Invertebrates associated with Myriophyllum spicatum L. in Sakadaš lake within Kopački rit floodplain, Croatia Dubravka Čerba, Irella Bogut, Jasna Vidaković and Goran Palijan




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Invertebrates associated with Myriophyllum spicatum L. in Sakadaš lake within Kopački rit floodplain, Croatia
Dubravka Čerba, Irella Bogut, Jasna Vidaković and Goran Palijan
Department of Biology, University of J. J. Strossmayer, Trg Ljudevita Gaja 6, HR-31000 Osijek, Croatia; e-mail: dcerba@vip.hr ibogut@ffos.hr javidako@inet.hr gpalijan@ffos.hr
Sampling of invertebrates associated with submersed macrophyte species Myriophyllum spicatum L., was conducted once a week during July, August and September 2004, at three sites, noted as I, II and III, in Sakadaš lake within Kopački rit floodplain in the North-East Croatia (Figures 1a and 1b).



II

I

III

area of Kopački rit

Čonakut Channel

Sakadaš lake

Figure 1a. Eastern part of Croatia Figure 1b. Research sites in Sakadaš lake


The weather and environmental parameters were as expected for summer season: high air temperatures, little rain, what influenced water temperature as well as decrease in depth and transparency (Table 1).
Table 1. Mean values of environmental parameters during research period in 2004 in Sakadaš lake

Environmental parameters

14.7.

21.7.

28.7.

4.8.

12.8.

18.8.

25.8.

1.9.

8.9.

water temp. ( °C)

23.7

27

23.8

24.8

25.3

24

23

22.5

21.2

depth (m)

2.8

2.4

1.3

1.4

0.8

0.5

0.5

0.9

0.6

SD (m)

1.2

1.1

0.8

0.6

0.6

0.4

0.5

0.6

0.5

O2 (mgl-1)

3.9

4.7

3.9

7.9

9.7

8.2

12.2

9.1

10.1

chl-a (µgl-1)

28.9

11.4

38.4

30.5

40.8

44.6

45.2

52.9

48.5

T-P (mgl-1)

0.1

0.1

0.2

0.1

0.1

0.1

0.1

0.5

0.04

There was a statistical significance in difference between environmental parameters recorded in July and those recorded in August (R=0.647, p<0.001) and September (R=0.739, p<0.001) (Figure 2), but there was no statistically important difference between sites for environmental parameters.


Figure 2. NMDS plot of environmental parameters recorded at the research sites


Calculated TSI values (Carlson and Simpson, 1996), based on concentration of chlorophyll-a and amount of T-P, indicated states of eutrophy and hypertrophy, for some dates, what is analogue to results gathered during reseach conducted from 1997 to 2004 (Vidaković et al., 2002; Bogut et al., 2003).

Myriophyllum spicatum first appeared in Sakadaš lake in the year 2004 and then the research on phytophilous invertebrate fauna began. In collected fauna we recorded 23 taxonomic groups and they are presented by their abundance as number of individuals per 100 g plant dry weight (Table 2).
Table 2. Mean invertebrate abundances (ind. 100 g-1 d.w.) at sites during research period

sites

I

II

III

Zygoptera

167.5

156.8

61.8

Anisoptera

0

0

3.4

Chironomidae

6743

7572.4

2891.2

Hemiptera

23.1

0

0

Ephemeroptera

56.6

44.4

12.2

Ceratopogonidae

8.4

101.9

39.4

Plecoptera

4.2

0

0.7

Trichoptera

0

5.2

0

Heteroptera

0

3.1

0

Muscidae

0

0

0.7

Dytiscidae

0

0

0.7

Oligochaeta

104.9

243.4

1740.5

Cladocera

182.3

148.4

314.6

Nematoda

75.4

92.9

2435.4

Copepoda

213.7

32

61.1

Nauplii

69.2

136.2

199

Insecta

23

3.1

4.1

Turbellaria

8.4

97

76.9

Gastropoda

6.3

20.6

6.1

Hydrozoa

2.1

2.1

12.9

Bivalvia

0

0

1.4

Hirudinea

2.1

0

0

Hydracarina

2.1

0

0

total

54000.8

62587.2

43458

S

17

15

18

Dominance in recorded invertebrate fauna had Insecta larvae (representatives of Zygoptera, Anisoptera, Chironomidae, Hemiptera, Ephemeroptera, Ceratopogonidae, Plecoptera, Trichoptera, Heteroptera, Dytiscidae and Muscidae), with the percentage rate ranging from 42% to 90% of total fauna at the research sites (Figure 3).




Figure 3. Percentage rate of invertebrates at each site
The highest abundance (47258.9 individuals per 100 g of M. spicatum dry weight at the site I, 53886.4 ind. 100 g-1 d.w. at the site II and 17739.9 ind. 100 g-1 d.w. at the site III) was found for members of the family Chironomidae (Table 2), what is 71% of all invertebrates at all three sites. At the site III high densities had Nematoda with 12086.3 ind. 100 g-1 d.w. and Oligochaeta with 9235 ind. 100 g-1 d.w, what representes 28% and 21% of all invertebrates at that site (Figure 3).
Very successful invertebrates, present in high abundance in eutrophic waters are Chironomidae larvae (Lund, 2001) and Oligochaeta (Mackie, 2001). Predominance of Chironomidae larvae is usual in eutrophic waters associated with macrophytes (Soszka, 1975; Linhart, 1999). According to the non-metric multidimensional scaling, NMDS, and analysis of similarities, ANOSIM, statistically significant difference exists in invertebrate abundances between the site I and the site III (R = 0.772, p < 0.005), as well as between the site II and the site III (R = 0.514, p < 0.01) (Figure 4).

Figure 4. NMDS plot showing difference in invertebrate abundances between the research sites


Also, there is statistically significant difference between months of sampling: July and August (R=0.647, p<0.001) and also July and September (R=0.739, p<0.001), regarding fauna abundance (Figure 5).

Figure 5. NMDS plot showing difference in invertebrate abundances between months


Statistically significant correlation (p<0.02) was found between invertebrate number and M. spicatum dry weight at the site III. These results could be explained by the fact that the M. spicatum stand at the site III lasted continuously over the whole sampling period, while the stands at the sites I and II did no longer exist after the first half of August 2004.
References:

Bogut I, Vidaković J, Palijan G. 2003. Trophic state and water quality in Kopački rit during 2002. In: 3rd Croatian Confrence on Waters, Croatian Waters in the 21st Century. p 173-179.

Carlson RE, Simpson J. 1996. A Coordinator’s Guide to Volunteer Lake Monitoring Methods. North American Lake Management Society. 96 p.

Linhart J. 1999. Phytophilous macrofauna in the Stratiotes aloides vegetation of the Lake Łukie, Poland. Acta Univ Palacki Olomuc, Fac rer nat, Biol 37:67-76

Lund MA. 2001. Nuisance midge (Chironomidae) plagues in urban wetlands: A catalyst for improved catchment management In: Proceedings of the 28th National Environmental Health Conference (CD-Rom), Australian Institute of Environmental Health, 14th-19th October 2001 Perth.

Mackie GL. 2001. Applied Aquatic Ecosystem Concepts. Kendall/Hunt Publishing Company. 744 p.



Soszka GJ. 1975. The invertebrates on submersed macrophytes in three Masurian lakes. Ekol Pol 23: 271-391.

Vidaković J, Bogut I, Borić E, Zahirović Ž. 2002. Hydrobiological research in the Kopački rit Nature Park in the period November 1997 – October 2001. Hrvat Vode 10(39):127-144.


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