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Abstract There is limited information on how the nutrient and freshwater input affects water column carbonate chemistry in the estuaries along the northern Gulf of Mexico. In this study, we assess the seasonal and spatial variability in carbonate chemistry in the Barataria Basin, a eutrophic estuary adjacent to the mouth of the Mississippi River. Eleven stations were sampled along a salinity gradient during the winter (January), spring (April), summer (July), and fall (October) of 2021. Surface and bottom water samples were collected for the analyses of dissolved inorganic carbon (DIC); total alkalinity (TA); and nitrite plus nitrate (NO2 + NO3), phosphate (PO4), and dissolved silica (SiO4). Dissolved CO2(pCO2) was measured in the surface water. Seasonal surface DIC and TA values ranged from 1553 to 2582 μmol kg−1and 1217 to 2217 μmol kg−1, respectively. DIC and TA varied seasonally and showed an increasing trend from fresh stations to saline stations. The highest DIC and TA values were observed during the fall season, likely due to the increased contribution of DIC and TA from adjacent marshes as a result of enhanced porewater exchange. In contrast to DIC and TA, pCO2decreased with the increase of salinity. The seasonal and spatial patterns in carbonate chemistry could not be explained solely by physical mixing and reflected complex interactions between biogeochemical processes driven by nutrient supply and temperature as well as tidal flushing and material exchanges with adjacent marshes.
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Synoptic assessment of coastal total alkalinity through community science
Abstract Comprehensive sampling of the carbonate system in estuaries and coastal waters can be difficult and expensive because of the complex and heterogeneous nature of near-shore environments. We show that sample collection by community science programs is a viable strategy for expanding estuarine carbonate system monitoring and prioritizing regions for more targeted assessment. ‘Shell Day’ was a single-day regional water monitoring event coordinating coastal carbonate chemistry observations by 59 community science programs and seven research institutions in the northeastern United States, in which 410 total alkalinity (TA) samples from 86 stations were collected. Field replicates collected at both low and high tides had a mean standard deviation between replicates of 3.6 ± 0.3 µ mol kg −1 ( σ mean ± SE, n = 145) or 0.20 ± 0.02%. This level of precision demonstrates that with adequate protocols for sample collection, handling, storage, and analysis, community science programs are able to collect TA samples leading to high-quality analyses and data. Despite correlations between salinity, temperature, and TA observed at multiple spatial scales, empirical predictions of TA had relatively high root mean square error >48 µ mol kg −1 . Additionally, ten stations displayed tidal variability in TA that was not likely driven by low TA freshwater inputs. As such, TA cannot be predicted accurately from salinity using a single relationship across the northeastern US region, though predictions may be viable at more localized scales where consistent freshwater and seawater endmembers can be defined. There was a high degree of geographic heterogeneity in both mean and tidal variability in TA, and this single-day snapshot sampling identified three patterns driving variation in TA, with certain locations exhibiting increased risk of acidification. The success of Shell Day implies that similar community science based events could be conducted in other regions to not only expand understanding of the coastal carbonate system, but also provide a way to inventory monitoring assets, build partnerships with stakeholders, and expand education and outreach to a broader constituency.
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- PAR ID:
- 10318296
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 16
- Issue:
- 2
- ISSN:
- 1748-9326
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1748-9326/abcb39
