Journal of Marine Systems最新文献

{"title":"Spring plankton energy content by size classes in two contrasting environments of a high latitude ecosystem: The Beagle Channel","authors":"Daniel O. Bruno ,&nbsp;Constanza Valencia-Carrasco ,&nbsp;María A. Paci ,&nbsp;Ezequiel Leonarduzzi ,&nbsp;Leonardo Castro ,&nbsp;Luciana Riccialdelli ,&nbsp;Clara M. Iachetti ,&nbsp;Andreana Cadaillon ,&nbsp;Ricardo Giesecke ,&nbsp;Irene R. Schloss ,&nbsp;Carla F. Berghoff ,&nbsp;Jacobo Martín ,&nbsp;Mariano Diez ,&nbsp;Ariel Cabreira ,&nbsp;María L. Presta ,&nbsp;Fabiana L. Capitanio ,&nbsp;Claudia C. Boy","doi":"10.1016/j.jmarsys.2023.103876","DOIUrl":"10.1016/j.jmarsys.2023.103876","url":null,"abstract":"<div><p><span><span>This study aimed to characterize the energy density (ED), using a micro-bomb calorimeter, of different plankton fractions: </span>microplankton (23–67 μm; including </span>phytoplankton<span><span><span> and small heterotrophs), microzooplankton (67–200 μm), mesozooplankton (200–2000 μm), and fish larvae, at two micro-basins separated by a sill (the Mackinlay Strait) and with different topography and hydrography in the </span>Beagle Channel. For that purpose, two sampling sites (west (F1) and east (F2) of the Mackinlay Strait), two strata (surface and near-bottom layers) and </span>diel variations<span> (diurnal and nocturnal hours) were considered. Also, patterns among plankton fractions' ED and water properties (temperature, salinity, total alkalinity, pH, and dissolved inorganic carbon) were analysed by redundancy analysis. ED values of the plankton fractions differed among sites, strata and sampling time. Surface microplankton at F1 showed higher ED than at F2. A trend of higher ED values of microzooplankton was observed at the surface than at the near-bottom layer of F1, whereas similar values between both layers (surface and near-bottom) were observed at F2. Mesozooplankton was the plankton fraction that most contributed to the site-depth-time of sampling differences in ED. For instance, the ED of mesozooplankton was higher at the near-bottom than the surface layer during diurnal and nocturnal hours of F1, while the opposite was observed for nocturnal hours at F2. ED of microplankton was associated with conditions of lower values of total alkalinity and salinity but higher temperature, whereas microzooplankton was associated with the opposite conditions. The ED of mesozooplankton was associated with conditions of higher pH and diurnal hours. It is proposed that the energy flow patterns of the plankton community in the Beagle Channel differ in the two micro-basins formed by the MacKinlay Strait (east and west of it), with lower and more homogeneous ED values between fractions and layers east of the Strait characterised by depleted-in-nutrients waters.</span></span></p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42223514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Source characterization of dissolved organic matter in the eastern Beagle Channel from a spring situation","authors":"Andrea Malits ,&nbsp;Chiara Monforte ,&nbsp;Clara Iachetti ,&nbsp;Marina Gerea ,&nbsp;Maité Latorre","doi":"10.1016/j.jmarsys.2023.103863","DOIUrl":"10.1016/j.jmarsys.2023.103863","url":null,"abstract":"<div><p><span>Dissolved organic matter (DOM) was analyzed by its optical and fluorescent properties in order to study its distribution, source and transformation in relation to microbial abundances, chlorophyll </span><em>a</em><span>nd physicochemical gradients along a transect in the eastern Beagle Channel<span><span> (BC) during austral spring 2019. Moreover, DOM evolution was followed during three tidal cycles<span><span> in two fixed stations (F1, F2) separated by the Mackinlay Strait, a hydrographic frontier between water masses under stronger continental influence (inner sector) and that of less modified Sub-Antarctic waters (outer sector). The fluorescence signals of protein- and humic-like compounds were used as a proxy for labile and non-labile material, respectively, while the concentration of nano-, pico- and virioplankton populations, chlorophyll-a (Chl-a) and </span>dissolved organic carbon (DOC) were used as a proxy for biological activity. Moreover, several spectroscopic