Posts Tagged 'methods'

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Shellfisheries’ adaptation to ocean acidification in OR and CA: linking strategies to strategic policy action

Published 18 November 2024 Science Closed
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Highlights

  • Policies are currently in place to support adaptive capacity of shellfish growers in California and Oregon.
  • Both specific and broad policies pertaining to OA, and shellfish aquaculture, offer multiple places to develop greater adaptive capacity.
  • Reducing institutional barriers to daily operations will help shellfish growers’ adaptation as more efforts can be directed to adaptive strategies.
  • Continued and expanded communication between agencies, scientists and shellfish growers provide pathways to explore adaptation to OA.

Abstract

As ocean pH levels continue to decline due to increased absorption of atmospheric CO2, a process known as ocean acidification (OA), industries dependent on ocean resources must adapt to mitigate negative impacts of OA. Utilizing adaptive strategies identified by shellfish growers in prior, related research, we seek to explore and identify existing U.S. State and Federal policies that pertain to OA, how they might impact the ability for shellfish growers in California (CA) and Oregon (OR) adapt to OA, and where there are opportunities for policy expansion to improve their capacity to adapt to OA. Potential pathways linking adaptation needs with policy processes is discussed.

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Sustainable Development Goal (SDG) 14.3.1 Indicator Quick Guide

Published 16 October 2024 Science Closed
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Submitting data to assess OA globally

Background

In 2015, the United Nations adopted the 2030 Agenda and a set of Sustainable Development Goals (SDG), including a goal dedicated to the ocean, SDG 14, which calls to “conserve and sustainably use the oceans, seas, and marine resources for sustainable development”. Under this SDG 14, there are 10 Targets addressing a range of ocean issues and 10 Indicators, which are the measurable components of the Target. The Intergovernmental Oceanographic Commission (IOC) of UNESCO was identified as the custodian agency for the SDG Target 14.3: “Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels”, and the associated SDG Indicator 14.3.1 (“Average marine acidity (pH) measured at agreed suite of representative sampling stations”).

The SDG 14.3.1 Indicator Methodology provides the necessary guidance on how to conduct ocean acidification observation. The Methodology contains guidance on sampling strategy, measurement methods and calculation, methodology and instrumentation, links to community agreed Best Practices and Standard Operating Procedures, data quality categories and data quality control mechanism as well as recommendations for the calculation of the seawater carbonate system, including how to account for the uncertainty of measurements. It further offers support on how to and what kind of data sets to submit to IOC, to ensure the production of quality-controlled global and possibly regional products of surface ocean acidification.

The full text of the Methodology as well as the data template, the metadata template and the metadata instructions files can be downloaded from the SDG 14.3.1 Data Portal website (https://oa.iode.org/). The SDG 14.3.1 Data Portal is a tool for the submission, collection, validation, storage, and sharing of ocean acidification data and metadata submitted towards the SDG 14.3.1 Indicator.

This present document is an introduction to the SDG 14.3.1 Methodology, providing an introduction to some aspects of the guidance provided within the Methodology. This document should therefore not replace the Methodology; please make sure to read and apply the SDG 14.3.1 Methodology elaborated here.

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Data driven models for predicting pH of CO2 in aqueous solutions: implications for CO2 sequestration

Published 7 October 2024 Science Closed
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Highlights

  • Fifteen machine learning models developed to predict pH of CO2 in aqueous solutions.
  • Error factors, cross plots and KDE plots were employed to evaluate models.
  • Boosted trees optimized with grid search recognized as the most accurate model.
  • Models based on boosted trees and GPR outperformed all other models.
  • Solubility of CO2 and salinity had the greatest and lowest impact on pH respectively.

