Antonio Pais

The Structure of Mediterranean Rocky Reef Ecosystems across Environmental and Human Gradients, and Conservation Implications

Historical exploitation of the Mediterranean Sea and the absence of rigorous baselines makes it difficult to evaluate the current health of the marine ecosystems and the efficacy of conservation actions at the ecosystem level. Here we establish the first current baseline and gradient of ecosystem structure of nearshore rocky reefs at the Mediterranean scale. We conducted underwater surveys in 14 marine protected areas and 18 open access sites across the Mediterranean, and across a 31-fold range of fish biomass (from 3.8 to 118 g m−2). Our data showed remarkable variation in the structure of rocky reef ecosystems. Multivariate analysis showed three alternative community states: (1) large fish biomass and reefs dominated by non-canopy algae, (2) lower fish biomass but abundant native algal canopies and suspension feeders, and (3) low fish biomass and extensive barrens, with areas covered by turf algae. Our results suggest that the healthiest shallow rocky reef ecosystems in the Mediterranean have both large fish and algal biomass. Protection level and primary production were the only variables significantly correlated to community biomass structure. Fish biomass was significantly larger in well-enforced no-take marine reserves, but there were no significant differences between multi-use marine protected areas (which allow some fishing) and open access areas at the regional scale. The gradients reported here represent a trajectory of degradation that can be used to assess the health of any similar habitat in the Mediterranean, and to evaluate the efficacy of marine protected areas.

Large-Scale Assessment of Mediterranean Marine Protected Areas Effects on Fish Assemblages

Marine protected areas (MPAs) were acknowledged globally as effective tools to mitigate the threats to oceans caused by fishing. Several studies assessed the effectiveness of individual MPAs in protecting fish assemblages, but regional assessments of multiple MPAs are scarce. Moreover, empirical evidence on the role of MPAs in contrasting the propagation of non-indigenous-species (NIS) and thermophilic species (ThS) is missing. We simultaneously investigated here the role of MPAs in reversing the effects of overfishing and in limiting the spread of NIS and ThS. The Mediterranean Sea was selected as study area as it is a region where 1) MPAs are numerous, 2) fishing has affected species and ecosystems, and 3) the arrival of NIS and the northward expansion of ThS took place. Fish surveys were done in well-enforced no-take MPAs (HP), partially-protected MPAs (IP) and fished areas (F) at 30 locations across the Mediterranean. Significantly higher fish biomass was found in HP compared to IP MPAs and F. Along a recovery trajectory from F to HP MPAs, IP were similar to F, showing that just well enforced MPAs triggers an effective recovery. Within HP MPAs, trophic structure of fish assemblages resembled a top-heavy biomass pyramid. Although the functional structure of fish assemblages was consistent among HP MPAs, species driving the recovery in HP MPAs differed among locations: this suggests that the recovery trajectories in HP MPAs are likely to be functionally similar (i.e., represented by predictable changes in trophic groups, especially fish predators), but the specific composition of the resulting assemblages may depend on local conditions. Our study did not show any effect of MPAs on NIS and ThS. These results may help provide more robust expectations, at proper regional scale, about the effects of new MPAs that may be established in the Mediterranean Sea and other ecoregions worldwide.

Harvesting Effects on Paracentrotus lividus Population Structure: A Case Study from Northwestern Sardinia, Italy, before and after the Fishing Season

Abstract PAIS, A.; SERRA, S.; MELONI, G.; SABA, S., and CECCHERELLI, G., 2012. Harvesting effects on Paracentrotus lividus population structure: A case study from northwestern Sardinia, Italy, before and after the fishing season. The edible sea urchin Paracentrotus lividus is commercially exploited in many European countries. In recent years, however, its stocks have shown a large reduction in several regions because of overfishing. This paper reports the effects of harvesting on P. lividus population structure in shallow rocky reefs from a central-western Mediterranean area where this activity is intensively practiced. Density, size (test diam), and biomass of sea urchin were assessed in October 2004 (just before the fishing season) and in May 2005 (immediately after the fishing season) at two locations where intense P. lividus harvest occurs and at two controls within an adjacent Marine Protected Area (MPA) where P. lividus harvest is prohibited. Density, size, and average biomass of P. lividus were significantly higher at the protected areas than at the exploited ones. In particular, large-sized specimens (test diam >5 cm) were notably less abundant at the fished locations; however, very similar results were detected for both the periods examined (i.e., before and after the fishing season), suggesting that effects of pressing activity of harvest through the past years may have produced effects much more evident than those attributable to the single fishing season. These results reveal the existence of a heavy-fishing impact on P. lividus in northwestern Sardinia and the urgent need of regulating its harvesting to prevent severe direct effects on its populations.

