Deep-sea Research Part Ii-topical Studies in Oceanography最新文献

{"title":"Variability of bottom dissolved oxygen on the southern Senegalese shelf at intraseasonal to interannual time scales using a modelling approach","authors":"Abdoul Wahab Tall ,&nbsp;Vincent Echevin ,&nbsp;Xavier Capet ,&nbsp;Eric Machu","doi":"10.1016/j.dsr2.2025.105464","DOIUrl":"10.1016/j.dsr2.2025.105464","url":null,"abstract":"<div><div>Recent in-situ measurements on the west African continental shelf have shown that the bottom waters undergo episodic hypoxia and even anoxia. In this study, we investigate the variability of bottom dissolved oxygen (DO) over the southern Senegalese shelf at seasonal, intraseasonal and interannual time scales over the period 2015–2019 using a high-resolution (2 km) regional coupled dynamical-biogeochemical model. The model is forced by daily winds to represent synoptic variability during the upwelling-favourable cold season (November-May). Near-bottom DO evaluation using data from the Melax mooring located over the mid shelf indicates that the model represents well the seasonal and intraseasonal variability. A bottom DO budget shows that advection of deep, low-oxygenated waters over the shelf edge during the upwelling season generates a DO loss, which is overcompensated by ventilation of the entire shelf due to vertical mixing. Biogeochemical processes compensate this DO supply: DO is consumed by organic matter and zooplankton respiration, slightly compensated by regenerated and new primary production. Because of a sluggish shelf circulation during the summer season (July–September, JAS), oxygen concentration declines in parts of the outer shelf bottom layer, in spite of a weaker surface primary production and organic matter export than during the heart of the cold season (February–April, FMA). Analysis of the synoptic variability reveals the complexity of the DO response to the duration and intensity of upwelling and relaxation events, with the largest DO decrease of <span><math><mrow><mo>∼</mo><mn>110</mn><mi>μ</mi><mi>m</mi><mi>o</mi><mi>l</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub><msup><mrow><mi>L</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> associated with a strong upwelling event (cumulative upwelling index <span><math><mrow><mo>∼</mo><mn>2</mn><msup><mrow><mi>Nm</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mi>d</mi><mi>a</mi><mi>y</mi></mrow></math></span>) obtained in 2016. Year to year variability indicates two periods of enhanced hypoxia in FMA 2017 and JAS 2016 characterized by a high retention of bottom waters over the shelf.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105464"},"PeriodicalIF":2.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Arabian Sea high salinity core supplies oxygen to the Bay of Bengal","authors":"Anoop A. Nayak ,&nbsp;P.N. Vinayachandran ,&nbsp;Jenson V. George","doi":"10.1016/j.dsr2.2025.105477","DOIUrl":"10.1016/j.dsr2.2025.105477","url":null,"abstract":"<div><div>The oxygen minimum zone (OMZ) in the Bay of Bengal (BoB) is unique owing to its curious capability to maintain steady dissolved oxygen (DO) levels. In this study, we identify a process by which the oxygen is supplied to the BoB, using DO and microstructure profiles in the southern BoB and Argo profiles over the entire basin. A high salinity core (HSC) rich in DO is advected by the Summer Monsoon Current (SMC) into BoB. Vertical mixing driven by turbulent processes recharge DO concentration in thermocline above OMZ. Salt-fingering processes were active below the HSC and were observed to enhance the vertical mixing. HSC identified in the Argo data, also rich in oxygen, can be traced up to 19° N, confirming that HSC is a source of DO and potentially prevents OMZ from moving to the denitrification regime. This might be a potential oxygen source for the BoB OMZ in changing climate conditions.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105477"},"PeriodicalIF":2.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143679156","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":"How do macrobenthic-based indices respond to anthropogenic pressures? Insights from estuaries of the Persian Gulf and Gulf of Oman","authors":"Moslem Sharifinia ,&nbsp;Mohammadreza Taherizadeh ,&nbsp;Javid Imanpour Namin ,&nbsp;Ehsan Kamrani","doi":"10.1016/j.dsr2.2025.105481","DOIUrl":"10.1016/j.dsr2.2025.105481","url":null,"abstract":"<div><div>Coastal ecosystems are increasingly threatened by human activities, necessitating effective monitoring tools to assess their ecological health. This research examines the ecological conditions of three estuaries along the Persian Gulf