Isotopic evidence for climate change during the Vandal Minimum from Ariopsis felis otoliths and Mercenaria campechiensis shells, southwest Florida, USA

Abstract

Archaeological evidence from coastal southwest Florida suggests this region and its local inhabitants (the Calusa) were affected by drought and cooling during the Vandal Minimum climate episode (ad 500–800). To test this hypothesis, we reconstructed seasonal-scale climate conditions using stable oxygen and carbon isotope ratios (δ18O and δ13C) preserved in Ariopsis felis otoliths and Mercenaria campechiensis shells. Comparing δ18O records from both species distinguishes between cool versus warm and wet versus dry conditions. δ18O values from four otoliths indicate cooling of winter temperatures occurred in the early Vandal Minimum (ad 500–600) and late half of the middle Vandal Minimum (ad 650–700). Persistent dry summers punctuated by occasional years with wet summers throughout the Vandal Minimum were detected from δ18O values of eight archaeological shells. Our climate reconstructions are in good agreement with archaeological observations and with the cool and dry conditions documented in Europe.

Do fish remains provide reliable palaeoenvironmental records? An examination of the effects of cooking on the morphology and chemistry of fish otoliths, vertebrae and scales

“…Chemical and isotopic analyses of archaeological fish remains are increasingly used in palaeoenvironmental studies, drawing heavily on methods developed in modern fisheries science (e.g., Disspain et al 2011;Disspain et al 2012;Long et al 2014;Wang et al 2011Wang et al , 2013. Numerous researchers have examined how ambient environmental variables influence the chemistry of calcified structures, specifically otoliths because of their unique attributes (see Disspain et al 2016;Elsdon et al 2008), using such relations to interpret environmental histories of modern fish.…”

Marine Reservoir Effects in Eastern Oyster (Crassostrea Virginica) from Southwestern Florida, USA

“…These yielded a weighted average and weighted uncertainty for ΔR of -15 ± 42 yr (T = 1.70, χ 2 :05 7:815). We consider this to be the current best estimate for ΔR for the pre-Columbian Turner River archaeological site, at least during the 7th century cal AD, which coincides with the Vandal Minimum climate episode, an abrupt onset of cooler, drier, or even drought-like conditions in Southwest Florida (Wang et al 2011(Wang et al , 2013 and elsewhere (Arjava 2005). We do not know, or purport to know, whether this value is generalizable to the greater region or beyond this time-period.…”

ClamR: A statistical evaluation of isotopic and temperature records in sclerochronologic studies

“…Variations in seasonal/annual growth rate can result in time averaging and, hence, truncated records. For example, time averaging of isotopic records has been observed in shells of the European limpet, Patella vulgata, (Fenger et al 2007) and otoliths of the hardhead catfish, Ariopsis felis (Wang, et al, 2011) where periods of slow growth during seasons exceeding optimal growth temperature have a lower sampling density (i.e., fewer data points) relative to periods of fast growth. Goodwin et al (2003) discuss the problem of time averaging due to low sampling resolution or slow growth rate.…”

“…scales. Therefore, many paleoclimate and paleoenvironmental reconstructions use biogenic hard parts, and in particular mollusc shells, to extract information on changes in seasonal temperature, precipitation, and primary productivity/upwelling (e.g., Jones et al, 2009;Schöne et al, 2011;Wang et al, 2011;Surge and Barrett, 2012;Wanamaker et al, 2012;Schöne and Gillikin, 2013 and papers therein; Wang et al, 2013).…”