ciliated colonization of artificial substrates in different saprobic conditions in a running water

8
Actn hydrovhiin. hyclrobiol. lb (1987) 6, 187-494 B. P'HIMC and I. HABDIJA Department of Zoology, Faculty of X;,tiiral Scientes, Vniverslty of Zagreb Ciliated Colonization of Artificial Substrates in Different Saprobic Conditions i n a Running Water Sumnmry: This work investigates the effect of water current velocit'y and organic. load on the colonization rate of ciliated Protozoa in periphyton communities. .btificial substrates (glass slides) were placed at three stations in a small mountain stream which runs through urban and industrial areas. The first station was located in an oligosaprobic to beta-meaosaprobic zone, the second in an alfa-mesosaprobic zone, and the third station in an alfa-mesosaprobic to polyaaprobic zone. At each station three substrates were placed in biot,opes of different current velority values (5 ... 20 cm,' sec., 20 ... 40 cmisec. and 50 ... 70 cmisec.). Wit'h such a distribution of artificial substrates it was possible to study the effect, of the water current velocit'y on the colonization dynamics of ciliates in particular saprobic zones. In trodue tion The colonization of Protozoa on ail artificial substrate depends on the invading rate, extinction rate, and interaction between species and environmental conditions (CAIRNS : CAIRNS et al.). According to ZIMMERMANN the most decisive ecological factors for the development of periphyton communities in running waters are current velocity and organic load. As ciliated Protozoa are a very important link in the for- iiiatiori and metabolism of periphyton cominunit~ies these investigations were carried out in a mountain stream in order to determine the effect of current velocity on their colonization in different saprobic conditions. The significance of these inrestigat ions can be seen i ti the assumption that the interaction between ciirrent velocity arid or- ganic load results in specific consequences for the creation arid the developnieiit of periphyton communities in mountain streams. I11 a nonlinear regressive analysis of enipirical data, instead of using the 11011- interactivc island coloiiization model S(t)=&'en (1 -e-"l) (MACARTHUR and ~VILSOX) due to objective difficiilties in processing, the folloaing logarithmic function nas used : S(t)= a 111 t & b, in which u and b are coefficients of regression which defiiie the dynamics of colonization. Materials and methods The colonization dynamics of ciliates on artificial substrates was studied at three stations located in a small mountain stream Veliki potok, which flows through an ur- banized and industrialized area of Zagreb. At each of the station (from 1 to 3), which

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Actn hydrovhiin. hyclrobiol. l b (1987) 6, 187-494

B. P'HIMC and I. HABDIJA

Department of Zoology, Faculty of X;,tiiral Scientes, Vniverslty of Zagreb

Ciliated Colonization of Artificial Substrates in Different Saprobic Conditions in a Running Water

Sumnmry: This work investigates the effect of water current velocit'y and organic. load on the colonization rate of ciliated Protozoa in periphyton communities. .btificial substrates (glass slides) were placed a t three stations in a small mountain stream which runs through urban and industrial areas. The first station was located in a n oligosaprobic to beta-meaosaprobic zone, the second in an alfa-mesosaprobic zone, and the third station in an alfa-mesosaprobic to polyaaprobic zone. At each station three substrates were placed in biot,opes of different current velority values (5 ... 20 cm,' sec., 20 ... 40 cmisec. and 50 ... 70 cmisec.). Wit'h such a distribution of artificial substrates it was possible to study the effect, of the water current velocit'y on the colonization dynamics of ciliates in particular saprobic zones.

In trodue tion

The colonization of Protozoa on ail artificial substrate depends on the invading rate, extinction rate, and interaction between species and environmental conditions (CAIRNS : CAIRNS et al.). According to ZIMMERMANN the most decisive ecological factors for the development of periphyton communities in running waters are current velocity and organic load. As ciliated Protozoa are a very important link in the for- iiiatiori and metabolism of periphyton cominunit~ies these investigations were carried out in a mountain stream in order to determine the effect of current velocity on their colonization in different saprobic conditions. The significance of these inrestigat ions can be seen i t i the assumption that the interaction between ciirrent velocity arid or- ganic load results in specific consequences for the creation arid the developnieiit of periphyton communities in mountain streams.

I11 a nonlinear regressive analysis of enipirical data, instead of using the 11011-

interactivc island coloiiization model S(t)=&'en (1 -e-"l) (MACARTHUR and ~ V I L S O X ) due to objective difficiilties in processing, the folloaing logarithmic function nas used : S(t)= a 111 t & b, i n which u and b are coefficients of regression which defiiie the dynamics of colonization.

