Urnatella gracilis leidy (kamptozoa) in heated effluents from the "Dolna Odra" power station

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Urnatella gracilis Leidy (Kamptozoa) in heated effluents from the “Dolna Odra” power station

Urnatella gracilis Leidy

M. Wolska

Kamptozoa (or Entoprocta) are small, mainly marine, sedentary animals (Barnes 1969). Only two freshwater species have been reported to date: originally North American Urnatella gracilis Leidy (Weise 1961, Barnes 1969) and Loxosomatoides sirindhornae (Wood 2005) recently discovered in the rivers in central Thailand. Of those two species, U. gracilis is significantly better known and widespread. Apart from North America, the species has been reported from, inter alia, South America, Africa, southern India and Japan (Wood 2005). In Europe, this entoproct was detected, inter alia, in Belgium, France, Hungary and in the whole drainage basin of the Black Sea (Lukacsovics and Pйcsi 1967; Protasov 1997; D'Hondt et al. 2002; Paavola et al. 2005; Wood 2005). The first occurrence of U.

Urnatella gracilis Leidy… M. Wolska gracilis in Poland was reported from the Konin lakes system (Protasov 1997). The system consists of several flow-through lakes that receive heated effluents from a nearby power station. According to many authors, U. gracilis is a thermophilic and rheophilic species (Wiese 1961, Emschermann 1987). Therefore, we assumed that it could likely occur also in other heated waters in Poland. Previous, unpublished reports indicated occurrence of U. gracilis in a canal receiving discharges of heated effluents from the “Dolna Odra” power station, situated south of Szczecin (D№bkowski 1996). The aim of this study was to verify these reports and to investigate taxonomic composition of periphytic communities in this watercourse.

Study area and experimental methods

The canal receiving discharges of heated effluents from the “Dolna Odra” power station is on average 40 m wide, some 5 m deep and 2.5 km long. Water flow in the canal is varied and depends on the power station's operation, which results in fluctuations of water level and water flow rate (D№bkowski, 1996). The canal is also used for commercial cage culture of warm-water fish.

Table 1. Physicochemical properties of water in the warm channel of Dolna Odra power station from May to October 2002.

Rectangles of plastic film (7 cm Ч 14 cm) were used as substrata. They were tied to a nylon rope weighted down with a stone and then attached to a pier, in a 10-m distance from the shore. The plastic film rectangles were totally submerged and exposed to water current. The substrata were placed in the discharge canal in April 2002. Three subsamples were collected on each subsequent month until October 2002. In the laboratory, periphyton was scraped off the plastic film, sieved through a 50-µm mesh and next placed in containers to which water and formalin were added. Macro organisms were counted and taxa were determined. The quantity of periphytic macro organisms was expressed as the number of individuals per m-2 (ind. m_2). In case of colonial organisms, single individuals (e.g., Cordylophora caspia) or single polypides (Plumatella repens) were counted.

Results

The examination of the collected periphytic communities revealed large quantity and taxonomical diversity of organisms. Urnatella gracilis occurred in all samples, except those collected in May. Apart from this species, 24 other taxa of macro organisms were found. Among them, both sedentary and mobile forms were observed. The most numerous were: Oligochaeta (mostly Chaetogaster sp.), Plumatella repens (Bryozoa) and Cordylophora caspia (Hydroidea). Occasionally found were: Hydra sp., Insecta (Simmulidae, Empididae), Molusca (Sphaerium sp.), Gastropoda (Lymnaea sp., Physella sp.) and Tardigrada.

Table 2. Number [ind.·m-2] of peryphytone organisms on anthropogenic substrate in warm channel of Dolna Odra power station, in 2002.

Samples collected in May, after just 30 days of staying in water, were the less numerous and taxonomically the poorest. A total of 5 taxa were found, with the overall quantity of organisms averaging 15504 ind. m-2. The most numerous taxon was a representative of Oligochaeta: Stylaria lacustris (4564.5 ind·m-2), while Urnatella gracilis was not found in these samples.