Abstract

Changes in pH during CO2 injection into oceans can lead to significant negative environmental impacts, making it particularly important to track these changes. However, previous studies have not comprehensively investigated the development of machine learning models to estimate this parameter. To fill this research gap, this study developed 15 models comprising five machine learning methods: regression trees, support vector regression, Gaussian process regression, bagged trees, and boosted trees, and three optimization algorithms: random search, grid search, and Bayesian optimization. A total of 170 data points were used to develop these models. After data preprocessing and model development, it was determined that the boosted trees model optimized with grid search, with an R2 = 0.9964 and RMSE = 0.0156, performed the best, while the support vector regression model optimized with random search, with an R2 = 0.8426 and RMSE = 0.1030, had the lowest accuracy. The boosted trees model optimized with grid search was found to estimate all data points with a residual error of less than 0.15 and an absolute relative error of 4.62 %. The 95 % confidence interval for the RMSE was calculated based on the best model, showing that the error lies between 0.009060 and 0.023256 with 95 % confidence. Pearson correlation analysis was used for sensitivity analysis. The results showed that in all models, temperature, solubility, and pressure have a negative correlation with pH, while salinity has a positive correlation. Additionally, solubility and salinity exhibited the highest and lowest correlations, with average values of −0.9225 and 0.0594, respectively. Due to the accuracy of the developed models, these models can help to optimize the operation of injecting CO2 into oceans to reduce harmful environmental effects.

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An update of data compilation on the biological response to ocean acidification and overview of the OA-ICC data portal

Published 29 August 2024 Science Closed
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The number of studies investigating the effects of ocean acidification on marine organisms and communities increases every year. Results are not easily comparable since the carbonate chemistry and ancillary data are not always reported in similar units and scales and are not calculated using similar sets of constants. To facilitate data comparison, a data compilation hosted by the PANGAEA Data Publisher was initiated in 2008 and is updated on a regular basis (https://doi.org/10.1594/PANGAEA.962556; Ocean Acidification International Coordination Centre (OA-ICC), 2023). By November 2023, a total of 1501 datasets (over 25 million data points) from 1554 papers had been archived. To easily filter and access relevant biological response data from this compilation, a user-friendly portal (https://oa-icc.ipsl.fr, last access: 9 November 2023) was launched in 2018. Here, we present an update of this data compilation since its second description by Yang et al. (2016) and provide an overview of the OA-ICC portal for ocean acidification biological response data, launched in 2018. Most of the study sites from which data have been archived are in the North Atlantic Ocean, North Pacific Ocean, South Pacific Ocean, and Mediterranean Sea, while polar oceans are still relatively poorly represented. Mollusca and Cnidaria are still the best-represented taxonomic groups. The biological processes most reported in the datasets are growth and morphology. Other variables that can potentially be affected by ocean acidification and are often reported include calcification/dissolution, primary production/photosynthesis, and biomass/abundance. The majority of the compiled datasets have considered ocean acidification as a single stressor, but their relative contribution has decreased from 68 % before 2015 to 57 % today, showing a clear tendency towards more data archived from multifactorial studies.

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The development research on marine ecological environment online monitoring equipment system in China

Published 28 August 2024 Science Closed
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Highlights

  • The concept of “system of systems” was introduced to marine ecological environment online monitoring equipment system, to help analyzing the applications of online monitoring systems
  • The hierarchical structure and functional structure of equipment “system of systems” were established, in order to discuss how to build an appropriate monitoring system for different scenarios
  • Methods for improving the accuracy, stability, and reliability of marine ecological environment monitoring systems were discussed

Abstract

There is an urgent need for marine ecological environment monitoring in China at present, but the traditional manual periodic sampling and testing has such disadvantages as low monitoring frequency and limited station coverage, which could not meet the requirements of large-scale real-time continuous data for current marine ecological early-warning monitoring. Therefore, constructing the multi-level, multi-system, and multi-space marine ecological environment online monitoring system could effectively develop marine ecological environment early-warning monitoring capacity. In this paper, the concept of “System of Systems” was introduced into the construction of marine ecological environment online monitoring equipment system, and the architecture of “System of Systems” of the monitoring equipment was constructed from two layers, structure layer and function layer. The composition of the two layers, and the difficulties in construction of the two layers were emphatically discussed. The paper also analyzed the methods of developing “System of Systems” of marine ecological environment online monitoring system.

