Limnology and Oceanography: Methods最新文献

{"title":"Trace analysis of volatile fatty acids in marine waters using modern high-pressure ion chromatography","authors":"Samuel I. Pereira,&nbsp;Bo Emilsson,&nbsp;Eoghan P. Reeves","doi":"10.1002/lom3.10686","DOIUrl":"https://doi.org/10.1002/lom3.10686","url":null,"abstract":"<p>Volatile fatty acids (VFAs) are key intermediates in carbon transformation in marine environments and feature widely in models for a hydrothermal origin of life. Quantifying VFAs in hydrothermal fluids is challenging due to their trace concentrations and the high inorganic ion loads of these matrices. Previous methods often rely on manual sample pre-treatment or complex instrumentation (e.g., mass spectrometry), increasing contamination risks, consumable use, and costs. To circumvent such challenges, we developed a simplified quantification method for trace VFAs in seawater-like matrices using a modern high-pressure ion chromatography (HPIC) system. This approach utilizes single-dimension ion exchange chromatography with conductivity detection alone, and a choice of two analytical column options to separate formate, acetate, propionate, butyrate, valerate, pyruvate, and lactate (measured as ∑anion) from inorganic anions. Modern HPIC systems, in addition to being versatile for other analytes (e.g., cations, nutrients), enable higher peak resolution and increased ion exchange capacity, and our tests show this allows for significantly greater trace VFA sensitivity than previous techniques. With careful sample handling and contamination control, our method achieves better absolute limits of detection for smaller sample requirements (≤ 0.3 mL), statistically determined to be below 10 ppb (~ 0.05 <i>μ</i>mol/kg for ∑formate, ~ 0.03 <i>μ</i>mol/kg for ∑acetate). Additionally, our study provides detailed insights into limiting VFA contamination sources, as well as their stability in storage. Initial analysis of hydrothermal fluids from the Arctic Mid-Ocean Ridges reveals formate (0.6–7.3 <i>μ</i>mol/kg) controlled by metastable CO₂–H₂–HCOOH equilibrium, and unexpectedly low acetate (2.6–5.8 <i>μ</i>mol/kg), likely reflecting competition between thermogenic formation and stability.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 6","pages":"389-412"},"PeriodicalIF":2.1,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144245021","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":"Assessing the applicability of sequential eye lens stable isotope analysis for reconstructing dietary histories in amphibians","authors":"Arisa Shiga,&nbsp;Jun Matsubayashi,&nbsp;Nanako O. Ogawa,&nbsp;Naohiko Ohkouchi,&nbsp;Noriko Iwai","doi":"10.1002/lom3.10689","DOIUrl":"https://doi.org/10.1002/lom3.10689","url":null,"abstract":"<p>Retrospective isotope analysis using metabolically inert tissues is a powerful tool for reconstructing historical environmental conditions experienced by animals. Although this technique has been successfully applied to fish and squids using eye lenses, its applicability to metamorphosing organisms, such as amphibians, across multiple life-history stages has not been thoroughly assessed. In this study, we examined whether stable isotope ratios in frog eye lenses reflect dietary data from both the larval and post-metamorphic stages through feeding trials of two species, <i>Rana ornativentris</i> and <i>Babina subaspera</i>, using diets with distinct <i>δ</i>¹³C values. Additionally, we analyzed samples collected from the wild and assessed the potential future use of this method. Our feeding trials demonstrated that δ¹³C values in the central and outer lens sections were closely aligned with the larval and adult food, respectively, confirming the applicability of the method. The transition point of stable isotope ratios was closely aligned with the actual metamorphosis point, indicating that this method can effectively identify metamorphosis. However, the two wild specimens exhibited no discernible patterns in isotope ratios across their life stages. This indicates that applying this method in the field requires careful selection of the environmental conditions and a comprehensive understanding of the stable isotope ratios of potential food sources.