68. The State of Ocean Acidification in a Newfoundland Fjord

Wartman, Melissa (1)*, Azetsu-Scott, Kumiko (2), Childs, Darlene (2), Hooper, Robert (3)

1 School of Biological Sciences, Monash University, Clayton, Victoria, 3800, Australia

2 Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada

3 Biology Department, Memorial University of Newfoundland, St John’s, Newfoundland, Canada

Background
Ocean acidification is a global phenomenon that exerts threats to vital coastal ecosystems. The state of ocean acidification in a pristine fjord was investigated by assessing the calcium carbonate saturation state with respect to calcite (Ωcal) and aragonite (Ωarg) and pHtotal in Bonne Bay, Newfoundland. Bonne Bay is comprised of two distinct basin (East and South Arm) connected to the Gulf of St. Lawrence (GSL).

Methods

CTD casts were completed in both basins and water samples were collected and analyzed for dissolved inorganic carbon (DIC), total alkalinity (TA), and pH, from April 28, 2012 to May 04, 2012.

Findings

Estuarine circulation was observed in Bonne Bay, with a fresher surface (<5m) layer overlying saline oceanic waters. Two distinct water masses were observed at depth in Bonne Bay: East Arm bottom waters (T= 0.10 to 0.75oC, S=31.0-31.5 psu) and South Arm bottom waters (T= 0.75 to 1.25oC, S= 31.7-32.4 psu). The average pHtotal in Bonne Bay was 8.031 ± 0.079, with the lowest pH (7.013) observed in the surface waters in both basins near freshwater input from local rivers and brooks. The average Ωarg in Bonne Bay was 1.16 ± 0.33 in the East Arm with a saturation horizon (where Ωarg =1) at 125m. In contrast, the average Ωarg in the South Arm was 1.37 ± 0.19 with no area of under saturation was observed.

Conclusions
Temporarily, more frequent flushing of the East Arm bottoms waters could increase the pH, Ωarg, and Ωcal, creating a more suitable habitat for calcifying organisms. However, as the outside waters in the Gulf of St. Lawrence become more acidic due to ocean acidification, these waters that flush the fjord bottom waters will soon be more acidic than the waters they would replace. This is the first study to investigate the chemical properties in Bonne Bay and provides baseline data of the saturation states and pH for the waters.