reflect the variability in δ<jats:sup>13</jats:sup>C<jats:sub>SPM</jats:sub> and δ<jats:sup>15</jats:sup>N<jats:sub>SPM</jats:sub>, with one autumn mismatch suggesting that in situ SPM is not always the dominant zooplankton food source. Our study shows how nutrient dynamics and phytoplankton community composition shape the seasonality of the Subantarctic's isotopic baselines, emphasizing a key role for iron availability. This work has implications for isotope‐based food web studies, highlighting the need to consider seasonal variability in δ<jats:sup>13</jats:sup>C<jats:sub>SPM</jats:sub> and δ<jats:sup>15</jats:sup>N<jats:sub>SPM</jats:sub>, as well as the different turnover times of phytoplankton (i.e., SPM) vs. zooplankton biomass.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"332 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142245416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}