Ustica Research Articles

A biomonitoring study: trace metals in seagrass, algae and molluscs in a marine reference ecosystem (Southern Tyrrhenian Sea)

Marine organisms were tested as possible biomonitors of heavy metal contamination in Ustica (island of the Southern Tyrrhenian Sea). The concentrations of Cd, Cr, Cu, Pb and Zn were measured in the phanerogam Posidonia oceanica L. Delile, the two brown algae Padina pavonica (L.) Thivy and Cystoseira sp., and the two gastropod molluscs Monodonta turbinata Born and Patella caerulea L. collected at five coastal stations on the island of Ustica. The biomonitors examined showed a high ability to accumulate metals, with concentration factors higher than 10³, with respect to the concentration (soluble fraction) in marine waters. The data from this study were also compared with those previously obtained from uncontaminated sites in the Sicilian sea (Favignana island, Italy) and those obtained from the area of the Gulf of Gaeta (Tyrrhenian Sea, central Italy). Results clearly show the diversity between these three marine ecosystems.

Genetic population structure of Epinephelus marginatus (Pisces, Serranidae) revealed by two molecular markers

In this paper, data are presented regarding the population structure of dusky grouper (Epinephelus marginatus) which was sampled in the Mediterranean Sea and Atlantic Ocean using two different molecular markers, ND2 RFLP and cytochrome b (cyt b) sequence analysis. The main objective of the study is to analyse the genetic variability of E. marginatus in the Mediterranean Sea to define how the biological characteristics of the species, such as the dispersal capability of pelagic larvae and the benthonic‐sedentary life style, can affect the genetic population structure or maintaining the gene flow or determining genetic differences. Furthermore, we considered an Atlantic sample to establish the presence of genetic differences between the two biogeographical areas under consideration. Analysis of variation based on ND2 RFLP analysis revealed a genetic difference between the Atlantic and Mediterranean samples, whilst cyt b sequence analysis did not. There exists evidence for genetic differentiation for both molecular markers in the Mediterranean region. The majority of the variation was due to the Ustica Island sample and this could be due to differences in fisheries effort since the island is a protected area where recreational and professional fisheries are almost completely forbidden. The pattern of genetic diversity, haplotype networks and mismatch distribution suggest a historical influence on the genetic structure of E. marginatus and recent population expansion. An analysis of the genetic structure of the dusky grouper will be the prerequisite for decisions regarding conservation and fisheries management.

The effects of recreational Paracentrotus lividus fishing on distribution patterns of sea urchins at Ustica Island MPA (Western Mediterranean, Italy)

This study evaluated the effects of recreational Paracentrotus lividus fishing on average density and size of this edible sea urchin, and its indirect effects on Arbacia lixula on barren substrates of Ustica Island MPA (SW Italy, Mediterranean Sea). Size, single and pooled species densities, density of large individuals (>40 mm long) and small individuals (<20 mm long) of the two species were estimated by scuba diving in autumn 2003, spring and summer 2004 at two sites impacted by P. lividus fishing (Punta Cavazzi and Pagliaro, take zone C) and one control (Cala Sidoti, no take zone). Two samplings were performed in each season. We found that reduced densities of P. lividus and A. lixula occurred at the fished sites compared with the unfished sites. P. lividus was always larger and more abundant at the protected site than the fished ones, whereas A. lixula had a larger density at the protected site and greater size at the fished sites. The significantly lower density of A. lixula at the sites subjected to fishing of P. lividus could suggest that A. lixula did not benefit from this kind of fishing and thus the two sea urchins might partially share the same habitat and resources in the barren habitats of “Ustica Island” MPA. These outcomes emphasize the role of regulated fishing in maintaining urchin populations at such low densities that interspecific competition is not induced.

Description of Chone usticensis sp. nov. (Polychaeta, Sabellidae) from the Mediterranean Sea

A new species of Chone (Sabellidae) from the coast of Ustica Island (Mediterranean Sea, north of Sicily) is described. The species, named Chone usticensis sp. nov., is similar to another Mediterranean species, C. filicaudata, in having a long pygidial filiform appendage, but is distinct from this species especially in the peristomium, collar, and in thoracic paleate chaetae shape. A discussion on the presence of the radiolar appendages within the genus Chone is also given.

