AQUATIC MACROPHYTES AND THEIR USE AS ECOLOGICAL...

Romanian Journal of Aquatic Ecology 1.1 (2011)

45

AQUATIC MACROPHYTES AND THEIR USE AS ECOLOGICAL

STATUS INDICATORS IN RESTORATION PROJECTS

IN THE DANUBE DELTA (ROMANIA)Erika SCHNEIDER-BINDER 1

Keywords: Romania, Danube Delta, aquatic macrophytes, quality indicators,

filtering function, restoration, monitoring as success control.

Abstract

The present study provides an introduction to the aquatic plants and their

communities occurring in three restored areas of the Danube Delta - Babina, Cernovca

and Popina. Given that the aquatic vegetation is very sensitive to physical and chemical

parameter changes it perfectly suits as indicator in the evaluation of alterations owing to

restoration measures. These evaluations consist in changes regarding the hydrological

regime, water circulation, water exchange, sedimentation processes, nutrient content

and filter function. The presence of aquatic plants of the Hydrocharition alliance such

as Greater bladderwort (Utricularia vulgaris), Frogbit (Hydrocharis morsus ranae)

or Waster soldier (Stratiotes aloides) in those spots along the reed area borders where

clear, filtered water seeps in substantiates the re-established filter function in the restored

areas.

ZUSAMMENFASSUNG: Gewässermakrophyten und ihre Verwendung als

Indikatoren des ökologischen Zustandes in Renaturierungsprojekten im Donau-Delta

(Rumänien).

In vorliegender Arbeit werden die Wasserpflanzen und ihre Gesellschaften aus

drei renaturierten Gebieten Babina, Cernovca und Popina im Donau-Delta vorgestellt. Da

die Wasserpflanzen auf Änderungen der physikalischen und chemischen Parameter sehr

sensibel reagieren, können sie zur Bewertung von Veränderungen nach erfolgten

Renaturier-ungsmaßnahmen dienen. Dabei geht es um die Bewertung von Veränderungen

des hydrologischen Regimes, von Wasser-zirkulation, Wasseraustausch, Sedimenta-

tionsprozessen, Nährstoffgehalt und Filterfunktion. Wasserpflanzen des Verbandes

Hydrocharition wie beispielsweise Wasserschlauch (Utricularia vulgaris), Froschbiss

(Hydrocharis morsus ranae) oder Krebsschere (Stratiotes aloides), die am Rande von

Schilfflächen dort vorkommen, wo klares, gefiltertes Wasser heraustritt, belegen die

Wiederherstellung der Filterfunktion in den renaturierten Gebieten.

Rom. J. Aquat. Ecol. 1.1 (2011); E. Schneider - Aquatic macrophytes and restoration, pp. 45-62

46

Rezumat: Macrofite acvatice şi folosirea lor ca indicatori ai stării ecologice în

proiecte de restaurare în Delta Dunării (România).

Lucrarea prezintă macrofitele acvatice şi comunităţile lor din trei arii situate în

nord-estul Deltei Dunării: Babina, Cernovca şi Popina, în care au fost implementate

măsuri de reconstrucţie ecologică. Deoarece macrofitele acvatice reacţionează foarte

sensibil la schimbarea parametrilor fizici şi chimici, pot fi utilizate pentru evaluarea

schimbărilor în urma măsurilor de reconstrucţie ecologică aplicate. Evaluarea se referă la

schimbări în regimul hidrologic, circulaţia apei, procese de sedimentare, conţinutul de

nutrienţi şi refacerea funcţiei de filtru a stufului. Macrofite acvatice din alianţa

Hydrocharition ca de exemplu otrăţelul de baltă (Utricularia vulgaris), broscariţă

(Hydrocharis morsus-ranae) şi foarfeca de apă (Stratiotes aloides), care s-au reinstalat în

bordura stufului acolo unde apa iese limpede şi filtrată, dovedesc refacerea funcţiei de

filtru în zonele renaturate.

