63J. Elementol. 2007, 12(1): 63–79

CHEMICAL COMPOSITION OF REEDPHRAGMITES AUSTRALIS (CAV.) TRIN.

EX STEUD. VERSUS DENSITYAND STRUCTURE OF PERIPHYTONIN VARIOUS AQUATIC ECOSTSEMS

Krystian Obolewski1, Agnieszka Strzelczak2,Anna Kiepas-Kokot3

1Department of Ecology and Protection of the Sea,Pomeranian Pedagogical University in S³upsk

2Institute of Chemistry and Environmental Protection,Szczecin University of Technology

3Department of Environmental Protection and Management,Szczecin University of Agriculture

Abstract

Analyses of three macroelements and six microelements in reed stems, accompanied by in-vestigation of periphyton density were carried out in two reservoirs: ¯arnowieckie Lake and PuckBay. To reveal the influence of chemical composition of biotic substrate on periphyton qualitativeand quantitative characteristics, ordination methods were applied (PCA, CCA, DCA, RDA). Theresults indicated that Copoepoda (Harpacticoida) and Chlorophyta preferred reed substrate withrelatively high zinc, sulfur and chromium but low manganese and carbon content. In turn, Nema-toda reached the highest density on a substrate rich in manganese. Mercury in reed limited densi-ty of Arachnidae-Hydrachnella and Chironomidae larvae, an effect which was not observed forCiliata libera. Copepoda (Harpacticoida) preferred low chromium and lead content and high car-bon/nitrogen ratio, which meant low nitrogen concentration in the reed substrate. Moreover, pref-erences of Nematoda and Bacillariophyta for freshwaters and Copepoda for brackish waters wereindicated

The results presented in this paper should be treated as a contribution to more detailedresearch on interactions between reed chemical composition and periphyton density.

Key words: reed, content of chemical elements, periphyton, ordination.

dr Krystian Obolewski, Zak³ad Ekologii i Ochrony Morza, Pomorska Akademia Pedagogiczna,ul. Arciszewskiego 22b, 76-200 S³upsk, e-mail: obolewsk@pap.edu.pl

64

WSTÊPNA OCENA WP£YWU SK£ADU CHEMICZNEGO TRZCINY PHRAGMITESAUSTRALIS (CAV.) TRIN. EX STEUD. NA WIELKOŒÆ ZAGÊSZCZENIA

OBRASTAJ¥CEGO J¥ PERIFITONU

Krystian Obolewski1, Agnieszka Strzelczak2, Anna Kiepas-Kokot3

1Zak³ad Ekologii i Ochrony Morza,Pomorska Akademia Pedagogiczna w S³upsku

2Instytut Chemii i Ochrony Œrodowiska,Politechnika Szczeciñska

3Katedra Ochrony i Kszta³towania Œrodowiska,Akademia Rolnicza w Szczecinie

Abstrakt

Dokonano analiz zawartoœci trzech makro- i szeœciu mikrosk³adników w ³odygach trzciny orazzagêszczenia obrastaj¹cego j¹ perifitonu w dwóch akwenach: Jeziorze ¯arnowieckim i ZatocePuckiej. W celu uchwycenia wp³ywu sk³adu chemicznego pod³o¿a na sk³ad jakoœciowy i iloœciowyorganizmów poroœlowych zastosowano metody ordynacyjne (PCA, CCA, DCA, RDA). Stwierdzono,¿e Copepoda (Harpacticoida) oraz Chlorophyta preferuj¹ pod³o¿e trzcinowe o relatywnie wysokiejzawartoœci cynku, siarki i chromu, natomiast niskiej manganu i wêgla. Z kolei Nematodaw najwiêkszym zagêszczeniu wystêpuje na pod³o¿u bogatym w mangan. Hg w trzcinie limitujezagêszczenie Arachnidae-Hydrachnella oraz Chironomidae larvae, czego nie obserwuje siê w przy-padku Ciliata libera. Copepoda (Harpacticoida) preferowa³y niskie stê¿enie chromu i o³owiu,wysoki stosunek zawartoœci wêgla do azotu, a tym samym niskie stê¿enie azotu w pod³o¿u trzcino-wym. Ponadto wykazano s³odkowodne preferencje Nematoda i Bacillariophyta i s³onowodneCopepoda (Harpacticoida)

Prezentowane w niniejszej pracy wyniki nale¿y traktowaæ jako przyczynek do g³êbszych badañnad powi¹zaniem sk³adu chemicznego trzciny i zagêszczeniem perifitonu.

