Abundance and distribution of freshwater sponges (Spongillidae)in Danube floodplain waters near Vienna, Austria

Transcription

1 Abudace ad dstrbuto of freshwater spoges (Spoglldae) Daube floodpla waters ear Vea, Austra Irs Dröscher 1, Joha Warger 1 Keywords: Spoglldae, Dauba floodpla waters, Vea Itroducto Although the phylum Porfera comprses more tha 6 speces, less tha 3 are kow from freshwaters (Frost, 1991) wth 6 speces beg recorded Cetral Europe (Ardt, 1926; Prozato & Maco, 1987): Spoglla lacustrs, Euapus fragls, Ephydata fluvatls, E. müller, Trochospoglla horrda ad Heteromeyea stepaow. A further speces (Euapus carter), well kow from tropcal ad subtropcal Afrca ad Asa ad from Lake Balato Hugary has bee reported from coolg water outlets of a uclear power plat Germay (Gugel, 1995). Ufortuately, there s a paucty of data o ecologcal parameters fluecg dstrbuto patters of freshwater spoges. The purpose of the preset study was, therefore, to obta quattatve formato o abudace ad habtat requremets of spoge speces typcal Dauba floodpla waters. Methods Freshwater spoges were collected durg a summer (28 Jue 14 July, 24) ad autum cesus (19 September 1 October, 24) at 32 samplg stes located at floodpla waters wth the cofes of the Natoal Park Doau-Aue east of Vea, Austra. At each ste, each substrate type (macrophytes, dead wood, meral substrate cludg rprap) was thoroughly checked for spoges ether from the shore or by boat throughout a 3 mute perod (CPUE; catch per ut effort). The coloy sze was measured usg a trasparet grd, spoges released from the substrate usg a kfe ad preserved 75% ethaol. I the lab, slceous spcules of spoges ad gemmulae were solated usg 1% Sodum Dchloro- Isocyaurate (Hooper, 2), trasferred to sldes, embedded ad vestgated uder a mcroscope. Speces were detfed usg the keys by Bartsch (1957) ad Streble & Krauter (22). Spcules were measured usg a ocular mcrometer ad checked for aomales; up to 3 spcules were vestgated per specme. For SEM vestgatos (JOEL JSM 35CF scag mcroscope), spcules were trasferred to 65% HNO 3 for 6 (spoges) or 24 hours (gemmulae), washed water ad 1% ethaol ad sputtered wth gold (AGAR B734). For checkg the fluece of abotc parameters, frequecy devatos were calculated (Øklad & Øklad, 1996) whch are gve by the followg formula: N F N = 1 where F = frequecy devatos for terval, = umber of samplg stes terval, = total umber of stes, N = umber of stes where the speces was preset terval ad N = total umber of stes where the speces was preset. Devatos were checked by Ch-square tests. Staststcal aalyses were performed usg the package SPSS. For caocal correspodece aalyss (CCA), evrometal data were (log+1) trasformed, rare speces 1 Departmet of Freshwater Ecology, Vea Uversty, Althastraße 14, 19 Vea, Austra 236

2 dowwehgted ad Mote Carlo urestrcted permutato tests (= 499) were performed; for these calculatos the package CANOCO was used. Results ad dscusso I the Natoal Park Doauaue fve of the sx Austra speces of freshwater spoges were recorded (Table 1). Raked from abudat to rare, these speces comprsed Ephydata fluvatls (Lé 1758), Spoglla lacustrs (Lé 1758), Ephydata müller (Leberküh 1855), Euapus (=Spoglla) fragls (Ledy 1851) ad Trochospoglla horrda (Welter 1893). Heteromeyea stepaow, already reported from Cartha, was lackg the samples. Trochospoglla horrda seems to be recorded for the frst tme Austra. The hgh colosato ablty of Ephydata fluvatls s reflected by the fact that t was preset at early each samplg ste. Ephydata müller, Euapus fragls ad Spoglla lacustrs were frequetly assocated the water bodes of the Daube flood pla. For most spoges hard substratum was essetal for growth. Suspeded tmber use the surroudgs of the water bodes ad dead trees drftg the water seems to postvely fluece the abudace of freshwater spoges. Euapus fragls, Ephydata fluvatls ad Ephydata müller sgfcatly prefer wood over stoe substrate, whereas Spoglla lacustrs deftely preferred the latter (Fg. 1). Ephydata fluvatls sgfcatly favoured water bodes wth summer temperatures above 21 C, whereas Ephydata müller sgfcatly avoded water bodes wth temperatures below 17.5 C. I addto Ephydata müller ad Trochospoglla horrda preferred backwaters wth hgher hydrologcal coectvty wth the Daube, whlst Spoglla lacustrs Table 1. Ivetory of freshwater spoge speces collected at 32 floodpla water bodes wth the area of the Natoal Park Doau-Aue ear Vea, Austra; showg the area colozed by each speces (cm² wth percetages) at the summer (Jue / July) ad the autum (September / October) cesus. Speces Area colozed (cm²; %) Ephydata fluvatls (Lé 1758) Ephydata müller (Leberküh 1855) Spoglla lacustrs (Lé 1758) Euaps fragls (Ledy 1851) Trochospoglla horrda (Welter 1893) Jue / July September / October Total 155 (68.) 114 (55.7) 2195 (61.) 144 (9.3) 42 (19.6) 546 (15.2) 189 (12.2) 443 (21.6) 632 (17.6) 137 (8.8) 19 (.9) 156 (4.3) 26 (1.7) 43 (2.1) 69 (1.9) 237

