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Zoobenthic assemblages of ponds supplied with biologically treated sewage
DOI: 10.2478/v10104-010-0014-z Vol. 9 No 2-4, 313-318 2009
Zoobenthic assemblages of ponds supplied with biologically treated sewage
Jacek Koszałka1, Stefan Tucholski2 1
Department of Applied Ecology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 5, 10-957 Olsztyn, Poland [email protected] 2 Department of Land Reclamation and Management, University of Warmia and Mazury in Olsztyn, Plac Łódzki 2, 10-719 Olsztyn, Poland
Abstract The composition of benthic macroinvertebrate communities were studied in three interconnected earth fish ponds in the sewage treatment plant in Olsztynek. These ponds were fed with biologically treated wastewater and stocked with the common carp (Cyprinus carpio L.), tench (Tinca tinca L.), European pike-perch (Sander lucioperca (L.)) and roach (Rutilus rutilus L.). Zoobenthos was sampled monthly between April and October 2007. The dominant taxa were Chironomidae and Oligochaeta. Ceratopogonidae and Ephemeroptera were scarce. Taxon richness was low. The total densities of bottom fauna of ponds varied from 3060 ind. m-2 to 9928 ind. m-2 in pond 1 and 2, respectively. Abundance of the total zoobenthos of three ponds showed similar temporal patterns with a peak in mid summer and a minimum in early spring and fall. The fauna of ponds were partially similar and indicated high trophy and impact of fish. The presence of underground springs at the bottom of ponds no. 2 and 3 probably affected the composition of aquatic macroinvertebrate communities. Key words: pond, zoobenthos, wastewater supply.
1. Introduction Wastewater is characterized by high nutrients content, and introduction of such fertilizers into aquatic ecosystem brings considerable effects on the life of organisms. Therefore, trophic potential of sewage is exploited in rearing zooplankton for fish feeding (Guerrin 1988; Dave 1989; Pelczarski 2004) or for supplying nutrients to ponds where rearing of whitefish were conducted (Tucholski 1994). In fish culture the
direct enrichment of the pond with organic allochtonic substances, as a pig manure (Dhawan, Kaur 2002) or animal wastes (Wohlfarth, Schroeder 1979) is used for fertilization in order to enhance plankton production. Benthic organisms are recognized as an important part of the foodcycle in fish ponds and the indirect influence of the fish on zoobenthos through their control of filter-feeding zooplankton is very strong (Lellák 1978). Therefore fertilization may have a distinct positive effect to increase both benthic and fish
J. Koszałka, S. Tucholski
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Table I. Main physico-chemical characteristics of the 3 ponds during the period of study (based on unpublished data of second author). Variable Temperature (0C) Dissolved oxygen (mg dm-3) pH Temperature (0C) Dissolved oxygen (mg dm-3) pH Temperature (0C) Dissolved oxygen (mg dm-3) pH
Date 2.04.07 7.05.07 4.06.07 2.07.07 1.08.07 3.07.07 2.10.07 Pond 1 12.2 15.6 19.6 19.6 17.9 15.9 14.4 16.0 12.9 4.0 4.6 5.6 9.0 10.1 8.7 8.8 7.8 8.5 7.8 8.5 8.7 Pond 2 9.5 15.7 18.0 17.3 16.7 14.9 13.7 19.0 12.6 4.5 3.8 7.5 14.6 7.7 8.8 8.5 7.5 8.1 7.9 8.7 8.2 Pond 3 9.8 15.5 17.9 19.1 17.3 15.0 13.6 13.4 18.3 6.0 8.7 6.1 5.8 10.5 8.2 9.1 7.6 8.4 7.6 8.0 8.4
production in ponds (Hall et al. 1970; Wasilewska 1978). Chironomus larvae, the predominant form in many shallow lentic habitats including ponds (Broza et al. 2000). Their large size and high biomass make these organisms a potentially important food resource for fish (Jonasson 1972). The mass emergence of adult insects in wastewater ponds where no presure of fish and macroinvertebrate predators occurres may cause nuisance or medical problems (Broza et al. lc.). Emergence of adult insect is also an important path of organic matter and nutrients loss form the aquatic ecosystem (Lellák 1981). Benthic invertebrate species are funcional component of fish pond ecosystem, not only as prey items consumed by fish, but they also can play a role as parasite-transmitting vectors (Brinkhurst 1997) or bioaccumulators of heavy metals and chemicals (Hare et al. 1994). The aim of this study was to analyze the qualitative and quantitative composition of benthic communities and the patterns of their seasonal changes in three ponds fed with a similar amount of biologically treated wastewater and stocked with the same species of benthivorous fish.
