Pub Date : 2025-10-10DOI: 10.1016/j.marmicro.2025.102520
Bradley Paine , Linda Armbrecht , Christopher Bolch , Gustaaf M. Hallegraeff
Over the past fifty years, Eastern Tasmanian waters have experienced rapid warming, primarily due to the extension of the East Australian Current. This has driven expansion of warm-water biota and decline of those adapted to cooler conditions, including phytoplankton. Presently, plankton monitoring, including diatoms along Eastern Tasmania, spans <100 years. This study reconstructed diatom communities throughout a sediment core spanning 9000 years before present (9 kyrs BP), using microfossil analysis and molecular techniques, including sedimentary ancient DNA (sedaDNA) and 18S rRNA from a 10-year water column archive at the Maria Island IMOS National Reference Station mooring.
Microfossil analysis revealed a dominance of strongly silicified benthic taxa (Campylodiscus, Diploneis, Paralia, Pyxidicula, Triceratium). Notably, Paralia sulcata showed a shift ∼6 kyrs BP from small to larger cells, possibly reflecting a transition from a coastal to shelf ecosystem. However, microfossils underrepresented lightly silicified planktonic diatoms. Molecular methods detected higher diatom diversity, though up to 50 % of sedaDNA reads remained unclassified due to reference library limitations. Lightly silicified planktonic genera (Chaetoceros, Corethron, Lithodesmium, Rhizosolenia) were identified only via molecular approaches and comprised 73 % of sedaDNA and 88 % of 18S rRNA records. Of 10 shared diatom families, 5, 15, and 4 were unique to microscopy, sedaDNA, and 18S rRNA, respectively. SedaDNA also captured greater benthic diversity.
Our findings revealed limitations in reconstructing historic diatom assemblages from sediment cores. Microfossils faced constraints due to difficulties in morphological identification and preservation biases. In contrast, sedaDNA analysis yielded finer taxonomic resolution, provided access to high-quality reference sequence libraries were available.
{"title":"A 9000-year marine diatom assemblage reconstruction off Eastern Tasmania, Australia, using microfossil and molecular methods","authors":"Bradley Paine , Linda Armbrecht , Christopher Bolch , Gustaaf M. Hallegraeff","doi":"10.1016/j.marmicro.2025.102520","DOIUrl":"10.1016/j.marmicro.2025.102520","url":null,"abstract":"<div><div>Over the past fifty years, Eastern Tasmanian waters have experienced rapid warming, primarily due to the extension of the East Australian Current. This has driven expansion of warm-water biota and decline of those adapted to cooler conditions, including phytoplankton. Presently, plankton monitoring, including diatoms along Eastern Tasmania, spans <100 years. This study reconstructed diatom communities throughout a sediment core spanning 9000 years before present (9 kyrs BP), using microfossil analysis and molecular techniques, including sedimentary ancient DNA (<em>sed</em>aDNA) and 18S rRNA from a 10-year water column archive at the Maria Island IMOS National Reference Station mooring.</div><div>Microfossil analysis revealed a dominance of strongly silicified benthic taxa (<em>Campylodiscus</em>, <em>Diploneis</em>, <em>Paralia</em>, <em>Pyxidicula</em>, <em>Triceratium</em>). Notably, <em>Paralia sulcata</em> showed a shift ∼6 kyrs BP from small to larger cells, possibly reflecting a transition from a coastal to shelf ecosystem. However, microfossils underrepresented lightly silicified planktonic diatoms. Molecular methods detected higher diatom diversity, though up to 50 % of sedaDNA reads remained unclassified due to reference library limitations. Lightly silicified planktonic genera (<em>Chaetoceros</em>, <em>Corethron</em>, <em>Lithodesmium</em>, <em>Rhizosolenia</em>) were identified only via molecular approaches and comprised 73 % of sedaDNA and 88 % of 18S rRNA records. Of 10 shared diatom families, 5, 15, and 4 were unique to microscopy, sedaDNA, and 18S rRNA, respectively. <em>Seda</em>DNA also captured greater benthic diversity.</div><div>Our findings revealed limitations in reconstructing historic diatom assemblages from sediment cores. Microfossils faced constraints due to difficulties in morphological identification and preservation biases. In contrast, <em>sed</em>aDNA analysis yielded finer taxonomic resolution, provided access to high-quality reference sequence libraries were available.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102520"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-08DOI: 10.1016/j.marmicro.2025.102522
Shokoufeh Mori , Sakineh Arefifard , Thomas J. Algeo , Jonathan D. Schueth
Upper Cretaceous and Paleogene deposits are broadly distributed within the Zagros Basin of western and southwestern Iran, yet a nearly continuous stratigraphic record of the calcareous nannofossil stratigraphy of this region has not been generated to date. Rich and diverse assemblages of calcareous nannofossil are present in the uppermost Cenomanian to Ypresian deposits of the Arkavaz section on the southwestern limb of the Kabir Kuh Anticline. The presence of the taxon Marthasterites furcatus demonstrates a late Turonian age for the base of the section. Two hiatuses were identified: one at the Santonian/Campanian boundary, where the UC13 Biozone is missing, and the other in the lower Campanian, where the UC15a-b Biozone is missing. The bulk of the section is of Campanian age, indicating a high sedimentation rate during that stage. The Cretaceous/Paleogene boundary is marked by abundant calcareous dinoflagellates as well as increased abundances of calcispheres (“Thoracosphaera” sp.) and Neobiscutum. A complete record of key index taxa of Paleocene to lower Eocene biozones NP1–12 is present. We note elevated abundance of Biscutum constans, Discorhabdus ignotus, and Zeugrhabdotus noeliae coeval with the Cenomanian/Turonian boundary (CTB) respectively, similar to records in other Tethyan sections. The PETM interval contains abundant oligotrophic taxa such as Sphenolithus and Zygrhablithus but lacks many of the nannofossil taxa noted elsewhere, whereas other PETM sections in the Tethyan region are characterized by a notable decrease in oligotrophic taxa. The Arkavaz section is a leading target for further study of paleoenvironmental changes and biotic events through the Late Cretaceous to Paleogene.
