Ostracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van example

Abstract

Abstract. Ostracods are common lacustrine calcitic microfossils. Their faunal assemblage and morphological characteristics are important ecological proxies, and their valves are archives of geochemical information related to palaeoclimatic and palaeohydrological changes. In an attempt to assess ostracod ecology (taxonomic diversity and valve morphology) combined with valve geochemistry (δ18O and δ13C) as palaeosalinity indicators, we analysed sedimentary material from the International Continental Scientific Drilling Program (ICDP) Ahlat Ridge site from a terminal and alkaline lake, Lake Van (Turkey), covering the last 150 kyr. Despite a low species diversity, the ostracod faunal assemblage reacted sensitively to changes in the concentration of total dissolved salts in their aquatic environment. Limnocythere inopinata is present throughout the studied interval, while Limnocythere sp. A is restricted to the Last Glacial period and related to increased lake water salinity and alkalinity. The presence of species belonging to the genus Candona is limited to periods of lower salinity. Valves of Limnocytherinae species (incl. L. inopinata) display nodes (hollow protrusions) during intervals of increased salinity. Both the number of noded valves and the number of nodes per valve appear to increase with rising salinity, suggesting that node formation is related to hydrological changes (salinity and/or alkalinity). In contrast to Lake Van's bulk δ18O record, the δ18O values of ostracod valves do record relative changes of the lake volume, with lower values during high lake level periods. The δ13C values of different species reflect ostracod habitat preferences (i.e. infaunal vs. epifaunal) but are less sensitive to hydrological changes. However, combined with other proxies, decreasing Holocene δ13C values may indicate a freshening of the lake water compared to the low lake level during the Last Glacial period. The Lake Van example underscores the significance and value of coupling ostracod ecology and valve geochemistry in palaeoenvironmental studies of endorheic lake basins.

Coeval primary and diagenetic carbonates in lacustrine sediments challenge palaeoclimate interpretations

“…The additional references provide further information on the isotopic composition and environmental context of the individual carbonate components. SEM images of aragonite, low-Mg calcite and dolomite are from McCormack et al 14 , images of ostracod valves are from McCormack et al 31 .

Figure 2 Compilation of images of diagenetic aragonite encrustations.

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“…( a ) Bulk oxygen isotopy (δ 18 O bulk ) 9 . ( b ) δ 18 O of different carbonate phases and (b) δ 13 C of different carbonate phases 14 , 25 , 31 . ( d ) Estimated bottom-water δ 18 O from deep-water carbonates, calculated for a constant temperature of 3.3 °C and using mineralogy specific fractionation factors (calcite 32 , aragonite 27 , dolomite 26 ).…”

Life stages and morphological variations of Limnocythere inopinata (Crustacea, Ostracoda) from Lake Jiang-Co (northern Tibet): a bioculture experiment

“…Living populations of L. inopinata have been reported from Europe, Asia, and Africa. The European populations include: Austria ( Löffler 1990 ; Yin et al 1999 ; Rossi et al 2010 ), Germany ( von Grafenstein et al 1999 ; Frenzel et al 2010 ; Scharf et al 2013), Greece ( Frogley et al 2001 ), Iceland ( Alkalaj et al 2019 ), Italy ( Rossi et al 2010 ; Marta et al 2017), Poland ( Szlauer-Łukaszewska 2014 , 2015a , b ), Spain ( Mezquita et al 1999 ; Rodríguez-Pérez and Baltanás 2008 ; Martínez-García et al 2015 ), Sweden ( Iglikowska and Namiotko 2012 ), Switzerland ( Decrouy et al 2012 , 2014), Turkey ( Külköylüoğlu et al 2016 ; McCormack et al 2019 ), and United Kingdom ( Benzie 1989 ; Holmes et al 2010 ). The Asian populations were recorded from China ( Mischke et al 2003 ; Zhang et al 2015 ; Akita et al 2016 ), India ( Kramer et al 2014 ), Israel ( Mischke et al 2012 ), and Jordan ( Mischke et al 2012 ).…”

“…The ecological characteristics of L. inopinata have been commonly used to infer paleoecological conditions (e.g., Shen et al 2001 ; Poberezhnaya et al 2006 ; McCormack et al 2019 ). This species has been reported from a variety of water bodies ( Geiger 1994 ), including ponds, swamps, lakes, and rivers.…”

Holocene paleoenvironmental evolution of the Acıgöl paleo maar lake (Nevşehir, Central Anatolia)

“…Therefore, many studies have been realised on Neogene-Quaternary archive records of the fossil lakes and/ or ponds of Anatolia to determine the ostracod fauna. Studies on Quaternary deposits (Şafak and Taner 1998;Beker et al 2008;Meriç et al 2009;Tunoğlu et al 2012;Ocakoğlu et al 2013Ocakoğlu et al , 2016Tuncer and Tunoğlu 2015;Karayiğit et al 2016;Tuncer et al 2017;Berndt et al 2019a, b;McCormack et al 2019) are rare by comparison with European/ Palearctic counterparts (Scharf 1983(Scharf , 1993Ricci Lucchi et al 2000;Viehberg 2004;Scharf et al 2005;Wilkinson et al 2005;Pipík and Bubik 2006;Meidla 2009, 2010;Anadón et al 2012;Bellucci et al 2012;Kalbe et al 2015;Mazzini et al 2015;Hajek-Tadesse et al 2018).…”