Anali za istrske in mediteranske študije Annali di Studi istriani e mediterranei Annals for Istrian and Mediterranean Studies Series Historia Naturalis, 31, 2021, 1 UDK 5 Annales, Ser. hist. nat., 31, 2021, 1, pp. 1-164, Koper 2021 ISSN 1408-533X KOPER 2021 Anali za istrske in mediteranske študije Annali di Studi istriani e mediterranei Annals for Istrian and Mediterranean Studies Series Historia Naturalis, 31, 2021, 1 UDK 5 ISSN 1408-533X e-ISSN 2591-1783 ANNALES · Ser. hist. nat. · 31 · 2021 · 1 Anali za istrske in mediteranske študije - Annali di Studi istriani e mediterranei - Annals for Istrian and Mediterranean Studies ISSN 1408-533X UDK 5 Letnik 31, leto 2021, številka 1 e-ISSN 2591-1783 UREDNIŠKI ODBOR/ COMITATO DI REDAZIONE/ BOARD OF EDITORS: Alessandro Acquavita (IT), Nicola Bettoso (IT), Christian Capapé (FR), Darko Darovec, Dušan Devetak, Jakov Dulčić (HR), Serena Fonda Umani (IT), Andrej Gogala, Daniel Golani (IL), Danijel Ivajnšič, Mitja Kaligarič, Marcelo Kovačič (HR), Andrej Kranjc, Lovrenc Lipej, Vesna Mačić (ME), Alenka Malej, Patricija Mozetič, Martina Orlando- Bonaca, Michael Stachowitsch (AT), Tom Turk, Al Vrezec Glavni urednik/Redattore capo/ Editor in chief: Darko Darovec Odgovorni urednik naravoslovja/ Redattore responsabile per le scienze naturali/Natural Science Editor: Lovrenc Lipej Urednica/Redattrice/Editor: Martina Orlando-Bonaca Lektor/Supervisione/Language editor: Polona Šergon (sl.), Petra Berlot Kužner (angl.) 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Navodila avtorjem in vse znanstvene revije in članki so brezplačno dostopni na spletni strani https://zdjp.si/en/p/annalesshn/ The submission guidelines and all scientific journals and articles are available free of charge on the website https://zdjp.si/en/p/annalesshn/ Le norme redazionali e tutti le riviste scientifiche e gli articoli sono disponibili gratuitamente sul sito https://zdjp.si/en/p/annalesshn/ ANNALES · Ser. hist. nat. · 31 · 2021 · 1 Anali za istrske in mediteranske študije - Annali di Studi istriani e mediterranei - Annals for Istrian and Mediterranean Studies UDK 5 Letnik 31, Koper 2021, številka 1 ISSN 1408-53 3X e-ISSN 2591-1783 VSEBINA / INDICE GENERALE / CONTENTS 2021(1) BIOINVAZIJA BIOINVASIONE BIOINVASION Luca CASTRIOTA & Manuela FALAUTANO Reviewing the Invasion History of the Blue Crab Callinectes sapidus (Portunidae) in Sicily (Central Mediterranean): an Underestimated Alien Species ... Revizija zgodovine invazije modre rakovice Callinectes sapidus (Portunidae) na Siciliji (osrednje Sredozemsko morje): podcenjena tujerodna vrsta Alan DEIDUN, Bruno ZAVA, Maria CORSINI- FOKA, Johann GALDIES, Antonio DI NATALE & Bruce B. COLLETTE First Record of the Flat Needlefish, Ablennes hians (Belonidae) in Central Mediterranean Waters (Western Ionian Sea) ............................................. Prvi zapis o pojavljanju ploščate morske igle, Ablennes hians (Belonidae) v vodah osrednjega Sredozemskega morja (zahodno Jonsko morje) Mohamed Mourad BEN AMOR, Khadija OUNIFI-BEN AMOR, Marouène BDIOUI & Christian CAPAPÉ Occurrence of Reticulated Leatherjacket Stephanolepis diaspros (Monacanthidae) in the Central Mediterranean Sea, and New Record from the Tunisian coast ............. Pojavljanje afriškega kostoroga, Stephanolepis diaspros (Monacanthidae), v osrednjem Sredozemskem morju in prvi podatek za tunizijsko obalo Sara AL MABRUK, Ioannis GIOVOS & Francesco TIRALONGO New Record of Epinephelus areolatus in the Mediterranean Sea: First Record from Syria .......... Novi zapis o pojavljanju rdečepikaste kirnje (Epinephelus areolatus) v Sredozemskem morju: prvi podatki za Sirijo SREDOZEMSKI MORSKI PSI SQUALI MEDITERRANEI MEDITERRANEAN SHARKS Primo MICARELLI, Francesca Romana REINERO & Emilio SPERONE Notes on a Rare Case of Bluntnose Sixgill Shark Hexanchus griseus Stranded on the Coast of Tuscany in the Central Tyrrhenian Sea ................. Zapis o redkem primeru morskega psa šesteroškrgarja Hexanchus griseus, ki je nasedel na toskanski obali v osrednjem Tirenskem morju Alen SOLDO