Recreational fish feeding affects coastal fish behavior and increases frequency of predation on damselfish Chromis chromis nests

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 310:165-172 (2006) - doi:10.3354/meps310165 Recreational fish feeding affects coastal fish behavior and increases frequency of predation on damselfish Chromis chromis nests Marco Milazzo1,*, Isabella Anastasi1, Trevor J. Willis2 1Dipartimento di Biologia Animale, Università di Palermo, Via Archirafi 18, 90123 Palermo, Italy 2Centro Interdipartimentale di Ricerca per le Scienze Ambientali in Ravenna, Università di Bologna, Via S. Alberto 163, 48100 Ravenna, Italy *Email: marmilazzo@iol.it ABSTRACT: Wildlife feeding has become an integral part of the range of activities offered to protected area visitors. In marine protected areas (MPAs), fish feeding may cause changes in the behavior, and thus the density and distribution, of coastal fish species. We evaluated spatial variability in human-positive fish behavior around the Ustica Island MPA (Italy) and the potential indirect effects of behavioral change on other species. Two mensurative experiments demonstrated that ca. 1/3 of the species present in fish-feeding areas exhibited human-positive behavior, losing instinctive fear in the presence of humans and encircling people in the water even when food was not provided. A manipulative experiment demonstrated that this behavioral response was learned rapidly. Damselfishes were negatively affected by the unnatural aggregation of a labrid species, as these aggregations frequently attacked and destroyed the benthic nests of the damselfish. Thus, fish feeding can have both direct and indirect effects. Therefore the MPA management goals need to be explicitly stated on a case-by-case basis. If the aim of a reserve is only to promote awareness of marine life and the benefits of conservation to the public, activities such as fish feeding may be regarded as desirable, since the human-positive behavior brought about by this activity guarantees a visual spectacle for visitors. Fish-feeding locations, however, cannot be regarded as natural and may reduce the effectiveness of a reserve for scientific research. KEY WORDS: Fish-feeding behavior · Indirect effects · Predation · Marine protected area · Mediterranean · Tourism Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 310. Online publication date: April 03, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Structure of a Mediterranean cryptobenthic fish community and its relationships with habitat characteristics

In the last 10 years, several studies have been carried out on the fish fauna of the Ustica Island marine reserve, yet no investigation was specifically addressed to the cryptobenthic fish assemblage. The first task of this study, conducted along the shallow rocky reefs of Ustica, was to determine the species composition, diversity and relative density of the resident cryptobenthic fishes. Furthermore, we aimed to assess the effects of some macro- and microscale habitat characteristics on the distribution pattern of fishes. In particular, the effect of predator density was indirectly evaluated by comparing density data collected within and outside the integral reserve zone. Overall, 20 species belonging to Blenniidae, Gobiidae, Tripterygiidae, Scorpaenidae and Gobiesocidae were recorded. Gobius bucchichi, Scorpaena maderensis, Tripterygion delaisi, T. melanurus and T. tripteronotus were the numerically dominant and most common species. The effects of zone (i.e. of predator density), bottom type and depth on species richness, diversity and evenness were not significant. A greater total fish density was observed on stones compared with rocky cliff and plateau, but only in the shallowest depth range. At level of single species, G. bucchichi was more abundant inside than outside the integral reserve, but only on stones and at 0–2 m depth range. Density of G. bucchichi was generally higher on stones than on rocky cliffs or plateau and between 0 and 5 m depth, although these differences were not always significant. T. delaisi was conversely more abundant in the deepest stratum (7–10 m). Canonical analyses demonstrated that bottom type and depth influenced significantly the fish assemblage structure. The observed differences in the assemblage structure relied mainly upon the dominant species. T. tripteronotus was mainly associated with rocky plateau and the intermediate depth range (3–5 m), whereas S. maderensis, T. melanurus and Lipophrys trigloides inhabited preferentially the rocky cliffs. At microscale level, the habitat choice of the investigated species was almost entirely based on whether the substrate was either vegetated or composed of bare rock. T. delaisi and T. tripteronotus were associated with substrata covered by algae, whilst G. bucchichi, S. maderensis and T. melanurus preferred bare rock bottoms. In some species, the electivity indices for the less abundant type of cover, measured at different spatial scale, changed accordingly. For instance, the smaller the size of the sampled area, the higher was the intensity of the association between G. bucchichi and Anemonia viridis.