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Dual-Lifetime referencing (t-DLR) optical fiber fluorescent pH sensor for microenvironments

Published 23 August 2024 Science Closed
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The pH behavior in the μm to cm thick diffusion boundary layer (DBL) surrounding many aquatic species is dependent on light-controlled metabolic activities. This DBL microenvironment exhibits different pH behavior to bulk seawater, which can reduce the exposure of calcifying species to ocean acidification conditions. A low-cost time-domain dual-lifetime referencing (t-DLR) interrogation system and an optical fiber fluorescent pH sensor were developed for pH measurements in the DBL interface. The pH sensor utilized dual-layer sol-gel coatings of pH-sensitive iminocoumarin and pH-insensitive Ru(dpp)3-PAN. The sensor has a dynamic range of 7.41 (±0.20) to 9.42 ± 0.23 pH units (95% CI, T = 20 °C, S = 35), a response time (t90) of 29 to 100 s, and minimal salinity dependency. The pH sensor has a precision of approximately 0.02 pHT units, which meets the Global Ocean Acidification Observing Network (GOA-ON) “weather” measurement quality guideline. The suitability of the t-DLR optical fiber pH sensor was demonstrated through real-time measurements in the DBL of green seaweed Ulva sp. This research highlights the practicability of optical fiber pH sensors by demonstrating real-time pH measurements of metabolic-induced pH changes.

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Assessment of an automated titration system for batch measurements of total alkalinity

Published 16 August 2024 Science Closed
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Highlights

  • An automated titration system for TA batch measurements was evaluated
  • Sample mass, salinity, and dilution have little effect on TA measurement
  • Temperature variation within ±1 °C does not significantly affect TA measurement
  • Negative TA can be determined with high precision

Abstract

Total alkalinity (TA) is the measure of water’s ability to neutralize acids. Discrete TA samples are typically measured by acid titration, with one sample processed at a time, which is tedious and time-consuming. In this study, we assessed an automated titration system for TA batch measurements that included the washing procedure between each sample analysis; and evaluated the impact of various factors on the precision of TA measurement, including the sample mass, sample salinity, temperature variation, and the dilution effect from the residual washing water. The results showed that temperature variation within ±1 °C, salinity ranging from 0 to 40, sample mass from 20 to 30 g, and the residual washing water within 2 g did not affect the precision of TA measurement (±2 μmol/kg). In addition, the automated titration system encoded with Gran calculation managed to determine the negative TA as low as −100 μmol/kg. Our study suggests that the automated titration system with an auto-sampler is capable of high-precision TA batch measurements.

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Long-term trends of pH, alkalinity, and hydrogen ion concentration in an upwelling-dominated coastal ecosystem: Ría de Vigo, NW Spain

Published 12 August 2024 Science Closed
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The present study focuses on the Ría de Vigo (NW Spain), a coastal embayment influenced by the Canary Current Upwelling System, which is among the world’s significant Eastern Boundary Upwelling Ecosystems. The research assesses historical changes in the marine carbonate system by generating 25-year weekly time series at six stations . Assessing ocean acidification in the region is complex due to diverse factors influencing coastal carbon dynamics, making predictions more challenging. To capture the specific dynamics in Ría de Vigo, ensembles of Neural Networks were applied. These networks were trained with a data set obtained in several oceanographic cruises, in order to retrieve pH, hydrogen ion concentration and alkalinity, achieving a root mean square error of 0.0272 pH units, 0.588 nmol Kg-1, and 10.6 μμmol kg−1, respectively. Subsequently, time series of the selected variables were generated, applying data of predictors measured at the aforementioned stations . An increase in normalized alkalinity was observed for all stations, except in the surface layer at the innermost location. A decrease in pH and an increase in hydrogen ion concentration were observed for all points, with trends that exceed reported rates of ocean acidification in the open ocean.

