Syntheses of carbonate chemistry spatial patterns are important for predicting ocean acidification impacts, but are lacking in coastal oceans. Here, we show that along the North American Atlantic and ...Gulf coasts the meridional distributions of dissolved inorganic carbon (DIC) and carbonate mineral saturation state (Ω) are controlled by partial equilibrium with the atmosphere resulting in relatively low DIC and high Ω in warm southern waters and the opposite in cold northern waters. However, pH and the partial pressure of CO
(pCO
) do not exhibit a simple spatial pattern and are controlled by local physical and net biological processes which impede equilibrium with the atmosphere. Along the Pacific coast, upwelling brings subsurface waters with low Ω and pH to the surface where net biological production works to raise their values. Different temperature sensitivities of carbonate properties and different timescales of influencing processes lead to contrasting property distributions within and among margins.
Prolonged nitrogen (N) fertilization can impact seagrass survival and productivity; however, the effects of N enrichment pulses (e.g., upwelling or sediment resuspension) remain poorly understood. ...This study examined the effects of short-term (1 h) pulsing of nitrate (
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) enrichment, simulating an upwelling event, on dissolved inorganic carbon (DIC) and
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uptake capacities, critical in controlling eelgrass productivity. Zostera marina dominates submerged vegetation in coastal lagoons influenced by upwelling in the California Current system. Laboratory incubations were conducted in winter (non-upwelling) and spring (upwelling) with shoots collected from San Quintín Bay meadows, Baja California, Mexico, differentially exposed to upwelled
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. Results suggest that
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enrichment stimulated DIC and
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uptake in winter, reflecting the close relationship between carbon metabolism and
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assimilation. Eelgrass shoots showed reduced
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incorporation in spring; neither
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uptake nor photosynthesis increased when exposed to high
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. Saturation of spring shoots at lower ambient
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concentrations may be interpreted as a physiological strategy to restrict metabolically costly
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incorporation during upwelling; this regulation of
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uptake strongly contrasts to the apparently full exploitation of this nutrient by seaweeds also dominant within the bay, as indicated in previous works. Despite their reduced
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uptake, eelgrass meadows near the bay mouth acquire
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at rates up to 4.2 mmol N m⁻² day⁻¹. This represents nontrivial water column
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removal compared to the estimated oceanic
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supply (~ 7.1 mmol m⁻² day⁻¹) during upwelling, highlighting the importance of Z. marina beds in controlling the lagoonal N-budget.
El golfo de California (GC) presenta diversos procesos oceanográficos. Tiene comunicación con el océano Pacífico mediante un flujo de salida de agua superficial (0–200 m) con valores relativamente ...bajos de carbono inorgánico disuelto (CID) y un flujo de entrada de agua (200–600 m) con valores altos de CID. Los datos sobre el sistema de carbono marino en el GC son escasos, y la mayoría proviene de la región de las islas grandes, en el centro del golfo. Se exploraron los posibles agentes forzantes que controlan la variabilidad del flujo de CO2 océano-atmósfera (fCO2) en 5 zonas costeras del GC. Se realizaron 6 cruceros oceanográficos en 5 regiones: frente al norte de Sinaloa en septiembre de 2016 (NAV2016) y marzo de 2017 (NAV2017), en la cuenca de Guaymas (centro del golfo) en septiembre de 2016 (GUA2016), en bahía Concepción (Baja California Sur) en julio de 2017 (BC2017), en Mulegé (Baja California Sur) en julio de 2017 (MUL2017) y frente a Mazatlán (golfo sur) en julio de 2017 (MAZ2017). Se midió la temperatura y la salinidad, se estimó el CID y la alcalinidad total y se calculó la presión parcial de CO2 superficial y el fCO2. Se utilizaron imágenes de satélite para generar compuestos de la anomalía del nivel del mar con flujo geostrófico, la temperatura superficial del mar y la concentración de clorofila en los días de muestreo. La temperatura más baja, el CID más alto y el fCO2 negativo se registraron en NAV2017. NAV2016, GUA2016 y BC2017 registraron las temperaturas más altas, y MUL2017 y MAZ2017, temperaturas intermedias. Los mayores contrastes de fCO2 ocurrieron en GUA2017 (0.56 ± 0.46 mmol C· m–2·d–1) y MAZ2017 (–2.26 ± 1.85 mmol C· m–2·d–1). En general, el fCO2 está determinado por las condiciones oceanográficas de cada zona de estudio.
As a result of anthropogenic activities, it has been predicted that the ocean will be challenged with rising temperature, increased stratification, ocean acidification, stronger more frequent ...tropical storms, and oxygen depletion. In the tropical Pacific off central Mexico all these phenomena are already occurring naturally, providing a laboratory from which to explore ocean biogeochemical dynamics that are predicted under future anthropogenic forcing conditions. Here, seasonally anomalous surface tropical waters were detected as a result of the developing "Godzilla El Niño 2015-2016". The incursion of this oxygenated water modified the local structure of an intense and shallow oxygen minimum zone, partially eroding and intensifying the oxycline while having an associated impact on the carbon maximum zone. The core of the oxygen minimum zone (<4.4 μmol kg-1) was centered around 474 m, with a variant upper level between 50 and 360 m depth. Below the dominance of Tropical Surface Waters, the thickness of the oxycline varied between 10 and 325 m, with intensity values up to 11 μmol kg-1 m-1. The change in dissolved inorganic carbon and apparent oxygen utilization yielded a molar ratio of δDIC=0.98×δAOU during June 2015 and of δDIC=1.08×δAOU for March 2016. A further decrease in the average content of dissolved inorganic carbon was observed in the carbon maximum zone for 2016. Traditionally, different explanations have been proposed to account for changing oxygen concentrations in the ocean rather than considering the interactions between multiple forcing factors. Our results highlight the significance of an episodic event like El Niño in the distribution and concentration of O2 and dissolved inorganic carbon and as a plausible mechanism of ventilation and increased oxygen availability in the upper oxygen minimum zone of the tropical Pacific off central Mexico.
