Download - LIVE AND DEAD FORAMINIFERAL FAUNAS FROM SAINT-TROPEZ ...€¦ · Saint-Tropez Canyon (Bay of Fre´jus), which had never been studied before. In this paper, we want to assess the putative

LIVE AND DEAD FORAMINIFERAL FAUNAS FROM SAINT-TROPEZ CANYON (BAY OFFREJUS): OBSERVATIONS BASED ON IN SITU AND INCUBATED CORES

CHRISTOPHE FONTANIER1,3, FRANS JORISSEN

1, EMMANUELLE GESLIN1, SEBASTIEN ZARAGOSI

2, GERALD DUCHEMIN1,

MORGAN LAVERSIN1

AND MELISSA GAULTIER1

ABSTRACT

The impact of sedimentary processes on the live (rose-Bengal-stained) foraminiferal faunas and on the compositionof dead assemblages was investigated at a 373-m-deep stationin Saint-Tropez Canyon (Bay of Frejus, France). For the.150-mm fraction, biocoenoses and thanatocoenoses wereinvestigated in two 10-cm-long cores collected with a classicalBarnett multi-corer. In the 63- to 150-mm size fraction, livingfaunas were investigated in the first centimeter of thesediment. The first core was fixed with ethanol and rose-Bengal at the time of the sampling (the in situ core) whereasthe second core was stored in a culture room during a 2.5-year-long incubation before its fauna was investigated.

Both cores present similar thanatocoenoses (.150-mm sizefraction) that are substantially contaminated by neriticforaminifera presumably transported from adjacent shelves.The sedimentological analysis of a third core reveals neithergraded sediments nor erosional surfaces. Abundant organicremains are detected downcore in the muddy silt sediment. Allthese observations preclude the idea of deposition by a recentturbidite. Therefore, our canyon environment seems to behaveat present as a depocenter for a rather continuous flux of finesediment and resuspended organic matter originating fromshallower areas.

The living in situ faunas in the 63- to 150-mm and .150-mmsize fractions are quite diverse with a moderate evenness. Inthe .150-mm size fraction, the high abundance of interme-diate and deep infaunal taxa (Uvigerina elongatastriata,Bolivina alata, Melonis barleeanus, Globobulimina spp. andChilostomella oolina) underlines the importance of organicmatter focusing (and the related redox conditions) in thissubmarine canyon environment. The dominance of M.barleeanus and bolivinids in the 63- to 150-mm size fractionconfirms the eutrophic aspect of our study area.

Because of logistical problems, the incubated core sufferedimportant salinity changes throughout the 2.5 years ofincubation. Salinity ranged between 35 and 62 psu. Oxygenconcentration was almost zero at the sediment-water interfaceat the end of incubation. In the larger size fraction(.150 mm), only one taxon, Rosalina bradyi (Cushman,1915), survived these adverse experimental conditions. Itsdensity (516 ind/100 cm2) is two orders of magnitude higherthan that of the in situ core (3 ind/100 cm2). No livingforaminifera were found in the first centimeter of the 63- to150-mm size fraction. Rosalina bradyi was obviously the last

species able to reproduce and grow in the incubated core. Ourresults show that this taxon is capable of tolerating extremesalinity changes.

INTRODUCTION

Submarine canyons represent complex physico-chemicalbiotopes where the sedimentary dynamics and organicmatter focusing induce uncommon ecological conditionscompared to open-slope environments. Few studies exist onthe living foraminiferal faunas from these environments(Jorissen and others, 1994; Swallow and Culver, 1999;Schmiedl and others, 2000; Anschutz and others, 2002;Hess and others, 2005; Fontanier and others, 2005; Kohoand others, 2007). Nevertheless, submarine canyons andtrenches are important sinks for organic matter related tomarine primary production and terrestrial organic com-pounds (Epping and others, 2002; Tselepides and Lampa-dariou, 2004; de Stigter and others, 2007). Therefore,studies of the functioning of canyon ecosystems are crucialto appreciate the fate of organic carbon on ocean margins,in the past and in the present. Some recent studies havedemonstrated that highly diverse, living (rose-Bengal-stained) foraminiferal faunas dominated by deep andintermediate infaunal taxa (e.g., Melonis spp., Chilostomellaspp., Globobulimina spp.) thrive in inactive canyonscharacterized by organic-matter-enriched sediment andstable redox conditions within the sediment (Schmiedl andothers, 2000; Fontanier and others, 2005; Koho and others,2007). On the other hand, in some active canyon areaswhere gravity–flows are common, living foraminiferalfaunas are mainly composed of early colonizing andopportunistic foraminiferal taxa like Technitella melo,Bolivina subaenariensis and Hyalinea balthica (Jorissenand others, 1994; Anschutz and others, 2002; Hess andothers, 2005; Koho and others, 2007). In all cases, livingforaminiferal faunas from canyon environments differstrongly from those found in adjacent open-slope environ-ments (Schmiedl and others, 2000; Fontanier and others,2005). Moreover, some species dominating the organic-matter-enriched sediments of inactive canyons are impor-tant in paleoceanography. For example, Chilostomella spp.and Globobulimina spp. belong to the rare deep-sea taxaable to survive adverse environmental conditions prevailingduring sapropel deposition in the eastern MediterraneanSea or during Heinrich events in the North Atlantic Ocean(e.g., Baas and others, 1998; Casford and others, 2003;Abu-Zied and others, 2007). A better understanding of theirecology in the benthic environments where they livepreferentially is necessary to better appreciate theirpotential as paleo-environmental proxies.

Journal of Foraminiferal Research fora-38-02-04.3d 28/2/08 10:42:16 45

3 Correspondence author. E-mail: [email protected]

1 Laboratory of Recent and Fossil Bio-Indicators, Angers Universi-ty, UPRES EA 2644, 2 Boulevard Lavoisier, 49045 Angers Cedex,France, and Laboratory for the Study of Marine Bio-Indicators(LEBIM), 85350 Ile d’Yeu, France.

2 Environnement et Paleoenvironnement Oceanique (EPOC-OASU),Bordeaux 1 University, UMR 5805, Avenue des Facultes, 33405Talence Cedex, France.

Journal of Foraminiferal Research, v. 38, no. 2, p. 000–000, April 2008

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Since ecological observations of live (rose-Bengal-stained) foraminiferal communities from canyon systemsare still rather limited, we have decided to investigate theecological patterns of foraminiferal assemblages from theSaint-Tropez Canyon (Bay of Frejus), which had neverbeen studied before. In this paper, we want to assess theputative impact of sedimentary processes on the live (rose-Bengal-stained) foraminiferal faunas and the compositionof dead assemblages at a 373-m-deep canyon station(CAMT-5). In order to do so, we investigated both livingand dead foraminiferal faunas in the .150-mm size fractionfrom an in situ core, and we obtained various data aboutthe sedimentary environment of our study area (X-radiography, granulometry, colorimetry, sieve-residue ob-servations). We also inventoried the live (rose-Bengal-stained) foraminiferal faunas of the 63- to 150-mm sizefraction in the first centimeter of the in situ core. All corematerial was collected in May 2003. We might expect tofind two different foraminiferal assemblages. (1) In the caseof an active canyon characterized by repetitive depositionof turbidites, the living foraminiferal fauna could becomposed of opportunistic pioneer species (Alve, 1999;Hess and others, 2005). (2) In the case of a more quiet,passive canyon environment where large quantities oforganic matter and fine-grained particles accumulate, weshould observe a highly diverse climax community withspecialized foraminiferal taxa (Alve, 1999; Fontanier andothers, 2005). A second part of this paper deals with thesurprising faunal composition after a 2.5-year-long incuba-tion of a core collected at the same station in the samesampling period. In May 2003, we stored this core for afuture incubation experiment. Unfortunately, because oflogistical problems, the incubated core suffered importantsalinity changes throughout the 2.5 years of incubation.Salinity ranged between 35 and 62 psu. At the end ofincubation, oxygen concentration was almost zero at thesediment-water interface. Temperature was kept constant at,14uC. In view of the highly adverse experimentalconditions, we expected to find no living (rose-Bengal-stained) foraminifera at the end of the incubation period.The unexpected presence of a dense living foraminiferalfauna sheds new light on the survival strategies offoraminifera, and may help us to better understand theextraordinary tolerance of this group to adverse conditions.