it was periodically fed into the ponds, in comparable quantities. The surface area of the experimental ponds was as follows: pond no. 1 – 1.04 ha, pond no. 2 – 0.94 ha, pond no. 3 – 1.00 ha. The maximum depth in summer was 1.5 m in each of the ponds. The studied reservoirs were filled with water from underground springs at the bottom of ponds no. 2 and 3. The ponds were characterized by similar physicochemical parameters of water (Table I). The periodic introduction of treated wastewater to the ponds did not cause oxygen deficits. The ponds were stocked with the common carp (Cyprinus carpio L.), tench (Tinca tinca L.), European pike-perch (Sander lucioperca (L.)) and roach (Rutilus rutilus L.) (Table II). The tench and roach were stoked into the ponds in the middle of November 2006, and the European pike-perch and carp (0+) were stocked in the middle of June 2007. The average weight of individual carps aged 1+ ranged from 365.0 g fish-1 in pond no. 2 to 559.1 g fish-1 in pond no. 3, and the weight of carp aged 0+ was 1.6 fish-1 in all experimental ponds. The average weight of tench spawners reached from 342.8 g fish-1 in pond no. 3 to 944.4 fish-1 in pond no. 1. Tench aged 1+ weighed 18.3 g fish-1 in pond no. 1 and 18.2 g fish-1 in pond no. 3, while tench
2. Materials and methods A field experiment investigating fish stocking material was carried out in the production season from April to October 2007 in three interconnected earth fish ponds on the premises of a wastewater treatment plant in Olsztynek (NE Poland). Raw wastewater fed to the treatment plant comprised household sewage as well as wastewater from a fruit and vegetable processing plant. Following preliminary treatment and the removal of screenings and sand, wastewater was treated in sequencing batch reactors (SBR), and
Table II. The species and the age structure of fish used for pond stocking. Modified from Goździejewska, Tucholski (2010, in press). The species and the age structure Cyprinus carpio L. (1+) C. carpio (0+) Tinca tinca L. spawners T. tinca (1+) T. tinca (0+) Sander lucioperca (L.) (0+) Rutilus rutilus L. (0+)
1 + + + + + +
Pond 2 + + + + +
3 + + + + + -
Zoobenthos of ponds supplied with biologically treated sewage
in the 0+ age category – 1.0 g fish-1 in ponds no. 1 and 3. The average individual weight of roach hatchlings and European pike perch hatchlings was 2.5 g fish-1 and 0.15 g fish-1, respectively. The presence of tench fry aged 0+ was noted during fish harvest in ponds no. 1 and 3 in the autumn of 2007. The hatchlings were the offspring from natural spawning of tench in those ponds (Goździewska, Tucholski 2010 in press). At each pond three samples were collected using a Kajak sampler (collecting area: 25.5 cm2) at the center and at the halfway point between the center and edge of the pond. Samples were washed through a 0.5 mm mesh size sieve . The material was sorted under a stereoscopic microscope, fixed and preserved in 4% formalin. Animals were identified to the lowest taxonomic unit possible. Bray Curtis distance matrix was applied to determine similarity and Mann-Whitney’s non parametric U-test was used to test differences in community abundances between the three ponds.
315
Described above analyses were performed using MVSP (Bray-Curtis) (Kovach 2006) and Statistica 6.0 (Mann-Whitney) (StatSoft, Inc. 2001) statistical packages.
3. Results A total of 25 taxa (8 species, 3 group of species, 12 genera and 2 higher taxa) were collected and identified during the study (Table III). The fauna was qualitatively dominated by insects and secondarily by oligochaetes. The highest number of taxonomic units were found in the pond 2 (20 taxa). This pond was also ranked highest in macroinvertebrates density, there the average number was 9928 ind. m-2 during period of surveys. The average number of benthic fauna in pond 1 was significantly lower (p<0.01) – 3060 ind. m-2 and also the lowest taxonomic richness (15 taxa) were noted there. In the quantitative structure the
Table III. Mean abundance values (ind. m-2) ±standard deviation and frequency (F) of macrozoobenthic taxa collected in the studied ponds. Taxa Oligochaeta Chaetogaster langi Bretscher Pristina aequiseta Bourne Stylaria lacustris (L.) Limnodrilus hoffmeisteri Claparède Limnodrilus juv. Tubificidae juv. Hirudinea Erpobdella octoculata (L.) Hydracarina Ephemeroptera Caenis horaria (L.) Ephemerella sp. Chaoboridae Chaoborus flavicans Meigen Ceratopogonidae Chironomidae Procladius sp. Tanypus sp. Hydrobaenus sp. Chironomus plumosus gr. Cladopelma laccophila gr. Cladopelma lateralis gr. Cryptochironomus sp. Einfeldia sp. Glyptotendipes sp. Microchironomus sp. Polypedilum sp. Tanytarsus sp. Lepidoptera Parapoynx stagnata Donovan
1 Mean±SD
19±49 131±292 37±64 75±103
F
14 29 29 43
Ponds 2 Mean±SD
F
19±49
14
802±646 5449±885 37±64
3 Mean±SD
F
19±49
14
100 411±567 43 100 1941±1662 100 29 168±164 57
B 0
37±99
14
37±99
14
37±64 205±249
29 57
168±180 224±375 93±195 914±1487 19±49 19±49 19±49 149±341 1344±2209 168±247 19±49 131±131
57 57 29 43 14 14 14 29 43 43 14 57
19±49
14
19±49 19±49
14 14
56±148
14
37±99 131±200 2874±3561 541±1043 56±103
14 43 86 71 29
19±49
14
75±127 19±49 112±244 224±195
29 14 29 71
19±49
14
B 1
B 2
B 3
19±49
14
37±64
29
131±226 75±103
29 43
2165±2524
71
19±49
14
19±49 75±148 19±49 37±64 187±103
14 29 14 29 86
B 4
J. Koszałka, S. Tucholski
316
100%
others
80%
Chironomidae Oligochaeta
60%
40%
20%
0% pond 1
pond 2
pond 3
Fig. 1. Percentage composition of macroinvertebrate communities at the studied ponds.
