Original scientific article	UDK 574.58:593.6(262.32)
Received: 2014-03-28
MACROFAUNA ASSOCIATED WITH A BANK OF CLADOCORA CAESPITOSA (ANTHOZOA, SCLERACTINIA) IN THE GULF OF TRIESTE (NORTHERN ADRIATIC)
Valentina PITACCO, Martina ORLANDO-BONACA, Borut MAVRIC & Lovrenc LIPEJ
Marine Biology Station, National Institute of Biology, SI-6330 Piran, Fornace 41, Slovenia
E-mail: pitacco@mbss.org
ABSTRACT
The Mediterranean stony coral Cladocora caespitosa (Linnaeus, 1767) is a native colonial, zooxanthellate, shallow-water coral, particularly sensitive to global changes and anthropogenic activities. Due to its shape and size, it is able to host a diversified faunal assemblage, which is still relatively unknown. A recently discovered bank of C. caespitosa, discovered close to Cape Ronek (Gulf of Trieste, Slovenia), was investigated in November 2010. Altogether 121 invertebrate taxa, belonging to 9 different phyla were found. Taxa composition in colonies differed markedly from the surrounding areas within the bank. Only 5 taxa (4 % of the total) were found both within and without C. caespitosa colonies. Our results confirm the role of C. caespitosa as a habitat builder and indicate the importance of the studied bank for biodiversity.
Key words: Cladocora caespitosa, bioconstruction, macroinvertebrates, circalittoral, Northern Adriatic
MACROFAUNA ASSOCIATA AD UN BANCO DI CLADOCORA CAESPITOSA (ANTHOZOA, SCLERACTINIA) NEL GOLFO DI TRIESTE (ADRIATICO SETTENTRIONALE)
SINTESI
La madrepora a cuscino (Cladocora caespitosa, Linneus, 1767) è un corallo madreporario di acque poco profonde, sensibile ai cambiamenti climatici ed alle attività antropiche. Grazie alla sua struttura e alle dimensioni, questo madreporario è in grado di ospitare una comunità faunistica molto diversificata. Un banco di C. caespitosa, scoperto recentemente vicino a Capo Ronco (Golfo di Trieste, Slovenia), è stato studiato nel novembre 2010. In totale sono stati trovati 121 taxa di invertebrati, appartenenti a 9 diversi phyla. La composizione faunistica all'interno delle colonie differiva notevolmente da quella della zona circostante sul banco. Solo 5 taxa (4 % del totale) sono stati trovati sia all'interno che nei pressi delle colonie. I nostri risultati confermano il ruolo di C. caespitosa come biocostruttore e pongono l'accento sull'importanza del banco oggetto di studio per la biodiversità.
Parole chiave: Cladocora caespitosa, biocostruzioni, macroinvertebrati, circalitorale, Adriatico settentrionale
INTRODUCTION
The Mediterranean stony coral Cladocora caespitosa (Linnaeus, 1767) is the only native colonial and obligate zooxanthellate coral of the Mediterranean Sea (Zibrow-ius, 1980; Peirano et al., 1999). It occurs throughout the Mediterranean on rocky and sandy bottoms from shallow waters to those at more than 30 m depth (Zibrowius, 1980). However, in the Adriatic Sea it is rarely found below 30 m (Kruzic et al., 2008). C. caespitosa is one of the major carbonate producers in the Mediterranean Sea (Peirano et al., 2001) and forms hemisperical, bushlike colonies. Due to its shape and size, it is physiologically and morphologically similar to the typical tropical reef-building corals (Zibrowius, 1982; Schuhmacher & Zibrowius 1985; Peirano et al. 1994; Kruzic & Pozar-Domac, 2003) and consequently, is able to host a diversified faunal assemblage (Koukouras et al., 1998). Much has been reported about the fauna associated with tropical corals (e.g., Cantera et al., 2003; Idjadi & Edmunds, 2006; Martins Garcia et al., 2008) but very little is known about the macrofauna associated with colonies of C. caespitosa. Species associated with this Scleractin-ian coral have been reported from different sites in the Adriatic (Sciscioli & Nuzzaci, 1970; Zavodnik, 1976; Schiller, 1993), Ionian (Lumare, 1965) and Aegean Seas (Arvanitidis & Koukouras, 1994; Koukouras et al., 1998; Antoniadou & Chintiroglou, 2010). Nevertheless, most of these reports focus on specific taxonomic groups, namely polychaetes (Sciscioli & Nuzzaci, 1970; Arvanitidis & Koukouras, 1994) and echinoderms (Zavodnik, 1976). The most comprehensive study of macrofaunal assemblages associated with C. caespitosa was carried out by Koukouras et al. (1998) in the Aegean Sea.
