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.
•The first full annual record of CO2 by MAPCO2 in the South Atlantic Bight.•Time series CO2 controls were quantitatively identified using a 1-D model.•River-influenced coastal system was vulnerable ...to terrestrial inputs.•River inputs can induce CO2 interannual variability.•Temporal under-sampling can greatly bias estimates of air–sea CO2 flux and NCP.
Carbon dioxide partial pressure (pCO2) in surface seawater was continuously recorded every three hours from 18 July 2006 through 31 October 2007 using a moored autonomous pCO2 (MAPCO2) system deployed on the Gray’s Reef buoy off the coast of Georgia, USA. Surface water pCO2 (average 373±52μatm) showed a clear seasonal pattern, undersaturated with respect to the atmosphere in cold months and generally oversaturated in warm months. High temporal resolution observations revealed important events not captured in previous ship-based observations, such as sporadically occurring biological CO2 uptake during April–June 2007. In addition to a qualitative analysis of the primary drivers of pCO2 variability based on property regressions, we quantified contributions of temperature, air–sea exchange, mixing, and biological processes to monthly pCO2 variations using a 1-D mass budget model. Although temperature played a dominant role in the annual cycle of pCO2, river inputs especially in the wet season, biological respiration in peak summer, and biological production during April–June 2007 also substantially influenced seawater pCO2. Furthermore, sea surface pCO2 was higher in September–October 2007 than in September–October 2006, associated with increased river inputs in fall 2007. On an annual basis this site was a moderate atmospheric CO2 sink, and was autotrophic as revealed by monthly mean net community production (NCP) in the mixed layer. If the sporadic short productive events during April–May 2007 were missed by the sampling schedule, one would conclude erroneously that the site is heterotrophic. While previous ship-based pCO2 data collected around this buoy site agreed with the buoy CO2 data on seasonal scales, high resolution buoy observations revealed that the cruise-based surveys undersampled temporal variability in coastal waters, which could greatly bias the estimates of air–sea CO2 fluxes or annual NCP, and even produce contradictory results.
In coastal regions and marginal bodies of water, the increase in partial pressure of carbon dioxide (
p
CO
2
) in many instances is greater than that of the open ocean due to terrestrial (river, ...estuarine, and wetland) influences, decreasing buffering capacity and/or increasing water temperatures. Coastal oceans receive freshwater from rivers and groundwater as well as terrestrial-derived organic matter, both of which have a direct influence on coastal carbonate chemistry. The objective of this research is to determine if coastal marshes in Georgia, USA, may be “hot-spots” for acidification due to enhanced inorganic carbon sources and if there is terrestrial influence on offshore acidification in the South Atlantic Bight (SAB). The results of this study show that dissolved inorganic carbon (DIC) and total alkalinity (TA) are elevated in the marshes compared to predictions from conservative mixing of the freshwater and oceanic end-members, with accompanying pH around 7.2 to 7.6 within the marshes and aragonite saturation states (Ω
Ar
) <1. In the marshes, there is a strong relationship between the terrestrial/estuarine-derived organic and inorganic carbon and acidification. Comparisons of pH, TA, and DIC to terrestrial organic material markers, however, show that there is little influence of terrestrial-derived organic matter on shelf acidification during this period in 2014. In addition, Ω
Ar
increases rapidly offshore, especially in drier months (July). River stream flow during 2014 was anomalously low compared to climatological means; therefore, offshore influences from terrestrial carbon could also be decreased. The SAB shelf may not be strongly influenced by terrestrial inputs to acidification during drier than normal periods; conversely, shelf waters that are well-buffered against acidification may not play a significant role in mitigating acidification within the Georgia marshes.
Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation ENSO, Pacific Decadal ...Oscillation PDO, and North Atlantic Oscillation NAO) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity.
Coastal acidification in southeastern U.S. estuaries and coastal waters is influenced by biological activity, run-off from the land, and increasing carbon dioxide in the atmosphere. Acidification can ...negatively impact coastal resources such as shellfish, finfish, and coral reefs, and the communities that rely on them. Organismal responses for species located in the U.S. Southeast document large negative impacts of acidification, especially in larval stages. For example, the toxicity of pesticides increases under acidified conditions and the combination of acidification and low oxygen has profoundly negative influences on genes regulating oxygen consumption. In corals, the rate of calcification decreases with acidification and processes such as wound recovery, reproduction, and recruitment are negatively impacted. Minimizing the changes in global ocean chemistry will ultimately depend on the reduction of carbon dioxide emissions, but adaptation to these changes and mitigation of the local stressors that exacerbate global acidification can be addressed locally. The evolution of our knowledge of acidification, from basic understanding of the problem to the emergence of applied research and monitoring, has been facilitated by the development of regional Coastal Acidification Networks (CANs) across the United States. This synthesis is a product of the Southeast Coastal and Ocean Acidification Network (SOCAN). SOCAN was established to better understand acidification in the coastal waters of the U.S. Southeast and to foster communication among scientists, resource managers, businesses, and governments in the region. Here we review acidification issues in the U.S. Southeast, including the regional mechanisms of acidification and their potential impacts on biological resources and coastal communities. We recommend research and monitoring priorities and discuss the role SOCAN has in advancing acidification research and mitigation of and adaptation to these changes.