On the Movement of the Sea Urchin Paracentrotus lividus Towards Posidonia oceanica Seagrass Patches

ABSTRACT The movement of the sea urchin Paracentrotus lividus from a rocky habitat to patches of Posidonia oceanica was investigated with respect to the size of the sea urchins and their location from the edge of the patch. With this aim, a manipulative experiment was conducted (4 times) at a location where several P. oceanica patches were interspersed on rocky platforms. Each time, after an accurate removal of the sea urchins populating them, 15 of these patches were randomly assigned in sets of 3 to 5 different urchin addition treatments, using groups of 10 large or small P. lividus specimens (test diameter >50 and <30 mm, respectively) positioned at close and far distances (25 and 100 cm, respectively) from the edges of the patches as follows: large-close, large-far, small-close, small-far, and control patches where no urchins were added. The abundance of sea urchins inside the patches was counted after 24 h. Results highlighted significant variability because of the distance from the patches, whereas no significant effect was observed for sea urchin size. These results suggested that: P. lividus specimens close to P. oceanica patches might have a greater probability of reaching them, and that the chance to reach the patch does not depend on the size of sea urchins. In fact, a comparable ability to move towards the patches was evident for different-sized specimens, indicating that migration from one habitat to the other is possible even for small-sized individuals.

Perspectives for development of low impact aquaculture in a Western Mediterranean lagoon: the case of the carpet clam Tapes decussatus

Some 30,000 specimens of the Mediterranean clam Tapes decussatus were suspended in nylon bags of two different mesh sizes and pre-grown in the Calich lagoon (Sardinia, Italy) from March to June 2001. The samples differed in size at the end of the pre-growth stage. They were then sown at a density of 650 specimens m−2 in two stations of the lagoon. The growth rates in the stations were different according to the Von Bertalanffy model. Primary and secondary plankton production was calculated by field measurements as well as by modelling. The results indicate that the Calich lagoon could produce a maximum of 753.25 g m−2 yr −1 WW, with shell, for Tapes decussatus. Our culture experiments lasted 15 months with an estimated mortality of 50% and the yield of T. decussatus was 4.3 times greater than the calculated natural production.

Combined analysis of four mitochondrial regions allowed the detection of several matrilineal lineages of the lessepsian fish Fistularia commersonii in the Mediterranean Sea

The bluespotted cornetfish ( Fistularia commersonii ) is an Indo-Pacific species that in the last ten years colonized a large part of the Mediterranean basin. The aim of this study was to sequence some portions of the mitochondrial DNA (D-loop II, 16S, 12S and Cyt b) of this fish from different localities of the Mediterranean Sea, in order to evaluate the level of its genetic variability in this area. The genetic analysis performed on specimens from seven localities of Sardinia, Tunisia and Libya revealed the presence of at least five mitochondrial lineages. The results obtained, compared with previous studies, indicate that the use of a sufficient number of mitochondrial regions may allow a more accurate estimate of genetic variability in lessepsian invasions.

Spatial variability of fish fauna in sheltered and exposed shallow rocky reefs from a recently established Mediterranean Marine Protected Area

Coastal exposure may affect the structure of littoral fish assemblages. To evaluate its effects, fish assemblages associated with shallow (0–3 m depth) rocky reefs were investigated by visual census at the Asinara Island National Park (northwestern Sardinia, Italy, Mediterranean Sea) during autumn 2003. Distribution patterns of ichthyofauna in sheltered and exposed rocky reefs were assessed over the spatial scales of locations (i.e. kilometres) and sites (i.e. hundreds of metres). Overall, 38 fish taxa belonging to 17 families were recorded, with Labridae, Sparidae and Serranidae being the families with the most species. Univariate analyses showed that the average density of Labridae and Serranidae was significantly greater at sheltered locations, while particulate organic matter feeders (i.e. Mugilidae) were more abundant at the exposed ones. Significant differences in species richness, total fish abundance and densities of Labridae and planktivorous fish were observed at the spatial scale of sites. Multivariate analyses revealed that whole fish assemblages differed more at the scale of locations than among sites. Planktivorous species contributed most to the dissimilarity between fish assemblages associated with exposed and sheltered stretches of coast. Direct and indirect effects of coastal exposure were hypothesized to explain the potential role of wave action in structuring fish assemblages associated with shallow rocky reefs. In particular, direct effects could affect the distribution patterns of fish, depending on their swimming ability, while indirect effects could include changes in the benthic cover (especially macroalgae) caused by wave action, which then had a repercussion on the fish.

