Oxygen isotope ratios of chironomids, aquatic macrophytes and ostracods for lake-water isotopic reconstructions ? results of a calibration study from Patagonia

MAYR; JULIETA MASSAFERRO; LAPRIDA, CECILIA; RAMON MERCAU; OLHENDORF

JOURNAL OF HYDROLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 529 p. 600 - 617

0022-1694

xygen stable isotopes (δ18O) of biogenic sedimentary components from lake sediment22 archives, such as ostracod valves, are frequently used for palaeoclimatic reconstructions.23 However, the effects of host water isotope changes, temperature-dependent fractionations,24 and vital effects on the isotopic ratios of such biogenic proxies often cannot be disentangled.25 Here, δ18O values of ostracod valves, chironomid head capsules and aquatic macrophyte 26 cellulosefromvariouslakeandstreamsitesinsouthernPatagonia(41?52°S)arecompared27 with δ18O values of their host waters. The best correlation between δ18O values of bioproxy28 and host water was obtained for aquatic cellulose exhibiting a slope of the regression of29 almost unity. Chironomid head capsules showed a strong correlation, but the data set was30 rather small (seven sites). The δ18O values of ostracod valves showed strong inter-specific31 vital effects. Generally strong offsets of valves from isotopic equilibrium values are possibly32 explained by re-working of subfossil valves, seasonality effects or different chemical33 composition of host waters. A weak, but significant temperature dependency of oxygen34 isotope fractionation was observed for cellulose of one aquatic taxon (Myriophyllum) and for35 ostracod calcite, but not for chironomids and aquatic moss cellulose. The present dataset36 suggests that δ18O of aquatic cellulose is the most reliable proxy for host water isotope37 reconstructions, but clearly more investigations are needed to substantiate this finding