indices, such as the indicator of microbially produced DOM (BIX), the Freshness index (FIX), an indicator of </span></span>molecular weight, the Slope Ratio (SR) and an indicator of chromophoric DOM (CDOM), were used to trace the quality and origin of DOM. Chl-a concentration was generally low in the sampling area (&lt; 1 μg L</span></span>⁻¹<span><span>) but increased towards the end of the campaign and especially during the visit of F1 along with the concentration of picoeukaryotes and the protein-like fluorophores evidencing the onset of a bloom event. Protein-like fluorophores peaked in the </span>euphotic zone<span> of the inner sector of the BC while humic-like material of terrestrial origin was homogeneously distributed throughout the water column and showed a decreasing gradient towards the outer sector and Atlantic waters. Furthermore, the inner sector was characterized by higher amounts of CDOM, high molecular weight material and more recalcitrant DOM. Accumulation of autochthonous humic-like material in bottom waters of the inner sector along with enhanced values of FIX and BIX preceded by colored organic material suggest an efficient functioning of the microbial carbon pump fueled by terrestrial DOM sources in these waters.</span></span></p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49658136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Daily variability of pelagic metabolism in a subtropical lagoonal estuary","authors":"Luís Henrique Bordin ,&nbsp;Eunice Da C. Machado ,&nbsp;Carlos R.B. Mendes ,&nbsp;Elisa H.L. Fernandes ,&nbsp;Maurício G. Camargo ,&nbsp;Rodrigo Kerr ,&nbsp;Carlos A. Schettini","doi":"10.1016/j.jmarsys.2023.103861","DOIUrl":"10.1016/j.jmarsys.2023.103861","url":null,"abstract":"<div><p><span><span><span>The influence of meteoceanographic variability on pelagic ecosystem metabolism was evaluated during late austral summer (from February to March 2021), through a daily survey for one month, at two channel sites in the subtropical Patos Lagoon </span>Estuary, Brazil — the largest choked (restricted connection to the sea) </span>coastal lagoon of South America. Heterotrophic predominance prevails in the studied area, with an overall mean of −205 ± 143 mmol O</span>₂ m−² d⁻¹, with 78 ± 67 mmol O₂ m⁻² d⁻¹ from gross primary production (GPP) and 285 ± 178 mmol O₂ m⁻² d⁻¹<span> from respiration (R). Generalized additive models were used to identify the most relevant driving forces for GPP, which were nitrate, salinity, chlorophyll-</span><em>a</em> (chl-<em>a</em><span><span>), wind speed and direction, water flow rate, silicate, and </span>turbidity. The main driving mechanisms for R were photosynthetically active radiation, temperature, wind speed, chl-</span><em>a</em><span><span>, turbidity, and nitrate. GPP was potentially co-limited by dissolved inorganic nitrogen (very low nitrogen to phosphorus ratio, N:P = 3.1 ± 2.0) throughout the period and by light in some events due to material </span>resuspension<span><span> from the bottom by wind-induced salt-wedge intrusions. Evidence of intrusions of Plata Plume Water into the estuary were observed, likely contributing as a key factor to local biogeochemistry<span>. The main phytoplankton groups, in decreasing order of abundance, were diatoms, cryptophytes, and </span></span>cyanobacteria, with their variability being controlled mainly by wind-induced salinity changes. Diatoms responded as the main contributor to metabolic rates, water carbon dioxide (CO</span></span>₂), carbon dioxide partial pressure (<em>p</em>CO₂), and water-air CO₂ fluxes (FCO₂<span>) by its higher biomass and uptake of total inorganic carbon. Inlet (70%) and sea-exposed (95%) stations behaved mainly as net CO</span>₂ sinks from the atmosphere during most of the study period (−7.9 ± 30.6 mmol C m⁻² d⁻¹). The inlet inner station had a median FCO₂ of −9.8 and an average of 4.4 ± 41.2 mmol C m⁻² d⁻¹, while the sea-exposed station had −17.0 and −15.4 ± 17.3 mmol C m⁻² d⁻¹, respectively. Although total inorganic carbon and chl-<em>a</em><span> were negatively correlated, which indicates carbon assimilation by primary production, no correlation was observed between metabolic rates and FCO</span>₂<span><span><span>. These