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Global and Planetary Change 40 (2004) 195–200

The Mediterranean coral Cladocora caespitosa: a proxy for

past climate fluctuations?

A. Peiranoa,*, C. Morrib, C.N. Bianchia, J. Aguirrec, F. Antoniolid,G. Calzettae, L. Carobeneb, G. Mastronuzzif, P. Orrug

aENEA, Centro Ricerche Ambiente Marino, PO Box 224, 19100 La Spezia, ItalybDipTeRis, Universita di Genova, Corso Europa 26, 16132 Genoa, Italy

cDep.to Estratigrafıa y Paleontologıa, Universidad de Granada, 18071 Granada, SpaindENEA, Dipartimento Ambiente, Via Anguillarese 301, S.Maria di Galeria, 00060 Rome, Italy

eStudio Eco-X, Via del Corso, 19038 Sarzana, La Spezia, ItalyfDipartimento di Geologia e Geofisica, Via E. Orabona 4, 70125 Bari, Italy

gDiSTer, Universita di Cagliari, Via Trentino 51, 09127 Cagliari, Italy

Received 4 October 2001; accepted 7 May 2003

Abstract

Sclerochronology was applied to recent, Holocene and Pleistocene samples of Cladocora caespitosa. Late Pliocene samples

were recrystallised and thus unsuitable for sclerochronology. Quaternary samples showed a clear, alternating banding pattern as

in the living coral, confirming a marked seasonality of past climate. The computed mean annual growth rates ranged from 2.1 to

6.9 mm year� 1, with highest growth rates during the warmer phase (isotope stage 5e) of the first climate cycle. It is

hypothesised that the largest fossil banks of C. caespitosa grew in a coastal environment with considerable alluvial inputs and

warmer temperatures than today.

D 2003 Elsevier B.V. All rights reserved.

Keywords: Paleoclimatic reconstruction; Cladocora caespitosa; Coral; Mediterranean; Sclerochronology

1. Introduction reefs both in the eastern and western Mediterranean

Cladocora caespitosa (L.) is the main native zoox-

antellate and constructional coral of the Mediterranean

Sea, abundant both in the geological past and in recent

times. Large fossil Cladocora formations were found

as old as Late Pliocene, when this coral formed true

0921-8181/$ - see front matter D 2003 Elsevier B.V. All rights reserved.

doi:10.1016/S0921-8181(03)00110-3

* Corresponding author. Tel.: +39-187-978296; fax: +39-0187-

978273.

E-mail address: peirano@santateresa.enea.it (A. Peirano).

Sea (Aguirre and Jimenez, 1998; Dornbos and Wil-

son, 1999). Large fossils banks of C. caespitosa are

also known from the Early Pleistocene (Bernasconi et

al., 1997), from the Middle and Late Pleistocene and

from the Holocene (for a review, see Peirano et al.,

1998).

Today, C. caespitosa is a major carbonate producer

among Mediterranean organisms (Peirano et al.,

2001). It occurs on shallow bottoms (4–10 m) form-

ing ‘beds’ of numerous, distinct, hemispherical colo-

nies. From 10 m down to 40 m of water depth, the

A. Peirano et al. / Global and Planetary Change 40 (2004) 195–200196

coral becomes more rare. But, where present, it can

form build-ups rising up to 1 m above the surrounding

seafloor and covers several square metres in surface

area.

Recent C. caespitosa growth has been studied by

sclerochronology, i.e., the study of seasonal growth

marks in the skeleton. X-radiographs of these skel-

etons show a clear banding pattern, indicating that the

coral deposits two bands per year: a high-density band

during the cold and rainy winter season (November–

March) and a low-density band in the warm and dry

summer season (July–September). No differences in

banding were found between colonies collected from

shallow and those from deeper water. Timing of band

formation proved to be correlated with monthly sea

temperature and irradiance levels (Peirano et al.,

1999).

Sclerochronology has been largely used in the

tropics to assess the response of corals to environ-

mental changes and to provide a proxy for seawater

temperature of past centuries (Hudson, 1981; Lough

and Barnes, 1997). Here, we present preliminary data

on the sclerochronology of fossil C. caespitosa. The

Fig. 1. Positive X-ray images of skeletons (corallites) of C. caespitosa fr

bands are high-density zones (HD) and white bands are low-density zone

present work aims to study the presence and preser-

vation of the annual banding pattern in fossil Clado-

cora skeletons. In case of positive results, we want to

compare annual growth rates of recent and fossil

samples with climate parameters.

2. Material and methods

Recent coral skeletons were samples isolated from

the Ligurian Sea (NLS). Fossil samples come from

Tuscany (PV), Sardinia (C1 and C2), Calabria

(LB95), Apulia (TaSV, TaSR and TaST) and SE Spain

(AL).

