EFFECTS OF NEARSHORE PROCESSES ON CARBONATE CHEMISTRY DYNAMICS AND OCEAN ACIDIFICATION
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...
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University of New Hampshire Scholars' Repository
2020
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| Online Access: | https://scholars.unh.edu/dissertation/2532 https://scholars.unh.edu/cgi/viewcontent.cgi?article=3531&context=dissertation |
| Summary: | 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. This dissertation synthesizes autonomous and bottle observations to model carbonate chemistry and to understand how physical and biological processes affect seasonal carbonate chemistry at both locations. The autonomous carbonate chemistry and oxygen observations are used to examine a mass balance approach using a 1-D model to determine net rates of ecosystem calcification and production (NEC and NEP) from communities close (<5km) to the buoys. The results provide evidence to suggest that seasonal response between benthic metabolism and seawater chemistry at LP is attenuated relative to that at CR because their differences in benthic cover and how benthic metabolism modifies the water chemistry. Simple linear trends cannot explain the feedback between metabolism and reef water chemistry using long-term observations over natural variations. The effects of community production on partial pressure of CO2 (pCO2sw) make these interactions complex at short- and long-term scales. Careful consideration should be taken when inferring local biogeochemical processes, given that pCO2sw (and presumably pH) respond on much shorter time and local scales than dissolved inorganic carbon (DIC) and total alkalinity (TA). The observations highlight the need for more comprehensive observing systems that can reliably measure both the fast-response (pCO2sw, pH) and slow-response (DIC) carbon pools. The metabolism rates are shown to be robustly modeled using a mass balance ... |
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