In marine sediments, many of the processes associated with high post-s
ettlement mortality of infauna have similar effects on the sediment su
rface. In most cases the original sediment surface is either removed,
buried, or mixed with subsurface sediment. The experiments reported he
re tested the ability of new juvenile infauna to discriminate between
undisturbed and recently disturbed sediment surfaces (i.e., subsurface
sediment exposed). Recently settled juveniles of two polychaete speci
es (Nereis vexillosa and Arenicola cristata) and one bivalve species (
Mercenaria mercenaria) were exposed to simulated erosional and mixing
events as well as to fresh feces, burrow tailings, and feeding tracks.
Where the disturbance buried or removed several millimeters of the se
diment surface, the time to initiate burrowing or the percentage of in
dividuals failing to burrow increased significantly over times and per
centages for juveniles on undisturbed surfaces. In all cases the resul
ts were consistent with the hypothesis that new juveniles reject (or a
re significantly slower to burrow into) disturbed sediment surfaces, i
f the disturbance is less than several hours old. For example, 51% of
nereid juveniles did not burrow when placed on subsurface sediments, w
hereas 100% burrowed into surface sediments; their average burrowing t
ime on surface sediments was 29.3 s compared with 109.7 s on fecal mou
nds of arenicolid polychaetes or 106.1 s on burrow tailings of thalass
inid crustaceans. Individuals that did not indicate acceptance of a se
diment surface by burrowing were all rapidly eroded from the surface i
n the presence of flow. Erosion of nonburrowing individuals occurred w
ithin 90 s of initiation of flow. Burrowing individuals were not erode
d. The decision as to the acceptability of a sediment was made within
30 s. These data imply that the new juveniles are utilizing cues assoc
iated with a process, the disturbance of surface sediments, in additio
n to the species-specific cues described elsewhere.