Tóm tắt
The 1982–1983 El Niño generated a strong signal which diminished poleward. Although water mass properties were clearly influenced at 48°N, no effects were identified on a rocky intertidal community which could unambiguously be attributed to El Niño. The analyses included long term studies of the upper limits to the distribution of a red alga (7 years) and two species of mussels (14 years). No effect was identified on the recruitment, mortality, or growth of a brown alga, Postelsia. Major sea urchin recruitments have occurred on the Washington outer coast four times in the last 22 years, only two of which have been El Niño events, although all were in years of warmer than average water. Major (extreme) episodes of mussel bed disruption occurred immediately after the latest El Niño, but also during a cold water winter (1975–1976). The data suggest that it is difficult to distinguish the influence of even a potentially strong perturbation against a biologically variable background when a long term data base exists.
