Warming Influences Mg²⁺ Content, While Warming and Acidification Influence Calcification and Test Strength of a Sea Urchin

Abstract

We examined the long-term effects of near-future changes in temperature and acidification on skeletal mineralogy, thickness, and strength in the sea urchin Tripneustes gratilla reared in all combinations of three pH (pH 8.1, 7.8, 7.6) and three temperatures (22 °C, 25 °C, 28 °C) from the early juvenile to adult, over 146 days. As the high-magnesium calcite of the echinoderm skeleton is a biomineral form highly sensitive to acidification, and influenced by temperature, we documented the MgCO3 content of the spines, test plates, and teeth. The percentage of MgCO3 varied systematically, with more Mg2+ in the test and spines. The percentage of MgCO3 in the test and teeth, but not the spines increased with temperature. Acidification did not change the percentage MgCO3. Test thickness increased with warming and decreased at pH 7.6, with no interaction between these factors. In crushing tests live urchins mostly ruptured at sutures between the plates. The force required to crush a live urchin was reduced in animals reared in low pH conditions but increased in those reared in warm conditions, a result driven by differences in urchin size. It appears that the interactive effects of warming and acidification on the Mg2+ content and protective function of the sea urchin skeleton will play out in a complex way as global climatic change unfolds.

Risk and resilience: variations in magnesium in echinoid skeletal calcite

“…Fabricius et al 2014, Uthicke et al 2016, while others are not (Calosi et al 2013). In addition, the mineralogy of the test of Tripneustes gratilla reared in ocean acidification conditions from the very early juvenile (5 mm) to the mature adult stage (~60 mm) did not differ from that of urchins reared in control present-day conditions (Byrne et al 2014).…”

“…Studies on the reduction in strength caused by exposure to acidified sea water thus far have concentrated on test thickness of adults, in terms of resistance to predators crushing whole skeletons (e.g. Asnaghi et al 2014, Byrne et al 2014. Similar investigation of individual skeletal elements and/or juveniles is the next step.…”

Biogenic acidification drives density-dependent growth of a calcifying invertebrate in culture

“…Studies that have tested the effects of high pCO 2 on sea urchins, including T. gratilla, have found impaired growth and development of larvae (Albright et al 2012;Byrne et al 2011Byrne et al , 2013Doo et al 2012;Sheppard Brennand et al 2010;Stumpp et al 2012) and reductions in growth, consumption rates and FCE of juveniles and adults (Albright et al 2012;Byrne et al 2014;Grosjean et al 1998;Shirayama and Thornton 2005;Siikavuopio et al 2007c;Stumpp et al 2012;Wolfe et al 2013a, b). Like the present study, other species of dissolved inorganic carbon would have covaried with pCO 2 in all of these studies.…”

Developments since 2005 in understanding potential environmental impacts of CO2 leakage from geological storage

“…In these situations biogenic carbonate structures (bivalve shells, urchin tests and corals) will undergo dissolution to liberate aqueous carbonate ions. The dissolution of biogenic calcified structures has been widely reported (Gazeau et al, 2007;Gazeau, 2008, Byrne et al, 2014 with effects generally more pronounced in juvenile and larval stages (Talmage and Gobler, 2009;Sheppard Brennand et al, 2010, Stumpp et al, 2012, Long et al, 2013, Hu et al, 2014. However, these impacts are not universal, and notable exceptions (normal calcification, hypercalcification) have been reported (e.g.…”