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Site-Specific multiple stressor assessments based on high frequency surface observations and an earth system model

Published 1 August 2024 Science Closed
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Abstract

Global Earth system models are often enlisted to assess the impacts of climate variability and change on marine ecosystems. In this study, we compare high frequency (daily) outputs of potential ecosystem stressors, such as sea surface temperature and surface pH, and associated variables from an Earth system model (GFDL ESM4.1) with high frequency time series from a global network of moorings to directly assess the capacity of the model to resolve local biogeochemical variability on time scales from daily to interannual. Our analysis indicates variability in surface temperature is most consistent between ESM4.1 and observations, with a Pearson correlation coefficient of 0.93 and bias of 0.40°C, followed by variability in surface salinity. Physical variability is reproduced with greater accuracy than biogeochemical variability, and variability on seasonal and longer time scales is more consistent between the model and observations than higher frequency variability. At the same time, the well-resolved seasonal and longer timescale variability is a reasonably good predictor, in many cases, of the likelihood of extreme events. Despite limited model representation of high frequency variability, model and observation-based assessments of the fraction of days experiencing surface T-pH and T-Ωarag multistressor conditions show reasonable agreement, depending on the stressor combination and threshold definition. We also identify circumstances in which some errors could be reduced by accounting for model biases.

Key Points

  • Physical and biogeochemical variability from moorings and GFDL ESM4.1 output is most consistent on seasonal and longer time scales
  • More high frequency (daily to monthly) variability is present in observations than in ESM output
  • Despite missing high frequency variability, ESM output can be applied to accurately quantify multiple stressor events

Plain Language Summary

Ocean ecosystems are under stress from changing temperature and acidity due to the human-driven increase in global atmospheric carbon dioxide. Global Earth system models (ESMs) are used to study the effects of climate variability and change on marine ecosystems. However, computing power and storage constraints limit the level of detail represented by these simulations. Some short timescale variability present in the real world is missing from ESM output. Despite this inconsistency, we show that at an array of sites where daily observation data from ocean moorings is available, models accurately capture observed spatial patterns in estimates of the amount of time the locations experience combined temperature and acidification stress. We also demonstrate circumstances in which some model errors can be reduced through bias correction.

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Climatological distribution of ocean acidification variables along the North American ocean margins

Published 31 July 2024 Science Closed
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Climatologies, which depict mean fields of oceanographic variables on a regular geographic grid, and atlases, which provide graphical depictions of specific areas, play pivotal roles in comprehending the societal vulnerabilities linked to ocean acidification (OA). This significance is particularly pronounced in coastal regions where most economic activities, such as commercial and recreational fisheries and aquaculture industries, occur. In this paper, we unveil a comprehensive data product featuring coastal ocean acidification climatologies and atlases, encompassing the fugacity of carbon dioxide, pH on the total scale, total hydrogen ion content, free hydrogen ion content, carbonate ion content, aragonite saturation state, calcite saturation state, Revelle factor, total dissolved inorganic carbon content, and total alkalinity content. These variables are provided on 1° × 1° spatial grids at 14 standardized depth levels, ranging from the surface to a depth of 500 m, along the North American ocean margins, defined as the region between the coastline and a distance of 200 nautical miles (∼370 km) offshore. The climatologies and atlases were developed using the World Ocean Atlas (WOA) gridding methods of the NOAA National Centers for Environmental Information (NCEI) based on the recently released Coastal Ocean Data Analysis Product in North America (CODAP-NA), along with the 2021 update to the Global Ocean Data Analysis Project version 2 (GLODAPv2.2021) data product. The relevant variables were adjusted to the index year of 2010. The data product is available in NetCDF (https://doi.org/10.25921/g8pb-zy76, Jiang et al., 2022b) on the NOAA Ocean Carbon and Acidification Data System: https://www.ncei.noaa.gov/data/oceans/ncei/ocads/metadata/0270962.html (last access: 15 July 2024). It is recommended to use the objectively analyzed mean fields (with “_an” suffix) for each variable. The atlases can be accessed at https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/synthesis/nacoastal.html (last access: 15 July 2024).

