This study examined patterns in the distnbution and demography of the barnacle Chthamalus steiiatus (Poli) at different spatial scales in the northwest Mediterranem. Prelirninary data indicated that the abundance and size of barnacles decreased from high-shore to low-shore habitats. The generality of these patterns was investigated at several locations (10s to 100s of km apart), at several sites within locations (100s to 1000s of m apart) and at different times. Patterns were consistent with the prelirninary observations, despite considerable spatial and temporal variabiiity at smaii and large spatial scales. The foliowing models were proposed to explain the observed patterns: (1) recruitment was intnnsicaiiy greater high on the shore, (2) limitation of recruitment due to pre-emption of the substratum was greater low than high on the shore, (3) environmental conditions reduce growth low on the shore, and (4) mortality was greater low on the shore. The predictions of these models were tested by examining patterns of recruitment, growth and mortality of barnacles and avaiiability of free space in relation to height on the shore, at several spatial scales and through time. Successful recruitment of barnacles was observed at different heights on the shore where resident organisms were removed, despite a trend toward a larger number of recruits high on the shore at 1 location (Livorno). Availabiiity of bare rock for recruitment was greater high on the shore, implying that pre-emption of the substratum was more intense low on the shore. There was no evidence to suggest that barnacles grew faster on the high shore than on the low shore. The opposite pattern was observed for young barnacles in several cases. Mortality rates were generally greater in low-shore than high-shore habitats for young and for adult barnacles. Patterns emerged over a background of considerable spatial and temporal vanation. These results emphasized the importance of pre-emption of space and mortality of juveniles in generating patterns in the distnbution and structure of populations of barnacles on rocky shores in the northwest Mediterranean.
Hulophilu stipulucea, a seagrass introduced into the Mediterranean Sea as a Lessepsian immigrant, is nowadays common in the eastern Mediterranean, and it was recently recorded in the western Mediterranean; very little information is available about the algal flora associated with this species. During a survey of a Hulophilu stipuluceu stand at Vulcano Island (Eolian Islands, western Mediterranean), samples were collected at three depths (5 m,15 m and 25 m) for identification of algal epiphytes. Thirty-six species of macroalgae were found. The epiflora of the leaves consisted of 20 species, the others being mixed with or entangled in the rhizomes. On the leaves,'Cerumium tenerrimum, Dusyu corymbiferu, Polysiphoniu cfr. tenerrimu, Spyridiu filumentosu, Chondriu pygmueu and Laurenciu sp. were the most common species; between the rhizomes, Dictyotu Eineuris was abundant. A differentiation of the epiphytic assemblage between 5 m and the other depths was observed; the 5 m samples were characterized by the abundance of Cerumium tenerrimum, Chondriupygmueu and Polysiphoniu cfr. tenerrimu, while at 15 m and 25 m Luurenciu sp., Dusyu corymbiferu and SpyridiaJilumentosu were the most common species. Epiphytic cover was generally very low. No rare species were found among the epiphytes. In comparison with other Mediterranean seagrasses, HuZophiZu stipuluceu has a qualitatively and quantitatively poor epiphytic flora. In particular, the virtual absence of encrusting corallines is noteworthy. A fast turnover rate of the leaves is hypothesized to be the main reason for this scarcity. Differences between this and other studies on epiphytes of Hulophilu stipuluceu stands are discussed. 0 Elsevier,
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