Open ocean observations have shown that increasing levels of anthropogenically-derived atmospheric CO2 are causing acidification of the worldâs oceans. Yet little is known about coastal acidification and studies are just beginning to characterize the carbonate chemistry of shallow, nearshore zones where many ecologically and economically important organisms occur. We characterized the carbonate chemistry of seawater within an area dominated by seagrass beds (Saint Joseph Bay, Florida), to determine the extent of variation in pH and pCO2 over monthly and daily timescales. Distinct diel and seasonal fluctuations were observed at daily and monthly timescales respectively, indicating the influence of photosynthetic and respiratory processes on the local carbonate chemistry. Over the course of a year, the range in monthly values of pH (7.36 â 8.28), aragonite saturation state (0.65 to 5.63), and calculated pCO2 (195 â 2537 uatm) were significant. When sampled on a daily basis the range in pH (7.70 â 8.06), aragonite saturation state (1.86 – 3.85), and calculated pCO2 (379 â 1019 uatm) also exhibited significant range and indicated variation between timescales. The results of this study have significant implications for the design of ocean acidification experiments where nearshore species are utilized and indicate that coastal species are experiencing far greater fluctuations in carbonate chemistry than previously thought.
Challener R., Robbins L. & McClintock J., in press. Variability of the carbonate chemistry in a shallow, seagrass-dominated ecosystem: implications for ocean acidification experiments. Marine & Freshwater Research. Article (subscription required).