{"title":"Calcareous nannofossil biostratigraphy of the upper cretaceous to lower Paleocene succession in the Zagros Basin, western Iran: Implications for the OAE2 and PETM events","authors":"Shokoufeh Mori , Sakineh Arefifard , Thomas J. Algeo , Jonathan D. Schueth","doi":"10.1016/j.marmicro.2025.102522","DOIUrl":"10.1016/j.marmicro.2025.102522","url":null,"abstract":"<div><div>Upper Cretaceous and Paleogene deposits are broadly distributed within the Zagros Basin of western and southwestern Iran, yet a nearly continuous stratigraphic record of the calcareous nannofossil stratigraphy of this region has not been generated to date. Rich and diverse assemblages of calcareous nannofossil are present in the uppermost Cenomanian to Ypresian deposits of the Arkavaz section on the southwestern limb of the Kabir Kuh Anticline. The presence of the taxon <em>Marthasterites furcatus</em> demonstrates a late Turonian age for the base of the section. Two hiatuses were identified: one at the Santonian/Campanian boundary, where the UC13 Biozone is missing, and the other in the lower Campanian, where the UC15a-b Biozone is missing. The bulk of the section is of Campanian age, indicating a high sedimentation rate during that stage. The Cretaceous/Paleogene boundary is marked by abundant calcareous dinoflagellates as well as increased abundances of calcispheres (<em>“Thoracosphaera</em>” sp.) and <em>Neobiscutum</em>. A complete record of key index taxa of Paleocene to lower Eocene biozones NP1–12 is present. We note elevated abundance of <em>Biscutum constans</em>, <em>Discorhabdus ignotus</em>, and <em>Zeugrhabdotus noeliae</em> coeval with the Cenomanian/Turonian boundary (CTB) respectively, similar to records in other Tethyan sections. The PETM interval contains abundant oligotrophic taxa such as <em>Sphenolithus</em> and <em>Zygrhablithus</em> but lacks many of the nannofossil taxa noted elsewhere, whereas other PETM sections in the Tethyan region are characterized by a notable decrease in oligotrophic taxa. The Arkavaz section is a leading target for further study of paleoenvironmental changes and biotic events through the Late Cretaceous to Paleogene.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102522"},"PeriodicalIF":1.6,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-03DOI: 10.1016/j.marmicro.2025.102521
Nguyen Van Su, Nguyen Tan Trieu, Mai Hoang Dam, Nguyen Thi Tham, Bui Thi Ngoc Phuong
This study integrates biostratigraphic and petrographic data from five wells to characterize Miocene sediments in the southeastern Nam Con Son Basin, offshore Vietnam. The Miocene succession is divided into three distinct units. The Lower Miocene (foraminiferal zones M1b–M5, nannofossil zones CNM2–CNM6) consists of sandstone, siltstone, and calcareous claystone deposited in intertidal to middle neritic environments, characterized by low microfossil abundance. The overlying Middle Miocene (M5–M9, CNM7–CNM9) comprises sandstone interbedded with packstone and wackestone and records a significant increase in microfossil abundance and diversity, indicating a transgression into middle to outer neritic settings. A major stratigraphic hiatus, marked by the absence of zones M10–M13a and CNM10–CNM14, separates the Middle from the Upper Miocene. The latter unit (M13b–M14, CNM15–CNM20) is composed of limestone, calcareous claystone, and siliciclastic sediments and exhibits a peak in microfossil abundance and diversity, reflecting continued deepening to outer neritic and upper bathyal conditions. Reservoir quality varies significantly across the succession. While the Lower and Middle Miocene sandstones and Upper Miocene limestones exhibit moderate to good porosity enhanced by grain dissolution, the Lower and Middle Miocene limestones show poor porosity due to cementation. This refined stratigraphic framework significantly improves regional correlation and enhances geological models for future hydrocarbon exploration in the basin.
