original scientific article	UDC 581.9:582.26/.27(262.3-18)
received: 2005-05-02
DEVELOPMENT OF THE INVASIVE TURF-FORMING RED ALGAE WOMERSLEYELLA SETACEA (HOLLENBERG) R. E. NORRIS ON SUBTIDAL SHORES OF RIJEKA BAY (NORTHERN ADRIATIC SEA)
Claudio BATTELLI University of Primorska, Faculty of Education of Koper, SI-6000 Koper, Cankarjeva 5 E-mail: claudio.battelli@guest.arnes.si
Milvana ARKO PIJEVAC
Natural History Museum Rijeka, HR-51000 Rijeka, Lorenzov prolaz 1, Croatia
ABSTRACT
Results of the study of subtidal macrobenthic flora, carried out in 1997 at Cape Ostro, Rijeka Bay, Croatia (northern Adriatic Sea), are presented. The investigation was based on seasonal sampling at different depths. Results indicated that the flora was strongly dominated by turf-forming algae. Overall, 37 macrobenthic algae (23 Rhodophycota or 62.2%, 6 Phaeophycota or 16.2% and 8 Chlorophycota or 21.6%) were identified. The invasive red filamentous alga Womersleyella setacea (Hollenberg) R. E. Norris was recorded for the first time in this area. The impact of massive development of the turf-forming algae on the structure of algal assemblages is discussed.
Key words: turf-forming algae, Womersleyella setacea, subtidal, northern Adriatic Sea, Rijeka Bay
SVILUPPO DI FELTRI DELL'ALGA ROSSA INVASIVA WOMERSLEYELLA SETACEA (HOLLENBERG) R. E. NORRIS NELL'INFRALITORALE DEL GOLFO DI FIUME
(ALTO ADRIATICO)
SINTESI
Vengono presentati i risultati di un'indagine condotta nel 1997 sulla flora macrobentonica nell'infralitorale nei pressi di Punta Ostro, Golfo di Fiume, Croazia (Alto Adriatico). Lo studio si basa su rilievi stagionali svolti a diverse profondita. I risultati indicano che la flora e costituita da densi feltri algali. Nel corso della ricerca sono state identifícate 37 specie di alghe macrobentoniche, di cui 23 Rhodophycota (62,2%), 6 Phaeophycota (16,2%) e 8 Chlorophycota (21,6%). Nel presente lavoro viene segnalata per la prima volta in quest'area la presenza dell'alga rossa filamentosa invasiva Womersleyella setacea (Hollenberg) R. E. Norris. Sono discusse le conseguenze dell'estesa dif-fusione di tali feltri sulla struttura delle comunita algali.
Parole chiave: feltri algali, Womersleyella setacea, infralitorale, Alto Adriático, Golfo di Fiume
INTRODUCTION
More than 90 taxa of marine algae are known to have been introduced into the Mediterranean Sea, mostly by human activities {i.e. aquaculture, pollution, ballast waters, fishing nets), and at least nine of them are considered invasive {Verlaque, 1994; Boudouresque & Verlaque, 2002). Some of the most invasive introductions took place in the last 10-15 years and have caused substantial changes in the structure of benthic algal assemblages. One of the best examples of this phenomenon is represented by the massive development of dense algal turfs produced by filamentous species, in particular the red alga Womersfeyeffa setacea {Hollenberg) R. E. Norris This species has been reported to produce thick turfs covering large portions of subtidal bottoms in several regions {Verlaque, 1989; Airoldi et af., 1995; Atha-nasiadis, 1997; Patzner, 1998). The uncontrolled growth of turfs is considered an indicator of disturbance in the environment, with a negative impact on biodiversity {Barth & Fagan, 1990; Morand & Briand, 1996).