Colonies of C. caespitosa can be solitary, can form 'beds' (numerous colonies living more or less close to each other) or 'banks' (colonies connected together in large formations) (Zibrowius, 1980; Kuhlmann et al., 1991; Schiller, 1993; Morri et al., 1994; Peirano et al., 1994). Solitary colonies can be locally abundant (Zibrowius, 1980), beds are known from several sites, such as the western Mediterranean (Majorca, Port-Cros and Villefrance), northern Adriatic and Ionian coasts (Peirano et al., 1994), while banks are uncommon and have been reported only in the Ligurian Sea (Morri et al., 1994), off the Tunisian coast (Zibrowius, 1980) and in the Adriatic (Kruzic & Pozar-Domac, 2003) and Aegean Seas (Kuhlmann, 1996).
The circalittoral belt in the Gulf of Trieste is mostly composed of the biocoenosis of the muddy detritic bottom, with a patch of coastal detritic biocoenosis in the Bay of Piran (Lipej et. al., 2006). A bank of C. caespitosa was recently discovered close to Cape Ronek in Slovenian waters (Lipej et al., 2006). The bank was investigated according to Marine Strategy Framework Directive (MSFD, 2008/56/EC) requirements. During the first survey of this bank, performed using SCUBA diving techniques,
coralline algae were sampled. Seven coralline algal species (three of them new for Slovenia) as well as fossil rho-doliths were found (Falace et al., 2011). Given the important role of C. caespitosa as bioconstructor, the aim of the present work was to investigate the invertebrate fauna associated with this almost unknown biogenic formation in order to estimate to what extent this coral contributes to local biodiversity. Moreover, since some authors reported that the Mediterranean stony coral is undergoing a rapid decrease in both size and spatial distribution in the Mediterranean Sea (Morri et al., 2001; Rodolfo-Metalpa et al., 2005), it is of great importance to study the biological and ecological aspects of this bank and to consider possible measures of protection as well.
MATERIAL AND METHODS
Study area and sampling site
The Gulf of Trieste is a shallow semi-enclosed em-bayment located in the northernmost part of the Adriatic Sea. It is characterized by the lowest winter temperatures in the Mediterranean Sea, which can fall below 10 °C in winter (Boicourt et al., 1999). Salinity is about 37 on average, but is influenced near the coast by fresh water input from rivers, mainly the Isonzo River (Mozetic et al., 1998). During the summer, a typical thermal stratification of the water column develops due to surface heating and fresh water inflow (Boicourt et al., 1999). In winter, the water column is characterized by consider-
Fig. 1: Map of the study area with sampling sites. Sl. 1: Obravnavano območje in mesta vzorčenja.
able vertical homogeneity due to autumnal cooling and wind mixing (Mozetič et al., 1998).
The sampling site (Fig. 1) is located off the coast of Strunjan (Cape Ronek), where a biogenic bank of C. caespitosa is present. This bank extends on a surface of about 200 x 100 m, at a depth range between 12.4 and 21 m and is a few meters higher than the surrounding bottom. The bank (Fig. 2) presents the highest density of C. caespitosa colonies ever recorded in Slovenian coastal water: 6.52 colonies m-2 on average (unpubl. data). On this bank colonies are surrounded by an area made of dead corallites and, to a lesser extent, of coralline algae (mainly rhodoliths of Lithothamnion spp.) (Fig. 3).
Fieldwork and laboratory work
Sampling was performed in November 2010, dredging the selected area at a constant speed of 1 knot for 5 minutes. The dredge is considered to be more appropriate than grabs and cores for the estimation of the densities of small benthic species (Pérès & Picard, 1964; Cas-telli et al., 2003). The biogenic bank was investigated on two levels in order to better characterize the benthic community associated with this formation. The first level comprises the area that surrounds the colonies of C. caespitosa. The largest, easily identifiable animals were identified on the boat immediately after the sampling and were then released. The smallest animals were fixed in ethanol (70 %) and classified later in the laboratory. The second level addresses the infauna living inside colonies of C. caespitosa. Thirty colonies of C. caespitosa were chosen. Each colony was weighed and measured (minimum axis width and maximum axis length), and the percentage of the number of living corallites was visually estimated. The bottom surface covered by
Fig. 2: The biogenic bank of Cape Ronek with colonies of C. caespitosa and the bottom made of dead corallites. (Photo: B. Mavric)
Sl. 2: Biogena formacija pred rtom Ronek s kolonijami sredozemske kamene korale (C. caespitosa) in dno, ki ga sestavljajo mrtvi koraliti. (Foto: B. Mavric)
those colonies was calculated from colony axes. Afterwards the colonies were preserved in 70 % ethanol. In the laboratory they were broken apart completely and sieved through a 1 mm mesh. Each corallite was broken and invertebrates living inside were carefully collected with fine pipettes and tweezers. Invertebrates were then sorted, counted and identified according to the relevant literature: Tebble (1966), Ghisotti & Sabelli (1970), Parenzan (19701976), Torelli (1982) and Cossignani et al. (1992) for molluscs; Fauvel (1923, 1927) and Bianchi (1981) for polychetes; Naylor (1972), Ruffo (19821993), Harrison & Ellis (1991), Falciai & Minervini (1992) and Hayward & Ryland (1995) for crustaceans, Occhipinti Ambrogi (1981) for bryozoans; Tursi (1980) for tunicates and Sara (1972) for sponges. The nomenclature follows WoRMS (WoRMS, 2013). Only living invertebrates were taken into consideration and counted. Colonial species were also determined and their coverage on a surface of 20 x 20 cm was calculated, but they were excluded from indices calculations.