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Ocean carbon sink assessment via temperature and salinity data assimilation into a global ocean biogeochemistry model

Published 31 July 2024 Science Closed
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Global ocean biogeochemistry models are frequently used to derive a comprehensive estimate of the global ocean carbon uptake. These models are designed to represent the most important processes of the ocean carbon cycle, but the idealized process representation and uncertainties in the initialization of model variables lead to errors in their predictions. Here, observations of ocean physics (temperature and salinity) are assimilated into the ocean biogeochemistry model FESOM-REcoM over the period 2010–2020 to study the effect on the air-sea CO2 flux and other biogeochemical variables. While the free running model already represents temperature and salinity rather well, the assimilation further improves it and hence influences the modeled ecosystem and CO2 fluxes. The assimilation has mainly regional effects on the air-sea CO2 flux, with the largest imprint of assimilation in the Southern Ocean during winter. South of 50° S, winter CO2 outgassing is reduced and thus the mean CO2 uptake increases by 0.18 Pg C yr-1 through the assimilation. Other particularly strong regional effects on the air-sea CO2 flux are located in the area of the North Atlantic Current. Yet, the effect on the global ocean carbon uptake is a comparatively small increase by 0.05 Pg C yr-1 induced by the assimilation, yielding a global mean uptake of 2.78 Pg C yr-1 for the period 2010–2020.

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Variability of dissolved inorganic carbon in the most extensive karst estuarine-lagoon system of the Southern Gulf of Mexico

Published 29 July 2024 Science Closed
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Coastal ecosystems with karstic geology have a unique characteristic where the dissolution of carbonate rocks can increase total alkalinity (TA) and dissolved inorganic carbon (DIC). This results in higher inorganic carbon budgets in coastal areas. One such ecosystem is the Terminos Lagoon, the most extensive tropical estuarine lagoon system in Mexico, located in the karstic aquifer of the Yucatan Peninsula and connected to the southern Gulf of Mexico (sGoM). We measured TA and DIC to evaluate the variability in Terminos Lagoon’s of the carbonate system. We also estimated pH, partial CO2 pressure (pCO2), and aragonite saturation (ΩAr) along two transects from the main lagoon tributaries (Palizada and Candelaria rivers) to the coastal zone during the dry and rainy seasons. During the dry season, TA and DIC concentrations were significantly higher (3092 ± 452 µmol kg-1 TA, 2943 ± 522 µmol kg-1 DIC) than during the rainy season (2533 ± 228 µmol kg−1 TA, 2492 ± 259 DIC µmol kg−1). Our calculations indicate that the rainy season pCO2 (2532 ± 2371 µatm) seems higher than in the dry season (1534 ± 1192 µatm). This leads to a reduction in pH (7.9 ± 0.3 to 7.8 ± 0.3). These significant changes indicate that rain increases the flow of unsaturated river water into the lagoon. The results of this work contribute toward a dissolved inorganic carbon variability baseline in the sGoM and can be helpful to Terminos Lagoon decision-makers.

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The Southern Ocean carbon sink has been overestimated in the past three decades

Published 29 July 2024 Science Closed
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Employing machine learning methods for mapping surface ocean pCO2 has reduced the uncertainty in estimating sea-air CO2 flux. However, a general discrepancy exists between the Southern Ocean carbon sinks derived from pCO2 products and those from biogeochemistry models. Here, by performing a boosting ensemble learning feed-forward neural networks method, we have identified an underestimation of the surface Southern Ocean pCO2 due to notably uneven density of pCO2 measurements between summer and winter, which resulted in about 16% overestimating of Southern Ocean carbon sink over the past three decades. In particular, the Southern Ocean carbon sink since 2010 was notably overestimated by approximately 29%. This overestimation can be mitigated by a winter correction in algorithms, with the average Southern Ocean carbon sink during 1992-2021 corrected to −0.87 PgC yr−1 from the original −1.01 PgC yr−1. Furthermore, the most notable underestimation of surface ocean pCO2 mainly occurred in regions south of 60°S and was hiding under ice cover. As the surface ocean pCO2 under sea ice coverage in the winter is much higher than the atmosphere, if sea ice melts completely, there could be a further reduction of about 0.14 PgC yr−1 in the Southern Ocean carbon sink.

