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Four decades of continual fly-ash disposal off Northumberland, U.K.,ended in December 1992. Quantitative sampling of the sediment and the macrobenthos was undertaken in the Summer 1993 over 27 km2 of seabed covering the Blyth Fly-ash Dumpsite and the surrounding area. The offshore portion of the region surveyed bore only traces offly-ash particles, waste being confined to the region shallower than45 m. There, disposals have changed local sedimentary conditions increasing the spatial patchiness of sediment types and altering silt-clay dynamics. Inshore of the dumpsite, substrata affected by long-termtipping have effectively become an artificial reef due to the cementation of the waste. The seabed within the designated dumpsite was still composed of pure fly ash, resulting in macrobenthic densities and species richness markedly lower than control areas, though higher than recorded in a previous survey in 1988. At the dumpsite, between 47 and 66% of the species had only one or two representatives and juveniles made up 47-88% of the individuals. Additional faunal impoverishment occurred where pebbly clinker and aggregates abounded. Nine monthsafter cessation of dumping recovery was essentially dependant on thedecrease in the concentration of the waste and will proceed as the gradual fertilization of the sediments occurs. [ABSTRACT FROM AUTHOR]

A component density feedback represents the effect of change in population size on single demographic rates, whereas an ensemble density feedback captures that effect on the overall growth rate of a population. Given that a population's growth rate is a synthesis of the interplay of all demographic rates operating in a population, we test the hypothesis that the strength of ensemble density feedback must augment with increasing strength of component density feedback, using long-term censuses of population size, fertility, and survival rates of 109 bird and mammal populations (97 species). We found that compensatory and depensatory component feedbacks were common (each detected in approximately 50% of the demographic rates). However, component feedback strength only explained <10% of the variation in ensemble feedback strength. To explain why, we illustrate the different sources of decoupling between component and ensemble feedbacks. We argue that the management of anthropogenic impacts on populations using component feedbacks alone is ill-advised, just as managing on the basis of ensemble feedbacks without a mechanistic understanding of the contributions made by its components and environmental variability can lead to suboptimal decisions.