Introduction

The Danube Delta presents a diversified network of water bodies including water

courses and standing waters of varying sizes. The water courses consist in the main

branches of the Danube river, large secondary natural branches, large channels that flow

into secondary branches, small and narrow channels connecting the lakes, smaller

streams, the so called “gârla” and “japse”, temporary water courses, flood channels or

channels characterized by anthropogenic impacts such as dragging and artificial canals

that were cut through the reeds. A large variety of standing waters of various sizes and

depths exists between the branches of the delta in the large reed areas. They consist in

reed-surrounded, isolate lakes, connected to smaller or larger water courses, temporary

small standing waters and artificial standing waters such as fishponds.

The hydrological regime, hydro-morphological processes and trophic conditions

of these waters constitute the basis for a large diversity of aquatic macro- and

microhabitats, which in their turn form the basis for the settling of various aquatic

macrophytes and their communities. The habitats are differentiated by their spatial

structure and the species composition of the macrophyte communities, offering niches to

many macroinvertebrate and fish species. Ecological gradients do exist between the

various types of water bodies and also within individual water bodies where the

repartition of macrophytes follows ecological gradients in dependence of their width,


47

depth, flow velocity and turbidity. The latter is in relation with the connection to the

Danube branch categories (direct connection, secondary and third connection category).

Given that the aquatic vegetation is very sensitive to natural changes, the

fluctuations of environmental factors and changes owing to anthropogenic impacts such

as rectifications, the construction of new canals, dykes and further hydraulic measures, it

is well suited as status indicator for changes in water quality and physical parameters in

consequence of restoration works.

In recent times water macrophytes have been increasingly used for the evaluation

of the trophic condition (Oosterberg & Staraş, 2000; Penning et al., 2008; Coops &

Hanganu, 2000) and the determination of physical parameters (Schneider, 2009). The

present study discusses the use of water macrophytes for the purpose of an ecological

status evaluation of water bodies in three project areas of the Danube Delta prior to and

after restoration. The macrophytes act as success control element for the monitoring of

changes occurring in the ecological condition after the measures were implemented (water

flow, filtering capacity, sediments).

Among the project areas, Babina and Cernovca were abandoned agricultural

polders characterized by destroyed, arid reed areas with increasing salinity. The third

area, Popina, consisted in an abandoned fishpond, a disturbed wetland that had been cut

off from the water dynamics of the Danube River and was subject in some parts to silting

and increasing salinity (Lagendijk & Schneider, 2000). Before hydrotechnical measures

were taken the area was a characteristic wetland area with standing and running waters.

The construction of dams transformed all former small water courses into standing

waters.

Among these three areas Babina was the first to be reconnected to the water

dynamics of the Danube River in 1994 and was followed in 1996 by Cernovca (Marin &

Schneider, 1997; Staraş, 2000; Schneider et al., 2008). The third area, Popina, was opened

subsequent to preliminary studies and technical plannings in the year 2000 (Schneider et

al., 2004) and has been monitored in 2000 at its opening as well as in 2001. Given that

wetland areas and aquatic vegetation could be found on Popina island, even though not

homogeneously and of varying quality, running waters being not existent, the objective

was to find out to which extent water circulation and water exchange had been re-

established by the reconnection to the Danube and how aquatic macrophytes had adapted

to these changes.


48

Materials and Methods

Due to multiannual samplings taken in a determined network of sampling sites in

the restoration areas Babina, Cernovca and Popina in the North-eastern Danube Delta/

Chilia branch the following elements became provable within the frame of the monitoring

programme: recolonisation of species depending on the hydrological regime, abundance-

dominance value fluctuations of individual species on various sites of the restored areas

over several years and changes in the abundance-dominance values of plant communities

(Schneider et al., 2008).

The samples were taken within the frame of field studies and along with studies

conducted on macrozoobenthos, phyto- and zooplankton. The samples and the physical-

chemical measurements were taken in 23.-24. VII 1996, 29.-30 VI 1997, 1.-4 VI 1998,

18.-22 VI 1999, 23.-24 VI 2000 and 20 VI 2001 for the island polders Babina and

Cernovca, with a number of verifications in 2005, and in 1999, 2000 and 2001 for

Popina.

The sampling sites were determined to include all types of water bodies

(Lagendijk & Schneider, 2000; Schneider et al., 2004, Schneider et al., 2008).