The Occurrence of the Common Angel Shark Squatina squatina in the Adriatic Sea ................... Pojavljanje navadnega sklata (Squatina squatina) v Jadranskem morju Hakan KABASAKAL, Deniz AYAS & Deniz ERGÜDEN Intentional Stranding of a Blue Shark, Prionace glauca (Carcharhiniformes: Carcharhinidae), in Pursuit of Prey ....................... Namerno nasedanje sinjega morskega psa, Prionace glauca (Carcharhiniformes: Carcharhinidae), med zasledovanjem plena Patrick L. JAMBURA, Julia TÜRTSCHER, Alessandro DE MADDALENA, Ioannis GIOVOS, Jürgen KRIWET, Jamila RIZGALLA & Sara A. A. AL MABRUK Using Citizen Science to Detect Rare and Endangered Species: New Records of the Great White Shark Carcharodon carcharias Off the Libyan Coast ........................ Uporaba ljubiteljske znanosti za pridobivanje podatkov o redki in ogroženi vrsti: novi podatki o pojavljanju belega morskega volka Carcharodon carcharias ob Libijski obali 51 1 9 23 37 31 17 45 ANNALES · Ser. hist. nat. · 31 · 2021 · 1 IHTIOLOGIJA ITTIOLOGIA ICHTHYOLOGY Sihem RAFRAFI-NOUIRA, Christian REYNAUD & Christian CAPAPÉ A New Record of Clinitrachus argentatus (Osteichthyes: Clinidae) from the Tunisian Coast (Central Mediterranean Sea)............................ Novi zapis o pojavljanju srebrnice Clinitrachus argentatus (Osteichthyes: Clinidae) iz tunizijske obale (osrednje Sredozemsko morje) Mauro CAVALLARO, Giovanni AMMENDOLIA, Ignazio RAO, Alberto VILLARI & Pietro BATTAGLIA Variazioni pluriennali del fenomeno dello spiaggiamento di specie ittiche nello stretto di Messina, con particolare attenzione alle specie mesopelagiche .............................................. Večletne spremembe v nasedanju ribjih vrst v Mesinski ožini s posebnim ozirom na mezopelaške vrste Sihem RAFRAFI-NOUIRA, Christian REYNAUD & Christian CAPAPÉ Skeletal and Pughead Deformities in the Saddle Bream Oblada melanura (Osteichthyes: Sparidae) from the Tunisian Coast (Central Mediterranean Sea) ... Deformacije skeleta in glave pri črnorepki, Oblada melanura (Osteichthyes: Sparidae) iz tunizijske obale (osrednje Sredozemsko morje) Murat BILECENOGLU & Seydi Ali DOYUK Uncommon Thermophilic Fishes from the Marmara and Black Seas ............................ Nenavadne toploljubne ribe iz Marmarskega in Črnega morja Christian CAPAPÉ, Adib SAAD, Ahmad SOLAIMAN, Issa BARAKAT & Waad SABOUR First Substantiated Record of Armless Snake Eel Dalophis imberbis (Osteichthyes: Ophichthidae) from the Syrian Coast (Eastern Mediterranean Sea) ... Prvi dokumentiran primer pojavljanja kačaste jegulje, Dalophis imberbis (Osteichthyes: Ophichthidae), vzdolž sirske obale (vzhodno Sredozemsko morje) Khaled RAHMANI, Fatiha KOUDACHE, Amaria Latefa BOUZIANI & Alae Eddine BELMAHI Length-Weight Relationships and Metric Characters of the Atlantic Horse Mackerel, Trachurus trachurus (Perciformes: Carangidae), Caught in Béni-Saf Bay, Western Mediterranean (Algeria) ................................ Odnos med dolžino in maso in metrični znaki navadnega šnjura, Trachurus trachurus (Perciformes: Carangidae), ujetega v zalivu Béni-Saf, zahodno Sredozemsko morje (Alžirija) Tülin ÇOKER & Okan AKYOL On the Occurrence of Pomadasys incisus (Haemulidae) in the Turkish Aegean Sea (Eastern Mediterranean Sea) ..................................... O pojavljanju vrste Pomadasys incisus (Haemulidae) v turškem Egejskem morju (vzhodno Sredozemsko morje) Sihem RAFRAFI-NOUIRA, Mohamed Mourad BEN AMOR, Khadija OUNIFI-BEN AMOR, Marouène BDIOUI & Christian CAPAPÉ First Substantiated Record of Opah, Lampris guttatus (Osteichthyes: Lamprididae), from the Tunisian Coast (Central Mediterranean Sea)........ Prvi dokumentiran zapis o pojavljanju svetlice, Lampris guttatus (Osteichthyes: Lamprididae), iz tunizijske obale (osrednje Sredozemsko morje) FLORA FLORA FLORA Claudio BATTELLI & Marcello CATRA First Report of Cystoseira aurantia (Sargassaceae, Fucophyceae) from the Lagoon of Strunjan (Gulf of Trieste, Northern Adriatic) ............................ Prvo poročilo o vrsti Cystoseira aurantia (Sargassaceae, Fucophyceae) v strunjanski laguni (Tržaški zaliv, severni Jadran) Amelio PEZZETTA Le Orchidaceae di Pinguente (Buzet)........................ Kukavičevke Buzeta FAVNA FAVNA FAVNA Ahmet ÖKTENER & Ivan SAZIMA Caligus minimus (Copepoda: Caligidae) Parasitic on the Gills of a Remora Echeneis naucrates Attached to a Seabass Dicentrarchus labrax in Köyceğiz-Dalyan Lagoon Lake, Aegean Sea, Turkey .................................................. Caligus minimus (Copepoda: Caligidae), zajedavec na škrgah prilepa (Echeneis naucrates), pritrjenega na brancina (Dicentrarchus labrax) v laguni Köyceğiz-Dalyan v Egejskem morju, Turčija Kazalo k slikam na ovitku .................................... Index to images on the cover ............................... 159 165 165 139 129 63 69 95 101 147 123 107 85 ANNALES · Ser. hist. nat. · 31 · 2021 · 1 139 received: 2021-04-20 DOI 10.19233/ASHN.2021.17 FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN (GULF OF TRIESTE, NORTHERN ADRIATIC) Claudio BATTELLI Frane Marušič 4, 6310 Izola, Slovenia e-mail: claudio.battelli@guest.arnes.si Marcello CATRA Laboratory of Phycology, Department of Biological, Geological and Environmental Sciences, University of Catania, Via Empedocle 58, 95128 Catania, Italy e-mail: m.catra@unict.it ABSTRACT The authors report the first record of the brown alga Cystoseira aurantia Kützing, found in the Stjuža Lagoon of Strunjan (Gulf of Trieste, Slovenia). During field surveys conducted in March 2021, dense free-floating hanks of this alga were observed on the water’s surface along the eastern margins of the lagoon, at depths not exceed- ing 0.5 m. These acropleustophytic hanks were composed of abundantly branched single thalli and fragments of thalli firmly intertwined and entangled. Branches of every order were cylindrical, slender (1‒2 mm in diameter), omnidirectional, with no leafy branchlets or thorny appendages. No fertile specimens were found. Among the possible factors leading to the formation of free-floating masses of C. aurantia, mechanic processes due to a constant water movement under the action of winds and tidal currents were considered. The habitat and the morphological characters of the specimens studied are described. Key words: Cystoseira aurantia, Stjuža lagoon Strunjan, Slovenia, northern Adriatic PRIMA SEGNALAZIONE DI CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) NELLA LAGUNA DI STRUGNANO (GOLFO DI TRIESTE, ALTO ADRIATICO) SINTESI Gli autori riportano la prima segnalazione dell’alga bruna Cystoseira aurantia Kützing, trovata nella Laguna Schiusa di Strugnano (Golfo di Trieste, Slovenia). Durante le indagini sul campo, condotte nel marzo 2021, sono state osservate delle dense masse di quest’alga fluttuanti sulla superficie dell’acqua lungo il margine orientale della laguna, a profondità non superiore a 0,5 m. Le masse acropleustofitiche liberamente flottanti in superficie, si pre- sentano composte da singoli talli abbondantemente ramificati e saldamente intrecciati. Non sono stati riscontrati esemplari fertili. Tra i possibili fattori responsabili della formazione delle masse fluttuanti di C. aurantia, assume un carattere particolarmente rilevante la costante variazione delle correnti superficiali, all’interno della Laguna, dovuta alla marea. Vengono descritti l’habitat e i caratteri morfologici degli esemplari studiati. Parole chiave: Cystoseira aurantia, laguna Schiusa Strugnano, Slovenia, Alto Adriatico ANNALES · Ser. hist. nat. · 31 · 2021 · 1 140 Claudio BATTELLI & Marcello CATRA: FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN ..., 139–146 INTRODUCTION The brown alga Cystoseira aurantia (Sargassaceae, Fucophyceae) is a perennial free-living species forming free-floating hanks. Since its description by Kützing (1843), based on specimens collected in 1835 at the Gulf of Trieste (type locality), it has been reported from both Black Sea and Mediterranean coastal areas. In the latter area, it was repor- ted from the Balearic Islands (Spain) (Ribera et al., 1996), the Adriatic Sea (Giaccone 