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Abstract The southeastern Atlantic Ocean is a crucial yet understudied region for the ocean absorption of anthropogenic carbon (Canth). Data from the A12 (2020) and A13.5 (2010) cruises offer an opportunity to examine changes in dissolved inorganic carbon (DIC), its stable isotope (δ13C), and Canthover the past decade within a limited region (1∼3°E, 32∼42°S). For the decade of 2010–2020, Canthinvasion was observed from the sea surface down to 1,200 m based on both DIC and δ13C data. The mean Canthincrease rate (1.08 ± 0.26 mol m−2 yr−1) during this period accelerated from 0.87 ± 0.05 mol m−2 yr−1during the previous period (1983/84–2010). The δ13C‐based Canthincrease closely matches the DIC‐based estimation below 500 m but is 26% higher in the upper ocean. This discrepancy is likely due to δ13C's longer air‐sea exchange timescale, seasonal variability in the upper ocean, and the chosen ratio of anthropogenically induced changes in δ13C and DIC. Finally, column inventory changes based on the two methods also exhibit very similar mean Canthuptake rates. The paired DIC concentration and stable isotope dataset may enhance our ability to constrain Canthaccumulation and its controlling mechanisms in the ocean.
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This content will become publicly available on April 1, 2027
Monitoring Coral Reef Metabolism Under Changing Oceans–Novel Insights From Seawater Stable Carbon Isotopes
Abstract Mounting environmental stressors are driving Caribbean reefs from coral to sponge and macroalgae dominance, necessitating a need for more nuanced metrics of reef metabolism under trophic transitions. Drawing upon four seasonally replicated field campaigns to Curaçao, we reveal highly variable net ecosystem productivity (−243 ± 69 C m−2 day−1to 216 ± 36 mmol C m−2 day−1) and calcification (−143 ± 42 mmol CaCO3m−2 day−1to 140 ± 21 mmol CaCO3m−2 day−1). We observe periods of intense net ecosystem dissolution that fall significantly below previously reported global averages. We offer two additional metabolic insights by integrating measurements of the stable carbon isotope composition of dissolved inorganic carbon (δ13CDIC). First, Keeling plots of water column DIC and δ13CDICmeasurements suggest that zooplankton grazing may be a significant source of respired carbon to the reef ecosystem, even during periods of net autotrophy. This suggests that heterotrophic feeding by corals or other consumers is a primary energy pathway that may provide the mixotrophic coral community with a stable food source and bolster its resilience to periods of symbiont stress. Second, by isolating photosynthetic fractionation factors, we reveal a potential carbonate chemistry dependence on algal community photosynthetic plasticity. This provides an important fingerprint of how the dominant primary producers physiologically respond to changing ocean conditions, which is essential for forecasting future shifts in the community and its metabolic function. These findings suggest that integrating stable isotopes into reef biogeochemical toolkits offers unprecedented insights into community interactions in a changing ocean.
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- PAR ID:
- 10686993
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 131
- Issue:
- 4
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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