and Gulf of Oman, focusing on the impacts of human activities over a one-year period by utilizing macrofauna as biological indicators. Samples of macrofauna and sediment were collected from nine distinct sites, reflecting a range of contamination levels from industrial wastewater and shrimp farming to relatively unaffected areas. A total of 165 macrobenthic taxa were identified across seven groups: Annelida and Mollusca each had 65 taxa, Arthropoda had 28, Echinodermata had 3, Hydrozoa had 2, and both Nemertea and Nematoda had 1 each. The most common group was Polychaeta, accounting for 37.57 % of the total, followed by Gastropoda at 22.42 %. The ecological condition and sediment quality were assessed using biotic and heavy metal indices, specifically the AMBI and the potential ecological risk index (PERI). The analysis revealed that industrial sewage and effluents from shrimp farming are significant pollution contributors in the Khamir and Tiyab estuaries, respectively, leading to notable declines in biodiversity indices (<em>P ≤</em> 0.05). The AMBI index exhibited a strong negative correlation with species richness and Shannon and Margalef indices, while positively correlating with total organic matter (TOM). Heavy metal concentrations were found to be elevated in contaminated sites, further indicating ecological stress. The results suggest that the AMBI index is a valuable tool for assessing coastal ecosystem conditions, effectively distinguishing between less affected and heavily impacted areas, and can support coastal monitoring efforts. Additionally, <em>Capitella capitata</em> and <em>Clymene robusta</em> showed resilience to pollution, while <em>Assiminea</em> sp. And <em>Littorina intermedia</em> were sensitive to environmental disturbances. These findings can inform more efficient and targeted management strategies for coastal areas, emphasizing the importance of monitoring heavy metal levels in maintaining ecological health.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105481"},"PeriodicalIF":2.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143838097","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":"Brought to the surface from obscurity: The distribution and biology of Coelorhinchus gilberti (Macrouridae, Gadiformes, Teleostei) off the Emperor Seamounts (Northwestern Pacific)","authors":"Nikolai B. Korostelev ,&nbsp;Igor V. Volvenko ,&nbsp;Igor V. Maltsev ,&nbsp;Alexei M. Orlov","doi":"10.1016/j.dsr2.2025.105461","DOIUrl":"10.1016/j.dsr2.2025.105461","url":null,"abstract":"<div><div><em>Coelorinchus gilberti</em> is a member of the grenadier family (Macrouridae) found off the Pacific coast of Japan (from Shikoku Island to Hokkaido Island), the Kyushu-Palau submarine ridge, and the Emperor Seamounts. This species is a common bycatch in the longline fishery for the skilfish <em>Erilepis zonifer</em> (Anoplopomatidae) and some rockfishes (Sebastidae). However, there is no published information on its distribution and biology. Based on observations on commercial longlines between 2014 and 2018, the catch distribution, size and sex, size of otoliths, age and growth, sex ratio and sexual maturity of <em>C. gilberti</em> in the waters of the Emperor Seamounts (NW Pacific) are presented. This species has been caught from Nintoku Seamount in the north to Kammu Seamount in the south and is most commonly found off the Jingu, Ojin, and Kammu seamounts. The species has been recorded from 215 to 1840 m, which significantly extends its known bathymetric range. The catches included individuals from 34 to 93 cm (mean 53.2 cm), weight 140–5240 g (mean 688.2 g) and age from 24 to 48 years (mean 37.9 years). The females were significantly longer, heavier and older than the males and generally dominated the catches (the proportion of males &lt;40%). The growth of <em>C. gilberti</em> is best described by a von Bertalanffy growth function (VBGF), and the parameters of the von Bertalanffy growth equation were L∞ = 61.6, k = 0.09, t₀ = −1.4. Spawning individuals were recorded in catches only in April, which is the end of spawning. Further research with year-round trawl samples is needed to obtain more detailed information on the life cycle of <em>C. gilberti</em>.