Many non-indigenous species of algae have been recorded in the northern Adriatic Sea {Orlando Bonaca, 2001), mostly on the Italian shores. Among them, the brown Sargassum muticum {Yendo) Fensholt {Gargiulo et af., 1992) and Undaria pinnatifida {Harvey) Surigar {Rismondo et af., 1993), the green Codium fragife subsp. tomentosoides {Van Goor) P.C. Silva {Godini & Avanzini, 1988), Cauferpa taxifofia {Vahl) C. Agardh {Zuljevic & Antolic, 1998; Span et af., 1998), Ufva scan-dinavica Bliding {Battelli & Tan, 1998), and the red An-tithamnion pectinatum {Montagne) Brauner ex Athana-siadis et Tittley {Curiel et af., 1996) and Pofysiphonia morrowii Harvey {Curiel et af., 2002) are some of the most recent records. Comparatively, the eastern shores of the northern Adriatic Sea have not been severely affected by algal introductions so far. However, some algae reported elsewhere as highly aggressive invaders, such as C. taxifofia, Cauferpa racemosa var. cyfindracea {Sonder) Verlaque, Huisman & Boudouresque, {Verlaque, 1994) and W. setacea {Sartoni & Rossi, 1998), have been recently recorded.
In 1996, an extensive growth of turf-forming algae was noted in the sublittoral area around Cape Ostro, northeastern coast of Rijeka Bay, northern Adriatic Sea {Battelli & Arko Pijevac, 2003). The same phenomenon was subsequently recorded in other parts of Rijeka Bay, such as the Sepen cove and the submarine area of Sv. Marko islet {Jaklin & Arko Pijevac, 1997; Zahtila, 1999). Examination of samples collected in these areas indicated that algal turfs had been formed primarily by W. setacea. The ben-thic marine algae of the Kvarner Gulf have been studied sporadically {Munda, 1960; Rizzi Longo, 1972; Zavodnik et af., 1981; Zavodnik & Zavodnik, 1982; Zavodnik, 1992; Zavodnik et af., 1998) and no previous records of this phenomenon are available in the literature.
In this study, we report preliminary on the observations regarding the composition of algal assemblages, their bathymetric variation and the reproductive phenology of W. setacea in the area at Cape Ostro. The results presented constitute the first report on extensive development of algal turfs in the northern Adriatic and provide a background of knowledge that will be of great value for further investigations.
Fig. 1: Study area, Cape Oštro (north-eastern coast of Rijeka Bay).
SI. 1: Raziskovano območje, Rt Oštro (severovzhodna obala Reškega zaliva).
MATERIAL AND METHODS
The study was carried out near Cape Oštro (northeastern coast of Rijeka Bay) (43°16.152 N, 1433.792 E) in 1997 (Fig. 1). The morphology of the area's bottom varies with depth; the substratum consists of carbonate rocks (limestone and dolomites) between 0 and 5 m, a mixture of rock and sand between 5 and 10 m, sand between 10 and 15 m, and muddy sand below 15 m.
Samples were collected at different depths (5, 10, 15 and 20 m) and in each season. Overall, 36 samples (8 in winter, 8 in summer, 8 in autumn and 12 in spring) were collected. Algae were removed from 100 cm2 squares
and the percentage cover of each species was estimated for each date and for different depths (5 m, 10 m, 15 m and 20 m). The samples were preserved in 4% seawater-formalin solution and examined in the laboratory. The algal material is deposited in the Natural History Museum of Rijeka.
The algae were determined at the best possible level of taxonomic resolution; for W. setacea (Fig. 2), detailed observations of the reproductive phenology were also carried out. Algal nomenclature follows Ribera et al. (1992), Gallardo et al. (1993), and Gomez Garreta et al. (2001).
Fig. 2: Thallus of Womersleyella setacea (barr = 500 pm).
Sl. 2: Steljka vrste Womersleyella setacea (merilo = 500 pm).
RESULTS
Overall, 37 species of macrobenthic algae were identified (Tab. 1): 23 Rhodophycota (62.2%), 6 Phaeo-phycota (16.2%) and 8 Chlorophycota (21.6%).
At the time of the survey, the bottom of the surveyed area was colonized by macroalgal assemblages that appeared very poor in terms of species number. The investigated area was mostly colonized by turf-forming species overgrowing all types of substrata from 5 m to 20 m depth.
In terms of presence, the most common species were the green algae Chaetomorpha linum (O.F. Müller) Kützing and Cladophora nigrescens Zanardini ex Frauenfeld and the red alga Womersleyella setacea. The species C. linum dominated at a depth of 5 m, C. nigrescens at depths of 10 and 20 m, while the depth of 15 m was dominated by the red alga W. setacea (Tabs. 2, 3, 4, 5).
