life history characteristics of cladocerans cladocera) fed on wastewaters

Acta hydrochim. hydrobiol. 33 (2005) 2, 133−141 133

S. Nandinia, Life History Characteristics of CladoceransM. Hernandez Valdeza,S.S.S. Sarmab (Cladocera) Fed on Wastewatersa UIICSE, Division de

Recycling domestic wastewaters is one way to maximize the utilization of freshwater. Al-Investigacion y Posgrado,though sewage treatment plants help to remove particulate wastes, organic matter stillUniversidad Nacionalremains, which can be used to harvest sizeable populations of zooplankton. In an effortAutonoma de Mexico, Campus

Iztacala, AP 314, CP 54090, to identify cladocerans which could grow on this organic matter, we tested the life tableTlalnepantla, Edo. de Mexico, demography of the commonly found cladocerans (Alona rectangula, Ceriodaphnia dubia,Mexico Moina macrocopa, and Daphnia pulex) feeding on wastewater at three different stages of

b Laboratorio de Zoologıa purification (tank that receives crude wastes (A), the biological reactor (B), and the penulti-Acuatica, Division de mate stage of the treatment process (C)) from the Iztacalco water treatment plant inInvestigacion y Posgrado,

Mexico City. Experiments were conducted using the medium from each of the 3 tanksEdificio UMF, Universidad

previously mentioned and a control of Chlorella vulgaris at 1.0 · 106 cells mL�1. We foundNacional Autonoma de Mexico,that the average lifespan ranged from 5...30 days with D. pulex living the longest. TheCampus Iztacala, AP 314,growth rate, which ranged from �0.57 to +1.5 was highest for M. macrocopa. Our dataCP 54090, Tlalnepantla,indicate that Moina macrocopa, which had higher reproductive rates on wastewater thanEdo. de Mexico, Mexicothe controls, was most suited for growing in wastewaters.

Charakteristik der Lebensdaten von Cladoceren (Cladocera) bei Ernährung mitAbwasser

Die Wiederverwendung von Abwasser ist ein Weg zur Intensivierung der Nutzung desSüßwassers. Wenn auch die Abwasserbehandlung partikuläre Abwasserinhaltsstoffe weit-gehend beseitigt, so verbleibt doch organische Substanz, die einen Ertrag aus Zooplank-ton-Populationen ermöglicht. Zur Identifizierung von Cladoceren, die auf der Nahrungs-grundlage von Abwasser wachsen können, wird die Demographie verbreitet vorkom-mender Cladoceren (Alona rectangula, Ceriodaphnia dubia, Moina macrocopa undDaphnia pulex) auf Basis ihrer Lebenstafeln untersucht. Als Nahrung dient die partikuläreorganische Substanz (< 40 μm) aus der dreistufigen Behandlung von kommunalem Ab-wasser (Vorklärung (A), Biologie (B) und Nachklärung (C)) der Kläranlage von Itztacalcovon Mexico City. Zur Kontrolle dient die Ernährung mit Chlorella vulgaris bei einer Zellzahlvon 1 · 106 mL�1. Die mittlere Lebensdauer liegt bei 5...30 d und ist für D. pulex amgrößten. Die Wachstumsrate reicht von �0.57 bis +1.5 d�1 und war für M. macrocopaam höchsten. Die Daten bestätigen, dass Moina macrocopa, die im Abwasser höhereReproduktionsraten als in der Kontrolle erreicht, am besten für das Wachstum in Abwassergeeignet ist.

Keywords: Demography, Life Table, Algal Food

Schlagwörter: Demographie, Lebenstafel, Algen-Nahrung

Correspondence: S. Nandini, E-mail: [email protected]

DOI 10.1002/aheh.200400561 © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

134 S. Nandini et al. Acta hydrochim. hydrobiol. 33 (2005) 2, 133−141

1 Introduction

The increasing shortage of freshwater globally has led to theadoption of several techniques to maximize the use of thisinvaluable commodity. One of them is the recycling of do-mestic wastewater through sewage stabilization plantswhich sediment or remove particulate waste matter [1]. How-ever, a considerable quantity of organic matter still remainsin the water even in the final stage of sewage stabilizationponds and this supports a high diversity of phytoplankton,zooplankton, and even fish [2].

Ciliates, rotifers, cladocerans, and copepods generally domi-nate the zooplankton community in freshwater ecosystemsincluding sewage stabilization ponds [3, 4]. Among thesegroups, in terms of biomass, cladocerans form the largestgroup due to their large size and parthenogenetic repro-duction. They are also generalist feeders, filtering bacteria,particulate organic matter, algae, and even ciliates from themedium [5]. Thus, they transfer energy efficiently from lower(such as bacteria and phytoplankton) to higher (such as fish)trophic levels [6, 7].

