Oxygen isotope fractionation between bird eggshell calcite and body water: application to fossil eggs from Lanzarote (Canary Islands)

Abstract

Oxygen and carbon isotope compositions of fossil bird eggshell calcite (δ 18 Ocalc and δ 13 Ccalc) are regularly used to reconstruct paleoenvironmental conditions. However, the interpretation of δ 18 Ocalc values of fossil eggshells has been limited to qualitative variations in local climatic conditions as oxygen isotope fractionations between calcite, body fluids, and drinking water have not been determined yet. For this purpose, eggshell, albumen water, and drinking water of extant birds have been analyzed for their oxygen and carbon isotope compositions. Relative enrichments in 18 O relative to 16O between body fluids and drinking water of +1.6 ± 0.9 ‰ for semi-aquatic birds and of +4.4 ± 1.9‰for terrestrial birds are observed. Surprisingly, no significant dependence to body temperature on the oxygen isotope fractionation between eggshell calcite and body fluids is observed, suggesting that bird eggshells precipitate out of equilibrium. Two empirical equations relating the δ 18 Ocalc value of eggshell calcite to the δ 18 Ow value of ingested water have been established for terrestrial and semi-aquatic birds. These equations have been applied to fossil eggshells from Lanzarote in order to infer the ecologies of the Pleistocene marine bird Puffinus sp. and of the enigmatic giant birds

δ18O‐derived incubation temperatures of oviraptorosaur eggs

“…Pooling this fractionation factor with those established for five extant birds (the common quail Coturnix coturnix , the chicken Gallus gallus , the Egyptian goose Alopochen aegyptiaca , the mallard duck Anas platyrhynchos and the ostrich Strutio camelus ; Table ; Lazzerini et al . ), no relationship was observed between α c–ew and body temperature (Fig. A).…”

“…According to Lazzerini et al . (), terrestrial birds display a drinking water‐body water 18 O‐enrichment of about +4‰ (at least in ostrich and chicken). Based on the egg water δ 18 O ew value of −5.7‰ calculated for NHGM10876, a δ 18 O w value of local surface waters of about −9.7‰ can be estimated.…”

“…A recent study has established a significant relationship between the δ 18 O c value of bird eggshell carbonate and that of the egg albumen water, both originating from the mother's body fluids (Lazzerini et al . ). Therefore, it should be possible to estimate the oxygen isotope composition of the egg water from the eggshell δ 18 O c value, and then calculate the bone formation temperature using the well‐established oxygen isotope phosphate‐water temperature scale (Lécuyer et al .…”

Cracking the egg: the use of modern and fossil eggs for ecological, environmental and biological interpretation

“…Later, Johnson et al [ 18 ] would find that the linear relationship between δ 18 O of eggshell carbonate and water source did not hold true in wild ostriches, indicating that this relationship might not be a reasonable assumption to make in open ecosystems where body water is obtained from a variety of sources such as plants. Lazzerini et al [ 40 ] calculated the oxygen isotope fractionation between ingested water and eggshell calcite and found it is in fact correlated in numerous bird species and could be used for palaeoenvironmental reconstruction, but the amount of enrichment was different for terrestrial and semi-aquatic birds. Even if absolute oxygen isotope fractionation factors are not known, Miller & Fogel [ 41 ] illustrated with modern emu eggshell from around Australia that eggshell δ 18 O can be a strong proxy for both modern and palaeo-aridity, emphasizing the importance of δ 18 O in the inorganic portion of eggshells for reconstructing palaeoenvironments.…”

Thermophysiologies of Jurassic marine crocodylomorphs inferred from the oxygen isotope composition of their tooth apatite

“…Air-breathing vertebrates have a body water 18 O-enriched relative to environmental water, the magnitude of which depends on the amount of body water loss through exhaled water vapour and transcutaneous evaporation. Direct measurements have shown that terrestrial mammals and birds have body water from about 4 to 7‰ 18 O-enriched relative to their drinking water [33][34][35], whereas the body waters of semi-aquatic to aquatic crocodylians, turtles and birds are about 2 to 3‰ 18 Oenriched relative to their drinking water [33,36,37].…”