diversity of vascular hydrophytes in the zasavica river (serbia). changes after 13 years (2012)

7/26/2019 Diversity of Vascular Hydrophytes in the Zasavica River (Serbia). Changes After 13 Years (2012)

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Arch. Biol. Sci., Belgrade, 64 (4), 1607-1617, 2012 DOI:10.2298/ABS1204607V

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DIVERSITY OF VASCULAR HYDROPHYTES IN THE ZASAVICA RIVER SERBIA CHANGES AFTER THIRTEEN YEARS

DRAGANA VUKOV, RUICA IGI, M. RUANDO and SNEANA RADULOVI

Department o Biology and Ecology, Faculty o Sciences, 21000 Novi Sad, Serbia

Abstract - Zasavica is a 33.1 km-long, slow-flowing river on the southern edge o the Pannonian plain. It has been a pro-tected natural asset since 1997, and has great value as a natural aquatic habitat. In the period between 1998 and 2010, in-tensive studies o the aquatic vegetation were carried out. Te comparisons o results gained at the beginning o that periodwith those rom the end, show significant differences in species composition, spatial distribution, and diversity analyzed

through species richness, Shannons diversity index, and evenness.

Key words: Macrophytes, Shannons diversity index, evenness, species richness, temporal changes

INRODUCION

Vascular aquatic plants include different adaptivetypes that inhabit different water bodies. Teir basicstructural and physiological characteristics are in ac-cordance with the ecological conditions and resourc-es o the aquatic environment in which they developand live. According to their ecomorphology and po-sition in the water body, aquatic plants are dividedinto the ollowing groups: submerged plants, floatingplants and emergent plants, where the first two eco-morphological types are known under the term hy-drophytes (sensu stricto), while the emergent plantsare called helophytes. In contemporary literature,ecologists ofen use the term aquatic macrophytes,which has no precise taxonomic meaning. Essential-ly, it reers to larger aquatic plants, and distinguish-es them rom microscopic planktonic and benthicplants, and thereore includes aquatic mosses, liver-worts and larger algae as well as vascular plants. Tisstudy deals with the submerged and floating vascularhydrophytes that belong to the divisions o Polypo-diophyta and Magnoliophyta. Hydrophytes are an

important component o aquatic ecosystems and canbe used to acilitate the monitoring o the ecologi-

cal status. In addition to their important ecologicalrole, the use o hydrophytes as indicators o ecologi-cal quality in running waters is based on the act thatcertain species and species groups are indicators orspecific running water types and are adversely a-ected by anthropogenic impact. Sometimes the lacko hydrophytes is also characteristic or certain typeso habitats in running waters (Sculthorpe, 1967;Hutchinson, 1975; Cook, 1990; Janauer and Dokulil,2006).

Hydrophytes, or aquatic macrophytes, are be-coming a matter o particular concern rom the sci-entific and economic aspect in relation to the currentrequirement o the Water Framework Directive touse aquatic macrophytes as biological elements orthe assessment o the ecological status o water bod-ies (WFD, Directive 2000/60/EC).

Te Special Nature Reserve Zasavica lies in thearea o southern Vojvodina and northern Mava, in


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1608 DRAGANA VUKOV E AL.

the northwest o Serbia on the territory o municipali-ties Crna Bara, Banovo Polje, Ravnje, Radenkovi, Za-

savica, Sala Noajski, Noaj, and Mavanska Mitro-vica (4452'24"/4458'04" N, 1924'07"/1936'31"E,central point at 4456'12"N 1929'09"E, altitude be-tween 77.5 and 80.6 m above sea level). Te centero the Reserve has the 33.1 km-long river, Zasavica,that meanders between settlements and runs into theSava River near Mavanska Mitrovica. Due to theuntouched nature, rich and diverse wildlie, Zasavicabecame a protected natural asset in 1997 (Brankovi,1997).

Te first inormation on the aquatic vegetation o

Zasavica dates back to the beginning o 20th century(Jurii, 1911), but more detailed surveys were un-dertaken afer 1997 (Vukov et al., 2000; 2001; 2010;Igi et al., 2001; Peri and Stankovi, 2007; Stankovi,2007)

Te aim o this study was to detect changes in thecomposition o hydrophytic species, its abundanceand diversity that has come about in the thirteenyear-long period. Te act that the study site (the riv-er Zasavica) is a protected natural asset accentuates

the importance o this study, in order to determinatethe effect o its management on its natural eatures.