Each species was assigned to one of the following trophic groups: motile predators (P), ectoparasites and specialized carnivores feeding on larger animals (EC), deposit feeders feeding on organic particles contained in the sediment (DF), suspension feeders capturing seston particles with their gills or with mucous strings (SF), and grazers feeding on algae, cyanobacteria or detritus attached to algal fronds (G). Feeding guilds were assessed according to Fauchald & Jumars (1979), Bianchi (1981), Chintiroglou (1996), Solis-Weiss et al. (2004) and Rueda et al. (2009).
Moreover, each species was assigned to one of four functional groups, following the classification of Reed & Mikkelsen (1987) and Hrs-Brenko & Legac (2006): free living, motile species (FL), epilithic species, living their
Fig. 3: Colonies of C. caespitosa and other epifauna on the biogenic bank at Cape Ronek. (Photo: B. Mavric) Sl. 3: Kolonije sredozemske kamene korale (C. caespitosa) in drugih elementov epifavne na biogeni formaciji pred rtom Ronek. (Foto: B. Mavric)
Tab. 1: Minimum axis and maximum axis (cm), wet weight (kg), coverage of each colony (cm2) and proportion of living corallites per colony of C. caespitosa.
Tab. 1: Minimalna in maksimalna os (cm), mokra teža (kg), pokrovnost posamezne kolonije (cm2) in delež živih koralitov na koloniji sredozemske kamene korale.
	Max axis (width) in cm	Min axis (length) in cm	Wet weight in kg	Surface covered in cm2	% of living corallites
Average	13.1	9.3	0.60	391.3	60
SD (±	2.7	1.5	0.24	125.3	27
Max	20.0	13.0	1.10	816.8	100
Min	8.6	6.3	0.14	170.2	0
entire life attached to a substrate (EP), endolithic species, living in holes bored in hard substrates (EN) and soft bottom dwelling species (SB). Species which were known to live attached to the substrate when juveniles and to move freely when adults (Hrs-Brenko & Legac, 2006) were considered separately (FL/EP).
Eventually, ecological groups were defined mainly following Pérès (1967), De Min & Vio (1997), and Solis-Weiss et al. (2004).
Data analysis
Correlation between colonies' weight, axes, percentage of living polyps and bottom surface coverage by each colony was analyzed with Spearman's coefficients for non-parametric distributions (Spearman, 1907) using R version 2.4.0.
Number of taxa (S), number of individuals (N), Mar-galeff index of richness (d), Shannon diversity index (H'), Pielou index of equitability (J') and Simpson index of dominance (L') (Clarke & Warwick, 2001) were calculated for the macrobenthic taxa found within colonies of C. caespitosa and for those taxa found on the surrounding area within the bank. A group-average sorting classification (Cluster) analysis based on Sorensen similarity (Clarke & Warwick, 2001) was performed using invertebrates presence/absence data in order to compare Cape Ronek with other sites sampled in Slovenian marine waters using the same method in the same year for other studies related to the implementation of the MSFD. These statistical analyses were carried out using the software package Primer 6, developed by the Plymouth Marine Laboratory.
RESULTS
Description of C. caespitosa colonies
The analyzed colonies of C. caespitosa were small to medium in size with a minimum axis ranging from 6.3 to 13 cm and a maximum axis ranging from 8.6 to 20
cm (Tab. 1). The majority (71 %) had a maximum axis ranging from 10 to 15 cm.
The shape of the colonies varied from almost circular to elliptical and there was no significant correlation between the maximum and minimum axes of colonies (rs = 0.295, p = 0.113). Colony weight ranged from 0.14 to 1.1 kg (Tab. 1). Both axes were positively correlated with colony weight, but the maximum axis showed the best correlation (rs = 0.641, p < 0.001). The surface covered by each colony was correlated with colony weight (rs = 0.742, p < 0.001). The percentage of living polyps in each colony was extremely variable, ranging from colonies with all polyps alive (100 %) to totally dead colonies (0 %) (Tab. 1). This percentage was not correlated with colonies' weights (rs = 0.149, p = 0.429) nor with the surface covered by each colony (rs = 0.117, p = 0.535).
Macrofaunal community description
During the present study a total of 121 taxa belonging to 9 different phyla (Porifera, Bryozoa, Cnidaria, Si-punculida, Mollusca, Anellida, Arthropoda, Echinoder-mata and Tunicata) were found within the bank of C. caespitosa. Among the 13 colonial taxa determined, 8 were sponges and 5 were bryozoans. Within non-colonial taxa 3605 individuals were counted.
On the area within the bank that surrounds colonies of C. caespitosa, 223 individuals belonging to 26 different taxa were analyzed. Echinoderms were the most abundant phyla (70 %), followed by molluscs (22 %). Taxa richness was higher within molluscs (58 %) and echinoderms (27%) (Fig. 4).
