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

{"title":"Spatial and temporal variations in net primary production and long-term trends between 2003 and 2022 in the Indian Ocean: A synthesis using different models","authors":"V.V.S.S. Sarma ,&nbsp;B. Sridevi ,&nbsp;M.K. Ashitha","doi":"10.1016/j.dsr2.2025.105468","DOIUrl":"10.1016/j.dsr2.2025.105468","url":null,"abstract":"<div><div>The measurements of net particulate primary production (NPP) with reference to space and time are limited in the Indian Ocean. Therefore, models are the only source of understanding spatial, temporal, and long-term variations. Different models have been developed to use remote sensing data to estimate NPP in the Indian Ocean. However, the accuracy of these models has not been evaluated. Here, we used the measured NPP data collected between 2003 and 2022 in the Indian Ocean to compare with different models such as Vertically Generalized Production (VGPM), Carbon-based Production (CbPM), Eppley-VGPM, and Carbon, Absorption, Fluorescence, Euphotic resolved (CAFE) models. This comparison suggested that CbPM simulated NPP with 10% underestimation compared to measured NPP in the Arabian Sea and South Indian Ocean (SIO), whereas VGPM simulated NPP well in the Bay of Bengal (BoB). The Eppley-VGPM over (under) estimated measured NPP by 20–30% in the SIO (Arabian Sea), while the CAFE model underestimated NPP in the BoB by 25%. No single model simulated the NPP well in the entire Indian Ocean compared to the measurements. All models reproduced seasonality in the Arabian Sea and SIO, but they failed in the case of the BoB. Compared to the measured NPP, the VGPM and CAFE models underestimated NPP, whereas the CbPM and Eppley-VGPM models overestimated it. Variable rates of changes in NPP in the past two decades were simulated in the Indian Ocean by different models. The long-term trends simulated by CbPM suggest decreasing trends in NPP south of 12°N and no trends north of 12°N in the Arabian Sea and increasing trends in NPP south of 20°S and decreasing trends north of 20°S in the SIO. The VGPM model indicated no significant trends in the BoB. The trends by the other models are variable and contrast in some regions. Therefore, the selection of an appropriate model to study long-term trends in NPP in the Indian Ocean is crucial.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105468"},"PeriodicalIF":2.3,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601498","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":"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":"2025-02-27","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":"Variable photosystem II thermal stress responses of reef-building corals Pocillopora indiania and Heliopora coerulea across latitudes from the Mascarene Plateau, Indian Ocean","authors":"Vikash Munbodhe ,&nbsp;Sundy Ramah ,&nbsp;Deepeeka Kaullysing ,&nbsp;Shakeel Yavan Jogee ,&nbsp;Mariette Dine ,&nbsp;Bryan Wilson ,&nbsp;Ranjeet Bhagooli","doi":"10.1016/j.dsr2.2025.105467","DOIUrl":"10.1016/j.dsr2.2025.105467","url":null,"abstract":"<div><div>The persistence of remote reef sites invariably depends on the ability of their corals to better respond and adapt to a continuing global environmental change, by way of their protection from additional and direct stressors as a result of their remoteness; such reefs are generally referred to as coral refugia. This study investigated the latitudinal thermal thresholds of two commonly occurring corals from reefs both remote from and close to human population centres, in the understudied Mascarene Plateau (MP), Central Indian Ocean. Thermal experimental trials at 26, 29 and 32 °C for a period of 22h focused on reef-building conspecifics: the regionally-endemic hard coral <em>Pocillopora indiania,</em> and heat-tolerant photo-physiologically understudied and threatened octocoral <em>Heliopora coerulea</em> from three sites of varying degrees of remoteness and human impact (Saya de Malha (SDM), St Brandon (SB) and Mauritius Island (MAU)), each with varying mean sea surface temperature (SST). Imaging Pulse-Amplitude-Modulation (Imaging-PAM) fluorometry was used to determine how the photosynthetic performances at the Photosystem II (PSII), in terms of effective quantum yield (Φ_PSII), of the conspecifics responded after exposure to these different temperature regimes. SST anomaly over the past 28 years showed an increment of 1.2 °C with no significant latitudinal variation within the MP. Moreover, the experimental results displayed significant differences in intra- and interspecific Φ_PSII when corals were exposed to 32 °C (p &lt; 0.0001); <em>P. indiania</em> from MAU suffered severe bleaching (over 90% surface area), with the highest degree of tissue sloughing leading to coral mortality, while conspecifics from SDM and SB exhibited better thermal threshold by being photosynthetically active, with 23% and 33% Φ_PSII, respectively. In contrast, <em>H. coerulea</em> from MAU thrived through the experiment indicating site-specific thermal threshold by displaying the lowest Φ_PSII (24%) as compared to conspecific from SDM (48%) and SB (58%). Although limited to Photosystem II responses, this study provides a first insight on the latitudinal variability in thermal vulnerability of conspecific corals from the MP and suggesting that corals from SDM and SB might be more resilient to the impacts of future warming events than corals at other sites.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105467"},"PeriodicalIF":2.3,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562732","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":"Impact of desalination plant brine discharge on macrobenthic communities in the Persian Gulf","authors":"Moslem Sharifinia,&nbsp;Mehrzad Keshavarzifard,&nbsp;Parisa Hosseinkhezri","doi":"10.1016/j.dsr2.2025.105465","DOIUrl":"10.1016/j.dsr2.2025.105465","url":null,"abstract":"<div><div>This research investigates the ecological impacts of desalination plant discharges on sediment quality and macrobenthic communities in the coastal waters of Bushehr City, Iran, located within the Persian Gulf. Spanning from November 2019 to October 2020, the study involved meticulous sampling of 288 sediment samples from 24 strategically selected stations—half of which were influenced by brine discharges from a desalination facility releasing approximately 45,000 cubic meters of treated wastewater daily, while