Palaeogeography, Palaeoclimatology, Palaeoecology 540 (2020) 109526
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Palaeogeography, Palaeoclimatology, Palaeoecology 540 (2020) 109526 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo High-resolution records of growth temperature and life history of two Nacella limpet species, Tierra del Fuego, Argentina T ⁎ Adam Nicastroa, Donna Surgea, , Ivan Briz i Godinob,d,f, Myrian Álvarezb, Bernd R. Schönec, Maria Basb,e a Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA b CONICET- Centro Austral de Investigaciones Científicas, Ushuaia, Argentina c Institute of Geosciences, Johannes Gutenberg-Universität Mainz, Mainz, Germany d Department of Archaeology, University of York, York, UK e Department of Evolutionary Biology, Ecology and Environmental Science, Biodiversity Research Institute (IRBio), University of Barcelona, Barcelona, Spain f DRCLAS at Harvard University, Cambridge, MA, USA ARTICLE INFO ABSTRACT Keywords: Stable isotope ratios in patelloid limpets of the genus Patella have been established as proxies for coastal en- Sclerochronology vironmental change at sub-monthly resolution along the eastern North Atlantic and Mediterranean Sea. Nacella Oxygen and stable carbon isotopes deaurata (Gmelin 1791) and N. magellanica (Gmelin 1791) are common intertidal species of patelloid limpets Temperature proxy inhabiting the coast of Tierra del Fuego, Argentina/Chile and are commonly found in Holocene archaeological South America deposits. Here, we examine oxygen and carbon isotope ratios (δ18O and δ13C , respectively) of modern Climate shell shell specimens of N. deaurata and N. magellanica to test the hypotheses that: 1) they form their shells in isotopic equilibrium with ambient water; and 2) prominent growth lines form annually. Based on growth margin analysis 18 of δ Oshell values, we identified a positive offset of 1.3 ± 0.4‰ (N. deaurata) and 1.3 ± 0.3‰ (N. magellanica) from expected equilibrium, similar to other patelloid limpets. Because the offset is relatively consistent between observed and expected values, it can be taken into account to reliably reconstruct growth temperature. Seawater temperature estimated from oxygen isotope time series data falls within the observed range. Thus, N. deaurata and N. magellenica shells serve as reliable proxy archives of seasonal variation in coastal seawater temperature. 13 Time series of δ Cshell values do not vary seasonally in all shells; hence, the influence on its variation requires 18 further study. The timing of prominent growth lines contextualized by the δ Oshell time series form twice a year and therefore cannot be used to estimate lifespan. Future isotopic analysis of archaeological Nacella shells can potentially provide much needed information about Holocene climate change at sub-monthly resolution from high-latitude South American locations, and contribute to our understanding of human behavior and human- climate interactions. 1. Introduction scales. Few of these proxy records capture changes to coastal environ- ments, which are particularly sensitive to changing climate conditions. Marine proxy archives are the foundation for extrapolating changes Even fewer paleoclimate data exist at decadal, annual, and seasonal in oceanographic conditions beyond the bounds of the instrumental time scales along coastlines in the Southern Ocean. Hence, a proxy record. Currently, records of paleoclimate in the Southern Ocean are record that can be resolved to sub-monthly resolution is necessary to relatively scarce when compared to records of paleoclimate from other understand seasonal variability in coastal environments from high ocean basins. Many of the limited paleoclimate proxy records in the southerly latitudes. Southern Ocean are derived from ice, marine, or lake sediment cores Stable isotopes in mollusc shells have been used to reconstruct pa- (Borromei and Quattrocchio, 2001; Borromei et al., 2010; Mauquoy leoclimate records to sub-monthly resolution. Most molluscs form their et al., 2004; Candel et al., 2009; Ponce et al., 2017). These records, shells in isotopic equilibrium with ambient water (Epstein et al., 1951, while temporally extensive, focus on centennial to millennial time 1953; Craig, 1957; Grossman and Ku, 1986), but this is not always the ⁎ Corresponding author at: University of North Carolina at Chapel Hill, Department of Geological Sciences, 104 South Road, CB #3315, Chapel Hill, NC 27559- 3315, USA. E-mail address: [email protected] (D. Surge). https://doi.org/10.1016/j.palaeo.2019.109526 Received 9 August 2019; Received in revised form 6 December 2019; Accepted 9 December 2019 Available online 13 December 2019 0031-0182/ © 2019 Elsevier B.V. All rights reserved. A. Nicastro, et