S³owa kluczowe: trzcina, zawartoœæ pierwiastków, perifiton, ordynacje.

INTRODUCTION

Occurrence of plant species in a reservoir is determined by its trophic state,oxygenation, thermal conditions and contamination. Biodiversity and chemical com-position of plants may indicate the present condition and changes in a habitat(HOOTSMANSM, VERMAAT 1992, KIRYLUK 2005, STANISZEWSKI et al. 2004). Commonreed Phragmites australis is a widely-spread rush species in coastal lakes. Thisplant determines the trophic state as it influences concentration of biofile ele-ments, which it accumulates in tissues and subsequently releases to a habitat, thusaccelerating eutrophication (PIECZYÑSKA 1988).

Due to its widespread occurrence as well as an ability to accumulate pollut-ants, reed is a preferred botanical treatment plant, referred to as “a reed treat-ment plant”. Tissues of this macrophyte can accumulate both nutrients and heavy

65

metals (DE LAING et al. 2006, KIRYLUK 2005 et al. 1997). Additionally, reed is aneasily accessible vertical substrate for a large group of aquatic organisms, calledperiphyton or epiphytic organisms (PIESIK, OBOLEWSKI 2000).

The first studies on periphyton concerned protection of hydrotechnical equip-ment against overgrowing by these organisms (RELINI, ORSI 1970). Factors poten-tially influencing epiphytic communities are light, temperature, motion of waves,type of substrate, water chemistry and feeding on periphyton (ALLAN 1998, MIHAL-JEVIÆ et al. 1998). Although the influence of the consecutive factors has beenstudied, scant information is available on chemical fight of reed against epiphyticorganisms. Aquatic plants, including reed, release chemical substances containingheavy metals, which can reduce the density of more sensitive periphyton organ-isms (BURK et al. 2000, LAKATOS et al. 1999). This has also been proved bycomparative studies of epiphytic communities on artificial and biotic substrate(PIESIK, OBOLEWSKI 2000, OBOLEWSKI 2006). Difficulties revealing the direct impactof a biotic substrate chemical composition on perihyton density are mainly causedby overlapping influences of the consecutive factors affecting the overgrowingprocesses. However, it has been observed that periphyton prefers some rockysubstrates. In the streams of Montana, Chrysophyta (Hydrurus sp.) appeared most-ly on limestone, Chlorophyta (Monostroma sp.) on rocks rich in iron, while Rhodo-phyta (Batrachosperum sp.) did not show any preferences of this kind (ALLAN

1998).The objective of this study was to carry out a preliminary assessment of the

relationships between chemical composition of reed, with special emphasis onheavy metals, and density of periphyton in reservoirs with different environmentalconditions, namely in coastal ¯arnowieckie Lake and Puck Bay.

MATERIALS AND METHODS

Sampling sitesThe study was conducted in freshwater ¯arnowieckie Lake (lying in a cryp-

todepression) and saline Puck Bay (Figure 1). The lake, located in the Wysoczyzna¯arnowiecka, covers an area of 1431 ha, is 7.6 km long and 2.6 km wide, andits maximum depth is 16 m. There is a river, the Piaœnica River, which flowsthrough the lake. It is only the western shore of the lake which is covered withrushes, mainly reed and common club-rush. The sampled area of Puck Bay wasan internal bay between Puck and Jastarnia, which is under influence of freshwa-ters from a tributary called the Plutnica.

Reed samples were collected in ¯arnowieckie Lake in June, 2005, at 6sampling sites, evenly distributed along the western shore of the lake. Recently,fields of reed in Puck Bay have been considerably reduced due to some earth-

66

works conducted in that area. Moreover, reed avoids saline waters, limiting itsoccurrence to a narrow, coastal strip. As a result, only 3 sampling sites werechosen.