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Non-traditional stable metal and metalloid isotopes and their potential applications in earth, ocean, and environmental sciences

Published 26 July 2024 Science Closed
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Highlights

  • Recent advancement has revolutionized the field of “Non-Traditional” isotopes.
  • Non-traditional isotopes provide useful tool in diverse fields.
  • Highlight challenges and perspectives of non-traditional isotopes.

Abstract

Recent technological advancement has revolutionized the field of non-traditional stable metal and metalloid isotopes for their wide applications for the study of earth surface processes, reconstructing past oceanic environments, tracing contaminants, and biomedical investigations. Beyond the conventional stable isotopes (H, C, O, N, S), this field has led to a wide exploration of stable isotopes (e.g., Li, B, Mg, Si, Ca, K, V, Cr, Ni, Fe, Cu, Zn, Sr, Mo, Cd, Ba, Hg, U) and their potential applications. This review delves into the applications of stable metal and metalloid isotopes as an important tool for tracing sources and elucidating various processes within the realm of earth, ocean, and environmental studies. The fundamental concept of mass-dependent and -independent isotope fractionations are introduced firstly; the selected “emerging” stable isotopes like Li isotopes (δ7Li), B isotopes (δ11B), and Mo isotopes (δ98Mo) are discussed; their applications as a proxy for earth surface processes, paleo-ocean pH, and paleo-redox conditions in oceans are highlighted respectively; various measurement techniques and their advantages/disadvantages are presented, including chemical extractions of elements and their isotope measurements using a Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). Finally, this article highlights the caveats and limitations, challenges, and scopes for future research of the stable isotopes.

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Carbonate uranium isotopes record global expansion of marine anoxia during the Toarcian Oceanic Anoxic Event

Published 22 July 2024 Science Closed
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Significance

A significant negative δ238U excursion (~0.4‰) starting just prior to the onset of the negative carbon isotope excursion within the Toarcian Oceanic Anoxic Event (T-OAE) has been recorded, followed by a long-lived recovery of δ238U values. This excursion represents a global expansion of marine anoxia of ~6 to 8% of the global seafloor during the peak of the T-OAE, which represents 28 to 38 times the extent of anoxia in the modern ocean. When compared with estimates of seafloor anoxic area for other CO2-driven global anoxic events, the T-OAE was the second-largest anoxic event of at least the last 300 My. As such, the T-OAE represents a powerful analog for future anthropogenic ocean deoxygenation.

Abstract

The Toarcian Oceanic Anoxic Event (T-OAE; ~183 Mya) was a globally significant carbon-cycle perturbation linked to widespread deposition of organic-rich sediments, massive volcanic CO2 release, marine faunal extinction, sea-level rise, a crisis in carbonate production related to ocean acidification, and elevated seawater temperatures. Despite recognition of the T-OAE as a potential analog for future ocean deoxygenation, current knowledge on the severity of global ocean anoxia is limited largely to studies of the trace element and isotopic composition of black shales, which are commonly affected by local processes. Here, we present the first carbonate-based uranium isotope (δ238U) record of the T-OAE from open marine platform limestones of the southeastern Tethys Ocean as a proxy for global seawater redox conditions. A significant negative δ238U excursion (~0.4‰) is recorded just prior to the onset of the negative carbon isotope excursion comprised within the T-OAE, followed by a long-lived recovery of δ238U values, thus confirming that the T-OAE represents a global expansion of marine anoxia. Using a Bayesian inverse isotopic mass balance model, we estimate that anoxic waters covered ~6 to 8% of the global seafloor during the peak of the T-OAE, which represents 28 to 38 times the extent of anoxia in the modern ocean. These data, combined with δ238U-based estimates of seafloor anoxic area for other CO2-driven Phanerozoic OAEs, suggest a common response of ocean anoxia to carbon release, thus improving prediction of future anthropogenically induced ocean deoxygenation.