MAERIALS AND MEHODS

Field research was carried out in July 1998 and July2010. Te main channel o the river was divided intocontinuous survey units o different length, depend-ing on the characteristics o hydromorphologicaleatures, aquatic and semi-aquatic vegetation, andland use in the adjacent areas along the banks. Ineach survey unit, submerged and/or floating aquaticvascular plant species were recorded, and or eachrecorded species the Plant Mass Estimate (PME) wasassessed according to an ordinal, five-level descrip-tive scale: 1-rare, 2-occasional, 3-requent, 4-abun-dant, 5-very abundant (Kohler et al., 1971; 1978;1995; Pall & Janauer, 1995; Janauer, 2003; EuropeanStandard EN 14184, 2003, relating to WFD). Forurther analyses, the ordinal PME data were trans-ormed into plant quantities expressed by relative

values (abundance here onwards) using the unc-tion y=x3(where y=abundance, x=PME; Janauer and

Heindl, 1998). Te results obtained in 1998 (Vukov,2000) were used to group the surveyed units into wa-ter bodies according to similarities in species com-position, abundance and distribution. In this man-ner, 17 water bodies were defined (able 1).

Based on the abundance o the obtained data in1998 and 2010, the ollowing numerical derivateswere calculated or each water body (Janauer, 2003;www.midcc.at): relative plant mass (RPM%); meanmass indices (MM mean mass index calculatedor the total length o the river; MMO mean mass

index calculated or the lengths o survey units wherecertain species were recorded), dispersal or distribu-tion ratio (d the ratio between MM3and MMO3,ranging between 0 and 1). Te diversity o aquaticvascular plant species in each water body was ana-lyzed through species richness (S), Shannons diver-sity index (H), and Pielous evenness index (J). Teresults gained or defined water bodies in 1998 and2010 are presented graphically, and compared usingthe Students t test and F test (SAISICA 10).

Te nomenclature o the analyzed hydrophytesollows 2011 Species 2000 and IIS Annual Checklist(Bisby et al., 2011).

RESULS

In 1998, 29 species made up the submerged andfloating vegetation in Zasavica River. Tirteen yearslater, in 2010, that number decreased drastically, andwas 19 (able 2). Seven species recorded in 1998belonged to the category o strictly protected plantspecies (SP), while our belonged to the group oprotected plant species (P), according to the Decla-ration o strictly protected and protected wild plant,animal and ungi species (Slubeni glasnik RS, No.5/2010). In 2010, our o the strictly protected andtwo o the protected species were not recorded in themain channel o the Zasavica.

Te abundance and the distribution patterno Stratiotes aloides and Ceratophyllum demersum


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DIVERSIY OF HYDROPHYES IN ZASAVICA 1609

changed the most drastically in the period between1998 and 2010.

Stratiotes aloidesdominated in the aquatic veg-etation in 1998, with RPM 30.35% (Fig. 1), it wasalso the most abundant hydrophyte in the entiresurveyed length o the river (Fig. 2; MM=4.14) andin the length o the sections where it occurred (Fig.3; MMO=4.36). According to its distribution ratio,

it was nearly ubiquitous, present in 86% o the sur-veyed sections (Fig. 4, d=0.86).

In 2010, the participation o S. aloides in theaquatic vegetation o Zasavica significantly de-creased; its RPM value was almost ten times lower(RPM=3.19%). Its abundance, according to Kohlersfive-level scale, also decreased with regard to thewhole surveyed length and the sections o the river

Fig. 1.Te RPM (%) values or 1998 and 2010

Fig. 2.Te MM values or 1998 and 2010


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where it was recorded (MM=1.73; MMO=2.27), sothe occurrence o this once abundant species becameoccasional. Its distribution range in the Zasavica wasreduced to 44% o the surveyed length (d=0.44).

In 1998, Ceratophyllum demersum participatedin the aquatic vegetation o Zasavica River by 7.43%(Fig. 1). Its abundance was between occasional and

requent along the total length o the river (Fig. 2;MM=2.59), and in the sections where it was re-corded (Fig. 3; MMO=2.64), but its distribution washomogenous (Fig. 4; d=0.95).

