T. Balch et Re. Scheibling, Temporal and spatial variability in settlement and recruitment of echinoderms in kelp beds and barrens in Nova Scotia, MAR ECOL-PR, 205, 2000, pp. 139-154
Settlement and recruitment of echinoderms were measured in 2 adjacent habit
ats: a kelp bed (Laminaria longicruris) and an echinoid (Strongylocentrotus
droebachiensis)-dominated barren ground at each of 2 sites in the rocky su
btidal zone (5 to 10 m depth) off Nova Scotia. Settlement was measured usin
g artificial collectors made of 0.05 m(2) panels of plastic turf that were
deployed 0.2 m (low) and 2.3 m (high) above the bottom in each habitat, and
sampled bi-weekly from June to November 1992 to 1994. Distinct settlement
pulses of ophiuroids (Ophiopholis aculeata and Ophiura spp.), asteroids (As
terias spp.) and an echinoid (S. droebachiensis) occurred between July and
September of each year at both sites. Timing of settlement differed consist
ently among species in relation to differences in timing of spawning and la
rval development. The magnitude of each pulse varied between years and spec
ies, and the year of maximum settlement differed between species, suggestin
g that species-specific processes regulate settlement rather than general e
nvironmental conditions. Settlement of all species was greater at the more
protected site, but between-habitat patterns were not consistent among spec
ies. Asteroids settled in greater numbers in and above kelp beds, whereas o
phiuroids showed a trend toward greater settlement in the barrens. The echi
noid S. droebachiensis also tended to settle more in barrens, although the
difference was not statistically significant. This suggests that kelp beds
do not exhibit a consistent or strong effect on settlement. Sampling settle
ment concurrently at different frequencies (3 to 48 d) gave different estim
ates of settlement, indicating a need for assessment of sampling artifacts
(e.g, changes in collector quality, post-settlement mortality or migration)
that can occur over longer deployment intervals. For most species sampled,
settlement predicted recruit density in natural populations the following
year. However, the strength of the relationship varied between species, pro
bably because of differing postsettlement processes.