Mexico City is a mega city with more than 20 million inhabi-tants. About 10 000 tons of sewage is produced daily; how-ever, the current sewage treatment plants are inadequateand in those that do function, the treatment is often not com-plete whereby large quantities of organic matter, Protozoa,and bacteria persist [4]. The water is often used for industrialor commercial purposes (such as car washing) and to fillfreshwater bodies such as Lake Xochimilco (Mexico City) orLake Zumpango (State of Mexico).

Mexico has a high diversity of zooplankton. For example,more than 300 species of rotifers and about 40 species ofcladocerans are known so far from the various water bodies[8, 9]. Alona, Ceriodaphnia, Daphnia, and Moina are somecladoceran genera commonly found in various waterbodiesin Mexico. Members of these genera are known to utilizeparticulate organic wastes. Quantitative data on their repro-ductive rates using such wastes are limited [10�12].

Cladocerans have been extensively used as bioassay or-ganisms, particularly to test the effect of food quality andtoxicants [13, 14]. The impact of these substances can bestudied by analyzing parameters such as filtering rates [5],somatic growth [15], or survival and reproduction relatedparameters [16]. Life table demography studies complementpopulation dynamics experiments, since the former give in-formation pertaining to an individual while the latter to popu-lations [17].

In a previous study [12], on an exclusive diet of organicmatter from a sewage treatment plant in Mexico City, weanalyzed the population dynamics of four cladoceran spe-

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

cies, Alona rectangula Sars, Ceriodaphnia dubia Richard,Moina macrocopa Goulden, and Daphnia pulex Leydig. Inthis study, on the same diet, we followed the life table demo-graphy of these four cladoceran species.

2 Materials and methods

The test cladocerans were isolated from local or nearbywaterbodies. Alona rectangula (length ± mean, μm)(430 ± 10) was isolated from Lake Chapultepec (MexicoCity) while Ceriodaphnia dubia (951 ± 40), Moina macro-copa (1286 ± 30), and Daphnia pulex (2413 ± 129) fromManuel Avila Camacho Reservoir in Puebla City (Mexico).All test species were cultured separately starting from asingle parthenogenetic female. They were fed on an exclu-sive diet of the green alga Chlorella vulgaris. C. vulgaris wascultured using Bold’s basal medium [18] in 2-L transparentbottles. Batch-cultured alga was harvested during the ex-ponential phase, centrifuged, rinsed, and resuspended indistilled water. The density of the algal concentrate was enu-merated using a Neubauer haemocytometer. For culturingas well as for the experiments with cladocerans we usedreconstituted moderately hard water. The medium wasprepared by dissolving 96 mg NaHCO3, 60 mg CaSO4,60 mg MgSO4, and 4 mg KCl in one liter of distilledwater [19]. For routine maintenance of the cladoceran popu-lations we used algal densities of 1.0 · 106 cells mL�1 or1.5 · 106 cells mL�1 (in terms of dry weight this was equiva-lent to 14.2 μg mL�1 or 21.3 μg mL�1). The cladoceranswere maintained in the laboratory for more than 2 years priorto experimentation.

We used water from the Iztacalco water treatment plant inMexico City as follows: Water from the first tank, which re-ceives crude wastes (A), the next tank in the sequence oftreatment, which is the biological reactor (B), and the penulti-mate stage of the treatment process, which has fairly clearwater, though some particulate organic matter is still present(C). In all the three tanks, disinfectants such as chlorinewere not used. Water from these tanks was brought to thelaboratory every alternate day during the entire duration ofthe experiment. The quantity of suspended solids present inthe wastewaters was estimated in quadruplicate followingCauchie et al. [20]. A known volume of the water from eachof tank was passed through a nylon gauze of 40 μm poresize (to remove large organic clumps), filtered using pre-weighed (Cahn electrobalance, Model C-33) WhatmanGlass fiber filters. The organic matter thus collected wasdried along with the filters at 105 °C for 24 h in an oven(Rhiossa HS 50�300 °C). The following day, the filters werereweighed. The quantity of organic matter was then derivedas the difference between the final weight (filters with driedorganic matter) and the initial weight (filters without theorganic matter).