Observations of physical effects from tsunamis of December 30, 2002 at Stromboli volcano, southern Italy

On December 30, 2002, following an intense period of activity of Stromboli volcano (south Tyrrhenian Sea, Italy), complex mass failures occurred on the northwest slope of the mountain which also involved the underwater portion of the volcanic edifice for a total volume of about 2–3×107 m3. Two main landslides occurred within a time separation of 7 min, and both set tsunami waves in motion that hit the coasts of Stromboli causing injuries to three people and severe damage to buildings and structures. The tsunamis also caused damage on the island of Panarea, some 20 km to the SSE from the source. They were observed all over the Aeolian archipelago, at the island of Ustica to the west, along the northern Sicily coasts to the south as well as along the Tyrrhenian coasts of Calabria to the east and in Campania to the north. This paper presents field observations that were made in the days and weeks immediately following the events. The results of the quantitative investigations undertaken in the most affected places, namely along the coasts of Stromboli and on the island of Panarea, are reported in order to highlight the dynamics of the attacking waves and their impact on the physical environment, on the coastal structures and on the coastal residential zone. In Stromboli, the tsunami waves were most violent along the northern and northeastern coastal belt between Punta Frontone and the village of Scari, with maximum runup heights of about 11 m measured on the beach of Spiaggia Longa. Measured runups were observed to decay rapidly with distance from the source, typical of tsunami waves generated by limited-area sources such as landslides.

Mafic and ultramafic enclaves in Ustica Island lavas: Inferences on composition of lower crust and deep magmatic processes

Ustica Island, southern Tyrrhenian Sea, is constituted of Quaternary alkaline volcanics. A variety of enclaves representative of deep to supra-crustal settings were recently found in a hawaiitic lava flow. Enclaves consist of: (i) Ultramafic meta-cumulates, i.e. clinopyroxenites and wherlites characterized by variably deformed porphyroclastic to granoblastic textures. (ii) Mafic cumulates, i.e. gabbros (± amphibole) and troctolites, the first often characterized by frequent amphibole breakdown coronas (olivine + Ti-augite + plagioclase + magnetite + ilmenite + rhönite) in response to an H 2O decrease during the ascent, while the troctolites interpreted as meta-cumulates. (iii) Microsyenites, consist of anorthoclase and Fe-clinopyroxene organized in a granular sub-ipidiomorphic texture. Amphibole is absent in Ustica lavas and is found only in some old, now exposed, sub-intrusive volcanic bodies. This evidence suggests a late appearance of amphibole on the liquidus, at a high crystal content that inhibits further ascent of the magma. The importance of the amphibole as a medium pressure liquidus phase in Ustica mafic magmas is in the bearings on the geochemistry of lavas e.g. in buffering Na and Ti abundances, in trace elements partitioning, etc. Density measurements pointed out higher values for clinopyroxenites (3160 to 3300 kg/m 3) than for gabbros (ca. 2900 kg/m 3). Given the density contrast between enclaves and host lavas (2790 kg/m 3) and assuming appropriate rheological models, we calculated a minimum ascent rate of 0.01 m/s, corresponding to an ascent time in the range of 5–29 days for a depth of entrapment of 25 km.

Effects of fish feeding by snorkellers on the density and size distribution of fishes in a Mediterranean marine protected area

Although there is a great deal of evidence to show that supplementary feeding by humans in terrestrial environments causes pronounced changes in the distribution and behaviour of wild animals, at present very little is known about the potential for such effects on marine fish. This study evaluated the consequences of feeding by snorkellers on fish assemblages in the no-take area of the Ustica Island marine protected area (MPA; western Mediterranean) by (1) determining if reef fish assemblage structure is affected in space and time by tourists feeding the fish; (2) assessing the effects of feeding on the abundance of the most common fish species; and (3) assessing the effects of feeding on the size structure of the two most numerically dominant ones. In particular, we hypothesised that both the abundance and the size structure of some fish species would increase at the study site following supplementary feeding, since the additional food provided by humans would make the site more appealing to them. Fish feeding influenced the fish assemblages within the Ustica MPA, and significant spatio-temporal changes occurred. While fish feeding appeared to have no effect on the ornate wrasse Thalassoma pavo, there was a noticeable increase in the number of Oblada melanura and Epinephelus marginatus in the impacted location after feeding. It is very likely that aggregations of fishes that evolve as a result of fish feeding by the public may have negative effects on local populations of fishes and invertebrates that make up their prey. Recreational use of coastal areas and MPAs is increasing elsewhere, making fish feeding a generalised human activity. Accurate information about its effect on the fish assemblage is essential to make responsible management decisions.