Tab. 1: Check list of macrobenthic algae at Cape Ostro (Rijeka Bay, northern Adriatic Sea). Tab. 1: Seznam vrst makrobentoskih alg pri Rtu Ostro (Reski zaliv, severno jadransko morje).
Rhodophycota_
Antithamnion cruciatum (C. Agardh) Nägeli_
Boergeseniella fruticulosa (Wulfen) Kylin_
Ceramium ciliatum (J. Ellis) Ducluzeau var. robustum
(J. Agardh) Feldmann-Mazoyer_
Ceramium tenerrimum (G. Martens) Okamura_
Champia parvula (C. Agardh) Harvey_
Chondria coerulescens (J. Agardh) Falkenberg_
Dipterosiphonia rigens (C. Agardh) Falkenberg_
Gelidium pusillum (Stackhouse) Le Jolis_
Haliptilon virgatum (Zanardini) Garbary et H. V.
Johansen_
Halopithys incurva (Hudson) Batters_
Herposiphonia secunda (C. Agardh) Ambronn f.
secunda_
jania rubens (Linnaeus) J. V. Lamouroux_
Laurencia sp._
Lophosiphonia obscura (C. Agardh) Falkenberg_
Nitophyllum punctatum (Stackhouse) Greville_
Polysiphonia atra Zanardini_
Polysiphonia breviarticulata (C. Agardh) Zanardini Polysiphonia opaca (C. Agardh) Moris & De Notaris
Polysiphonia polyspora (C.Agardh) Montagne_
Polysiphonia stuposa Zanardini ex Kützing_
Polysiphonia subulifera (C. Agardh) Harvey_
Spyridia filamentosa (Wulfen) Harvey_
Womersleyella setacea (Hollenberg) R. E. Norris
Phaeophycota_
Cystoseira corniculata (Turner) Zanardini_
Dictyota dichotoma (Hudson) J.V. Lamouroux var
dichotoma_
Dictyota fasciola (Roth) J.V.Lamouroux_
Halopteris filicina (Grateloup) Kützing_
Padina pavonica (Linnaeus) J. V. Lamouroux_
Sphacelaria cirrosa (Roth) C. Agardh_
Chlorophycota_
Chaetomorpha linum (O. F. Mueller) Kützin_
Cladophora coelothrix Kützing_
Cladophora laetevirens (Dillwin) Kützing_
Cladophora lehmanniana (Lindenberg) Kützing_
Cladophora nigrescens Zanardini ex Frauenfeld_
Cladophora prolifera (Roth) Kützing_
Ulva clathrata (Roth) C. Agardh_
Ulva laetevirens Areschoug_
In terms of percentage cover, the most abundant species were the green algae C. nigrescens and the red alga W. setacea. During the study, the abundance of C. nigrescens, at different depths, was generally higher than W. setacea, although the average cover percentage of these two species showed different trends during the seasons. The cover percentage of C. nigrescens increased from a depth of 5 m to a depth of 10 m and then markedly decreased to a depth of 20 m. The fluctuation of the cover percentage of the red algae W. setacea showed a different trend: it increased slightly from a depth of 5 m to 15 m and then decreased at a depth of 20 m (Fig. 3).
Seasonal fluctuation of the cover percentage values showed that at all depths (5 m, 10 m, 15 m, 20 m), the abundance of C. nigrescens decreased in general from the winter to the summer and then increased in the autumn, while the abundance of W. setacea slightly decreased from the winter to the autumn at all depths (Fig. 4).
In spite of frequent sampling, W. setacea was never observed in a reproductive state.
□ CI. nigrescens EW. setacea
I ^
		□ CI.	nigrescens
38.8	34.2		setacea
A
I 20-

5.9
Spring	Summer
Season
								
					43.8		43.8	
		15.0						
				6.7		2.5		2.5
		WW/.		vm				
C
Fig. 3: Percentage covers of C. nigrescens and W. setacea at different depths.
SI. 3: Odstotne pokrovne vrednosti vrst C. nigrescens in W. setacea na različnih globinah.