Materials and methods

The colonization dynamics of ciliates on artificial substrates was studied a t three stations located in a small mountain stream Veliki potok, which flows through an ur- banized and industrialized area of Zagreb. At each of the station (from 1 to 3), which

488 PRIJIC, B., I. HABDIJ.~: Ciliated Colonization of Artificial Substrates

heloiig to different, saprohic zones, three microhahitats were defined with regard to the crirreiit, velocit,y of water (Tab. 1 ) . In each of the microhahit~at~s seven glass slides were fixed on t'he ripper side of a brick. The qualitative and quantitative analysis of ciliates n-as carried oiit' after 2, 5, 10, 15, 20, 25 and 30 days. A s long as tmhe periphyton deiisity allon-ed, microscopic esaminat ions were pei.formed on exposed glass slide. When a non-transparent layer was formed, periphyton mas scraped off and a suspension was made i n a determined rolii~iie. .A11 samples were t8aken at i ... 1 0 o'clock a.m. and examined on the same day. 1)et~crrniiiat~ioii of species was car- ried out on lire inaterial. lnrestigatioiis took place i i i the atit'iiinri 1982 and spring 1983 at, appoxiinat.ely the same teniperat , i i i~ and sapmhica conditioiis.

The nonlinear regression analysis of empirical data is based or1 estahlishing t'he logarithinic funct'ioiial relation hetween t h e number of colonized species S and coloniza- t'ion time f 111 t + b ) . From the eiiipirical data, by nieans of the principle of least squares, approriniat'e cwves of colonization were worked out. The chi-square goodness of f i t test was taken for the degree of fiinctional connection. -4s the hasic criterion for the determination of differences in t'he dynainics of ciliated Protozoa colonization dcpeiiding 011 currelit wlocity a i d organic load, t'he colonization rate

(C.R.) u x s taken, eyiial t o t h r derivation of fiiriction r:==:), and the t ime of sta-

d d t

hilization of colonization (S.T.) 011 t1aJ.s whcn -reached a value of 0.1

-1s a third criterion the nuinher of species a t the t'ime of stahilizat'ioii of colonization

, 11-hicli can be conipared t o t'he equilibrium from 0.1 -

tjht! lllodel Of . \ . IACA~RTHUR R l l d FYILSOX.

Results

The distri1)utioii of iiiicrohahitat,s a t t,iiree sampling stat'ioiis wit'li regaid to ciirrent velocity arid the mean \-allies of some physical-chemical parameters &ken during the process of coloiiizat.ion are shown i n Tab. 1 . -4nalysing the ~~hysical-chemical pro- pcxties and saprohic le\-el, obtained on t.he hasis of saprohiologica'l a d y s i s ( HABDIJA), it can he concluded tha t t.he first, three artificial substrat'es (1/I ... 1/lII) were exposed in an oligosaprobic t o beta-inesosaprohic zone of organic load. I-alues of water t'em- peratwe, 0,-concentration, K J I ~ i O ~ - c o ~ ~ s u i i i p t i o ~ i arid mineral salt. content indicate clean spring naters. The other three slihstiates (?,'I ... 2/III) iverc exposed in an alfa- iiiesosilprohic zoiie of load, which is iiidicated by the increased values of KMiiC),,- consuniption and miiieral salts. C'olonization of ciliates oil t'lie last two snbstrabes (S j l and 3/IJ1) crolved iinder t h r inflritvicr of stmngly loaded 1i-at.w (alfa-mesosal,ro~-,ic t o pol-saprobic zoiiv). In spit'e of the high c!olit.eiit of organic. inaterial a i l t i analysed mineral salts, par t~ici i lar l~ ortho-pliosphat'e. the oxygcn concent'ration was close to the saturation point.

Graphic representat'ions of the changes in the nnmber of species of ciliated Protozoa dilririg 30 days of colonization on the artificial suhst.rate demoiist~rate tha t the degree of orgaiiic pollution and ciirrent ~e loc i t~y has a significant interactional effect on the

Acta hydrochiin. hydrobiol. 15 (1987) 5 489

Table 1. Distriblition of microhobitats i L t sampling stations wit'h regard t'o current velocity and rnean values of some physical-chemical parameters measured during the colonization Tabelle 1 . Vert,eilung von Mikrohabitaten an Probenahmestellen in bezug a u f die FlieBgeschwindig- keit ulld ;\littelwert,e von physikochemischen Parametern, die xahrend der Besiedlung geniessen wurden

