Direct experimental manipulation of intertidal organisms accelerated in the 1960s with the groundbreaking work of J. H. Connell and R. T. Paine. Connell manipulated the presence of two species of barnacles in Scotland by selectively removing individuals from small tiles fashioned from the sandstone rock from the shore. He showed that the lower limit of the high intertidal species Chthamalus stellatus was set by competition with the mid zone species Balanus (now Semibalanus) balanoides and that the upper limit of S. balanoides was set by physical factors. Paine removed the predatory seastar Pisaster ochraceus from an area of the intertidal shore in Washington and showed that Pisaster was responsible for controlling mussels,
which are successful competitors for space and dominate the intertidal shore in the absence of Pisaster. These early investigations provided a framework for the rapid growth of experimental studies that characterized the field in recent decades (Figure 4).
In general, the observation and experimental manipulations of mobile consumers and their prey has often revealed predation by mobile consumers as an important factor that contributes to the structure of rocky intertidal assemblages. Consumers have been repeatedly shown to be prey species- and prey size-selective, while algal grazing consumers can inadvertently remove newly settled animals and algae as well as their intended prey.
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