Acta hydrochim. hydrobiol. 33 (2005) 2, 133−141 Life Histories of Cladocerans Raised on Wastewater 135

We tested the life table demography of each of the four cla-doceran species using the organic matter collected fromeach of the three tanks (A to C) and the control (C. vulgarisat 1 · 106 cells mL�1). For each treatment we used four repli-cates. Into each of the 64 test jars (= 4 test species · 4 treat-ments · 4 replicates) of 100 mL capacity, containing 50 mLmedium with chosen food type, we introduced 20 neonates(48 h old) from one of the four test species. All the treatmentjars were maintained at a constant temperature [(23 ± 1) °C]and continuous but diffused fluorescent illumination. The pHof the test medium was 7.1.

Following initiation of the experiment, we counted daily thenumber of individuals alive and the neonates produced.While the neonates as well as the dead adults were countedand discarded, the surviving individuals of each cohort weretransferred to a fresh medium containing the appropriatefood type. Observations were continued until the lastindividual of each cohort died.

We calculated the survivorship, life expectancy, fecundity,average life span, and the following parameters for each ofthe test cladocerans on each of the media tested [21].

Fig. 1: Age specific survivorshipcurves of Alona rectangula, Cerio-daphnia dubia, Moina macrocopa,and Daphnia pulex fed on alga,and on wastewater at three diffe-rent stages of purification (crudewastes: column A, biological reac-tor: column B, and the penulti-mate stage of the treatment pro-cess: column C). Experimentswere conducted using the cohort(20 individuals per cohort) lifetable method. Shown are themean ± standard error based onfour replicates (cohorts).

Altersspezifische Überlebenskur-ven von Alona rectangula, Cerio-daphnia dubia, Moina macrocopaund Daphnia pulex bei Ernährungmit Algen und Abwasser aus dreiReinigungsstufen (A � Vorklä-rung, B � Biologie, C � Nachklä-rung). Die Ergebnisse stammenaus Lebenstafeln von Kohorten(20 Ind. je Kohorte). Angegebensind die arithmetischen Mittel ±Standardabweichung des Mittel-wertes für vier Wiederholungen(Kohorten).


Gross reproductive rate = ��

0

mx

Net reproductive rate Ro = ��

0

lx · mx

Generation time: T = � lx · mx · x

Ro

Rate of population increase, Euler equation (solved iterat-ively)

�n

x=w

e�rx · lx · mx = 1

In these equations, lx is the probability of an individual sur-viving to an age class, mx is the age specific fecundity, Ro

is the average number of female offspring each female inthe population produces, and r is the growth rate of thepopulation.

In order to test whether there were any statistically signifi-cant differences among the life history variables of the


cladoceran species reared on different diets, we usedanalysis of variance, followed by post-hoc analyses (Tukey’smethod) where necessary [22].

3 Results

The quantity of organic matter (as determined from the dryweights) was highest in water from tank B as comparedto that of A or C. It was 4 μg mL�1, 31 μg mL�1, and39 μg mL�1 in water from tank C, A, and B respectively. Thisavailability of food is reflected in the life-history variables ofall the test species.

The age specific survivorship curves of all the test cladocer-ans were affected by the food with which they were cultured(Fig. 1). The species showed Type I survivorship pattern (rel-atively lower mortality during the younger age groups) onChlorella, which deviated towards Type II (i.e., continuedmortality during all age groups), or III (i.e., relatively heaviermortality in younger population) on the other diets. Survivor-ship was generally highest in controls. A. rectangula on adiet of water from tank C had a survivorship similar to thatin the control.

Fig. 2: Age specific fecunditycurves of A. rectangula, C. dubia,M. macrocopa, and D. pulex fedon alga, and on wastewater atthree different stages of purifica-tion (columns A, B, C, details inFigure 1). Shown are the mean ±standard error based on four repli-cates (cohorts).

Altersspezifische Fruchtbar-keitsraten von Alona rectangula,Ceriodaphnia dubia, Moinamacrocopa und Daphnia pulexbei Ernährung mit Algen und Ab-wasser aus drei Reinigungsstufen(A � Vorklärung, B � Biologie,C � Nachklärung). Angegebensind die arithmetischen Mittel ±Standardabweichung des Mittel-wertes für vier Wiederholungen(Kohorten).


All the test species showed a steady reproductive outputthroughout their life in controls (Fig. 2). However, this patternvaried in treatments containing food from the wastewatertanks. A. rectangula and D. pulex had higher fecundity onwater from tank B than from that of A or C. For C. dubiawater from tanks B and C supported a better reproductiveoutput than that of tank A. On the other hand, M. macrocopaproduced more neonates and over a longer period in waste-waters than in the controls.