The permanent waters are composed of a network of artificial canals, natural

former branches, smaller water courses, the so-called „Gârla“ and the shallow

depressions of varying extent that are connected to them, some kind of shallow

lakes. Considering their connectivity the waters had to be evaluated differently.

Besides selective samplings, data have also been collected in the circumference of

the sampling spots to allow a large-scale vegetation recording. Moreover, data on

the vegetation occurring alongside a number of water transects have been collected

all the same to allow a more concise registration along ecological gradients. The

collection of the aquatic vegetation data has been effected by means of the methods

for the evaluation of species abundance, dominance and sociability according to

Braun-Blanquet (1964). The yearly controls of the sampling spots allowed to draw

comparisons and made it also possible to show the development trends of the

vegetation under the changed physical and chemical parameters subsequent to

restoration measures. The improvement of water circulation, water exchange and

flashing was monitored one year following the opening on the basis of the abundance

of existing salinity indicators as well as by the recording of further indicator species

for running waters.


49

Results and Discussions

The Babina and Cernovca area

After the reflooding of the two agricultural polders Babina and Cernovca, site-

specific species and plant communities developed rapidly in strong relation with the

restoration of the hydrological regime and the water quality. Along with the flooding a

shifting from dry towards a humid, moist and constantly water-covered area took place.

Depending on the ground level, the recorded data differed as a result of duration, height,

period and frequency of the floods respectively of the depth of the water bodies.

Characteristic species for running waters have been observed at the opening spots

just as species characteristic of running waters with a high to low turbidity, they are

represented by the pondweeds Potamogeton pectinatus, Potamogeton nodosus and

locally also by Potamogeton crispus. Species characteristic of running and more or less

clear waters such as the submerged form of Sagittaria sagittifolia and Sparganium

emersum. Potamogeton pectinatus occur in the oulet areas, even though they have a large

ecological amplitude and are present in clear to extremely turbid running and standing

waters. In some canals of the opened polder’s centre the pondweeds Potamogeton

crispus and Potamogeton pectinatus have been observed as well, the first being the only

water macrophyte species which persisted in the some canals of the polder before

opening.

Table 1. Evolution of water macrophyte diversity in the restored polder Babina;p = present, d = dominant.

SpeciesYear

1994 1995 1996 1997 1998 1999 2000 2001 2005Aldrovandavesiculosa . . . . . p . . .

Alismalanceolatum . p . p . . . . .

Alismaplantago-aquatica . p p p . . p p p

Azollafiliculoides . d d d p d . . p

Ceratophyllumdemersum . d d d d d d p p

Characontraria . . . . d . . . .

Charaglobularis . . . p d d . p .


50

Table 1 continuing.Charavulgaris . . . . p . . p .

Elodeacanadensis . . . . . d p p p

Elodeanutalii . . . . d d p p p

Hydrocharismorsus-ranae . d d p p d d d d

Lemnaminor p p p p d p p p p

Lemnatrisulca . p p p p d p p p

Myriophyllumspicatum . p d d d d p p p

Najas marina . . . d . . . . pNupharluteum . . . . . . . . .

Nymphaeaalba . d d p d d d d d

Nymphoidespeltata . d d . p d . . p

Polygonumamphibium p p d p p p p p p

Potamogetonberchtoldii . . . . p . . . .

Potamogetoncrispus p p p d d d p p p

Potamogetonlucens . p p d d d d d d

Potamogetonnodosus . p p p d p p p p

Potamogetonpectinatus . p p . p d p p p

Potamogetonperfoliatus . . . p . . . . p

Potamogetontrichoides . . . p d d d p p

Ranunculuscircinatus . . p . d p p p p

Ranunculustrichophyllus . . d . . . p p .

Sagittariasagittifolia . p p d . . p d d


51

Table 1 continuing.Salvinianatans d d d d d d d d d

Sparganiumemersum . . . d p p p p d

Spirodelapolyrhiza . d d p p p p p d

Stratiotesaloides . p d d d d d d d

Trapanatans . p p d d d d d d

Utriculariavulgaris . . . p d d d d p

Veronicaanagallis-aquatica . p p . p p d p .

Wolffiaarrhiza . p . . p p . . .