Within the 30 colonies of C. caespitosa collected and analysed in the laboratory 89 taxa of infauna were determined (Tab. 2). About 50 % of them were polychaetes, 25 % molluscs and 16 % crustaceans (Fig. 4). Regarding taxa abundance, 3386 organisms were counted (Tab. 2). The most abundant were molluscs (50 %), followed by polychaetes (20 %) and crustaceans (7 %). Many of these specimens were juveniles.
Fig. 4: Percentage of (A) abundance and taxa richness (B) within different phyla (colonial organisms excluded) within the colonies of C. caespitosa (CC) and in the surrounding area within the bank (DB). Sl. 4: Delež abundance (A) in pestrosti taksonov (B) različnih debel (brez kolonijskih organizmov) znotraj kolonij kamene korale (CC) in na okoliškem dnu znotraj biogene formacije (DB).
Only 5 taxa (4 % of the total) were found in both micro-habitats (within and without C. caespitosa colonies) (Tab. 3).
The area within the bank was dominated by the sea urchin Psammechinus microtuberculatus (with 42 % of dominance), whereas the infauna of C. caespitosa was dominated by two boring bivalves, Hiatella artica (with 27 % of dominance) and Rocellaria dubia (19 %).
The overall diversity of the community was quite high (Shannon index H' = 3.05; Tab. 2). The contribution of infaunal organisms associated with colonies of C. caespitosa to richness and abundance values of the sampled area was consistent (74 % of total richness and 94 % of total abundance). Also considering infaunal taxa, the Margalef index (d) passed from a value of 4.28 to a value of 13 and the global diversity of the community (H') increased (Tab. 2). Conversely, the index of equita-bility (J') showed no significant differences, since both
infaunal communities and the surrounding area within the bank were dominated by few taxa with a high abundance (comparable L').
The majority of taxa found in the sampled area are of wide ecological distribution or of uncertain bio-nomic affinity. On the area surrounding colonies only the mollusc Vermetus triquetrus is characteristic of the biocoenosis of Photophilic Algae (AP), and the serpulid Ditrupa arietina is characteristic of the biocoenosis of Coastal Detritic (DC), but neither were significantly abundant (< 1 % of dominance). In those samples, taxa usually associated with AP were present together with taxa associated with DC.
Among the infauna of colonies of C. caespitosa, taxa usually associated with AP and DC were found, but no characteristic species of any biocoenosis were present. Also some typical species for sandy and muddy bottoms namely the bivalves Diplodonta rotundata and Nucula nucleus, and the polychaetes Lumbrineris impatiens and Cirriformia tentaculata, were found.
The benthic community on the biogenic bank at Cape Ronek (without the infauna of colonies of C. caespitosa) differed greatly from other sampled sites at a comparable depth during the same period in Slovenian waters, as shown in other studies (unpublished data). Cluster analysis shows that Cape Ronek (Fig. 5, ACL8) can't be grouped with any other sites along the Slovenian coast.
Macrofaunal feeding guilds
Non-colonial organisms were subdivided into four feeding categories: grazers, suspension feeders, predators, ectoparasites and specialized carnivores and deposit feeders. Among them, 36 taxa were predators (P), 35 suspension feeders (SF), 11 grazers (G), and 17 deposit feeders (DF) (Tab. 3). Predators were mainly poly-chaetes and crustaceans, suspension feeders were represented by molluscs and serpulid polychaetes, grazers were mainly sea urchins, and deposit feeders were other echinoderms and sipunculids.
Within the infauna of C. caespitosa colonies, suspension feeders were the dominant group (64 % of total
Sample	S	N	d	J'	H'	L'
CC	89	3386	10.828	0.641	2.879	0.875
DB	24	215	4.283	0.683	2.172	0.789
TOTAL	108	3605	13.06	0.651	3.050	0.889
s
Tab. 2: Taxa richness, abundance and diversity indices of invertebrates within C. caespitosa colonies (CC), in the surrounding area (DB) and in the overall sampled area (colonial organisms excluded). S = number of taxa, N = number of individuals, d = Margaleff index, J '= Pielou index, H/ = Shannon-Wiener index (loge), L = Simpson index ((-lambda).
Tab. 2: Pestrost, taksonov, abundanca in diverzitetni indeksi za nevretenčarje znotraj kolonij kamene korale (CC), na okoliškem dnu (DB) in na celotnem vzorčnem območju (brez kolonijskih organizmov). S = število taksonov, N = število osebkov, d = Margaleffov indeks, J' = Pieloujev indeks, H/ = Shannon-Wienerjev indeks (loge), L = Simp-sonov indeks (1-lambda).