Table IV. Similarities (Bray Curtis distance) of the zoobenthic assemblages of studied ponds.
16000 14000
pond 1 others
12000
Chironomidae 10000 ind m-2
of quantitative composition, respectively), whereas oligochaetes were the most important in pond 2 accounting for 64% of total mean density. Tubificid worms Limnodrilus were caught here in large number and was responsible for more than 63% of total abundance. Also in pond 3 it was a dominant taxon (35%). Moreover, Limnodrilus was found in all sampling occasions in ponds 1 and 2 (Table III). Analysis of the assemblages of benthic fauna of ponds using the Bray-Curtis similarity coefficient test yielded the matrix shown in Table IV.
Pond 1 Pond 2 Pond 3
Oligochaeta
8000
Pond 1 0.000 0.746 0.741
Pond 2
Pond 3
0.000 0.574
0.000
6000 4000
As clearly observed the zoobenthos of all ponds were different, but community of pond 2 and pond 3 did not differ significantly (similarity at 43%). During the study period, the number of taxa presented large oscillations in ponds, varying from 1 in April to 9 in August in pond 1, from 5 (April, June, September) to 12 (July) and from 3 (April, October) to 12 (July, August) in ponds 2 and 3, respectively. Abundance of macroinvertebrates showed a similar trend, when comparing data between studied ponds, with extremely low values observed in April and October in pond 1 and 3, and a peak in July (pond 1 and 2) or in August (pond 3) (Fig. 2). The chironomids and the oligochaetes were visible dominant during all studied period. The minimum value of a total abundance of zoobenthos observed in pond 1 in April (261 ind..m-2), and the highest density was observed in pond 3 in August (15 545 ind..m-2). The minimum value of a total abundance of zoobenthos recorded in pond 2 (7838 ind..m-2) was higher than the maximum value observed in pond 1 (7185 ind..m-2).
2000 0
16000 14000
pond 2
12000
ind m-2
10000 8000 6000 4000 2000 0 16000 14000
pond 3
12000
ind m-2
10000 8000 6000 4000 2000 0
IV
V
VI
VII Months
VIII
IX
X
Fig. 2. Seasonal changes in population density of oligochaetes, chironomids and other benthic macroinvertebrates in ponds during the study.
dominant groups were chironomids and oligochaetes constituing 98% of the total zoobenthos abundance in each of studied ponds (Fig. 1). Chironomids were the most abundant faunal group in pond 1 and pond 3 (90% and 60%
4. Discussion
The number of species found in ponds from various geographic regions change within a wide range. As already observed, the highest richness value were found in densely vegetated ponds with low concentrations of total phosphorus, the lo-
Zoobenthos of ponds supplied with biologically treated sewage
west (<20) in highly degraded ones (Trigal et al. 2007). Our results are in agreement with this. In studied parts of ponds submerged vegetation of elodeids do not occur, and a narrow belts of helophytes can be found only along the shore. During the decomposition of organic matter in sediments phosphates are liberated (Hillerod 1974). Wastewater fertilizations of ponds supports this process by providing substrate for decomposition. Ponds containing no fish possess a rich and varied assemblage of aquatic animals (Whitman et al. 1988). In addiction, almost entire lack of lower trophic level carnivores and not numerous invertebrate predators in studied ponds may be an effect of introduction of ichthyofauna. The taxonomic composition of zoobenthos in the investigated ponds was typical of eutrophicated waters. Overall, the fauna of the ponds was dominated by chironomids and the remaining taxa consist nearly entirely of Oligochaeta. Such a result is also typical in fish ponds (Lellák 1981), and the quantity of benthic macroinvertebrates fluctuated in dependence on these two groups what agrees with the observation of Adamek and Sukop (1995). The composition of the midges community showed no significant differences between the three ponds and the majority of collected taxa are common for eutrophic lakes and ponds, particulary in muddy sediments or layer of organic matter. Dominant genera are Chironomus, which feed on this kind of substances (Wasilewska 1978) or Procladius, known as predator-engulfers of Protozoa, microcrustaceans, and aquatic insects (Coffman, Ferrington 1996). Clear dominance of Limnodrilus hoffmeisteri, particulary in pond 2, may be (according to Milbrink 1978) a result of replacing the former species caused by increasing quantities of nutrients supplied with sewage. The higher density of oligochaetes indicated the detrital rich habitats they occupy. In pond 2 Limnodrilus dominated, what suggests that the fish limited density of Chironomidae population by feeding directly on the bottom. Chironomids larvae are fed much more intensively than Oligochaeta (Lellák 1978) and the common carp