Marcello Catra

Changes in the benthic algal flora of Linosa Island (Straits of Sicily, Mediterranean Sea)

Abstract A study of the benthic algal macroflora of Linosa Island (Straits of Sicily, Mediterranean Sea) is presented, aiming to verify possible floristic changes that have occurred in the area, last studied in 1973. We found noticeable changes in the benthic flora, which is now poorer in species than that recorded in the literature (233 species against 305), with a minor decrease in Phaeophyceae and Chlorophyta, and a more significant decrease in the number of Rhodophyta. Only 178 species in the present flora were reported previously, while 127 previously reported were not found during the present study. Conversely, 55 species were newly found. Several species of Fucales, like Cystoseira brachycarpa, C. sauvageauana, C. spinosa, C. zosteroides, Sargassum acinarium and S. trichocarpum, which are characteristic of the Mediterranean Sea photophilic communities on hard substrata and sensitive to any environmental changes, have disappeared.

Resource partitioning among early colonizing Siganus luridus and native herbivorous fish in the Mediterranean: an integrated study based on gut-content analysis and stable isotope signatures

The present study attempts to give timely information on the resource partitioning between the lessepsian migrant Siganus luridus and two ecological native analogues, Sarpa salpa and Sparisoma cretense. Sampling was carried out in concomitance with the first record of Siganus luridus in Linosa and fish were caught simultaneously, allowing direct comparison of diets. Gut-contents analyses provided a snapshot of the feeding habits of the three species: Siganus luridus fed on 34 taxa of benthic algae (mostly represented by Dictyota dichotoma) and a total of 27 taxa was identified in the stomach of Sarpa salpa, with the predominance of Sargassum vulgare. For the first time, a detailed picture of Sparisoma cretense diet was given (N=22 taxa of identified algae) albeit, due to the high percentage of digested food, this species was excluded from gut-content comparisons. A certain resource partitioning between Siganus luridus and Sarpa salpa was resolved on the basis of trophic indices and multivariate analyses, these latter also highlighting a more dispersed diet for Siganus luridus with respect to Sarpa salpa. Isotopic signatures were important towards defining the trophic level of the three species and particularly of Sparisoma cretense, whose gut-contents analysis was only partially informative. The values of δ 15 N confirmed a strictly vegetal diet for Siganus luridus and Sparisoma cretense while Sarpa salpa was significantly more enriched. According to δ 13 C, observed values matched the predicted ones for Siganus luridus and Sarpa salpa while both species presented less enriched δ 15 N values than expected.

Spring Marine Vegetation on Rocky Substrata of the Tremiti Islands (Adriatic Sea, Italy)

Spring aspect of the benthic marine communities on rocky substrata from midlittoral to circalittoral zones of the Tremiti Islands (Adriatic Sea) is described. From a comparison with literature data the disappearance of species characterising well structured infralittoral photophilic communities on rocky substrata like Cystoseira spp. and Sargassum spp., resulted. This finding led us to suppose that a considerable structural deterioration of phytobenthic communities has occurred during the last three decades, probably because of an increase of water turbidity.

The benthic algal flora on rocky substrata of the Tremiti Islands (Adriatic Sea)

ABSTRACT The results of a floristic study of benthic marine macroalgae on rocky substrata from the Tremiti Islands (Adriatic Sea) are presented. The list of taxa at specific and infraspecific level consists of 226 Rhodophyceae, 59 Fucophyceae and 36 Chlorophyceae. Of these 321 taxa, 147 are newly reported from the Tremiti Islands. Data on the reproductive phenology of each species, and comments on some species of particular interest are also given.

Summer biomass of a population of Phyllophora antarctica (Phyllophoraceae, Rhodophyta) from Antarctica