Tirteen years later, C. demersum was the mostdominant hydrophyte in Zasavica, with an increasedRPM value o 23.57%. Its abundance became re-

Fig. 3.Te MMO values or 1998 and 2010

Fig. 4.Te d values or 1998 and 2010


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quent to abundant in the total surveyed river length(MM=3.36), and in the sections where it grows(MMO=3.56), although its distribution range wasslightly reduced (d=0.85).

Te RPM values o the majority o other speciesrecorded in the Zasavica in both 1998 and 2010 haveincreased. Exceptions are Lemna minor and Najas mi-

norwith a relatively unchanged share in the aquaticvegetation, and Utricularia vulgaris, Lemna trisulca,Potamogeton crispus, Potamogeton lucensand Najasmarinawith a decreased RPM.

In general, values o the Mean Mass Indicescalculated or the total length o the surveyed river(MM) tended to decrease, since the mean MM

Fig. 5.Species richness in water-bodies o Zasavica

Fig. 6.Shannons diversity index in water-bodies o Zasavica


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value in 1998 was 1.50, and in 2010, 1.08 (Fig. 8), al-though the recorded difference is not statistically sig-nificant (p=0.41; F-ratio Variances=1.28; pVar=0.67).

Although species such as Salvinia natans, Cer-

atophyllum demersum, Nuphar lutea, Spirodelapolyrrhiza, Nymphaea alba, Myriophyllum spicatum,Stuckenia pectinata and Wolffia arrhiza, have Koh-lers abundance values, regarding the total length othe Zasavica, higher in 2010 than in 1998 (Fig. 2),many o hydrophytes ound in the Zasavica in 1998were not recorded in 2010, so the mean MM isslightly lower in 2010.

Similar to the MM, the mean MMO was low-er in 2010 than in 1998 (Fig. 8). In 1998 it was 1.89and in 2010, 1.35. Te recorded difference is on theverge o statistical significance (p=0.05; F-ratio Vari-ances=2.16; pVar=0.046).

Te same assembly o species that showed in-creased MM values had higher MMO values in2010, with the addition o Utricularia vulgaris (Fig.3).Its lower MM in 2010 shows that it has retreatedrom the water bodies where it occurred in 1998,but its higher MMO in 2010 shows that in the parts

o Zasavica where it still grows, it is more abundantthan in 1998.

Te dispersal ratio (d) which indicates the distri-bution o species along the surveyed river has slightly

increased; in 1998 its mean value was 0.51, and in2010 it was 0.53 (Fig. 8). Tis change is not statis-tically significant (p=0.91; F-ratio Variances = 1.26;pVar=0.62). Most o the plant species have retreatedrom the localities they inhabited in 1998, which isshown by the lower values o their dispersal ratio(Fig. 4). On the other hand, species like Wolffia ar-rhiza, Potamogeton lucens and Callitriche palustriswere ound in water bodies in 2010 where they havenot been recorded in 1998, so their distribution inthe Zasavica has become wider, and this is shown inthe increase o their distribution ratio values.

Te values o species richness in the defined wa-ter bodies along the Zasavica River tend to be lowerin 2010, than in 1998. Te exception is the 650 m-long water body 2 (Jovaa 2; able 1), with five speciesrecorded in 1998, and eight in 2010. In water body 3(Prekopac), 12 species were recorded in 1998, whilein 2010 the water body was completely overgrownwith reeds and without any submerged or floating

Fig. 7. Pielous evenness index in water-bodies o Zasavica


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plants. Water body 16 (Lug) had the highest numbero hydrophytes in 1998 23, while in 2010 the speciesrichness declined and was 9 (Fig. 5). Tis water bodyis also the one with the largest decline in the numbero recorded species in thirteen year-long period. Tetrend o increasing species richness in the down-stream direction rom water body 1 to 17 that couldbe observed in 1998, in 2010 is no longer visible.

Water body 16 (Lug) had the highest value othe diversity index in 1998, 2.58 (Fig. 6), and wa-ter bodies 2 and 7 had the lowest 1.1. In 2010, thehighest diversity index was recorded in section 15(2.11), and the lowest was in water body 5 (1.52). Te1010 m-long water body 5 (rebljevine 1) is charac-terized by the biggest decline in diversity index value,since in 1998 it was 2.25, and in 2010, as previously

Fig. 8. Comparison o the MM, MMO, d, S, H, and J mean values


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mentioned, 1.52. Te localities with increased val-ues o Shannons diversity index are 2, 6, 7, 8, and 9;the water bodies with decreased diversity are: 5, 10,11, 12, 13, 14, 15, 16, and 17; sections with nearlyunchanged diversity index are 1 and 4. It is interest-

ing to observe that the increase in the diversity in-dex happened in the water bodies characterized byrelatively low values in 1998 (1.6 and lower), whilethe decline in diversity is noticed in the sections withrelatively high values recorded in 1998 (between 2.11and 2.58), so the plant species diversity became moreuniorm in 2010.