may eat the midge larvae for the almost entire duration of culture even the small fry (Szlauer, Szlauer 1980). There was no relationship beetween the European pike-perch stocking and domination of worms in pond 2. Peterka et al. (2003) have reported that dominant food items of juveniles pikeperch are copepods and cladocerans, and chironomids constitued 1% in the diet. Intensity of consumption of bottom fauna by fishes adapted to feeding on muddy sediments increases with their growth, according to the theory of optimal foraging (Werner, Hall 1974). With the concomitance of the emergence of temporary fauna of ponds this can explain the seasonal variations of abundance. Lellák (1981) observed the most intense emergence of Chiro-
317
nomidae in April which with varying intensity extended till the end of September or October. High densities in summer are related to the life cycle of the macrozoobenthic organisms and to the presence of newly hatched specimens. The results of the study demonstrate that under rearing conditions the stability of seasonal pattern of macrozoobenthos density is dependant mostly on the initial share of permanent elements of fauna in benthic assemblage of pond. Our survey revealed a high variation in bottom fauna community composition among adjacent ponds. Despite the same maintaining and the area of ponds, similar waters parameters, the benthic assemblages tends to be differentiated. There may be severe reasons why indirectly connected water bodies exhibit variability in total and relative abundance and faunistic similarity of zoobenthic communities. Firstly, water flow in ponds with underground springs may act as an important source of disturbance for zoobenthos assemblage. Conclusions The taxonomic composition of zoobenthos in the investigated ponds, fed with biologically treated wastewater and stocked with fish, was typical of eutrophicated waters. The ponds differed with respect to the taxonomic structure and densities of benthic fauna, despite the absence of differences in the physicochemical parameters of water and in the volume of wastewater introduced, and the fact that they were stocked with the same species of benthivorous fish. The presence of underground springs at the bottom of ponds no. 2 and 3 and fish predation pressure most probably affected the composition of aquatic macroinvertebrate communities. Acknowledgements The study was supported by grant N N305 2777 33 from Ministry of Science and Higher Education, Poland.
5. References Adamek, Z., Sukop, I. 1995. Zooplankton and zoobenthos development in ponds stocked with tench fry in mono- and polycultures with herbivorous fish. Pol. Arch. Hydrobiol. 42, 181-186. Broza, M., Halpern, M., Inbar, M. 2000. Non-biting midges (Diptera; chironomidae) in waste stabilization ponds: an intensifying nuisance in Israel. Water Sci. Technol. 42, 71–74. Coffman, W.P., Ferrington, L.C. 1996. Chironomidae. In: Merrit, K.W., Cummins, R.W. [Eds]. An introduction of aquatic insects of North America. Kendall Hunt Publishing, Dubuque, pp. 635-754.
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Dave, G. 1989. Experiences with wastewater-cultured Daphnia in the start-feeding of rainbow trout (Salmo gairdneri). Aquaculture 79, 337-343. Dhawan, A., Kaur, S. 2002. Effect of pig dung on water quality and polyculture of carp species during winter and summer. Aquacult. Int. 10, 297–307. Goździejewska A., Tucholski S. 2010. In press. Zooplankton of fish culture ponds periodically fed with treated wastewater. Polish J. Environ. Stud. Guerrin, F. 1988. Valorisation du zooplancton produit en étangs de lagunage comme base pour l’alimentation de juvéniles de Cyprinidés. Bull. Fr. Peche Piscicult. 311, 113-125. Hall, D.J., Cooper, W.E., Werner, E.E. 1970. An experimental approach to the production dynamics and structure of freshwater animal communities. Limnol. Oceanogr. 15, 839-928. Hare, L., Carignan, R., Huerta-Diaz, M.A. 1994. A field study of metal toxicity and accumulation by benthic invertebrates; implications for the acid-volatile sulfide (AVS) model. Limnol. Oceanogr. 39,1653-1668. Hillerod, V.J.M.A. 1974. Nitrogen and phosphorus budgets and the role of sediments in six Danish lakes. Archive für Hydrobiologie 74, 528–550. Jonasson, P.M. 1972. Ecology and production of the profundal benthos in relation to phytoplankton in Lake Esrom. Oikos Supplement 14, 1-148. Kovach, W. 2006. Multivariate Statistical Package V.3.13n Kovach Computing Services, Anglesey, Wales, UK. Lellák, J. 1978. Population dynamics of the bottom fauna and its respect to the fish stock in the carp pond. Verh. Internat. Verein. Limnol. 20, 2194. Lellák, J. 1981. Loss of bottom fauna production resulting from. emergence of adult Chironomidae in carp ponds. Verh. Internat. Verein. Limnol. 21, 1183-1186.
