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Marine Caves of the Salento Peninsula (Southeastern Apulia, Italy)
Stazione di Biologia Marina, Dipartimento di Biologia, UniversitÓ degli Studi, 73100 Lecce, Italy

Marine Caves

    Marine caves are peculiar coastal environments characterized by sharp physical, chemical and hydrodynamic gradients. For example, light attenuation is responsible for the lack of photosynthetic production in the inner parts of caves. Thus, the distribution of marine organisms is related to these selective environmental features, which allow such caves to be subdivided into distinct ecological zones. On a small scale, marine caves show high biodiversity and habitat diversification (both rocky and sandy). For this reason, they can be considered "miniature natural zoos" where a large variety of marine life, including deep sea species, is represented. From this point of view, the study of marine caves may promote a better understanding of the complex relationships between distribution patterns of organisms and ecological factors. Moreover, marine caves are particularly relevant in regard to ongoing marine protection programs of the Italian Government.

Salento Peninsula

    Salento is a karstic peninsula located in southeastern Italy that contains one of the most significant concentrations of marine caves along the Italian coast (Fig.1) (Onorato et al., 1999). At present, 53 submerged caves have been described. However, the geomorphologic uniformity of the coast suggests that many more await discovery. The well-studied Zinzulusa cave is particularly noteworthy from a biological perspective. The interior of this cave contains an anchialine pool, "Il Cocito", inhabited by a stygobiotic fauna including the recently described endemic sponge Higginsia ciccaresei (Pansini & Pesce, 1998) (Photo 1).


 
Figure 1: Locations of the most important marine caves along the Italian coast. The circle indicates the Salento peninsula. Photo 1: Higginsia ciccaresei (Photo by A. Danieli).


Research Activities of the Laboratory of the Marine Biology Station (University of Lecce)

    The high density of marine caves along the coasts of Salento provides considerable opportunity for biological investigations. Studies on the ecology of marine caves have been undertaken to identify environmental issues and to safeguard these marine ecosystems. Although they have suffered minimal environmental degradation, in fact, they require careful management because of their fragility. The Salento, moreover, is affected by a heavy anthropogenic pressure as a consequence of the date-mussel fishery which leads to desertification of shallow rocky bottoms (Fanelli et al., 1994). Thus, marine caves are important sites for preserving the environmental integrity of those areas.
    A preliminary survey was carried out in the underwater cave "Grotta delle Corvine" (Belmonte et al., 1999; Denitto et al., 1999) (Fig. 2; Photo 2). The results displayed a high biodiversity of sessile fauna (only among sponges, 46 species were recorded) and some uncommon patterns of colonization of hard substrates (Photo 3; 4; 5a; 5b; 6a; 6b). Also noteworthy is the presence on the soft bottom of a dense population of the ceriantid Arachnanthus oligopodus (Photo 7), formerly reported only from a submerged cave near Marseilles, France (Harmelin et al., 1987). The plankton, still under study, contains many components of the so-called hyperbenthos (mainly copepods).


        Click here to view the full size image
    Figure 2: Profile and plan views of "Grotta delle Corvine". Photo 2: "Grotta delle Corvine" site. Photos 2-7 were taken in Grotta delle Corvine by F. Denitto. Photo 3: Red algae such as Peyssonellia squamaria and Lithophyllum frondosum are very abundant within 5 m from the cave mouth.
        Click here to view the full size image
    Photo 4: A rich population of the yellow anthozoan Leptosammia pruvoti characterizes the rocky walls at 15-35 m from the entrance. Photo 5a: A diversified assemblage of sponges develops on the rocky walls and ceiling of the cave. Photo 5b: Closeup view of the sponge Agelas oroides.
        Click here to view the full size image
    Photo 6a: Serpulid polychaetes colonize the rock walls of the inner part of the cave (35-50 m from the entrance). Photo 6b: Closeup view of Serpulidae. Photo 7: A dense population of the cerianthid Arachnanthus oligopodus on the soft bottom of the middle part of the cave.

    From a morphological viewpoint, submerged caves of the Salento show a peculiar type of coralligenous speleothem (a complex biogenic substrate built by calcareous rhodophytes) which hangs from the ceiling in up to 1.2 m long club stalactites (Photo 8). If is not know if these speleothems have a rocky core, or they are the result of a "trickling" organogenous formation.

     

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    Photo 8: Coralligenous stalactites in grotte SasÓ from Belmonte video.

Proposed Research

  • Spatio-temporal dynamics of sessile zoobenthos (hydroids) in caves with varying morphology
  • Structure and dynamics of assemblages of vagile organisms (zooplankton and fish); evaluation of seasonal presence of propagules of sessile organisms in the plankton
  • Assessment of the role of refuge and nursery area for juvenile fish exhibited by marine caves
  • Study of the resting stages found in soft bottom sediments of the cave
  • Study of the "trickling coralligenous" club stalactites
  • Test hypotheses that caves could serve as source areas within marine reserves
  • Identification of vulnerable organisms threatened by diver visitation (biological indicator species)
  • Provide a management plan to minimize impact due to visitors and maximize environmental integrity
  • Provide a database listing biological descriptions of those caves included within protected areas

Participants

    Address: Dipartimento di Biologia, Stazione di Biologia Marina, UniversitÓ degli Studi, 73100 Lecce, Italy

Collaborations

    "Gruppo Speleologico Neretino": this cave diving group operates in the framework of the "Hydra Project" for the exploration, survey and description of the Salento caves. This work will provide:
    • Topographic documentation
    • Photographic inventory
    • Videos of the most significant caves
    Address: Piazza Mercato, 13; 73048 Nard˛ (LE), Italy

References

  • Belmonte G., Costantini A., Denitto F., Della Tommasa L., Miglietta M.P., Onorato R., Poto M. & Vetere M. 1999. Indagine ecologica sulla Grotta sottomarina delle Corvine (Nard˛, Lecce). Biol. Mar. Medit., 6(1): 343-346.
  • Bussotti S., Guidetti P. & Belmonte G., 2003. Distributional patterns of the cardinal fish, Apogon imberbis, in shallow marine caves in southern Apulia (SE Italy). Ital. J. Zool., 70: 153-157.
  • Bussotti S., Denitto F., Guidetti P. & Belmonte G., 2002. Fish assemblages in shallow marine caves of the Salento Peninsula (Southern Apulia, SE Italy). Mar. Ecol., 23(Suppl. 1): 11-20.
  • Denitto F., Longo C., Belmonte G., Costantini A., Poto M. & Onorato R., 1999. Biocenotica della grotta sottomarina delle Corvine (cala di Uluzzu, Nard˛, Lecce). Itin. Speleol., 8: 7-16.
  • Fanelli G., Piraino S., Belmonte G., Geraci S. & Boero F., 1994. Human predation along Apulian rocky coasts (SE Italy): desertification caused by Lithophaga lithophaga (Mollusca) fisheries. Mar. Ecol. Prog. Ser., 110: 1-8.
  • Harmelin J.G., Vacelet J. & Petron C., 1987. MÚditerranÚe vivante. Glenat ed.: pg. 256.
  • Onorato R., Denitto F. & Belmonte G., 1999. Le grotte marine del Salento: classificazione, localizzazione e descrizione. Thalassia Salentina, 23: 67-116.
  • Pansini M. & Pesce G.L., 1998. Higginsia ciccaresei sp. nov. (Porifera: Demospongiae) from a marine cave on the Apulian coast (Mediterranean Sea). J. Mar. Biol. Ass. U.K., 78: 1083-1091.

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