Spatial and temporal variability of macrobenthic communities in tidepools on a rocky shore in Nova Scotia, Canada

Abstract

Spatial and temporal patterns in the distribution and abundance of macroalgae and macrofauna were measured in 4 pools in each of 3 intertidal zones (mid, high and splash) on a rocky shore near Halifax, Nova Scotia, Canada. Sheets, filamentous, coarsely branched, thick leathery, jointed calcareous, and crustose forms were the most abundant macroalgal functional groups, and mussels, l~ttorinid snails and whelks were the most abundant macroinvertebrates in the pools. Percentage cover of the late-successional macroalgal forms, such as thick leathery and crustose forms, was greatest in the mid pools where environmental fluctuations are smaller and more predictable. Percentage cover of the more opportunistic forms, such as sheets and filamentous algae, was variable among pools in all zones, whereas percentage cover of the other functional forms was most variable among mid pools on most sampling dates. Mussels and whelks were more abundant in mid pools, whereas littonnes were more abundant in the high pools. Macrofaunal abundance also was variable among pools within most zones on most sampling dates. Multiple regressions showed that grazer density, nutrient regime and physical characteristics of the tidepools can consistently explain the variability in percentage cover of late-successional macroalgal functional forms, but not of the more opportunistic forms. The horizontal spatial variability in percentage cover of macroalgae may result from differential recruitment of opportunistic forms, and/or differences in the physical characteristics of the pools which affect slow-growing, late-successional forms. The Shannon D~versity Index for the macroalgal and the macrofaunal assemblages was greatest in mid pools, suggesting that a smaller number of macroalgal and macroinvertebrate species can survive in the higher pools where conditions are harsher. Cluster analyses showed that the macroalgal assemblages were mostly similar among mid pools, and that macrofaunal assemblages of mid pools were similar to high pools, but not splash pools. Our study shows that macrobenthic community structure in tidepools does not vary consistently with the period of tidal isolation and there is large variability among pools within intertidal zones.

Benthic assemblages of rock pools in northern Portugal: seasonal and between-pool variability

“…Finally, although unable to mask differences between seasons, present findings indicated a large variability between pools in the structure of assemblages, analogously to previous studies (Metaxas et al 1994, Araújo et al 2006. Such variability is often attributed to physical characteristics of each pool.…”

“…Such variability is often attributed to physical characteristics of each pool. Here, however, spatial and temporal differences were unlikely to be affected by physical traits that are usually considered as particularly important, such as size, depth and position (Femino and Mathieson 1980, Wolfe and Harlin 1988b, Metaxas et al 1994, Araújo et al 2006, as these were comparable between pools assigned to each date and season. Other single or interacting abiotic and biological factors, such as the heterogeneity of the substratum, grazing and patchy algal recruitment and colonization, could thus make a larger contribution to driving the variability of assemblages between pools (Menge et al 1983, Reed et al 1988, Benedetti-Cecchi and Cinelli 1992.…”

“…On the other hand, they experience greater fluctuations of physical variables, including temperature, salinity and pH, compared with subtidal habitats, with the occurrence of very harsh conditions particularly at higher levels on the shore (Metaxas and Scheibling 1993). These factors have been invoked to explain the dominance of different groups of macroalgae in pools located at different tidal levels (Dethier 1982, Wolfe and Harlin 1988a, Kooistra et al 1989, Metaxas et al 1994) and the reduction of species diversity at increasing heights (Femino and Mathieson 1980, Huggett and Griffiths 1986, Wolfe and Harlin 1988b, Kooistra et al 1989. Moreover, assemblages are highly variable between pools located at the same height on the shore Scheibling 1993, Metaxas et al 1994), probably due to combined abiotic and biological factors.…”

“…Tide pools have been reported to be very variable systems at different locations (Metaxas and Scheibling 1993, Metaxas et al 1994, Underwood and Skilleter 1996, Van Tamelen 1996, Thompson et al 2002. Tide pools provide peculiar environmental conditions compared with the surrounding rocky habitats, as they are not subject to the tidal cycles of submersion and desiccation of nearby emergent rocky areas.…”

Habitat heterogeneity, sea urchin grazing and the distribution of algae in littoral rock pools on the west coast of Italy (western Mediterranean)

“…The hypothesis underlying this prediction was contrasted with the alternative explanation of a negative effect of the crevices independent of the presence of sea urchins. Both hypotheses were tested against the background of natural variability in species distribution and abundance existing between pools (see Astles 1993, Metaxas & Scheibling 1993, Metaxas et al 1994. This procedure allowed a rigorous assessment of the ecological relevance of these hypotheses across the study site.…”