Te species evenness values were higher in 2010than in 1998 in all surveyed water bodies, except 5,10, 13, 14, and 15, where in the last two the decreasewas minimal (Fig. 7). In 1998, the highest evennessvalue was recorded in section 13 (Valjevac 1) 0.89,and the lowest in water body 7 (Poljansko 1) 0.46.Tirteen years later, the highest value was calculatedor water body 4 (rebljevine), where the maximalspecies evenness occurred, while the lowest valuewas 0.73, recorded in section 10 (Vrbovac).

Te average number o species, or species rich-ness, recorded in each surveyed water body has de-

clined. In 1998, the mean value was 14.06, while in2010 it was 9.37 (Fig. 8). Te observed difference is

statistically significant (p=0.0004; F-ratio Varianc-es=3.97; pVar=0.01). In addition, the recorded speciesnumber in the water bodies o the Zasavica was morevariable in 1998 than in 2010.

In 1998, the average Shannons Diversity indexwas 1.94, while in 2010 it was 1.85 (Fig. 8). Tis differ-ence is not statistically significant, according to the t-test (p=0.25; F-ratio Variances=9.42; pVar=0.00008).More significant is the difference in the deviation othe recorded values rom the mean, which was muchwider in 1998.

Te average value o species evenness was 0.74in 1998 and 0.84 in 2010 (Fig. 8). Te increase in thevalue is statistically significant (p=0.009; F-ratio Var-iances=4.60; pVar=0.005). Deviation rom the meanvalue was wider in 1998, while the values o speciesevenness were much narrowly grouped around themean in 2010.

DISCUSSION

Te temporal changes in aquatic vegetation as indi-cators o habitat changes have been studied by nu-merous authors, concluding that the indicative po-tential o aquatic plants rests on the knowledge othe species tolerance within an ecoregional context(Hutchinson, 1975; Lacoul & Freedman, 2006).

he most notable change in the assemblage osubmerged and loating aquatic plant species inthe Zasavica River over the course o thirteen yearswas in the composition o species. At the end othis period, in 2010, no new species were ound inthe main channel, and eleven species that had in-habited main channel o the river in 1998, were notrecorded in 2010. So the overall species richness inthe Zasavica decreased. he lower number o hy-drophyte species was not expected, since the stud-ied area is protected by law, and is a slow-lowinglowland river, highly susceptible to natural succes-sion (opuzovi et al., 2009; Oaheov et al., 2007;Hrivnk et al., 2009). Among the missing plants

Table 1.: Te list o defined water bodies in Zasavica River

name o water-body abbreviation length [m]

Jovaa 1 920Jovaa1 2 650

Prekopac 3 750rebljevine 4 1030

rebljevine1 5 1010Poljansko 6 2030

Poljansko1 7 1900Batve 8 2500

Batve1 9 2560Vrbovac 10 2100

Vrbovac1 11 2000Valjevac 12 2000

Valjevac1 13 2000Valjevac2 14 2250

Sadak 15 2070Lug 16 2070

Modran 17 2650

total 30490


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are our strictly protected, and two protected spe-cies. Since the study site was the central part othe Special Reserve, protected because o its natu-ralness and numerous rare and protected species,this possible loss o protected aquatic plant speciescould be an indicator o the inadequate manage-ment o this protected natural asset. In this study,only the results o surveys done in 1998 and 2010were analyzed. In the period between there wererecords o aquatic plant species that are notable.he most signiicant is the inding o Aldrovandavesiculosa in 2006 (Stankovi, 2007), but in the

survey in 2010 it was not ound, as along with Elo-dea canadensis(Peri and Stankovi, 2007).