{"title":"Biostratigraphy and petrography of Miocene sediments in the southeastern Nam Con Son Basin, Vietnam","authors":"Nguyen Van Su, Nguyen Tan Trieu, Mai Hoang Dam, Nguyen Thi Tham, Bui Thi Ngoc Phuong","doi":"10.1016/j.marmicro.2025.102521","DOIUrl":"10.1016/j.marmicro.2025.102521","url":null,"abstract":"<div><div>This study integrates biostratigraphic and petrographic data from five wells to characterize Miocene sediments in the southeastern Nam Con Son Basin, offshore Vietnam. The Miocene succession is divided into three distinct units. The Lower Miocene (foraminiferal zones M1b–M5, nannofossil zones CNM2–CNM6) consists of sandstone, siltstone, and calcareous claystone deposited in intertidal to middle neritic environments, characterized by low microfossil abundance. The overlying Middle Miocene (M5–M9, CNM7–CNM9) comprises sandstone interbedded with packstone and wackestone and records a significant increase in microfossil abundance and diversity, indicating a transgression into middle to outer neritic settings. A major stratigraphic hiatus, marked by the absence of zones M10–M13a and CNM10–CNM14, separates the Middle from the Upper Miocene. The latter unit (M13b–M14, CNM15–CNM20) is composed of limestone, calcareous claystone, and siliciclastic sediments and exhibits a peak in microfossil abundance and diversity, reflecting continued deepening to outer neritic and upper bathyal conditions. Reservoir quality varies significantly across the succession. While the Lower and Middle Miocene sandstones and Upper Miocene limestones exhibit moderate to good porosity enhanced by grain dissolution, the Lower and Middle Miocene limestones show poor porosity due to cementation. This refined stratigraphic framework significantly improves regional correlation and enhances geological models for future hydrocarbon exploration in the basin.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102521"},"PeriodicalIF":1.6,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-26DOI: 10.1016/j.marmicro.2025.102519
Saki Ishino , Takuya Itaki , Motohisa Fukuda
Recent evidence suggests that object detection techniques based on deep learning are evidently useful for automating microfossil analysis, particularly by enabling the rapid and accurate extraction of target particles. While the assemblage and morphometric analysis of fossil diatoms requires unique procedures, such as including fragmented specimens in counts and accounting for intra-morphometric variation, little is known regarding how these factors affect detection accuracy or how to efficiently construct training datasets for data-driven methods such as deep learning. In this study, we experimentally evaluated the use of the YOLOv5 object detection model to detect Eucampia antarctica, a key paleoenvironmental indicator, across sites in the Southern Ocean that vary in sedimentological and biogeographical characteristics. Detection accuracy was assessed using the datasets from fourteen test sites for the models trained on datasets from four individual sites, that vary within E. antarctica morphology and fossil preservation state, as well as models trained on pairwise combinations of these sites. Our results show that morphological variation of E. antarctica did not significantly affect detection performance, but models trained on datasets of moderately preserved fossils slightly outperformed those trained on datasets of well-preserved fossils. Furthermore, the findings suggest that incorporating diverse non-target particles including other diatom fragments and sediment particles in training data is critical for developing robust models that maintain consistently high performance in diverse regions. Our experiments demonstrate that object detection models allow rapid and accurate counting of E. antarctica, thereby improving its use in paleoenvironmental reconstructions, including past sea ice and surface temperatures.
{"title":"Deep learning object detection for fossil diatom counting: assessing the impact of fossil preservation and intraspecific morphological variation","authors":"Saki Ishino , Takuya Itaki , Motohisa Fukuda","doi":"10.1016/j.marmicro.2025.102519","DOIUrl":"10.1016/j.marmicro.2025.102519","url":null,"abstract":"<div><div>Recent evidence suggests that object detection techniques based on deep learning are evidently useful for automating microfossil analysis, particularly by enabling the rapid and accurate extraction of target particles. While the assemblage and morphometric analysis of fossil diatoms requires unique procedures, such as including fragmented specimens in counts and accounting for intra-morphometric variation, little is known regarding how these factors affect detection accuracy or how to efficiently construct training datasets for data-driven methods such as deep learning. In this study, we experimentally evaluated the use of the YOLOv5 object detection model to detect <em>Eucampia antarctica</em>, a key paleoenvironmental indicator, across sites in the Southern Ocean that vary in sedimentological and biogeographical characteristics. Detection accuracy was assessed using the datasets from fourteen test sites for the models trained on datasets from four individual sites, that vary within <em>E. antarctica</em> morphology and fossil preservation state, as well as models trained on pairwise combinations of these sites. Our results show that morphological variation of <em>E. antarctica</em> did not significantly affect detection performance, but models trained on datasets of moderately preserved fossils slightly outperformed those trained on datasets of well-preserved fossils. Furthermore, the findings suggest that incorporating diverse non-target particles including other diatom fragments and sediment particles in training data is critical for developing robust models that maintain consistently high performance in diverse regions. Our experiments demonstrate that object detection models allow rapid and accurate counting of <em>E. antarctica</em>, thereby improving its use in paleoenvironmental reconstructions, including past sea ice and surface temperatures.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102519"},"PeriodicalIF":1.6,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-25DOI: 10.1016/j.marmicro.2025.102518
Rose Manceau , Meryem Mojtahid , Eelco Rohling , Robin Fentimen , Thibault de Garidel-Thoron , Sonia Chaabane , Gianluca Marino
Planktonic foraminifera provide essential palaeoceanographic proxies, as their shells are used to characterise past ocean conditions. The accurate interpretation of palaeorecords depends on a thorough understanding of the species-specific ecological preferences. While global distribution patterns are well documented, regional analysis are sparser, which limits our understanding of the response of planktonic foraminiferal distribution to local environmental conditions. This study synthesises data of extant planktonic foraminiferal abundances to determine their spatial and vertical distributions in the Bay of Bengal, using available and published plankton net and sediment trap data. Our analysis highlights the dominance of six species that exhibit distinctive spatial and vertical distribution patterns. Globigerinoides ruber and Trilobatus sacculifer are associated with oligotrophic waters, and nutrient-rich areas, respectively. They consistently inhabit the upper 40 m of the water column, within the mixed layer. Neogloboquadrina dutertrei and Globigerina bulloides thrive in stratified waters near the Ganges-Brahmaputra River mouth and in the upwelling system south of India. While abundant in the mixed layer, their high numbers in the subsurface in stratified conditions and associated subsurface nutrient availability highlights their capacity to dwell in both surface and subsurface environments. Globorotalia cultrata and Globigerinita glutinata are abundant in the northern Bay of Bengal, with G. cultrata inhabiting the upper thermocline, while G. glutinata has the broadest vertical distribution, from the mixed layer to the deep thermocline. These findings help constraining the regional response of key species to local conditions and hence their use in palaeoenvironmental reconstructions from this critical sector of the global ocean.