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105461"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386454","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":"Phytoplankton communities distribution along a physical gradient in the eastern Indian Ocean based on their pigments and absorption properties","authors":"Chandanlal Parida,&nbsp;David Antoine","doi":"10.1016/j.dsr2.2025.105460","DOIUrl":"10.1016/j.dsr2.2025.105460","url":null,"abstract":"<div><div>Phytoplankton pigments and absorption properties were measured along 110° E in the southeast Indian Ocean during a research voyage carried out on R/V Investigator in May–June 2019. The data set was collected along a 3300 km transect starting from mesotrophic conditions around 40° S (chlorophyll concentration of about 0.5 mg m⁻³) to oligotrophic conditions (0.04 mg m⁻³) near 10° S. A cluster analysis was applied to phytoplankton absorption data, in which the absorption-based clusters serve as a reference for identifying different phytoplankton pigment assemblages and their depth in the water column. The resulting clusters reflect variations in phytoplankton pigment compositions and degrees of pigment packaging, categorised into distinct groups: mesotrophic waters, surface oligotrophic waters, deeper waters near the deep chlorophyll maxima and low-chlorophyll waters at depths exceeding 100 m. Our results confirm that pigment composition has a significant impact on the absorption spectra for given chlorophyll concentrations. In oligotrophic conditions, the proportions of photosynthetic and photoprotective pigments show large variations along depth. We also found that the phytoplankton absorption coefficient in the blue is lower than predicted by relationships previously established with Chl-<em>a</em>. When pico- and micro-phytoplankton are generally expected to vary in opposite ways from oligo-to meso-trophic waters, with the contribution of nano-phytoplankton remaining quite stable, we here found that pico- and nano-phytoplankton were the varying fractions along the transect, with the contribution of micro-phytoplankton remaining stable and low (about 10%). Our results support the use of optical properties, which are linked to pigment composition, cell size, and intracellular pigment concentration to study phytoplankton communities across varied oceanographic regimes.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105460"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Diet of deep-sea octocorals from the Emperor Seamount Chain inferred by fatty acid trophic markers","authors":"S.A. Rodkina,&nbsp;T.N. Dautova","doi":"10.1016/j.dsr2.2025.105462","DOIUrl":"10.1016/j.dsr2.2025.105462","url":null,"abstract":"<div><div>Despite the important role that octocorals (Cnidaria: Octocorallia) play in creating and maintaining deep-sea communities known as coral gardens, little is known about their diet. We analyzed the fatty acid compositions of deep-sea octocorals collected from Koko Guyot, located in the southern Emperor Seamount Chain, to identify their main food sources. The data suggests that octocorals feed mainly on zooplankton. However, the contribution of zooplankton to their diet varies greatly among different species and is determined by different zooplankton groups (herbivores, carnivores, or omnivores). This is evidenced by the increased content of some monounsaturated fatty acids (FA) and the different ratios of polyunsaturated fatty acids in corals. In bamboo coral <em>Isidella</em>, we observed the maximum enrichment in calanoid copepod markers (20:1n-9 and 22:1n-1). In addition to the copepod markers, most corals showed a high level of the carnivore marker (18:1n-9), which indicates a significant contribution of other (non-calanoid copepods) items to the diet. The high level of n-3 polyunsaturated fatty acids (PUFA) such as the diatom marker 20:5n-3 suggests that corals of the family Primnoidae take up more freshly produced material. However, the high level of n-6 PUFA (especially, 20:4n-6), found in Paramuriceidae and <em>Keroeides</em> corals may indicate the involvement of detrital links in their diet. FA analysis is useful for identifying the diet of cold-water octocorals and provides a basis for prediction of future potential changes of the bottom ecosystems in the Emperor Seamount Chain.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105462"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395369","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":"Late Holocene and recent cold-water coral calcium carbonate production in Guilvinec Canyon, Bay of Biscay, France","authors":"Evan Edinger ,&nbsp;Jean-François Bourillet ,&nbsp;Lenaïck Menot ,&nbsp;Franck Lartaud ,&nbsp;Mathilde Chemel ,&nbsp;Stephan Jorry","doi":"10.1016/j.dsr2.2024.105451","DOIUrl":"10.1016/j.dsr2.2024.105451","url":null,"abstract":"<div><div>Cold-water coral reefs and communities can be locally important calcium carbonate factories in continental shelf and slope environments, including submarine canyons. Here we present short-term and long-term estimates of coral carbonate production by colonial scleractinian coral communities in the 750–850 m depth range in Guilvinec Canyon, northern Bay of Biscay. Short-term (annual-decadal) estimates were calculated using local coral skeletal biomass, estimated as a product of coral size and abundance from ROV video surveys, a locally generated species-specific regression between coral colony size and wet weight, and published daily or annual percent growth rates for <em>Lophelia pertusa</em> and <em>Madrepora oculata</em>. A long-term (century-millennial) estimate of carbonate accretion for the same reef was derived from a piston core through the same coral community.