Fig. 5: Comparison between the sampling site (ACL8) and other sites along the Slovenian coast sampled with the same technique in the same year (unpubl. data). Spring samples: SCL1, SCL2, SCL3, SCL4, SCL6; autumn samples: ACL1, ACL2, ACL3a, ACL3b, ACL8, ACL9. Sl. 5: Primerjava med postajo vzorčenja (ACL8) in drugimi postajami ob slovenski obali, ki so jih avtorji vzorčili z isto metodo v istem letu (neobjavljeni podatki). Pomladni vzorci: SCL1, SCL2, SCL3, SCL4, SCL6; jesenski vzorci: ACL1, ACL2, ACL3a, ACL3b, ACL8, ACL9.
abundance and 34 % of total taxa richness) (Fig. 6), but predators had the highest richness (35 % of total taxa richness). Among suspension feeders, the most dominant were the bivalves H. artica and R. dubia, followed by the bivalve Anomia ephippum, serpulids (mainly Ser-pula concharum) and the crustacean decapod Pisidia longimana. The most abundant predators were poly-chaetes belonging to the families Eunicidae, Syllidae and Polynoidae, together with decapods like Alpheus dentipes and Athanas nitescens.
On the bank around colonies of C. caespitosa, grazers were dominant (more than 56 % of total abundance and 37 % of total taxa richness). Relevant also was the presence of suspension feeders and predators (see Fig. 6). The most abundant grazers were sea urchins P. mi-crotuberculatus and Sphaerechinus granularis, while the most abundant suspension feeder was the bivalve Arca noae. Predators were mainly represented by molluscs (Calliostoma zizyphinum and Hexaplex trunculus) and cnidarians.
Macrofaunal functional groups
The proportion of taxa richness among functional groups from the bank around colonies of C. caespitosa and functional groups within the colonies did not differ significantly (Fig. 7). Free living taxa were dominant (45 % within colonies and 54 % on the area around them), followed by epilithic (25 % both within colonies and on
Fig. 6: Abundance (a) and taxa richness (b) of feeding guilds in the total sampled area (TOT), inside C. caespitosa colonies (CC) and within the bank without infauna (DB). ND = no data available.
Sl. 6: Abundanca (a) in pestrost taksonov (b) prehranjevalnih cehov na celotnem vzorčnem območju (TOT), znotraj kolonij kamene korale (CC) in na okoliškem dnu znotraj bioformacije brez infavne (DB). ND = ni razpoložljivih podatkov.
the surrounded area), while endolithic were only 8 % of all taxa, both within colonies and on the detritic bottom within the bank.
The results were different regarding relative abundance. Among the infauna, endolithic taxa were dominant (50 % of total abundance), followed by free-living organisms (27 %), and by epilithic taxa (13 %). Conversely, on the surrounding area free living organisms were dominant (78 % of total abundance), followed by epilithic animals (16 %), while endolithic taxa were very scarce (2 %) (Fig. 7).
More precisely, in the fauna within colonies the dominant endolithic species were H. artica (27 % of dominance) and R. dubia (19 %), accompanied by endolithic sipunculids (Phascolosoma sp.) and polychaetes (Eunice siciliensis, Lysidice ninetta and Dodecaceria conchar-
Fig. 7: Abundance (a) and taxa richness (b) of functional groups in the total sampled area (TOT), inside C. caespitosa colonies (CC), and on the surrounding detrit-ic bottom within the bank (DB). EN = endolithic, EP = ephilithic, FL = free living, Fl/EP = changing mode with growth, SB = soft bottom, ND = no data available. Sl. 7: Abundanca (a) in pestrost taksonov (b) funkcionalnih skupin na celotnem vzorčnem območju (TOT), znotraj kolonij kamene korale (CC) in na okoliškem dnu znotraj bioformacije (DB). EN = endolitski, EP = epilit-ski, FL = prostoživeč, Fl/EP = spremeni način z rastjo, SB = mehko dno, ND = ni razpoložljivih podatkov.
um). The bivalves H. artica and R. dubia were present also on the surrounded area, but with a low number of individuals (< 2 % of dominance).
The sea urchin P. microtuberculatus (41 % of dominance) was the dominant free-living species on the bank around colonies, while among infauna the dominant free-living species was the polychaete Ceratonereis cos-tae with only 9 % of dominance.
DISCUSSION
The biogenic bank at Cape Ronek is made of a de-tritic layer of dead corallites and, to a lesser extent, of coralline algae, on the top of which living colonies of C. caespitosa grow. Only four comparable formations (in Sicily, Sardinia, Corsica and the Aegean Sea) have
been reported in the Mediterranean Sea (Peirano et al., 1994; Koukouras et al., 1998). Such formations offer a diversified habitat for benthic fauna, which is still mostly unknown.
Cladocora caespitosa's role as a bioconstructor
In optimal ecological conditions the colonial coral C. caespitosa forms large connected formations called coral bioherms or banks (Kruzic & Benkovic, 2008). To our knowledge, up to now only one paper (Koukouras et al., 1998) reported data on macrofauna living on such biogenic formations. Those banks were located close to Diaporos Island (Aegean Sea) and presented a similar structure made of dead corallites on the top of which living colonies of C. caespitosa grow, comparable to that which we found in the Slovenian sea. Compared with the bank at Cape Ronek, the Aegean formations were smaller (max 4 x 5.5 m vs. 200 x 100 m at Cape Ronek). Colonies on the bank at Cape Ronek were of mediumsmall size, with a maximum axis smaller than 20 cm.
