Disturbance and Recovery in Intertidal Pools: Maintenance of Mosaic Patterns

Abstract

The species composition of pools in the intertidal zone on the coast of Washington State varies greatly from pool to pool and from time to time. While assemblages change somewhat predictably from the low— to the high—intertidal zone (presumably owing to different stress tolerances of the species), the variance among pools at a given tidal height cannot be ascribed to such physical factors. Some pools at each height are dominated by one species that monopolizes space on the rock or in the water column and modifies the pool environment. Each dominant species, once established, can spread rapidly through a pool (either by vegetative growth or by enhanced recruitment of its conspecifics) and is thus potentially self—perpetuating. When abundant, most dominants appear to prevent potential competitors from settling and surviving by monopolization of resources, abrasion of the substratum, and/or collection of sediment. Six such dominants were identified for Washington tidepools: from low to high pools, these are (1) the surfgrass Phyllospadix scouleri, (2) articulated coralline algae, (3) the mussel Mytilus californianus (exposed shores), (4) the cloning anemone Anthopleura elegantissima (more protected shores), (5) the red alga Rhodomela larix, and (6) the green alga Cladophora sp. Colonial diatoms also appear capable of dominating low pools in the absence of wave disturbance. However, each dominant monopolizes only 20—50% of the pools at any height. Disturbances, defined here as a loss of biomass exceeding 10% cover of a sessile species within 6 mo and caused by extrinsic forces, were observed frequently in regularly censused tidepools. Disturbance agents included waves, excessive heat, wave—driven logs or rocks, and unusual influxes of predators and herbivores. Severe disturbances (those affecting a large proportion of the organisms in a pool) tended to occur in high pools in the summer (due to heat stress) and low pools in the winter (due to wave damage). Overall, a disturbance occurred in every pool studied an average of every 1.6 yr. About half of the 231 observed disturbances affected one of the six dominant species. The frequencies of these disturbances ranged from one every 2—5 yr, and recovery of the species to its original level required 3 mo to > 2 yr. Some species (e.g., Rhodomela) were disturbed frequently bu recovered quickly because of rapid vegetative growth. However if asexual propagation was not possible, such as when the entire population of a species was removed from a pool, the slowness and irregularity of recruitment of sexual propagules greatly impeded recovery. Experimental manipulations involving the total removal of dominant species from pools showed that such large disturbances often require > 3 yr for recovery. The irregularity of planktonic recruitment can be compounded by the presence of herbivores, which can remove most settling organisms from the substratum, or by the absence of other organisms that are necessary for the settlement of a dominant (e.g., seed—attachment sites for Phyllospadi...

Disturbance and subsequent recovery of mid-shore assemblages on seasonal, tropical, rocky shores

“…In contrast to other studies, where localised impacts caused by collision damage are known to have a major structuring effect on intertidal assemblages (e.g. shores where long-lived sessile species dominate the community; Dayton 1971, Dethier 1984, the timing of such events in Hong Kong means that their importance in shaping semi-exposed Hong Kong shores appears to be minimal. Subsequent visits showed that the pattern of recovery following the typhoon was the same as that which occurred after the normal summer die-off the following year (Hutchinson 1999).…”

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

“…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. These include physical characteristics, such as size, depth, substratum heterogeneity, orientation and position along the coastline that can provide different microhabitats to different pools (Femino andMathieson 1980, Metaxas et al 1994), and biotic factors, such as grazing (Chapman 1990, Benedetti-Cecchi andCinelli 1995) and competition (Van Tamelen 1996, BenedettiCecchi 2000, often interacting in complex ways (Astles 1993, Dethier 1984, Masterson et al 2008. This complexity could be responsible for the lower number of studies on patterns of distribution and abundance of assemblages in pools compared with other rocky habitats.…”

Colonisation of newly-opened habitat by a pioneer species, Alvinella pompejana (Polychaeta: Alvinellidae), at East Pacific Rise vent sites

“…proximity of a source of propagules, i.e. reproductive adults) and/or seasonality in reproduction, and therefore be much more variable over the year (Dethier 1984, Levin 1984, Blanchette 1996. To evaluate whether colonisation might have been achieved by recruitment of larvae or by immigration of juveniles or adults, data on the size at recruitment and on growth rates are necessary (Shull 1997).…”