1978; Ribera et al., 1992; Taskin et al., 2012), Corsica (France) (Taskin et al., 2012), Sardinia, Sicily, and Tuscany (Italy) (Ribera et al., 1992; Furnari et al., 1999; Rindi et al., 2002; Taskin et al., 2012), Turkey (Taskin et al., 2012), the Bay of Cadiz (Spain) (Gallardo et al., 2016), Tunisia (Bouafif et al., 2016), and more recently from the Mediterranean coast of Morocco (Ramdani et al., 2021). The species, reduced to a form of C. barbata (Stackhouse) C. Agardh [= Gongolaria barbata (Stackhouse) Kuntze] by Giaccone in Amico et al. (1986) as C. barbata f. aurantia (Kützing) Giaccone, was recently reinstated as a distinct species by Orellana et al. (2019). According to literature, C. aurantia was reported from the northern Adriatic Sea by Giaccone (1974) as C. barbata C. Agardh var. aurantia (sic!); from Ferrara by Amico et al., [1986, as C. barbata (Goodenough & Woodward) J. Agardh f. aurantia (Kützing) Giaccone]. Gómez Garreta et al. (2001) considered C. barbata f. aurantia to be synonymous with C. barbata f. repens Zinova & Kalugina, but erroneously so, since the former form takes precedence over the latter (Cormaci et al, 2012). Interestingly, there are no records of this species from the eastern Adriatic Sea (Antolić et al., 2010), except that from the Middle Adriatic Sea (the Island of Palagruža) by Giaccone (1978). In this paper, we report the occurrence of C. aurantia from the Stjuža marine lagoon of Strunjan (Slovenia). It represents the first record of this species from Slovenian coastal waters. MATERIAL AND METHODS Study area The Strunjan Lagoon is a shallow, semi-enclosed oligotro- phic brackish coastal lagoon situated in the eastern part of the Strunjan Bay (45°31’30” N, 13°36’20” E) (Figs. 1a–1b), about 10 hectares in surface area and divided into two sub-basins: a smaller discharge lagoon and the larger Stjuža Lagoon. Geologically, it represents a large area of the Late-Glacial and Holocene estuary of the Strunjan stream, formed during the last transgression of the sea into that area (Šmuc, 2020). It is the only Slovene marine lagoon, and not entirely natural. For about half a century it has been an abandoned fish farm. The newly created lagoon has remained connected with the sea only by an entrance channel of about 20 meters in width and 5‒6 meters in depth, and three much smaller tidal channels (Fig. 1b), which allow for a better circulation of water masses in the lagoon and a reduced organic pollutant load (Avčin et al., 1973; Avčin et al., 1974; Vrišer, 2002). The Stjuža Lagoon is characterised by Cymodocea nodosa (Ucria) Ascherson and Zostera noltei Hornemann meadows on its margins. It is mostly very shallow, with some of its areas breaking the surface at the lowest tide (Šajna & Kaligarič, 2005; Lipej et al., 2019). Seagrass meadows host a diverse lagoon fish fauna and demersal invertebrates (Avčin et al., 1973; Šajna & Kaligarič, 2005; Lipej et al., 2019). Fig. 1: a) Maps of the study area; b) Stjuža Lagoon of Strunjan, indicating sampling site of Cystoseira aurantia (black circles), and the direction of seawater currents during the tide (after Avčin et al., 1973). The yellow arrows indicate the output flow, the red arrows the entry flow. Sl. 1: a) Karta raziskovalnega območja; b) Laguna Stjuža Strunjan z vzorčevalnimi postajami alge Cystoseira aurantia (črni krogci), in smer toka morske vode med plimovanjem. Rumene puščice predstavljajo smer izhoda in rdeče smer vhoda morske vode med bibavico (po Avčin et al., 1973). ANNALES · Ser. hist. nat. · 31 · 2021 · 1 141 Claudio BATTELLI & Marcello CATRA: FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN ..., 139–146 Today, the lagoon area is an important part of the Strunjan Stjuža Nature Reserve, falling within the Natura 2000 network, the primary objective of which is to pre- serve biodiversity. The study area is also characterised by the presence of a diverse fish fauna, demersal invertebrates closely associated with the environment of seagrasses: numerous molluscs (bivalves, gastropods), benthic