At Cape Ronek, dead corallites and coralline algae created a secondary hard bottom where living colonies of C. caespitosa and other typically hard bottom species were able to settle. Consequently, the studied bank hosts a unique faunistic community which, even without taking into consideration C. caespitosa infauna, differed greatly from communities in other sites at a comparable depth (Fig. 5, ACL8). The massive presence of species with a wide ecological distribution and the almost complete absence of species described as characteristic of any biocoenosis make the exact nature of this community difficult to assess.
The consistent contribution of infaunal organisms to the total richness and abundance of the studied area confirms the importance of living colonies of C. caespitosa for local biodiversity. Moreover, only a few species were found to inhabit both examined microhabitats (the colonies of C. caespitosa and the area around the colonies). The general structure of these communities was very different, since the assemblage of the bank around colonies was dominated by echinoderms and big molluscs, while the community within the colonies was dominated by small animals like polychaetes, molluscs and crustaceans. The relatively low number of co-occurring species suggests that this coral, acting as a refugee for animals originating from different habitats, is able to create an 'enclave' supporting different species and is not simply changing species abundance. These results suggest that C. caespitosa plays an important role as a habitat builder both through living colonies and with the accumulation of dead and subfossil corallites.
Infaunal community associated with C. caespitosa
Of the 89 taxa found within colonies 57 were determined to the species level and 21 species are here
Tab. 3: List of invertebrate taxa found in the bank of C. caespitosa: inside (infauna, CC) and/or outside (DB) colonies. Feeding guilds: P = predator, EC = ectoparasite and specialized carnivore, G = grazer, O = omnivore, SF = suspension feeder, DF = deposit feeder, ND = no data available. Functional groups: FL = free living, motile, EP = epilithic (fouling), EN = endolithic (boring), ND = no data available.
Tab. 3: Seznam taksonov nevretenčarjev, najdenih na formaciji sredozemske kamene korale: znotraj (infavna, CC) in/ali v okolici (DB) kolonij. Prehranjevalni cehi: P = predator, EC = ektoparazit in specializiran karnivor, G = str-galec, O = vsejed, SF = suspenzijofag, DF = detritivor, ND = ni razpoložljivih podatkov. Funkcionalne skupine: FL = prostoživeč, gibljiv, EP = epilitski (pritrjen), EN = endolitski (vrtalec), ND = ni razpoložljivih podatkov.
Taxa	Location	Feeding guilds	Functional groups
Mollusca			
Acantochitona fascicularis	CC	G	FL
Anomia ephippum	CC	SF	EP
Arca noe	CC and DB	SF	EP
Bittium reticulatum	CC	G	FL
Bivalvia indet	CC	SF	ND
Calliostoma zizyphinum	DB	EC	FL
Cardidae juv	CC	SF	ND
Cerithiopsis tubercularis	CC	EC	FL
Chama gryphoides	CC	SF	EP
Chiton sp.	DB	G	FL
Chlamys sp.	DB	SF	FL/EP
Mimachlamys varia	CC	SF	FL/EP
Dendrodoridae indet.	DB	ND	FL
Diodora graeca	CC	G	FL
Diodora cf. italica	DB	G	FL
Diplodonta rotundata	CC	SF	ND
Fissurella nabecula	CC	G	FL
Galeomma turtoni	CC	ND	FL
Gibbula magus	DB	G	FL
Hexaplex trunculus	DB	P	FL
Hiatella artica	CC and DB	SF	EN
Telochlamys multistriata	DB	SF	FL/EP
Limaria hians	CC	SF	FL/EP
Limaria tuberculata	DB	SF	FL/EP
Marshallora adversa	CC	EC	FL
Modiolarca subpicta	CC	SF	EP
Modiolus barbatus	CC	SF	EP
Mytilus sp.	DB	SF	EP
Nucula nucleus	CC	DF	ND
Ostrea edulis	CC	SF	EP
Pseudochama gryphina	CC	SF	EP
Rocellaria dubia	CC and DB	SF	EN