Fragments of reed were sampled from the outer zone of fields of reed (depth0.5–1.0 m) by cutting out 3 shoots at each sampling site. Then, 3 segments,10–12 cm long, were cut out form every shoot at three levels: surface (just belowthe water surface), middle and bottom (in total 9 sub-samples). Reed samplingwas followed by analyses of the periphyton removed from the reeds according tothe methodology given by OBOLEWSKI (2006).

The dry plant material was homogenized in a laboratory mill. Concentrationsof N, C and S were directly analyzed using an elementary analyzer CNS. Con-centrations of heavy metals (Zn, Mn, Cd, Pb except for Hg), were determinedafter wet mineralization of the plant material in a closed microwave system, usinga mixture of concentrated nitric and perchlorate acids (4:1 V/V) with addition of30% hydrogen dioxide solution. The material was analyzed for metal concentra-tions with flame atomic absorption spectrometry. Hg content in the samples wasdetermined by direct combustion in oxygen in an automatic mercury analyzer. Inorder to assess measuring errors, the concentrations obtained were compared toresults for two certified plant materials (mixture of herbs and tea leaves): INCT--MPH-2 and INCT-TL-1. The calculated measuring error did not exceed 5% ofthe certified value.

Prior to statistical analyses, the data set was transformed in order to obtainnormal distribution of the consecutive variables and to eliminate influence of rarespecies. The transformation was log(x+1), which is applicable to data with nullvalues and, owing to subsequent ordination analyses, enables researchers to avoidnegative values.

Fig.1. Location of sampling sites

67

Significance of differences in reed chemical composition and periphyton den-sity between the sampled reservoirs was determined by ANOVA. Homogeneity ofvariance was assessed by Brown-Forsythe test.

Next, ordinations, a widely-used family of multidimensional exploration meth-ods, were applied in order to reveal the relationships between ecological commu-nities. Interactions and redundancy between the predictors (content of chemicalelements) were explored by Principal Component Analysis (PCA), based only onchemical data, and additionally with the Variance Inflation Factor (VIF) in Canoni-cal Correspondence Analysis (CCA), which involved both reed chemical composi-tion as well as periphyton taxonomic composition. Using Detrended Correspon-dence Analysis (DCA), the gradient of DCA first axis was determined and theninteractions between reed chemical composition and epiphytic community struc-ture were determined with the help of Redundancy Analysis (RDA) (TER BRAAK

1995).ANOVA and PCA analyses were performed using STATISTICA 6.1 software

(StatSoft 2002), while CCA, DCA and RDA in R environment (the R Foundationfor Statistical Computing) (TER BRAAK 1986, LEGENDRE, LEGENDRE 1998, HILL, GAUCH

1980, OKSANEN, MINCHIN 1997).

RESULTS AND DISCUSSION

Chemical composition of reedReed from 6 sampling sites on ¯arnowieckie Lake and 3 other sites on Puck

Bay was analyzed. Content of the following chemical elements was determined:N, C, S, Hg, Zn, Cr, Mn, Cd and Pb (Table 1).

Plants absorbed considerable amounts of macroelements, with quantitiesof carbon reaching the highest concentration This is typical due to widespreadoccurrence of carbon in the environment (BALDANTONI et al. 2004). Nitrogen massfraction varied between 0.538 and 1.006% for ¯arnowieckie Lake and between0.723 and 0.906% for Puck Bay. The highest N contents were observed in reednext to a ditch supplying ¯arnowieckie Lake with water and near Puck in theP³utnica estuary. Reed can accumulate nitrogen in tissues, especially in placeswith high N concentration in environment (BERNATOWICZ 1969).

Availability of nitrogen released during organic matter decomposition dependson its C:N ratio. The ratio of carbon to nitrogen observed at all the samplingsites was high (over 32:1), which hampered mineralization of organic substanceand intensified nitrogen accumulation in plants (THOMPSON, TROEH 1978). This ratioalso indicated high vegetation level of the analyzed reed.