Regardless of the taxa involved, the average lifespan rangedfrom 5 to 30 days; M. macrocopa had the lowest lifespanwhile D. pulex had 6 times this value (Fig. 3a). Post-hocTukey’s test revealed that water from tanks B and C sup-ported longevities similar to the control in A. rectangula andC. dubia, respectively. For M. macrocopa the averagelifespan was significantly higher when grown in water fromtank A and B than in the controls (P < 0.05, Tukey’s Test,Fig. 3a). The gross and net reproductive rates (Figs. 3b, c)showed trends similar to the average lifespan where thesevalues were higher in the controls than on the food fromwastewater tanks except for M. macrocopa where they weresignificantly higher than in the alga-fed treatment (P < 0.001,F-test) and in A. rectangula where water from tank B


Fig. 3: Selected life history varia-bles (average lifespan (a), gross(b) and net (c) reproductive rates,generation time (d), and the rateof population increase (e) ofA. rectangula, C. dubia, M. mac-rocopa, and D. pulex fed on algaand on wastewater at three diffe-rent stages of purification (tanksA, B, C, details in Figure 1).Shown are the mean ± standarderror based on four replicates(cohorts). For each variable of agiven cladoceran species (pre-sented as a group), bars contai-ning different alphabets arestatistically significant (p < 0.05,Tukey’s test).

Ausgewählte Variablen der Le-bensgeschichte (a � mittlereLebensdauer, b � Bruttorepro-duktionsraten, c � Nettoreproduk-tionsraten, d � Generationsdauer,e � Rate des Populationswachs-tums) von Alona rectangula, Ce-riodaphnia dubia, Moina macro-copa und Daphnia pulex beiErnährung mit Algen und Abwas-ser aus drei Reinigungsstufen(A � Vorklärung, B � Biologie,C � Nachklärung). Angegebensind die arithmetischen Mittel ±Standardabweichung des Mittel-wertes für vier Wiederholungen(Kohorten). Für jede Art (darge-stellt als Gruppe) sind die Diffe-renzen zwischen Säulen mit un-terschiedlichen Buchstaben signi-fikant (p < 0.05, Tukey�s Test).

supported the population as well as the control (Tukey’stest).

Depending on the treatment involved, the generation time ofthe tested cladoceran species varied from 1 to 30 days. Onlyin the case of D. pulex the generation time was significantlylower in treatments containing food from wastewater tanksthan in the controls (Fig. 3d). The rate of population increase


(r) ranged from �0.57 (D. pulex on water from tank C) to+1.5 (M. macrocopa reared on food from tank A) with theother species lying within this range (Fig. 3e). In general,cladoceran species fed on Chlorella had significantly higherpopulation growth rates than those fed on food from waste-water tanks (P < 0.05, F-test, Table 1) with the exception ofA. rectangula fed on food from tank B and M. macrocopagrown on water from tank A.


Table 1: Analysis of variance (ANOVA) for the demographic variables of the test cladocerans (A. rectangula, C. dubia,M. macrocopa, and D. pulex). DF: degrees of freedom, SS: sum of squares; MS: mean square, F: F-ratio, p: probability (levelof significance).

Varianzanalyse (ANOVA) der demographischen Variablen der untersuchten Cladoceren (A. rectangula, C. dubia, M. macrocopaund D. pulex).

Source of Variation DF SS MS F p

Average LifespanAlona rectangula

Food type 3 107.28 35.76 37.42 < 0.001Error 10 9.55 0.95

Ceriodaphnia dubiaFood type 3 96.39 32.13 7.06 < 0.01Error 12 54.58 4.549

Daphnia pulexFood type 2 1445.68 722.84 58.22 < 0.001Error 8 99.32 12.41

Moina macrocopaFood type 3 41.97 13.99 20.76 < 0.001Error 11 7.414 0.674

Gross Reproductive RateAlona rectangula

Food type 3 2432.58 810.86 25.70 < 0.001Error 10 315.5 31.55

Ceriodaphnia dubiaFood type 3 20255 6751.66 106.64 < 0.001Error 12 759.72 63.31



Net Reproductive RateAlona rectangula

Food type 3 151.2 50.40 20.22 < 0.001Error 10 24.9 2.49






Table 1 (continued)