The relationship between potassic, calc-alkaline and Na-alkaline magmatism in South Italy volcanoes: A melt inclusion approach

The present-day tectonic setting of the Tyrrhenian Sea is dominated by the eastward migration of the Tyrrhenian–Appenines subduction system and the existence of a contemporaneous and parallel extensional–compressional regime. This complex setting leads to the occurrence of a wide spectrum of magma-types in the South Italy volcanoes. Here, major and trace-element data for primitive melt inclusions preserved in olivine phenocrysts have been obtained in order to add constraints on the origin of the calc-alkaline magmas from the Aeolian arc (Stromboli and Vulcano islands), the potassic magmas from the Campania Province (Vesuvius and Phlegraean Fields) and the Na-alkaline magmas from Ustica Island. The approach used to determine the possible mantle sources of the trapped melts for each population of melt inclusions is based on the determination of the trace-element incompatibility sequence taken as the relative order of increasing bulk partition coefficients, which depends on the mineralogy of the source and gives direct information about minerals residual at the time of melting. Compositional similarities between the melt inclusions and their host lavas suggest that shallow-level magma contamination did not contribute significantly to the geochemical characteristics of the magma-types encountered in the region. Results of the trace-element modelling indicate that the melt inclusions from the Aeolian Islands and Campania Province volcanoes originate from mantle sources strongly affected by subduction-related metasomatic processes. Trace-element relationships of melt inclusions from Vulcano and Stromboli reflect melting of peridotitic sources that have been enriched by a slab-derived, aqueous fluid formed during dehydratation of K-free phases at shallow to intermediate depths. The negative high-field strength elements (HFSE) anomalies of these inclusions were generated in the absence of any residual phase in which HFSE might be compatible. In addition, their major element characteristics require the involvement of a clinopyroxene-rich source component in their genesis. With regard to the Vesuvius and Phlegraean Fields melt inclusions, their calculated incompatibility sequences point to a common phlogopite-bearing mantle source likely to be the result of interaction and hybridisation reactions with K2O and H2O-rich phases released from the slab at larger depths. Finally, trace-element characteristics of melt inclusions from Ustica Island imply the derivation from an upwelling enriched intraplate mantle source with a HIMU-type signature reflecting an ancient basaltic source component. Moreover, the source seems to be contaminated by a slab-derived fluid due to the rollback motion of the Ionian slab, in a process similar to that operating beneath Mount Etna, South of Ustica.

Boat anchoring on Posidonia oceanica beds in a marine protected area (Italy, western Mediterranean): effect of anchor types in different anchoring stages

Seagrasses worldwide are noted for suffering from mechanical damage caused by boat anchoring. This is particularly so in sites highly frequented by boaters (marine protected areas or coastal urbanised areas). In the last decades, different strategies have been put into practice to reduce such impacts on seagrasses (i.e. by anchoring bans or by deploying boat moorings). More recently, in consideration that few marine protected area (MPA) management bodies or local administrations have the resources to enforce their anchorage regulations, the self-regulatory approach based on education and information of boaters has been preferred in several cases. At present, however, very little is known on the correct anchoring practices to ensure the safeguarding of seagrasses. The aim of the present study was to experimentally quantify in the field the damage caused to Posidonia oceanica shoot density by anchoring. A multifactorial experiment was designed to test whether the damage is dependent on (1) different anchor types (Hall, Danforth and Folding grapnel), (2) the use of a chain vs. a rope, (3) the three anchoring stages (anchor fall, dragging/lock-in and weighing), and finally (4) whether the pattern is consistent among different locations of the meadow. As expected, the three anchor types employed in the present study differed in the levels of damage inflicted on the P. oceanica meadows of the Ustica Island MPA. In particular, the use of the Hall type anchor seems to be preferable to minimise this impact in comparison with the other two anchor types. Moreover, the effect on the meadow of the three anchor types is greatly dependent on the anchoring stage. These results confirm that the weighing stage is the critical stage of the anchoring process. The number of damaged shoots of P. oceanica was not affected by the presence of the chain. These patterns were consistent between locations. In the long term, even anchoring on P. oceanica by small boats using low-impact anchors may potentially have detrimental consequences. For this reason, we suggest that in vulnerable sites, it is preferable to implement an educational program based on information of boaters on correct anchoring practices and anchor typology to use, rather than adopting strong restrictions to boat anchoring or deploying mooring buoys. Although the use of these management strategies is still recommended in the case of anchorage frequented by bigger vessels using heavier anchors and chains.

Low-density-lipoprotein peak particle size in a Mediterranean population.