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 5","pages":"336-345"},"PeriodicalIF":2.1,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143950226","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":"MARS: Programmable multipurpose auto-release system for aquatic observations","authors":"Marko Radeta,&nbsp;João Gama Monteiro,&nbsp;João Pestana,&nbsp;Dinarte Vieira,&nbsp;Pedro Abreu,&nbsp;Rodrigo Silva,&nbsp;Susanne Schäfer,&nbsp;Patrício Ramalhosa,&nbsp;Ana Lopez Martos,&nbsp;Bruno Loureiro,&nbsp;Nuno Queiroz,&nbsp;Rui Seabra,&nbsp;Fernando P. Lima,&nbsp;João Canning-Clode","doi":"10.1002/lom3.10688","DOIUrl":"https://doi.org/10.1002/lom3.10688","url":null,"abstract":"<p>Aquatic biodiversity assessments are often labor-intensive due to the large size of the equipment and the complex logistics of sea vessel operations. Traditional drift and drop cameras are typically tethered to the surface, causing cable and line clutter on sea vessels. At the same time, landers rely on auto-release mechanisms that use costly acoustic signals or inaccurate galvanic reactions. We introduce a reusable, novel, and low-cost Multipurpose Auto-Release System, a versatile and programmable solution for diverse payloads and applications in shallow and mesophotic waters. Building on existing drop-cam and Baited Remote Underwater Video System techniques, we enhance them with natural ballasts and an electronically controlled timed-release mechanism, which is programmed via a smartphone app using Near Field Communication. Our technique allows tetherless retrieval from small sea vessels at the sea surface. This innovation simplifies aquatic monitoring logistics by eliminating the need for surface buoys or equipment retrieval from the seabed during each deployment. Our approach also advances benthic and deep-sea marine biodiversity assessments by enabling easy systems deployment and recapture without pingers. We validated the system through 10 seawater tests, reaching depths of 278 m, accumulating 6 h of submerged data collection, and 17 d during continuous water immersion. We provide a detailed guide for building this robust, reusable, user-friendly tool for diverse aquatic monitoring assessments. Additionally, we share key lessons learned, paving the way toward more democratized, customizable, and widely accessible applications capable of reaching the deepest seas.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 6","pages":"376-388"},"PeriodicalIF":2.1,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10688","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144245035","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":"Enhancing sampling of dissolved N2O in aquatic systems: Field-deployable automated gas bag collection system","authors":"Mohammad Arar,&nbsp;Timothy J. Clough,&nbsp;Naomi S. Wells","doi":"10.1002/lom3.10687","DOIUrl":"https://doi.org/10.1002/lom3.10687","url":null,"abstract":"<p>Measuring dissolved nitrous oxide (N₂O), a potent greenhouse gas and contributor to ozone depletion, is essential for understanding its aquatic dynamics and informing climate mitigation and emission estimates. Dissolved N₂O concentration measurements typically involve headspace equilibration of water samples in sealed containers, followed by gas chromatography analysis. This manual method is labor-intensive and often requires toxic preservatives. Alternatively, air-water exchangers coupled with laser analyzers provide high-precision continuous measurements but lack sample storage capabilities and require frequent relocation and setup to capture spatiotemporal variations. We developed an automated gas bag (AGB) collection system for collecting N₂O samples (AGB-N₂O) from discrete water samples, which could then be analyzed for concentration using laser analyzers. This method combines the field-friendly sample collection and storage of the manual method with the precision of exchangers and laser analyzers. Field experiments tested four setups of exchangers with varying internal volumes (2 L vs. 1 L) and water flow rates (small nozzle: 0.75 L min⁻¹ vs. medium nozzle: 3 L min⁻¹) at sites with low vs. high N₂O concentrations (13 nM vs. 95 nM). The 2-L exchanger with a medium nozzle achieved the fastest equilibration times of 2.25 and 0.08 min for high and low N₂O sites, respectively. The AGB-N₂O showed comparable results to the manual method for measuring dissolved N₂O concentrations (<i>p</i> &gt; 0.05). However, the AGB-N₂O demonstrated significantly lower standard deviations, indicating higher precision and consistency. These findings demonstrate the suitability of the AGB-N₂O for diverse aquatic environments, offering reliable and efficient N₂O measurements.