NLS samples were collected in 1994–1997 in the

Ligurian Sea at 4–30 m of depth from Bocca di

Magra to Bonassola (La Spezia) (Peirano et al.,

1999). Sclerochronology allowed measuring annual

growth rates of 114 colonies back to 1930.

All the Holocene and Pleistocene samples were

single colonies; they were dated by the Th/U method

and attributed to ancient shorelines and isotopic stages

following Hearty et al. (1986).

om Holocene (NLS) and Pleistocene (TAST, LB95) samples. Dark

s (LD). Reference bar is 5 mm.

Table 1

Annual mean growth rates and their standard deviations (S.D.)

computed from sclerochronological analysis of Quaternary samples,

in chronological order of isotopic stages of Hearty et al. (1986)

Sample Age

(ky)

Isotopic

stage

Number of

measurements

Mean

growth rates

(mm year� 1)

S.D.

C2 7F 1 1 27 4.11 1.25

TaSV 104F 2 5c 47 2.13 0.89

TaPR 108F 1.5 5c 81 3.62 1.78

TaST 125F 8 5e 170 6.94 2.14

PV 129F 15 5e 7 6.25 2.96

C1 149F 10 5e 4 2.57 0.73

LB95 329 + 196

� 64

9 98 2.55 0.80

A. Peirano et al. / Global and Planetary Change 40 (2004) 195–200 197

Samples PV from Piana della Versilia (Massaciuc-

coli lake, Pisa) were extracted from a lagunal silt-clay

layer in a borehole at 68.8 m of depth. They were

dated 129.2F 15 ky BP.

Sample C1 was extracted from fossil deposits of

Iletta Island at the center of S. Gilla Lagoon (Cagliari,

Sardinia), where C. caespitosa is abundant and em-

bedded in a littoral sandy matrix. It was dated

149F 10 ky BP, and attributed to the isotopic stage

5e (Euthyrrenian). Sample C2 was collected from the

bay-mouth bar, named La Playa that locks the lagoon.

It was dated 7F 1 ky BP corresponding to the

Holocene climatic optimum. Its living depth was

probably 0.5–1 m (Ulzega and Hearty, 1986).

Samples LB95, from Grotta del Prete (S. Nicola

di Arcella, Scalea) were isolated from a Cladocora-

Fig. 2. Mean growth rates (E) and standard deviations (bars) of recent (N

Shackleton’s (2000) d18 Oatm isotopic curve; in brackets, isotopic stages.

bearing biocalcarenite dated 329 + 196� 64 ky BP.

They were referred to the sea level highstand 9.

Living depth of coral banks was V 4.5 m (Car-

obene et al., 1986; Carobene and Dai Pra, 1991).

Samples from Apulia were collected near Taranto

and extracted from a sandy matrix. TaSV (S. Vito

Cape; 104F 2 ky BP) and TaPR (Ponte Romano;

108F 1.5 ky BP) were referred to isotopic stage 5c,

TaST (S. Teresiola; 125F 8 ky BP) to stage 5e.

The most ancient sample analysed (AL) was at-

tributed to Late Pliocene on the basis of planktonic

foraminifer assemblages (Aguirre and Jimenez, 1998;

Aguirre and Sanchez-Almazo, 1998). It came from the

Almerıa-Nıjar basin (Spain) where Cladocora formed

banks covering a surface area of up to 3000 m2.

Skeletons were recrystallised and embedded in a

cemented silty clay. The corals probably lived at

20–30 m of water depth.

From each sample, corallites were separated,

cleared of epibionts and immersed in a 1:1 peroxide

solution to remove organic remains and then dried at

70 jC. To measure growth rates the corallites were X-

rayed. Positive images from X-ray films were analysed

with the public domain NIH-Image programme for

Macintosh. According to Peirano et al. (1999), mean

growth rates were computed averaging the measure-

ments of distances between two successive HD density

peaks ( = 1 year of growth). Differences between mean

growth rates were analysed through one-way ANOVA.

Homoscedasticity of variances was achieved through

logarithmic transformations of variables.

LS) and fossil samples of C. caespitosa. Continuous line indicates

A. Peirano et al. / Global and Planetary Change 40 (2004) 195–200198

3. Results

All the skeletons from the Quaternary showed a

clear banding pattern (Fig. 1). Corallites of the Plio-

cene from Spain (AL), recrystallised, did not show

growth bands. Mean annual growth rates of Quater-

nary samples ranged from 2.1 to 6.9 mm year� 1

(Table 1).

