Seasonal Variations of Carbonate Chemistry at Two Western Atlantic Coral Reefs

Abstract

Time series from open ocean fixed stations have robustly documented secular changes in carbonate chemistry and long‐term ocean acidification (OA) trends as a direct response to increases in atmospheric carbon dioxide (CO2). However, few high‐frequency coastal carbon time series are available in reef systems, where most affected tropical marine organisms reside. Seasonal variations in carbonate chemistry at Cheeca Rocks (CR), Florida, and La Parguera (LP), Puerto Rico, are presented based on 8 and 10 years of continuous, high‐quality measurements, respectively. We synthesized and modeled carbonate chemistry to understand how physical and biological processes affect seasonal carbonate chemistry at both locations. The results showed that differences in biology and thermodynamic cycles between the two systems caused higher amplitudes at CR despite the shorter residence times relative to LP. Analyses based on oxygen and temperature‐normalized pCO2sw showed that temperature effects on pCO2sw at CR were largely counteracted by primary productivity, while thermodynamics alone explained a majority of the pCO2sw dynamics at LP. Heterotrophy dominated from late spring to fall, and autotrophy dominated from winter to early spring. Observations suggested that organic respiration decreased the carbonate mineral saturation state (Ω) during late summer/fall. The interactive effects between the inorganic and organic carbon cycles and the assumed effects of benthic metabolism on the water chemistry at both sites appeared to cause seasonal hysteresis with the carbonate chemistry. Improved integration of observational data to modeling approaches will help better forecast how physical and biogeochemical processes will affect Ω and carbonate chemistry in coastal areas.

Net ecosystem dissolution and respiration dominate metabolic rates at two western Atlantic reef sites

“…Rhizophora mangle and Laguncularia racemosa mangroves have colonized the Enrique reef crest. The inorganic nutrient concentrations across the Caribbean and La Parguera coral reefs are low (Meléndez et al 2020). Riverine influence is at its minimum during the winter and spring, while the Amazon and Orinoco plumes dominate the southeastern Caribbean during the summer and fall (Corredor and Morell, 2001).…”

Heritable variation and lack of tradeoffs suggest adaptive capacity inAcropora cervicornisdespite negative synergism under climate change scenarios

“…[14,15], and increasing water temperatures, which have led to regional bleaching events [16,17]. FCR also experiences a combination of ocean and coastal acidification processes [18][19][20], which can impair coral growth and skeletal integrity [21][22][23][24][25]. Ocean acidification is the global decrease in oceanic pH as a result of the exponential increase of atmospheric carbon dioxide since the Industrial Revolution, which in turn leads to increases in dissolved CO 2 within the oceans [26,27].…”

Experimental Techniques to Assess Coral Physiology in situ Under Global and Local Stressors: Current Approaches and Novel Insights

“…Indeed, autonomous measurements of light, dissolved oxygen, and alkalinity were used to estimate the NCP and NCC in order to evaluate the efficacy of coral restoration in supporting the net ecosystem metabolism ( Platz et al, 2020 ). Autonomous sensors can be used also to measure the seasonal variability in carbonate chemistry and the relationship between carbonate chemistry and biological activity of benthic organisms identifying spatial differences according to different substrates, like corals, seagrasses, or mangroves ( Meléndez et al, 2020 ). These systems are especially important in natural ocean acidification laboratories, such as hydrothermal vents, characterized by naturally high fluctuations of pH and temperature ( Kerrison et al, 2011 ; Fabricius et al, 2015 ; Torres et al, 2021 ).…”