Acceleration of modern acidification in the South China Sea driven by anthropogenic CO2

Abstract

Modern acidification by the uptake of anthropogenic CO2 can profoundly affect the physiology of marine organisms and the structure of ocean ecosystems. Centennial-scale global and regional influences of anthropogenic CO2 remain largely unknown due to limited instrumental pH records. Here we present coral boron isotope-inferred pH records for two periods from the South China Sea: AD 1048–1079 and AD 1838–2001. There are no significant pH differences between the first period at the Medieval Warm Period and AD 1830–1870. However, we find anomalous and unprecedented acidification during the 20th century, pacing the observed increase in atmospheric CO2. Moreover, pH value also varies in phase with inter-decadal changes in Asian Winter Monsoon intensity. As the level of atmospheric CO2 keeps rising, the coupling global warming via weakening the winter monsoon intensity could exacerbate acidification of the South China Sea and threaten this expansive shallow water marine ecosystem.

Historical Trends in pH and Carbonate Biogeochemistry on the Belize Mesoamerican Barrier Reef System

“…One such proxy that has received much attention is the boron isotope pH proxy (e.g., Goodkin et al, 2015;Liu et al, 2014;Pelejero et al, 2005;Wei et al, 2009). It is therefore unlikely that the ecosystem level response of coral reefs to historic anthropogenic oceanic change can be estimated from direct measurements.…”

“…Instead, we use equations developed for the coral species Porites cylindrica (Liu et al, 2014;McCulloch et al, 2012;Trotter et al, 2011) to estimate seawater pH (pH sw ) from the pH cf : Instead, we use equations developed for the coral species Porites cylindrica (Liu et al, 2014;McCulloch et al, 2012;Trotter et al, 2011) to estimate seawater pH (pH sw ) from the pH cf :…”

“…Instead, we must turn to geochemical proxies. One such proxy that has received much attention is the boron isotope pH proxy (e.g., Goodkin et al, 2015;Liu et al, 2014;Pelejero et al, 2005;Wei et al, 2009). There are two aqueous species of boron in seawater (boric acid and borate ion), and their relative abundance depends primarily on pH (Dickson, 1990).…”

“…Nevertheless, because changes in seawater pH have been shown to cause changes in coral calcifying fluid pH (e.g., Ries, 2011), coral skeletal δ 11 B tracks seawater δ 11 B bor and there is a consistent relationship between internal and external pH (e.g., Holcomb et al (2014)). This permits the reconstruction of seawater pH at annual resolution from the boron isotope composition of coral skeletons using species specific δ 11 B-pH calibrations (e.g., Liu et al, 2014;Trotter et al, 2011).…”

What is at stake? Status and threats to South China Sea marine fisheries

“…Moreover, shifts in species distribution can potentially lead to increased transboundary fisheries disputes (Miller et al 2013), particularly given the highly contested territorial claims over parts of the SCS. Expected increases in atmospheric CO 2 levels are likely to exacerbate the impact of ocean acidification on shallow water marine life in the SCS (Liu et al 2014). While the frequency of tropical cyclones is expected to decrease in the region, their intensity is projected to rise, resulting in increased damage to coastal habitats and severe human and economic costs (World Bank 2013).…”