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 6","pages":"363-375"},"PeriodicalIF":2.1,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10687","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144245002","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":"Particulate inorganic carbon in the ocean: Evaluation of discrete sampling protocols","authors":"Catherine Mitchell,&nbsp;Jelena Godrijan","doi":"10.1002/lom3.10683","DOIUrl":"https://doi.org/10.1002/lom3.10683","url":null,"abstract":"<p>This study evaluates the impact of sampling protocols on the measurement of particulate inorganic carbon (PIC) in ocean waters, an essential component for understanding the global carbon cycle and climate regulation. The study compares four protocols for estimating PIC in discrete water column samples, focusing on the effects of filter pore size (0.4 vs. 0.8 <i>μ</i>m) and rinsing agents (pH-adjusted MilliQ water with NH₄OH vs. potassium tetraborate buffer). Five coccolithophore strains were selected to represent variations in PIC content resulting from species-specific differences in coccolith mass, coccolith number per cell, and life cycle phase. Discrete samples were analyzed using inductively coupled plasma mass spectrometry. Statistical analyses show no significant differences in PIC concentrations between protocols, filter types, or rinsing agents, confirming the robustness and precision of the measurement method. In addition, the non-calcifying strain provided insights into the measurement uncertainty and enabled us to quantify the precision of the sampling method. These results suggest that researchers can use any tested protocol without compromising data quality. This will improve the reliability and comparability of PIC measurements and contribute to a more precise understanding of ocean carbon dynamics and climate regulation.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 5","pages":"326-335"},"PeriodicalIF":2.1,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10683","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949779","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":"DISCO: A low-cost device-instrumented Secchi disk for water clarity observations","authors":"Gaia Donini,&nbsp;Sebastiano Piccolroaz","doi":"10.1002/lom3.10684","DOIUrl":"https://doi.org/10.1002/lom3.10684","url":null,"abstract":"<p>Water clarity regulates irradiance penetration in aquatic environments, influencing physical and biological dynamics: irradiance penetration affects heat transfer in the water column and provides energy through photosynthetically active radiation (PAR) in the euphotic zone, which is vital for light-dependent organisms. The ability to accurately assess water clarity is therefore important in several aquatic science contexts, from data analysis and process interpretation to modeling. Common metrics used to quantify water clarity include the vertical irradiance attenuation coefficient <span></span><math>\u0000 <mrow>\u0000 <mi>K</mi>\u0000 </mrow></math>, a measure of irradiance penetration, and the Secchi disk depth (<span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>z</mi>\u0000 <mi>SD</mi>\u0000 </msub>\u0000 </mrow></math>), a measure of water visibility. The enduring simplicity and low cost of the Secchi disk has made it a global standard for measuring water clarity for almost two centuries. In contrast, <span></span><math>\u0000 <mrow>\u0000 <mi>K</mi>\u0000 </mrow></math> is typically determined using expensive instruments that measure underwater irradiance profiles. This highlights the need for innovative, cost-effective methods that integrate both types of measurements. Here we present DISCO, a low-cost, easy-to-build instrument that retains the traditional appearance of a Secchi disk, and is equipped with photoresistors (also known as light-dependent resistors, LDRs) both looking upwards and downwards for planar irradiance measurements. DISCO is also equipped with low-cost temperature and pressure sensors, all connected to an ArduinoUNO board. DISCO was tested in two mountain lakes together with high resolution PAR, temperature and pressure sensors to calibrate the LDRs and validate its performance. The results show that the proposed instrument is able to measure the irradiance attenuation coefficients with an error of less than 10<span></span><math>\u0000 <mrow>\u0000 <mo>%</mo>\u0000 </mrow></math> compared to the reference PAR sensor.