ANNALL-S • Ser. hist. nat. • 13 • 2003 ■ 1 • Supplement short scientific article L'DK 639.3/ 5:504.064(262.3-18) received: 2003-09 05 SUSPENDED BfOFILTERS: SUCCESSION OF FOULING COMMUNITIES IMMEDIATELY ADJACENT TO A FISH CAGE AND CONTROL LOCATION Aieksandra f RUMEN, Bonn VRISER & Alenka MALE J National institute of Biology, Marine Biology Station, 51-6330 Piran. fornace 41 E-mail: rnalej@iribss.org ABSTRACT Biofouling succession on the suspended artificia! surfaces was studied in the Bay of Piran (northern Adriatic.) near a fish farm and at the control location. The novel fouling community was analysed qualitatively and quantitatively. Initially, benthic Algae colonized the artificial surfaces and dominated fouling community near the fish cage; Algae, Bryozoa and Hydroidea prevailed on control site surfaces, l ater succession-settlers were mostly suspension-feeders (hydroids, bivalves;, polychaete worms, bryozoans, ascidians), which occupied the artificial surfaces on both sites. After five months, the surfaces were overgrown predominantly by the bryozoan Schizobrachiella sanguínea, which was later replaced by the serpulid polychaetes (mainly Serpula vermicularis). Key words: biofouling, successions, fish farm, Adriatic Sea BIOFiLTRI SOSPES!: SUCCESSION! DI COMUNITA Dl FOULING ÍMMEDIATAMENTE ADIACENTI GABBIE Dl PESO E SITI DI CONTROLLO SINTESI Nell a baia di Pírano (Adriático settentrionale) sono state studiate successioni di bio-fouling su superifici artificial/ sospese in prosslmita dl un atlevamento di pesci e di un sito di controllo. Le neo-comunita di fouling sono state ana lizzate sía qualitativamente che quantitativamente. Durante un primo stadio alghe bentoniche hanno coionizzato le superfici artificial! e dominate ia comunita del fouling prossima alia gabbia di pesci. Sulle superfici del sito di controllo sono prevalsi alghe, briozoi ed idrozoi. In fast successive le supertlci di entrambi i sití sono state colonizzate da organismi filtratori (idrozoi, bivalvi, policheti vermiformi, briozoi, ascidiacei). Dopo cinque rnesi te superfici era-no ricoperte in prevalenza dal briozoo Schizobrachiella sanguínea, successivamente sostituito da policheti serpultdi (principalmente Serpula vermicularis). Parole chiave; bio-fouling, successions allevamento di pesci, Mare Adriático 39 ANNAl.tS • Ser. hist. nat. • 13 • 2003 • 1 • Supplement AM ;..milr.i FRMMtfj ♦< SUSIWOCP BOfllTmS: SUCCFSSIONOF rOUtlNC COMMUNIIIFS IMMlT)lAlK V aDJACIW TO A fish CAO!: . . 21-2* INTRODUCTION As a rule, pollution originating from open water risJi farming exceeds the local purifying capacity of the marine environment. Several solutions were proposed to reduce fish farm impacts and to enhance the auto-purifying capacity of the sea, such as deployment of artificial reefs (review in Spanter & Angel, 1999; Angel, 2001; Black et al., 2001; Hughes, 2001). To provide surface for bio-fouling community that would enhance natural uptake of the fish farm wastes we deployed suspended artificial structures near fish cages in the moderately eutrophic Bay of Pi ran (northern Adriatic). Attached flora and fauna are assumed to utilise dissolved and particulate wastes released by farmed fish depending on the structure of the fouling community. Therefore, a study was carried out on succession of fouling communities on suspended structures in the Immediate vicinity of fish cages compared to control location. MATERIALS AND METHODS Our study was conducted in the Bay of Piran (see figure 1 in Malacic & Forte, this volume) where two fish farms produce about 100 tons of European sea bass (Mo-rone /abrax) and giithead seabream tSparus aura (us J