Te next indicative change in the hydrophyticvegetation o the Zasavica concerns the change inthe order o dominance. In 1998, the most dominantaquatic vascular plant in the Zasavica was Stratiotesaloides, making up over a third o the relative plantmass, with a ubiquitous distribution along the riverand being the most abundant in the assembly o hy-drophytes. In 2010, its relative plant mass was overten times lower, it became occasional instead o abun-

Table 2.Species List

Species Abbreviation 1998 2010 National legislative

Callitriche palustris L. Cal pal + + SPCeratophyllum demersum L. Cer dem

+ +

Ceratophyllum submersum L. Cer sub+

Hottonia palustris L. Hot pal+ SP

Hydrocharis morsus-ranae L. Hyd mor+ +

Lemna gibba L. Lem gib+

Lemna minor L. Lem min+ +

Lemna trisulca L. Lem tri+ +

Myriophyllum spicatum L. Myr spi+ +

Myriophyllum verticillatum L. Myr ver+

Najas marina L. Naj mar+ +

Najas minor All. Naj min+ +

Nuphar lutea(L.) Sibth. & Sm. Nup lut + + SP

Nymphaea alba L. Nym alb+ + SP

Nymphoides peltata (S. G. Gmelin) O. Kuntze Nyp pel+

Potamogeton acutiolius Link. Pot acu+ SP

Potamogeton crispus L. Pot cri+ +

Potamogeton lucens L. Pot luc+ +

Potamogeton pusillus L. Pot pus+ SP

Potamogeton trichoides Cham. et Schlecht. Pot tri+ SP

Ranunculus circinatus Sibth. Ran cir+

Salvinia natans(L.) All. Sav nat + +Spirodela polyrrhiza (L.) Schleiden Spi pol + +

Stratiotes aloides L. Str alo + +

P

Stuckenia pectinata (L.) Berner Stu pec+ +

Utricularia australis R. Br. Utr aus +P

Utricularia vulgaris L. 1753 Utr vul + +P

Wolffia arrhiza (L.) Wimm. Wol arr + +Zannichellia palustris L. Zan pal + P

otal number o species 29 18


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dant, and it retreated rom almost hal o the locali-ties it had inhabited beore. In 2010, a new dominant

species emerged, Ceratophyllum demersum, whichis now abundant and present in almost all the sur-veyed water bodies. Te act that afer thirteen yearsthe most dominant species in a slow-flowing lowlandriver has become a submerged species instead o thefloating one, is a bit unusual in regard to the stages osuccession in reshwater ecosystems (Krivtsov et al.,2000). It is to be expected that afer a certain periodo time, the flotant vegetation would become moredeveloped. Te only part o the Zasavica where proc-esses o natural succession took the expected coursewas Prekopac, which is now in the phase o emer-

gent, or helophyte, vegetation. It seems that in therest o the Zasavica River, the succession took a stepbackwards, allowing the successul development osubmerged plant assemblages.

Te observed diversity loss is substantiated bythe lower species richness and diversity index values,both as a general trend and in the individual waterbodies. Te most drastic change in species richnessoccurred in the water body Lug. Te most significantdrop o diversity index value was observed in above-

mentioned water-body, and in rebljevine 1. In ad-dition, regarding the changes in diversity index, it isworth mentioning that the values o this parameterbecame more uniorm in the surveyed parts o theZasavica, and that its values dropped most signifi-cantly in water bodies that were earlier characterizedby high diversity. Unlike species richness and diversi-ty index, the values o the evenness index were high-er in 2010, both in general and in the separate waterbodies. Although the number o recorded speciesand their diversity have decreased, the abundance ohydrophytes that are growing in the Zasavica havebecome more evenly distributed between occurringaquatic plant species, and the recorded values o spe-cies evenness became less variable along the river(Magurran, 2004).

Te increased evenness indicates an evenly dis-tributed abundance among the hydrophytes thatwere recorded at the end o the thirteen year-longperiod, and this again illustrates the established sta-

bility that happened afer the disturbance that causedthe diversity loss. It is important to reveal the origin

o the disturbance that caused such drastic changes.Te possible explanation probably lies in hydrologi-cal actors that have changed over the years (Janaueret al., 2010; Hrivnk et al., 2006; 2010; Oaheov,2011). Tere are some indications that the water levelo the Zasavica has become significantly higher, asalong with the flow rate. Unortunately, since there isno available published documentation that such hy-drological measures were undertaken, this explana-tion is just speculation, based on the changes in theaquatic vegetation.

Acknowledgments - Tis work is supported by the Ministryo Education and Science o the Republic o Serbia, projectIII43002.

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diversity of vascular hydrophytes in the zasavica river (serbia). changes after 13 years (2012)

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