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 5","pages":"346-361"},"PeriodicalIF":2.1,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10684","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143950279","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":"Fast responses, rich insights: Optimizing experimental stream studies using periphyton for comprehensive environmental assessment","authors":"Luciane Ayres Castro Reis,&nbsp;Gilberto Fonseca Barroso","doi":"10.1002/lom3.10681","DOIUrl":"https://doi.org/10.1002/lom3.10681","url":null,"abstract":"<p>Experimental streams (ESs) are enclosures of fluvial ecosystems designed as flume microcosms to simulate flowing waters and assess environmental disturbances on aquatic communities' structure and function under controlled conditions. This study presents an ES system that combines ecological relevance with reliability in a compact design, offering rapid responses to iron ore tailings. The system used periphyton biofilm as a bioindicator in a recirculating flume microcosm over 65 d. Periphyton is a key bioindicator, representing critical aquatic metabolic processes such as primary production. The system includes artificial glass channels, microscope slide substrates, and recirculating pumps. It was developed with replicates, three controls, and three treatments, each consisting of a main channel and a water reservoir, for a total volume of 10.0 L. Six sampling campaigns evaluated periphyton biofilm and water quality indicators under acute, short, and long-term exposures. The system's reliability is ensured by standardizing setup conditions, maintaining river water properties, ensuring uniform flow, and standardizing slide sampling. Realism is achieved by renewing large water volumes, regular inoculation of periphyton propagules, and the appropriate sampling frequency for periphyton and water quality. The results showed that the ES, a simple and low-cost system (US$569), was sensitive to indicators throughout the exposure period. This approach is practical for assessing various aquatic stressors.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 5","pages":"309-325"},"PeriodicalIF":2.1,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10681","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143950259","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":"Retrieving vertical phytoplankton functional types in the South China Sea and adjacent Taiwan Strait based on phytoplankton absorption spectra and machine learning","authors":"Qing Zhu,&nbsp;Zhongping Lee,&nbsp;Wupeng Xiao,&nbsp;Bangqin Huang,&nbsp;Gong Lin","doi":"10.1002/lom3.10679","DOIUrl":"https://doi.org/10.1002/lom3.10679","url":null,"abstract":"<p>Phytoplankton functional types (PFTs) found in natural aquatic environments play different roles in the biogeochemical cycles of different elements. However, commonly used methods for identifying PFTs have inherent limitations. In this study, based on a large dataset (1747 samples) collected from 2004 to 2019 in the South China Sea and adjacent Taiwan Strait, which had concurrent measurements of the spectral absorption coefficient of phytoplankton and chlorophyll <i>a</i> concentration of nine PFTs (PFTs_Chla), along with depth and time information, a reliable support vector regression (SVR) model was developed to retrieve these nine PFTs_Chla in the water column. These PFTs included diatoms, dinoflagellates, haptophytes_8, haptophytes_6, chlorophytes, cryptophytes, <i>Prochlorococcus</i>, <i>Synechococcus</i>, and prasinophytes. The independent validation results indicated that the SVR model outperformed the traditional PFTs_Chla retrieval algorithms, with an average mean bias of −14.2%, an average mean absolute unbiased relative difference of 60.3%, and an average coefficient of determination of 0.56. The predicted PFTs_Chla values and their error distributions in the water column were subsequently analyzed. Finally, the SVR model was found to be applicable to most PFTs_Chla retrieval in the East China Sea.