{"title":"Insights into the spatial and vertical distribution of extant planktonic foraminifera in the Bay of Bengal","authors":"Rose Manceau , Meryem Mojtahid , Eelco Rohling , Robin Fentimen , Thibault de Garidel-Thoron , Sonia Chaabane , Gianluca Marino","doi":"10.1016/j.marmicro.2025.102518","DOIUrl":"10.1016/j.marmicro.2025.102518","url":null,"abstract":"<div><div>Planktonic foraminifera provide essential palaeoceanographic proxies, as their shells are used to characterise past ocean conditions. The accurate interpretation of palaeorecords depends on a thorough understanding of the species-specific ecological preferences. While global distribution patterns are well documented, regional analysis are sparser, which limits our understanding of the response of planktonic foraminiferal distribution to local environmental conditions. This study synthesises data of extant planktonic foraminiferal abundances to determine their spatial and vertical distributions in the Bay of Bengal, using available and published plankton net and sediment trap data. Our analysis highlights the dominance of six species that exhibit distinctive spatial and vertical distribution patterns. G<em>lobigerinoides ruber</em> and <em>Trilobatus sacculifer</em> are associated with oligotrophic waters, and nutrient-rich areas, respectively. They consistently inhabit the upper 40 m of the water column, within the mixed layer. <em>Neogloboquadrina dutertrei</em> and <em>Globigerina bulloides</em> thrive in stratified waters near the Ganges-Brahmaputra River mouth and in the upwelling system south of India. While abundant in the mixed layer, their high numbers in the subsurface in stratified conditions and associated subsurface nutrient availability highlights their capacity to dwell in both surface and subsurface environments. <em>Globorotalia cultrata</em> and <em>Globigerinita glutinata</em> are abundant in the northern Bay of Bengal, with <em>G. cultrata</em> inhabiting the upper thermocline, while <em>G. glutinata</em> has the broadest vertical distribution, from the mixed layer to the deep thermocline. These findings help constraining the regional response of key species to local conditions and hence their use in palaeoenvironmental reconstructions from this critical sector of the global ocean.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102518"},"PeriodicalIF":1.6,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-19DOI: 10.1016/j.marmicro.2025.102517
Yoshiyuki Ishitani , Kozo Takahashi
Vertical distributions of siliceous plankton groups in the seas off Japan were studied to clarify their ecological preferences. Radiolarian standing stock maxima were absent in the layers where silicoflagellate and diatom standing stock maxima occured. The vertical distribution patterns of silicoflagellate species were consistent vertically, whereas their geographic distributions differed, likely reflecting current systems. Two silicoflagellate taxa (Octactis speculum and O. octanaria var. pulchra) showed strong correlations with temperature. In contrast, diatoms displayed two distinct vertical distribution types: Group 1 (above pycnocline) and Group 2 (below pycnocline). Based on their vertical and geographic distributions, large diatoms such as Stephanopyxis palmeriana, Coscinodiscus asteromphalus, C. wailesii group, C. oculus-iridis, C. perforatus, and Stellarima stellaris are identified as a”shade flora“. Members of the family Rhizosoleniaceae exhibit an effective strategy for adapting to oligotrophic conditions. Several taxa can serve as environmental proxies: Thalassiosira eccentrica as nitrate concentration in the surface, Bacteriastrum delicatulum as low temperature and high phosphate, and Phaeoceros spp. and Hyalochaete spp. as nitrite and ammonium stocks. Comparison among siliceous plankton suggests that increasing stratification leads to vertical partitioning among siliceous plankton. Under weak stratification, silicoflagellates and diatoms dominate surface waters, whereas stronger stratification causes silicoflagellates and large centric diatoms to accumulate near the pycnocline, followed by other diatoms. Living radiolarian standing stocks are regulated by siliceous phytoplankton and peak below their abundant layers. This study demonstrates clear vertical partitioning among siliceous plankton groups.