3 1% Area colozed (cm²) 8% 6% 4% 2% % Ephydata fluvatls Ephydata müller Spoglla lacustrs Spoglla fragls Trochospoglla horrda Fg. 1. Substrate prefereces (gve as percetages) of the fve spoge speces. Lght grey: wood, medum grey: stoes, dark grey: macrophytes ( = P<.5, = P <.1, = P<.1). ad Ephydata fluvatls were favoured by lower coectvty (Fg. 2). Stes 29 to 32, where spoges were completely lackg, are located the backwater system of Regelsbru, whose flow ad coectvty wth the Daube has bee creased wth the last years. The abudaces of Ephydata müller ad Trochospoglla horrda were sgfcatly (P<.5) ad postvely flueced by creased slca cotet, whereas Ephydata fluvatls preferred habtats wth low slca cotet (Fg. 3). Wth respect to aberrat macroscleres, Ephydata fluvatls followed by Ephydata müller ad Euapus fragls were the most ecosestve speces, whereas aberrat macroscleres were oly seldom recorded Trochospoglla horrda ad Spoglla lacustrs. Aomalous hooks occurred most ofte, whereas cetrotylots were scarcest. 238

4 Frequecy devato Frequecy devato Abwechug der Häufgket stagat medum flow lotc Curret weak medum strog Caopy Slca Fg. 2. Curret velocty, caopy shadg ad slca cocetrato prefereces of Ephydata fluvatls, the most commo spoge speces of the study area, based o frequecy devatos ( = P<.5; hatched colums: Ch-square test ot possble). 1 SO 2 T. horrda Coectvty Koektvtät Durchströmug E. fluvatls E. müller E. fragls S. lacustrs

5 Fg. 3. Caocal correspodece aalyss of hydrologcal coectvty ad slca cocetrato versus area colozed by the fve spoge speces at 32 samplg stes. Refereces ARNDT, W. (1926): De Spoglldefaua Europas. Arch. Hydrobol. 17: BARTSCH, A. (1957): Das Bestmme ehemsche Süßwasserschwamme. - Mkrokosmos 47: FROST, T. M. (1991): Porfera. I: THORP, J.H. & COVICH, A.P. (eds): Ecology ad Classfcato of North Amerca Freshwater Ivertebrates: Academc Press, Sa Dego, Calfora. GUGEL, J. (1995): Erstachwes vo Euapus carter (Bowerbak 1863) (Porfera, Spoglldae) für Mtteleuropa.- Lauterbora 2: HOOPER, J.N.A. (2): Spogude. Gude to spoge collecto ad detfcato. ( ).: Queeslad Museum, Australa. ØKLAND, K.A. & ØKLAND, J. (1996): Freshwater spoges (Porfera: Spoglldae) of Norway: Dstrbuto ad ecology. - Hydrobologa 33: 1-3. PRONZATO, R. & MANCONI, R. (1987): Chave dcotomca per l rcooscmeto delle spuge d aqua dolce Italae. - Boll. Mus. Ist. Bol. Geova 53: STREBLE, H. & KRAUTER, D. (22): Das Lebe m Wassertropfe: Kosmos, Stuttgart. 24