STUDY AREA, MATERIAL AND METHODS

STUDY AREA

The narrow continental shelf characterizing the Bay ofFrejus (southeastern France) is incised by numerous poorlystudied canyon systems. Some studies using a submersiblewere conducted in the 1970’s to investigate the tectonic andsedimentary structure of Cenozoic deposits in the deepestparts of these canyons (Bellaiche, 1972; Bellaiche andothers, 1979). It appeared from these works that canyons,as typical polygenic structures, suffered dramatic erosionalprocesses during the Messinian crisis (Late Miocene)followed by sedimentary in-filling processes during thePlio-Quaternary age. However, none of these works couldprecisely describe the sedimentary patterns of the Holocene

sedimentation off Frejus. Station CAMT-5 (43u23.189N,6u46.629E) is situated at the head of Saint-Tropez Canyon(Bay of Frejus) at 373 m water depth (Fig. 1). It is bathed byMediterranean Intermediate Water derived from LevantineIntermediate Water (Millot, 1990). The physico-chemicalproperties in our study area can be deduced from conduc-tivity, temperature, and depth (CTD) measurements per-formed by Pierre (1999) at a nearby station (Station 1B;42u25.0009N, 4u55.0009E). Salinity is ,38.45 psu and tem-perature is ,12.7uC (Pierre, 1999). Oxygen concentration ofthe bottom water is ,4 ml/l (Gostan, 1968; Minas, 1970).

MATERIAL AND METHODS

Station CAMT-5 was sampled in May 2003 with aclassical Barnett multi-corer. This corer allows the collec-tion of sediment cores with an undisturbed sediment-waterinterface (Barnett, 1984). A first core (internal diameter9.6 cm, surface area ,72 cm2) was sampled for in situfaunal analysis. A second one was sub-sampled with aPlexiglas tube (internal diameter 5.9 cm, surface area,27 cm2) and stored for a long-term incubation at theLaboratory of Recent and Fossil Bio-Indicators (AngersUniversity, France). The sedimentological features of athird core were investigated at Bordeaux University. Allcores were collected from the same multi-corer deployment.Unfortunately, we did not sample replicate cores forforaminiferal analysis. Therefore, differences between our


FIGURE 1. Study area, bathymetry and geographical position ofStation CAMT-5 in Saint-Tropez Canyon (Bay of Frejus, France).

0 FONTANIER AND OTHERS

cores could be partially the result of putative micro-scalespatial variability.

In Situ Core Dedicated to Foraminiferal Analysis

The core dedicated to the in situ foraminiferal study wassliced horizontally onboard the ship; every 0.5 cm for thefirst 4 cm of the sediment and every centimeter between 4and 10 cm was sampled. Sediments were stored in 500-cm3

bottles filled with 95% ethanol containing 1 g/l rose Bengalstain (Walton, 1952). Problems and advantages related tothe use of rose Bengal staining were discussed by Bernhard(1988, 2000) and Corliss and Emerson (1990). We use thesame criteria of identification as those described inFontanier and others (2005). The samples were gentlyshaken for several minutes in order to obtain a homoge-neous mixture. Several weeks after sampling, samples weresieved through screens with 63- and 150-mm openings, andthe sieve residues were stored in 95% ethanol. Foraminiferabelonging to the .150-mm fraction were sorted from wet(about 50% ethanol) samples and stored in Chapman slides.Because of the extremely time consuming character, the 63-to 150-mm fraction was investigated only in the firstcentimeter of sediment. Census data for the livingforaminiferal fauna of both size fractions are presented inTables 1 and 2. Note that we discriminated betweenfossilizing and non-fossilizing agglutinated taxa. All arena-ceous species that were found in the dead assemblages downto the bottom of the core (e.g., Bigenerina nodosaria,Pseudoclavulina crustata, Sigmoilopsis schlumbergeri, Sipho-textularia spp., Textularia spp.) were considered as fossiliz-ing agglutinated taxa. The faunal reference list is depicted inAppendix I. For the living and for the dead assemblages, wedetermined the species richness, which corresponds to thetotal number of observed taxa (excluding undeterminedspecies). We calculated the Shannon index H and theevenness index E (Hayek and Buzas, 1997), as described inMurray (2006). In order to obtain a general idea aboutmicrohabitat patterns, we calculated the average living depth(ALDx; Jorissen and others, 1995) of individual taxa.Following Buzas and others (1993), we identified only threedifferent microhabitat categories: shallow, intermediate anddeep infaunal taxa. For details of calculation of ALD10,readers should consult Fontanier and others (2002). Wecalculated ALD10 only for species with an absoluteabundance higher than 5 individuals per core (Table 1).Isolated specimens separated by more than 1 cm from otherindividuals were not included in the calculation of ALD10. InTable 1, such isolated individuals are presented in italics.

We did not perform geochemical analysis (redoxconditions within the sediment) on in situ material.Therefore, in the discussion, we will use sedimentologicaland faunal observations to estimate the oxygen penetrationdepth (OPD), which is supposed to be an importantecological boundary for living foraminifera.

Incubated Core Dedicated to Foraminiferal Analysis

Onboard the ship, the core dedicated to the incubationwas immediately stored at 14uC (in situ temperature) indarkness. Afterwards, the core was transported to thelaboratory at Angers University in a cool box. In the

laboratory, the core was incubated at 14uC in the dark. Thesalinity (measured with a conductivity meter) was checkedafter 15 days (on May 19, 2003) and because of thesurprisingly high salinity value (62 psu), distilled water wasadded. Thereafter, the salinity was checked at irregularintervals, and if necessary, distilled water was added. Theexperiment stopped on November 2, 2005. Before samplingthe incubated core, pictures of the cores were taken (Fig. 2).On the sediment surface, two zones with different colorscan be distinguished. Two pore-water profiles of oxygenconcentration were measured in the bottom water andalong the sediment column at two different places in thecore. Oxygen profiles were made with an oxygen micro-electrode and a picoampere meter (Unisense, Denmark).Calibration of the electrode signal was performed with air-saturated seawater (100% O2 saturation) obtained by airbubbling during at least one hour and oxygen freeconditions (0% O2 saturation) were obtained deeper in thecore sediment. The calibration was made at the sametemperature and salinity as those of the core. The incubatedcore was sliced and treated in the same way as the in situcore, except for the first half centimeter where threesubsamples were made: one in the orange zone (firstmillimeter), one in the black zone (first millimeter) andone below the first millimeter (from 1–5 mm depth in core).Census data of living foraminiferal fauna for the incubatedcore are presented in Table 1. Note that no living (rose-Bengal-stained) foraminifera were found in the 63- to 150-mm fraction in the first centimeter of sediment (Table 2).

Dead Foraminiferal Faunas in both In Situ andIncubated Cores

We also determined dead foraminiferal assemblages inthe in situ and the incubated cores for the larger sizefraction (.150 mm). As usual (Murray, 2006), whenpossible, we counted at least 250 individuals per sedimentinterval. If necessary, we divided samples into sub-fractionsusing an Otto splitter. Census data are given in Appendi-ces II and III (placed at http://www.cushmanfoundation.org/jfr/index.html under the JFR Article Data RepositoryItem No. JFR DR200803). Branched foraminifera were nottaken into account because it is not reliable to consider onebranched fragment as representative of one individual.

It should be noted that in certain sediment levels wefound some foraminifera with doubtful staining. All theseindividuals, which belong to Bolivina alata, Chilostomellaoolina, Globobulimina pyrula var. pseudospinescens, Hoe-glundina elegans, Hyalinea balthica, Melonis barleeanus,Uvigerina elongatastriata and Uvigerina mediterranea,presented patchy pinkish, reddish to brownish compoundswithin the shell suggesting a slow decay of the remainingprotoplasm. We did not consider these doubtful specimensas alive at the time of sampling, and consequently, theywere integrated into the counts of the dead assemblages.

