Conditions of Mytilus edulis extracellular body fluids and shell composition in a pH‐treatment experiment: Acid‐base status, trace elements and δ¹¹B

Abstract

[1] Mytilus edulis were cultured for 3 months under six different seawater pCO 2 levels ranging from 380 to 4000 matm. Specimen were taken from Kiel Fjord (Western Baltic Sea, Germany) which is a habitat with high and variable seawater pCO 2 and related shifts in carbonate system speciation (e.g., low pH and low CaCO 3 saturation state). Hemolymph (HL) and extrapallial fluid (EPF) samples were analyzed for pH and total dissolved inorganic carbon (C T ) to calculate pCO 2 and [HCO 3 − ]. A second experiment was conducted for 2 months with three different pCO 2 levels (380, 1400 and 4000 matm). Boron isotopes (d 11 B) were investigated by LA-MC-ICP-MS (Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry) in shell portions precipitated during experimental treatment time. Additionally, elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF of specimen from the second experiment were measured via ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry). Extracellular pH was not significantly different in HL and EPF but systematically lower than ambient water pH. This is due to high extracellular pCO 2 values, a prerequisite for metabolic CO 2 excretion. No accumulation of extracellular [HCO 3 − ] was measured. Elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF increased slightly with pH which is in accordance with increasing growth and calcification rates at higher seawater pH values. Boron isotope ratios were highly variable between different individuals but also within single shells. This corresponds to a high individual variability in fluid B/Ca ratios and may be due to high boron concentrations in the organic parts of the shell. The mean d 11 B value shows no trend with pH but appears to represent internal pH (EPF) rather than ambient water pH.

<i>δ</i><sup>11</sup>B as monitor of calcification site pH in divergent marine calcifying organisms

“…For example, prior studies have shown that for a given pH SW , δ 11 B CaCO 3 of the coral species Porites cylindrica and Acropora nobilis are moderately elevated relative to δ 11 B CaCO 3 of the foraminifera Globigerinoides sacculifer and substantially elevated relative to δ 11 B CaCO 3 of the mussel Mytilus edulis ( Fig. 2; Heinemann et al, 2012;Sanyal et al, 2001). One possible explanation for these differences is that corals are maintaining their calcifying fluids at higher pH than the calcifying fluids of foraminifera, which are in turn elevated relative to the pH CF of mussels.…”

Mollusc and brachiopod skeletal hard parts: Intricate archives of their marine environment

“…The pH of mollusc body fluid ranges between 7·4 and 8·3 (Hahn et al ., ; Heinemann et al ., ) but generally remains below that of seawater. Similarly, Crenshaw () reported values ranging between 7·33 and 7·41 for three different molluscs.…”

“…It is acknowledged that fluid pH is but one of the many factors that influence δ 13 C carb . Nevertheless, pH is important because body fluids of modern molluscs and brachiopods are in most cases lower (7·2 to 7·5) than that of coeval seawater ( ca 8·0) but, in some cases, authors also reported body fluid pH values above 8·0 (Hahn et al ., ; Heinemann et al ., ). Assuming δ 13 C CO2 of −7‰ for the present‐day atmosphere (Bottinga & Craig, ) and combining published equilibrium fractionation factors (Thode et al ., ; Vogel et al ., ; Mook et al ., ) with the distribution coefficients, the δ 13 C values and the amounts of different carbonate species using the software ‘PhreeqC’ and the database ‘wateq4F’ can be calculated (Table ).…”

Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured <i>Arctica islandica</i>

“…However, due to the ability of calcifying organisms to buffer their own local environments, speciesspecific fractionation factors and transfer functions are likely (Anagnostou et al, 2012;Krief et al, 2010;Rae et al, 2011;Reynaud et al, 2004Reynaud et al, , 2008Trotter et al, 2011). Thus far, the pH − δ 11 B relationship has been tested extensively on some biogenic marine carbonates, primarily foraminifera and coral records, with broad success (Anagnostou et al, 2012;Henehan et al, 2013;Ni et al, 2007;Rae et al, 2011;Reynaud et al, 2004); a few measurements have been made on calcite shells (Heinemann et al, 2012;Penman et al, 2012), but no published data exist for aragonitic bivalves.…”