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Fig. 3. Average macrobenthos abundance with confidence limit (fg .95 S.E.) vs sediment depth. ae eee ee ee eee ee ee EE EE EEE EE eee eee The macrobenthos abundance is estimated at 4.6 + 2.0 individuals dm~? (calculated over 27 cm depth), and the density is 13.1 + 5.6 individuals dm~* (mean + fy 95 S.E.,n = 25). The distribution of macrobenthos indicates that the macrobenthos is encountered as deep as 18 cm in the sediment, but 85% of individuals are concentrated in the uppermost 3 cm (Fig. 3). Family abundance in each sediment level and their feeding modes are given in Table 1. Polychetes dominate the community (43.0% of individuals) with many Paraoni- dae. Fauveliopsidae and Capitellidae occur at ali depth intervals to 18 cm. Mollusca reach 32% of the community with a high representation of Chaetodermatidea. Sipuncula and Crustacea represent, respectively, 16.0% and 8% of the community. Figure 4 shows percentages of the different trophic groups. This classification indicates that 81.4% of the

Figure 3 Average macrobenthos abundance with confidence limit (fg .95 S.E.) vs sediment depth. ae eee ee ee eee ee ee EE EE EEE EE eee eee The macrobenthos abundance is estimated at 4.6 + 2.0 individuals dm~? (calculated over 27 cm depth), and the density is 13.1 + 5.6 individuals dm~* (mean + fy 95 S.E.,n = 25). The distribution of macrobenthos indicates that the macrobenthos is encountered as deep as 18 cm in the sediment, but 85% of individuals are concentrated in the uppermost 3 cm (Fig. 3). Family abundance in each sediment level and their feeding modes are given in Table 1. Polychetes dominate the community (43.0% of individuals) with many Paraoni- dae. Fauveliopsidae and Capitellidae occur at ali depth intervals to 18 cm. Mollusca reach 32% of the community with a high representation of Chaetodermatidea. Sipuncula and Crustacea represent, respectively, 16.0% and 8% of the community. Figure 4 shows percentages of the different trophic groups. This classification indicates that 81.4% of the

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Fig. 1. Location of the investigated zone in Toulon Canyon (northwestern Mediterranean Sea). —to define the major aspect of bioturbation and identify the organisms responsible for the dominant processes; —to establish the relationships between macro and megabenthic fauna in an oligotro-
Fig. 1. Location of the investigated zone in Toulon Canyon (northwestern Mediterranean Sea). —to define the major aspect of bioturbation and identify the organisms responsible for the dominant processes; —to establish the relationships between macro and megabenthic fauna in an oligotro-
Fig. 2. Average porosity and LOT (loss on ignition) with confidence limits (f9.95 S.E.) as a function of sediment depth.
Fig. 2. Average porosity and LOT (loss on ignition) with confidence limits (f9.95 S.E.) as a function of sediment depth.
Table 1. Average abundance of macrobenthic families in the different levels of the RM cores (number of individuals per level) and total abundance and dominance of each family (number of individuals per core). Feeding modes (Coull, 1977; Fauchald and Jumars, 1979; George and George, 1980; Jumars et al., 1990) are formulated with codes as: DS: surface deposit feeders; DSS: subsurface deposit feeders, C: carnivores, S: suspensivores; H: herbivores, U: undeterminate mode
Table 1. Average abundance of macrobenthic families in the different levels of the RM cores (number of individuals per level) and total abundance and dominance of each family (number of individuals per core). Feeding modes (Coull, 1977; Fauchald and Jumars, 1979; George and George, 1980; Jumars et al., 1990) are formulated with codes as: DS: surface deposit feeders; DSS: subsurface deposit feeders, C: carnivores, S: suspensivores; H: herbivores, U: undeterminate mode
X-radiography of the sediment shows numerous turbidite structures at various depths within the sediment column. Only one of the X-rayed cores contained a distinctive burrow. This biogenic structure is a horizontal tube of 1 cm diameter transecting the core between 7 and 9 cm depth, and it may be related to planolites (Wetzel, 1983).
X-radiography of the sediment shows numerous turbidite structures at various depths within the sediment column. Only one of the X-rayed cores contained a distinctive burrow. This biogenic structure is a horizontal tube of 1 cm diameter transecting the core between 7 and 9 cm depth, and it may be related to planolites (Wetzel, 1983).
eee eee ee eee ee eee ee ee ONO NE EE NE OO NN ANE NA EO | es ? Study of photographs of the sea floor permits identification of various types of biogenic features at the sediment surface (Fig. 5). One can observe groups of usually six, nine or 12 holes, simple large conical holes or craters, circular depressions with a plane bottom, large mounds with an apical vent, and small mounds with a vent on the side. Average densities of these structures are given in Table 2. The most frequent type of structure is the group of holes which has an average density of 1.2 + 0.7 structures m~*. Sampling wit box corer was carried out on a group of six holes. Analysis of macrobenthic c h the Oceanic ontent of this core resulted in 12 Polychaetes, two Bivalva, 17 Sipuncula, and 1 Crustacean individuals. This macrofauna corresponds to a density of 14.2 individuals dm™*. All t he organisms
eee eee ee eee ee eee ee ee ONO NE EE NE OO NN ANE NA EO | es ? Study of photographs of the sea floor permits identification of various types of biogenic features at the sediment surface (Fig. 5). One can observe groups of usually six, nine or 12 holes, simple large conical holes or craters, circular depressions with a plane bottom, large mounds with an apical vent, and small mounds with a vent on the side. Average densities of these structures are given in Table 2. The most frequent type of structure is the group of holes which has an average density of 1.2 + 0.7 structures m~*. Sampling wit box corer was carried out on a group of six holes. Analysis of macrobenthic c h the Oceanic ontent of this core resulted in 12 Polychaetes, two Bivalva, 17 Sipuncula, and 1 Crustacean individuals. This macrofauna corresponds to a density of 14.2 individuals dm™*. All t he organisms
[able 2. Average density (average + fg ys S.E.) of biogenic structures counted at the sediment surface in Toulon Canyon encountered are very small except the Crustacean, identified as Calocaris macandreae which was larger than the others.
[able 2. Average density (average + fg ys S.E.) of biogenic structures counted at the sediment surface in Toulon Canyon encountered are very small except the Crustacean, identified as Calocaris macandreae which was larger than the others.
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