Results of a study on summer biomass in aninfralittoral population of Phyllophora antarctica A.et E. S. Gepp from Terra Nova Bay (Ross Sea,Antarctica) are reported. The population studied grewat depths of 5 to 12 m. The highest value of biomass(1548 wet g m−2) was found at the end of January at6 m depth. Data showed that biomass depended mainly onthe presence or absence of large heavy specimens, eventhough these were always few in number. Moreover, thevery high number of specimens in weight classes 1 (upto 0.03 wet g) and 2 (> 0.03 to 0.06 wet g) recordedfrom December to January showed a relevant productionof new thalli in that period; the decrease of thetotal number of thalli from 8832 counted on 30December to 4384 counted on 10 February, showed someself-thinning in the population; the occurrence ofnumerous thalli belonging to weight classes 3 (>0.06 to 0.125 wet g), 4 (> 0.125 to 0.25 wet g) and5 (> 0.25 to 0.5 wet g) just at the end of December,allows to conclude that P. antarctica continues togrow, although at low rate, during the period ofwinter darkness. Finally, both the low number ofthalli of weight classes 6 (> 0.5 to 1 wet g) and 7(> 1 to 2 wet g) and the absence of thalli of theweight class 8 (> 2 wet g), recorded at the end ofDecember, indicate that most of specimens reachingduring the winter such weight classes (due to theirability to dark growth), died before summer.

Observations on Cystoseira squarrosa De Notaris (Fucophyceae, Fucales), a Rare and Little Known Mediterranean Species, and Its Typification

Abstract A study of the morphology of the brown alga Cystoseira squarrosa De Notaris, a rare and little known species, was carried out on numerous thalli collected at Torre del Serpe near Otranto (Apulia, Italy). Because the original material of this species, held in the Herbarium of the University of Genova (GE), was destroyed during the Second World War, a neotype is designed here. The species is well characterized by the combination of the following characters: not caespitose, bush-like habit; short primary axis bearing 1–2 secondary axes inserted at right angle; oblong and warty tophules; slightly prominent and smooth apex of the axes; robust, rigid, flattened, not spaced spinose appendages with bifid, trifid or multifid apices and conceptacles grouped at the base of the spinose appendages.

Floristic macroalgal diversity in selected submarine caves located within two marine protected areas off Lampedusa Island and Sicily (Italy)

Abstract We investigated phytobenthos in submerged marine caves. Underwater caves have rarely been examined for floristic composition. The study was carried out in two Mediterranean marine protected areas (MPAs) [Plemmirio (Maddalena Peninsula, Syracuse, Ionian Sea) and Pelagean Islands (Straits of Sicily)] and the caves were chosen on the basis of their geomorphology, exposure, and bathymetry. From our comparative study of cave floras, we demonstrated that the macroalgal flora of each cave is influenced by the floristic composition of the adjacent area that is a natural source of recruits and by the light environment. Caves that are “visited” (i.e., those situated on one of the underwater routes for scuba divers visiting the MPAs) had floristic richnesses higher than those of “scarcely” or “not visited” ones (i.e., not on tourist routed). This is likely because the visited caves, due to their large entrance and shallow location, have good lighting that favors high macroalgal biodiversity.

Observations sur Cystoseira susanensis (Cystoseiraceae, Phaeophyta): une espèce méditerranéenne rare et peu connue

Abstract A study of the morphology of the brown alga Cystoseira susanensis, a species known only from the type locality (Susa, Lybia) and from southeastern Sicily, was carried out on numerous thalli occurring in littoral rockpools at Marzamemi (Syracuse, Italy). The species has a short primary axis bearing numerous secondary axes close to the base. Such a branching pattern probably led Nizamuddin to consider his species as caespitose, while, on the contrary, it is not caespitose. Observations in culture of the first phases of segmentation of zygotes as well as of the first growth stages of germlings are also provided.

First Record of Haloguignardia cystoseira (Ascomycota) Parasitic on Cystoseira elegans (Fucophyceae) from the Mediterranean Sea

Abstract The finding of galls caused by Haloguignardia cystoseirae on Cystoseira elegans from the SE Sicilian coast (Italy) is reported. It is the first record of this species after its description from Corsica. Cystoseira elegans represents a new host for that fungus previously reported only on Cystoseira balearica (= Cystoseira brachycarpa).

First record of fertile gametophytes of Polysiphonia perforans (Ceramiales, Rhodophyta)

Abstract We report fertile gametophytes of Polysiphonia perforans for the first time in collections from the Mediterranean Sea. The occurrence of spermatangial axes replacing whole trichoblasts and four-celled carpogonial branches, in addition to the previously known features, such as the occurrence of four pericentral cells, the open connection between rhizoids and pericentral cells and the straight arrangement of tetrasporangia, allow us to confirm that the species belongs to the genus Polysiphonia.