As for heavy metals, zinc reached the highest concentration in reed tissues -on average 12.21 mg kg-1 d.m. in ¯arnowieckie Lake and 23.73 mg kg-1 d.m.

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in Puck Bay. These values are two-fold lower than a content typical of reedgrowing in melioration ditches but comparable with plants from meadow moors(KIRYLUK 2005, URBAN, WOJCIECHOWSKA-KAPUSTA 1999).

Mercury concentration in reed was at a relatively stable level (SD – 0.004--1.012). The vicinity of ¯arnowieckie Lake and the examined area of Puck Bayare generally free of heavy industry, therefore the environment is not polluted bymercury. In reservoirs contaminated by raw municipal sewage, concentration ofHg built in reed stem tissues is considerably higher, at a level of 10.5 mg kg-1

(SZYMANOWSKA et al. 1999).ENDLER and GRZYBOWSKI (1996) analyzed aquatic plants in Wad¹g Lake near

Olsztyn. The amount of cadmium contained in common reed (on average0.035 mg kg-1) was similar to concentrations found in reed from ¯arnowieckieLake. In turn, the content of cadmium in reed from Puck Bay was comparable tothe results cited by GRZYBOWSKI et al. (2005) for reed growing near an edgeof forest, in a lake and in a melioration ditch (0.026-0.029 mg kg-1). KABATA-PEDIAS and PENDIAS (1999) assayed the lead concentration in grass from areas freeof direct contamination within the range 0.4-2.5 mg kg-1 and this suits the resultsfrom our study.

The amount of chromium in reed stems from ¯arnowieckie Lake was low,which indicated lack of industrial contamination in this reservoir. The Cr contentwas comparable to concentrations from South American palustrine fields of reed(BURKE et al. 2000), but 30-times lower than in lakes near Poznañ, influenced byraw municipal sewage (SZYMANOWSKA et al. 1999).

Compared to the investigation of reed chemical composition conducted byPEVERLY et al. (1995), the accumulation of manganese in reed from ¯arnowieckieLake was two-fold lower; in the case of reed from Puck Bay, four-fold less man-ganese was accumulated.

Periphyton densityIn ¯arnowieckie Lake, Nematoda was the dominant taxon among microzoo-

periphyton inhabiting reed (97% of the total periphyton density). Nematoda in-cludes species feeding on epiphytic algae, which in turn absorb nutrients dissolvedin water (PIESIK 1992). The remaining taxa reached much lower densities and didnot contribute considerably to the epiphytic microfauna density (Table 2). Otherinvestigations carried out in lakes and in Pomeranian Bay (OBOLEWSKI 2006, PIESIK,OBOLEWSKI 2000, PIESIK, WAWRZYNIAK-WYDROWSKA 2003) indicated Protozoa or Rota-toria as dominant taxa.

Density of macrozooperiphyton was dominated by Trichoptera, which wereparticularly abundant at the sampling site located in the ditch supplying the lake.High density of these larvae on biotic substrate in spring can be explained bytheir life cycle (CZACHOROWSKI 1998).

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Fitoperiphyton was dominated by Bacillariophyta, which made up 99% of thetotal epiphytic algae. Diatoms strongly prevail in periphyton inhabiting reed inreservoirs with moderate loading of nutrients ((PIESIK, OBOLEWSKI 2000).

The dominant taxa of microzooperiphyton in Puck Bay were Nematoda (43%)and Protozoa (26%). Eelworms feed on algae, which were abundant at the inves-tigated substrate (PIESIK 1992), while high density of Protozoa could have beenconnected to abundant and easily available bioseston. The remaining microzoope-riphyton taxa had low densities and contributed slightly to the overall epiphyticmicrofauna density (Table 3). The situation observed in Puck Bay is typical andconfirmed by other studies from northern Poland (PIESIK, OBOLEWSKI 2000, OBO-LEWSKI 2006).

Density of macrozooperiphyton was mostly influenced by Crustacea Gammarussp., which occurred only in the P³utnica’s estuary. Fitoperiphyton was dominatedby Bacillariophyta (88% of the total epiphytic algae density), which is a typicalsituation (PIESIK, OBOLEWSKI 2000).