results suggest the need for additional investigation into the driving factors and/or sources of carbon species in the Patos Lagoon Estuary to better understand the role of aquatic ecosystem metabolism in the </span>carbon budget. Finally, the daily investi","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41875201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"National Marine Sanctuaries capture enhanced abundance and diversity of the California Current Ecosystem avifauna","authors":"Tamara M. Russell ,&nbsp;Angela R. Szesciorka ,&nbsp;Trevor W. Joyce ,&nbsp;David G. Ainley ,&nbsp;Lisa T. Ballance","doi":"10.1016/j.jmarsys.2023.103887","DOIUrl":"10.1016/j.jmarsys.2023.103887","url":null,"abstract":"<div><p>Quantifying the spatial patterns of marine predators, such as seabirds, reveals areas of ecological importance and associated food web characteristics, upon which marine conservation and management plans can be based. Owing to high productivity, the California Current Ecosystem (CCE) harbors an abundant and diverse avifauna comprised of resident and migratory species. With a goal of protecting habitats in three biogeographic regions — North, Central, and South CCE — a network of marine protected areas have been designated, including five National Marine Sanctuaries (NMS). Using an extensive at-sea survey dataset (1980 to 2017), we characterize spatial patterns of seabirds, and compare mean relative abundance, diversity, and community composition both within and outside the NMSs. We found that within the CCE, seabird abundance and diversity increase linearly from south to north (R² = 0.54 and R² = 0.55, respectively) and decrease linearly with distance from the coast (R² = 0.16 and R² = 0.23, respectively). The avifauna of the North and South regions are the most distinct, with the Central region being transitional between the two. The CCE avifauna shows limited overall diversity, with just 10 species contributing &gt;93% of abundance totals. In addition, certain foraging guilds and prey preference groups were dominant: pursuit-feeding and piscivorous species in the North and surface feeding generalists in the South. Overall, seabird relative abundance and diversity are higher within NMS boundaries compared to outside. Although relative abundance and diversity of seabirds within NMSs were broadly representative of corresponding biogeographic regions, the overall NMS network captures a range of distinct seabird communities. The analysis of this extensive dataset provides a better understanding of seabird spatial patterns and their ecological roles within different regions, thus facilitating more effective, adaptive management of CCE biotic resources.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44463924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Macroinvertebrates food web and trophic relations of a peri urban mangrove system in a semi-arid region, Gulf of California, México","authors":"Diana Medina-Contreras,&nbsp;Alberto Sánchez,&nbsp;Fernando Arenas","doi":"10.1016/j.jmarsys.2023.103864","DOIUrl":"10.1016/j.jmarsys.2023.103864","url":null,"abstract":"<div><p><span><span>Despite being structurally limited due to their latitudinal distribution and local climatic conditions, mangroves of the southwest Gulf of California present productivity and carbon storage<span> rates similar or higher than that of tropical mangroves. Despite the importance of their contribution to marine and atmospheric dynamics, few studies exist focused on food web structures in such ecosystems. In order to analyze </span></span>trophic structure<span> and dynamics of a mangrove system in the Gulf of California, the isotopic composition, trophic position, isotopic niche, and trophic pathways were studied using the statistical packages TrophicPosition (TP), SIBER, and Simmr. Isotopic values of C and N were obtained for 244 samples of carbon sources and invertebrate consumers which were classified into six trophic guilds. The δ</span></span>¹³C values of carbon sources varied from −30.7 (<span><em>Rhizophora mangle</em></span>) to −15.6‰ (<span><em>Caulerpa</em><em> sertularioides</em></span>) and for consumers varied from −22.3‰ (<em>Aratus</em> sp) to −13.2 (<span><em>Callinectes</em><em> arcuatus</em></span>). Herbivores generally had depleted ¹³<span>C values related to those of the other trophic guilds. The macroinvertebrate<span> communities' mean TP values (2.6: 2.0–3.5) indicate a composition of primary and secondary consumers, exhibiting a clear separation between trophic guilds. Isotopic niche width (TA) of the community (14.1) suggests niche segregation, specially between herbivores and deposit feeders<span><span>. Those trophic guilds are the first consumers and intermediaries for two distinct trophic pathways, one derived from detritus<span><span> and mangroves and the other from microphytobenthos (MPB). Three groups of primary sources were identified contributing &gt;70% of carbon, representing the primary base of several trophic pathways that sustain different consumer guilds: (1) mangrove-detritus, herbivorous crabs, (2) MPB-Sedimentary </span>organic carbon, supporting mainly deposit feeders and </span></span>filter feeders<span>, and (3) Seston-MPB, supporting mainly omnivorous shrimp. Overall, the identified pathways potentially sustain fish communities, which due to their movement export energy from mangroves to coastal food webs.</span></span></span></span></p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46442617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bio-optical properties of algal communities in Antarctic pack ice during spring","authors":"Laura A. Dalman ,&nbsp;Christina Schallenberg ,&nbsp;Alexander D. Fraser ,&nbsp;Sophie Bestley ,&nbsp;Eun Jin Yang ,&nbsp;Lesley Clementson ,&nbsp;Klaus M. Meiners","doi":"10.1016/j.jmarsys.2023.103890","DOIUrl":"10.1016/j.jmarsys.2023.103890","url":null,"abstract":"<div><p>Microalgae use Antarctic sea ice as habitat and accumulate in spring, leading to significant early-season production in Southern Ocean ecosystems. As key contributors to the marine food web and carbon fixation within the Antarctic pack-ice zone, ice algae depend on the light environment and their adaptability to irradiance extremes. This study examines spectral ice algal and non-algal particulate absorption coefficients, pigments, and community composition in pack-ice cores sampled off East Antarctica and in the Weddell Sea during the winter-spring transitions in 2012 and 2013, respectively. Our results show that ice algae dominated particulate absorption in pack ice in both regions. From high- to low-light exposure in both East Antarctica and Weddell Sea, biomass-specific absorption decreased, suggesting strong pigment packaging with depth towards the ice-water interface. Ice algae also showed increased production of photoprotective pigments in the surface in comparison to the bottom of the sea ice, with flagellates being more dominant in the surface ice sections. Our results indicate species-specific light-acclimation and photoprotection through the ice profiles, and highlight the role of light conditions in influencing pigment production and shifts in community composition.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48789935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spring phytoplankton distributions and primary productivity in waters off northern Norway","authors":"R. Meng ,&nbsp;W.O. Smith Jr ,&nbsp;S.L. Basedow","doi":"10.1016/j.jmarsys.2023.103891","DOIUrl":"10.1016/j.jmarsys.2023.103891","url":null,"abstract":"<div><p>The distributions of phytoplankton, zooplankton and hydrographic features off the coast of northern Norway were assessed in late April – early May 2019 using ship-based observations (CTD casts and Moving Vessel Profilers) and autonomous vehicles. A satellite chlorophyll climatology was generated to place our in-situ observations within a longer temporal sequence. Substantial spatial and temporal variability on all scales was observed in both the observations and climatology. Spring phytoplankton accumulation usually is initiated in the south on the continental shelf, and advanced in a northerly direction through time. Accumulations in the surface layer of deeper waters off the continental shelf occurred 2–3 weeks later than those on the shelf. During our survey, primary productivity was greatest in offshore waters where nutrients were not depleted and exceeded 