In Situ Core dedicated to Sedimentological Analyses

The third core collected at Station CAMT-5 wasradiographed using a Scopix system, which consists of anX-ray imaging system combined with image analysissoftware (Migeon and others, 1999). The aim of the X-


FORAMINIFERA FROM SAINT-TROPEZ CANYON 0


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.TABLE 2. Census data of live foraminiferal faunas (63- to 150-mm sizefraction) in both cores collected at Station CAMT-5 (in situ andincubated cores). We investigated only the first centimeter of sediment.Density values are not normalized for sediment volume.

CAMT-5 in situ core (63–150 mm)

Species nameNumber of individuals

(0–1 cm) Abundance (%)

PerforateIndeterminate 3 0.5Anomalinoides sp. 4 0.7Bolivina spathulata 88 16.1Bolivina dilatata 30 5.5Bulimina marginata 3 0.5Cassidulina carinata 4 0.7Cassidulina minuta 27 4.9Cassidulinoides bradyi 30 5.5Chilostomella oolina 1 0.2Coryphostoma sp. 2 0.4Epistominella sp. 16 2.9Fursenkoina complanata 2 0.4Gavelinopsis praegeri 1 0.2Globocassidulina subglobosa 1 0.2Gyroidina orbicularis 1 0.2Gyroidina umbonata 9 1.6Hoeglundina elegans 4 0.7Hyalinea balthica 3 0.5Lenticulina peregrina 1 0.2Melonis barleeanus 105 19.2Polymorphina sp. 1 0.2Rectuvigerina phlegeri 3 0.5Robertinoides sp. 3 0.5Rosalina sp. 1 0.2Rosalina bradyi 2 0.4Sphaeroidina bulloides 1 0.2Trifarina sp. 1 0.2Uvigerina sp. 2 0.4Uvigerina elongatastriata 14 2.6Uvigerina mediterranea 3 0.5Valvulineria bradyana 9 1.6

PorcellaneousIndeterminate 1 0.2Quinqueloculina sp. 4 0.7Spiroloculina spp. 12 2.2Triloculina sp. 1 0.2

Non-fossilizing agglutinatedIndeterminate 12 2.2Agglutinated sp.11 16 2.9Agglutinated sp.44 13 2.4Agglutinated sp.55 20 3.6Agglutinated sp.77 22 4.0Agglutinated sp.99 6 1.1Agglutinated sp.333 22 4.0Adercotryma glomerata 18 3.3Haplophragmoides sp. 4 0.7Lagenammina sp. 3 0.5Psammosphaera spp. 1 0.2Recurvoides spp. 12 2.2Reophax sp. 2 0.4Reophax dentaliniformis 1 0.2Thurammina albicans 3 0.5Total number of foraminifera 548 100Number of taxa 47

CAMT-5 incubated core (63–150 mm)Total number of foraminifera 0 0


with a Malvern Laser Diffraction Particle Sizer (type 2600).This technique was applied to sediment samples of thepreviously radiographed and photographed core. After-wards, the core was sliced into 1-cm-thick sedimentintervals from the sediment-water interface down to20 cm depth. We calculated grain sizes (decile grain sizesD10, Q50 and D90) for all these sediment intervals.

Complementary Investigations

Using the scanning electron microscope Jeol 6301F fromthe Service Commun d’Imageries et d’Analyses Microsco-piques (SCIAM) at Angers University, we obtained digitalphotographs of picked foraminiferal individuals. These arepresented in Plate 1. We used the X-ray microprobe(Oxford ISIS system) equipping the microscope to obtainenergy dispersive X-ray (EDX) spectra and X-ray mappingof different major elements composing the foraminiferaltest and the particles incrusting the test (Plate 1). We focusour attention on sedimentary coatings covering livingRosalina bradyi (Cushman, 1915), which we found abun-dant in the incubated core.

RESULTS

IN SITU CORE

Living Foraminiferal Faunas (.150-mm size fraction)

Census data of the in situ core (72 cm2 surface area) arepresented in Table 1. The vertical distribution of dominant

foraminifera (abundance percentage .5%) in the 10-cm-long core is depicted in Figure 3. The foraminiferal fauna ischaracterized by a species richness of 56 live taxa (excludingundetermined taxa). The Shannon index (H) is 3.08, and theequitability index (E) is 0.37. The foraminiferal density forthe whole 10-cm-long core (normalized to a 100-cm2 surfacearea) is about 830 ind/100 cm2 (,600 individuals for thewhole core without normalization).

Perforate species represent about 71% of total forami-niferal fauna. Dominant taxa are Globobulimina pyrula var.pseudospinescens (14.6%), Chilostomella oolina (10.1%),Uvigerina elongatastriata (7.8%), Bolivina alata (7.0%),Melonis barleeanus (5.3%) and Hyalinea balthica (4.8%).Non-fossilizing agglutinated taxa represent more than 20%of the total faunas. Cribrostomoides sp. is the dominanttaxon of this group, accounting for 14.5% of total liveforaminiferal fauna. Fossilizing agglutinated and porcela-neous species are minor groups. When investigating themicrohabitat distribution of the main taxa, three mainpatterns can be distinguished (Table 1). Cribrostomoides sp.(ALD10 5 0.40 cm) and H. balthica (ALD10 5 0.92 cm) areshallow infaunal taxa. They thrive between the sediment-water interface and 1 cm depth in the sediment. Uvigerinaelongatastriata (ALD10 5 1.20 cm), B. alata (ALD10 5

1.21 cm) and M. barleeanus (ALD10 5 1.41 cm) constituteintermediate infaunal species that mainly occupy thesediment interval between 1 and 2 cm depth. Globobuliminapyrula var. pseudospinescens (ALD10 5 2.68 cm) and C.oolina (ALD10 5 3.33 cm) are typically deep infaunal taxawith average living depth deeper than 2 cm. Both taxa canbe found alive until 8–9 cm depth. Note the presence ofonly two living (rose-Bengal-stained) individuals of Rosa-lina bradyi in the first half centimeter of the core (relativeabundance 5 ,0.3%). One of them was attached todecaying algal remains as an epiphytic organism (Plate 1).

Living Foraminiferal Faunas (63- to 150-mm size fraction)

Census data of the 63- to 150-mm fraction of the in situcore (first centimeter of sediment, 72 cm2 surface area) arepresented in Table 2. The foraminiferal fauna is character-ized by a species richness of 47 living taxa. H is 3.05, and Eis 0.42. The foraminiferal density for the first centimeter ofsediment (normalized for a 100 cm2 surface area) is about760 ind/100 cm2 (,550 individuals for the first centimeterwithout normalization). Perforate taxa represent 68.4% ofthe total fauna whereas the non-fossilizing agglutinatedgroup counts for 28.3% of the foraminiferal community.Dominant taxa are Melonis barleeanus, Bolivina spathulata,Bolivina dilatata and Cassidulinoides bradyi with relativeabundances of 19.2%, 16.1%, 5.5% and 5.5%, respectively.In addition, in the 63- to 150-mm fraction, two living (rose-Bengal-stained) individuals of Rosalina bradyi are found inthe first centimeter of the core (relative abundance 5

,0.4%).

Dead Foraminiferal Assemblages (.150-mm size fraction)

Census data of dead foraminiferal faunas counted in thein situ core (per 72 cm2 surface area) are presented inAppendix II. The vertical distribution of abundant forami-niferal taxa in the 10-cm-long core is depicted in Figure 4a.


FIGURE 2. Photographs of the incubated core taken on November2, 2005 (at the end of incubation). a a general view of the subcore. b aclose-up of the sediment-water interface. The black and white bar onthe side of the core is a centimetric scale. Note the ,1-mm thick orangeand black layer at the sediment-water interface. c a top view of thesediment-water interface with the surficial orange and black layer. Therounded spot marks the spot where oxygen profile 1 was measured.The squared spot marks the spot where oxygen profile 2 was performed.



PLATE 1In situ material: 1 Rosalina bradyi attached on an organic fibrous substrate (dorsal view); 2 R. bradyi (dorsal view). Incubated material: 3 R. bradyi

(dorsal view); 4 R. bradyi, (umbilical view); 5 R. bradyi (lateral view); 6 R. bradyi with incrusting iron-enriched particles (umbilical side); on the right-handside, an EDX spectrum of major elements of the encrusted sediment. 7 X-ray mapping of calcium (Ca) for the umbilical side; 8 X-ray mapping of iron(Fe); 9 X-ray mapping of silicon (Si); 10 X-ray mapping of manganese (Mn). 11 R. bradyi with incrusting manganese-enriched particles (dorsal view); onthe right-hand side, an EDX spectrum of major elements of the encrusted sediment. 12 X-ray mapping of calcium (Ca) for the dorsal side; 13 X-raymapping of manganese (Mn); 14 X-ray mapping of silicon (Si); 15 X-ray mapping of aluminum (Al). Horizontal scale represents 100 mm.


