Studi Trent. Sci. Nat., 86 (2009): 119-126 ISSN 2035-7699119 © Museo Tridentino di Scienze Naturali, Trento 2009 Atti XVIII Convegno Gadio 2008: Un mondo che cambia: successioni ecologiche, invasioni biologiche ed alterazioni antropiche Sessione 7 - Comunicazione orale: Trasformazioni, impatti e strumenti di gestione in ambienti acquatici 2 Diatoms in the SW Piedmont (N-Italy) biological river monitoring network, with particular attention to the possible expansion of distribution of the “invasive” spe- cies Didymosphenia geminata (Lyngbye) Schmidt in Italy Maurizio BATTEGAZZORE1*, Lucio LUCADAMO2 & Luana GALLO2 1 ARPA - Agenzia Regionale per la Protezione Ambientale del Piemonte, Via Vecchia di B.S. Dalmazzo 11, 12100 Cuneo, Italy 2 University of Calabria, Department of Ecology, Via Ponte Pietro Bucci, 87036 Arcavacata di Rende (CS), Italy * Corresponding author e-mail: [email protected] SUMMARY - Diatoms in the SW Piedmont (N-Italy) biologcal river monitoring network, with particular attention to the “invasive” spe- cies Didymosphenia geminata (Lyngbye) Schmidt - Diatoms were sampled in March 2007 in 39 stations of the SW sector of the Piedmont macroinvertebrate-based biological quality monitoring network situated along 14 watercourses, among which are important rivers such as the R.Po and the R.Tanaro. D. geminata – considered to be invasive in various parts of the world - was found in 13 watercourses and in 25 stations (93% and 64% of the total, respectively). Abundances of D. geminata were generally quite low, but in 6 stations reached 3% of the individuals of the community and a peak of 12% in one station. D. geminata abundance was not significantly correlated with altitude or with European diatom indices of water quality (EPI-D, IBD and TDI). Some degree of correlation was observed between the macroinvertebrate– based IBE index and the EPI-D index (r= 0.67) and between the same IBE index and D. geminata abundance (r= 0.41). This species results to be more widespread than expected and the hypothesis of an expansion of its distribution area in Italy is plausible, but its past presence in many of these watercourses cannot be excluded. The past data, in fact, are not sufficient to reach precise conclusions regarding present trends of geographical distribution and population densities in the studied area. However, the situation deserves to be monitored. RIASSUNTO - Le diatomee nei punti della rete di monitoraggio biologica dei fiumi del Piemonte Sud-Occidentale, con particolare atten- zione alla specie “invasiva” Didymosphenia geminata (Lyngbye) Schmidt in Italia - Nel Marzo 2007 sono state campionate le comunità diatomiche in 39 stazioni del settore Sud-Occidentale della rete di monitoraggio basata sui macroinvertebrati bentonici, ubicate in 14 corsi d’acqua fra i quali i fiumi Po e Tanaro.D. geminata – specie considerata invasiva in diverse parti del mondo – è stata osservata in 13 corsi d’acqua e 25 stazioni (93% e 64% del totale, rispettivamente). Le abbondanze di D. geminata erano generalmente basse, tranne in 6 stazioni con oltre il 3% della comunità e un picco del 12% in una stazione. L’abbondanza di D. geminata non è risultata significativamente correlata con l’altitudine o con alcuni indici diatomici europei di qualità dell’acqua (EPI-D, IBD e TDI). Un certo grado di correlazione è stato osservato fra l’indice IBE basato sui macroinvertebrati bentonici e l’indice EPI-D (r= 0,67) e fra lo stesso IBE e l’abbondanza di D. geminata (r= 0,41). Questa specie è risultata più diffusa di quanto immaginato ed è plausibile ipotizzare che il suo areale in Italia sia in espansione, ma la sua presenza passata almeno in parte dei corsi d’acqua studiati non può essere esclusa. Al momento non è quindi possi- bile raggiungere conclusioni sulle attuali tendenze nella distribuzione geografica e nella densità di popolazione della specie; pare tuttavia opportuno monitorare l’evolversi della situazione. Key words: river diatom communities, Didymosphenia geminata, invasive species Piedmont (Italy) Parole chiave: comunità diatomee, Didymosphenia geminata, specie invasive, Piemonte (Italia) 1. INTRODUCTION of water quality with other monitoring methods. D. geminata (Fig. 1) has the capacity to form persist- Work on diatoms has a tradition in Italy starting ant mats of organic material (thanks to the massive develop- from the XIX century (Meneghini 1846). In SW Piedmont, ment of extracellurar, polysaccharidic stalks) covering river the first known study of diatoms was by Castracane degli bottoms. In recent years, massive nuisance blooms and ex- Antelminelli (1888) who studied the diatoms of the sedi- pansion outside its known geographical range on the part of ments in the hot spring waters of Valdieri. D. geminata were reported in several countries around the Only very recently, other studies were undertaken world (Kilroy 2004; Spaulding & Elwell 2007). Battegaz- in limited portions of the Province of Cuneo (Battegazzore zore et al. (2007b) referred the occurrence of the species in et al. 2004; Battegazzore et al. 2007a). One of the aims of 2006 in the Province of Cuneo, in the Po and Varaita rivers. this study was to give a picture of the diatom communities, Therefore, in this study it was decided to extend the search never systematically studied before in all the main water- of this potentially invasive species, already found in 2 riv- courses of the Province, and to compare the results in terms ers, to all of the 14 main watercourses of the Province. 