Page 1 - Shell_growth_2008

Geo-Mar Lett (2008) 28:309–325
DOI 10.1007/s00367-008-0107-5

ORIGINAL

Shell growth and oxygen isotopes in the topshell Osilinus

turbinatus: resolving past inshore sea surface temperatures

Marcello A. Mannino & Kenneth D. Thomas &
Melanie J. Leng & Hilary J. Sloane

Received: 30 October 2007 /Accepted: 27 February 2008 / Published online: 3 July 2008
# Springer-Verlag 2008

Abstract Shells of the rocky shore intertidal gastropod through the year. In all the datasets, surface seawater
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Osilinus turbinatus (von Born), often abundant in archae- temperatures (SSTs) calculated from δ O SHELL mostly
ological deposits in the Mediterranean region, are a underestimate measured SSTs, offsets being generally
potential source of data on palaeotemperature, palaeosea- greater in summer. Minimum annual offsets range from
sonality and archaeological seasonality. To evaluate this 0.0°C to 0.7°C and maximum annual offsets from 3.1°C to
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species as a climate archive, investigations of annual 8.7°C. δ O SHELL values fail to record temperatures higher
patterns of shell growth and of monthly variations in than 25°C. Careful selection of shells to be analysed can
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oxygen isotopes in shell carbonates were made on different reduce offsets between δ O SHELL temperature estimates
populations in NW Sicily. Mark-recapture experiments at and measured SSTs for many parts of the year, except the
San Vito lo Capo and Mazzaforno show that O. turbinatus hottest. Allowing for this, shells of O. turbinatus offer good
grows almost continuously throughout the year but at potential as climate archives and for archaeological studies
different rates in different seasons. Around 75% of the of seasonal patterns of human foraging for shellfish.
yearly shell growth occurs in the autumn and winter. On
average, larger/older shells produce narrower annual
growth increments than smaller/younger ones. Conspicuous Introduction
growth lines in larger/older shells show that growth stops
during the hottest part of the summer. Oxygen isotope Oxygen isotopes in the calcareous skeletons of inverte-
analyses on monthly collected shells of O. turbinatus from brates are frequently used for palaeoenvironmental recon-
three shores (Cala Grande, Monte Cofano and Mazzaforno) struction (e.g. Barrera and Tevesz 1990; Wefer and Berger
show that the isotope values record temperature variations 1991). Growth increments in shells of bivalve molluscs are
often correlated with tidal cycles (Evans 1972) or daylight
: cycles (Clark 2005), and offer good potential for environ-
M. A. Mannino (*) K. D. Thomas mental resolution from sequences of oxygen isotope data in
Institute of Archaeology, University College London,
31-34 Gordon Square, both long- and short-lived species (Schöne 2003; Goodwin
London WC1H 0PY, UK et al. 2003;Schöneetal. 2005). Sclerochronological
e-mail: m.mannino@ucl.ac.uk analyses of the rocky shore intertidal gastropods Littorina
: littorea (Burman and Schmitz 2005)and Patella vulgata
M. J. Leng H. J. Sloane
NERC Isotope Geosciences Laboratory, (Fenger et al. 2007) show their potential to encode
British Geological Survey, environmental signals in their calcitic shells. Oxygen
Keyworth NG12 5GG, UK isotopes in aragonitic gastropod shells have also been used
in a variety of ways: Gibbula cineraria is a useful
M. J. Leng
School of Geography, University of Nottingham, environmental archive (Schöne et al. 2007), Osilinus
Nottingham NG7 2RD, UK lineatus from modern shores and archaeological sites