Notwithstanding the low number of fossil corals

analysed and the fact that samples came only from one

colony per site, mean growth rates were in good

accordance with Shackleton’s (2000) isotopic recon-

struction of climate cycles (Fig. 2). In particular,

samples C2, TaPR, TaSV and PV showed a positive

trend of mean growth rates that is consistent with

warm phases of the first climatic cycle. On the

contrary, C1 and LB95 did not fit with previous

samples and exhibited lower growth rates than

expected. Holocene (C2) and recent (NLS) samples

were consistent with the temperature profiles from the

Greenland ice sheet (Dahl-Jensen et al., 1998). An-

nual mean growth rates (2.5F 0.91 mm year� 1) of

recent C. caespitosa (NLS) were significantly differ-

ent from TaPR, TaST, C2 and PV (Table 1). Highest

growth rates were found in TaST (6.94F 2.14 mm

year� 1).

Fig. 3. Interannual variations of mean growth rates of the coral C. caespitos

Mediterranean) since 1866 (lower graph). Curves are the multi-annual tre

To test the possible relationship of past coral

growth with climate, growth rates of recent C. caes-

pitosa collected in the Ligurian Sea were compared to

the 150-year record of air temperature (ISTAT, 1986–

2000), which is strongly and positively correlated

with seawater temperature (Astraldi et al., 1995).

Notwithstanding the variability in the amplitude of

oscillations, due to the differences in the numbers of

corals analysed per year, the growth of C. caespitosa

was in good agreement with climatic data (Fig. 3).

Two synchronous, parallel cycles were recognised: a

sinusoidal long-term cycle of 90 years, and a shorter

cycle of about 7 years. The overall, positive trend is

in agreement with the global warming, and the

warmer climatic phase in the 1930s is consistent with

the temperature profiles from Greenland ice sheet

GRIP (Dahl-Jensen et al., 1998). The five-order

polynomial regression indicated a coral growth in-

crease of 0.7–1.6 mm year� 1 in relation to a rise in

air temperature of 0.7–1 jC. If this relationship is

applied to the fossil coral samples, then the TaST

corals should have grown in a climatic phase charac-

terised by a mean annual air temperature 3.2 jChigher than today. This is in the range of temperatures

reported by Cita et al. (1977) and Zazo (1999) for past

Mediterranean climates.

a (upper graph) compared to air temperature records of Liguria (NW

nds generated by a five-order polynomial regression.

A. Peirano et al. / Global and Planetary Change 40 (2004) 195–200 199

4. Discussion and conclusions

An identical banding pattern in fossil and recent C.

caespitosa indicates that also the past Mediterranean

climate was characterised by a marked seasonality,

with cold winters and warm summers. However, fossil

corals formed larger and higher banks than those of

today, hence the environmental conditions of past

Mediterranean Sea, in terms of both temperature and

water quality should not have been exactly the same.

The descriptions of fossil coral banks, their strati-

graphic sequences and their sedimentological features

often report their presence in sites exposed to fine

sediments and alluvial inputs (Aguirre, 1998). Fornos

et al. (1996) suggested that C. caespitosa banks

developed mainly during maximum flooding condi-

tions at the end of transgressive phases, and massive

input of sediments is supported by Peizhen et al.

(2001) who showed that in the Pliocene–Pleistocene

erosional processes were the highest since 80 Myr.

Such a turbid environment is consistent with the

observation of recent coral ‘beds’ and banks, often

found in coastal waters exposed to important terres-

trial inputs. Here C. caespitosa competes successfully

with soft, frondose algae thanks to its capability of

combining autotrophy and heterotrophy (Peirano et

al., 1998, 1999). In the Pliocene and Early Pleisto-

cene, the presence of extensive ‘beds’ of Ostrea spp.

(Bernasconi et al., 1997; Aguirre and Jimenez, 1998;

Dornbos and Wilson, 1999), forming the basement of

or being intercalated in coral banks, confirms the

assumption of turbid waters, where suspension and

filter feeding organisms were favoured.

Late Pleistocene C. caespitosa banks differed from

older banks in the presence of Strombus bubonius,

which characterised the isotopic stage 5e (our samples

C1, TaST). This gastropod, a Senegalese species, is an

indicator of a warmer climate phase. This coincides

with higher C. caespitosa growth rates (Fig. 1).

In conclusion, we can hypothesise that major fossil

reefs of C. caespitosa grew in coastal waters charac-

terised by a marked seasonality, with alluvial inputs of

fine sediments, higher turbidity and higher tempera-

ture than today. Such results, although preliminary,

suggest that C. caespitosa could be a reference species

for future work on changing Mediterranean climate,

allowing the study of climate cycles at short (annual),

medium (decadal) and long (millennia) terms.

Acknowledgements

Thanks to J. Geister (Bern) and to Kl. Oekentorp

(Muenster) for the critical reading of the manuscript.

This work has been done within the framework of the

research projects SINAPSI and Ambiente Mediterra-

neo (Accordo di programma MURST-CNR ‘‘Ecosis-

temi marini’’).

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