Zannichelliapalustris L.ssp. pedicellata

. p p p p d p d p

Numberofspecies

4 23 23 25 29 28 26 28 28

The development of water macrophytes and their communities in the

opened Babina polder became clearly apparent already in 1995 with broad covers of

fringed water-lily (Nymphoides peltata) in the northern area with shallow waters and

a high sediment load, the species being an indicator in shallow, eutrophic waters

with siltation processes and medium turbidity. In the first year after opening, covers

of floating macrophytes such as swimming fern (Salvinia natans), giant duckweed

(Spirodela polyrhiza) and common waterlens (Lemna minor) have also developed

and are characteristic of moderate eutrophic to eutrophic waters with medium

turbidity. Small areas were covered with European white water lily (Nymphaea

alba), characteristic of clear, moderate eutrophic to eutrophic waters. The rapid

re-establishment of the species can only be explained by the existence of the

rootstocks which survived on the bottom of the drained polder area for a period of

about twelve years, from the construction of the dams and the drainage measures

up to the reconnection of the area to the water dynamics of the Danube River (Table

1).


52

A similar situation has been observed in the Cernovca polder openend two years

later in 1996. In this area the White water lily (Nymphaea alba) developed also in

proximity of floating species such as Salvinia natans, Giant duckweed (Spirodela

polyrhiza) and Common waterlens (Lemna minor). The latter arrived in the area with the

inflowing water and was among the first settlers after the reflooding (Table 2).

The gradual recovery of the reed area’s filter function has been observed from the

second year following the opening. First signs of a beginning filtering capacity of the

reed could be documented by the presence of small stands of Frogbit (Hydrocharis

morsus ranae) along the borders of small rushes consisting of the Bulrush Typha

angustifolia, Water-archer (Sagittaria sagittifolia) and Sparganium ramosum. The

Greater bladderwort (Utricularia vulgaris) settled in Babina along the borders of the

main canal CC2 from 1997, in those places where clear and filtered water seeped in from

the reed stands. These species occurring only in clear meso-eutrophic and eutrophic

waters are perfect indicators for the recovery of the reed’s filtering function in the

restored area and mark a distinct belt along the reed border, as does Frogbit (Hydrocharis

morsus ranae).

In the subsequent year 1998 the Greater Bladderwort already showed higher

abundance and dominance values (Table 2). In some lateral channels where the Water

soldier (Stratiotes aloides) builds broad covers, the Greater bladderwort occurred very

frequently as well. The sporadic occurrence of Aldrovanda vesiculosa together with

Greater Bladderwort Utricularia vulgaris in clear waters along the borders of a reed

stand is remarkable and shows as well the recovered filter function of the reed areas.

A similar evolution has been observed in Cernovca polder in 1997 and 1998, i. e.

the second and the third year following the opening and re-flooding. The Frogbit

(Hydrocharis morsus ranae) covered larger areas already in 1997. The recovery of the

filter function has been proven by the occurrence as well as abundance and dominance of

the Greater baldderwort (Utricularia vulgaris) and the development of large stands of

Water soldier (Stratiotes aloides). Greater baldderwort, Water soldier and Frogbit occur

together with the submerged floating Lemna trisulca in clear, moderate eutrophic waters,

they are very characteristic indicators of a good water quality.


53

Table 2. Evolution of water macrophyte diversity in the restored areas ofCernovca Island; p = present, d = dominant.

SpeciesYears

1996 1997 1998 1999 2000Azolla filiculoides . d . p pCeratophyllum demersum . d d d dChara hispida . . d . pElodea canadensis . . . p dElodea nutalii . p . . dHydrocharis morsus-ranae . d d d dLemna gibba . . . . pLemna minor p p p p pLemna trisulca . p d p dMyriophyllum spicatum - d p d dMyriophyllum verticillatum . . . p pNajas minor . p . . .Nuphar luteum . p p p pNymphaea alba . d d d pPolygonum amphibium p p p p .Potamogeton crispus p p p p pPotamogeton lucens . d p d dPotamogeton pectinatus . d d d pPotamogeton trichoides . p d d dRanunculus aquatilis . . p . .Ranunculus circinatus . . p p .Salvinia natans . d p p dSpirodela polyrhiza . . d p pStratiotes aloides . d d d dTrapa natans . p p p dUtricularia vulgaris . p d d dVallisneria spiralis . . p . .Zannichelia palustris . . p p d

Number of species 3 19 22 22 23

The distribution of water macrophyte associations in both artificial main and

lateral canals and in the lakes of Babina and Cernovca occurred as a function of pH-

values - the differentiation depending on water salinity, nutrient content of the water,

suspended load and involved water transparency, flow velocity, water depth and

involved water respectively channel bed warming and subsoil (sandy, silty).


