Macroalgae contribute to nested mosaics of pH variability in a sub-Arctic fjord

• Published in: Biogeosciences
• Main Authors: Krause-Jensen, Dorte, Duarte, Carlos M., Hendriks, Iris E., Meire, L., Blicher, M. E., Marbà, Núria, Sejr, Mikael K.
• Other Authors: Danish Cooperation for Environment in the Arctic, Research Foundation - Flanders, Nordic Centre of Excellence (Norway)
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union 2015
• Subjects: Arctic; Arctic Ocean; Duarte; Greenland; Ocean acidification
• Online Access: http://hdl.handle.net/10261/122949; https://doi.org/10.5194/bg-12-4895-2015; https://doi.org/10.13039/501100003130

Krause-Jensen, D., Duarte, C.M., Hendriks, I.E., Meire, L., Blicher, M.E., Marbà, N., and Sejr, M.K. (2015). Macroalgae contribute to nested mosaics of pH variability in a sub-Arctic fjord. Biogeosciences, 12: 4907-4945. DOI:10.5194/bgd-12-4907-2015 The Arctic Ocean is considered the most vulnerable ecosystem to ocean acidification, and large-scale assessments of pH and the saturation state for aragonite (Ωarag) have led to the notion that the Arctic Ocean is already close to a corrosive state. In high-latitude coastal waters the regulation of pH and Ωarag is, however, far more complex than offshore because increased biological activity and input of glacial meltwater affect pH. Effects of ocean acidification on calcifiers and non-calcifying phototrophs occupying coastal habitats cannot be derived from extrapolation of current and forecasted offshore conditions, but they require an understanding of the regimes of pH and Ωarag in their coastal habitats. To increase knowledge of the natural variability in pH in the Arctic coastal zone and specifically to test the influence of benthic vegetated habitats, we quantified pH variability in a Greenland fjord in a nested-scale approach. A sensor array logging pH, O2, PAR, temperature and salinity was applied on spatial scales ranging from kilometre scale across the horizontal extension of the fjord; to 100 m scale vertically in the fjord, 10–100 m scale between subtidal habitats with and without kelp forests and between vegetated tidal pools and adjacent vegetated shores; and to centimetre to metre scale within kelp forests and millimetre scale across diffusive boundary layers of macrophyte tissue. In addition, we assessed the temporal variability in pH on diurnal and seasonal scales. Based on pH measurements combined with point samples of total alkalinity, dissolved inorganic carbon and relationships to salinity, we also estimated variability in Ωarag. Results show variability in pH and Ωarag of up to 0.2–0.3 units at several scales, i.e. along the horizontal and ...