Temporal and spatial variation in the early recruitment of fucoid algae: the role of microhabitats and temporal scales

Abstract

The recruitment of a multi-species assemblage of fucoid algae, Ascophyllum nodosum (L.) Le Jolis, Fucus vesiculosus L., and F. distichus L. ssp. edentatus (Pyl.) Powell, onto artificial sub- strata over different temporal and spatial scales was examined on a semi-exposed rocky shore in Quebec, Canada. Measurements were taken at daily (1 d), fortnightly (15 d), and monthly (30 d) peri- ods in 3 microhabitats (exposed rock surfaces, under adult fucoids, and in tide pools) from July through September in 3 consecutive years (1998 to 2000). Recruitment was spatially and temporally variable among months and years with much less recruitment in 1998. Recruitment was consistently lowest in September. The density of reproductive adults did not generally affect the rate of recruit- ment, but the rate of recruitment was negatively correlated with wind speed, a possible indicator of wave action. Among microhabitats, the recruitment was over 10 to 50 times greater under the canopy relative to exposed surfaces and tide pools. Mortality of outplanted embryos was only slightly higher outside the canopy, which suggests that it is limited dispersal and not differential survival that leads to high numbers of recruits under the canopy. There were, however, no differences in the numbers of recruits accumulating from 1 to 30 d, suggesting that overall post-settlement mortality rates are extremely high.