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72

ANOVA and ordinationsStatistical analyses were performed for the whole data set (¯arnowieckie Lake

and Puck Bay jointly) and for the taxa occurring in both reservoirs: Protozoa,Ciliata libera, Peritricha, Rotatoria, Nematoda, Copepoda-Harpacticoida, Arach-nidae-Hydrachnella, Chironomidae larvae, Bacillariophyta and Chlorophyta.

Brown-Forsythe test revealed homogeneity of variance between variables for¯arnowieckie Lake and Puck Bay. Analysis of variance indicated significant(p<0.05) differences between the studied in concentrations of C, S and Zn in thebiotic substrate and in density of Nematoda, Copepoda (Harpacticoida) and Bacil-lariophyta (Table 4).

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¯arnowieckie Lake had higher content of C and S in reed but lower Znconcentration than Puck Bay. Nematoda and Bacillariophyta were more abun-dant in freshwaters, in contrast to Copepoda. As for Nematoda and Copepoda,preferences for the consecutive ecosystems can be explained- using ordinations-by chemical composition of reed substrate, but in the case of Bacillariophytasome other factors probably play a role.

PCA analysis (Figure 2) revealed strong redundancy between concentrationof S, Zn and C (Pearson’s linear correlation coefficient 0.8-0.9 for p<0.05).

According to GREGER and KAUTSKI (1992), increase in salinity expressed aselectrolytic conductivity induces higher solubility of metals. Correlation betweenthe above mentioned non-metals and zinc may be connected to Zn ability forfixing carbon and sulfur, forming carbonates and sulfates, which can accumulate

73

Fig. 2. PCA bibplot for ¯arnowieckie Lake and Puck Bay

in plant’s tissues during excessive absorption of this chemical element by a plant.Among the analyzed metals, zinc has the highest geochemical concentration, whichallows an accurate analysis and high Pearson’s correlation coefficient at the levelof r=0.72 (SKORBILOWICZ 2003). Sulfur and carbon are the main components oforganic matter. Metals, having considerable chemical affinity to organic substanc-es, fix with them forming metaloorganic complexes. Therefore, higher concentra-tion of C and N may also increase zinc concentration in plant’s tissue, due tointensive fixation of metallic ions.

In order to assure orthogonality of the predictors, concentrations of C, Znand N were excluded from the next analyses. CCA analysis for the new datasubset and VIF values lower than 10 (1.6–6.3) confirmed fulfilling the orthogonali-ty requirement (GROSS 2003).

The next stage of the investigation was a DCA analysis, used for determiningenvironmental gradients for the consecutive periphyton taxa. Values <2 indicatedmonotonic responses for chemical element contents in biotic substrate for most ofthe studied taxa (TER BRAAK 1995).

Finally, an RDA analysis was applied. Figure 3 shows RDA biplot of axis 1and 2.

74

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gH 0741.0- 4705.0 1501.0 2342.0-

rC 6427.0 5492.0- 5364.0 5103.0-

nM 4344.0- 7610.0 0983.0 1980.0

dC 2533.0- 7480.0 3212.0- 0333.0

bP 3762.0 8070.0- 2804.0 1724.0-

Fig. 3. RDA bibplot of axis 1 and 2 for ¯arnowieckie Lake and Puck Bay

Axis 1, which explained 42.22% of the total variance, was connected to S,Cr and Mn concentration in the biotic substrate. As for the second axis (20.72%of the explained variance), the highest contribution was ascribed to Hg content(Table 5).

75

Biplot scores (Figure 3, Tables 5, 6) reveal that Harpacticoida and Chloro-phyta preferred reed substrate with relatively high S and Cr but low Mn content.Taking into account correlations between the consecutive chemical element con-tents, we can conclude that the aforementioned taxa were typical of reed poor inelementary carbon (correlation C-S: r=-0.82, p<0.05) but rich in Zn (correlationZn-Mn: r=-0.73, p<0.05). Zinc, as a microelement, performs an important bio-chemical role in plant, animal and human organisms. It takes part in oxidation--reduction processes and is an indispensable component or activator of manyenzymes. In plants, it participates in transformation of organic acids, synthesis ofchlorophyll, vitamins C, B, P and also influences growth and development oforganisms. Axis 1 of RDA also suggested that Nematoda preferred reed sub-strate with high concentration of Mn but low Zn content (correlation Zn-Mn::r=-0.73, p<0.05). The results confirm that Nematoda tend to develop better infreshwaters, while Copepoda grow more abundantly in saline reservoirs.

