Effect of diet, anthropogenic activity, and climate on δ 15 N values of cave bat guano Daniel M. Cleary a,b , Bogdan P. Onac a,b,c, ⁎, Ferenc L. Forray b , Jonathan G. Wynn a,b a Karst Research Group, School of Geosciences, University of South Florida, 4202 E. Fowler Ave., NES 107, Tampa FL 33620, USA b Department of Geology, Babeș-Bolyai University, Kogălniceanu 1, 400084 Cluj-Napoca, Romania c Emil Racoviţă Institute of Speleology, Clinicilor 5, 400006 Cluj-Napoca, Romania abstract article info Article history: Received 11 March 2016 Received in revised form 8 August 2016 Accepted 11 August 2016 Available online 14 August 2016 Few studies have attributed δ 15 N values of guano to a factor other than diet. A δ 15 N record obtained from a 1.5-m core of bat guano deposit from Zidită Cave (western Romania) provides a record of anthropogenic and climatic influence on the regional nitrogen pool. Nitrogen content is nearly constant (%N N 9) for over 1 m of the core, indicating limited diagenesis. The δ 15 N and δ 13 C time series are compared and the δ 15 N is also interpreted in light of previously published pollen assemblage from the same core. Using these comparisons the influence of an- thropogenic activity and water availability is interpreted. Although some δ 15 N variation can be attributed to major changes in anthropogenic activities, additional variation implies an alternative control. The correlation between δ 15 N and δ 13 C values is significant (p b 0.01), but not strong, suggesting that both variables are influ- enced by water availability, known to be a primary control of δ 13 C values within C 3 ecosystems. Drier periods indicated by higher δ 13 C values correspond with lower δ 15 N values and vice-versa for wetter conditions. The in- strumental climate record (precipitation amount) for the past 50 years nearby the cave supports this relation- ship. From 1000 to 1800 CE, the δ 15 N values fluctuated between 11.5 and 14‰, then decreased in two abrupt steps, at 1800 and 1947 CE. The most significant decrease occurred after 1947 CE when values fell from 12.5 to below 7‰, suggesting the N-cycle transitioned towards a more conservative state. The correlations between δ 15 N and δ 13 C, and the instrumental precipitation record, along with the apparent negligible effect of diet on long term δ 15 N variation indicate that the δ 15 N values of guano can be used as an integrator of the local N-cycle. © 2016 Elsevier B.V. All rights reserved. Keywords: Bat guano Cave Nitrogen and carbon isotopes Pollen Paleoenvironment Nitrogen cycling Romania 1. Introduction Caves are frequently suitable sites for paleoclimate and paleo- environmental studies because their deposits are protected from surfi- cial weathering. A generally untapped archive is preserved in bat guano, which can be found in many caves and can be precisely dated using radiocarbon (McFarlane et al., 2002; Bird et al., 2007; Wurster et al., 2007; Onac et al., 2015; Royer et al., 2015). Guano deposits are pri- marily composed of unconsolidated organic material (insect remains), sometimes interbedded with clays (Mizutani et al., 1992a; Onac et al., 2014). When bioturbation and diagenesis are minimal, the original stratigraphy of the guano deposit may be preserved. Paleoenvironmental reconstructions using guano have focused primarily on stable isotope records such as bulk δ 13 C values, δ = [(R sample − R standard ) ∕ (R standard )] x 1000; R = 13 C/ 12 C; Mizutani et al., 1992b; Wurster et al., 2007; Forray et al., 2015), pollen (Maher, 2006; Geantă et al., 2012), δ 2 H in chitin (Wurster et al., 2010), as well as chemical composition (Bird et al., 2007; Onac et al., 2015; Wurster et al., 2015). In contrast, the nitrogen (N) isotopic composition of guano has received far less attention. Using the well-defined 3–4‰ in- crease in δ 15 N values with each higher trophic position (e.g., DeNiro and Epstein, 1981; Peterson and Fry, 1987; Koch et al., 1994), guano N studies have often been limited to confirmation of the diet and trophic position of the bats (Mizutani et al., 1992a; Bird et al., 2007). However, Mizutani et al. (1992a) reported a latitudinal dependence of 15 N enrich- ment in guano at caves in Jamaica and the southwestern United States, reflecting trends in aridity or climate. Meanwhile, other organic mate- rials used as paleoenvironmental proxies have shown that δ 15 N values can provide additional resources to the more commonly used δ 13 C and δ 2 H values (Esmeijer-Liu et al., 2012; Szpak, 2014). In addition to re- cords of long-term paleoenvironmental changes, δ 15 N values in guano may also track the degree to which anthropogenic activities (deforesta- tion, fertilizer usage, controlled fires, etc.) and climate may have impact- ed the local ecosystem. The use of δ 15 N in guano has eluded paleoenvironmental science for mainly two reasons: 1) the potential of digenetic alteration of δ 15 N sig- nal in guano and 2) the complicated nature of the N cycle (Bird et al., 2007; Wurster et al., 2007). The first condition relates to microbial Palaeogeography, Palaeoclimatology, Palaeoecology 461 (2016) 87–97 ⁎ Corresponding author at: School of Geosciences, University of South Florida, 4202 E. Fowler Ave., NES 107, Tampa FL 33620, USA. E-mail address: bonac@usf.edu (B.P. Onac). http://dx.doi.org/10.1016/j.palaeo.2016.08.012 0031-0182/© 2016 Elsevier B.V. All rights reserved. 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