Milbrink, G. 1978. Indicator communities of oligochaetes in Scandinavian lakes. Verh. Internat. Verein. Limnol. 20, 2406-2411. Pelczarski, W. 2004. Mass rearing of juvenile whitefish in brackish water using live zooplankton. Ann. Zool. Fenn. 41, 165-170. Peterka, J., Matěna, J., Lipka, J. 2003. The diet and growth of larval and juvenile pikeperch (Stizostedion lucioperca (L.)): A comparative study of fishponds and a reservoir. Aquacult. Int. 11, 337-348. StatSoft, Inc. 2001. STATISTICA (data analysis software system), version 6. www.statsoft.com. Szlauer, B., Szlauer, L. 1980. The use of lake zooplankton as feed for carp (Cyprinus carpio L.) fry in pond culture. Acta Ichthyol. Pisc. 10, 79-102. Trigal, C., García-Criado, F., Fernandez-Aláez, C. 2007. Macroinvertebrate communities of mediterranean ponds (North Iberian Plateau): importance of natura and human-induced variability. Freshwat. Biol. 52, 2042-2055. Tucholski, S. 1994. Chów ryb w stawach zasilanych biologicznie oczyszczonymi ściekami [Fish breeding in ponds supplied with biological treated sewage] Wydaw. IRŚ, Olsztyn. Wasilewska, B.E. 1978. Bottom fauna in ponds with intense fish rearing. Ekol. Pol. 26, 512-536. Werner, E.E., Hall, D.J. 1974. Optimal foraging and the size selection of prey by the bluegill sunfish (Lepomis macrochirus). Ecology 55, 1042-1052 Whitman, R.L., Gochee, A.V., Ruckman, P.L. 1988. Biological assemblages of Miller Woods ponds, Indiana Dunes National Lakeshore, Gary, Indiana. Verh. Internat. Verein. Limnol. 23, 1041-1048. Wohlfarth, G.W., Schroeder, G.L. 1979. Use of manure in fish farming – a review. Agr. Wastes 1, 279-299.
Zoobenthic assemblages of ponds supplied with biologically treated sewage
Jacek Koszałka1, Stefan Tucholski2 1
Department of Applied Ecology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 5, 10-957 Olsztyn, Poland [email protected] 2 Department of Land Reclamation and Management, University of Warmia and Mazury in Olsztyn, Plac Łódzki 2, 10-719 Olsztyn, Poland
Abstract The composition of benthic macroinvertebrate communities were studied in three interconnected earth fish ponds in the sewage treatment plant in Olsztynek. These ponds were fed with biologically treated wastewater and stocked with the common carp (Cyprinus carpio L.), tench (Tinca tinca L.), European pike-perch (Sander lucioperca (L.)) and roach (Rutilus rutilus L.). Zoobenthos was sampled monthly between April and October 2007. The dominant taxa were Chironomidae and Oligochaeta. Ceratopogonidae and Ephemeroptera were scarce. Taxon richness was low. The total densities of bottom fauna of ponds varied from 3060 ind. m-2 to 9928 ind. m-2 in pond 1 and 2, respectively. Abundance of the total zoobenthos of three ponds showed similar temporal patterns with a peak in mid summer and a minimum in early spring and fall. The fauna of ponds were partially similar and indicated high trophy and impact of fish. The presence of underground springs at the bottom of ponds no. 2 and 3 probably affected the composition of aquatic macroinvertebrate communities. Key words: pond, zoobenthos, wastewater supply.
