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In order to assess the possible environmental impact of oily cuttings discharged during oil exploration activities, we studied the benthic foraminiferal faunas in a five-station, 4-km-long sampling transect around a cuttings disposal site at about 670 m depth offshore Angola (W Africa), where drilling activities started 1.5 years before sampling. Living (Rose Bengal stained) and dead foraminiferal faunas were sampled in March 2006. The faunal patterns mirror the spatial distribution of hydrocarbons, which are dispersed into a southeastern direction. Four different areas can be distinguished on the basis of the investigated faunal parameters (density, diversity and species composition of the living fauna, and comparison with subrecent dead faunas). The fauna at station S31, 300 m SE of the oil cuttings disposal site, appears to be clearly impacted: the faunal density and diversity are maximal, but evenness is minimal. Taxa sensitive to organic enrichment, such as Uvigerina peregrina, Cancris auriculus and Cribrostomoides subglobosus, have largely disappeared, whereas the low-oxygen-resistant taxon Chilostomella oolina and opportunistic buliminids and bolivinids attain relatively high densities. At station S32, 500 m SE of the disposal site, environmental impact is still perceptible. The faunal density is slightly increased, and U. peregrina, apparently the most sensitive species, is still almost absent. The faunas found at 1 and 1.8 km SE of the disposal site are apparently no longer impacted by the drill mud disposal. Faunal density and diversity are low, and the faunal composition is typical for a mesotrophic to eutrophic upper slope environment. Finally, Station S35, 2 km NW of the disposal site, contains an intermediate fauna, where both the lowoxygen-resistant C. oolina and the more sensitive taxa (U. peregrina, C. auriculus and C. subglobosus) are present. All taxa live close to the sediment-water interface here, indicating a reduced oxygen penetration into the sediment. Since the hydrocarbon concentration is low at this station, it appears that the faunal characteristics are the consequence of a slightly different environmental setting, and not due to a contamination with drill cuttings. Our data underline the large potential of benthic foraminifera as bio-indicators of anthropogenic enrichment in open marine settings, such as caused by the disposal of oily drill cuttings. The foraminiferal faunas react essentially by a density increase of a number of tolerant and/or opportunistic taxa, and a progressive disappearance of more sensitive taxa in the most impacted area. Rather surprisingly, large-sized taxa appear to be more sensitive than small-sized foraminiferal taxa.

The impact of sedimentary processes on the live (rose-Bengal-stained) foraminiferal faunas and on the composition of dead assemblages was investigated at a 373-m-deep station in Saint-Tropez Canyon (Bay of Fréjus, France). For the .150-mm fraction, biocoenoses and thanatocoenoses were investigated in two 10-cm-long cores collected with a classical Barnett multi-corer. In the 63-to 150-mm size fraction, living faunas were investigated in the first centimeter of the sediment. The first core was fixed with ethanol and rose-Bengal at the time of the sampling (the in situ core) whereas the second core was stored in a culture room during a 2.5year-long incubation before its fauna was investigated.Both cores present similar thanatocoenoses (.150-mm size fraction) that are substantially contaminated by neritic foraminifera presumably transported from adjacent shelves. The sedimentological analysis of a third core reveals neither graded sediments nor erosional surfaces. Abundant organic remains are detected downcore in the muddy silt sediment. All these observations preclude the idea of deposition by a recent turbidite. Therefore, our canyon environment seems to behave at present as a depocenter for a rather continuous flux of fine sediment and resuspended organic matter originating from shallower areas.The living in situ faunas in the 63-to 150-mm and .150-mm size fractions are quite diverse with a moderate evenness. In the .150-mm size fraction, the high abundance of intermediate and deep infaunal taxa (Uvigerina elongatastriata, Bolivina alata, Melonis barleeanus, Globobulimina spp. and Chilostomella oolina) underlines the importance of organic matter focusing (and the related redox conditions) in this submarine canyon environment. The dominance of M. barleeanus and bolivinids in the 63-to 150-mm size fraction confirms the eutrophic aspect of our study area.Because of logistical problems, the incubated core suffered important salinity changes throughout the 2.5 years of incubation. Salinity ranged between 35 and 62 psu. Oxygen concentration was almost zero at the sediment-water interface at the end of incubation. In the larger size fraction (.150 mm), only one taxon, Rosalina bradyi (Cushman, 1915), survived these adverse experimental conditions. Its density (516 ind/100 cm 2 ) is two orders of magnitude higher than that of the in situ core (3 ind/100 cm 2 ). No living foraminifera were found in the first centimeter of the 63-to 150-mm size fraction. Rosalina bradyi was obviously the last species able to reproduce and grow in the incubated core. Our results show that this taxon is capable of tolerating extreme salinity changes.

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