{"title":"Vertical partitioning of siliceous plankton in the stratified waters around Japan","authors":"Yoshiyuki Ishitani , Kozo Takahashi","doi":"10.1016/j.marmicro.2025.102517","DOIUrl":"10.1016/j.marmicro.2025.102517","url":null,"abstract":"<div><div>Vertical distributions of siliceous plankton groups in the seas off Japan were studied to clarify their ecological preferences. Radiolarian standing stock maxima were absent in the layers where silicoflagellate and diatom standing stock maxima occured. The vertical distribution patterns of silicoflagellate species were consistent vertically, whereas their geographic distributions differed, likely reflecting current systems. Two silicoflagellate taxa (<em>Octactis speculum</em> and <em>O. octanaria</em> var. <em>pulchra</em>) showed strong correlations with temperature. In contrast, diatoms displayed two distinct vertical distribution types: Group 1 (above pycnocline) and Group 2 (below pycnocline). Based on their vertical and geographic distributions, large diatoms such as <em>Stephanopyxis palmeriana</em>, <em>Coscinodiscus asteromphalus</em>, <em>C. wailesii</em> group, <em>C. oculus-iridis</em>, <em>C. perforatus</em>, and <em>Stellarima stellaris</em> are identified as a”shade flora“. Members of the family Rhizosoleniaceae exhibit an effective strategy for adapting to oligotrophic conditions. Several taxa can serve as environmental proxies: <em>Thalassiosira eccentrica</em> as nitrate concentration in the surface, <em>Bacteriastrum delicatulum</em> as low temperature and high phosphate, and <em>Phaeoceros</em> spp. and <em>Hyalochaete</em> spp. as nitrite and ammonium stocks. Comparison among siliceous plankton suggests that increasing stratification leads to vertical partitioning among siliceous plankton. Under weak stratification, silicoflagellates and diatoms dominate surface waters, whereas stronger stratification causes silicoflagellates and large centric diatoms to accumulate near the pycnocline, followed by other diatoms. Living radiolarian standing stocks are regulated by siliceous phytoplankton and peak below their abundant layers. This study demonstrates clear vertical partitioning among siliceous plankton groups.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102517"},"PeriodicalIF":1.6,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-16DOI: 10.1016/j.marmicro.2025.102516
Lai Shan Sum
Our understanding of Quaternary planktonic foraminiferal ecostratigraphy in the Demerara Rise region is limited. Analysing planktonic foraminiferal assemblage turnovers can help in understanding the palaeoecological changes experienced in this area. A comparison of the planktonic foraminiferal assemblage turnover index (ATI) between tropical cores (ODP Hole 1261A, Demerara Rise; and three En20 piston cores, Leeward Islands) and a subtropical core (ODP Hole 994C, Blake Ridge Plateau) reveals lower mean ATIs values in the tropics than that in the subtropics. Peaks in ATIs at ODP Hole 1261A did not coincide with the onset of interglacial periods as they did at ODP Hole 994C, limiting its use for broad correlations. Significant difference in medians of ATIs values between these cores is attributed to differential heating across latitudes, warm-water species contributing most to the tropical turnovers and dominating the interpretable principal component loadings.
Significant correlation in Globigerina bulloides and Globigerinita glutinata indicate that upwelling contributed to some peak assemblage turnovers. Conversely, there being no significant correlation between Globigerinoides ruberpink and Neogloboquadrina dutertrei, suggests that the nearby Amazon River did not greatly affect assemblage turnover at the Demerara Rise as much as the equatorial location of the cores and upwelling. Additionally, sequential changes in proportional abundances of the planktonic foraminiferal species indicated variations in upwelling, thermocline depth and sea-levels during glacial terminations. This study demonstrates that the use of ATI highlights multiple factors affecting individual planktonic foraminiferal species and overall assemblages. However, understanding of regional factors is crucial for effectively using ATI as an ecostratigraphic tool.
{"title":"Equatorial sea surface temperature and upwelling: A comparative analysis of late quaternary planktonic foraminiferal ecostratigraphy","authors":"Lai Shan Sum","doi":"10.1016/j.marmicro.2025.102516","DOIUrl":"10.1016/j.marmicro.2025.102516","url":null,"abstract":"<div><div>Our understanding of Quaternary planktonic foraminiferal ecostratigraphy in the Demerara Rise region is limited. Analysing planktonic foraminiferal assemblage turnovers can help in understanding the palaeoecological changes experienced in this area. A comparison of the planktonic foraminiferal assemblage turnover index (ATI) between tropical cores (ODP Hole 1261A, Demerara Rise; and three En20 piston cores, Leeward Islands) and a subtropical core (ODP Hole 994C, Blake Ridge Plateau) reveals lower mean ATI<sub>s</sub> values in the tropics than that in the subtropics. Peaks in ATI<sub>s</sub> at ODP Hole 1261A did not coincide with the onset of interglacial periods as they did at ODP Hole 994C, limiting its use for broad correlations. Significant difference in medians of ATI<sub>s</sub> values between these cores is attributed to differential heating across latitudes, warm-water species contributing most to the tropical turnovers and dominating the interpretable principal component loadings.</div><div>Significant correlation in <em>Globigerina bulloides</em> and <em>Globigerinita glutinata</em> indicate that upwelling contributed to some peak assemblage turnovers. Conversely, there being no significant correlation between <em>Globigerinoides ruber</em><sub>pink</sub> and <em>Neogloboquadrina dutertrei</em>, suggests that the nearby Amazon River did not greatly affect assemblage turnover at the Demerara Rise as much as the equatorial location of the cores and upwelling. Additionally, sequential changes in proportional abundances of the planktonic foraminiferal species indicated variations in upwelling, thermocline depth and sea-levels during glacial terminations. This study demonstrates that the use of ATI highlights multiple factors affecting individual planktonic foraminiferal species and overall assemblages. However, understanding of regional factors is crucial for effectively using ATI as an ecostratigraphic tool.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102516"},"PeriodicalIF":1.6,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145118762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-29DOI: 10.1016/j.marmicro.2025.102506