Striarca lactea	CC	SF	EP
Vermetus triquetrus	DB	SF	EP
Echinodermata			
Amphipholis squamata	CC	SF/DF	FL
Astropecten irregularis	DB	P	FL
Cucumaria planci	DB	DF/SF	FL
Holothuria tubulosa	DB	DF/SF	FL
Ophioderma longicauda	DB	SF/DF	FL
Paracentrotus lividus	DB	G	FL
Psammechinus microtuberculatus	DB	G	FL
Sphaerechinus granularis	DB	G	FL
Echinoidea juv	CC	G	FL
Ophiotrix cf. fragilis	CC	SF/DF	FL
Tunicata			
Microcosmus sp.	CC and DB	SF	EP
Tunicata indet.	CC	SF	EP
Cnidaria			
Adamsia palliata	DB	P	EP
Cnidaria indet.	CC and DB	P	EP
Sipunculida			
Phascolosoma sp.	CC	DF	EN
Aspidosiphon sp.	CC	DF	EN
Polychaeta			
Eunice torquata	CC	P	FL
Eunice schizobranchia	CC	P	FL
Eunice siciliensis	CC	P	EN
Eunice vittata	CC	P	FL
Eunice harassi	CC	P	FL
Eunicidae 1	CC	P	ND
Eunicidae 2	CC	P	ND
Lysidice ninetta	CC	P	EN
Marphysa sanguinea	CC	P	SB
Nematonereis unicornis	CC	P	FL
Lumbrineris impatiens	CC	P	SB
Lumbrineris coccinea	CC	P	FL
Lumbrineris latreilli	CC	P	SB
Lumbrineris gracilis	CC	P	FL
Syllinae indet.	CC	P	ND
Haplosyllis spongicola	CC	P	FL
Ceratonereis costae	CC	P	FL
Nereis rava	CC	P	FL
Serpula concharum	CC	SF	EP
Vermiliopsis striaticeps	CC	SF	EP
Hydroides pseudouncinatus	CC	SF	EP
Serpula vermicularis	CC	SF	EP
Spirobranchus triqueter	CC	SF	EP
Spirobranchus lamarcki	CC	SF	EP
Ditrupa arietina	CC	SF	DB
Spirorbidae indet.	CC	SF	EP
Serpulidae indet.	CC	SF	EP
Sabellidae indet.	CC	SF	EP
Harmothoe areolata	CC	P	FL
Harmothoe spinifera	CC	P	FL
Polynoe sp.	CC	P	FL
Polynoidae indet.	CC	P	FL
Notomastus cfr. latericeus	CC	DF/SF	FL/EP
Dodecaceria concharum	CC	DF/SF	EN
Cirriformia tentaculata	CC	DF/SF	SB
Aphelochaeta sp.	CC	DF/SF	SB
Polychaetae indet.	CC	ND	ND
Cirratulidae indet.	CC	DF/SF	ND
Phyllodocidae indet.	CC	ND	FL
Phyllodoce cf. mucosa	CC	P	FL
Maldanidae indet	CC	DF	SB
Terebellidae indet	CC	DF	FL/EP
Amphitrite variabilis	CC	DF	EP
Crustacea			
Alpheus dentipes	CC	O/P	FL
Amphipoda indet.	CC	ND	FL
Anisopoda indet.	CC	SF	FL
Athanas nitescens	CC	O/P	FL
Balanus sp.	CC	SF	EP
Galatea sp.	CC	DF	FL
Gnathia sp.	CC	P	FL
Janira maculosa	CC	ND	FLi
Leucothoe sp.	CC	ND	Fli
Liljeborgia dellavallei	CC	ND	FLI
Maera grossimana	CC	ND	FL
Pilumnus cf. hirtellus	CC	G/P/DF	FL
Pisidia longimana	CC	SF	FL
Synalpheus gambarelloides	CC	P/EC	FL
Thoralus chranchii	CC	O/P	FL
Porifera			
Aplysina aerophoba	DB	SF	EP
Haliclona mediterranea	DB	SF	EP
Hippospongia communis	DB	SF	EP
Geodia cydonium	DB	SF	EP
Ircinia variabilis	DB	SF	EP
Ircinia fasciculata	DB	SF	EP
Chondrosia reniformis	DB	SF	EP
Tethya aurantium	DB	SF	EP
Bryozoa			
Schizobrachiella sanguinea	DB	SF	EP
Schizoporella errata	DB	SF	EP
Schizoporella cf. unicornis	CC	SF	EP
Diastoporidae indet.	CC	SF	EP
Celleporidae indet.	CC	SF	EP
reported for the first time as inhabitants of the Mediterranean stony coral C. caespitosa. The present results are not directly comparable with data reported by other researchers (Lumare, 1965; Sciscioli & Nuzzaci, 1970; Za-vodnik, 1976; Schiller, 1993; Arvanitidis & Koukouras, 1994; Antoniadou & Chintiroglou, 2010) since the field sampling and the statistical analysis were different. The overall diversity (Shannon diversity) of the infauna of the bank at Cape Ronek was quite high. However, even higher values were reported for the bank in the Aegean Sea (Koukouras et al., 1998), but such results could be distorted by the smaller colonies' size in the Slovenian bank and consequently the lower sampled volume. Considering colonial organisms as well, in particular sponges, the diversity would be higher. Those organisms were excluded from indices calculation due to the difficulties in the proper quantification of endolithic colonial organisms.
