Ocean acidification does not impact shell growth or repair of the Antarctic brachiopod Liothyrella uva (Broderip, 1833)

Abstract

Marine calcifiers are amongst the most vulnerable organisms to ocean acidification due to reduction in the availability of carbonate ions for skeletal/shell deposition. However, there are limited long-term studies on the possible impacts of increased pCO 2 on these taxa. A 7 month CO 2 perturbation experiment was performed on one of the most calcium carbonate dependent species, the Antarctic brachiopod Liothyrella uva, which inhabits the Southern Ocean where carbonate ion saturation levels are amongst the lowest on Earth. The effects of the predicted environmental conditions in 2050 and 2100 on the growth rate and ability to repair shell in L. uva were tested with four treatments; a low temperature control (0°C, pH 7.98), a pH control (2°C, pH 8.05), mid-century scenario (2°C, pH 7.75) and end-century scenario (2°C, pH 7.54). Environmental change impacts on shell repair are rarely studied, but here repair was not affected by either acidified conditions or temperature. Growth rate was also not impacted by low pH. Elevated temperature did, however, increase growth rates. The ability of L. uva to continue, and even increase shell production in warmer and acidified seawater suggests that this species can acclimate to these combined stressors and generate suitable conditions for shell growth at the site of calcification.

Variation in brachiopod microstructure and isotope geochemistry under low-pH–ocean acidification conditions

“…Cross et al (2018) found that punctae became narrower over the past 120 years, which partially explained the increase in shell density over this period. Overall, there appears to be little to no apparent effect on brachiopod morphology or chemistry with lower seawater pH (Cross et al, 2015(Cross et al, , 2016(Cross et al, , 2018.…”

“…This applies to calcium carbonate shell-forming species, such as brachiopods and mollusks, because they are considered excellent archives documenting F. Ye et al: Variation in brachiopod microstructure and isotope geochemistry changes in environmental conditions affecting marine organisms (e.g. Kurihara, 2008;Comeau et al, 2009;Hahn et al, 2012Hahn et al, , 2014Watson et al, 2012;Cross et al, 2015Cross et al, , 2016Cross et al, , 2018Crippa et al, 2016a;Milano et al, 2016;Garbelli et al, 2017;Jurikova et al, 2019).…”

“…Brachiopods possess a low-magnesium calcite shell, which should be more resistant compared to the more soluble forms of CaCO 3 such as aragonite and high-Mg calcite (Brand and Veizer, 1980;Morse et al, 2007). The shell microstructure of Rhynchonelliformean brachiopods has been used as a powerful tool to understand the biomineral's response to modern global ocean acidification and similar events in the geologic past (Payne and Clapham, 2012;Cross et al, 2015Cross et al, , 2016Garbelli et al, 2017). A comprehensive study focusing on fossil brachiopods during the end-Permian mass extinction showed that brachiopods produce shells with increased organic matter content during ocean acidification events (Garbelli et al, 2017).…”

A 120‐year record of resilience to environmental change in brachiopods

“…Biological implications of these changes are less well described and have largely been identified from organism responses in laboratory experiments lasting a few days to a few months (Riebesell & Gattuso, ). In recognition of the fundamental role played by seasonal phenotypic plasticity and genetic change across generations, long‐term experiments which allow for acclimation (Cross, Peck, & Harper, ; Cross, Peck, Lamare, & Harper, ; Hazan, Wangensteen, & Fine, ; Suckling et al., ) and/or adaptation potential in organisms with short generation times (Andersson et al., ; Collins, Rost, & Rynearson, ) are now being made. Although information from long‐term laboratory experiments is vital to reveal sensitivities of marine organisms, even they can still only predict responses from exposures of relatively short durations, of months or even a few years, to environmentally unrealistic conditions (Andersson et al., ; Riebesell & Gattuso, ).…”

“…Biological implications of these changes are less well described and have largely been identified from organism responses in laboratory experiments lasting a few days to a few months (Riebesell & Gattuso, 2015). In recognition of the fundamental role played by seasonal phenotypic plasticity and genetic change across generations, long-term experiments which allow for acclimation (Cross, Peck, & Harper, 2015;Cross, Peck, Lamare, & Harper, 2016;Hazan, Wangensteen, & Fine, 2014;Suckling et al, 2014) and/or adaptation potential in organisms with short generation times (Andersson et al, 2015;Collins, Rost, & Rynearson, 2014) are now being made. Although information from long-term laboratory experiments is vital to reveal sensitivities of marine organisms, even they can still only predict responses from exposures of relatively short durations, of months or even a few years, to environmentally unrealistic conditions experiments, including in situ mesocosms (Nagelkerken & Munday, 2015) and CO 2 vent sites (Fabricius et al, 2011;Hall-Spencer et al, 2008;Uthicke et al, 2016), are another common approach which allows for the investigation of impacts on more long-term scales and also often include responses at the community level and the physical, chemical and biological variability in their natural environments that cannot be recreated in laboratory experiments.…”