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Toward an ecologically realistic experimental system to investigate the multigenerational effects of ocean warming and acidification on benthic invertebrates

Published 19 July 2024 Science Closed
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Human activities over the past 150 yr have led to significant carbon dioxide (CO2) emissions, causing global warming and ocean acidification. Surface ocean temperature has risen by 0.93°C since 1850, with projections of an additional +1.42°C to 3.47°C by 2080–2099. Ocean acidification, driven by CO2 absorption, has already lowered seawater pH by 0.1 units, affecting calcifying organisms, including shelled mollusks. Long-term multigenerational studies on mollusk responses to both ocean acidification and warming, under realistic environmental conditions, are scarce. To address this knowledge gap, two mobile experimental units that can be deployed at the vicinity of shellfish farming areas were developed within the framework of the CocoriCO2 project. The experimental systems were designed to manipulate temperature and pH as offsets from ambient conditions. The experimental units have shown their effectiveness in terms of controlling and maintaining pH and temperature to assess the multigenerational effects of ocean warming and acidification on benthic invertebrates. Finally, the developed experimental systems can be modified easily to provide an educated assessment of the impact of other relevant environmental changes such as deoxygenation and changes in salinity.

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Underway mapping of coastal seawater pH using an automated shipboard analyzer with spectrophotometric detection

Published 17 July 2024 Science Closed
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Highlights

  • High-precision spectrophotometric determination of pH.
  • Robust automated field-deployable analyzer for mapping pH.
  • Accurate pH measurement of dynamic estuarine-coastal samples.
  • A powerful monitoring tool for addressing ocean acidification and facilitating marine carbon dioxide removal.

Abstract

The development of field-deployable methods and instruments for the measurement of pH and other carbonate parameters is important for the assessment of the marine carbon cycle, ocean acidification and marine carbon dioxide removal techniques. In this study, a high-precision fully automated integrated syringe-pump-based environmental-water analyzer for pH (iSEA-pH) was developed. The pH is determined spectrophotometrically using purified indicator dye with a high precision (better than ±0.001) and high frequency (3.5 min/sample). For the short-term analysis, the measurement frequency was 18 h−1, which revealed pH = 7.8148 ± 0.0005 (n = 104) for aged surface seawater (S = 35) from the western Pacific. For long-term analysis, the measurement frequency was 2 h−1 for 4 days, and the results showed that pH = 7.8148 ± 0.0010 (n = 200). Three commonly used pH indicators (meta-cresol purple, thymol blue and phenol red) were purified with improved flash chromatography procedures. The autonomous iSEA-pH can automatically correct for the influence of temperature, salinity and other factors on pH measurements to achieve rapid and accurate on-site measurements, which meet the “climate” goal of the Global Ocean Acidification Observing Network (uncertainty is ±0.003). Three identical iSEA-pH systems were developed and successfully applied in mesocosm experiments and several coastal and open ocean cruises with excellent in field performance.

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“Quantifying the Impacts of Multiple Stressors” (QIMS)—a new experimental platform for robust multifactorial experiments in benthic ecosystems

Published 16 July 2024 Science Closed
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To predict the ecological consequences of expected global change, we need to understand the independent and combined effects of multiple stressors. Multiple experimental treatments are required to simultaneously test for effects of multiple stressors at different levels of intensity, independently and combined, and at different levels of biological organization. Most marine multiple stressors studies to date are conducted on assembled communities in mesocosms with a low number of treatments or low replication of treatments or both. These limitations prevent (1) robust data analyses, (2) characterization of single and combined effects of multiple stressors, and (3) identification of mechanisms underpinning biological responses. We present a new mesocosm-based experimental platform for benthic communities: Quantifying the Impacts of Multiple Stressors (QIMS). Here, 96 independent mesocosms facilitate multifactorial and multilevel experimental designs with the high replication required for robust tests of multiple stressors and biological interactions. For example, three distinct pH levels are achieved by manipulating CO2 concentrations in the air supply, and three water temperature levels are provided by a cooling system in a fully crossed design that is required to identify all potential interactions, from which all combinations can be replicated 10 times (i.e., 90 experimental units). We demonstrate clearly how different levels of temperature and pCO2/pH can be manipulated precisely and maintained for at least 7 weeks. QIMS complements the limited number of permanently installed marine mesocosm facilities worldwide that simulate ocean warming and/or acidification and expedites multiple stressor research by providing an unprecedented level of replication for statistical robustness.