Mycobacterium chelonae associated with tumor-like skin and oral masses in farmed Russian sturgeons ( Acipenser gueldenstaedtii )

BackgroundNon-tuberculous mycobacteria responsible for piscine mycobacteriosis usually produce visceral granulomas in both freshwater and marine species. In this study, the first occurrence of Mycobacterium chelonae associated with tumor-like lesions in the Russian sturgeon (Acipenser gueldenstaedtii) is reported. Fifteen sturgeons from an Italian fish farm showing skin and oral cauliflower-like masses were investigated by histopathology, bacterial culture and molecular analyses.ResultsA total of 20 masses different in size located in the mouth and in pectoral and caudal fins (characterized by abundant calcium deposits and by mild to moderate granulomatous inflammation) were observed with a significant different degree of histological severity. All internal organs of the fish were negative for mycobacteria, Ziehl-Neelsen was positive in only one of the oral masses, whereas bacterial and PCR analyses detected the presence of M. chelonae for almost all the skin and oral masses. Based on these results, a calcinosis of dystrophic origin associated with a chronic granulomatous inflammation was considered as a primary diagnosis consequent to tissue injury in areas susceptible to trauma.ConclusionsWe hypothesized that the occurrence of M. chelonae in farmed sturgeons was only a secondary event related to its presence in a stressful rearing environment and subsequent to a dystrophic calcinosis occurred in previously damaged tissues.

Assessment of the use potential of edible sea urchins (Paracentrotus lividus) processing waste within the agricultural system: Influence on soil chemical and biological properties and bean (Phaseolus vulgaris) and wheat (Triticum vulgare) growth in an amended acidic soil

In this study we evaluated the influence of ground purple sea urchin (Paracentrotus lividus) endoskeletons, a processing waste common to all edible sea urchin plants, on the chemical, biochemical and microbiological features of an acidic (pH 5.65) sandy-loam soil. The purple sea urchin endoskeletons were characterized by a high content of total carbonates (∼94%), a moderately alkaline pH in water (pH 7.88) and electrical conductivity values (3.55 mS/cm) very similar to those of commercial lime. To evaluate the influence of the P. lividus endoskeletons on soil properties four different amendment rates were tested, notably 0.5, 1.0, 3.0 and 5.0% based on soil dry weight, and the effects compared with those recorded on unamended control soil. The addition of the purple sea urchin processing waste caused an immediate and significant pH increase which was positively related to the rate of the amendment addition. After a six months equilibration period, the differences in soil pH were still evident and significant increases of electrical conductivity and available phosphorus were also detected in soils with the higher amendment rates. The number of heterotrophic and cellulolytic bacteria and actinomycetes significantly increased after amendment addition while the number of culturable fungi steadily declined. The analysis of the Biolog Community Level Physiological Profile indicated a clear influence of the purple sea urchin processing waste on the structure of the native microbial community while a significant increase of microbial functionality (i.e. dehydrogenase activity) was recorded in soil treated with the higher amendment rates (i.e. 3.0 and 5.0%). The improvement of microbial abundance and functionality as well as the change of the microbial community structure were ascribed to the pH shift induced by the P. lividus processing waste. To investigate possible effects on soil fertility, dwarf bean (Phaseolus vulgaris) and wheat (Triticum vulgare) growth were also assessed in a pot experiment. Plant growth was unaffected (wheat) or stimulated (bean) by the amendment addition in the 0.5-3.0% range while the higher amendment rate (i.e. 5.0%) was detrimental for both plant species indicating a phytotoxic effect which could be due to different factors such as an excess of calcium in soil, a suppression of Mg uptake or the higher EC values detected at the highest amendment rate. It is concluded that ground P. lividus endoskeletons have potential as a soil amendment to ameliorate chemical and biological properties of acidic Mediterranean soils. This seems particularly relevant, especially at the lower amendment rates, since for the first time, a sustainable management system is proposed for P. lividus processing waste, which foresees economic value in the sea urchin by-product through its re-use within the agricultural production system.

Molluscs and echinoderms aquaculture: Biological aspects, current status, technical progress and future perspectives for the most promising species in Italy

Shellfish aquaculture is a widespread activity in the Italian peninsula. However, only two bivalve species are mainly cultured along the coastline of that country: the Mediterranean mussel Mytilus galloprovincialis and the Manila clam Venerupis philippinarum (Ruditapes philippinarum). By contrast, just a few other mollusc species of commercial interest are scarcely reared at a small-scale level. After analysing the current status of Italian shellfish production, this paper reports and discusses the potential for culturing several different invertebrate species [i.e., the European flat oyster Ostrea edulis, the grooved carpet shell Venerupis decussata (Ruditapes decussatus), the razor clams Ensis minor and Solen marginatus, the cephalopod Octopus vulgaris, and the purple sea urchin Paracentrotus lividus] in this country. In addition, a detailed overview of the progress made in aquacultural techniques for these species in the Mediterranean basin is presented, highlighting the most relevant bottlenecks and the way forward to shift from the experimental to the aquaculture phase. Finally, an outlook of the main economic and environmental benefits arising from these shellfish culture practices is also given.