The predominance of small, dense low-density lipoprotein (LDL) particles ('LDL phenotype B') has been associated with a three-fold increased risk of myocardial infarction, but the feasibility of the identification of small, dense LDL as independent predictors of coronary artery disease risk in population studies remains questioned. Design We evaluated the LDL peak particle size and its relation with other established risk factors for coronary heart disease in a group of 156 randomized subjects living on the Mediterranean island of Ustica (71 males and 85 women, range of age 20-69 years), representing approximately 30% of the total population. The prevalence of LDL phenotype B subjects was low (approximately 15% in both men and women) and there was a clear trend for both genders in reducing the LDL peak particle size with age. Moreover, LDL phenotype B subjects had higher BMI values, prevalence of diabetes and plasma triglyceride (TG) levels and lower plasma HDL-C concentrations in comparison with LDL phenotype A individuals; in a multivariate analysis, plasma TG levels were the only variable independently associated with LDL peak particle size. In this population, which appears to be somewhat protected by premature coronary artery disease, a low prevalence of the LDL pattern B was found in both men and women, and plasma TG could have a key role in regulating the LDL peak particle size. The follow up, still ongoing, will provide useful information on the predictive role of LDL peak particle size on cardiovascular risk, at least in a low-risk population.

The non-fraud of the Middle Bronze Age stone goddess from Ustica: a reverse Piltdown hoax

The authors examine claims that the sole surviving example of relief sculpture from the Middle Bronze of Italy or Sicily, discovered in the excavations on the island of Ustica in 1991, is a forgery that was deliberately planted on the site. Their refutation is based on examination of the photographic evidence that has been published in support of these claims.

Butyltins concentration levels and imposex occurrence in snails from the Sicilian coasts (Italy).

Two sampling campaigns have been carried out along the Sicilian coasts within the frame of a European project (Hic-TBT) financed by the LIFE programme. Snails and sediments have been sampled at 5 stations, characterised by very low (Ustica natural sea reserve), low (Ustica harbour), intermediate (Castellamare and Termini Imerese) and high shipping densities (Palermo). Biological and chemical analyses were carried out in order to evaluate the incidence of imposex occurring in snails, and the concentration levels of organotins in sediment and snail samples. Despite the low organotin concentration levels in sediment and snail samples, the results show that imposex is widespread around Sicily. In four locations almost all female snails were affected by imposex at advanced development stages, even in areas with a fairly low shipping density. Only in the natural sea reserve of Ustica Island imposex was relatively less severe. Finally a logarithmic correlation between TBT and imposex stages was observed.

Short-term effect of human trampling on the upper infralittoral macroalgae of Ustica Island MPA (western Mediterranean, Italy)

The short-term response of Mediterranean upper infralittoral macroalgal species to experimental human trampling was investigated. Disturbances of six different intensities were applied within the integral reserve of the Ustica Island marine protected area (Italy, Mediterranean Sea). The dominant macroalgal species Cystoseira brachicarpa v. balearica and Dictyota mediterranea were strongly affected by human trampling. Higher levels of disturbance significantly affected both algal percentage cover and canopy at an increasing rate. Three months after trampling, for both variables it was highlighted that the algal recovery from disturbance was incomplete, being significantly different among trampling intensities. The current study revealed that in the short-term it was not possible to identify critical levels of trampling that are sustainable for this shallow community.

Assessment of microhabitat preferences in juvenile dusky grouper ( Epinephelus marginatus ) by visual sampling

As a top-level predator, the brown grouper Epinephelusmarginatus can play an important role in maintaining the ecological balance of hard-bottom ecosystems. However, to fulfil this role, the species must have a sufficient population density and a wide size range. The presence of such a "healthy" grouper population is one of the known benefits of the protection measures applied to marine protected areas. The availability, in marine reserves, of areas suitable for settlement and recruitment of early juveniles can contribute to preserving a well-structured population. Thus, knowledge of microhabitats preferred by juvenile groupers is an important step in locating, within protected or not yet protected areas, nursery sites that might need a specific protection regime. The aim of the present work was to evaluate habitat and microhabitat preferences of juvenile E. marginatus, in comparison with two other serranids of comparable size, Serranuscabrilla and S. scriba, in the marine reserve of Ustica Island (SW Mediterranean). At different sites, located along the shallow coastal area of the reserve, 329 individuals of the three serranid species were visually surveyed by means of skin- or SCUBA-diving in June 1999. The location of each encountered fish was characterised by both biotic and abiotic variables evaluated at two spatial scales. In order to assess interspecific differences in the use of the spatial environment, the results were analysed by correspondence analysis. According to observations on a small spatial scale, juvenile groupers showed a preference for cavities and recesses, in clear contrast with both Serranus species. When out of such sheltered places, juvenile groupers avoided visually exposed locations (convex substrates and very large visual fields), preferring flat or sub-horizontal rocky substrates. Conversely, S. scriba, and especially S. cabrilla, chose rather open microhabitats (flat to convex substrates, with large to very large visual fields). On a larger spatial scale, brown groupers and the two other serranids showed no marked differences in their habitat preferences.

