Growth rate rather than temperature affects the B∕Ca ratio in the calcareous red alga <i>Lithothamnion corallioides</i>

<p>The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="0f999d1a4e097c24f1ad042959464cfe"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00004.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00004.png"/></svg:svg></span></span> ratio in calcareous marine species is informative of past seawater CO<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="490d7ecf09fa5682b13318d48526c23f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00005.svg" width="13pt" height="17pt" src="bg-19-1047-2022-ie00005.png"/></svg:svg></span></span> concentrations, but scarce data exist on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7ff65a833488bf1ffc834b275f39e1d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00006.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00006.png"/></svg:svg></span></span> in coralline algae. Recent studies suggest influences of temperature and growth rates on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="171d22a3c19a0d1f8a371d3188f68171"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00007.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00007.png"/></svg:svg></span></span>, the effect of which could be critical for the reconstructions of surface ocean pH and atmospheric <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula">₂</span>. In this paper, we present the first laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of Mg, Sr, Li, and B in the coralline alga <i>Lithothamnion corallioides</i> collected from different geographic settings and depths across the Mediterranean Sea and in the Atlantic Ocean. We produced the first data on putative temperature proxies (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Mg</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="37pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d1f58fc3a76bb75dfaa8c6e5d7932caa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00008.svg" width="37pt" height="14pt" src="bg-19-1047-2022-ie00008.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Li</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="50621674f39f5938ff3cb1b598033eaa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00009.svg" width="31pt" height="14pt" src="bg-19-1047-2022-ie00009.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Sr</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7a25d1af185cb50eba192ad4c421755f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00010.svg" width="33pt" height="14pt" src="bg-19-1047-2022-ie00010.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Mg</mi><mo>/</mo><mi mathvariant="normal">Li</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="bdd51dd57fe955c30ebf4e84889192fe"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00011.svg" width="32pt" height="14pt" src="bg-19-1047-2022-ie00011.png"/></svg:svg></span></span>) and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f1f79cc49191c1df7b568c2395dce8ee"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00012.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00012.png"/></svg:svg></span></span> in a coralline algal species grown in different basins from across the photic zone (12, 40, 45, and 66 m depth). We tested the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fa262b09298be535c8d15ab3220327b0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00013.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00013.png"/></svg:svg></span></span> correlation with temperature proxies and growth rates in order to evaluate their possible effect on B incorporation. Our results suggested a growth rate influence on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d25b0067b11885191d14df9ead3e2df9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00014.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00014.png"/></svg:svg></span></span>, which was evident in the sample with the lowest growth rate of 0.10 mm yr<span class="inline-formula">⁻¹</span> (Pontian Isl., Italy; 66 m depth) and in Elba (Italy; 45 m depth), where the algal growth rate was the highest (0.14 mm yr<span class="inline-formula">⁻¹</span>). At these two sites, the measured <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fd2ad9c475e5eecb8e7c3103707d576a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00015.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00015.png"/></svg:svg></span></span> was the lowest at 462.8 <span class="inline-formula">±</span> 49.2 <span class="inline-formula">µ</span>mol mol<span class="inline-formula">⁻¹</span> and the highest at 757.7 <span class="inline-formula">±</span> 75.5 <span class="inline-formula">µ</span>mol mol<span class="inline-formula">⁻¹</span>, respectively. A positive correlation between <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="2feca14fc2dfb797b265f6c6001dea87"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00016.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00016.png"/></svg:svg></span></span> and temperature proxies was found only in the shallowest sample from Morlaix (Atlantic coast of France; 12 m depth), where the amplitude of temperature variation (<span class="inline-formula">Δ<i>T</i></span>) was the highest (8.9 <span class="inline-formula">^∘</span>C). Still, fluctuations in <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">B</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d34b9e112fa6ab96535a8cfd8ae16e60"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00017.svg" width="30pt" height="14pt" src="bg-19-1047-2022-ie00017.png"/></svg:svg></span></span> did not mirror yearly seasonal temperature oscillations as for <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M29" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Mg</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="37pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="8d41f2be441c6261b5bc3898456c0e3c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00018.svg" width="37pt" height="14pt" src="bg-19-1047-2022-ie00018.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Li</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="876ccf0c3ed2e94eced0ad19459f461d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00019.svg" width="31pt" height="14pt" src="bg-19-1047-2022-ie00019.png"/></svg:svg></span></span>, and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M31" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Sr</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="33pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f7a0ea0908d23c7d18b2100a228874fa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-1047-2022-ie00020.svg" width="33pt" height="14pt" src="bg-19-1047-2022-ie00020.png"/></svg:svg></span></span>. We concluded that growth rates, triggered by the different <span class="inline-formula">Δ<i>T</i></span> and light availability across depth, affect the B incorporation in <i>L. corallioides</i>.</p>