In the total 10-cm-long core, we recorded 91 differenttaxa. This value is higher than the 56 taxa observed in thelive foraminiferal faunas. Perforate foraminifera representabout 90% of the total dead assemblage. Dominant taxa areHyalinea balthica, Bolivina alata, Melonis barleeanus andValvulineria bradyana with average percentages of 15.861.0%, 13.0 61.0%, 8.8 60.8% and 5.6 60.8%, respec-tively (Appendix II; Fig. 4a). Chilostomella oolina, Hoe-glundina elegans, Uvigerina mediterranea, Bulimina aculeata,Cassidulina carinata, Uvigerina peregrina, Planulina arimi-nensis and Cibicides pachydermus present average relativeabundances between 1 and 5%. Globobulimina pyrula var.pseudospinescens and Uvigerina elongatastriata have aver-age percentages of 1.7% and 0.8%, respectively. Porcelane-ous and agglutinated fossilizing groups account for about5% and 3%, respectively. Non-fossilizing agglutinatedforaminifera represent about 2% of the dead faunas.Rosalina bradyi presents a mean relative abundance of 0.660.2% without any perceptible trend in vertical distribu-tion. Dead R. bradyi specimens are found until 10 cmdepth. Not a single specimen is found in the first interval

(0–0.5 cm); in total, we recorded 83 dead individuals for thewhole core. When we correct this number for the split sizesused, this corresponds to ,115 ind/100 cm2.

Sedimentological Data

No clear vertical succession of different sedimentaryfacies is visible in the photograph of the 20-cm-long coresection collected at station CAMT-5 (Fig. 5). There are noclear erosional surfaces and/or turbiditic sequences. Thesediment is homogeneously brownish, with dark browncentimeter-scale patches at the basis of the core. Note thatthe sediment-water interface was slightly compressed by thepolystyrene cap during the transport of the core material toBordeaux University at the end of the sampling campaign.For this reason, the sediment-water interface is slightlyinclined. The X-ray radiograph shows neither clear erosivesurfaces nor graded sediments (Fig. 5). The sediment showsa number of empty and vertical filled burrows detectable allalong the core.

The sediment is mainly composed of muddy silts. TheD10 for the upper 20 cm is between 1.4 and 1.9 mm. The Q50

ranges between 5.8 and 8.3 mm. The D90 ranges between28.1 and 40.2 mm. For these three indices, we can note aslight coarsening-up tendency.

INCUBATED CORE

Salinity in the Water Overlying the Core

Throughout the 2.5 years of incubation, overlying watersalinities varied from ,35 to ,62 psu (Fig. 6). Especially atthe beginning of incubation (May 2003) to September 2004,the water overlying the sediment-water interface suffered anumber of significant salinity increases, with maximumvalues well above 40 psu (,61 psu on May 19, 2003;,62 psu on July 25, 2003). Between November 2004 andNovember 2005, salinity stayed close to a mean value of36 psu. At the end of incubation, salinity was 35.2 psu.

Dissolved Oxygen in Bottom and Pore Waters

At the end of the incubation (November 2005), thesediment-water interface was characterized by orange- andblack-colored particles organized in a ,1-mm-thick sedi-mentary layer (Fig. 2). Two oxygen profiles were performedat the end of the incubation; one through the black-coloredsediment-water interface (profile 1) and a second onethrough the orange-colored interface (profile 2; Fig. 7). Inthe 5 mm of water overlying the sediment-water interface,oxygen concentrations varied between 0.30 and 0.55 ml/lfor both profiles. This denotes strongly hypoxic conditions.In the first millimeter of water immediately above thesediment-water interface, oxygen concentrations fell toundetectable values (,zero) for profile 1 (black sediment)and to 0.03 ml/l for profile 2 (orange sediment). Below thesediment-water interface, for both cases, no more measur-able dissolved oxygen was observed. Since the oxygenconcentration at the sediment-water interface was not zero,the 1-mm-thick orange layer visible in Figure 7 wasprobably not fully anoxic. However, all deeper sedimentsof the whole core presented anoxic conditions.


FIGURE 3. Live foraminiferal distribution (number of individualsof the .150-mm size fraction found in each level, standardized for a50 cm3 volume of sediment) in the in situ core collected at StationCAMT-5. Only taxa with a percentage higher than 5% in at least onedepth interval are presented. Depth axis changes scale below 4 cm.


Live Foraminiferal Faunas (.150-mm and 63- to 150-mmsize fractions)

For the .150-mm size fraction, census data for the liveforaminiferal faunas from the incubated core (per 27 cm2

surface area) are presented in Table 1 (bottom part). Thevertical distribution of the dominant foraminifera in the 10-cm-long core is depicted in Figure 8. The living (rose-Bengal-stained) foraminiferal fauna is characterized by amonospecific population containing only Rosalina bradyi[Discorbis globularis (d’Orbigny) var. bradyi Cushman,1915; Plate 1]. In all, 141 specimens of this perforate specieswere found in the 10-cm-long core, which corresponds toabout 500 ind/100 cm2. EDX spectra and X-ray mappingwere performed on two individuals picked respectively fromthe orange and the black sedimentary layers of theincubated core (Plate 1). Both types of analysis reveal that

orange incrusted particles are mainly composed of ironwhereas black particles contain manganese.

The investigation of the 63- to 150-mm size fraction of thetopmost centimeter of the sediment did not reveal living(rose-Bengal-stained) foraminifera.

Dead Foraminiferal Assemblages (.150-mm size fraction)

Census data of dead foraminiferal faunas for theincubated core (per 27 cm2 surface area) are presented inAppendix III. The vertical distribution of the dominantforaminiferal taxa in the 10-cm-long core is depicted inFigure 4b. For the whole core, we recorded 101 species.Perforate foraminifera represent more than 90% of the totaldead assemblage. Dominant taxa are Hyalinea balthica,Bolivina alata, Melonis barleeanus, Hoeglundina elegans andChilostomella oolina, with respective mean percentages of


FIGURE 4. Foraminiferal thanatocoenoses at Station CAMT-5: a the dead foraminiferal distribution (percentages of dominant taxa of the .150-mm size fraction) in the in situ core; and b dead foraminiferal distribution (percentages of dominant taxa belonging to the .150-mm fraction) in theincubated core. We enlarged the bars related to Rosalina bradyi. Depth axis changes scale below 4 cm.


15.1 61.21%, 12.0 60.7%, 9.3 61.0%, 5.4 60.5% and 5.160.7% for the whole core (Appendix III; Fig. 4b). Valvu-lineria bradyana, Uvigerina mediterranea, Bulimina aculeata,Cassidulina carinata, Planulina ariminensis and Uvigerinaelongatastriata present mean relative abundances between 1and 5%. Globobulimina pyrula var. pseudospinescens andUvigerina elongatastriata account, respectively, for only2.3% and 1.2%. Porcelaneous and agglutinated fossilizinggroups account for about 5% and 3%, respectively. Non-fossilizing agglutinated foraminifera represent less than 2%.Rosalina bradyi presents a mean relative abundance of 1.360.6% for the whole core, with its highest value recorded inthe first half centimeter (,10%). Dead R. bradyi are foundto 10 cm in the sediment. In total, we recorded 109 dead


FIGURE 5. Photograph and X-ray radiograph of a half core collected at Station CAMT-5. Mean grain sizes of the 10th, 50th, and 90th percentilesare indicated along the same half-core.

FIGURE 7. Dissolved oxygen concentration (ml/l) below, at, andabove the sediment-water interface of the incubated core. Profile 1 wasperformed through the black sediment-water interface. Profile 2 wasperformed through the orange sediment-water interface. All measure-ments were performed at the end of the 2.5-year-long incubation, on 2November 2005.