54

The following water macrophyte associations have been recorded in the Babina

and Cernovca restoration area:

Lemnion minoris R. Tx 55 / Duckweed communities

- Lemno-Spirodeletum polyrhizae (Kalkofer 15) W. Koch 54 em. Müll. et Görs 60

- Lemnetum minoris (Oberd. 57) Müller et Görs 60

Hydrocharition Rübel 33 / Frogbit communities

The group of frogbit-associations is bound to clear, moderately nutrient-rich water

sections.

- Spirodelo-Salvinietum natantis Slavnic 1956

- Lemno-Azolletum filiculoidis Br.-Bl. 1915

- Lemno-Utricularietum vulgaris Soó (1928) 1938

- Hydrocharitetum morsus-ranae van Langendonck 1935

- Stratiotetum aloidis Nowinski 1930 em. Midjian 1933

facies with Utricularia vulgaris

Salvinia natans occurs predominantly and in some years (2005) it shapes the

autumnal aspect of the canals and other waters that are covered for their major parts by

this species. Azolla filiculoides occurs unsteadily. Given its tolerance against a moderate

salinity in waters and soils it has been recorded mainly in the western part of Babina and

Cernovca islands, where soil salinization has indeed been reduced as a result of the

reconnection to the Danube river, it is, however, still existent. In some places the species

forms also large carpets in the restoration area of Popina fishpond (2000, 2001).

Stonewort (Chara) – Associations

- Chara globularis community

Chara globularis has been registered in the western part of Babina at the end of canal

CC2 as a species developing dominant stands. In some parts they were closely interlaced

with stands of Ranunculus circinatus in waters with light salinity. In shallow waters they

could also be found in loose stands of sea club-rush (Bolboscheonus maritimus). Their

characteristic sites have changed following the opening and re-flooding of the polder as a

result of intensified cattle and pig grazing (and related to this an increasing

eutrophication) and the species disappeared as from 1998 even though it occurred en

masse before.


55

Potamion eurosibiricum Koch 26 p. p. / Submerged pondweed - communities

- Potamogetonetum perfoliati W. Koch 1926 em. Pass. 1964.

- Parvopotameto-Zannichellietum palustris (Baumann 1921) W. Koch 1926, facies

with Ranunculus circinatus

- Potamogetonetum lucentis Hueck 1931

- Potamogetonetum pectinati Horvatic 1931

- Potamogetono - Najadetum marinae (Oberd. 1957) Fukarek 1961

- Ceratophylletum demersi (Soó 1927) Hild 1956

- Najadetum marinae Fukarek 1961

- Elodeetum nutalii Ciocârlan et al., 1997

- Potamogetonetum trichoidis Freitag et al., 1956

- Potamogetonetum crispi Soó 1927

Nymphaeion Oberd. 1957 (Potamion eurosibiricum W. Koch 1926 p. p. /

Group of water lily communities

- Nymphoidetum peltatae (All. 22) Bellot 1951

- Trapetum natantis Müll. et Görs 1960

- Myriophyllo-Nupharetum luteae W. Koch 1926

- Nymphaeetum albae Vollmar 1947

- Myriophyllum spicatum-community

The Popina fishpond area.

Due to the relatively young alluvial land and the topography of the area with

respect to the mean water level of the Danube River, the Popina areas EC 21 and EC 22

are dominated by a characteristic vegetation which is called „balta“. It is characterised by

a mixture of reed vegetation and open water bodies with varying depths and extensions.

Large areas are covered by emerged and submerged macrophytes and small parts of

higher river embankments and dunes with semiaquatic and terrestrial vegetation.