1. Introduction Wastewater is characterized by high nutrients content, and introduction of such fertilizers into aquatic ecosystem brings considerable effects on the life of organisms. Therefore, trophic potential of sewage is exploited in rearing zooplankton for fish feeding (Guerrin 1988; Dave 1989; Pelczarski 2004) or for supplying nutrients to ponds where rearing of whitefish were conducted (Tucholski 1994). In fish culture the
direct enrichment of the pond with organic allochtonic substances, as a pig manure (Dhawan, Kaur 2002) or animal wastes (Wohlfarth, Schroeder 1979) is used for fertilization in order to enhance plankton production. Benthic organisms are recognized as an important part of the foodcycle in fish ponds and the indirect influence of the fish on zoobenthos through their control of filter-feeding zooplankton is very strong (Lellák 1978). Therefore fertilization may have a distinct positive effect to increase both benthic and fish
J. Koszałka, S. Tucholski
314
Table I. Main physico-chemical characteristics of the 3 ponds during the period of study (based on unpublished data of second author). Variable Temperature (0C) Dissolved oxygen (mg dm-3) pH Temperature (0C) Dissolved oxygen (mg dm-3) pH Temperature (0C) Dissolved oxygen (mg dm-3) pH
Date 2.04.07 7.05.07 4.06.07 2.07.07 1.08.07 3.07.07 2.10.07 Pond 1 12.2 15.6 19.6 19.6 17.9 15.9 14.4 16.0 12.9 4.0 4.6 5.6 9.0 10.1 8.7 8.8 7.8 8.5 7.8 8.5 8.7 Pond 2 9.5 15.7 18.0 17.3 16.7 14.9 13.7 19.0 12.6 4.5 3.8 7.5 14.6 7.7 8.8 8.5 7.5 8.1 7.9 8.7 8.2 Pond 3 9.8 15.5 17.9 19.1 17.3 15.0 13.6 13.4 18.3 6.0 8.7 6.1 5.8 10.5 8.2 9.1 7.6 8.4 7.6 8.0 8.4
production in ponds (Hall et al. 1970; Wasilewska 1978). Chironomus larvae, the predominant form in many shallow lentic habitats including ponds (Broza et al. 2000). Their large size and high biomass make these organisms a potentially important food resource for fish (Jonasson 1972). The mass emergence of adult insects in wastewater ponds where no presure of fish and macroinvertebrate predators occurres may cause nuisance or medical problems (Broza et al. lc.). Emergence of adult insect is also an important path of organic matter and nutrients loss form the aquatic ecosystem (Lellák 1981). Benthic invertebrate species are funcional component of fish pond ecosystem, not only as prey items consumed by fish, but they also can play a role as parasite-transmitting vectors (Brinkhurst 1997) or bioaccumulators of heavy metals and chemicals (Hare et al. 1994). The aim of this study was to analyze the qualitative and quantitative composition of benthic communities and the patterns of their seasonal changes in three ponds fed with a similar amount of biologically treated wastewater and stocked with the same species of benthivorous fish.
it was periodically fed into the ponds, in comparable quantities. The surface area of the experimental ponds was as follows: pond no. 1 – 1.04 ha, pond no. 2 – 0.94 ha, pond no. 3 – 1.00 ha. The maximum depth in summer was 1.5 m in each of the ponds. The studied reservoirs were filled with water from underground springs at the bottom of ponds no. 2 and 3. The ponds were characterized by similar physicochemical parameters of water (Table I). The periodic introduction of treated wastewater to the ponds did not cause oxygen deficits. The ponds were stocked with the common carp (Cyprinus carpio L.), tench (Tinca tinca L.), European pike-perch (Sander lucioperca (L.)) and roach (Rutilus rutilus L.) (Table II). The tench and roach were stoked into the ponds in the middle of November 2006, and the European pike-perch and carp (0+) were stocked in the middle of June 2007. The average weight of individual carps aged 1+ ranged from 365.0 g fish-1 in pond no. 2 to 559.1 g fish-1 in pond no. 3, and the weight of carp aged 0+ was 1.6 fish-1 in all experimental ponds. The average weight of tench spawners reached from 342.8 g fish-1 in pond no. 3 to 944.4 fish-1 in pond no. 1. Tench aged 1+ weighed 18.3 g fish-1 in pond no. 1 and 18.2 g fish-1 in pond no. 3, while tench
2. Materials and methods A field experiment investigating fish stocking material was carried out in the production season from April to October 2007 in three interconnected earth fish ponds on the premises of a wastewater treatment plant in Olsztynek (NE Poland). Raw wastewater fed to the treatment plant comprised household sewage as well as wastewater from a fruit and vegetable processing plant. Following preliminary treatment and the removal of screenings and sand, wastewater was treated in sequencing batch reactors (SBR), and
Table II. The species and the age structure of fish used for pond stocking. Modified from Goździejewska, Tucholski (2010, in press). The species and the age structure Cyprinus carpio L. (1+) C. carpio (0+) Tinca tinca L. spawners T. tinca (1+) T. tinca (0+) Sander lucioperca (L.) (0+) Rutilus rutilus L. (0+)
1 + + + + + +
Pond 2 + + + + +
3 + + + + + -
Zoobenthos of ponds supplied with biologically treated sewage
in the 0+ age category – 1.0 g fish-1 in ponds no. 1 and 3. The average individual weight of roach hatchlings and European pike perch hatchlings was 2.5 g fish-1 and 0.15 g fish-1, respectively. The presence of tench fry aged 0+ was noted during fish harvest in ponds no. 1 and 3 in the autumn of 2007. The hatchlings were the offspring from natural spawning of tench in those ponds (Goździewska, Tucholski 2010 in press). At each pond three samples were collected using a Kajak sampler (collecting area: 25.5 cm2) at the center and at the halfway point between the center and edge of the pond. Samples were washed through a 0.5 mm mesh size sieve . The material was sorted under a stereoscopic microscope, fixed and preserved in 4% formalin. Animals were identified to the lowest taxonomic unit possible. Bray Curtis distance matrix was applied to determine similarity and Mann-Whitney’s non parametric U-test was used to test differences in community abundances between the three ponds.