FIGURE 6. Salinity of bottom water overlying the sediment-waterinterface from the incubated core. Measurements were performed inthe laboratory from May 19, 2003 to the November 2, 2005. The firstsalinity value (May 1, 2003) and the horizontal dotted line represent theputative initial value of bottom water in our study area (,38.45 psu;value according to Pierre, 1999).


individuals of R. bradyi in the whole core, corresponding to,400 ind/100 cm2.

DISCUSSION

TAPHONOMIC FEATURES AT STATION CAMT-5

Comparison of the Dead Assemblages in the In Situ andIncubated Cores

Our study allows us to compare the dead faunas of the insitu and incubated cores in the larger size fraction(.150 mm; Fig. 4a, b). The linear regression based on theaverage percentages of the 114 taxa observed in both coresreveals an excellent positive correlation (y 5 0.9693x +0.0283; r 5 0.99, p,0.01). In addition, diversity andequitability indices based on dead faunas from both coresare similar. These results suggest that the dead assemblagefrom the incubated core was obviously not affected bycalcite dissolution related to an eventual acidification ofpore waters during incubation. Such a putative acidification

might have taken place as the consequence of a long-termdegradation of sedimentary organic matter and would havedissolved the more sensitive foraminiferal species (e.g., thinwalled calcitic species such as Globobulimina and Chilosto-mella or the aragonitic Hoeglundina elegans; Mackensenand others, 1990).

Comparison between Live and Dead Assemblages in the InSitu Core

Several taphonomic processes can be enumerated toexplain eventual discrepancies between the in situ thanato-coenoses and the in situ living foraminiferal fauna of the.150-mm size fraction (Mackensen and others, 1990;Mackensen and others, 1993; de Stigter and others, 1999;Jorissen and Wittling, 1999). Globobulimina spp. andChilostomella spp. that dominate the living faunas are lessabundant in the dead foraminiferal assemblages. Threeexplanations can be proposed to explain such differences.(1) Bioturbation and physical compaction may havedamaged their thin tests (Mackensen and others, 1990; deStigter and others, 1999; Jorissen and Wittling, 1999). (2)Test production for these two taxa may be low compared toother dominant taxa living at this station (de Stigter andothers, 1999; Jorissen and Wittling, 1999). (3) In situ livingforaminiferal faunas represent only a snapshot of livingfaunas at the time of the sampling, whereas deadassemblages represent time-averaged assemblages (de Stig-ter and others, 1999; Jorissen and Wittling, 1999). Non-fossilizing agglutinated taxa such as Cribrostomoides spp. orEggerella spp. are absent from the thanatocoenoses pickedin the deeper sediment layers. This probably illustrates theprogressive degradation of test cement after the burial ofdead organisms (e.g., Mackensen and others, 1990; Mack-ensen and others, 1993; de Stigter and others, 1999).Perforate taxa characterized by robust planispiral andtrochospiral tests (Hyalinea balthica, Melonis barleeanus,Valvulineria bradyana) or by flattened tests (Bolivina alata)are well preserved and become, therefore, dominant taxa ofthe dead faunas. The dominance of Hyalinea balthica in thethanatocoenoses may also reflect the opportunistic behav-ior of this taxon, which has been observed to dominateliving faunas from organic enriched canyon environments(S. Hess, written communication, 2007).

Evidence of Downslope Transport

An important question is whether there has been anypost-mortem redeposition of foraminiferal tests fromshallower depths (outer and inner shelf) at our stationclose to the Canyon head. The investigation of the living(rose-Bengal-stained) foraminiferal faunas of the .150-mmsize fraction from two outer shelf stations in the Bay ofFrejus (CAMT-6 and CAMT-7; ,80 m depth; unpublisheddata) revealed a dominance of agglutinated taxa (Textulariaagglutinans, Textularia saggitula, Eggerella scabra, Clavu-lina cylindrica, Ammoscalaria sp.), fair quantities ofperforate shallow infaunal species (Valvulineria bradyana,Pseudoeponides falsobeccarii, Rectuvigerina phlegeri, Mel-onis barleeanus s.l.) and the presence of epiphytic andepilithic perforate species (Asterigerinata mamilla, Cibicideslobatulus, Hanzawaia boueana, Planorbulina mediterranen-


FIGURE 8. Vertical distribution of living and dead (rose-Bengal-stained) Rosalina bradyi: a in the in situ and b the incubated corescollected at Station CAMT-5 (number of individuals belonging to the.150-mm size fraction found in each level, standardized for a 50 cm3

volume of sediment). In the first interval (0–0.5 cm), a distinction hasbeen made between Rosalina bradyi found in the orange ,1-mm-thicklayer (gray bar), those found in the black ,1-mm-thick layer (blackbar) and in the remaining sediment (white bar). Depth axis changesscale below 4 cm.


sis, Gavelinopsis praegeri and Rosalina bradyi). All thesetaxa, which are typical of continental shelf environments,could have been transported into the canyon head byvarious types of downslope transport (suspension orturbidity flow). Together, these taxa constitute a substantialproportion of the .150-mm thanatocoenoses at CAMT-5Station (on average, 11% of in situ dead fauna). Since M.barleeanus s.l. and Valvulineria bradyana are a significantcomponent of the living fauna at our 373-m-deep station(CAMT-5), we did not include them in our estimatedpercentage of potentially allochthonous material. The clearlack of graded sediments and erosional surfaces in our coresare indications that there was no deposition of recentturbidites in our study area. The sediment is, rather,homogeneous and composed of muddy silts. Therefore, itis probable that the neritic taxa encountered in our .150thanatocoenoses were transported downslope by sedimentresuspension events. Summarizing, we think that ourstation CAMT-5 is at present an inactive sedimentaryenvironment that acts as a depocenter for fine-grainedparticles (muddy silt).

IN SITU LIVING FORAMINIFERAL FAUNAS AT

STATION CAMT-5

As explained in the ‘‘material and methods’’ section,authors should keep in mind that our ecological interpre-tations for the in situ and incubated cores are unfortunatelybased on unreplicated material. Therefore, differencesbetween our cores may be due to a putative micro-scalespatial variability that could be enhanced in the sedimen-tological settings suggested above (resuspension-depositionprocesses).

Compared to foraminiferal data from other areas(Jorissen and others, 1994; Hess and others, 2005), therelatively high specific richness in both size fractions at our373-m-depth station, the elevated diversity index, themoderate equitability and the moderate foraminiferaldensity all provide evidence for a community close to anecological equilibrium state. In fact, our foraminiferalfauna differs strongly from the dense, low-diversity, high-dominance faunas that re-colonize active canyons systemsoff New Jersey (Jorissen and others, 1994), the FrenchAtlantic coast (Cap-Breton Canyon; Hess and others, 2005)and the Portuguese coast (Koho and others, 2007). Thissuggests that our canyon environment is quiescent in termsof sedimentary processes and offers a suitable environmentfor more specialized foraminiferal faunas (Alve, 1999).

The .150-mm live foraminiferal fauna from our StationCAMT-5 is characterized by Globobulimina pyrula var.pseudospinescens, Chilostomella oolina, Uvigerina elongatas-triata, Bolivina alata and Melonis barleeanus (Table 1). Allthese taxa do not concentrate at the sediment-waterinterface but occupy intermediate (U. elongatastriata, B.alata, M. barleeanus, Bolivina alata) and deep (C. oolina, G.pyrula var. pseudospinescens) infaunal microhabitats (below1 cm depth). Only Cribrostomoides sp. (mainly Cribrosto-moides subglobosus), the dominant agglutinated taxon,appears in a shallow infaunal microhabitat (first centimeterof sediment). For all these major taxa, numerous ecologicalstudies dealing with living foraminiferal faunas from open