</div><div>Average live colonial scleractinian skeletal biomass in the Guilvinec Canyon coral mounds was 153.9 ± 39.4 g CaCO₃ m⁻². Applying published growth rates, the average annual gross carbonate production was 6.85 ± 1.79 g CaCO₃ m⁻² y⁻¹, range 0–30.2 g CaCO₃ m⁻² y⁻¹. This carbonate production rate was about one order of magnitude lower than previous estimates from the Norwegian shelf.</div><div>A 2011 piston core through the mound was analyzed by CT-scan and subsampled for coral abundance. An age model from previous ¹⁴C and U/Th ages of coral fragments in the core yielded a long-term average coral carbonate accretion rate of 78 g CaCO₃ m⁻² y⁻¹ over the past ∼2150 y, range 40.8 (core-bottom) to 148.5 g CaCO₃ m⁻² y⁻¹ in the upper half, about 1–2 orders of magnitude lower than previous estimates from other regions.</div><div>Low carbonate accretion rates observed in the Guilvinec Canyon mounds could be attributable to recent declines in live coral cover, indicated by low abundance of live corals in ROV surveys from this site, compared to other regions of the Northeast Atlantic.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105451"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Contrasting trends of the ocean CO2 sink and pH in the agulhas current system and the Mozambique basin, south-western Indian ocean (1963–2023)","authors":"Nicolas Metzl ,&nbsp;Claire Lo Monaco ,&nbsp;Guillaume Barut ,&nbsp;Jean-François Ternon","doi":"10.1016/j.dsr2.2025.105459","DOIUrl":"10.1016/j.dsr2.2025.105459","url":null,"abstract":"<div><div>We describe new observations of the oceanic carbonate system in the South-Western Indian Ocean obtained in January 2021 (OISO-31 cruise) and May 2022 (RESILIENCE cruise). To evaluate the decadal trends and drivers of fugacity of CO₂ (fCO₂), air-sea CO₂ fluxes, dissolved inorganic carbon (C_T) and pH, we used available data in this region over 1963–2023 and compared the results in the Mozambique Basin and in the Agulhas region near the African coast. Over 1995–2023, we found a faster fCO₂ increase in the Mozambique basin (2.03 ± 0.07 μatm.yr⁻¹) compared to the coastal zone (1.37 ± 0.07 μatm.yr⁻¹). The temporal change of anthropogenic CO₂ concentrations estimated in subsurface enables to reconstruct the carbonate system properties since the 1960s. In the Mozambique Basin the CO₂ sink increased slightly over 1960–2022 with a maximum observed in May 2022 (−2.4 mmolC.m⁻².d⁻¹). In the coastal zone, the ocean CO₂ sink increased from near equilibrium in the 1960s to a maximum observed in May 2022 (−4.2 mmolC.m⁻².d⁻¹). In both regions, we found a decrease of pH, most pronounced in the open ocean zone (−0.020 ± 0.001.decade⁻¹ over 1995–2023). The lowest pH of 8.04 was observed in January 2021, 0.11 lower than in the 1960s. The increase of the CO₂ sink and the decrease of pH were mainly driven by anthropogenic CO₂ uptake, with about 10% due to the ocean warming.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105459"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Understanding future changes of Chlorophyll-a in the Indian Ocean using CMIP6 Earth System Model simulations","authors":"Athira K. ,&nbsp;Prasanna Kanti Ghoshal ,&nbsp;A.P. Joshi ,&nbsp;Linta Rose ,&nbsp;Kunal Chakraborty","doi":"10.1016/j.dsr2.2025.105458","DOIUrl":"10.1016/j.dsr2.2025.105458","url":null,"abstract":"<div><div>This study uses the Coupled Model Intercomparison Project phase 6 (CMIP6) Earth System Model simulated outputs and satellite-based chlorophyll-a (Chl-a) observations to understand the changes in Chl-a concentration in the recent past and its future changes in the Indian Ocean. Based on the availability of common models across the three future scenarios (SSP5-8.5, SSP2-4.5, and SSP1-2.6), we chose 11 CMIP6 models for this study. The climatology of these model-simulated historical outputs is assessed against a satellite-based Ocean Colour Climate Change Initiative-Version 5 (OC-CCI-V5) data product. The Indian Ocean (IO) is divided into four regions (Arabian Sea (AS), Bay