In June, we observed a threefold increase in the biodiversity (16 taxa) and a tenfold increase in the density of organisms, which reached its maximum value - 151445.0 ind. m-2. For the first time Urnatella gracilis was detected, and right away it turned out to be a dominant species occurring in a number of 40953 ind. m-2. Two other sedentary species: Cordylophora caspia (20298.0 ind.·m-2) and Plumatella repens (9843.5 ind.·m-2) were much less abundant.

In July, a decrease in the biodiversity (12 taxa) and density of organisms (82288.5 ind. m-2) was observed. Urnatella gracilis was still the dominant species (26698.5 ind·m-2). Less abundant, but equally significant for periphyton, was a representative of Oligochaeta: Chaetogaster sp. (18742.5 ind.·m-2), as well as Cordylophora caspia (13591.5 ind.·m-2) and Plumatella repens (10761 ind. ·m_2).

In September, 13 taxa were recorded, but the density of organisms further decreased to 56610.0 ind.·m-2. This time the dominant species was Plumatella repens (41539.5 ind.·m-2), while the density of Urnatella gracilis population decreased significantly to 535 ind. m-2. Cordylophora caspia was still relatively abundant - 7267.5 ind·m-2. periphyton substrate anthropogenic camptozoa

In October, the biodiversity increased to 18 taxa, but the overall density decreased by half, to 26851.5 ind. m-2. Plumatella repens (10225.5 ind. m-2) and Chaetogaster sp. (5023.5 ind. m-2) dominated. The participation of U. gracilis decreased to 408.0 ind. m-2.

Discussion

D№bkowski (1996), in his hydrobiological study of the discharge canal of the “Dolna Odra” power station, did not record the presence of Urnatella gracilis. However, there were some reports from non-systematized qualitative samples, that this species occurred in the watercourse, but no such information has ever been published. Our study has confirmed occurrence of this kamptozoan in the canal. Moreover, during two months (June and July), the species turned out to be a dominant component of the periphytic community in the canal. We assume that water temperature might have been one of the factors that enabled abundant occurrence of U. gracilis in those months, as temperature influences vegetative growth of these animals (Emschermann 1987), although water temperature in the canal was not as high as 30 єC or more reported for Konin lakes (Protasov 1997). Dissolved oxygen content might have been another factor that facilitated growth of U. gracilis. Worth noticing is that the population of Urnatella started to decrease in September, when water temperature was still high, but oxygen content decreased comparing to previous months (Table 1).

This study focused also on organisms living in association with Urnatella gracilis. The community was similar to the one observed previously by D№bkowski (1996). According to Protasov (1997), Urnatella gracilis lived together with Plumatella emarginata. Also other organisms were reported to live in association with Urnatella gracilis, inter alia, Hydra americana, Cordylophora lacustris and some bivalves, including Dreissena polymorpha (Weise 1961, Wood 2005). Although in this study we found similar community, some differences were observed. In the periphytic community of the discharge canal, we found different representative of Bryozoa - Plumatella repens, and numerous individuals of Corylophora caspia. This might have resulted from similar environmental preferences of those species. Similarly as Plumatella repens and Cordylophora caspia, Urnatella gracilis can tolerate slight water pollution, but has never been reported in seriously polluted waters (McCullough and Smith 1975). It is hard to estimate the effects of this freshwater entoproct spreading in Polish waters. There are no reports on its adverse influence on other organisms, even though it often occurs in a large number (King et al. 1988), and sometimes even lives as a commensal on insect larvae (Tracy and Hazelwood 1983). As a suspension feeder, it may positively participate in removing the tiniest suspended particles. To confirm this assumption, further studies should be undertaken on the species' ecology in Polish waters and its distribution in other parts of the Oder river estuary.

Major statements and conclusions

1. In the discharge canal, a total of 25 taxa of periphytic macro organisms were found on all submerged substrata. The main representatives of groups inhabiting the examined substrata were: Oligochaeta, Plumatella repens and Cordylophora caspia.

2. Occurrence of Urnatella gracilis Leidy, a representative of Entoprocta not recorded before in this region, has been confirmed. The species was present in all the samples, except those collected in May.

