254
M. Cormaci et al.
Discussion and Conclusions
Apart from midlittoral communities and the
shallow community with Cystoseira amentacea v.
stricta, the benthic vegetation of the Tremiti
Islands appears little structured. In particular,
the most striking thing is the lack of other
infralittoral photophilic communities with
Cystoseira spp. and Sargassum spp. that, as
known, characterise in the Mediterranean Sea
the vegetation on rocky substrata in unpolluted
environments (Giaccone and Bruni 1973; Ros et
al. 1985). Even though it was impossible to carry
out any comparisons between previous and present vegetational characteristics of that area,
because of all the previous papers on those
islands dealt only with flora, the occurrence in
the sixties-seventies years of Cystoseira crinita, C.
schiffneri f. tenuiramosa, C. spinosa, Sargassum
acinarium and S. hornschuchii (Rizzi Longo
1972}, leads us to suppose the occurrence, at that
time, of the above mentioned photophilic communities in that area. Therefore, we can conclude
that the benthic algal vegetation of the Tremiti
Islands has undergone a considerable structural
deterioration, during the last three decades,
mainly in the infralittoral zone. Such a kind of
deterioration might be due to different factors
like the occurrence of more or less toxic pollutants (often linked to suspended inert terrigenous materials), eutrophication, overgrazing by
sea-urchins, fishery activities and anchoring, etc.
However, at the Tremiti Islands, neither the
occurrence of dense populations of sea-urchins
causing overgrazing, nor fishery activities and
anchoring sufficiently important to cause heavy
damage to the benthic vegetation, nor eutrophication (see below), were observed. Conversely,
during our dives, a noticeable water turbidity due
to the presence of suspended inert terrigenous
materials was observed. A reduction in water
transparency in the Southern Adriatic from sixties to eighties in both the coastal and open
waters was recorded by Morovic and Domijan
(1991). Such a reduction was related by ZoreArmanda (1991) to the eutrophication of the
Adriatic waters. But, both the persistence of the
above mentioned well structured midlittoral
communities as well as of the Cystoseira amentacea v. stricta belt compared with the lack of
communities with Ulvales near the surface, indicate the lack of eutrophication in the Tremiti
Islands, at least in shallow waters. Therefore,
agreeing with Cormaci and Furnari (1999), we
think that the above mentioned structural deterioration of the benthic algal vegetation is mainly
due to the increased turbidity of waters related to
the presence of inert terrigenous suspended
materials, even though the occurrence of toxic
pollutants cannot be excluded.
Acknowledgements. This work was supported by a grant from
the Italian C.N.R. within the Project PRISMA 2, sub-project 3.
We are grateful to the Mayor of the Commune Isole Tremiti
for facilities during sampling campaign.
References
Ballesteros E (1992) Els vegetals i la zonaci6 litoral: esproes,
comunitats i factors que influeixen en la sen distribuci6.
Inst Estud Catalans Secd6 Cienc BioI, Barcelona
Boudouresque C-F (1974) Aire minima et peuplements algaux
marins. Bull Soc Phycol Fr 19: 141-157
Braun-Blanquet J (1928) pflanzensoziologie. Springer, Berlin
Heidelberg New York Tokyo
Cormaci M,Furnari G (1999) Change of the benthic algal flora of
the Tremiti Islands (Southern Adriatic) Italy. In: Kain
(Jones) 1M, Brown TM, Lehaye M (eds) Proc 16 th lnt Seaweed
Symp. Hydrobiology 398/399, pp 75-79
Giaccone G (1969) Raccolte di fitobenthos sulla banchina continentale italiana. G Bot Ital103: 485-514
Giaccone G (1978) Revisione della flora marina del mare
Adriatico. Annu WWF Parco Mar Miramare Trieste 6: 5-118
Giaccone G, Bruni A (1973) Le Cistoseire e la vegetazione sommersa del Mediterraneo. Atti Ist Veneto Sci Lett Arti Venezia
131:59-103
Mcruvic M, Domijan N (1991) Light attenuation changes in the
middle and southern Adriatic. Acta Adriat 32: 621-635
Pignatti S, De Cristini P, Rizzi L (1967) Le assodazioni algali della
grotta delle Viole nell'isola di S. Domino (Is. Tremiti). G Bot
ItallOl: 117-126
Rizzi Longo L (1972) La flora sottomarina delle Isole Tremiti. Atti
1st Veneto Sci Lett Arti Venezia 130: 329-376
Ros 10, Romero J, Ballesteros E, Gili MJ (1985) Diving in blue
water: the benthos. In: Margalef R (ed) Key environments:
Western Mediterranean. Pergamon Press, Oxford. pp 233-295
Solazzi A, Totti C, Marzocchi M (1991-1994) Epifitismo in
Halimeda tuna (El. et Sol.) Lam. (Chlorophyceae,
Siphonales) Isole Tremiti, Adriatico Meridionale. Nova
Thalassia 12: 69-79
Woelkerling WI, Lawson GW, Price JR, John DM, Pmd'homme
van Reine W (1998) Seaweeds of the western coast of tropical Mrica and adjacent islands: a critical assessment. IV.