DISCUSSION
During the study, the invasive filamentous red alga W. setacea was recorded for the first time in Rijeka Bay. This species, originally described from a tropical locality and subsequently reported for other tropical regions, has recently become widespread in the Mediterranean Sea (Verlaque, 1989, 1994; Airoldi et a/., 1994; Rindi & Ci-nelli, 1995; Athanasiadis, 1997; Rindi et a/, 1999), and in the northern Adriatic Sea (Sartoni & Rossi, 1998).
The phenological observations suggest that the colonization of W. setacea proceeded by vegetative reproduction, which is so far the only form of reproduction known both in the field and in cultures of this species from various areas of the Mediterranean Sea (Airoldi et a/.,1995; Rindi et a/., 1999; Rindi & Cinelli, 2000).
		m	5.8		6.7					
		1			1		2.5	1.3 m\		1.3 W\
Fig. 4: Temporal fluctuation of mean cover of C. nigrescens and W. setacea at a depth of (A) 5 m, (B) 10 m, (C) 15 m and (D) 20 m.
Sl. 4: Sezonske variacije pokrovnih vrednosti vrst C. nigrescens in W. setacea na globini (A) 5 m, (B) 10 m, (C) 15 m in (D) 20 m.
The present results show that turfs of W. setacea can grow on all types of substratum (rock, sand and mud) and at different depths in the investigated area. Although W. setacea has been recorded in the Adriatic only re-
B
D
cently, the extensive development of this alga in Rijeka Bay reflects the fast and aggressive propagation already reported for the western Mediterranean Sea (Verlaque, 1989; Airoldi et a/., 1995; Athanasiadis, 1997; Rindi & Cinelli, 2000; Piazzi & Cinelli, 2001; Boudouresque & Verlaque, 2002).
Tab. 2: Algal species recorded in the study area at a depth of 5 m with average values*. (*Cover abundance values)
Tab. 2: Vrste alg na raziskanem območju na globini 5 m s pokrovnimi vrednostmi*. (*Vrednosti pokrovne gostote)
ln the course of the survey, large-sized erect algae appeared to be rare. The high dominance of the turf-forming algae might negatively affect the development of some erect species, such as Dictyota dichotoma (Hudson) J. V. Lamouroux, Dictyota fascio/a (Roth) J. V. Lam-ouroux, Padina pavonica (Linnaeus) J. V. Lamouroux and Cystoseira cornicu/ata (Turner) Zanardini. This is in agreement with the studies carried out in other regions of the Mediterranean, which have shown that the monopolization of substratum by turf-forming filamentous algae can prevent the development of other macroalgae by overgrowth and accumulation of sediment, making the settlement of spores and the survival of juvenile stages impossible and thus reducing species diversity and equi-tability (Airoldi et a/., 1995; Morand & Briand, 1996; Airoldi & Virgilio, 1998; Piazzi & Cinelli, 2001).
The present observations, however, are based on a relatively short sampling period and do not allow for a formulation of relevant conclusions on the impact of these algal turfs in Rijeka Bay. Observations in a longer temporal span and studies based on an experimental approach, as carried out for other parts of the Mediter-