annually. The artificial structures consist of plastic mesh (2 x 2 cm openings) roiled into cylindrical bio-filters (BFs) with a total surface of 0.5 m", supporting the frames, floats and anchor weights (Plate I: Fig. 2). We deployed four arrays consisting of 11 BFs at each location (close to fish farm and control) {Plate I: Fig. 1} at depths ranging from 5 to 11 m. Field surveys of BF and removal for laboratory analysis were carried out 3-4 times yearly from 2001 to 2003. BFs were photographed under water and then removed for further laboratory analysis consisting oi taxonomic analysis of fouling community, wet and dry mass measurements, including carbon and nitrogen contents. RESULTS AND DISCUSSION Artificial structures were located in the photit zone and the initial colonisation after a monthly immersion of BFs was dominated by autotrophs at both, fish cage and ' control site. The main taxa were algae (6 species of Chlorophyceae and Rhodophyceae) and diatoms, embedded in mucilage. Fouling fauna was represented by small bryozoan colonies (1 species], Hydroidea (3 species) and Bivalvia. On average, 30% (38.3±1.2) of BFs surface was covered by fouling organisms at fish form site compared to significantly higher coverage (73.3i7.25 on the control site. Algal fouling prevailed on fish farm site ;,,2.5±2.0% of total surface) compared to 3.3+3.1% ion the control site, where hydroids (49.2±3.1) and bryozoans 05.8+1.2%) dominated the early colonisation (Plate I: Figs 6a,. 6b). Algae covered, on average, 29.1+6.8 and 9.5+4.4% of BFs surface at fish farm and control locations, respectively, after three months of tine BFs immersion. BFs were nearly completely overgrown with fouling communities: 94.1 ±2.0% coverage was observed at fish farm and 95,0±1.8 on the control site. Fouling fauna was still dominated by hydroids and br yozoans, the latter covering 35.9±9.0 and 67.2+10,2% of BFs surface at fish farm and control locations, respectively. Algae coverage decreased to 13.4+4.2 and 1.2+1.5 % (fish farm and control site) after five months of immersion, while macrofauna, now consisting of 6 main sedentary groups (Hydroidea, Cirripedia, Ascidiacea, Bivalvia, Poiychaeta, Sryozoa) prevailed. However, only one bryozoan species Schizobrachiella sanguines covered over 80% of BFs surface at both localities. Nearly 2 years after the immersion of BFs, serpulid polychaetes, mostly Se.rpula vermicularis, dominated fouling communities at both localities. Vagife fauna, associated with BFs, was less important and included mainly Crustacea (Amphipoda, Gam-maridea, Decapoda, Anisopoda), motile Poiychaeta and opistobranch molluscs. A total of 38 sedentary taxa were identified over the experimental period (nearly 2 years) attached to BFs, of which 26 were common to both localities (Tab. 1). More taxa were registered at fish farm (36) than on control site (281 (Plate II: Figs 12, 13). Described pattern of colonisation of BFs generally conforms to the successions on artificial substrates observed in other studies in the northern Adriatic (Bressan, 2001) and elsewhere (Cook, 2001), The only exception was the low abundance of mussels and barnacles that seemed to be unsuccessful settlers on BFs. CONCLUSIONS The initial 5 months after BFs deployment were characterised by macro algae (Chlorophyceae, Rhodophyceae) settlement that covered comparatively larger surfaces on bio-filters deployed near the fish cage. Hy-drozoans and Bryozoa were also successful colonisers of BFs during this initial stage, particularly bryozoan Schizobrachiella sanguines outcompetecl other species for space. Serpulid polychaetes dominated the fouling community