This week's In The News addresses recent findings (published in the October 16, 1998 issue of Science) that killer whale predation on sea otters in the North Pacific has "created an ecological chain reaction in nearshore ecosystems." Such ecological chain reactions refer to the disruption of the complex balance between predator and prey species. Killer whales, which traditionally fed on the (now scarce) Steller sea lions and harbor seals, have recently shifted their diet to sea otters. The resulting decline in sea otters has, in turn, led to an increase in sea urchins (sea otter prey), which in turn have deforested many kelp (seaweed) beds in the nearshore marine community. Although killer whales are playing a critical role in the current disruption, this chain of interactions "was probably initiated by anthropogenic changes in the offshore oceanic ecosystem" -- namely, the region's burgeoning fisheries, higher ocean temperatures, and the depletion of baleen whales. Similar "trophic cascades" have been well documented for lakes and in other systems (e.g. Snow Geese in the Arctic), but this research provides a new example of a disrupted food web that may reach a wider audience -- as it involves several highly charismatic vertebrates. The nine resources discussed describe the recent scientific findings, provide background information on food webs, and offer several resources for understanding ecological (trophic) chain reactions.