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Biodiversity of the Banco di Santa Croce, a marine protected area in the Gulf of Naples

Valerio Zupo 
Stazione Zoologica A. Dohrn, 
Benthic Ecology Laboratory, 
Punta San Pietro, 
80077 Ischia (NA), Italy

Figure 1. Bank of Santa Croce, Gulf of Napoles.

The Bank of Santa Croce is a protected area located in the Bay of Naples (Fig. 1) characterized by a series of carbonate rock hills (Fig. 2) hosting highly differentiated benthic communities. Photophilic associations with dominance of brown algae (Padina pavonica and Sargassum sp.) dominate the top of hills, while macroalgal assemblages typical of sciaphilic environments (Peyssonellia borneti and Flabellina petiolata) characterize the vertical walls. Zoocenoses are dominated by Eunicella cavolinii, Parazoanthus axinellae, Paramuricea clavata and Gerardia savaglia. Species characteristic of "very stable" environments (e.g., red coral) are present mainly at the deeper stations (>20 m), but also the shallowest sites (11 m) contain, almost exclusively, "climax" benthic communities. Benthic fauna is highly diverse (Fig. 3) and the presence of decapods previously known only for the Adriatic Sea (e.g., Palicus caronii Roux, 1830) was recorded. Abundant fish stocks, mainly represented by members of the families Labridae, serranidae and sparidae, characterise the area. However, two young specimens of Zu cristatus Bonelli 1819 were recently observed in shallow waters: this species was considered oceanic and mesopelagic.

Figure 2. Model of the bank, reconstructed using a 'kriging' interpolator.

Our Research Programme (P.I. V. Zupo and M.C. Buia) was aimed at the characterization of ecological descriptors and at the investigation of structural and functional relationships benthos-nekton-plankton within this protected area, to allow the formulation of an effective management and protection plan. 

Several data-sets were collected and analysed (Nutrient concentration in the water column, chemical and physical descriptors, water currentometry, fractioned chlorophyll, micro- and macro-zooplankton, fish stocks evaluated by visual census and collections by nets, gut contents of fish and benthic invertebrates, faunistic and floristic composition of benthic assemblages, heavy metal contents of the tissues of fish) to obtain a dynamic model of simulation of the food web within the area. The model, based on budget equations for each of the 552 species identified, was calibrated and validated based on the data collected during a 3-year investigation. The model demonstrated that, despite the fishing prohibition regime, the area is impacted by the collections of benthic and nektonic organisms.

Figure 3. View of shallow communities, illustrating the great biodiversity of the Bank area.
It was also recorded the great biodiversity of the area and the function of the bank as an energy transducer, based on the continuous transformation of organic matter deriving from the Sarno River in production of biomasses of high economic value. The productivity peaks in spring and summer and the total export of animal biomass to surrounding systems is about 23 kg yr-1 m-3 . These biomasses are not affected by inorganic pollution, as demonstrated by the analyses of heavy metals. The sensitivity analysis demonstrated that high productivities of the bank are sustained by both the input of organic matter (transported by strong currents), and the local primary production. The analysis indicated that a higher level of protection of benthic communities and the preservation of the present hydrodynamic patterns will allow an optimal management and an increase of the export of fish biomass.

The coastal areas around the Sarno River are considered among the most impacted by organic and inorganic pollution, in the whole Mediterranean basin. It was very interesting to detect highest levels of biodiversity into the bank (which is located within this area). The results of the Research Programme opened new perspectives in the study of the relationships between human impacts and diversity and highlighted the existence of unresolved ecological paradigms, worth to be investigated.

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