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Geo-Mar Lett (2008) 28:309–325 319

Table 8 Mazzaforno isotope data in relation to temperature (°C) data from the locality
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Month SST at the Edge δ O SHELL Calculated Difference Edge δ O SHELL Calculated Difference between
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time of value (best fit) δ O SHELL between SST value (worst fit) δ O SHELL SST and δ O SHELL
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collection (‰ VPDB) temperature and δ O SHELL (‰ VPDB) temperature temperature (worst
(°C) (best fit) (°C) temperature (worst fit) (°C) fit)
(best fit)
August 2004 28.1 −0.02 25.0 +3.1 +0.18 24.2 +3.9
September 2004 27.9 +0.04 24.8 +3.1 +0.73 21.8 +6.1
October 2004 24.7 +0.73 21.8 +2.9 +0.73 21.8 +2.9
November 2004 21.6 +0.86 21.2 +0.4 ns +1.21 19.7 +1.9
December 2004 18.5 +1.79 17.2 +1.3 +1.98 16.3 +2.2
January 2005 15.4 +2.45 14.3 +1.1 +2.53 14.0 +1.4
February 2005 12.9 +2.72 13.1 −0.2 ns +2.53 13.9 −1.0
March 2005 12.8 +2.97 12.0 +0.8 ns +2.59 13.7 −0.9
April 2005 16.0 +2.40 14.5 +1.5 +2.95 12.1 +3.9
May 2005 18.7 +1.47 18.6 +0.1 ns +1.84 17.0 +1.7
June 2005 23.6 +0.59 22.4 +1.2 +0.98 20.7 +2.9
July 2005 26.9 +0.09 24.5 +2.4 +0.29 23.2 +3.2

See text for explanation of ‘best fit’ and ‘worst fit’
ns Not statistically significant)

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larly closely, the Palermo mean monthly SSTs (r =0.971). isotope values from smaller (younger) shells reflect ambient
On average, for both larger and smaller shells, there are temperatures best through the winter and spring months,
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larger discrepancies between δ O SHELL temperatures and while those from larger shells reflect SSTs best in the
SSTs measured at the locality than with mean monthly autumn/fall to mid-winter months (Table 10).
SSTs at Palermo (Table 10). Compared with mean monthly
Palermo SSTs, isotope temperatures from smaller shells Isotope data from a marked individual: Cala Grande
show the greatest discrepancies in the months from July to
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October, while results from larger shells are more variable The pattern of δ O values (Fig. 8) shows that a whole year
(Table 10). Isotope temperatures from both larger and of temperature fluctuations is represented, confirming that
smaller shells show the least discrepancy with recorded the two growth lines on the shell demarcate 1 year of shell
SSTs in February, which is the coldest month. In general, growth. Each line corresponds to a period of growth

Table 9 Mazzaforno isotope data in relation to temperature (°C) data from the marine station in the Gulf of Palermo
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Month Mean SST Edge δ O SHELL Calculated Difference Edge δ O SHELL Calculated Difference
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at the Palermo value (best fit) δ O SHELL between SST value (worst fit) δ O SHELL between SST
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measuring (‰ VPDB) temperature and δ O SHELL (‰ VPDB) temperature and δ O SHELL
station (°C) (best fit) (°C) temperature (worst fit) temperature
(best fit) (°C) (worst fit)
August 2004 27.2 −0.02 25.0 +2.2 +0.18 24.2 +3.0
September 2004 25.7 +0.04 24.8 +0.9 +0.73 21.8 +3.9
October 2004 23.6 +0.73 21.8 +1.8 +0.73 21.8 +1.8
November 2004 20.8 +0.97 20.7 +0.1 ns +1.21 19.7 +1.1
December 2004 17.5 +1.79 17.2 +0.3 ns +1.98 16.3 +1.2
January 2005 15.0 +2.45 14.3 +0.7 ns +2.53 14.0 +1.0
February 2005 13.7 +2.62 13.6 +0.1 ns +2.72 13.1 +0.6 ns
March 2005 14.2 +2.59 13.7 +0.5 ns +2.97 12.0 +2.2
April 2005 15.6 +2.40 14.5 +1.1 +2.95 12.1 +3.5
May 2005 19.0 +1.47 18.6 +0.4 ns +1.84 17.0 +2.0
June 2005 23.2 +0.59 22.4 +0.8 ns +0.98 20.7 +2.5
July 2005 26.5 +0.09 24.5 +2.0 +0.29 23.7 +2.8
See text for explanation of ‘best fit’ and ‘worst fit’
ns Not statistically significant