crustaceans (mysids, amphipods, decapods, isopods), echinoderms (brittlestars, starfishes), and many species of polychaetes. Recently a total of 15 macroalgal taxa, both substrate- -attached and free-floating, were recorded (Lipej et al., 2004; 2019; Battelli & Gregorič, 2020). Environmental parameters Because of its shallow depth (only about 0.5–1 m), the thermal conditions in the Stjuža Lagoon seasonally move from one extreme to the other: ranging between 5 ºC and 10 ºC in wintertime and between 24 ºC and 27 ºC during the summer; during the other seasons the water temperatures are similar to the atmospheric temperatures. The salinity, oxygen content, and thermal conditions in the Stjuža Lagoon are related to the large water exchange and usually similar to those of Strunjan Bay (Avčin et al., 1973). The lagoon receives freshwater inputs through small canals from agri- cultural areas (Vrišer, 2002). The average tidal amplitude is 67 cm, with high tide 35 cm above mean sea level, and low tide 31 cm below mean sea level (Slovenian Environment Agency (ARSO): (www.arso.gov.si/water/sea; http://www. arso.gov.si/vode/podatki/amp/H9350_g_1.html). Sampling procedure and data analysis The fieldwork was carried out in March 2021, when dense free-floating hanks of Cystoseira aurantia were ob- served in the lagoon. The study was conducted along the eastern margins of the lagoon, as showed in Fig. 1b, since this was the only site where free-floating aggregates of the studied alga occurred in high abundance. The substrate of the research site consisted of a soft sediment composed of compact-fine argillaceous silt with a slight admixture of sand, with a thin (0.5–1 cm) yellowish brown layer of flocculent organic detritus (Vrišer, 2002; Šmuc, 2020). The salinity, pH, oxygen content (O2), and water temperature were measured in the Stjuža Lagoon and Strunjan Bay, using a Hanna HI98194 multiparameter waterproof meter. Ten thalli of C. aurantia were randomly collected during the sampling period. Fresh samples were manually collect- ed at the survey site, immediately placed in plastic bags containing water, and transported to the Laboratory of the Faculty of Mathematics, Natural Sciences and Information Technologies (FAMNIT) of Koper for further observation. Some samples were dried, pressed, and preserved in the personal herbarium of one of the authors (C.B.). The algal material collected was carefully sorted and examined using an Olympus SZ61 stereo microscope with a XC50 digital camera for morphological observation and measurements. The following measurements were carried out: thallus length from the basal part to the apex; length and diameter of main axes; length and diameter of primary axes. The occurrence of aerocysts, their length, diameter, and position, were recorded. The different positions of the conceptacles were described; in addition, the sizes of the ostioles of the conceptacles present either along the thalli or on aerocysts, were measured. The averages of all the conducted measure- ments were calculated. Species were identified based on papers by Maggs & Hommersand (1993), Bressan & Babbini (2003), Brodie et al. (2007), Sfriso (2010), Cormaci et al. (2012, 2014). The nomenclature follows Guiry & Guiry (2021). RESULTS AND DISCUSSION Samples of Cystoseira aurantia were collected in the eastern part of the Stjuža Lagoon (Fig. 1b), the only site of its occurrence. The alga was found unattached on the mobile substrate, between 0 and 0.5 m depth, forming a free-flo- ating hank of thalli of various shapes and sizes (Fig. 2a). These aggregates were composed by abundantly branched fragments of the alga, firmly intertwined and dispersedly arranged. Individual thalli in the aggregations were entan- gled with each other; consequently, branches growing in different directions (Fig. 2b) were observed within the hank. Morphological characteristics of Cystoseira aurantia The axes were cylindrical, reaching up to 20.77 cm in length, and 1.0 mm in diameter. The alga was white-brown in colour, non-iridescent; holdfast