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Climex Maps - explanatory notes
The outermost layers (active serpulids) from extracted from colonies sampled at different
different colonies sampled in different caves and depths, and permits the assumption that
at different depths have a similar mean 18O serpulids long-term records of mean annual
value (2.1‰). temperature changes of near-surface sea water
Polychaete serpulids are believed to secrete averaged over 200 years.
calcium carbonate close to 18O equilibrium with Information on serpulid growth rates is available
sea water and do not show metabolic effects on for harbour and brackish-water species (Bianchi
oxygen isotope fractionation (Videtich, 1986). and Morri, 1996), for which maximum tube
The 18O value of serpulid tube calcite, growth occurs in summer. Faster growth rates
therefore, should be a function of the 18O value during warm seasons were also documented for
of sea water and of the ambient temperature aragonite serpulids from a submarine cave off
(e.g. O’Neill et al., 1969). Any discussion about the coast of Belize (Videtich, 1986). Serpulids of
variables which should be accounted for when tropical origin, such as Serpula massiliensis put
interpreting the 18O signal of Tyrrhenian most of their energy into reproduction in
serpulids are in Antonioli et al. 2001. autumn and winter. They spend their energies
to grow in summer, following their biological
Sea Surface Temperature reconstruction rhythm. Their annual growth rate is considered,
If we assume that Tyrrhenian sea water 18O however, constant as for other Mediterranean
composition mainly reflects the SST variation, invertebrates, and independent from
time changes in 18O of serpulid tube calcite temperature. So we infer that serpulids
could reflect SST trends (cooling vs. warming) commonly grew in summer throughout the
averaged over about 200 years, which is the Holocene, and that their growth rate was
mean time span encompassed by a 2 mm2 season-dependent, not temperature dependent,
sample. and that their calcite 18O signal records
The measured present-day 18O value of sea summer sea surface temperature trends within
water both within and outside the submerged and outside the caves.
caves is constant, and is 0.9‰ (SMOW). We exclude the possibility that 18O changes
However, the SST measured within this reflect the influence of karstic freshwater on the
submerged caves ranges from 17° in winter to basis of the observation that Serpula
24°C in summer, and the SST outside the caves massiliensis are not present in caves where
ranges from 14° in winter to 25° in summer. there is freshwater percolation (Belloni and
Cave waters are therefore less subjected to Bianchi 1982).
seasonal temperature variations, and can be By application of Epstein et al. (1953) equation
considered as representative of average mean we calculated the SST-near-shore values for
annual temperature. In the submerged caves at OPT map in these three sites of the Tyrrhenian
both Palinuro, Argentarola and Marettimo we did Sea, as summarized in Tab. 1.
not record the presence of a thermocline. This
physical characteristic of the coastal caves
makes it possible to compare the 18O signals
Location Age d 18O SST (°C)
(ky cal BP) (permil PDB)
Argentarola Is. 7.81±1.77 14.5±1.6
Palinuro Cape 7.36±1.19 1.37±0.39 12.9±1.2
Marettimo Is. 8.00±1.64 1.76±0.30 16.9±3.0
0.80±0.72
Tab. 1. d 18O and derived SST data shown in the HCO map.