315
Described above analyses were performed using MVSP (Bray-Curtis) (Kovach 2006) and Statistica 6.0 (Mann-Whitney) (StatSoft, Inc. 2001) statistical packages.
3. Results A total of 25 taxa (8 species, 3 group of species, 12 genera and 2 higher taxa) were collected and identified during the study (Table III). The fauna was qualitatively dominated by insects and secondarily by oligochaetes. The highest number of taxonomic units were found in the pond 2 (20 taxa). This pond was also ranked highest in macroinvertebrates density, there the average number was 9928 ind. m-2 during period of surveys. The average number of benthic fauna in pond 1 was significantly lower (p<0.01) – 3060 ind. m-2 and also the lowest taxonomic richness (15 taxa) were noted there. In the quantitative structure the
Table III. Mean abundance values (ind. m-2) ±standard deviation and frequency (F) of macrozoobenthic taxa collected in the studied ponds. Taxa Oligochaeta Chaetogaster langi Bretscher Pristina aequiseta Bourne Stylaria lacustris (L.) Limnodrilus hoffmeisteri Claparède Limnodrilus juv. Tubificidae juv. Hirudinea Erpobdella octoculata (L.) Hydracarina Ephemeroptera Caenis horaria (L.) Ephemerella sp. Chaoboridae Chaoborus flavicans Meigen Ceratopogonidae Chironomidae Procladius sp. Tanypus sp. Hydrobaenus sp. Chironomus plumosus gr. Cladopelma laccophila gr. Cladopelma lateralis gr. Cryptochironomus sp. Einfeldia sp. Glyptotendipes sp. Microchironomus sp. Polypedilum sp. Tanytarsus sp. Lepidoptera Parapoynx stagnata Donovan
1 Mean±SD
19±49 131±292 37±64 75±103
F
14 29 29 43
Ponds 2 Mean±SD
F
19±49
14
802±646 5449±885 37±64
3 Mean±SD
F
19±49
14
100 411±567 43 100 1941±1662 100 29 168±164 57
B 0
37±99
14
37±99
14
37±64 205±249
29 57
168±180 224±375 93±195 914±1487 19±49 19±49 19±49 149±341 1344±2209 168±247 19±49 131±131
57 57 29 43 14 14 14 29 43 43 14 57
19±49
14
19±49 19±49
14 14
56±148
14
37±99 131±200 2874±3561 541±1043 56±103
14 43 86 71 29
19±49
14
75±127 19±49 112±244 224±195
29 14 29 71
19±49
14
B 1
B 2
B 3
19±49
14
37±64
29
131±226 75±103
29 43
2165±2524
71
19±49
14
19±49 75±148 19±49 37±64 187±103
14 29 14 29 86
B 4
J. Koszałka, S. Tucholski
316
100%
others
80%
Chironomidae Oligochaeta
60%
40%
20%
0% pond 1
pond 2
pond 3
Fig. 1. Percentage composition of macroinvertebrate communities at the studied ponds.
Table IV. Similarities (Bray Curtis distance) of the zoobenthic assemblages of studied ponds.
16000 14000
pond 1 others
12000
Chironomidae 10000 ind m-2
of quantitative composition, respectively), whereas oligochaetes were the most important in pond 2 accounting for 64% of total mean density. Tubificid worms Limnodrilus were caught here in large number and was responsible for more than 63% of total abundance. Also in pond 3 it was a dominant taxon (35%). Moreover, Limnodrilus was found in all sampling occasions in ponds 1 and 2 (Table III). Analysis of the assemblages of benthic fauna of ponds using the Bray-Curtis similarity coefficient test yielded the matrix shown in Table IV.
Pond 1 Pond 2 Pond 3
Oligochaeta
8000
Pond 1 0.000 0.746 0.741
Pond 2
Pond 3
0.000 0.574
0.000
6000 4000
As clearly observed the zoobenthos of all ponds were different, but community of pond 2 and pond 3 did not differ significantly (similarity at 43%). During the study period, the number of taxa presented large oscillations in ponds, varying from 1 in April to 9 in August in pond 1, from 5 (April, June, September) to 12 (July) and from 3 (April, October) to 12 (July, August) in ponds 2 and 3, respectively. Abundance of macroinvertebrates showed a similar trend, when comparing data between studied ponds, with extremely low values observed in April and October in pond 1 and 3, and a peak in July (pond 1 and 2) or in August (pond 3) (Fig. 2). The chironomids and the oligochaetes were visible dominant during all studied period. The minimum value of a total abundance of zoobenthos observed in pond 1 in April (261 ind..m-2), and the highest density was observed in pond 3 in August (15 545 ind..m-2). The minimum value of a total abundance of zoobenthos recorded in pond 2 (7838 ind..m-2) was higher than the maximum value observed in pond 1 (7185 ind..m-2).
