Estimating the contribution of organic bases from microalgae to the titration alkalinity in coastal seawaters

Abstract

This study reports the potential contribution of organic bases to the alkalinity of seawater samples. The concentration of organic bases in these samples was inferred from the difference between the measured alkalinity and that calculated from a knowledge of pH and concentrations of the various inorganic acid‐bases species such as total carbon, total boron, and so on. Significant concentrations of such organic bases were measured in cultures of the marine microalgae Rhodomonas sp. (800 µmol kg−1) and Isochrysis aff. Galbana (400 µmol kg−1), as well as in three marine environments (northern gulf of California, México; San Quintín Bay, B.C., Mexico; and San Diego Bay). These three sites are characterized by significant biological activity and restricted mixing, and the organic bases were found at concentrations greater than 50 µmol kg−1 in each of these three locations.

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

“…Remineralization of particulate organic matter and subsequent nutrient release directly affect A T , depending on the reactive nitrogen species produced (e.g. 1 mole of ammonium or nitrate release leads to an increase or decrease, respectively, of A T by 1 mole; Hernández-Ayón et al, 2007). During more acidified conditions, in this study, the steady increase of ammonium over time along with the respective decrease in nitrate and nitrite concentrations could contribute positively to A T levels.…”

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

“…Fraser River TA thus appears to be produced primarily by carbonate weathering in the upper watershed, diluted by low-TA seaward tributaries, and flow-dependent. There are no data in the Fraser River region to date that determine organic acids and bases that may contribute significantly to TA, as they do in some coastal areas (Cai et al, 1998;Koeve and Oschlies, 2012;Kim and Lee, 2009;Hernández-Ayón et al, 2007) and rivers (Hunt et al, 2011;Kennedy, 1965). Carbonate alkalinity is esti- mated to be as low as 10 % of TA in the Congo (Wang et al, 2013) and Kennebec rivers (Hunt et al, 2014).…”

Significant contribution of dissolved organic matter to seawater alkalinity

“…The strong correlation between DA T and DDOC indicates that the net production of DOM (measured here as DDOC) by phytoplankton during photosynthesis contributed to seawater A T , i.e., DA T-DOM . A similar method of quantifying DA T-DOM in culture samples was employed elsewhere [Hernandez-Ayon et al, 2007;Muller and Bleie, 2008], but in their study a direct connection between increasing A T anomalies and DOC accumulation was not established. In addition, their pH measurements may have been inaccurate because potentiometric pH measurements are subject to large errors, particularly in high pH seawater (>8.0) [Dickson, 1993].…”

“…However, the model does not take into account DOM, which could lead to errors in A T values estimated from titration data. The contribution of DOM to seawater A T (A T-DOM ) has been partially demonstrated in previous studies [Cai et al, 1998;Hernandez-Ayon et al, 2007;Muller and Bleie, 2008], but the supporting evidence was inconclusive.…”

“…Of biochemical products released in phytoplankton cultures, some weak organic acids (e.g., glycollate and tricarboxylic acids) may contribute to A T-MEAS [Hernandez-Ayon et al, 2007;Muller and Bleie, 2008]. In future studies, the molecular level analysis of DOM will facilitate identification of functional groups that are responsible for species-specific relationships between DA T and DDOC.…”