2 g C m⁻² d⁻¹. The greatest <em>Calanus finmarchicus</em> abundances were associated with low chlorophyll concentrations, suggesting a major impact of grazing on phytoplankton biomass, but estimates of phytoplankton growth and zooplankton removal suggested that <em>Calanus</em> was responsible for a variable fraction (3–69%) of the daily chlorophyll changes. Vertical changes in chlorophyll were related to physical features during some transects, but to grazing and sinking in others. Understanding the spatial and temporal variations of the coupling of phytoplankton to zooplankton is essential to effective management of this important commercial species in Norwegian waters.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49194531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sinking rates of phytoplankton in response to cell size and carbon biomass: A case study in the northeastern South China Sea","authors":"Yingjie Mao ,&nbsp;Jun Sun ,&nbsp;Congcong Guo ,&nbsp;Shuang Yang ,&nbsp;Yuqiu Wei","doi":"10.1016/j.jmarsys.2023.103885","DOIUrl":"10.1016/j.jmarsys.2023.103885","url":null,"abstract":"<div><p><span>The direct sinking behavior of phytoplankton<span> is an important way for marine carbon pumping and an accurate estimation of the sinking rates of phytoplankton is necessary for a comprehensive understanding of the ocean carbon cycle. After comparing all the methods of studying cell sinking behavior for nearly 40 years, we gave a reason for using the SETCOL method. To study the effect of Kuroshio Current (KC), and Tropical Storms (TS) on the sinking rates, we analyzed 672 samples collected from the northeastern part of the South China Sea (neSCS), where the marine environments were highly diverse. KC could increase the total sinking rates, TS transit caused the phytoplankton to sink slower. The effect of nutrients on the sinking rates was minimal in the absence of abnormal sea conditions. Chl-</span></span><em>a</em><span> concentrations showed negative regulation on the sinking rates of KC-affected stations. Nutrients positively regulated the TS-affected stations, and dinoflagellates abundance has negative feedback regulation on the sinking rates. In addition, long rod-shaped diatoms sank fastest and the elliptical dinoflagellates sank significantly slower after being affected by TS. Under the influence of KC, the cell with an equivalent sphere diameter (ESD) of around 10–12 μm, and carbon content per unit volume (CCV) of about 0.5 Pg C cell</span>⁻¹ μm⁻³ sank fastest. TS resulted in the fastest sinking rates of cells at 15–17 μm. The sinking rates correlated extremely well with ESD in normal sea conditions in a positive linear fashion and slowed down with increasing CCV. We thus suggested that the sinking rates of cells under different marine conditions was closely related to cell size and carbon biomass. In future oceans, it is possible that most phytoplankton in the euphotic layer will be able to maintain themselves in an optimal growth environment consistently by reducing its size or increasing the proportion of biological carbon content in cells.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44437360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iron geochemistry in surface sediments of the subtropical northern South China Sea and a comparison with the temperate East China Sea","authors":"Ying-Jian Han,&nbsp;Jian-Hua Ren,&nbsp;Qing-Qing Li,&nbsp;Wen-Xuan Sun,&nbsp;Tie Li,&nbsp;Mao-Xu Zhu","doi":"10.1016/j.jmarsys.2023.103878","DOIUrl":"10.1016/j.jmarsys.2023.103878","url":null,"abstract":"<div><p>The influence of differential chemical weathering intensity on the contents and spatial distribution of highly reactive iron (Fe_HR<span>) in the marginal sea<span> sediments is not well documented. Here, we used sequential extractions to quantify various Fe pools in offshore surface sediments of the northern South China Sea (nSCS), which receives multiple fluvial sediments with distinct chemical weathering intensity, and then to unravel whether and if so, to what extent, the contents and spatial distributions of Fe</span></span>_HR are linked to chemical index of alternation (CIA) of the sediments. Our results show that, despite the inputs of Fe_HR-rich, highly