slope and canyon environments have already describedidentical microhabitat patterns (e.g., Corliss, 1985; Mack-ensen and Douglas, 1989; Rathburn and Corliss, 1994;Jorissen and others, 1994; Jorissen and others, 1998;Schmiedl and others, 2000; Fontanier and others, 2002;Licari and others, 2003; Fontanier and others, 2003; 2005;2006; Hess and others, 2005; S. Hess, written communica-tion, 2007; Langezaal and others, 2006). In two papersdealing with the living foraminiferal faunas from Lacaze-Duthiers Canyon in the Gulf of Lions and Cap-FerretCanyon in the Bay of Biscay, Schmiedl and others (2000)and Fontanier and others (2005) recorded similar highabundances of intermediate and deep infaunal taxa(Globobulimina spp., Chilostomella spp., Melonis spp.).These authors suggested that the elevated densities ofinfaunal species may be a direct response to a massive fluxof partially degraded organic matter focusing in thesepassive canyon environments. In Saint-Tropez Canyon, weassume that organic matter derived from various marineshallow-water algae and plants concentrates at our site. Asimple observation of sieves residues (63–150 mm and.150 mm) from the incubated or the in situ core reveals,indeed, high quantities of organic remains (fibrous algaeand plants), which obviously originate from adjacentshelves (Fig. 9). Refractory organic compounds would beslowly introduced into the deeper parts of the sediment,where their slow degradation would induce a rather stableredox gradient and would constitute a food source.Therefore, as predicted by the TROX-model (Jorissen andothers, 1995), the vertical distribution of intermediate anddeep infaunal species at our station would be food- as wellas oxygen-controlled. Moreover, as underlined by Jorissenand others (1994), Hess and others (2005) and S. Hess(written communication, 2007), the development of deepforaminiferal infauna would reflect a state of ecologicequilibrium present in passive canyon environments. Thehigh abundance of Bolivina spathulata and Bolivina dilatatain the 63- to 150-mm size fraction of the first centimeter ofsediment supports these ideas; these taxa have beendocumented as living preferentially in organic-matter-enriched sediment from outer-shelf environments underthe influence of riverine discharge (Langezaal and others,2006; Duchemin and others, 2007).


FIGURE 9. Photographs of the .150-mm sieve residue for the 3.5–4.0 cm depth interval of the in situ core: a the sieve residues in thepicking plate under a stereoscopic microscope—note the filamentousaggregates; b and c show stereoscopic views of sieve residues. Note theabundance of fibrous and filamentous organic remains. They look likedebris of fixed plants and algae.


Fontanier and others (2002; 2005; 2006) showed that inthe Bay of Biscay Melonis barleeanus preferentially lives insediment with dissolved oxygen concentrations between50 mmol/l (,1 ml/l) and 5 mmol/l (,0.1 ml/l), dysoxic tosuboxic conditions, whereas Chilostomella oolina andGlobobulimina spp. systematically show abundance maximaaround the zero oxygen boundary. Although we do nothave direct measurements of redox elements in our in situcore, we can assume that the vertical distribution of thesetaxa is strongly related to pore-water concentration, and,therefore, may provide an accurate estimate of the oxygenpenetration depth. Based on the vertical distribution in the.150-mm size fraction of M. barleeanus and C. oolina (and,to a lesser degree, of Globobulimina pyrula var. pseudospi-nescens) in our in situ core, we estimate the depth of thezero oxygen boundary between 1.0 and 2.0 cm depth. Thetaxa Bolivina alata and Uvigerina elongatastriata occupy anintermediate infaunal microhabitat and present respectivedensities of 42 and 47 individuals per 72 cm2. Bolivina alatawas also described in the Bay of Ajaccio (Corsica, France)as a species dominating the total foraminiferal (dead +living) faunas between 320 and 360 m depth in a canyonsystem (Bizon and Bizon, 1984). De Rijk and others (1999)described high relative frequencies of B. alata in thethanatocoenoses from the Alboran Sea and off Algeria(western Mediterranean Sea) without any depth preferencealong the slope. Because this species is (together withChilostomella spp. and Globobulimina spp.) abundant insediments characterized by a high organic carbon concen-tration, de Rijk and others (1999) suggested that it would befavored by a high sedimentary carbon supply. Therefore, B.alata (and to a lesser degree, U. elongatastriata) may beconsidered as relevant bio-indicators of organic-detritus-enriched sediments. In such settings, they may occupydysoxic microhabitats as intermediate infaunal species.

To summarize, the study of living foraminiferal faunasprovides evidence that our 373-m-depth station in Saint-Tropez canyon is under the influence of organic-matter-enriched sedimentation. High organic inputs in the sedi-ment may sustain intermediate and deep infaunal standingstocks through (1) serving as an important source of foodand (2) maintaining distinct bio-redox zones with asuccession of dysoxic to anoxic sediments. The describedforaminiferal fauna may be considered as a typical, highlydiverse, specialized climax community, which has colonizeda rather quiescent sedimentary environment.

ADVERSE CONDITIONS FOR THE INCUBATED CORE

The core collected at CAMT-5 Station for incubationsuffered important salinity and oxygenation changesthroughout the 2.5 years of incubation. Salinity variedbetween 35 and 62 psu. Bottom and pore water becameseverely hypoxic (close to anoxia) at the end of incubation,in comparison with the well oxygenated conditionsprevailing naturally in Mediterranean Intermediate Water(,4 ml/l). The iron-enriched and manganese-enrichedsediment that constituted the first millimeter of sediment(respectively, the orange and black interfaces) at the end ofincubation indicated that oxygen (and probably nitrate +nitrite) had been totally consumed within the sediment and

that the zero oxygen boundary had migrated upward to thesediment-water interface, where Mn (III, IV) oxides andoxyhydroxides and Fe (III) oxides precipitated. Since wemade only two oxygen measurements, we cannot excludethe presence of re-oxygenation phenomena during theincubation period, especially when we added demineralizedfreshwater to adjust the salinity.

Salinity changes associated with severe oxygen depletion,as observed in our incubated core, are uncommon innatural deep-sea biotopes. Only in deep hypersaline anoxicbasins (DHABs), such as in the Eastern Mediterranean Sea,where salinity may drastically increase to more than300 psu, a comparable setting has been observed (e.g.,Jongsma and others, 1983; De Lange and others, 1990;Wallmann and others, 1997). These high-pressure areasharbor important microbial communities that thrive inorganically enriched and oxygen depleted habitats (e.g.,Erba and others, 1987; Erba, 1991; Ollivier and others,1994; C. Corselli, communication, 1998; van der Wielen andothers, 2005). Foraminifera belonging to the family ofAllogromiidae, bacteriovorous nematodes, and halophilicmollusks proliferate in these environments (Lampadariouand others, 2003). Polychaetes, which filter abundantprokaryotes, and mollusks, which live in symbiosis withchemolithotrophic bacteria, are found in the direct vicinityof such deep-sea hypersaline ‘‘lakes’’ (C. Corselli, commu-nication, 1998). We did not find any Allogromiidae in ourincubated core. It is possible that these soft-shelledforaminifera were not preserved in ethanol. Rosalina bradyi(Cushman, 1915) was the only rose-Bengal-stained (sup-posedly living at the time of sampling) foraminiferal taxonwe found. It appears that all other taxa did not survive theadverse incubation conditions (salinity and oxygen chang-es).

Ecological Behavior of Rosalina bradyi

Venec-Peyre (1984) recorded stained (living) Rosalinabradyi in Posidonia meadows between 10 and 15 m depth inthe Bay of Banyuls-sur-Mer (Gulf of Lions, France). At thiswater depth, salinity ranged between 36.9 and 37.8 psu andtemperature oscillated between 11.6u and 20.8uC. In theAdriatic Sea, Jorissen (1987) recorded R. bradyi between 20and 100 m depth in total assemblages from sandysubstrates, in association with ephiphytic foraminifera suchas Asterigerinata mamilla and Cibicides lobatulus. Thisauthor also found very low frequencies of this taxon from100 to 1000 m depth. Hayward and others (1994) depicted adead foraminiferal association dominated by R. bradyifrom a 0.5-m-depth station characterized by sandy gravel inPort Pegasus of Stewart Island (New Zealand). This specieswas interpreted as a specialized, sessile, epifaunal taxon ableto attach to the rocky substrate. Ferraro and Molisso(2000), who studied foraminiferal thanatocoenoses fromshallow-water volcanic banks in the Gulf of Naples(Tyrrhenian Sea, Italy), described high relative abundancesof R. bradyi (together with the epiphytic Cibicides lobatulus)at a 54-m-deep station. A substrate composed of detritalsand with a vegetation cover may constitute goodenvironment for these attached foraminifera. Vanicek andothers (2000) recorded abundant living (rose-Bengal-



