A quantification of carbon fluxes in the coastal ocean and across its boundaries with the atmosphere, land, and the open ocean is important for assessing the current state and projecting future ...trends in ocean carbon uptake and coastal ocean acidification, but this is currently a missing component of global carbon budgeting. This synthesis reviews recent progress in characterizing these carbon fluxes for the North American coastal ocean. Several observing networks and high-resolution regional models are now available. Recent efforts have focused primarily on quantifying the net air–sea exchange of carbon dioxide (CO2). Some studies have estimated other key fluxes, such as the exchange of organic and inorganic carbon between shelves and the open ocean. Available estimates of air–sea CO2 flux, informed by more than a decade of observations, indicate that the North American Exclusive Economic Zone (EEZ) acts as a sink of 160±80 Tg C yr−1, although this flux is not well constrained. The Arctic and sub-Arctic, mid-latitude Atlantic, and mid-latitude Pacific portions of the EEZ account for 104, 62, and −3.7 Tg C yr−1, respectively, while making up 51 %, 25 %, and 24 % of the total area, respectively. Combining the net uptake of 160±80 Tg C yr−1 with an estimated carbon input from land of 106±30 Tg C yr−1 minus an estimated burial of 65±55 Tg C yr−1 and an estimated accumulation of dissolved carbon in EEZ waters of 50±25 Tg C yr−1 implies a carbon export of 151±105 Tg C yr−1 to the open ocean. The increasing concentration of inorganic carbon in coastal and open-ocean waters leads to ocean acidification. As a result, conditions favoring the dissolution of calcium carbonate occur regularly in subsurface coastal waters in the Arctic, which are naturally prone to low pH, and the North Pacific, where upwelling of deep, carbon-rich waters has intensified. Expanded monitoring and extension of existing model capabilities are required to provide more reliable coastal carbon budgets, projections of future states of the coastal ocean, and quantification of anthropogenic carbon contributions.
•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.
A successful integrated ocean acidification (OA) observing network must include 1) scientists and technicians from a range of disciplines (from physics to chemistry to biology to technology ...development) and across the globe; 2) government, private, and intergovernmental support; 3) regional cohorts working together on regionally specific issues; 4) publicly accessible data from the open ocean to coastal to estuarine systems; 5) close integration with other networks focusing on related measurements or issues including the social and economic consequences of OA; and 6) observation-based informational products useful for decision making such as management of fisheries and aquaculture. The Global Ocean Acidification Observing Network (GOA-ON), a key player in this vision, seeks to expand and enhance geographic extent and availability of coastal and open ocean observing data to ultimately inform adaptive measures and policy action, especially in support of the United Nations 2030 Agenda for Sustainable Development. GOA-ON works to empower and support regional collaborative networks such as the Latin American Ocean Acidification Network, supports new scientists entering the field with training, mentorship, and equipment, refines approaches for tracking biological impacts, and stimulates development of lower-cost methodology and technologies allowing for wider participation of scientists. GOA-ON seeks to collaborate with and complement work done by other observing networks such as those focused on carbon flux into the ocean, tracking of carbon and oxygen in the ocean, observing biological diversity, and determining short- and long-term variability in these and other ocean parameters through space and time.
Porites panamensis is a hermatypic coral present in the eastern Pacific Ocean. Skeletal growth parameters have been reported, but studies of the relationship between annual calcification rates and ...environmental controls are scarce. In this study, we investigated three aspects of the annual calcification rates of P. panamensis: growth parameters among three P. panamensis populations; the sea surface temperature as a calcification rate control spanning a latitudinal gradient; and calcium carbonate production among three sites. Growth parameters varied among the sites due to the colony growth form. Massive colonies in the north showed a higher calcification rate than encrusting colonies in the south (mean: 1.22–0.49 g CaCO₃ · cm⁻² · yr⁻¹), where variations in calcification rates were related to growth rate (0.91–0.38 cm · yr⁻¹) rather than to skeletal density differences (overall mean ± SD, 1.31 ± 0.04 g CaCO₃ · cm⁻³). Our results showed a positive linear relationship between annual calcification rates and sea surface temperatures within these P. panamensis populations. Differences were related to distinct oceanographic environments (within and at the entrance of the Gulf of California) with different sea surface temperature regimes and other chemical properties. Different populations calcified under different environmental conditions. Calcium carbonate production was dependent upon the calcification rate and coral cover and so carbonate production was higher in the north (coral cover 12%) than in the south (coral cover 3.5). Thus, the studied sites showed low calcium carbonate production (0.25–0.43 kg CaCO₃ · m⁻² · yr⁻¹). Our results showed reduced calcification rates, regional temperature regime control over calcification rates, different growth forms, low coral cover and low calcium carbonate production rates in P. panamensis.
The Gulf of California (GC) features many oceanographic processes. It communicates with the Pacific Ocean via a surface water outflow (0-200 m) with relatively low dissolved inorganic carbon (DIC) ...values and a water inflow (200-600 m) with high DIC values. Data on the marine carbon system in the GC are scarce and most have been taken from the Midriff Islands region, in the central part of the gulf. We explored possible forcing agents that control the ocean-atmosphere CO2 flux (fCO2) variability in 5 coastal zones of the GC. We carried out 6 oceanographic cruises in 5 regions: off northern Sinaloa in September 2016 (NAV2016) and in March 2017 (NAV2017), in the Guaymas Basin (central gulf) in September 2016 (GUA2016), in Concepción Bay (Baja California Sur) in July 2017 (BC2017), in Mulegé (Baja California Sur) in July 2017 (MUL2017), and off Mazatlán (southern gulf) in July 2017 (MAZ2017). We measured temperature, salinity, DIC, and total alkalinity and calculated the surface water partial pressure of CO2 and fCO2. We also used sea surface height anomaly with geostrophic flow, sea surface temperature, and chlorophyll concentration data from satellite imagery to generate composites for the sampling days. The lowest temperature, highest DIC, and negative fCO2 were registered in NAV2017. NAV2016, GUA2016, and BC2017 showed the highest temperatures; and MUL2017 and MAZ2017, intermediate temperatures. The most contrasting fCO2 values occurred in GUA2017 (0.56 ± 0.46 mmol C·m-2·d-1) and MAZ2017 (-2.26 ± 1.85 mmol C·m-2·d-1). In general, fCO2 is determined by the oceanographic conditions of each study area.
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.
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 environmental changes due to the Colorado River damming, have affected the ecological functioning of the nursery river delta and consequently the population of fishermen that live of the natural ...marine resources of the upper Gulf of California. We propose the use of urban wastewaters as a source of nutrients to fertilize the estuary, increase the primary productivity and therefore increase the population size of the estuarine dependent species, which are important for the fisheries in the region. In this way, we could partially restore the delta's ecological functioning and thus solve environmental, social, and economic problems. With a wastewater flow of 800 l·s-1 from “Las Arenitas” treatment plant, we could increase the primary organic productivity and ~1000 metric tons (mT) of shrimp landings of the region. These calculations are just for one fishery, but in a magnitude that could also increase in others.
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