al. Palaeogeography, Palaeoclimatology, Palaeoecology 540 (2020) 109526 case. Previous studies have shown that limpet species from the genus, 2.2. Geographic and oceanographic settings Patella, form their shells in isotopic disequilibrium with ambient water (e.g. Shackleton, 1973; Cohen and Tyson, 1995; Fenger et al., 2007; The Beagle Channel (54.8–55°S, 67.2–70°W) is a narrow waterway Ferguson et al., 2011; Surge et al., 2013; Parker et al., 2017; in the Tierra del Fuego Archipelago at the southern tip of South Prendergast and Schöne, 2017). In these studies, seawater temperatures America. It extends approximately 240 km from the Argentinian pro- were reliably reconstructed after subtracting a consistent, positive vince of Tierra del Fuego in the east to the western coast of the Chilean 18 offset in δ Oshell values relative to expected equilibrium values. Thus, if Province of Magallanes. This study is set in the eastern portion of the such offsets from expected equilibrium values are consistent in modern Beagle Channel, 64 km east of Ushuaia, Argentina (Fig. 2). This Ar- specimens, it can be accounted for to reliably reconstruct sea surface gentinean portion of the Beagle Channel coast has a long tradition of temperature (SST) in older (i.e., archaeological or fossil) specimens archaeological, biological, and climatic research, offering rich sampling (Surge and Barrett, 2012; Wang et al., 2012). opportunities related to archaeological shell middens, peatlands, and Other studies examined stable isotope ratios in mollusc shells to marine sediments to develop paleoclimate studies (Orquera and Piana, understand life history and growth patterns (Jones, 1983; Jones et al., 2009; Vila et al., 2007; Mauquoy et al., 2004; Borromei et al., 2010.) 1984, 1989; Jones and Quitmyer, 1996; Goodwin et al., 2001). In Gordillo et al. (2015) reports monthly mean SST values from Ushuaia particular, studies of patelloid limpets have noted prominent growth Bay over a period of approximately 50 years ranging from approxi- lines that occur annually, possibly due to growth temperature stress in mately 4–9 °C (estimated from their Fig. 5; standard deviations not winter and/or summer, reproductive stress, or changes in food supply provided). Graniero et al. (2016) reports average salinity of (Fenger et al., 2007; Surge et al., 2013; Ambrose Jr. et al., 2016). As 30.6 ± 0.8 psu (practical salinity units) at the study site, with little such, prominent growth lines can help to contextualize the growth seasonal variation. Precipitation averages 570 mm per year, with more patterns and lifespans of a shelled animal, provided that the timing of precipitation generally occurring in winter than in summer (Gordillo prominent growth formation is understood. et al., 1992). Here, we interpret records of life history and seasonal variation in Waters of the Beagle Channel are influenced by the Antarctic growth temperature preserved in modern specimens of two high- Circumpolar Current (ACC), the strength of which is determined by the southerly latitude limpets, Nacella deaurata (Gmelin, 1791) and N. strength of the Southern Hemisphere Westerly Winds (SHWW). The magellanica (Gmelin, 1791). Through the analysis of oxygen and stable primary cause of climate variation in the study area is the Southern 18 13 carbon isotope ratios (δ Oshell and δ Cshell, respectively), we test the Annular Mode (SAM; Limpasuvan and Hartmann, 1999), also known as hypotheses that: 1) these species form their shells in isotopic equili- the Antarctic Oscillation (AAO, Gong and Wang, 1999). The SAM index brium with ambient water; 2) their shells record seasonal variation in is defined as the difference in mean sea-level pressure (MSLP) between SST; and 3) prominent growth lines in their shells form annually. Our 40°S and 65°S latitude (Gong and Wang, 1999). During positive phases results have implications for an important new and abundant resource of SAM, MSLP is higher at mid latitudes than at high latitudes, causing for studying human behavior, past climate change, and ultimately the SHWW to contract toward Antarctica. During negative phases of human-climate interactions from high southerly latitudes in South SAM, MSLP is higher at high latitudes than at mid latitudes, causing the America (Álvarez et al., 2018). SHWW to expand toward the southern edges of South America, Africa, and Australia. In southern South America, positive phases of SAM are associated with warmer, drier conditions, while negative phases coin- 2. Materials and methods cide with colder and wetter conditions (Thompson and Solomon, 2002; Sen Gupta and England, 2006; Gillett et al., 2006; Dätwyler et al., 2.1. Ecology of Nacella deaurata and N. magellanica 2018). SAM oscillates between positive and negative phases over per-