absent; primary branches cylindrical, without thorny appendages, up to 7.21 cm long and 0.9 mm in diameter; secondary branches cylindrical, without spinose appendages; ultimate branches filiform. In some thalli abundant aerocysts occurred, fairly regularly arranged on the branches, ovoid, 6.68 mm long and 1.73 mm in diameter, isolated or in short series of 2‒3 (Fig. 2c). Cryptostomata were abundant in all branches. The ostioles of the conceptacles present along the branches were fusi- form, 0.23 mm long and 0.09 mm width, with a l/w ratio of 2.64, while those on aerocysts were more ovoid, 0.22 mm long and 0.14 mm width, with a l/w ratio of 1.62 (Tab. 1). Despite the large number of conceptacles present on the thalli, the specimens examined were still infertile; in fact, we observed no sexual cells within the conceptacles. Our specimens agree well with previous descriptions and illustrations of the taxon (Cormaci et al., 2012; Bouafif et al., 2016; Ramdani et al., 2021). Algal vegetation in the Stjuža Lagoon In the Stjuža Lagoon, many algal species were present in both attached and unattached forms. C. aurantia was always present in free-floating form. It was collected mainly between ANNALES · Ser. hist. nat. · 31 · 2021 · 1 142 Claudio BATTELLI & Marcello CATRA: FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN ..., 139–146 the water surface and 0.5 m of depth and over soft substrate. The soft bottom is clearly unsuitable for the development of a highly diverse attached macroalgal vegetation. The spatial formation of free-floating hanks of C. aurantia (Fig. 2a) was probably owed to an accumulation and aggregation of many intertwined thalli caused by winds and tidal currents flowing during the tidal switch, as illustrated in Fig. 1b, where the yellow and red arrows indicate, respectively, the outflow and inflow of seawater during the change of tides. According to Fritsch (1965) and Smith (1950), the phenomenon of the aggregation of free-floating algae can be considered the result of a dynamic action of the waves’ motion caused by winds or water currents. Pleustophyte populations, typical of lagoon enviro- nments of the Mediterranean Sea, are mainly characterised by Valonia aegagropila C. Agardh, Rytiphlaea tinctoria (Clemente) C. Agardh, Lychaete echinus (Biasoletto) Wynne, and Chaetomorpha linum (O.F. Müller) Kützing (Calvo et al., 1980; Orestano & Calvo, 1985; Cecere et al., 1992). The most abundant unattached algal species found in the Stjuža Lagoon were green algae of the genus Ulva, U. rigida C. Agardh, and U. australis Areschoug. Together with Enteromorpha-type forms of Ulva (U. compressa Linnaeus and U. intestinalis Linnaeus), Chaetomorpha linum (O.F. Müller) Kützing, Lychaete echinus, Cladophora lehmanni- ana (Lindenberg) Kützing, and C. liniformis Kützing, they formed mostly unattached aggregates. Some red algae, such as Ceramium sp., Polysiphonia sp., and Polysiphonia spinosa (C. Agardh) J. Agardh, were also present. The long thallus in the free-floating form of C. aurantia facilitates the formation of dense aggregations and consequently the colonisation of the lagoon habitat. Some species of macroalgae were found as epiphytes on the thalli of C. aurantia, but they were very rare. Among them we observed Ceramium spp., Titanoderma pustulatum (J.V. Lamouroux) Näegeli, Cladophora spp, and Cladosiphon zosterae (J. Agardh) Kjlin. We did not observe any species of invertebrates within C. aurantia free-floating hanks, except for a single occurrence of Asterina gibbosa (Pennant, 1777). Water quality of the Stjuža Lagoon of Strunjan Judging from the information available for other parts of the Mediterranean, we believe that certain environmental conditions characteristic of the Stjuža Lagoon favour the formation of free-floating forms of C. aurantia, namely: (i) shallowness (an average depth of about 0.5–1 m), which allows for continuous exposure to sunlight and, consequently, the growth of algal thalli in all directions; (ii) superficial and bottom water cur- rents