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 4","pages":"223-245"},"PeriodicalIF":2.1,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749659","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":"FISH, a new tool for in situ preservation of RNA in tissues of deep-sea mobile fauna","authors":"Valérie Cueff-Gauchard,&nbsp;Johanne Aubé,&nbsp;Jean-Romain Lagadec,&nbsp;Laurent Bignon,&nbsp;Jean-Pierre Lafontaine,&nbsp;Iván Hernández-Ávila,&nbsp;Nathalie Marsaud,&nbsp;Bruce Shillito,&nbsp;Louis Amand,&nbsp;Erwan G. Roussel,&nbsp;Marie-Anne Cambon","doi":"10.1002/lom3.10677","DOIUrl":"https://doi.org/10.1002/lom3.10677","url":null,"abstract":"<p>Accessing the metabolic functioning of deep-sea animals in situ remains a technological challenge as the recovery time of samples is incompatible with the short lifespan of such molecules as mRNAs. Tools able to preserve RNA in situ exist, but they are incompatible with the study of mobile fauna. Here, we describe a new sampling tool, named FISH (fixer in situ of homogenized substrates), implemented on a submersible and equipped with a number of new specific features to collect and preserve in situ tissue of mobile fauna. Connected to the suction pump of a submersible, the FISH sampler incorporates a sampling bowl to which two bottles of a preservative reagent are attached, a suction hose, and a support containing a motor connected to the sampling bowl by a magnetic coupling system. We used the deep-sea hydrothermal shrimp <i>Rimicaris exoculata</i> from the Mid-Atlantic Ridge as a model to test the suitability of our new tool. The FISH sampler was compared to two other sampling methods, which use a metatranscriptomic approach targeting microbial communities associated with cephalothorax symbionts. RNA quality, gene assignment, and taxonomic and gene function diversity showed differences between in situ and on-board preservation of tissues. Of the alternative sampling methods tested, the suction sampler was clearly not suitable for RNA-based studies, while pressurized recovery showed results closer to the sample quality obtained with FISH sampling. The FISH sampler has therefore demonstrated to be a cost-effective and reliable tool to efficiently preserve RNA recovered from deep-sea environments.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 4","pages":"273-292"},"PeriodicalIF":2.1,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lom3.10677","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749822","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 phytoplankton primary production by coupling pulse amplitude modulation and incubation methods","authors":"Yichong Wang,&nbsp;Wupeng Xiao,&nbsp;Chengwen Xue,&nbsp;Yaqin Zhang,&nbsp;Chao Xu,&nbsp;Weinan Li,&nbsp;Mingwang Xiang,&nbsp;Chun Yang,&nbsp;Jixin Chen,&nbsp;Bangqin Huang","doi":"10.1002/lom3.10678","DOIUrl":"https://doi.org/10.1002/lom3.10678","url":null,"abstract":"<p>Pulse amplitude modulation (PAM) fluorometry provides high-resolution and high-frequency primary production (PP) estimates, crucial for understanding and managing dynamic ecosystems such as estuaries. However, traditional PAM-derived PP estimations often overlook the variability of the photosynthetic quotient and the dynamics of chlorophyll <i>a</i>, leading to uncertainties. This study introduced an innovative method for estimating the PP of natural phytoplankton communities using the rapid light curve of PAM measurements. Validation using ¹⁴C incorporation and oxygen techniques in two subtropical estuaries demonstrated a strong linear relationship between PAM-derived PP and measured oxygen evolution rates (<i>R</i>² = 0.76, <i>p</i> &lt; 0.001) and carbon fixation rates (<i>R</i>² = 0.94, <i>p</i> &lt; 0.001). While the dynamics of chlorophyll <i>a</i> had minimal impact on hourly PAM-derived PP estimations, they caused significant deviations on daily time scales, influenced by sampling times. Predicting photosynthetic quotient values based on salinity (<i>R</i>² = 0.34, <i>p</i> &lt; 0.05) allowed for expanded temporal and spatial PP estimations. Seasonal PP patterns in the Jiulong River Estuary, Xiamen Bay, Zhangjiang Estuary, and Dongshan Bay revealed the highest PP in summer, followed by spring, with similar levels in autumn and winter. Using these surface measurements, annual phytoplankton carbon fixation fluxes were estimated through the entire water column across the four regions. This method provides a more comprehensive understanding of PP dynamics, highlighting its potential for frequent application in small-scale valuable ecosystems like estuaries and bays to better assess their ecological functions and biogeochemical cycles.</p>","PeriodicalId":18145,"journal":{"name":"Limnology and Oceanography: Methods","volume":"23 4","pages":"293-308"},"PeriodicalIF":2.1,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143749905","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}