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Nutrient limitation dampens the response of a harmful algae to a marine heatwave in an upwelling system

Published 15 July 2024 Science Closed
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Harmful algal blooms caused by toxin-producing species of the diatom genus Pseudo-nitzschia have been linked to anomalously warm ocean conditions in the Northern California Current System. This study compares summertime concentrations of Pseudo-nitzschia spp. and the toxin they produce, domoic acid, during a marine heatwave year (2019) and a climatologically neutral year (2021). An Imaging FlowCytobot was installed on a fishery survey vessel alongside environmental sensors to continuously sample phytoplankton and oceanographic parameters. This was paired with targeted manual sample collections for nutrients, chlorophyll, and domoic acid. Accumulations of Pseudo-nitzschia spp. were associated with upwelling zones and established hotspot regions: the Juan de Fuca Eddy, Heceta Bank, and Trinidad Head. Overall, however, Pseudo-nitzschia spp. and domoic acid concentrations were low during both summers and appear to have been limited by nitrate. Nutrient availability may therefore modulate the response of Pseudo-nitzschia spp. to warm anomalies. Comparison of these results with 2015, another marine heatwave year but one that produced record concentrations of Pseudo-nitzschia spp. and domoic acid, suggests that the timing of marine heatwave conditions in the nearshore relative to seasonal upwelling plays a key role in determining whether a Pseudo-nitzschia spp. harmful algal bloom will occur.

Continue reading ‘Nutrient limitation dampens the response of a harmful algae to a marine heatwave in an upwelling system’

Drivers of seasonal to decadal mixed layer carbon cycle variability in subantarctic water in the Munida Time Series

Published 10 July 2024 Science Closed
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Using ancillary datasets and interpolation schemes, 20+ years of the Munida Time Series (MTS) observations were used to evaluate the seasonal to decadal variability in the regional carbon cycle off the southeast coast of New Zealand. The contributions of gas exchange, surface freshwater flux, physical transport processes and biological productivity to mixed layer carbon were diagnostically assessed using a mass-balanced surface ocean model. The seasonal and interannual variability in this region is dominated by horizontal advection of water with higher dissolved inorganic carbon (DIC) concentration primarily transported by the Southland Current, a unique feature in this western boundary current system. The large advection term is primarily balanced by net community production and calcium carbonate production, maintaining a net sink for atmospheric CO2 with a mean flux of 0.84±0.62 mol C m-2 y-1. However, surface layer pCO2 shows significant decadal variability, with the growth rate of 0.53±0.26 μatm yr-1 during 1998–2010 increasing to 2.24±0.47 μatm yr-1 during 2010–2019, driven by changes in advection and heat content. Changes in circulation have resulted in the regional sink for anthropogenic CO2 being 50% higher and pH 0.011±.003 higher than if there had been no long-term changes in circulation. Detrended cross-correlation analysis was used to evaluate correlations between the Southern Annular Mode, the Southern Oscillation Index and various regional DIC properties and physical oceanographic processes over frequencies corresponding the duration of the MTS. The drivers of variability in the regional carbon cycle and acidification rate indicate sensitivity of the region to climate change and associated impacts on the Southern Ocean and South Pacific.

Continue reading ‘Drivers of seasonal to decadal mixed layer carbon cycle variability in subantarctic water in the Munida Time Series’

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