We present a model of community regulation that incorporates the effects of abiotic disturbance, predation, competition, and recruitment density. We assume that mobile organisms (i.e., consumers) are more strongly affected by environmental stress than are sessile organisms and that food-web complexity decreases with increasing stress. The model makes three predictions under conditions of high recruitment. First, in stressful environments, consumers have no effect because they are absent or inactive, and competition for space is prevented. Both mobile and sessile organisms are regulated directly by environmental stress. Second, in moderate environments, consumers are still ineffective, but sessile organisms are less affected by stress and frequently attain high densities, leading to competition for space. Finally, in benign environments, consumers prevent competition for space unless the prey can escape a predation bottleneck and reach a high abundance. A reduction in recruitment density reduces the import...

Community regulation: variation in disturbance, competition, and predation in relation to environmental stress and recruitment

Predation, Competition, and Prey Communities: A Review of Field Experiments

Organisms living in the marine rocky intertidal zone compete for space This, together with predation, physical disruption, and differing species tolerances to physiological stress, explains the structure of the ecological communities at some sites At other sites the supply of larvae is limiting, and events in the offshore waters, such as wind-driven upwelling, explain the composition of intertidal communities Whether the community ecology at a site is governed by adult-adult interactions within the site, or by limitations to the supply of larvae reaching the site, is determined by the regional pattern of circulation in the coastal waters Models combining larval circulation with adult interactions can potentially forecast population fluctuations These findings illustrate how processes in different ecological habitats are coupled

https://science.sciencemag.org/content/sci/241/4872/1460.full.pdf

Recruitment dynamics in complex life cycles

The consequences of variation in initial settlement vs. post-settlement mortality in rocky intertidal communities

Many marine invertebrates have a planktonic stage of their life history during which widespread dispersal and much mortality occur. The numbers surviving to recruit into habitats occupied by adults are therefore very variable in time and space. Models for the structure and dynamics of benthic assemblages tend to focus on processes causing death - often assuming consistent arrivals of recruits. Supply-side ecology is a newly fashionable term to describe recent interest in the long-realized consequences of variations in recruitment. Such variations have important influences on theory and empirical research in these assemblages.

Supply-side ecology and benthic marine assemblages

At mid-shore levels on rocky shores in New South Wales, grazing gastropods are the dominant species in sheltered areas. Where wave-exposure is great, barnacles occupy most of the space. At intermediate levels of waveexposure, there are mixtures of grazing gastropods and barnacles, and the patterns of occupancy of space, and structure of the community change from time to time. The major species found in these areas are the coronuloid barnacle Tesseropora rosea, the patellid limpet Cellana tramoserica, the smaller acmaeid limpet, Patelloida latistrigata, which is mostly confined amongst barnacles, and the predatory whelk Morula marginalba. The roles of each of these species in determining the structure and persistence of intertidal communities were investigated by experimental manipulations of the densities of each of these organisms. In most experiments, a range of densities of limpets and barnacles was used, rather than the simple removal of all of one species.

E. J. Denley

Papers

Experimental analyses of the structure and dynamics of mid-shore rocky intertidal communities in New South Wales.

Experiments on factors influencing settlement, survival, and growth of two species of barnacles in new south wales