Depending on the Danube River’s water level, the depressions of the western

part of Popina EC 22 that are dominated by Bolboschoenus maritimus and Juncus

maritimus also act as temporary waters, when the Danube water level exceeds the mean

level. During flood periods these temporary waters are colonised by water macrophytes

such as Utricularia vulgaris and Charophytes, as was the case in 2000 and also in 2001.


56

Even though large areas are characterized by more or less uniform reeds, the

area’s vegetation shows a high diversity of different types of species and plant

communities. This is due to the various ecological conditions depending on microrelief,

soil and hydrological regime (surface and groundwater dynamics), that have

unfortunately been subject to changes owing to hydrotechnical constructions in the area.

Small differences in the relief level lead to visible changes in the repartition of the

vegetation. In the area of Popina Polder EC 21 and 22 the following plant communities

have been identified:

Lemnion minoris R. Tx 55 / Duckweed communities

- Lemno-Spirodeletum polyrhizae (Kalkofer 15) W. Koch 54 em. Müll. et Görs 60

- Lemnetum minoris (Oberd. 57) Müller et Görs 60

Hydrocharition Rübel 33 / Frogbit communities

- Spirodelo-Salvinietum natantis Slavnic 1956

- Hydrocharitetum morsus-ranae van Langendonck 1935

- Stratiotetum aloidis Nowinski 1930 em. Midjian 1933

- Lemno-Utricularietum vulgaris Soó (1928) 1938 facies with Aldrovanda vesiculosa

- Lemno-Azolletum filiculoidis Br.-Bl. 1915

Stonewort (Chara) – Associations

- Charetum asperae Corillion 1957

- Charetum contrariae Corillion 1957

Potamion eurosibiricum Koch 26 p. p. / Submerged pondweed – communities- Potamogetonetum trichoidis Freitag et al., 1956

- Potamogetonetum lucentis Hueck 1931

- Potamogetonetum pectinati Horvatic 1931

- Parvopotameto-Zannichellietum palustris (Baumann 1921) W. Koch 1926

facies with Ranunculus circinatus

- Potamogetonetum nodosi (Soó 1960) Segal 1964

- Potamogetonetum crispi Soó 1927

- Ceratophylletum demersi (Soó 1927) Hild 1956 facies with Ranunculus circinatus

- Elodeetum canadensis Eggler 1973

- Hippuris vulgaris community


57

Nymphaeion Oberd. 1957 (Potamion eurosibiricum W. Koch 1926 p. p. / Group of

water lily communities

- Nymphoidetum peltatae (All. 22) Bellot 1951 facies with Hippuris vulgaris

- Myriophyllum spicatum-community

- Nymphaeetum albae Vollmar 1947

- Myriophyllo-Nupharetum W. Koch 1926

- Ranunculetum circinati community

The most diversified vegetation may be found in the south-western part of the

Popina EC 22 area. The ecological gradients from dry to wet, fresh to salty on different

soil types exemplified by cross sections are demonstrating very impressively the mosaic

patterns and a high diversity of species in relatively small areas.

Aquatic macrophytes are represented by more or less eutrophic plant

communities characteristic of different types of water bodies, standing or running

waters, clear or turbid, fresh or lightly saline, with various depth and extension,

bordered or mixed with patches of reeds. Due to these facts the aquatic vegetation

includes a wide range of different types of water macrophyte communities, locally

in small-scale mosaic patterns. Utricularia vulgaris occurs in clear and

mesotrophic-eutrophic waters. Further occurring, vulnerable species are the water

macrophytes Hippuris vulgaris, Stratiotes aloides and Trapa natans. Among the

endangered species and rare in the whole delta is Aldrovanda vesiculosa which occurs

in EC 22.

The reed vegetation is represented more frequently in the southern polder

EC 22 and more rarely in EC 21 owing to the destruction of the reed beds in EC 21 at

the moment of the fishpond construction. In polder EC 22 the reed’s function

as biological filter shows through the abundant occurrence of species that are

characteristic of clear, deep waters on organic soils. The same is true for EC

21. Utricularia vulgaris, Myriophyllum verticillatum, Lemna trisulca, Hydrocharis

morsus ranae and Hippuris vulgaris. Charophytes (Chara contraria, Chara

aspera) settle in clear shallow water areas and occur in the southern part of the both

polders.