1 0-b l/I 5-20 1/11 "-40 Autumn 7.2 10.7 15.2 0.22 0.009 0.17 35.2

50-7,) Spring 10.7 10.4 20.0 0.26 0.009 0.13 -

2 a 211 5-20 ,ilI 20-40 Autunin 7.1 10.7 40.7 0.84 0.037 1.12 70.0

2,111 30-7,, Spring 11.2 10.4 37.5 1.00 0.073 0.76 -

3 a-p R / l 3-20 - - Aut1imn 9.2 10.1 78.6 1.08 0.073 1.38 95.5

3,ilI .i,)-70 Spring 11.6 9.8 50.1 1.30 O.i:39 -7.01 -

dynamics of colonizat~iori (Fig. I a'rid 3 ) . Significant differelices in the niiiiiher of colo- nized species and colonization rate conditioned hy these two factors became obrioiis after only two days of exposlire of artificial srihst'rates and coiit,itiued till the end of the experiment. Fig. 1 and 2 demonstrate tha t higher degreesof organic pollution and a low- er current velocit,y condition a greater niiinher of colonized species. Thus, in t,he aiitumn period, for example, after two days of exposure a t the first st,atioiis, depending on the current velocity (l/I, 1/11 or 1/III) 4, 3 01' 1 species were present, a t t'he second stnt'ion 14, 9 or 6 species, and at the third stat,ion, on the first microhahitat 15 species and on the secoiid 8 species of ciliat'ed Protozoa.

Figures 1 and 2 cont>ain logarit,hrnic curves worked out by a nonlinear regressive analysis of dat,a obtained 011 a number of species in the process of coloiiizat'ioii. The

Table 2. Sonlinear regrcssion analysis of model S([)=u In t+b a t three stat'ions: S.T. =time of stabilization of colonization in days; S.N.S. =number of species at, the time of stabilization of colo- nizat,ion and chi-squares ( ~ 2 ) wit,h corresponding level of significance (a). See text. Tabelle 2. Nichtlineare R'egressionsanalyse des Modells S ( Q = ~ In t k b an drei Stationen: S.T. = St>abilisierungszeit der Eesiedlung in Tagen; S.N.S. = A-lrtenzahl zur Stabilieieruilgszeit der Besiedlung und Chi-Quadrate ( ~ 2 ) mit, entsprechcnder Signifikanzstufe (a). Siehe den Test

