MIT Center for International Studies — Ken Buesseler, Woods Hole Oceanographic Institution, Oct 24, 2013 (at 31:30 in): This is a timeline from early on to about 1 year later. This is what we published using Tepco’s data to point out, a couple of features here, you see it going up — this is 50 million Bq/m³. I studied Chernobyl, we’d never seen things above 1,000 Bq/m³ in the ocean. This is why we called it an unprecedented accident. When the health physics people started looking at this they said yeah this of concern. When you’re up here, you might have mortality effects directly on organisms living in the ocean.
Fukushima Wildlife Dose Reconstruction Signals Ecological Consequences (pdf): Seawater concentrations of 131I reached 180 000 Bq L [180 million Bq/m³] on March 30, with an associated 47 000 Bq L [47 million Bq/m³] of 137Cs (measured 330 m offshore) […] At such high dose rates, marked reproductive effects, and even mortality for the most radiosensitive taxa are predicted for all marine wildlife groups whose life history characteristics confine them to the near-field, contaminant release area. […] All estimations were performed under the assumption of no additional marine releases after the end of March. Actual releases of unknown quantity appear to have continued past this date, thus our dose estimates may be low. Our estimates of dose rates are also under-predictions because they are based on measured data for only a few radioisotopes among the suite of possible radionuclides that composed the actual aquatic source terms (e.g., 58Co, 95Zr, 99 Mo, 99 mTc, 105Ru, 106Ru, 129 mTe, 129Te, 132Te, 134Cs, 136Cs, 132I, 140Ba, 140La).