58

In general the water macrophytes are represented mainly by communities

characterstic of eutrophic spots or slowly running waters. The large areas covered

by Nymphoides peltata in EC 21 and 22 indicate eutrophic waters with changing

water levels, the species being well adapted to these changes can also survive in

the summer time (i. e. the Danube River’s low water levels) and persist in semiterrestrial

conditions. The big quantity of biomass in the large open shallow waters and the

lacking water circulation will lead to increasing organic deposits and to a progressive

silting of area.

The courses of small old water channels („gârla“) are partly well contoured by the

presence and abundance of Stratiotes aloides. They constitute a first step towards a

development of swimming reeds, the so called „plaur“.

Generally higher pH values in the northern polder EC 21 compared to the

southern polder EC 22 becomes apparent by the dominance and high abundance of

Myriophyllum spicatum covering large areas, i. e. a species occurring in waters with high

pH values (s. Ellenberg et al., 1991). Highly abundant in EC 21 is also Ranunculus

circinatus, characteristic just as Myriophyllum spicatum in calcareous and extremely

basic waters (s. Krausch, 1996).

Potamogeton pectinatus occurs with a broader ecological amplitude. The species

is sporadically present in standing clear waters with high pH values and a high nutrient

content even though rather in running waters, as is the case in the surrounding canal of

Popina and Cardon, where turbidity is high owing to its sediment content. This species

occurs only along the borders of Popina polder in the Chilia branch.

Dyked areas without any direct connection to the channels or to the Danube

River branches show a higher salinity. This is apparent in the area situated between

the dyke adjacent to Popina channel and the former protecting dyke of the

village Sfistofca. This area with its changed hydrological regime, in connection

with a high evaporation rate owing to the studied area’s continental climate type,

is characterized by settlements of communities with increasingly characteristic

halophilous, polyhalin and also eurihalin species. On the water-side, next to the

Popina channel the community of Carex distans (lightly halophilous conditions

present) dominates on sites where salinity is well-balanced thanks to fresh water

floodings.


59

Potamogeton pectinatus occurring on larger areas around the openings after

the reconnection to the water dynamics of the Danube River and the occurrence

of Potamogeton nodosus reflect an improved water flow into the opened polder area.

The better water exchange was also documented by a decreasing salinity in the

northern polder area. However, applied merely during one vegetation period

following the restoration measures as element of success control, monitoring

documents only a first step towards an improvement and does not depict the long-term

evolution in the area.

Water macrophytes can be used as quality indicators of physical and

chemical parameters, for ater dynamics (circulation, exchange, velocity, sedimentation),

filtering capacity, nutrient content and salinity. The reaction of macrophytes to

changes following restoration measures can be used for the evaluation of restoration

successes.

The reconnection of abandoned agricultural polders areas of Babina and also of

Cernovca and the restoration of the wetlands functions were documented by the

recolonisation of water macrophytes and their communities with different indicator

values.

The repartition of the water macrophytes and their communities is obviously and

strongly interdependent with flow velocity, turbidity and nutrient input in the restored

areas.

Species characterised by a broad ecological amplitude such as for example

Potamogeton pectinatus are among the first re-settlers, so are free floating species,

species that enter in the area with the water flow. The diasporas of rooted

macrophytes that occurred in the first colonisation phase survived in the studied area’s

soil.

The shorter the area’s period as drained polder, the more rapidly the

restoration process of characteristic plant communities could occur. This can also

be documented in comparison with the two islands Babina and also Cernovca. The

species diversity grows rapidly over the first two years and stabilizes in the third and

forth year.


60

Fig. 1 - Restoration area Popina fishponds (EC21 and EC22).


61

The reed’s filtering function developed right from the start and became

clearly apparent with the occurrence of species such as for example Utricularia

vulgaris and Hydrocharis morsus ranae that develop small belts along the reed borders

in sites were the water is flowing into the channels after being filtered by the restored

reed. The growing abundance-dominance of these species provides evidence of a well

operating filter system. In particular the characteristic species of the Hydrocharition

alliance are quality indicators for an intact ecological status, i. e. clear, moderately

eutrophic or euthrophic-mezotrophic waters. Along the borders of canals showing this

type of vegetation they also serve as indicators of a good filtering capacity of the areas

reeds.

