Distribution of Enteric Bacteria inAntarctic Seawater Surrounding theDumont dÕUrville Permanent Station(Ad�elie Land)D. DELILLE * and E. DELILLEà Observatoire Oc�eanologique de Banyuls, Universit�e P. et M. Curie, UMR-CNRS 7621, Laboratoire Arago,66650 Banyuls sur mer, FranceàLaboratoire d�epartemental, Site Technosud, Rambla de la thermodynamique, 66000 Perpignan, France

The survival of human enteric bacteria in the aquatic en-vironment has attracted much interest in view of its publichealth signi®cance. Untreated sewage has been releasedfrom Dumont d'Urville station, Antarctica, into theSouthern Ocean for several years. The spatial distributionof faecal bacteria indicators was investigated in summerice-free seawater near the French Base station of theAd�elie land area. A complementary seasonal survey of theoccurrence of faecal coliform bacteria was conducted inseawater under the winter sea ice in a speci®c station.Relatively high bacterial densities (maximum 103 CFU100 mlÿ1) were found in seawater surrounding the sewageoutfall. However, the contamination decreased rapidlywith increasing distance from the outfall. In all samplescollected further than 2 km, the bacterial indicators wereabsent or present in very small numbers. Faecal coliformswere not detected in samples collected at pristine sites.Despite these relatively low contamination levels, faecalbacteria were always detected in the vicinity of the sewageoutfall during the seasonal survey conducted in ice andunder-ice seawater. Ó 2000 Elsevier Science Ltd. Allrights reserved.

Keywords: faecal pollution; coliform; seawater; spatialdistribution; seasonal changes; Antarctica.

Introduction

Sewage wastes have been disposed into the ocean formany years. The survival of human enteric bacteria inaquatic environment has attracted an intense interest in

view of its public health signi®cance (Xu et al., 1982;Monfort and Baleux, 1991; Dupray et al., 1993; Gau-thier and Cl�ement, 1994; Nelson et al., 1996). Followingthe early exploratory expeditions in Antarctica, thegrowing human activity has resulted in the accumulationof waste of various types around larger installations(Lenihan et al., 1990). Such observations have stimu-lated interest in determining the environmental impactof human settlements, in observance of the fundamentalprinciples laid out for the preservation of this pristineenvironment. In the vicinity of the largest permanenthuman settlement in Antarctica (McMurdo station)Howington et al. (1992) and Mc Feters et al. (1993)reported that high concentrations of faecal coliformindicators were found along the ca. 1-km shoreline. Inmuch smaller and temporary settlement (summer stationof Terra Nova Bay) Bruni et al. (1997) found a persis-tent marine faecal pollution localized in the narrow zonestrictly surrounding the outfall or at the furthest 100 mfrom the seashore, both in ice-free waters and under theice. Untreated sewage has been released from Dumontd'Urville permanent station (Ad�elie land, Antarctica),into Southern Ocean for more than 40 yr. The outfalldischarged the sewage directly at the base of a deep shelfcli� at approximately 50-m of the seashore. In winter-time the frozen sewage accumulated between the outfalland the land fast ice.

This study was initiated to determine the occurrenceand distribution of faecal bacteria in the seawater sur-rounding the sewage outfall of the Dumont dÕUrvillestation.

Material and Methods

Study site and samplingStudies were done from December 1996 to January

1998 in the nearshore environment of Dumont dÕUrvillestation located on Petrel Island, Adelie Land, Antarctica.

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*Corresponding author.E-mail address: daniel.delille@wanadoo.fr (D. Delille).

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The ocean adjacent to the settlement characteristically iscovered by sea ice (ca. 1±1.5 m thick) during much of theyear. Sea ice usually breaks out in summer (December±January) and reforms during the fall (May). The sea-water temperature ranged from +0.5°C in summer to)2.1°C in winter. Ice free seawater samples were takenfrom 25 stations regularly distributed around the sewageoutfall of the station in January 1997 and December1998. Control (pristine) samples were also collected at`Cap Jules' and `Rocher du d�ebarquement' about 30 km,respectively to the north and west of Petrel Island.Samples were collected directly at seawater surface usingsterile glass bottles. Bacterial analyses were begun in the`Dumont dÕUrville marine biological laboratory' nomore than one hour after the sampling.

During winter, weekly sampling in underlying sea-water allowed a regular survey of coliform bacteria.After drilling through the ice cover, using a 10-cm (in-ternal diameter) ice-coring auger, subsurface seawatersamples were collected in sterile glass bottles.