Ana Cláudia Aoki Santarosa , Cintia Yamashita , Thaisa Marques Vicente , Maria Virginia Alves Martins , Daniel Leite Moreira , Silvia Helena de Mello e Sousa
Living (stained) benthic foraminifera from deep-sea stations in the Southern Brazilian Margin were studied to compare distribution patterns across the 63–125 μm and > 125 μm size fractions 0–1 and 1–2 cm intervals. Statistical testsconfirmed the presence of significant differences between the two sediment layers and size fractions. The superficial level showed higher density of specimens and species richness. In addition, the sediment layers show distinct species composition. The most abundant and frequent species in the 0–1 cm were Globocassidulina subglobosa, Epistominella exigua, Alabaminella weddellensis, Reophax sp. 1, Seabrookia curta, Bolivina albatrossi, Reophax tortilis, and Trifarina bradyi. Among the 96 exclusive species from the 1–2 cm, we found: Arenoparrella mexicana, Haplophragmoides fragile, Triloculinella pseudooblonga, Technitella harrisii, and Bolivina pacifica. Regarding the different size fractions, the >125 μm fraction showed lower density of specimens but higher diversity and the benthic foraminiferal assemblages had an average of 65 % agglutinated and 33 % calcareous species. The most abundant species were Reophax sp. 1, Thurammina sp. 1, Lagenammina sp. 1, Uvigerina peregrina, and Reophax scorpiurus. In the 63–125 μm size fraction, benthic foraminiferal assemblages comprised 53 % agglutinated and 43 % calcareous species, showing that the proportions of agglutinated species decreased. The most abundant species in the finer fraction were Alabaminella weddellensis, Epistominella exigua, Globocassidulina subglobosa, Seabrookia curta, and Bolivina albatrossi. Based on the statistically different results of the diversity indices, as well as the distinctive composition of species between the two layers and size fractions, we recommend the use of the >63 μm size fraction and 0–2 cm for future studies on benthic foraminifera in oligotrophic deep-sea areas.
{"title":"Living (stained) benthic foraminifera from Southern Brazilian Margin: A comparative study in different soft sediments size fractions and strata","authors":"Ana Cláudia Aoki Santarosa , Cintia Yamashita , Thaisa Marques Vicente , Maria Virginia Alves Martins , Daniel Leite Moreira , Silvia Helena de Mello e Sousa","doi":"10.1016/j.marmicro.2025.102506","DOIUrl":"10.1016/j.marmicro.2025.102506","url":null,"abstract":"<div><div>Living (stained) benthic foraminifera from deep-sea stations in the Southern Brazilian Margin were studied to compare distribution patterns across the 63–125 μm and > 125 μm size fractions 0–1 and 1–2 cm intervals. Statistical testsconfirmed the presence of significant differences between the two sediment layers and size fractions. The superficial level showed higher density of specimens and species richness. In addition, the sediment layers show distinct species composition. The most abundant and frequent species in the 0–1 cm were <em>Globocassidulina subglobosa</em>, <em>Epistominella exigua</em>, <em>Alabaminella weddellensis</em>, <em>Reophax</em> sp. 1, <em>Seabrookia curta</em>, <em>Bolivina albatrossi</em>, <em>Reophax tortilis</em>, and <em>Trifarina bradyi.</em> Among the 96 exclusive species from the 1–2 cm, we found: <em>Arenoparrella mexicana</em>, <em>Haplophragmoides fragile</em>, <em>Triloculinella pseudooblonga</em>, <em>Technitella harrisii</em>, and <em>Bolivina pacifica.</em> Regarding the different size fractions, the >125 μm fraction showed lower density of specimens but higher diversity and the benthic foraminiferal assemblages had an average of 65 % agglutinated and 33 % calcareous species. The most abundant species were <em>Reophax</em> sp. 1, <em>Thurammina</em> sp. 1, <em>Lagenammina</em> sp. 1, <em>Uvigerina peregrina</em>, and <em>Reophax scorpiurus</em>. In the 63–125 μm size fraction, benthic foraminiferal assemblages comprised 53 % agglutinated and 43 % calcareous species, showing that the proportions of agglutinated species decreased. The most abundant species in the finer fraction were <em>Alabaminella weddellensis</em>, <em>Epistominella exigua</em>, <em>Globocassidulina subglobosa</em>, <em>Seabrookia curta</em>, and <em>Bolivina albatrossi.</em> Based on the statistically different results of the diversity indices, as well as the distinctive composition of species between the two layers and size fractions, we recommend the use of the >63 μm size fraction and 0–2 cm for future studies on benthic foraminifera in oligotrophic deep-sea areas.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102506"},"PeriodicalIF":1.6,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-25DOI: 10.1016/j.marmicro.2025.102504
Ruby Barrett , Ann Power , John Love , Daniela. N. Schmidt
Coccolithophores are single-celled phytoplankton that produce calcite plates called coccoliths. Coccolithophores play a key role in long-term ocean carbon storage through the sedimentation and burial of their calcite (calcium carbonate) exoskeletons. Coccolith size is important in determining how much carbonate is ultimately buried. We present a novel method for measuring ancient coccolith size using imaging flow cytometry combined with cross-polarised light (ISX+PL). This technique provides a rapid and high throughput alternative to manual and existing automated techniques by enabling the analysis of ≈1000 objects per second without time-consuming slide preparation. We have applied ISX+PL to the fossil record for the first time, and as a proof of method, analysed samples from Goban Spur (DSDP Site 548) and Ceara Rise (ODP Site 925/9) to reconstruct 66 million years of coccolith size. We show that data obtained from ISX+PL is consistent with published coccolith size trends, including the reported decrease in size toward the modern. Changes in coccolith size below 3 μm should be treated with caution because this exceeds the accuracy of the method. The inexpensive, rapid, and less labour intensive approach increases the speed of analysis compared to existing methods. The ISX+PL method enables users to analyse more samples, increase the robustness of their dataset due to a high specimen count (≈10,000 per sample), and explore a wealth of morphological features recorded in the digital images of coccoliths. The method offers flexibility, enabling users to adapt it to their needs—for instance, by targeting specific morphologies—thereby expanding its applicability.