2000 0
16000 14000
pond 2
12000
ind m-2
10000 8000 6000 4000 2000 0 16000 14000
pond 3
12000
ind m-2
10000 8000 6000 4000 2000 0
IV
V
VI
VII Months
VIII
IX
X
Fig. 2. Seasonal changes in population density of oligochaetes, chironomids and other benthic macroinvertebrates in ponds during the study.
dominant groups were chironomids and oligochaetes constituing 98% of the total zoobenthos abundance in each of studied ponds (Fig. 1). Chironomids were the most abundant faunal group in pond 1 and pond 3 (90% and 60%
4. Discussion
The number of species found in ponds from various geographic regions change within a wide range. As already observed, the highest richness value were found in densely vegetated ponds with low concentrations of total phosphorus, the lo-
Zoobenthos of ponds supplied with biologically treated sewage
west (<20) in highly degraded ones (Trigal et al. 2007). Our results are in agreement with this. In studied parts of ponds submerged vegetation of elodeids do not occur, and a narrow belts of helophytes can be found only along the shore. During the decomposition of organic matter in sediments phosphates are liberated (Hillerod 1974). Wastewater fertilizations of ponds supports this process by providing substrate for decomposition. Ponds containing no fish possess a rich and varied assemblage of aquatic animals (Whitman et al. 1988). In addiction, almost entire lack of lower trophic level carnivores and not numerous invertebrate predators in studied ponds may be an effect of introduction of ichthyofauna. The taxonomic composition of zoobenthos in the investigated ponds was typical of eutrophicated waters. Overall, the fauna of the ponds was dominated by chironomids and the remaining taxa consist nearly entirely of Oligochaeta. Such a result is also typical in fish ponds (Lellák 1981), and the quantity of benthic macroinvertebrates fluctuated in dependence on these two groups what agrees with the observation of Adamek and Sukop (1995). The composition of the midges community showed no significant differences between the three ponds and the majority of collected taxa are common for eutrophic lakes and ponds, particulary in muddy sediments or layer of organic matter. Dominant genera are Chironomus, which feed on this kind of substances (Wasilewska 1978) or Procladius, known as predator-engulfers of Protozoa, microcrustaceans, and aquatic insects (Coffman, Ferrington 1996). Clear dominance of Limnodrilus hoffmeisteri, particulary in pond 2, may be (according to Milbrink 1978) a result of replacing the former species caused by increasing quantities of nutrients supplied with sewage. The higher density of oligochaetes indicated the detrital rich habitats they occupy. In pond 2 Limnodrilus dominated, what suggests that the fish limited density of Chironomidae population by feeding directly on the bottom. Chironomids larvae are fed much more intensively than Oligochaeta (Lellák 1978) and the common carp may eat the midge larvae for the almost entire duration of culture even the small fry (Szlauer, Szlauer 1980). There was no relationship beetween the European pike-perch stocking and domination of worms in pond 2. Peterka et al. (2003) have reported that dominant food items of juveniles pikeperch are copepods and cladocerans, and chironomids constitued 1% in the diet. Intensity of consumption of bottom fauna by fishes adapted to feeding on muddy sediments increases with their growth, according to the theory of optimal foraging (Werner, Hall 1974). With the concomitance of the emergence of temporary fauna of ponds this can explain the seasonal variations of abundance. Lellák (1981) observed the most intense emergence of Chiro-
317
nomidae in April which with varying intensity extended till the end of September or October. High densities in summer are related to the life cycle of the macrozoobenthic organisms and to the presence of newly hatched specimens. The results of the study demonstrate that under rearing conditions the stability of seasonal pattern of macrozoobenthos density is dependant mostly on the initial share of permanent elements of fauna in benthic assemblage of pond. Our survey revealed a high variation in bottom fauna community composition among adjacent ponds. Despite the same maintaining and the area of ponds, similar waters parameters, the benthic assemblages tends to be differentiated. There may be severe reasons why indirectly connected water bodies exhibit variability in total and relative abundance and faunistic similarity of zoobenthic communities. Firstly, water flow in ponds with underground springs may act as an important source of disturbance for zoobenthos assemblage. Conclusions The taxonomic composition of zoobenthos in the investigated ponds, fed with biologically treated wastewater and stocked with fish, was typical of eutrophicated waters. The ponds differed with respect to the taxonomic structure and densities of benthic fauna, despite the absence of differences in the physicochemical parameters of water and in the volume of wastewater introduced, and the fact that they were stocked with the same species of benthivorous fish. The presence of underground springs at the bottom of ponds no. 2 and 3 and fish predation pressure most probably affected the composition of aquatic macroinvertebrate communities. Acknowledgements The study was supported by grant N N305 2777 33 from Ministry of Science and Higher Education, Poland.
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