Scleractinian corals are known to influence the invertebrate community in two ways (Reed & Mikkelsen, 1987). Firstly, increasing the three dimensional structures of the seafloor and locally modifying water movement, they create a physical space for facultative associated invertebrates, which can be endolithic, epilithic or free living species. Secondly, they may host obligate symbionts, which can be ectoparasites or predators feeding on coral tissue (e.g. some molluscs, as reported by Robertson (1970) and Reed & Mikkelsen (1987)), or commensals eating coral mucus and entrapped detritus (e.g. some decapods, as reported by Castro (1978) and Carricart-Ganivet et al. (2004)). The consistent abundance and richness of endolithic, epilithic and free living invertebrates found in the present work is related to C. caespitosa morphology, which is similar to the typical tropical reef-building scleractinian corals. Its long and packed corallites provide a cryptic habitat for many small invertebrate species (Zibrowius, 1982; Schuhmacher & Zibrowius, 1985). The presence of species typical of sandy and muddy bottoms among the infauna is probably related to the role of trapping sediment played by Cladocora colonies. The sediment trapped among corallites consolidates coral structure and offers a suitable habitat for small soft bottom species like the polychaetes Lumbrineris impatiens and Cirriformia ten-taculata.
We were unable to find any evidence of obligatory species-specific relationships between the Mediterranean stony coral and the associated infauna since, to our knowledge, all invertebrates found within C. caespitosa colonies so far (Koukouras et al., 1998; present work) were also present in other communities in the Mediterranean Sea, mainly on hard substrate. Nevertheless, in the present work the presence of deposit feeders such
as ophiurids and sipunculids suggests that a facultative commensalism exists with associated taxa feeding on mucus produced by coral and entrapped within sediments.
Threats and conservation
C. caespitosa is a species subject to mass-mortality events, such as those recently recorded in the NW Mediterranean Sea (Rodolfo-Metalpa et al., 2005). Global warming and the related acidification of the ocean pose a serious threat for this species and the associated mac-rofauna (Rodolfo-Metalpa et al., 2005, 2006, 2011). In the Adriatic Sea additional pressures are present, such as coastal modifications and the spread of the non-native invasive green algae Caulerpa racemosa (Kruzic & Benkovic, 2008), which has not yet been recorded in the Gulf of Trieste. Moreover, evidence of C. caespitosa bleaching in the Gulf of Trieste indicates that this species is subjected to some stress, probably related to increasing seawater temperatures (Lipej et al., 2013).
Since large biogenic formations of C. caespitosa are extremely rare in the Mediterranean Sea (Cape Ronek, Sicily, Sardinia, Corsica and Diaporos Island), the peculiarity and high diversity of the associated community and the threat posed by habitat loss and climate change indicate the immediate need for more conservation action. Increasing our knowledge of the role played by C. caespitosa in maintaining marine biodiversity at different levels is of crucial importance for conservation efforts. Studies of tropical corals affected by bleaching events have shown that interactions with other associated taxonomic groups emerged as very important for coral resilience and recovery (McCook et al., 2001; Baker et al., 2008). Therefore, further intensive investigation is required to elucidate the complex interactions between C. caespitosa and the community of invertebrates living inside and near its corallites. A better understanding of these relationships is basic not only to quantify the importance of C. caespitosa as habitat builder, but also to elucidate the potential role of associated organisms in the maintenance of coral health and recovery after stressful events.
ACKNOWLEDGEMENTS
This study was financially supported in part by the Ministry of Agriculture and Environment of Slovenia. A special thanks to Marko Tadejevic and Nicola Bettoso for their immeasurable help and those joyful moments during the fieldwork. We are grateful also to Dr. Katja Stopar for her help during laboratory work and to Dr. Nicola Bettoso, Dr. Floriana Aleffi and Dr. Lisa Faresi (ARPA FVG, Italy) for their help in taxa determination.
MAKROFAVNA, POVEZANA Z BIOFORMACIJO SREDOZEMSKE KAMENE KORALE, CLADOCORA CAESPITOSA (ANTHOZOA, SCLERACTINIA), V TRŽAŠKEM ZALIVU
(SEVERNI JADRAN)
Valentina PITACCO, Martina ORLANDO-BONACA, Borut MAVRIČ & Lovrenc LIPEJ
Morska biološka postaja, Nacionalni inštitut za biologijo, SI-6330 Piran, Fornače 41 E-mail: pitacco@mbss.org
POVZETEK
Sredozemska kamena korala (Cladocora caespitosa, Linneus, 1767) je predstavnik kolonijskih koralnjakov zmernega pasu. Občutljiva je na podnebne spremembe in na antropogene dejavnosti. Zaradi svoje oblike in velikosti lahko kamena korala gosti zelo raznoliko živalsko skupnost. Novembra 2010 so avtorji raziskovali bioformacijo sredozemske kamene korale, ki je bila pred kratkim odkrita pred rtom Ronek (Tržaški zaliv, Slovenija). Potrdili so prisotnost 121 taksonov nevretenčarjev, ki spadajo v 9 različnih debel. Sestava favne znotraj kolonij je bila precej različna od tiste v njihovi okolici znotraj bioformacije. Le 5 taksonov (4 % vseh) je bilo najdenih tako znotraj kolonij kot v njihovi okolici. Rezultati potrjujejo vlogo sredozemske kamene korale kot biogradnika in poudarjajo pomen te izjemne bioformacije za biotsko raznovrstnost.
Ključne besede: Cladocora caespitosa, biogradniki, makro-nevretenčarji, cirkalitoral, severni Jadran
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