Tab. 3: Algal species recorded in the study area at a depth of 10 m with average values*. (*see Table 2) Tab. 3: Vrste alg na raziskanem območju na globini 10 m s pokrovnimi vrednostmi*. (*glej Tabelo 2)
Species	Feb	Mar	Apr	May	Jun	Jul	Auj	Nov	Dec
A. cruciatum	0.0	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0
B. fruticulosa	15.0	2.5	2.5	0.0	0.0	15.0	0.0	2.5	0.0
C. ciliatum v. robustum	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1
C. coerulescens	15.0	2.5	2.5	2.5	0.0	0.0	0.0	2.5	0.0
C. laetevirens	0.0	0.0	0.0	0.0	15.0	0.0	0.0	0.0	2.5
C. tenerrimum	0.1	0.1	0.1	0.0	0.0	0.0	0.0	0.1	0.1
Ch. linum	0.1	2.5	0.1	0.1	2.5	0.1	0.1	0.1	0.1
Cl. coelothrix	0.0	2.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cl. lehmanniana	0.0	0.0	0.1	0.0	15.0	0.0	2.5	0.0	0.0
Cl. nigrescens	62.5	15.0	0.0	87.5	15.0	15.0	2.5	62.5	15.0
Cl. prolifera	0.1	0.1	0.1	2.5	0.0	2.5	0.0	2.5	0.0
Cy. corniculata	0.0	0.0	15.0	0.0	0.0	0.0	0.0	0.0	0.0
D. dichotoma	2.5	15.0	15.0	0.0	0.0	0.1	0.0	0.0	15.0
D. fasciola	2.5	0.1	0.1	0.0	15.0	0.1	15.0	2.5	15.0
D. rigens	0.0	0.0	2.5	0.0	2.5	2.5	15.0	2.5	0.0
G. pusillum	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0
H. filicina	0.0	0.1	0.0	0.0	0.0	2.5	0.0	0.0	0.0
H. incurva	0.1	0.1	0.0	0.0	0.0	0.0	0.0	0.1	0.0
H. secunda	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1
L. obscura	0.0	2.5	0.0	0.1	2.5	0.0	0.1	0.1	0.0
Laurencia sp.	0.0	0.0	15.0	2.5	15.0	15.0	15.0	15.0	0.0
N. punctatum	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0
P. atra	0.1	0.0	0.0	0.0	0.0	0.0	0.1	0.0	0.0
P. breviarticulata	0.0	0.0	2.5	0.1	0.1	2.5	2.5	2.5	0.1
P. opaca	0.1	2.5	0.0	0.1	0.1	0.0	0.1	2.5	0.0
P. polyspora	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	2.5
P. sertularioides	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1
P. stuposa	0.0	2.5	2.5	0.0	2.5	0.0	0.1	0.0	0.0
P. subulifera	0.0	15.0	2.5	0.0	0.1	0.0	0.0	0.0	2.5
S. filamentosa	0.0	0.0	0.0	0.0	0.0	0.0	2.5	0.0	2.5
Sp. cirrosa	0.1	0.1	0.0	0.0	2.5	0.1	2.5	2.5	0.0
W. setacea	0.1	15.0	15.0	0.0	2.5	0.1	2.5	0.0	2.5
*Cover abundance values / Vrednosti pokrovne gostote:
Class	% cover	Average values
+	<1%	0.1
1	1.1-5.0%	2.5
2	5.1-25.0%	15.0
3	25.1-50.0%	37.5
4	50.1-75.0%	62.5
5	75.1-100%	87.5
Species	Feb	Mar	Apr	May	Jun	Jul	AuJ	Nov	Dec
C. coerulescens	2.5	0.1	0.1	2.5	0.0	2.5	0.0	0.1	2.5
C. parvula	0.0	0.0	0.0	0.0	0.1	0.0	0.0	0.0	0.0
Ce. ciliatum v. robustum	0.0	0.0	0.0	0.0	2.5	0.0	0.0	0.0	0.0
Ce. tenerrimum	0.0	0.0	0.1	0.0	0.0	0.0	0.1	0.0	0.0
Ch. linum	0.1	2.5	0.0	0.1	0.1	0.1	0.1	0.1	0.1
CO. laetevirens	0.0	37.5	15.0	0.0	0.0	2.5	0.0	0.0	0.0
CO. lehmanniana	0.0	0.1	0.0	0.0	0.0	0.0	2.5	2.5	2.5
Cl. nigrescens	87.5	37.5	15.0	87.5	37.5	87.5	2.5	87.5	15.0
Cl. prolifera	2.5	0.0	0.0	0.0	2.5	2.5	2.5	0.0	0.5
Cy. corniculata	0.0	0.0	0.0	0.0	0.0	0.0	62.5	0.0	0.0
D. dichotoma	0.0	0.1	0.1	2.5	0.0	0.0	0.0	0.0	0.0
D. fasciola	0.0	2.5	0.0	2.5	0.0	0.0	15.0	0.0	2.5