球石藻是单细胞浮游植物，产生方解石板，称为球石岩。球石藻通过其方解石（碳酸钙）外骨骼的沉积和埋藏，在长期的海洋碳储存中起着关键作用。球粒岩的大小对于确定最终埋藏了多少碳酸盐非常重要。我们提出了一种利用成像流式细胞术结合交叉偏振光（ISX+PL）测量古球粒大小的新方法。该技术为人工和现有的自动化技术提供了一种快速、高通量的替代方法，每秒可以分析约1000个物体，而无需耗时的玻片制备。我们首次将ISX+PL应用于化石记录，并分析了Goban Spur （DSDP Site 548）和Ceara Rise （ODP Site 925/9）的样品，重建了6600万年的球粒大小。我们发现从ISX+PL获得的数据与已发表的球粒石尺寸趋势一致，包括报告的尺寸向现代减小。球粒尺寸小于3 μm的变化应谨慎处理，因为这超出了方法的精度。与现有方法相比，这种廉价、快速、劳动密集程度较低的方法提高了分析速度。ISX+PL方法使用户能够分析更多的样品，由于高标本计数（每个样品≈10,000个），增加了数据集的鲁棒性，并探索了在球粒石的数字图像中记录的丰富形态特征。该方法提供了灵活性，使用户能够根据自己的需求进行调整——例如，针对特定的形态——从而扩大其适用性。
{"title":"A rapid method for measuring ancient coccolith size","authors":"Ruby Barrett , Ann Power , John Love , Daniela. N. Schmidt","doi":"10.1016/j.marmicro.2025.102504","DOIUrl":"10.1016/j.marmicro.2025.102504","url":null,"abstract":"<div><div>Coccolithophores are single-celled phytoplankton that produce calcite plates called coccoliths. Coccolithophores play a key role in long-term ocean carbon storage through the sedimentation and burial of their calcite (calcium carbonate) exoskeletons. Coccolith size is important in determining how much carbonate is ultimately buried. We present a novel method for measuring ancient coccolith size using imaging flow cytometry combined with cross-polarised light (ISX<sup>+PL</sup>). This technique provides a rapid and high throughput alternative to manual and existing automated techniques by enabling the analysis of ≈1000 objects per second without time-consuming slide preparation. We have applied ISX<sup>+PL</sup> to the fossil record for the first time, and as a proof of method, analysed samples from Goban Spur (DSDP Site 548) and Ceara Rise (ODP Site 925/9) to reconstruct 66 million years of coccolith size. We show that data obtained from ISX<sup>+PL</sup> is consistent with published coccolith size trends, including the reported decrease in size toward the modern. Changes in coccolith size below 3 μm should be treated with caution because this exceeds the accuracy of the method. The inexpensive, rapid, and less labour intensive approach increases the speed of analysis compared to existing methods. The ISX<sup>+PL</sup> method enables users to analyse more samples, increase the robustness of their dataset due to a high specimen count (≈10,000 per sample), and explore a wealth of morphological features recorded in the digital images of coccoliths. The method offers flexibility, enabling users to adapt it to their needs—for instance, by targeting specific morphologies—thereby expanding its applicability.</div></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102504"},"PeriodicalIF":1.6,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-21DOI: 10.1016/j.marmicro.2025.102502
Iria García-Moreiras , Ana Amorim , Vera Pospelova , Karin Zonneveld , Donald M. Anderson , Girish Beedessee , Amy Dale , Barrie Dale , Ophélie David , Anne de Vernal , Eugenia Fatourou , Emilie Folie-Boivin , Javier Helenes , María García-Portela , Fang Gu , Haifeng Gu , Vincent Iratçabal , Jan Janouškovec , Audrey Limoges , Fabienne Marret , Kenneth Neil Mertens
<div><div>Cysts are resistant life-cycle stages that play a key role in the survival and dispersal of some dinoflagellate species. Given their preservation and fossilisation potential, the organic-walled dinoflagellate cysts have been widely used as bioindicators of past and present environmental conditions. Living cysts are studied extensively due to their roles in bloom initiation, termination, and species adaptation. The use of cysts in various fields such as taxonomy, biogeography, evolution, (palaeo)ecology, and (palaeo)oceanography has expanded significantly in recent years. In this paper, we review recent developments, identify research needs, and outline future directions in marine organic-walled dinoflagellate cyst research based on round-table discussions held during the International Workshop on Dinoflagellate Cysts, which took place from 18 to 21 June 2024 in Vigo (Spain).</div><div>Key priorities in taxonomy, evolution, and biogeography include the need to continue establishing connections between the cyst and motile forms along with their associated sequences, particularly for Harmful Algal Bloom (HAB) species, and updating reference databases for metabarcoding studies. Emerging molecular techniques, such as metabarcoding, provide complementary information on cyst diversity, distribution, and geographic connectivity, thereby aiding in the monitoring and reconstruction of HAB dynamics. Given the impacts of climate change on biogeographical ranges, cysts could serve as valuable indicators for tracking HAB shifts. Combining multi-omics with morphological methods could offer deeper insights into character evolution and support the construction of the dinoflagellate tree of life. Advances in the biogeochemical analysis of dinoflagellate cyst walls, particularly through the detailed study of dinosporin, are also promising for evolutionary research, as demonstrated