the other half served as controls. The study employed a comprehensive methodology that integrated fieldwork focused on macrobenthos as biological indicators. A total of 62 macrobenthic taxa were identified, with a notable diversity of mollusks, including 35 gastropod taxa, which represented 56% of the total abundance. The application of ecological indices, including the AZTI Marine Biotic Index (AMBI), Margalef's richness, Shannon-Wiener diversity, and Pielou's evenness, revealed significant declines in biodiversity metrics near discharge points, highlighting the detrimental effects of pollution. Statistical analyses confirmed a negative correlation between the AMBI index and both the Shannon and Margalef indices, while a positive association was observed between the AMBI index and total organic matter (TOM), highlighting its effectiveness in assessing organic enrichment. These findings emphasize the complex interplay between ecological health indicators and environmental stressors, such as salinity, and highlight the importance of utilizing biological indices within coastal management frameworks. Ultimately, this research provides critical insights for developing targeted strategies to enhance the sustainable management of coastal ecosystems, ensuring the preservation of biodiversity and ecological integrity in the face of anthropogenic pressures.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105465"},"PeriodicalIF":2.3,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143471556","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":"Introducing a new method to determining the capacity of heavy metal absorption by macro algae on the coast of Persian Gulf based on Kullback-Leibler cumulative information","authors":"Mehdi Bibak ,&nbsp;Saeid Tahmasebi ,&nbsp;Eisa Safavi ,&nbsp;Najmaldin Ezaldin Hassan","doi":"10.1016/j.dsr2.2025.105466","DOIUrl":"10.1016/j.dsr2.2025.105466","url":null,"abstract":"<div><div>Researchers have continuously sought effective and affordable ways to address contamination. Application of both live and deceased algae biomass has emerged as a highly effective and promising approach for remediation. In this study, the efficacy of macroalgal species (<em>Padina gymnospora</em>, <em>Cladophoropsis membranacea</em>, and <em>Hypnea hamulosa</em>) harvested from the northern coast of the Persian Gulf was evaluated for their capacity to biosorb heavy metals, with a focus on nickel, lead, cadmium, and mercury. The study encompassed two key components. Firstlythe experimental methodology was meticulously design using Design-Expert software. Secondly, a novel approach involving – the analysis of scanning electron microscope (SEM) images of the algae was introduced, employing a measure known as cumulative Kullback–Leibler information. The results showed that <em>P. gymnospora</em> is capable of removing 50% of Pb. The highest percentage of Cd removal was observed in <em>H. hamulosa</em> (86.44%), while the highest percentage of Hg removal was recorded in <em>C. membranacea</em> (50%). Both, the experimental and analysis of image methods yielded consistent findings, corroborating their reliability. Based on the findings of this study, image analysis employing cumulative Kullback–Leibler information presents a novel and cost effective means of assessment, contributing to the arsenal methods available for contamination treatment.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"221 ","pages":"Article 105466"},"PeriodicalIF":2.3,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143487678","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":"2025-02-10","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}

{"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":"2025-02-07","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":"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":"2025-02-06","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":"2025-02-06","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":"Estimating quantitative gear and taxa specific encounter thresholds for commercial fisheries bycatch of vulnerable marine ecosystem indicator taxa","authors":"Christopher N. Rooper ,&nbsp;Kayleigh Somers ,&nbsp;Pamela Goddard ,&nbsp;Glenn Campbell","doi":"10.1016/j.dsr2.2024.105448","DOIUrl":"10.1016/j.dsr2.2024.105448","url":null,"abstract":"<div><div>Corals and sponges are often a component of vulnerable marine ecosystems (VMEs) in the deep sea. These taxa can be impacted and removed by bottom contacting fishing gear and protecting VMEs is an important component of managing ecosystems. One of the tools that is routinely used to manage VME impacts from fishing gear is move-on rules triggered by bycatch thresholds (encounter thresholds) of VME. Usually, these bycatch thresholds are set with little information regarding the level of impact on the benthic habitat. The objective of this analysis was to develop and apply methods for quantifying threshold catches of VME indicator taxa by gear type and VME indicator taxa grouping. Three previously used methods based on cumulative bycatch distributions and one novel method based on percentile regression of fishery bycatch and density from underwater camera surveys were applied to data from the northeast Pacific Ocean to determine data-based encounter thresholds that could trigger spatial fishery closures. The percentile regression method suggested encounter thresholds of ∼40–65 kg of Antipatharia, &lt;20 kg of gorgonians and 78–131 kg of Porifera would equate to a density of 0.2 VME indicator taxa per <span><math><mrow><msup><mi>m</mi><mn>2</mn></msup></mrow></math></span> for bottom trawl bycatch. Threshold values were lower for longline and pot gear (generally &lt;10 kg per set). Using the percentile regression method allowed for the definition of VME encounter thresholds to be expressed in terms of density of the taxa of interest, an improvement over examination of break points in the cumulative bycatch data alone. This improvement allows the ecological importance (e.g. density of VME) to be defined and used to estimate encounter thresholds, rather than assuming that the natural break points in cumulative bycatch represent an ecological break point.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"219 ","pages":"Article 105448"},"PeriodicalIF":2.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161548","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}