chemically weathered fluvial sediments, Fe_HR contents in offshore sediments of the nSCS are almost independent of the CIA values, and Fe_HR was not enriched relative to the global average of Fe_HR<span> in oxic sediments, probably due to effective trapping of Fe</span>_HR<span> in the estuary and dilution by moderately chemically weathered Taiwan-sourced sediments. Our results indicate that the signature of Fe</span>_HR enrichment previously observed in the offshore sediments, which are discharged from a highly chemically weathered mountainous island (Hainan Island) of the nSCS, becomes lost beyond the local zone around the island. Relative to the marginal sediments of the nSCS (water depth &lt;1000 m), the higher Fe_HR<span> contents in the deep-water sediments (water depth larger than 1000 m) can be attributed to higher smectite<span> contents, lower inorganic carbon contents, and low dilution by Taiwan-sourced fluvial material in the deep-water area. A comparison of the subtropical nSCS and the temperate East China Sea indicates that chemical weathering intensity is not the overarching factor governing Fe</span></span>_HR/Fe_T ratios in the two climatically different regions, though chemical weathering intensity along with depositional/diagenetic regimes is an important factor controlling the sizes and transformation of some specific Fe_HR pools.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47918387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plankton metabolic balance in the eastern Beagle Channel during spring","authors":"M.P. Latorre ,&nbsp;C.F. Berghoff ,&nbsp;R. Giesecke ,&nbsp;A. Malits ,&nbsp;G. Pizarro ,&nbsp;C.M. Iachetti ,&nbsp;J. Martin ,&nbsp;X. Flores-Melo ,&nbsp;M.N. Gil ,&nbsp;J.L. Iriarte ,&nbsp;I.R. Schloss","doi":"10.1016/j.jmarsys.2023.103882","DOIUrl":"10.1016/j.jmarsys.2023.103882","url":null,"abstract":"<div><p><span>Microbial community<span><span> metabolic balance (i.e., the ratio between photosynthesis and community respiration) is critical for assessing the strength of the biological carbon pump and its importance for the marine food web. This study aimed at characterizing the microbial community metabolic balance (hereinafter referred to as metabolic balance) in the Beagle Channel<span> (BC, 54°S, 68° W), a sub-Antarctic environment that connects the Pacific and Atlantic Oceans at the southernmost extreme of South America. During a binational Chilean-Argentinian cruise along the eastern BC in the austral spring (November 2019), oxygen production and consumption rates were estimated in vitro after 12-h light and dark incubations. Phytoplankton primary productivity was additionally assessed using in vivo active fluorescence techniques. Environmental conditions (temperature, </span></span>salinity<span>, nutrients, dissolved oxygen, carbonate system and light) and the composition of the plankton community (i.e., phytoplankton and bacteria) were analyzed to assess the factors controlling productivity in the BC. Finally, we explored the role of the microbial community metabolic balance in modulating CO</span></span></span>₂ uptake by means of high-resolution underway CO₂ fugacities (fCO₂). Results showed a highly dynamic and rapidly changing system, with gross primary production (GPP) rates presenting a west-east gradient, with minimum values in the western portion of the study area (0.63 ± 0.12 mmol O₂ m⁻³ d⁻¹) and maximum values towards the Atlantic (13.87 ± 2.00 mmol O₂ m⁻³ d⁻¹). Community respiration rates were high (mean: 2.81 mmol O₂ m⁻³ d⁻¹) and positively correlated with GPP. Although net community production (NCP) was relatively low (0.25–3.27 mmol O₂ m⁻³d⁻¹), the P:R ratio suggests the prevalence of autotrophic communities, dominated by chain forming diatoms, mainly in the eastern portion (NCP : 3.27 mmol O₂ m⁻³ d⁻¹). Thermohaline conditions played a key role in regulating the productive capacity of the BC and in the sea-air CO₂ exchange, except in the most productive stations, where biological production fueled fCO₂ dynamics.</p></div>","PeriodicalId":50150,"journal":{"name":"Journal of Marine Systems","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42657483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}