produced by winds blowing from the North-North- -East (bora) and from the South-East (sirocco); (iii) a wide tidal range of about 67 cm; and (iv) a soft sedimentary bottom unfavourable to the development of attached macroalgae. During the sampling period, the values of salinity, temperature, and pH of the sampling site were very simi- lar to those of the open sea (Strunjan Bay), while greater differences were observed when comparing the oxygen values of the sampling site (9.98 ppm) with those of the waters of the Strunjan Bay (12.08 ppm) (Tab. 2). The results obtained from our measurements are prevalently in agreement with those obtained in previous studies (Avčin et al., 1873; Vrišer, 2002; Lipej et al., 2019). C. aurantia clearly thrives as the lagoon ecosystem conditions improve, possibly because of its sensitivity to water quality and the hydrodynamic environment. The eastern part of the Stjuža Lagoon, where that alga is most common, is probably least exposed to less favourable environmental conditions and displaying conditions very similar to those of the water of Strunjan Bay (Tab. 2). The connections with the sea through the entrance and the tidal channels, favouring water circulation, have probably facilitated the colonisation and spread of C. aurantia. Also, since this alga is unattached, water circulation patterns in the lagoon undoubtedly influence its distribution towards the eastern part of the Stjuža Lagoon. On the other hand, the sea connections ensure a better circulation of water masses in the lagoon and reduced organic pollution. Fig. 2: a) Free-floating hanks of alga in the natural habitat; b) habit of Cystoseira aurantia; c) aerocysts isolated and in short series, indicated by arrows. Sl. 2: a) Prosto plavajoči skupki alge v naravnem okolju); b) steljka alge Cystoseira aurantia; c) posamezne aerociste in v zaporedju, označene s puščicami. ANNALES · Ser. hist. nat. · 31 · 2021 · 1 143 Claudio BATTELLI & Marcello CATRA: FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN ..., 139–146 Impact on the environment Information on the presence in the Stjuža Lagoon of brown algae, which indicates a good status of water, are very scarce. From literature data, a total of 15 macroalgal taxa, attached and free-floating, were recorded in the lagoon (Lipej et al., 2004, 2019; Battelli & Gregorič, 2020). Most of the macroalgal species found by Lipej et al. (2019) are ESG II class (Orfanidis et al., 2011) and as such not indicative of good ecological status. From papers in Lipej et al. (2004) and Lipej et al. (2019) it results that brown algae Cystoseira com- pressa (Esper) Gerloff & Nizamuddin and Fucus virsoides J. Agardh, both indicators of good ecological status, were at times present in the Stjuža Lagoon, but we did not encounter those species during our study. It is interesting to note that F. virsoides disappeared from the entire Slovenian coast a few years ago due to reasons still unknown (Battelli, 2016). Or- lando-Bonaca & Rotter (2018) observed a certain regression of Cystoseira species in recent years in the coastal waters of Slovenia. Recently, Battelli and Gregorič (2020) reported the occurrence of Cystoseira foeniculacea (Linnaeus) Greville f. tenuiramosa (Ercegović) Gómez Garreta, Barceló, Ribera et Rull Lluch in the lagoon, attached to hard substrata and as epiphyte on a ball-like form of Rytiphlaea tinctoria, which is certainly evidence to the species diversity of the lagoon. Unfortunately, up to now, there have been no studies about the ecological conditions that could somehow expla- in the occurrence of C. aurantia in the lagoon. Further inve- stigation regarding the causes that have led to the presence of only two species of Cystoseira is desirable and necessary. The present observations were limited to a single sam- pling period. Unfortunately, we did not have additional data on the environmental conditions that may have favoured the unusual formation of the free-floating form of this brown alga in the Stjuža Lagoon of Strunjan. Our assumptions are based