Radiation is not "wreaking havoc on ecosystems."
Level in the Pacific off the West Coast trackable to Fukushima (via Cesium-137 analysis) are about 1 Becquerel per cubic meter of ocean water (a Becquerel refers to one nuclear decay per second).
More perspective at, from all places, the Washington Post.
As a sidebar, the actual radiation-related health results for Fukushima were calculated by the WHO based on the conservative "linear no threshold" model (LNT). The Summary section on page 92 is recommended.