6elbaT6alebaT

yaBkcuPdnaekaLeikceiwonra.axatnotyhpireprofserocstolpibADR

smsinagrocityhpipE)notyhpireP(

sixaADR

1ADR 2ADR 3ADR 4ADR

aozotorPlatoT 2551.0 5742.0 9001.0 6431.0-

arebil-atailiC 7484.0- 1665.0 1373.0- 1611.0

ahcirtireP 2270.0 2852.0 0890.0 4190.0-

airotatoR 9882.0 6211.0 4351.0 7850.0-

adotameN 1417.0- 4270.0 9851.0 8713.0

adiocitcapraH 8291.1 8042.0 0411.0- 6094.0

eadinhcarA 3770.0 7474.0- 3477.0- 5090.0-

eavraleadimonorihC 9740.0 2067.0- 6392.0 5812.0

atyhpoirallicaBlatoT 4462.0- 7610.0- 5881.0 5321.0

atyhpoirallicaBlainoloC 8782.0- 9201.0- 7612.0 85111.0

atyhpoirallicaBrtallecinU 9933.0- 7761.0 5840.0 1921.0

atyhporolhC 2594.0 5190.0 6553.0 2503.0-

The second RDA axis indicated that Arachnidae and Chironomidae larvaewere particularly sensitive to Hg concentration, while Ciliata libera occurred inboth reservoirs also at a high content of this metal. Mercury is very toxic or lethalto most higher organisms. Ciliata libera are primitive organisms, hence theirsensitivity to Hg is lower and additionally – owing to their movement on reeds’surface – they can avoid places where substances against their overgrowth aresecreted.

76

The next two RDA axes explained respectively 16.84% and 8.74% of thevariance. RDA3 was connected to Cr and Pb content. The highest contributionof C/N ratio was observed in RDA4 (Figure 4, Tables 5, 6).

Analysis of biplot scores showed that Arachnidae occurred at high density onreed substrate rich in Pb and Cr (RDA3), which can be explained by movementof these taxa. Moreover, Nematoda and Harpacticoida preferred wide range ofC/N ratio (RDA4), that is low nitrogen content in the reed substrate. The oppo-site dependencies were observed for Chlorophyta. Nitrogen in reed tissues is anideal source of this nutrient, which is indispensable for green algae growth. Pres-ence of high C concentration does not directly stimulate growth of either Harpac-ticoida or Nematoda, since both taxa belong to herbivores, feeding mostly ondiatoms (PIESIK 1992).

Fig. 4. RDA bibplot – axis 3 and 4 – for ¯arnowieckie Lake and Puck Bay

CONCLUSIONS

1. Harpacticoida and Chlorophyta preferred reed substrate with relatively highZn, S and Cr concentrations but low Mn and C content;

2. Nematoda had the highest density on reed substrate rich in Mn;3. Hg in reed limited density of Arachnidae-Hydrachnella and Chironomidae

larvae, an effect which was not observed in the case of Ciliata libera;

77

4. Nematoda and Copepoda (Harpacticoida) preferred low Pb and Cr con-centrations and high C/N ratio, which meant low N content in the biotic sub-strate;

5. Nematoda were more abundant in freshwater ¯arnowickie Lake, mostlydue to relatively low Zn concentration in reed;

6. Copepoda (Harpacticoida) preferred saline water of Puck Bay, which wasassociated with higher content of Zn and S but lower C concentration in reedsubstrate;

7. Bacillariophyta were particularly abundant in the lake ecosystem but dueto factors other than chemical composition of reed substrate.

This study should be treated as a contribution to more thorough investigationson periphyton density-reed chemical composition. It would be advisable to confirmthe obtained results by experiments excluding interference factors, like feedingon periphyton or wave motion.

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