Decreased calcification in the Southern Ocean over the satellite record

Abstract

Widespread ocean acidification is occurring as the ocean absorbs anthropogenic carbon dioxide from the atmosphere, threatening marine ecosystems, particularly the calcifying plankton that provide the base of the marine food chain and play a key role within the global carbon cycle. We use satellite estimates of particulate inorganic carbon (PIC), surface chlorophyll, and sea surface temperature to provide a first estimate of changing calcification rates throughout the Southern Ocean. From 1998 to 2014 we observe a 4% basin‐wide reduction in summer calcification, with ∼9% reductions in large regions (∼1 × 106 km2) of the Pacific and Indian sectors. Southern Ocean trends are spatially heterogeneous and primarily driven by changes in PIC concentration (suspended calcite), which has declined by ∼24% in these regions. The observed decline in Southern Ocean calcification and PIC is suggestive of large‐scale changes in the carbon cycle and provides insight into organism vulnerability in a changing environment.

Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone

“…Cubillos et al (2007) and Winter et al (2014) postulated that E. huxleyi has expanded its ecological niche south of the Polar Front in recent decades. Contrastingly, Freeman and Lovenduski (2015) suggested an overall decline in Southern Ocean PIC concentrations using satellite records between 1998 and 2014. The explanation of these contrasting results may lie in the methodologies applied.…”

A multi-decade record of high-quality <i>f</i>CO<sub>2</sub> data in version 3 of the Surface Ocean CO<sub>2</sub> Atlas (SOCAT)

“…A number of studies estimate trends in surface ocean pH or the carbonate concentration by combining SOCAT f CO 2 values with another carbonate parameter (Lauvset and Gruber, 2014;Freeman and Lovenduski, 2015;Lauvset et al, 2015).…”

Phytoplankton Blooms at Increasing Levels of Atmospheric Carbon Dioxide: Experimental Evidence for Negative Effects on Prymnesiophytes and Positive on Small Picoeukaryotes

“…However, whether they will amplify or mitigate the observed CO 2 effects is impossible to forecast, although it is unlikely that the trends in certain groups will simply reverse as nutrients, light and temperature have stimulating effects on the entire phytoplankton community. Currently, there are reports suggesting decreasing coccolithophore abundances/calcification in the Southern Ocean (Freeman and Lovenduski, 2015), poleward expansion (Winter et al, 2014) or a subtropical North Atlantic increase (Krumhardt et al, 2016) over the past decades. Given the more than an order of magnitude larger increase in atmospheric CO 2 levels projected until the end of the the century in comparison to that during the past decades, these reports and our findings and conclusions are not a contradiction.…”