exclusively on the observations made during the short research period and the study of the available literature. It is therefore evident that further investigations, repeated in time, will be necessary for a deeper understanding of this phenomenon. CONCLUSIONS On the basis of the cited literature and observations made during this study, we suppose that the formation of the free-floating forms of the unattached brown alga Cystoseira aurantia in the Stjuža Lagoon of Strunjan may be a consequence of (i) mechanic processes due to a consistent movement of water under the action of winds and tidal currents between high and low tides, and (ii) characteristics intrinsic to the species which allow the growth of the thallus in any direction and thereby an ever-changing exposure to light. ACKNOWLEDGEMENTS We would like to thank several individuals who helped with the present study. We are particularly grateful to the director and the staff of Public Institute Landscape Park Strunjan (Slovenia), for allowing us to carry out the research. To Bojana Lipej from Škocjanski zatok Nature Reserve, who helped us during the measurements of physical and chemical parameters of the Lagoon. Special thanks to Pro- fessor Giovanni Furnari from the Laboratory of Phycology, Department of Biological, Geological and Environmental Sciences, University of Catania, whose valuable suggestions made a substantial contribution to the manuscript. Tab. 1: Average values of some morphological measurements of brown alga Cystoseira aurantia from the Stjuža Lagoon of Strunjan. Tab. 1: Povprečne vrednosti nekaterih morfoloških meritev pri rjavi algi Cystosera aurantia iz Lagune Stjuža v Strunjanu. Thallus Primary branches Aerocysts Ostioles of conceptacles along the branches Ostioles of conceptacles on aerocysts length/ cm diam./ mm length/ cm diam./ mm length/ cm diam./ mm length/ cm diam./ mm ratio l/w length/ cm diam./ mm ratio l/w mean 20.77 1.00 7.21 0.90 6.68 1.73 0.23 0.09 2.64 0.22 0.14 1.62 stdev 7.46 0.11 2.59 0.13 0.96 0.18 0.02 0.02 0,55 0.02 0.01 0.25 Tab. 2: Comparisons among the values of salinity, tempe- rature, pH and oxygen recorded at the sampling site and in Strunjan Bay during the sampling period (March 2021). Tab. 2: Primerjava vrednosti slanosti, temperature, pH in kisika na vzorčevalni postaji in v Strunjanskem zalivu, v obdobju vzorčenja (marec 2021). Location salinity T (°C) pH O2 (ppm) Stjuža lagoon 34.00 19.64 7.87 9.98 Strunjan bay 34.46 15.05 8.25 12.08 ANNALES · Ser. hist. nat. · 31 · 2021 · 1 144 Claudio BATTELLI & Marcello CATRA: FIRST REPORT OF CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) FROM THE LAGOON OF STRUNJAN ..., 139–146 PRVO POROČILO O VRSTI CYSTOSEIRA AURANTIA (SARGASSACEAE, FUCOPHYCEAE) V STRUNJANSKI LAGUNI (TRŽAŠKI ZALIV, SEVERNI JADRAN) Claudio BATTELLI Frane Marušič 4, 6310 Izola, Slovenia e-mail: claudio.battelli@guest.arnes.si Marcello CATRA Laboratory of Phycology, Department of Biological, Geological and Environmental Sciences, University of Catania, Via Empedocle 58, 95128 Catania, Italy e-mail: m.catra@unict.it POVZETEK Avtorja poročata o pojavu rjave alge Cystoseira aurantia iz morske lagune Stjuža v Strunjanu (Tržaški zaliv, severni Jadran), ki predstavlja prvi zapis o tej vrsti v obalnem morju Slovenije. Študija je bila izvedena marca 2021, na vzhodnem delu lagune, kjer je bila ugotovljena večja gostota prosto plavajočih prepletenih mas te alge, na globini, ki ni presegala 0,5 m. Opisani so življenjski prostor, morfološki znaki preučenih vzorcev. Ugotovljeno je bilo, da je mehko dno lagune očitno ugodno za razvoj nepritrjene vegetacije alg, katerih predstavnik je C. aurantia. Avtorja domnevata, da je nastanek prosto plavajočih mas te alge v Strunjanski laguni Stjuža mogoče razlagati kot posledico dinamičnega delovanja valov zaradi vetrov in plimskih tokov ter kot rezultat aktivne vloge alge, ki omogočajo rast steljke v vse smeri, saj nima pritrdilnih struktur, in s tem nenehno spreminja izpostavljenost svetlobi. 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