stained) R. bradyi in low-diversity, foraminiferal faunasfrom restricted nearshore environments. R. bradyi wasdominant at a 40-m-deep, open-sea station from theAdriatic Sea (Croatia), on gravelly muddy sand where thetemperature ranged between 13u and 16uC, salinity wasclose to 38.0 psu and oxygen concentration oscillated from4.2 to 6.6 ml/l. As elsewhere, R. bradyi was observed as asessile organism attached to biogenic substrates. However,some R. bradyi were also found in a 1.5-m-deep channelconnecting the open sea to a coastal lagoon. There, salinityranged between 36.0 and 38.0 psu, temperature rangedbetween 9u and 27uC, oxygen concentration varied between5 and 6 ml/l and the sediment was a gravelly sand. Somedead tests were also observed in a lagoon at 40 m depthwhere seasonal anoxia was recorded and where salinitiesand temperature range respectively between 35.5–37.0 psuand 9–17uC (Vanicek and others, 2000). All these observa-tions illustrate that R. bradyi may be considered as anepiphytic and/or epilithic neritic taxon living preferentiallyin inner shelf environments. Heinz and others (2001)performed a laboratory experiment to study the responseof deep-sea foraminifera from a 993-m-depth station fromthe Gulf of Taranto (Mediterranean Sea) to simulatedphytoplankton pulses. The ten-months-long feeding exper-iment induced hypoxic conditions in the aquarium.Surprisingly, at the end of the incubation, Rosalina bradyidominated, suggesting that reproduction had taken place inthe incubation conditions. Heinz and others suggested thatR. bradyi was originally represented in low numbers in thesediment before the beginning of the incubation; it wouldhave become dominant because of its higher tolerance tolow pressure or other incubation conditions.

Observations on the Incubated Core

Figure 8 presents the normalized density of Rosalinabradyi for the dead and living faunas in the in situ andincubated cores for the .150-mm size fraction. Rosalinabradyi is scarce in the in situ core (3 individuals per 100 cm2

in both the .150-mm and the 63- to 150-mm size fractions)in comparison with the incubated core, where its densityincreases to a value of 516 ind/100 cm2 for the .150-mmsize fraction. In contrast, there were no living R. bradyijuveniles (63- to 150-mm size fraction) in the first centimeterof the incubated core. We think that the occurrence of R.bradyi in the in situ core is related to the deposit of algaldetritus with attached specimens in Saint-Tropez Canyon.This phenomenon is depicted in Figure 10, which showsorganic remains (mainly algal fragments) with attachedepiphytic R. bradyi that are transported from adjacentshelves into the canyon. In deep-sea environments (higherpressure, decreasing temperature, limited algal substrate, nolight), R. bradyi would probably not find suitable condi-tions for its reproduction, resulting in very low frequenciesin the dead faunas (Fig. 10).

In contrast, after our 2.5-year-long incubation, the in situliving fauna has been completely replaced by a monospe-cific population of adult Rosalina bradyi (Fig. 10). Thehighly diverse in situ foraminiferal fauna obviously did nottolerate the drastic salinity changes that occurred duringincubation. Such an explanation would be logical since

most dominant deep-sea foraminiferal taxa (e.g., Uvigerinaelongatastriata, Bolivina alata, Melonis barleeanus, Globo-bulimina spp., Chilostomella spp.) can be considered asrather stenohaline. As previously explained, a salinitychange from 35 to 62 psu is uncommon in deep-seaenvironments and can perhaps only be tolerated byAllogromiidae. As a second explanation, the decline of insitu faunas can be also related to the oxygen depletion thatwe recorded at the end of our experiment. However, thisexplanation is less convincing since some of our dominantin situ species are known to be tolerant of hypoxicconditions in in situ and ‘‘culture’’ conditions (e.g., SenGupta and Machain-Castillo, 1993; Bernhard and SenGupta, 1999; Ernst and van der Zwaan, 2004; Geslin andothers, 2004). Only R. bradyi was able to reproduce andgrow throughout our incubation (Figs. 8, 10). According toAlve and Goldstein (2003), propagules of some foraminif-eral species might survive prolonged unfavorable periodsand start growing and reproducing as soon as conditionsimprove. Several questions may be asked with respect to R.bradyi, but will largely remain unanswered: did R. bradyireproduce after salinity returned to marine values(,36 psu) during the experiment; did it reproduce andgrow because of the lack of competition with other taxa; didit reproduce and grow before the oxygen depletion recordedat the end of the experiment; or was R. bradyi really alive atthe end of the incubation? Our data do not allow us toanswer these questions. We can only conclude that R.bradyi was able to reproduce and grow in spite of drasticsalinity changes. Therefore, R. bradyi can be considered as aeuryhaline species. Finally, if we assume that rose-Bengal-stained R. bradyi counted at the end of our incubation werealive, this would mean that R. bradyi is also able to toleratedrastic oxygen depletion (from 4 to 0 ml/l) as was earlierreported by Heinz and others (2001). Consequently, R.bradyi might also be considered as a species tolerant ofoxygen depletion.

CONCLUSION

The putative impact of sedimentary processes on the live(rose-Bengal-stained) foraminiferal faunas and the compo-sition of dead assemblages was investigated at a 373-m-deepcanyon station (CAMT-5 station) in Saint-Tropez Canyon(Bay of Frejus, France).

N The study of dead foraminiferal faunas in both the insitu and the incubated cores (.150-mm size fraction) andthe sedimentological features of a third core reveal thelack of recent turbidite deposition in our study area.However, the substantial occurrence of dead foraminif-eral species from neritic areas and the observation ofhigh amounts of algae and plants fragments in sieveresidues support the assumption that our station ischaracterized (1) by downslope transport of shelfforaminifera and (2) by substantial focusing of organicmatter coming from adjacent shelves.

N The live in situ faunas of the .150-mm size fraction arecharacterized by high abundances of intermediate anddeep infaunal taxa (Uvigerina elongatastriata, Bolivinaalata, Melonis barleeanus, Globobulimina spp. and



Chilostomella oolina). The smaller fraction investigatedfor the first centimeter of the sediment is dominated byM. barleeanus, Bolivina spathulata and Bolivina dilatata.These observations agree with the idea that the fine(muddy silt) sediment at our station is enriched inorganic matter. Specific richness and diversity arerelatively high at this site, suggesting the presence of aspecialized climax community in a rather stable passivecanyon setting. Some living epiphytic individuals belong-ing to neritic taxa are still attached to organic algal debris.

This is the case of Rosalina bradyi (Cushman, 1915),which is probably transported on advected algal detritus.

An incubated core suffered large salinity and oxygenchanges over the 2.5 years of incubation. Salinity variedbetween 35 and 62 psu, whereas oxygen concentration wasalmost zero at the sediment-water interface at the end ofincubation. Only Rosalina bradyi survived these stronglyadverse conditions. Rosalina bradyi was obviously the lastspecies able to reproduce and grow during our incubation,


FIGURE 10. Synthetic schemes showing the vertical distribution of dead and living (rose-Bengal-stained) Rosalina bradyi in the in situ and theincubated cores collected at Station CAMT-5 and the putative redox conditions for both cases. In the in situ settings, shallow infaunal (SI),intermediate infaunal (II) and deep infaunal (DI) groups are also depicted. Note that these groups did not survive in the incubated core. Asteriskmeans that only dead Rosalina bradyi are figured (not other dominant taxa). All distribution profiles are expressed in density (without scale unit).


which suggests that this species is able to tolerate thecombination of large salinity and oxygenation changes.

ACKNOWLEDGMENTS

We would like to thank the crew and the captain of theTethys II, our scientific ship during our oceanographiccruise. We also thank Amaury de Resseguier and PatriceBretel for their precious help during the CARMAcampaign. We thank three anonymous reviewers, JoanBernhard and Charlotte Brunner for their useful commentsabout the submitted and revised version of this paper.

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WALTON, W. R., 1952, Techniques for recognition of living Forami-nifera: Contribution of the Cushman Foundation for Foraminif-eral Research, v. 3, p. 56–60.

Received 2 February 2007Accepted 9 December 2007




APPENDIX I Faunal Reference List.