Source of Variation DF SS MS F p

Generation TimeAlona rectangula

Food type 3 103.95 34.65 14.79 < 0.01Error 7 16.38 2.34




Population Growth RateAlona rectangula

Food type 3 1.19 0.39 5.49 < 0.05Error 10 0.72 0.072




4 Discussion

Deriving usable biomass from wastewater is one of the mainaims of water management [11, 23]. Microscopic obser-vations of the water used in our study revealed particulateorganic matter in small clumps, bacteria, and protozoans,which can be consumed by cladocerans [6]. City wastescontain large quantities of organic substances, which maychange depending on the month. Since we realized allexperiments within a short period (about 30 days), the varia-tion in the quantity of the organic load within this periodmight not be expected to vary strongly compared to varia-tions within a year [24]. We did not analyze the nutritionalquality of the organic matter present in the wastewaterssince our objective was to compare these four commonlyfound and well used cladocerans in aquaculture [25] in termsof their capacity to utilize organic matter from sewage treat-ment plants. We also did not quantify the amount of organicmatter consumed per individual cladoceran during the ex-


perimental period. However, we offered the test cladoceransnearly a specified quantity daily.

Not all cladoceran species grow well on organic wastes. Al-though it has been shown that Daphnia magna and D. similiscan utilize organic wastes efficiently for survival and popu-lation growth [10, 26], in the present study, D. pulex did notsurvive when fed on organic wastes from tanks A, B, or C.In crude wastes, D. pulex did not survive beyond 24 h. Thiswas evident from age-specific survivorship curves. Underoptimal conditions of food type and density, and tempera-ture, mortality is relatively low for most part of the organism’slife and thereafter it increases giving a rectangular mortalitycurve. However, in most cladoceran species, this trend devi-ates, because neonates (with which life table demographicstudies are begun) are sensitive to food types. As has beenshown in a previous study [12], here also we found thatwhen reared on organic matter from tanks A, B, or C, Moinamacrocopa showed higher reproductive rates than even in


Fig. 4: Relation between the average lifespan and thegeneration time of A. rectangula, C. dubia, M. macrocopa,and D. pulex fed on alga, and on wastewater. Plotted arethe replicated (cohorts) data for each treatment.

Verhältnis zwischen mittlerer Lebensdauer und Generations-dauer von A. rectangula, C. dubia, M. macrocopa undD. pulex bei Ernährung mit Algen und Abwasser. Dargestelltsind die wiederholten (Kohorten) Daten für jede Versuchs-reihe.

controls. The other three cladoceran species when fed Chlo-rella survived longer than when grown on wastewaters. Theshortest average lifespan recorded for M. macrocopa in thisstudy was comparable to the data recorded for this genuspreviously [27]. Generally, species of Daphnia have longerlifespan than many other genera including Ceriodaphnia,Moina, and Alona, as was observed in this study too whereD. pulex had a lifespan of more than 30 days.

Most cladoceran species produce fewer offspring at the be-ginning and towards the end of their reproductive period withthe peak production in the mid-reproductive stage [28]. Thispattern, roughly resembles a normal distribution curve. InMoina macrocopa this was evident in the wastewater treat-ments too. Rapid maturation, larger clutch size, and shorterlifespan gives Moina an edge over other cladoceran generain terms of higher rates of population growth. The positiver values of most cladoceran species are in the range of0.1 to 1.5 per day and they rarely exceed 2 [6]. Data on ther recorded for the tested species are within this interval. Foriteroparous taxa, generation time is positively correlated tothe lifespan. King [29] hypothesized that for zooplankton thegeneration is twice the median lifespan. In the present study


we also obtained a positive relation when the mean lifespandata of the tested cladocerans were plotted against thegeneration time (Fig. 4), although, the ratio was lower (1:1)

Of the four cladoceran species tested, neonates of A. rectan-gula, C. dubia and D. pulex showed increased survival withincreased processing of the crude wastes (tank A to the pen-ultimate tank C). Moina consistently showed better survivaland reproduction in all the treatments and therefore is themost suitable cladoceran, among those tested, to grow onorganic wastes from sewage treatment plants. Mass cultureof any cladoceran in wastewater tanks has not been under-taken yet. The organic matter in these tanks could be har-vested in the form of cladocerans, which in turn can be usedfor harvesting chitin which has several uses in the pharma-ceutical industry [11]. Wastewaters also carry pathogens andpollutants and hence the use of cladocerans harvested fromthese systems for edible fish culture is not recommended,although it is practiced in some countries [25]. This use ofcladocerans represents additional revenue from sewagetreatment plants.

Acknowledgements

This investigation was supported by a grant from PAPIIT(IN205900). S. Nandini and S.S.S. Sarma thank TheNational System of Investigators, Mexico (SNI-20520 &SNI-18723).

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life history characteristics of cladocerans cladocera) fed on wastewaters

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