Sapro- S.T. R.S.S. ~2 a S.T. S.S.S. X? a S.T. S.S.S. x'! a bic level

~~~ ~

o-b 23.0 9.5 (J.79 -=0.99 23.1 8.0 1.26 <0.93 30.3 1V.7 3.7 <0.3 J a 25.9 18.3 1.46 -=0.95 28.6 18.5 0.91 -=0.98 42.9 16.4 4.28 <0.3 4 a-p 17.3 19,s 0.77 <0.99 - - - - 36.2 18.2 1.44 -=0.93

M o-b 13.8 10.2 2.22 e0 .86 30.7 12.2 6.16 c0.3 69.7 10.6 0.71 -=0.99 E L . a F,

9.0 14.9 3.77 -=0.70 43.3 14.3 7.6 ~ 0 . 2 16.1 12.4 3.57 -=0.7 - - 35.7 19.4 3.61 <0.3

.- v1 a-p 36.1 20.9 0.39 e0.995 - -

S t o t i o n 7

1 / a 1 5 =2,31 In 2 + C,?3

25

20

qrE 5 70 IS 20 25 30

- 2 /m S=4,29 I n t + Q3

-

0

U o v

2 / 1 S=2,591n t + 9,86

25 t 2 20 .- u aJ 4 * L O

75

d 10 2

5

0 5 I0 15 20 25 30

D O Y

3 I T 25 1 S=1,75 I n t 4 14,78

Y 20 aJ u aJ .- 2 15

4-

10 d 2

5

0 5 10 15 20 25 30

D O Y

I0 I- 0

'' 5 10 15 20 25 30

D O Y

S t a t i o n 2

2 /n 5=2,86 l n t + 8,91

5 10 6 20 25 30

S t a t i o n 3

1 lm S=3,031nt + 937

Fig. 1. Effect of organic load and current velocity on colonization of ciliated Protozoa, (micro- habitats from l/I t o 3j111) and throwtic colonization curves. Alutumti 1982. (See test) Abh. 1 . X~is\\irlciiiig \-on orgariisclicr Bclnstiing t int1 FlieBeescIi\~iiidiglieit, aiif die Besiedlung iiiit Cilinteii (JIikrohabitatc ron 1 j1 bis 3)'III) iind theoretische Bes~,c\lu~igsliu~ven. Herbst 1952. (Siehe Test)

S t a t i o n I

I I1 1 jx 1Jn

25

20

1 S=1,381n t .+ 6,56

- S=3,57 I n t + 6,60

- 0

25

5

0

0 15 }- 0

5

5 10 75 20 25 30

Day S t a t i o n 2

5 10 15 20 25 30

D O Y

3 / 1 1

S = 3 , 6 1 1 n t + 7 9 3

5

0

S =2,96 In t + 0,Sl t

2 /m S=1,61 f n t -t 7,89

DOY

S t a t i o n 3

Fig. 2. Effect of organic load and cnrrent velocity on colonizst'ion of ciliated Protozoa (micro- habitats from l/I to 3/ITI) and theoretic colonization curves. Spring 1983. (See text) Ahb. 2. B~swirkung von organisclier Belastung und Flieflgeschwindigkeit nnf die Besiedlung niit Cilioteri (Miltrohnbitste von l/I bis 3IIII) und theorctisclie Besiedluiigskutven. Ftuhjalir 1983. (Siehe Text) 34 Acta hydrochim. hydrobiol. 15 (1987) 5

492 PRINC, B.. I. HABDIJA: Ciliated Colonization of Artificial Substrates

presented theoret,ic logaritliniic curves geiierally sho\v clearly t'he course of the first 30 days of coloiiizatioii. This is indicated hy largely low values of chi-squares (Tab. 2). As the critical value for 12.59(for 6 degrees o f freedom) iioiie of t he t.heoretica1 distribution of species caii lie rejected. Extrenie iiicreases or decreases iri t,he number of species, i.e. deviations from the logalit hiiiic cotii se of coloiiizat~ioii, are mainly the consequence of biotic and abiotic chxiigts oii tlie siibst'rate, arid are part'ly t h e constqiieiice of siidden hydrologic c h a i i p (ai.cl \ \ i t 1 1 t h i s a drift,) which are coinmoll in sinall inorriitaiii streams.

Table 2 preseiits the results of a iioiiliiiear i,cgiu;si\-e aiialysis of einpirical data. The time necessary for stabilizatioii of coloiiizatioii (S.T.) expressed i n days and t,he nuniher of specics at, the time of stahilizatioii of coloiiizatioii ( S A .S.) were t8akeri as paraiiieters for tlic: detelmiiiiatioti of tliffereiiccs i i i coloriizatioii a i d its depc~ide~iice oii current velocity aiid organic load. Both values were takeii when t'he colonizatioii rate was 0.1 species prr dav. ~)ilI'iiig the peliod of o\)servatioli of 30 days, a stabiliza- tiori of colonization n-as avhieveti a t tlie niajorit>- of iiiicroliahitats. C'onipariiig t,he compiited .\-allies of the ~irii i i lwr of speci lid the tiinc necessary for t,hc st,aliilizatioii of colotiizat'iori, i t caii he coi:clridcd tlia eiit ial diffei,eiices i n the dynamics of colo- nization exist in the autumn and spriiig periods. I n thc autuiriii period of 1982 the longest time tiecessary for the stahilizatioii of tlit ciliiited fauna was necessary for the periphytoii comiiiiiiiity ivhich devcloped it1 t,he alfn-riiesosa~)ro})ic zoi~e. 111 the spring period the sitiiatioii was the opposite ~ i i e and the sta izatiori of a commtiiiit,y was t he fa,stest i i i the alfa-iiiesosaprobic zoiie, aiid the slo t at t.he great,& clegree of pollrit,iori investigated. These differelices i t i the dynniiiic*s of coloiiizatioii can be explained by the irifliiericr of hiotic factors which take part in the formatioii of a complet'e periphyton commnnity (t'he sensoiial periodic developinelit of diatoms po- pulations). The curre l i t \.elocity effects the colonization rate considerably. Time iieeded for reaching equilihririni progressiwly iiicrcases together with the current8 velocity. This regiilarity is ot)ser\-etl i i i aliiiost a l l saprohic zorips i i i both seasons (Tab. 1). This is logical hecarise iii leiiitic areas organic det'rit,tis of antochthoiious and allochthoiious origiri hccoiiies sediiiieiited quicker and coiiscqtient,ly the condi- tions for reaching eyiii1il)riiiin are 11101'e favourable.