at both localities after over a year of immersion. Similar taxa developed at fish farm and control localities but number of taxa recorded on bio-filters deployed on fish farm site was higher, indicating that the enriched environment enhanced the settlement of various organisms. I ANNALES • Ser. hist. nal. • 13 • 2003 • 1 • Supplement Aids»-dr« fftUMCN rt ¿i: SUSPÍNWD BtOFII I ESS: SUCCESSION Qt FOULINC COMMUNITIES IMMEDIATELY AD|ACENT.10 A Rsiï CACE .;v.:2í-í4 ' Tab. 1: Taxoiwmic structure of flora & sedentary fauna Tab. 1: Taksonomska struktura flore i» sesi/ne favne v of bio-filter fouling communities at fish farm and at združbi obrasli na biofiltrih ob ribogojnici in na kon-control site between 2001 and 2003. trobi postaji v obdobju 2001-03. Taxa ] Fish farm Control site Algac Enteromorpha sp. + + Cladophora sp. + Antithamnion sp. + -f Polysiphonia sp. + + Ceramium sp. + + Champia sp. - + I FAUNA Spongiaria spp. | + - Hydroidea Obe lia gen/culata + + Campanopsis sp. T + Kirchenpaueria sp + + Eudendríum sp. + + Gonothyraea sp. + - Bivalvia Chiamys muSlistriata 4- + Ch/amys varías + + Hi a te Ha árctica + + Barbada barbat a + - Mytilus galbprovincialis + + Ostrea edulis H- + Anomia ephippium + + Pericardium sp. - Taxa Fish farm Control site Polychaeta Serpula vermicularís + ■+ Pomatoceros triquete, r + + ■ ■ Hydroides helmatus 4- - Mercierella enigmática + + Sptforbis pagenstecheri + + Salmacina incrustaos + - Polydora sp. + - Cirripedia Baíaous balanus + + Bryozoa Adeona haeckeli 4 - Buguls neritina + + : L ¡chenopora rad ¡ata + + Schizobrachiella + + ; sa nguinea i Tubu/ípora sp. + - : Ascidiacea Styela plicata + Polycarpa poma ría + + i Botryllus schlössen + + Microcosmos vulgaris + + Ascidie IIa aspersa + Phallusia sp. - SUKCESIJE ZDRUŽB OBRASTi NA LEBDEČIH BIOFILTRIH V NEPOSREDNI BLIŽINI RIBOGOJNICE IN NA KONTROLNI LOKACIJI Aleksandra FRUMENBorut Vrišer & Alenka MALE! Nacionalni inštitut za biologijo, Morska biološka postaja, SM>330 Piran, Fomače 'It E-mail: malej@mbss.0Fg POVZETEK V obdobju 2001 -2003 smo v Piranskem zalivu raziskovali sukcesije biološke obrasti na lebdečem umetnem substratu plastičnih mrež (biofiltrih) v neposredni bližini ribogojnice in na kontrolni lokaciji. Prvi naseljenci so bile bentoške alge (predvsem ob ribogojnici) in hidroidi (predvsem na kontrolni postaji). Poznejše sukcesije združb obrasti obeh lokacij je oblikovala zlasti suspenziofaga sedentarna favna Školjk„ polihetnih črvov, hidroidov, ma-hovnjakov in kozolnjakov. Po petih mesecih so prevladali mahovnjaki vrste Schizobrachiella sanguínea, po skoraj dveh lelihi pa polihetni črvi fSerpula vermicuiarisj. Ključne besede: obrast, sukcesije, ribogojnica, Jadransko morje 41 ANNALES ■ Ser. hist, nat. • 13 • 2003 1 • Supplement Áílfksílicíra FRl-MtN cl.ii: SIJSPF.NDFD BIÓFIÍTERS- SUCCESSION C' rOyÜÑC COMMUNITIES IMMLLMATOY ADIAOFNI TO AfiSHCAGl . .. ;!l-.!4 REFERENCES Angel, D. (2001): A review of biofiltration processes as used in waste management, in: A review of the environmental impacts of marine cage aquaculture, processes of biofiltration relevant to impact mitigation, the biological properties of marine invertebrates relevant to biofiltration and biofouling on artificial structures. BIOFAQs Ann. Rep,, Techn. Annex, p. 31-45. Black, K. D., M. D. J. Saycr, E. Cook, 13. Angel, E. Spanier, 1. Karakasis, A. Malej, K. Collins, H. Pickcring, S. Whitmarsh & S. Lojen (2001); BIOFAQs - Biofiltration and Aquaculture: an evaluation of substrate deployment performance with mariculfure developments. Cahier Options Mediterranneennes, 55, 205-207. Bressan, G. (2001). 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