Oceanographic features acting on different spatial-temporal scales influence the variation in the partial pressure of CO2 (pCO2) and ocean-atmosphere CO2 flux (FCO2). In this work, we regionally ...characterize regions of variability in the Mexican Pacific (MP) based on these chemical properties. We also evaluate the seasonal and interannual changes of each region: in the California Current System (CCS), Cabo Corrientes (CC), and Gulf of Tehuantepec (GT) regions. Sea surface temperature (SST), salinity, wind, pCO2, and FCO2 data from 1993 to 2018 were analyzed. Bayesian t-tests (95% credibility intervals) determined showed that the three regions had high probabilities of being different. Typical FCO2 values in the CCS were higher (−27.6–29.8 mmol C m−2 d−1) than those of the CC and GT regions (−19.9–25.8 and − 11.8–12.5 mmol C m−2 d−1, respectively). The highest positive seasonal variation of FCO2 (mean ± standard deviation) was found in the CCS and CC (∼4.6 ± 4.2 mmol C m−2 d−1) regions during spring, and in the GT region (1.2 ± 2 mmol C m−2 d−1) in autumn due to the strong northerly winds. It was found that during ENSO conditions the MP was a source (4.0 and 3.9 mol C m−2 y−1 for El Niño and La Niña, respectively), although on average over the last 25 years included in the study the MP acted as a slight-CO2 sink (∼10.9 ± 0.005 mol C m−2).
•The Mexican Pacific can be regionalized based on pCO2 measurements•The highest variation of FCO2 was found in the CCS and CC regions during summer.•High FCO2 was also found in the GT region in autumn during the Tehuano season.•During the 25 years of the study, the MP was found a CO2 source to the atmosphere.
In the Gulf of Mexico (GoM), the upper 300 m of the water column contains a mixture of water types derived from water masses from the North Atlantic and the Caribbean Sea, namely Caribbean Surface ...Water (CSW), Subtropical Underwater (SUW), Gulf Common Water (GCW), and Tropical Atlantic Central Water (TACW). These are mainly altered by mesoscale processes and local evaporation, which modulate biogeochemical cycles. In this study, we improve our understanding of water mass dynamics by including biogeochemical data when evaluating the T-S relationship to define water-mass boundaries, particularly when the observed thermohaline characteristics overlap. The variables considered were apparent oxygen utilization (AOU), nitrate, and dissolved inorganic carbon (DIC). The data were obtained from eight cruises carried out in the central and southern regions of the GoM and an additional cruise that covered the entire coastal-ocean region. The new proposed boundaries were instrumental in clarifying the dynamics of surface waters. Of note, GCW on the western side of the GoM is not formed from the mixing of CSW and SUW but by the mixing of remnant CSW with TACW. In winter, a remnant of CSW mixed with GCW, and the biogeochemical composition of surface waters was affected, as observed from an increase in nitrate and DIC concentrations and positive AOU values. CSW was mainly detected at the surface during summer with negative AOU values, low DIC values, and almost undetectable nitrate concentrations. The presence or absence of CSW modulated the depth of the nitracline and likely influenced primary productivity.
•GCW is formed by the mixture of the CSW with TACW in the western region of gulf.•The presence or absence of CSW modulates the depth of the nitracline.•Water type boundaries improve by adding biogeochemical data to T-S relationships•The new reclassification improves our understanding of how GCW is formed.
The aim of this work was to identify processes that cause surface CO2 partial pressure (pCO2W) and air–water CO2 flux (FCO2) variations at a coastal location in the California Current System, from ...semidiurnal to interannual time scales. Such processes may include sea breeze, upwelling, El Niño/Southern Oscillation (ENSO) cycle, and “The Blob” (strong positive temperature anomalies in the NE Pacific). Sea surface temperature (SST, 2008–2014) and pCO2W (2008–2015) time series were generated with data collected from a MAPCO2 buoy anchored at 100 m depth and 5 km from Punta Banda (31.6ºN, 116.6ºW), Baja California, México. There were significant changes in SST, pCO2W, and FCO2 that lasted periods that were as short as a few hours and as large as interannual time frames. Spectral analysis showed significant semidiurnal, diurnal, ~15-d, and ~28-d components of variation. Time series were divided into periods according to the Multivariate ENSO Index and the Blob event. Bayesian t tests show that both pCO2W and FCO2 had high credibility of being different between periods. During La Niña conditions (2010–2011), maximum pCO2W and FCO2 values were higher, and the minimum values were lower, than during “normal,” El Niño, and Blob conditions. The pCO2W range during this La Niña event was from 131 to 864 µatm, and the FCO2 range was from–6.9 to 40.4 mmol C·m–2·d–1. The FCO2 range during the Blob was from near equilibrium to ~2.5 mmol C·m–2·d–1. The extreme values for the FCO2 integral (± standard error), for all periods, were –57.0 ± 0.01 mmol C·m–2 for El Niño, and 257.0 ± 0.03 mmol C·m–2 for La Niña. Themean FCO2 value (± standard error) was 0.04 ± 0.02 mol C·m–2·yr–1. The buoy location was found to be a very weak source of CO2 during thestudy period.
Abstract 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 CO 2 pressure (pCO 2 ), and aragonite saturation (Ω Ar ) 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 pCO 2 (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.
•The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion ...of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century.•This review paper provides a synthesis of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment.•Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions.•Case studies were selected to achieve a balance in system diversity and global coverage.•Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time.•Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration.•Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships.•Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging.•System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.
The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.
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