3. The highest quantity of periphytic organisms was found in June (151445 ind. m-2), and the dominant taxa at that time were Urnatella gracilis (40953 ind. m-2), Chaetogaster sp. (29605.5 ind. m-2) and larvae of Chironomidae (28738.5 ind. m-2).

References

1. Barnes R.D., 1969. Invertebrate zoology. W.B. Saunders Co., Philadelphia.

2. D№bkowski P., 1996. Wpіyw wуd podgrzanych na populacjк Plumatella repens L. (Bryozoa) wystкpuj№c№ w kanale ciepіym Elektrowni „Dolna Odra”. [The effect of heated effluents on the population of Plumatella repens L. (Bryozoa) in the warm canal of the “Dolna Odra” power station]. In: Przyrodnicze aspekty badania wуd estuarium Odry i wуd jeziornych wojewуdztwa szczeciсskiego. Proceedings No. 19, Uniwersytet Szczeciсski. (in Polish)

3. D'Hondt J.-L., Morgillo A., Gontier B., 2002. Urnatella gracilis Leidy, 1851, un Entoprocte d'eau douce nouveau pour la faune franзaise. Bulletin mensuel de la Sociйtй linnйenne de Lyon, vol. 71, No7, pp. 269-274

4. Emschermann P., 1987. Creeping propagation stolons - an effective propagation system of the freshwater entoproct Urnatella gracilis Leidy (Barentsiidae). Arch. Hydrobiologie, Vol. 108, no. 3, pp. 439-448.

5. King D.K., King R.H., Miller A.C., 1988. Morphology and Ecology of Urnatella gracills Leidy, (Entoprocta) , a Freshwater Macroinvertebrate from Artificial Riffles of the Tombigbee River, Mississippi. Journal of Freshwater Ecology Vol. 4, No. 3, pp. 351-360.

6. McCullough J.D., Smith B., 1975. Some ecological observations on Urnatella gracilis Leidy. Southwest. Nat., Vol. 20, no. 2, pp. 171-176.

7. Paavola M., Olenin S., Leppдkoski E., 2005. Are invasive species most successful in habitats of low native species richness across European brackish water seas? Estuarine, Coastal and Shelf Science, 64 (2005) pp. 738-750

8. Protasov A.A., 1997. The spreading and abundance of Bryozoans and Kamptozoa in Konin Lakes system (Poland). All - Russian and International Conference on Bryozoa. Institute of Hydrobiology, Kiev, Ukraine.

9. Szlauer B., Szlauer L., 1998. Organisms colonising polyethylene sheets deployed in river Odra mouth. Abbrev.: Fol. Univ. Agric. Stetin. 184 Piscaria (24): 79 - 90.

10. Tracy B.H., Hazelwood D.H., 1983. The Phoretic Association of Urnatella gracilis (Entoprocta:Urnatellidae) and Nanocladius downesi (Diptera:Chironomidae) on Corydalus cornutus (Megaloptera:Corydalidae). Freshwater Invertebrate Biology, Vol. 2, No. 4, pp. 186-191

11. Wiese J.G., 1961. The ecology of Urnatella gracilis Leidy: Phylum Endoprocta. Limnol. Oceanogr. 6(2), 228-230.

12. Wood T.S., 2005. Loxosomatoides sirindhornae, new species, a freshwater kamptozoan from Thailand (Entoprocta). Hydrobiologia, 544:27-31.

Abstract

This study examined periphyton that formed on anthropogenic substrata placed in a canal receiving discharges of heated effluents from the “Dolna Odra” power station. Apart from species typical for these waters, we recorded occurrence of Urnatella gracilis, a kemptozoan found in this area for the first time. Colonies of U. gracilis occurred in high density, especially in June and July, in association with Plumatella fungosa and Cordylophora caspia.

It is investigated periphyton plants on antropogenic substratum placed in the warm channel of power station DOLNA Odra. Except the kinds typical for these waters, the first time it is found representative Kamptozoa - Urnatella грацилис. U.Gratsilis's quantity was big, especially in June and July.

Keywords: Kamptozoa, Entoprocta, periphyton.

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