of Bengal (BoB), Central Indian Ocean (CIO), and Southern Indian Ocean (SIO)), and the performance of each of these CMIP6 models are evaluated in each of these regions of IO. Based on the statistical analysis, GFDL-ESM4 is found to be the best-performing model across all four IO regions. However, the GFDL-ESM4 underestimates Chl-a concentration in the AS and CIO regions (<span><math><mo>&gt;</mo></math></span> 0.07 mg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>), whereas it overestimates Chl-a concentration in the BoB region (<span><math><mo>&lt;</mo></math></span> −0.07 mg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>). The GFDL-ESM4 performs relatively better in the SIO region with a less biased Chl-a concentration. Under the SSP5-8.5 scenario, the future changes of Chl-a indicate a large decrease in the Chl-a concentrations (<span><math><mo>&lt;</mo></math></span> −0.04 mg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>) in the western coast of the AS, the western coast of BoB, and the southern Java coast. This large decrease in Chl-a concentration is limited to nearly 0.01 mg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> under the SSP1-2.6 scenario. Therefore, the implementation of extreme mitigation measures can control the reduction of surface Chl-a concentration in the IO. The analysis to understand future changes in Chl-a concentration in the mixed layer of six upwelling zones in the IO indicates a decrease in Chl-a concentration in the mixed layer by −0.06 to −0.09 mg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> in all future scenarios.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105458"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104382","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":"Uncovering the hidden amphipod biodiversity and its drivers in the Persian Gulf","authors":"Farzaneh Momtazi ,&nbsp;Abdolvahab Maghsoudlou ,&nbsp;Hanieh Saeedi","doi":"10.1016/j.dsr2.2025.105463","DOIUrl":"10.1016/j.dsr2.2025.105463","url":null,"abstract":"<div><div>The Persian Gulf (PG), an epicontinental sea at the northwestern corner of the Indian Ocean presents a challenging environment in which species confront the upper limits of their environmental tolerance. Previous hypotheses suggested that the PG is a homogeneous ecosystem characterized by low species diversity and a limited number of endemic species. We investigated these hypotheses by studying the amphipods' distribution pattern and environmental drivers, a dominant benthic group in the PG. We compiled an extensive database of amphipod distribution by integrating the open-access data including the Ocean Biodiversity Information System (OBIS) and Global Biodiversity Information Facility (GBIF), literature mining on amphipods, as well as the author's sampling database from the Persian Gulf and the Gulf of Oman. Following careful data cleaning and quality control, the final dataset comprised 1411 distribution records of 134 accepted marine amphipod species collected from depths ranging from 0 to 100 m. The environmental variables were extracted from the Bio-ORACLE database for the benthic layer with the maximum depth. Species richness per hexagonal cells (alpha species richness), and ES15 (expected number of species per 15 random samples) were calculated. Our findings revealed higher-than-expected species richness and non-homogeneous amphipod distribution across the region. Two biodiversity hotspots were identified in the northern and northwestern parts of the PG and a lowspot of amphipod species diversity in the southern half. Beta diversity cluster analysis exhibited three distinct compositions of amphipod assemblages: a northwestern community near the Arvand (Shat AL-Arab) river, a northern assemblage along Iranian coasts and the Strait of Hormuz region, and a southern assemblage along Arabian coasts. Generalized Additive Models (GAMs) and General Linear Models (GLMs) outputs showed that all environmental variables, pH, and temperature were the most important drivers in delimiting the benthic species distributions and richness. Our findings emphasize the need for a detailed approach to understanding the distribution and diversity of marine organisms in the PG where data and knowledge are less shared openly. This region should not be treated as a homogeneous ecosystem, as it harbors many endemic and rare species threatened by anthropogenic activities such as oil extraction and ocean warming.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"220 ","pages":"Article 105463"},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421546","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}