120 Battegazzore et al. Diatoms and Didymosphenia geminata in SW Piedmont 2. METHODS AND STUDY AREA In Italy, large-scale monitoring of Diatoms for river quality evaluation has not been implemented yet. Therefore, it was decided to adopt the sampling locations used in the current macroinvertebrate monitoring network, including 39 stations situated between 150 e 1380 m a.s.l. along the 14 principal watercourses of the Province of Cuneo (see Fig. 2 and Tab. 1). Sampling was undertaken in the spring of 2007 according to the procedure described by Kelly et al. (1998). Samples were cleaned using 30% hydrogen peroxide and slides were mounted using Naphrax medium. Microscopic examination of about 400 diatom frustules for each sample, in LM at 1000 X, allowed taxonomic identification accord- ing to Krammer & Lange-Bertalot (1991-1997). On all diatom taxonomic lists, the indices TDI (Kelly & Whitton 1995), IBD (Prygiel & Coste 2000) and EPI-D (Dell’Uomo 2004) were calculated. On water samples taken in the same locations and period of time, analyses of the 12 variables: dis- solved oxygen % saturation, nitrites, total nitrogen, solu- ble phosphates, sulphates, chloride, conductivity, total hardness, suspended solids, chemical oxygen demand, trivalent chromium and dissolved iron were undertaken according to the APAT (2003) methods. Moreover, in the same reaches of the watercourses the macroinverte- brate communities were sampled and the Indice Biotico Esteso (IBE) index was calculated, following the APAT (2003) procedure. Data were elaborated using PC-ORD software (McCune & Mefford 1999). Pearson’s correla- tion coefficient was calculated among all variables: the chemical variables listed previously, the TDI index, al- titude and distance from source. On all data, verifica- Fig. 1 - Didymosphenia geminata observed under LM at 1000x. tion of normal distribution and a Monte Carlo test were The characteristic outline and large size make it very difficult to carried out. CCA (Canonical Correspondence Analysis) confound this species with other diatom taxa. Fig. 1 - Didymosphenia geminata osservata in microscopia ottica was adopted in order to link the taxonomical data to the a 1000x. La caratteristica forma e le grandi dimensioni la rendo- environmental variables. no difficilmente confondibile con altri taxa di diatomee. Fig. 2 - Study area with water- courses and sampling stations represented by red dots (where D. geminata was sampled) and green dots (where D. geminata was not found). Fig. 2 - Area di studio con corsi d’acqua e stazioni di campiona- mento rappresentati con pallini rossi (località dove D. geminata era presente) e con pallini verdi (dove non è stata campionata). Studi Trent. Sci. Nat., 86 (2009): 119-126 121 1 P-PO4 El T3 DO G2 TDI T4 M1 T6 C2 Bo2 Bo3 G1 S5 Bo4Bo5 T2 S4 P2 N-NO 2 0 T1 M2 S6 -1,5 C1 S2 P1 1,5 P5 Be2 Pe Va1 1 Bo1 Be3 G Ve Cl Cond Va2 Be N tot. Cr S1 SO4 P4 Altit P3 sse 2 Axis 2 A Fe Fig. 3 - Biplot of the samples and environmental factors for the first two axes of the CCA. For symbol meanings see tables 1 and 2. Fig. 3 - Diagramma di ordinamen- Ti to dei campioni e dei fattori am- bientali per i primi due assi della CCA. Per i significati dei simboli -2,5 si vedano le tabelle 1 e 2. Asse 1 Axis 1 3. RESULTS CCA performed on the 13 environmental factors (DO, N- NO2, Ntot., P-PO4, SO4, Cl, Cond., S.Sol., COD, Cr, Fe, A total of 190 diatom taxa were identified in the Altit. and TDI) and 39 samples is shown in Fig. 3. The present study. The most abundant taxa in the entire study variables COD and Suspended solids and also stations M3 were Achnanthidium minutissimum (Kutzing) Czarnecki, and T5 are not shown on the biplot because they are very Achnanthidium pyrenaicum (Hustedt) Kobayasi and Coc- close to the origin of the axes. The CCA accounted for coneis pediculus Ehrenberg. The most frequent ones about 20 % of total variability in tha taxonomic data, most (i.e. those present in the highest number of stations) were of which was asociated with the first axis. The variables A.minutissimum, Navicula tripunctata (O.F. Muller) Bory altitude, Chloride and the trophic index TDI were those and Diatoma vulgaris Bory. D. geminata was present in 13 best correlated with axis 1, while soluble phosphates and watercourses out of 14 (93%), in 25 points out of 39 (64%), iron were the factors best correlated with axis 2.