ChemInform Abstract: Dragmacidin F: A New Antiviral Bromoindole Alkaloid from the Mediterranean Sponge Halicortex sp.

Abstract A new bromoindole alkaloid, named dragmacidin F ( 1 ) and structurally related to other dragmacidins previously described, was isolated from a marine sponge of the genus Halicortex collected off the southern coast of Ustica Island (Italy). Structural elucidation of 1 was achieved by an extensive spectroscopic study (mainly by 1D/2D-NMR and MS techniques). Compound 1 , containing an unprecedented carbon skeleton that is very likely derived from cyclization of a partially oxidized form of dragmacidin D ( 2 ), showed in vitro antiviral activity against HSV-1 (EC 50 =95.8 μM) and HIV-1 (EC 50 =0.91 μM), thus proving to be responsible for the antiviral property exhibited by Halicortex extracts.

Dragmacidin F: A New Antiviral Bromoindole Alkaloid from the Mediterranean Sponge Halicortex sp.

A new bromoindole alkaloid, named dragmacidin F (1) and structurally related to other dragmacidins previously described, was isolated from a marine sponge of the genus Halicortex collected off the southern coast of Ustica Island (Italy). Structural elucidation of 1 was achieved by an extensive spectroscopic study (mainly by 1D/2D-NMR and MS techniques). Compound 1, containing an unprecedented carbon skeleton that is very likely derived from cyclization of a partially oxidized form of dragmacidin D (2), showed in vitro antiviral activity against HSV-1 (EC50=95.8μM) and HIV-1 (EC50=0.91μM), thus proving to be responsible for the antiviral property exhibited by Halicortex extracts.

Effets de l'expansion des Rhodophyceae introduites Acrothamnion preissii et Womersleyella setacea sur les communautés algales des rhizomes de Posidonia oceanica de Méditerranée occidentale

In this study, the macroalgal community of Posidonia oceanica rhizomes was described in relation to different levels of development of the two introduced Rhodophyceae Acrothamnion preissii and Womersleyella setacea. Fifteen P. oceanica meadows were chosen in the western Mediterranean. In each meadow, two samples of five shoots were made at 4 and 15 metres deep. Sixty-five macroalgal species were found: seven Chlorophyta, eight Fucophyceae and 50 Rhodophyta. A. preissii was distributed from the Balearic Islands to Tuscan Archipelago and along the Ustica Island. W. setacea was present in all samples except for Tunisia. The development of algal turfs changed the structure of epiphytic communities. In the colonised areas, A. preissii and W. setacea formed paucispecific populations. Diversity diminished with the increasing of turf developments. Turfs trap sediments, forming a stratum that prevents the development of other algal species. Where the two species were both present, A. preissi reached higher values of dominance. The development of algal turfs seems not limited by the competition between A. preissii and W. setacea. Turf cover was the same independently of the dominant species.

Molluscan assemblages associated with photophilic algae in the Marine Reserve of Ustica Island (Lower Tyrrhenian Sea, Italy)

Very few studies have addressed the effect of protection on macrozoobenthos in marine protected areas, and particularly for sites in the Mediterranean Sea. In the present study, the molluscan assemblages associated with photophilic algal communities of the Marine Reserve of Ustica Island, were investigated. A survey was carried out along transects from 1 to 15 m in depth, during the spring of 1996 at three different sites, subjected to different levels of reserve protection. Species richness and number of individuals reflected the level of protection, and both variables were significantly higher in the integral (most heavily protected) part of the reserve compared with the less well protected buffer areas. Species diversity values showed no correlation with the level of protection. The results reported here do not agree with previous findings on the ‘reserve effect’ involving large‐sized macrozoo‐benthic species. However, the data reported, together with a study on polychaetes from the same study sites, and visual census observations concerning the fish assemblage of the island may support the hypothesis that protection of piscivore and macrocar‐nivore species within the integral reserve suppresses populations of small‐sized microcarnivorous fish species, allowing ‘prey‐release’ of small benthic invertebrates.