by recent methodological advances in Fourier Transform Infrared (FTIR) and Raman spectroscopy. In palaeoceanography and palaeoecology, improving quantitative cyst-based reconstructions requires expanding the database of living cyst assemblages and their relationships with environmental variables, especially in underrepresented regions, notably in the Southern Hemisphere. Despite progress towards standardisation, there remains no universally adopted standardised methods for extracting and concentrating cysts from sediments or for quantifying cysts—essential steps for inter-site comparisons. Additionally, sediment trap studies and field observations of associated plankton are needed to complement surface sediment research and enhance our understanding of species ecology. The emerging field of palaeogenomics is promising as it complements cyst-based research. Finally, the integration of biological and geological studies to address key scientific questions is emphasised. For example, investigating the discrepancy between the accepted geological emergence of dinoflagellates and earli
{"title":"Progress, challenges and future directions in marine organic-walled dinoflagellate cyst research: New insights from an international workshop","authors":"Iria García-Moreiras , Ana Amorim , Vera Pospelova , Karin Zonneveld , Donald M. Anderson , Girish Beedessee , Amy Dale , Barrie Dale , Ophélie David , Anne de Vernal , Eugenia Fatourou , Emilie Folie-Boivin , Javier Helenes , María García-Portela , Fang Gu , Haifeng Gu , Vincent Iratçabal , Jan Janouškovec , Audrey Limoges , Fabienne Marret , Kenneth Neil Mertens","doi":"10.1016/j.marmicro.2025.102502","DOIUrl":"10.1016/j.marmicro.2025.102502","url":null,"abstract":"<div><div>Cysts are resistant life-cycle stages that play a key role in the survival and dispersal of some dinoflagellate species. Given their preservation and fossilisation potential, the organic-walled dinoflagellate cysts have been widely used as bioindicators of past and present environmental conditions. Living cysts are studied extensively due to their roles in bloom initiation, termination, and species adaptation. The use of cysts in various fields such as taxonomy, biogeography, evolution, (palaeo)ecology, and (palaeo)oceanography has expanded significantly in recent years. In this paper, we review recent developments, identify research needs, and outline future directions in marine organic-walled dinoflagellate cyst research based on round-table discussions held during the International Workshop on Dinoflagellate Cysts, which took place from 18 to 21 June 2024 in Vigo (Spain).</div><div>Key priorities in taxonomy, evolution, and biogeography include the need to continue establishing connections between the cyst and motile forms along with their associated sequences, particularly for Harmful Algal Bloom (HAB) species, and updating reference databases for metabarcoding studies. Emerging molecular techniques, such as metabarcoding, provide complementary information on cyst diversity, distribution, and geographic connectivity, thereby aiding in the monitoring and reconstruction of HAB dynamics. Given the impacts of climate change on biogeographical ranges, cysts could serve as valuable indicators for tracking HAB shifts. Combining multi-omics with morphological methods could offer deeper insights into character evolution and support the construction of the dinoflagellate tree of life. Advances in the biogeochemical analysis of dinoflagellate cyst walls, particularly through the detailed study of dinosporin, are also promising for evolutionary research, as demonstrated by recent methodological advances in Fourier Transform Infrared (FTIR) and Raman spectroscopy. In palaeoceanography and palaeoecology, improving quantitative cyst-based reconstructions requires expanding the database of living cyst assemblages and their relationships with environmental variables, especially in underrepresented regions, notably in the Southern Hemisphere. Despite progress towards standardisation, there remains no universally adopted standardised methods for extracting and concentrating cysts from sediments or for quantifying cysts—essential steps for inter-site comparisons. Additionally, sediment trap studies and field observations of associated plankton are needed to complement surface sediment research and enhance our understanding of species ecology. The emerging field of palaeogenomics is promising as it complements cyst-based research. Finally, the integration of biological and geological studies to address key scientific questions is emphasised. For example, investigating the discrepancy between the accepted geological emergence of dinoflagellates and earli","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"201 ","pages":"Article 102502"},"PeriodicalIF":1.6,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145027133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号