The iiumber of species a t t he tiiiie of stahilizatioii of coloiiizatioli (S.K.S.) is also depeiident on the saprohic degree a'ncl current wloc4tx. A correlat'iori bctween t'he iiumber of species and qiiantity of saprohic iiiaterial i i i water is very oLvioiis (Tab. 2 ) . The higher organic polltition is the greater the iiiiinhei. of :,pecics appears. This was coiifirmed in the spring and aiit'riiiin periods, with tlie cliffk rciicc t.hat a t the second station in aut,tiinri a greater tiuiiibei. of slwcies oc'ciii led thn i i i i i spriiig. i2t, the first and third stations approximately the same i i i i i i ihci . c.f species was prescrit in bot,lz periods. Higher current velocities dccrease the i i i r i i ihcr c f spc cic s iii cq~tilibriuiii. These differelices i r i the riiiniher of specics a t niicrohahitxts 11-it.h diift r( nt cr,ircnt velocit'ies a t oiie st.at.ioti are expressed to a intich lesser degree thaii t 'he diifercrices hetween microhabitats with the same currelit' relocity at, difftsreiit stations with differerit, aiiioiirits (of or'gaiiic iiiatter ir i t hc water.

Acta hydrochini. hgdrobiol. 16 (1987) 6 193

Discussion and conclusions

In this study the intention was to determine the effect of organic pollution and cur- rent velocity 011 the dynamics of caolonization of ciliated Protozoa during the first 30 days of exposure of artificial substrates. Fiinctjional analysis was carried orit, be- tween tjhe number of colonized species arid time. The logarithmic curve during tjhe 30 days observation period clearly illastrates the course of colonization a t the major- ity of mictrohahitats. It can be mentioned that pel-iphyton communit8ies in the pol- lut~xl biotopes (second and third station) are of a tc-mporary nat'ure. Namely, a t the second statioii after some time, due to the development of filamentous green algae, lithorheophilous periphyton is t~ansformed int'o a phytorheopliilous cominunity, while at the third stjatioii iiiainly a thick, dense layer of organic detritus is scdimented. Only a t the first station a true lithorheophilous periphyton was preserved. There- fore, a logarit'hmic or asymptotic (MACARTHUR and WILSON) curve course would be adequate after 30 days of coloriization only a t the first non-polluted station, while a t the other two st,at,ions the curve would show a differerit course.

Fluctuations in t'he number of species during the 30 days of coloiiizatioii on the art,ificial substrates demonstrated that the degree of organic polluttion and t'he cur- rent velocity have a decisive effect on t he dynamics of colonization. Organic pol- lution cont'rjbuted t o the increase of the number of colonized species and t'o an in- creased speed of colonization. This conclusion is based on the fact that the majority of ciliated Protozoa are bacteriophagous and detritophagous organisms which favour a higher amoiirit of saprobic matter in water.

The current velocity had an obvious effect on the dynamics of colonizatioii of ciliat'es with regard to a reduced number of species and a prolonged t'ime necessary for stabiliza- t,iori in lotic areas. The faster current velocity slowed down t'he init,ial sedimentation a n d adherence to the slides. AS t.he distribution of ciliates in riinniiig water is mainly or exclusively passive, the dispersal capacity of ciliated Protozoa depends, on the oiie hand, oii drift, which directly depends on the current velocity, and, 011 the other hand, on the ainoiint of dissolved arid suspended organic matters, which influences the bio- cenotic spectrum of a community developing on cert'ain microhabitats. Consequently, t,he colonization of ciliated Protozoa depends on drift, h u t also on the organic load which increases the already existing ecological differences in micrahabihats even more.

Ref arences

~ ' A I R : < s , J . dr.: 1962. The environmental requirements of fresh-water protozoa. Pp. 48-52 in: Tarewell, c'. $1. : Third seminar on biological problems in water pollution. United St,ates Public: Ncnlth Service Publ. Xo. 999-WP-25.

C'amxs, J. Jr., 31. L. DA~LBERG, K. L. DICKSON, N. SMITH and W. T. WALLER: The relationship of fresh-water protozoa,n communities to the MACARTHUR-WILSON equilibrium niodel. American Naturalist 103 (1969) 933, 439-454.

HABDKJA, I. : KJber den Zusaminenhang zwischen Saprobiezustand und iikologischen Faktoren in den Gebirgsbachen Veliki Markovac und Veliki potok (in Serbo-Croatian). Ekologija 6

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494 PRrarc. B., I. HABDIJA: Ciliated Colonization of Artificial 8ubst.rates

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