Quantifying and identifying measurement error is an ongoing challenge for carbon cycle science to constrain measurable uncertainty related to the sources and sinks of CO2. One source of uncertainty ...in measurements is derived from random errors ( epsilon ); thus, it is important to quantify their magnitude and their relationship to environmental variability in order to constrain local-to-global carbon budgets. We applied a paired-observation method to determine epsilon associated with marine xCO2 in a coastal upwelling zone of an eastern boundary current. Continuous data (3-h resolution) from a mooring platform during upwelling and non-upwelling seasons was analyzed off of northern Baja California in the California Current. To test the rigor of the algorithm to calculate epsilon we propose a method for determining daily mean time series values that may be affected by epsilon . To do this we used either two or three variables in the function, but no significant differences for epsilon mean values were found due to the large variability in epsilon (-0.088 plus or minus 27ppm for two variables and -0.057 plus or minus 28ppm for three variables). Mean epsilon values were centered on zero, with low values of epsilon more frequent than greater values, and follow a double exponential distribution. Random error variability increased with higher magnitudes of xCO2, and in general, epsilon variability increased in relation to upwelling conditions (up to 9% of measurements). Increased epsilon during upwelling suggests the importance of meso-scale processes on epsilon variability and could have a large influence seasonal to annual CO2 estimates. This approach could be extended and modified to other marine carbonate system variables as part of data quality assurance/quality control and to quantify uncertainty (due to epsilon ) from a wide variety of continuous oceanographic monitoring platforms.
Coastal margins could be hotspots for acidification due to terrestrial‐influenced CO2 sources. Currently there are no long‐term (>20 years) records from biologically important coastal environments ...that could demonstrate sea surface CO2 fugacity (fCO2) and pH trends. Here, multidecadal fCO2 trends are calculated from underway and moored time series observations along the United States southeast coastal margin, also referred to as the South Atlantic Bight (SAB). fCO2 trends across the SAB, derived from ∼26 years of cruises and ∼9.5 years from a moored time series, range from 3.0 to 4.5 µatm yr−1, and are greater than the open ocean increases. The pH decline related to the fCO2 increases could be as much as −0.004 yr−1; a rate greater than that expected from atmospheric‐influenced pH alone. We provide evidence that fCO2 increases and pH decreases on an ocean margin can be faster than those predicted for the open ocean from atmospheric influence alone. We conclude that a substantial fCO2 increase across the marginal SAB is due to both increasing temperature on the middle and outer shelves, but to lateral land‐ocean interactions in the coastal zone and on inner shelf.
Key Points
Long‐term fCO2 in coastal South Atlantic Bight is increasing at a rate greater than open ocean
The fCO2 increase is likely a combination of increases from terrestrial sources, with little to no influence from temperature
The related pH decrease on this coastal margin is likely greater than that of the open ocean
The uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has resulted in a decrease in seawater aragonite saturation state (Ωarag), which affects the health of carbonate‐bearing organisms ...and the marine ecosystem. A substantial short‐term variability of surface water Ωarag, with an increase of up to 0.32, was observed in the central Mid‐Atlantic Bight off the Delaware and the Chesapeake Bays over a short period of 10 days in summer 2015. High‐frequency underway measurements for temperature, salinity, percentage saturation of dissolved oxygen, oxygen to argon ratio, pH, fCO2, and measurements based on discrete samples for pH, dissolved inorganic carbon, and total alkalinity are used to investigate how physical and biogeochemical processes contribute to the changes of Ωarag. Quantitative analyses show that physical advection and mixing processes are the dominant forces for higher Ωarag in slope waters while biological carbon removal and CO2 degassing contribute to increased Ωarag in shelf waters.
Key Points
Large changes in surface water aragonite saturation state were observed off the Delaware and Chesapeake Bays over a short period of 10 days
Biological carbon removal and CO2 degassing largely affected the aragonite saturation state on the shelf
Physical processes were the dominant forces for large aragonite saturation state changes in the slope water
In the past several decades, the techniques used to discern the different sedimentary fractions of P have been refined. This has allowed for a better understanding of P burial of the different P ...fractions and diagenetic reactions and, ultimately, the constraining of P residence time in the oceans. P sequential extraction was performed on eight sediment cores (between 16 and 24 cm deep) collected along a salinity gradient from the Ojo de Liebre Lagoon and the salt evaporation saltern of Guerrero Negro, Baja California Sur, Mexico in order to determine, under purely diagenetic conditions (in the absence of anthropogenic activities and biogenic sediment reworking), the fractionation and flux of P to the sediments. The majority of P was found in the authigenic fraction (37±5.4% to 53±8.9%), with P associated to organic matter comprising the overall smallest percentage (0.25±0.43% to 21±6.0%) relative to total P. The average flux of total P to the sediments for all the sites was found to be (451±127) 10⁻⁴ mol m⁻² year⁻¹, up to several orders of magnitude greater than those found in other studies. It is concluded that P is most likely transformed from P associated to organic matter to the authigenic mineral phase and that P was retained in the sediments in its mineral form rather than in reactive forms. This particular study area has the ability to retain large quantities of P in the sediments.
Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. ...Monitored parameters include all, or some of the following: partial pressure of CO2 of the water (pCO2w) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray's Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of pCO2w from underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual pCO2w time series variability and air-sea flux (FCO2), as well as describe the potential sources of pCO2w variability; and determine the source/sink for atmospheric pCO2. Over the ~8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated-pCO2w strongly correlate with r-values > 0.90. pCO2w and FCO2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series pCO2w increases by 5.2 ± 1.4µatm y−1 with FCO2 increasing 51–70mmolm−2 y−1. The net FCO2 sign can switch interannually with the magnitude varying greatly. Non-thermal pCO2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term pCO2w increase.
•Mooring, underway, and discrete water samples CO2 is examined.•High interannual CO2 variability on ocean margins could be due to freshwater inputs.•Non-thermal processes likely contribute to increased CO2 on an ocean margin.
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