D. rigens	2.5	0.1	0.1	0.0	0.0	0.0	2.5	0.0	2.5
G. pusillum	0.0	0.0	0.0	0.0	0.0	0.1	0.0	0.0	0.0
H. filicina	0.0	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0
H. incurva	0.1	0.1	0.0	0.0	0.0	0.1	0.0	0.1	0.0
L. obscura	0.0	2.5	0.1	0.0	0.0	0.1	0.0	2.5	0.0
Laurencia sp.	0.0	0.1	0.0	2.5	0.1	0.0	0.1	0.0	0.0
P. atra	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
P. breviarticulata	0.0	0.0	0.0	0.0	0.0	0.0	2.5	0.0	2.5
P. opaca	0.0	0.1	0.0	0.0	0.1	0.0	0.1	0.1	0.1
P. polyspora	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.0	0.0
P. sertularioides	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.0	0.0
P. stuposa	0.0	0.0	0.0	0.0	0.1	0.0	2.5	0.0	0.0
P. subulifera	0.0	0.0	2.5	0.0	0.1	0.0	0.0	0.0	2.5
S. filamentosa	0.0	0.0	0.0	0.0	0.0	0.0	2.5	0.0	0.0
Sp. cirrosa	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.0	0.0
W. setacea	2.5	15.0	15.0	0.1	2.5	0.0	2.5	0.0	0.0
Tab. 4: Algal species recorded in the study area at a depth of 15 m with average values*. (*see Table 2) Tab. 4: Vrste alg na raziskanem območju na globini 15 m s pokrovnimi vrednostmi*. (*glej Tabelo 2)
ranean, will be necessary to understand better the effects of the development of algal turfs. It is therefore very important that the scientific institutions continue to monitor the distribution and persistence of turfs of W. setacea and their effects on the structure of subtidal assemblages.
Tab. 5: Algal species recorded in the study area at a depth of 20 m with average values*. (*see Table 2) Tab. 5: Vrste alg na raziskanem območju na globini 20 m s pokrovnimi vrednostmi*. (*glej Tabelo 2)
Species	Feb	Mar	Apr	May	Jun	Jul	AuJ	Nov	Dec
B. fruticufosa	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.G	G.G
Ce. cifiatum v. robustum	G.G	G.G	2.5	G.G	G.G	G.G	G.G	G.G	G.G
Ch. finum	G.1	G.1	G.G	G.1	G.G	G.1	G.1	G.1	G.1
Cf. fehmanniana	G.G	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.1
Cf. nigrescens	15.G	2.5	G.G	15.G	2.5	2.5	2.5	2.5	15.G
Cf. profitera	2.5	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.G
D. dichotoma	G.G	G.G	2.5	G.G	15.G	G.1	G.1	G.1	G.G
D. rigens	G.1	G.G	G.G	G.G	G.1	G.1	G.1	G.1	G.G
H. fificina	15.G	G.G	G.G	G.G	G.G	G.G	G.G	G.G	G.G
H. incurva	G.G	G.G	2.5	G.G	G.G	G.G	G.G	G.G	G.G
H. secunda	G.G	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.G
Laurencia sp.	G.G	G.1	G.G	G.G	15.G	2.5	G.1	2.5	G.G
P. atra	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.G	G.G
P. pavonica	G.G	G.G	2.5	G.G	G.G	G.G	G.G	G.G	G.G
P. stuposa	G.G	G.1	G.1	G.G	G.G	G.G	G.G	G.G	G.G
S. cirrosa	G.1	G.G	2.5	G.G	2.5	G.1	G.1	G.1	G.G
U. cfathrata	G.G	G.G	G.1	G.G	G.G	G.G	G.G	G.G	G.G
W. setacea	2.5	15.G	2.5	15.G	2.5	2.5	G.G	G.G	2.5
ACKNOWLEDGEMENTS
We are grateful to Dr Fabio Rindi from the Martin Ryan Institute of Galway {Ireland) for his advice and help with the revision of the text. We wish to thank Dr Donatella Serio from the University of Catania {Italy) for her assistance in the determination of some algal species.
