Detritivore Amphipods - Detritus Interactions and "'P Fluxes in Microcosm
335
Fig. 2a-c. "Sediment only"
condition, animal treatments: a
variations in D-P fluxes; b 3 2 p
distribution among compartments; c sediment concentration factors at different depths
in the sedimentary column.
Animal treatment cumulates
both "low density" and "high
density" treatments
a
2600
" ~
...
E 2550
0
:l:
Q.
C
2500
1
T
T
o
4
12
n. individuals
4 INDIVIDUALS
12 INDIVIDUALS
b
1
0
E
§.
:z:
3
~
0W
c
6
C
and ADs (1691.87 ± 23.00, 1767.03 ± 10.03,
1744.41 ± 8.04 DPM/mg for 0,4, and 12 individuals, respectively) indicated a significant increase
of the sedimentary radiotracer pool. In Fig. 2,
CFs of different layers in the sedimentary column are showed: G. insensibilis activity caused a
decrease in surficial layer (0-3 mm) 32p uptake
and a contemporaneous increase in the layer 3-6
mm. Mechanical turbation of the water-sediment
interface by amphipods may have determined a
p.p
CONCENTRATION FACTOR
10
100
1000
b
-"' -
J
o Defaunated contr 01
Animal treatment
positive variation in 0 2 penetration in the sedimentary column, and a consequent increase in
both radiotracer diffusion rates and in phosphorus binding capacity of superficial sediments.
Animal activity may strongly affect sediments
redox potential and the oxidised surface layer
thickness (Revsbech et al. 1980; Kamp-Nielsen et
al. 1982; Rippey and Jewson 1982), determining
in clayish sediments a positive variation in phosphate binding capacity (Froelich 1988;