The decrease in salinity became evident with the parallel decrease of dominant

species such as Azolla filiculoides, Zannichellia palustris serving as indicators of a light

water salinity.

The first opening in the circular dam on the crossing point with the dam

between EC 21 and EC 22 in the Popina area has improved the ecological situation in

the polders but this was not enough to ensure the water circulation and exchange in the

area.

The site-specific biodiversity which is conditioned by the hydrological regime

can only be preserved in the long term by the maintenance of water circulation and water

exchange. For this reason the reactivation of the old water courses, i. e. the „gârla“ on

Babina, Cernovca and Popina islands, had a crucial effect on the area’s ecological

functioning.

References

COOPS H., HANGANU J., 2000, 6 Aquatic vegetation, In: Ecological gradients in the

Danube Delta. Present state and man induced changes. Oosterberg, W., Staraş, M.

(eds.), RIZA rapport 2000.015, 95-109, Lelystadt.

ELLENBERG H., WEBER H. E., DÜLL R., WIRTH V., WERNER W., 2001, Indicator

values of te plants in Central Europe (in German), Scripta Geobotanica. 18: 1-

264.

LAGENDIJK O., SCHNEIDER E. (edit.), 2000, Perspectives on Popina.

Recommandations for ecological resetoration and wise use of former fishponds in

the Danube Delta Biosphere Reserve/Romania, DDNI, WWF, RIZA RIZA-

workdocument 2000.137X, 58.


62

KRAUSCH H.-D., 1996, Farbatlas Wasser- und Uferpflanzen, Ulmer Stuttgart, pp. 315.

MARIN G., SCHNEIDER E. (edit.), 1997, Ecological restoration in the Danube Delta

Biosphere Reserve/Romania. ICPDD Danube Delta Research and Design

Institute /Umweltstiftung WWF Deutschland, 120.

OOSTERBERG W., STARAŞ M., (edit.), 2000, Ecological gardients in the Danube

Delta. Present state and man induced changes. RIZA rapport 2000.015, Lelystadt,

168.

PENNING W. E., MJELDE M., DUDLEY B., HELLSTEN S., HANGANU J.,

KOLADA A., VAN DEN BERG M., POIKANE S., PHILLIPS G., WILLBY N.,

ECKE F., 2008, Classifying aquatic macrophytes as indicators of eutrophication

in European lakes. Aquat. Ecol., 42, 237-251.

SCHNEIDER E., ŞTIUCĂ R., TUDOR M., COVALIOV S., 2004, 10 YEARS OF

RESTORATION IN THE DANUBE DELTA, WWF-Auen-Institut & INCDDD –

Institutul Naţional de Cercetare-Dezvoltare Delta Dunarii, 17.

SCHNEIDER E., TUDOR M., STARAŞ M., 2008, Evolution of Babina polder after

restoration works. WWF Germany and Danube Delta National Institute for

Research and Development. 81.

SCHNEIDER E., 2009, Aquatic macrophytes in the Danube Delta – indicators for water

quality and habitat parameters. Studia Universitatis Babeş-Bolyai, LIV, 1, 2009,

21-31.

STARAŞ M., 2001, Restoration programme in the Danube Delta: achievements, benefits

and constraints, River restoration in Europe. Practical approaches, Conference

on river restoration, Wageningen, The Netherlands, 2000, Proceedings, 95-101.

Author1 Erika SCHNEIDER-BINDER

[email protected], [email protected]

KIT-Karlruhe Institute of Technology -

Univerity of Land Baden-Württemberg and

Research Center of Helmholtz Society

Department WWF Auen-Institut,

Josefstrasse 1,

76437 Rastatt /Germany

mailto:[email protected]

mailto:[email protected]

AQUATIC MACROPHYTES AND THEIR USE AS ECOLOGICAL...

Documents

Transcript of AQUATIC MACROPHYTES AND THEIR USE AS ECOLOGICAL...