Species	Feb	Mar	Apr	May	Jun	Jul	Auj	Nov	Dec
B. fruticufosa	G.G	G.G	G.G	G.1	G.G	G.G	G.G	G.G	G.G
C. coerufescens	G.G	2.5	2.5	G.1	G.G	2.5	G.G	2.5	G.G
Ce. tenerrimum	G.G	G.G	G.G	G.G	G.G	G.G	G.1	G.G	G.G
Ch. finum	G.1	2.5	2.5	G.1	2.5	G.1	G.G	G.1	G.1
Cf. nigrescens	62.5	37.5	37.5	87.5	15.G	87.5	G.G	87.5	G.G
Cf. faetevirens	G.G	15.G	15.G	G.G	G.G	G.1	15.G	2.5	G.G
Cf. fehmanniana	G.G	G.G	G.G	G.G	2.5	G.G	G.G	G.G	2.5
Cf. profitera	2.5	G.1	2.5	2.5	G.1	G.G	G.G	G.G	G.1
Cy. cornicufata	G.G	G.G	G.G	G.G	G.G	G.G	37.5	G.G	G.G
D. dichotoma	G.G	G.1	G.G	G.1	G.G	G.G	15.G	G.G	G.G
D. rigens	G.G	G.1	G.G	G.G	G.G	G.G	2.5	G.G	2.5
H. incurva	G.1	2.5	G.1	G.G	G.1	G.G	G.G	G.G	G.G
L. obscura	2.5	2.5	G.G	G.G	G.1	G.G	G.G	G.G	G.G
Laurencia sp.	G.G	G.1	G.G	G.G	G.G	G.G	G.G	G.G	G.G
P. atra	2.5	G.G	G.G	G.G	G.G	G.G	G.G	G.G	G.G
P. opaca	G.G	G.1	G.1	G.1	G.1	G.1	G.1	G.1	G.1
P. sertufarioides	G.G	G.G	G.G	G.G	G.G	G.G	2.5	G.G	G.G
P. stuposa	G.G	G.G	2.5	G.G	G.G	G.G	G.G	G.G	G.1
P. subufifera	G.G	G.G	G.G	G.G	G.G	G.G	2.5	G.G	2.5
S. cirrosa	G.G	G.G	G.G	G.G	G.G	G.G	2.5	G.G	G.G
S. fifamentosa	G.G	G.G	G.G	G.G	G.G	G.G	2.5	G.G	G.G
W. setacea	15.G	15.G	15.G	2.5	2.5	2.5	2.5	2.5	2.5
POJAVLJANJE GOSTIH PREVLEK INVAZIVNE RDEČE ALGE WOMERSLEYELLA SETACEA (HOLLENBERG) R. E. NORRIS V INFRALITORALU REŠKEGA ZALIVA
(SEVERNO JADRANSKO MORJE)
Claudio BATTELLI Univerza na Primorskem, Pedagoška fakulteta Koper, SI-6000 Koper, Cankarjeva 5 E-mail: claudio.battelli@guest.arnes.si
Milvana ARKO PIJEVAC
Prirodoslovni muzej Rijeka, HR-51000 Rijeka, Lorenzov prolaz 1, Hrvaška POVZETEK
Članek obravnava rezultate raziskave morske makrobentoške flore alg infralitorala pri rtu Ostro, Reški zaliv (severno Jadransko morje). Študija, napravljena v letu 1997, temelji na sezonskem vzorčenju na različnih globinah (5, 10, 15 in 20 m). Rezultati kažejo, da je flora alg sestavljena predvsem iz gostih prevlek makrobentoških alg. Skupno je bilo določenih 37 alg, med katerimi je bilo 23 rdečih (62,2%), 6 rjavih (16,2%) in 8 zelenih (21,6%). Prikazana je časovna variacija pokrovnih vrednosti najbolj pogostih vrst (Cladophora nigrescens Zanardini ex Frauenfeld in
Womersleyella setacea (Hollenberg) R. E. Norris). V članku je prvič zabeleženo pojavljanje rdeče nitaste alge W. se-tacea na tem območju, ki se tu pojavlja na vseh globinah in v vseh letnih časih, vendar nikoli v fertilni obliki. Dosedanje študije o vrsti W. setacea so pokazale, da se vrsta v Sredozemskem morju razmnožuje vegetativno in hitro širi po vseh vrstah podlage; zato se ta alga prišteva k invazivnim vrstam. Članek obravnava tudi posledice masivnega pojavljanja gostih prevlek makrobentoških alg na sestavo združb alg.
Ključne besede: prevleke alg, Womersleyella setacea, infralitoral, severno Jadransko morje, Reški zaliv
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