Rhodophyta (Florideae) 6: genera [Q] R-Z, and an update of
current names for non-geniculate Corallinales. Bull Br Mus
Nat Hist Bot 28: 115-150
Zore-Armanda M (1991) Natural characteristics and climatic
changes of the Adriatic sea. Acta Adriat 32: 567-586
M. Cormaci et al.
Discussion and Conclusions
Apart from midlittoral communities and the
shallow community with Cystoseira amentacea v.
stricta, the benthic vegetation of the Tremiti
Islands appears little structured. In particular,
the most striking thing is the lack of other
infralittoral photophilic communities with
Cystoseira spp. and Sargassum spp. that, as
known, characterise in the Mediterranean Sea
the vegetation on rocky substrata in unpolluted
environments (Giaccone and Bruni 1973; Ros et
al. 1985). Even though it was impossible to carry
out any comparisons between previous and present vegetational characteristics of that area,
because of all the previous papers on those
islands dealt only with flora, the occurrence in
the sixties-seventies years of Cystoseira crinita, C.
schiffneri f. tenuiramosa, C. spinosa, Sargassum
acinarium and S. hornschuchii (Rizzi Longo
1972}, leads us to suppose the occurrence, at that
time, of the above mentioned photophilic communities in that area. Therefore, we can conclude
that the benthic algal vegetation of the Tremiti
Islands has undergone a considerable structural
deterioration, during the last three decades,
mainly in the infralittoral zone. Such a kind of
deterioration might be due to different factors
like the occurrence of more or less toxic pollutants (often linked to suspended inert terrigenous materials), eutrophication, overgrazing by
sea-urchins, fishery activities and anchoring, etc.
However, at the Tremiti Islands, neither the
occurrence of dense populations of sea-urchins
causing overgrazing, nor fishery activities and
anchoring sufficiently important to cause heavy
damage to the benthic vegetation, nor eutrophication (see below), were observed. Conversely,
during our dives, a noticeable water turbidity due
to the presence of suspended inert terrigenous
materials was observed. A reduction in water
transparency in the Southern Adriatic from sixties to eighties in both the coastal and open
waters was recorded by Morovic and Domijan
(1991). Such a reduction was related by ZoreArmanda (1991) to the eutrophication of the
Adriatic waters. But, both the persistence of the
above mentioned well structured midlittoral
communities as well as of the Cystoseira amentacea v. stricta belt compared with the lack of
communities with Ulvales near the surface, indicate the lack of eutrophication in the Tremiti
Islands, at least in shallow waters. Therefore,
agreeing with Cormaci and Furnari (1999), we
think that the above mentioned structural deterioration of the benthic algal vegetation is mainly
due to the increased turbidity of waters related to
the presence of inert terrigenous suspended
materials, even though the occurrence of toxic
pollutants cannot be excluded.
Acknowledgements. This work was supported by a grant from
the Italian C.N.R. within the Project PRISMA 2, sub-project 3.
We are grateful to the Mayor of the Commune Isole Tremiti
for facilities during sampling campaign.
References
Ballesteros E (1992) Els vegetals i la zonaci6 litoral: esproes,
comunitats i factors que influeixen en la sen distribuci6.
Inst Estud Catalans Secd6 Cienc BioI, Barcelona
Boudouresque C-F (1974) Aire minima et peuplements algaux
marins. Bull Soc Phycol Fr 19: 141-157
Braun-Blanquet J (1928) pflanzensoziologie. Springer, Berlin
Heidelberg New York Tokyo
Cormaci M,Furnari G (1999) Change of the benthic algal flora of
the Tremiti Islands (Southern Adriatic) Italy. In: Kain
(Jones) 1M, Brown TM, Lehaye M (eds) Proc 16 th lnt Seaweed
Symp. Hydrobiology 398/399, pp 75-79
Giaccone G (1969) Raccolte di fitobenthos sulla banchina continentale italiana. G Bot Ital103: 485-514
Giaccone G (1978) Revisione della flora marina del mare
Adriatico. Annu WWF Parco Mar Miramare Trieste 6: 5-118
Giaccone G, Bruni A (1973) Le Cistoseire e la vegetazione sommersa del Mediterraneo. Atti Ist Veneto Sci Lett Arti Venezia
131:59-103
Mcruvic M, Domijan N (1991) Light attenuation changes in the
middle and southern Adriatic. Acta Adriat 32: 621-635
Pignatti S, De Cristini P, Rizzi L (1967) Le assodazioni algali della
grotta delle Viole nell'isola di S. Domino (Is. Tremiti). G Bot
ItallOl: 117-126
Rizzi Longo L (1972) La flora sottomarina delle Isole Tremiti. Atti
1st Veneto Sci Lett Arti Venezia 130: 329-376
Ros 10, Romero J, Ballesteros E, Gili MJ (1985) Diving in blue
water: the benthos. In: Margalef R (ed) Key environments:
Western Mediterranean. Pergamon Press, Oxford. pp 233-295
Solazzi A, Totti C, Marzocchi M (1991-1994) Epifitismo in
Halimeda tuna (El. et Sol.) Lam. (Chlorophyceae,
Siphonales) Isole Tremiti, Adriatico Meridionale. Nova
Thalassia 12: 69-79
Woelkerling WI, Lawson GW, Price JR, John DM, Pmd'homme
van Reine W (1998) Seaweeds of the western coast of tropical Mrica and adjacent islands: a critical assessment. IV.
Rhodophyta (Florideae) 6: genera [Q] R-Z, and an update of
current names for non-geniculate Corallinales. Bull Br Mus
Nat Hist Bot 28: 115-150
Zore-Armanda M (1991) Natural characteristics and climatic
changes of the Adriatic sea. Acta Adriat 32: 567-586