Bacterial enumerationThree replicates of each of the seawater samples were

®ltered through membrane ®lters (0.45 lm, Sartorius)

and then placed on Tergitol agar supplemented withTTC as described by Carlucci and Pramer (1960). Plateswere incubated for 24 h at 37°C. Typical colonies werecounted and the number of bacteria was calculated fromthe volume of ®ltered water and expressed as colonyforming units (CFU 100 mlÿ1).

Results

The spatial distribution of coliform bacteria is shownin Figs. 1 and 2. The highest density of enteric bacteria(850 CFU 100 mlÿ1 in January 1997 and 1200 CFU 100mlÿ1 in December 1998) was recorded in the direct vi-cinity of the outfall. The di�erences observed betweenthe two data sets were probably related to the di�erenttimes elapsed after ice breaking (2 weeks in December1998 and 4 weeks in January 1997). At stations locatedat more than 2 km faecal bacteria were present in lowdensity (<5 CFU 100 mlÿ1) or absent. Coliform werenot detected in samples collected at `Cap Jules' and`Rocher du D�ebarquement'. Fig. 3 shows the seasonaloccurrence of coliform bacteria in under-ice seawater(station A). From this ®gure it is clear that faecal indi-cators were always present in the direct vicinity of theDumont dÕUrville station.

Fig. 1 Spatial distribution of enteric bacteria in the vicinity ofDumont dÕUrville station. 20 January 1997, 4 weeks after icebreaking (CFU 100 mlÿ1).

Fig. 2 Spatial distribution of enteric bacteria in the vicinity of Du-mont dÕUrville station. 25 December 1997, 2 weeks after icebreaking (CFU 100 mlÿ1).

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Discussion

A loss of bacterial culturability has been shown toreduce the detection of enteric bacteria in marine envi-ronments. However, it was suggested that this observa-tion does not detract from the use of coliforms asindicators of recent contamination (Elliot and Colwell,1985). In any case, the observed enteric bacterial countswill be minimal values.

In contrast with Mac-Murdo and Terra Nova Baystations, Dumont dÕUrville settlement is located in anarea of intense animal life: Weddel seals (Leptomychotesweddeli), Adelie penguins (Pygoscelis adeliae), Emperorspenguins (Aptenodytes forsteri) (Fig. 4). Drainage out-

fall of penguins rookeries contains very high hetero-trophic bacterial populations (Delille, 1987). Coliformbacteria have been detected in the more crowded Adeliepenguin's rookeries. However, the faecal pollutionplume is too clearly centred on the human sewage out-fall to be attributed to an animal contamination. Thus,as reported for Mac Murdo (Howington et al., 1992;McFeters et al., 1993) and Terra Nova Bay (Bruni et al.,1997) stations, the Dumont dÕUrville settlement pro-duced a persistent marine faecal pollution both in ice-free and under-ice seawater. However the pollutionplume is localized in a relatively narrow zone strictlysurrounding the sewage outfall.

Several molecular mechanisms that allow a bacteriumto respond and adapt to stress have been elucitated(Matin, 1992; Henge-Aronis, 1993; Kolter et al., 1993).The natural self-puri®cation of seawater is caused bydiverse physical, chemical and biological factors.Among them antibiotic production by the marine or-ganisms has been reported to be particularly importantin the Antarctic environment (Sieburth, 1959). The pe-riod of survival of enteric bacteria in seawater is highlyvariable, ranging from fractions of an hour to weeks,depending on the speci®c characteristics of each organ-ism and on several other factors (Carlucci and Pramer,1960). Low temperatures seem to be relatively favour-able to the survival of faecal bacteria (Halton andNehlen, 1968; Baross et al., 1975), thus, as reported forautochthonous heterotrophic bacteria (Delille et al.,1988; Delille and Perret, 1989) nutrient availabilityrather than low temperature will reduce the activity ofenteric bacteria. Bacteria could enter in a physiologicallyactive, yet non-recoverable, state for extended periods(Nilsson et al., 1991; Smith and McFeters, 1993). Fur-ther experiments involving more physiological studieswill be necessary to document the observed persistenceof enteric bacteria in the environmental conditions ofAntarctic seawater.

This research was supported by the `Institut Francßais pour la Re-cherche et la Technologie Polaires'. This work is dedicated to Pascal LeMauguen, Bruno Fiorese and Dario Lattanzi who lost their lives on 8February 1999, during logistic operations near Dumont dÕUrville sta-tion.

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Fig. 4 Spatial distribution of major penguin roockeries (Pygoscelisadeliae: black circles, Aptenodytes forsteri: black star) in thevicinity of Dumont dÕUrville station.

Fig. 3 Seasonal changes of enteric bacteria in ice covered seawater(Station a, austral winter, 1997).

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