Species References

Adercotryma glomerata (Brady), 1878 Jones (1994), pl. 34, Figs. 15–18Ammonia beccarii (Linnaeus), 1758 Jorissen (1987), pl. 2, Fig. 5Amphicoryna scalaris (Batsch), 1791 Jones (1994), pl. 63, Figs. 28–31Asterigerinata mamilla (Williamson), 1858 Jorissen (1987), pl. 3, Fig. 1Bigenerina nodosaria d’Orbigny, 1826 Jorissen (1987), pl. 1, Fig. 10Bolivina alata (Seguenza), 1862 Jones (1994), pl. 53, Figs. 2–4Bolivina dilatata Reuss, 1850 Schiebel (1992), pl. 1, Fig. 4aBolivina spathulata (Williamson), 1858 Jorissen (1987), pl. 1, Fig. 5Bolivina striatula Cushman, 1922 Hess (1998), pl.10, Fig. 4Bolivina subaenariensis (Cushman), 1922 Jones (1994), pl. 53, Figs. 10 and 11Bulimina aculeata d’Orbigny, 1826 Jones (1994), pl. 51, Figs. 7–9Bulimina costata d’Orbigny, 1826 Van Leeuwen (1989), pl. 8, Figs. 2 and 3Bulimina inflata Seguenza, 1862 Van Leeuwen (1989), pl. 8, Fig. 4Bulimina marginata d’Orbigny, 1826 Hess (1998), pl. 10, Fig. 7Cancris auriculus (Fichtel and Moll), 1978 Jones (1994), pl. 106, Fig. 4Cassidulina carinata Silvestri, 1896 Phleger and others (1953), pl. 9, Figs. 32–37Cassidulina crassa d’Orbigny, 1839 Jones (1994), pl. 54, Figs. 4 and 5Cassidulina minuta Cushman, 1933 Schiebel (1992), pl. 1, Fig. 4aCassidulinoides bradyi (Norman), 1881 Jones (1994), pl. 54, Figs. 6 and 9Chilostomella oolina Schwager, 1878 Jones (1994), pl. 55, Figs. 12–14Cibicides lobatulus Walker & Jacob, 1798 Jones (1994), pl. 92, Fig. 10Cibicidoides pachydermus (Rzehac), 1886 Jones (1994), pl. 94, Fig. 9Clavulina cylindrica (Cushman), 1922 Jones (1994), pl. 44, Figs. 19–24Cribrostomoides subglobosus (Cushman), 1910 Jones (1994), pl. 34, Figs. 8–10Fursenkoina complanata (Egger), 1893 Jones (1994), pl. 52, Figs 1–3Gavelinopsis praegeri (Heron-Allen and Earland), 1913 Jorissen (1987), pl. 3, Fig. 13Globobulimina affinis d’Orbigny, 1826 Phleger and others (1953), pl. 6, Fig. 32Globobulimina pyrula (d’Orbigny, 1846 ) var. pseudospinescens (Emiliani, 1949) Parker (1958), pl. 2, Figs. 26 and 27Globocassidulina subglobosa (Bradyi), 1881 Jones (1994), pl. 54, Fig.17Glomospira charoides (Jones and Parker), 1860 Timm (1992), pl. 1, Fig. 9Gyroidina altiformis Stewart & Stewart, 1930 Jorissen (1987), pl. 1, Fig. 11Gyroidina orbicularis (sensu Parker, Jones and Brady), 1865 Jones (1994), pl. 115, Fig. 6Gyroidina umbonata (Silvestri), 1898 Parker (1958), pl. 3, Figs. 19 and 20Hanzawaia boueana (d’Orbigny), 1846 Jorissen (1987), pl. 3, Fig. 10Hoeglundina elegans (d’Orbigny), 1826 Phleger and others (1953), pl. 9, Figs. 24 and 25Hyalinea balthica (Schroeter), 1783 Jones (1994), pl. 112, Figs. 1 and 2Lenticulina peregrina (Schwager), 1866 Cushman and McCulloch (1950), pl. 39, Fig. 5Lenticulina vortex (Fichtel and Moll), 1798 Jones (1994), pl.69, Figs. 14–16Melonis barleeanus (Williamson), 1858 Van Leeuwen (1989), pl. 13, Figs. 1 and 2Nonion fabum (Fichtel and Moll), 1978 Jones (1994), pl.109, Figs. 12 and 13Planorbulina mediterranensis d’Orbigny, 1826 Jones (1994), pl. 92, Fig. 1Planodiscorbis rarescens (Brady), 1884 Jones (1994), pl. 90, Figs. 2 and 3Planulina ariminensis d’Orbigny, 1826 Jones (1994), pl. 93, Figs. 10 and 11Pseudoclavulina crustata Cushman, 1936 Jorissen (1987), pl. 1, Fig. 1Pseudoeponides falsobeccarii Rouvillois, 1974 Jorissen (1987), pl. 4, Fig. 3Pullenia quinqueloba (Reuss), 1851 Jones (1994), pl. 84, Figs. 14 and 15Pyrgo depressa (d’Orbigny), 1826 Jones (1994), pl. 2, Figs. 12, 16 and 17Pyrgo elongata (d’Orbigny), 1826 Jones (1994), pl. 2, Fig. 9Pyrgo murrhina (Schwager), 1866 Hess (1998), pl.9, Fig. 1Pyrgo subsphaerica d’Orbigny, 1839 Cushman (1929), pl. 18, Figs 1 and 2Pyrgoella sphaera (d’Orbigny), 1839 Jones (1994), pl. 2, Fig. 4Quinqueloculina seminula (Linne), 1758 Jones (1994), pl. 5, Fig. 6Rectuvigerina phlegeri le Calvez, 1959 Schiebel (1992), pl. 3, Figs. 10a–dReophax bilocularis Flint, 1899 Hess (1998), pl.2, Figs. 13 and 14Reophax dentaliniformis Brady, 1881 Jones (1994), pl. 30, Figs. 21 and 22Reophax guttiferus Brady, 1881 Jones (1994), pl. 31, Figs. 10–15Rosalina bradyi (Cushman), 1915 Jorissen (1987), pl. 3, Fig. 96Sigmoilopsis schlumbergeri Silvestri, 1904 Jones (1994), pl. 8, Figs. 1–4Siphogenerina columellaris (Brady), 1881 Jones (1994), pl. 75, Figs. 15–17Sphaeroidina bulloides Deshayes, 1832 Jones (1994), pl.84, Figs. 1–5, ?6–7Spirophtalmidium acutimargo (Brady), 1884 Jones (1994), pl.10, Fig. 13Stainforthia fusiformis (Williamson), 1858 Schiebel (1992), pl. 2, Fig. 10Textularia agglutinans d’Orbigny, 1839 Jones (1994), pl.43, Fig. 1–3Textularia saggitula Defrance, 1824 Jorissen (1987), pl. 3, Fig. 12Thurammina albicans Brady, 1879 Jones (1994), pl.37, Figs. 2–7Uvigerina elongatastriata (Colom), 1952 Van der Zwaan and others (1986), pl. 6, Figs. 1–8Uvigerina mediterranea Hofker, 1932 Van der Zwaan and others (1986), pl. 5, Figs. 1–7Uvigerina peregrina Cushman, 1923 Van der Zwaan and others (1986), pl. 1, Figs. 1–6Uvigerina proboscidea Schawger, 1866 Van der Zwaan and others (1986), pl. 12, Figs. 1–4Valvulineria bradyana (Fornasini), 1900 Jorissen (1987), pl. 4, Figs. 1 and 2


APPENDIX II

Census data of dead foraminiferal faunas (.150-mm size fraction)in the in situ core collected at Station CAMT-5. Density values arenot normalized for sediment volume and correspond with the numberof individuals observed in the studied fraction of sediment (aftersplitting if necessary). The appendix can be found at http://www.cushmanfoundation.org/jfr/index.html under JFR Data RepositoryItem no. JFR-DR200803.

APPENDIX III

Census data of dead foraminiferal faunas (.150-mm size fraction) inthe incubated core collected at Station CAMT-5. Density values arenot normalized for sediment volume and correspond with the numberof individuals observed in the studied fraction of sediment (aftersplitting if necessary). The appendix can be found at http://www.cushmanfoundation.org/jfr/index.html under JFR Data Reposi-tory Item no. JFR-DR200803.

