Data visualization is all the rage these days, but there’s nothing quite like getting the story from points on a graph. In today’s issue of Science, Ken Buesseler of the Woods Hole Oceanographic Institution in Massachusetts provides plots of radioactivity in fish around the ruined Fukushima Daiichi nuclear plant that do just that (click image to enlarge).
The Y axis is a logarithmic scale of radioactive caesium in becquerels per kilogram (Bq/Kg). The dashed line isn’t a trend line, it’s the Japanese government’s limit on what they consider safe levels of radioactivity in seafood (100 Bq/Kg). This data is for demersal, or bottom-dwelling fish.
There’s a couple of things the graph tell us: first, there is enough radioactivity in the fish in Fukushima prefecture to seriously hinder commercial fishing. Second, the radioactivity doesn’t seem to have declined in the first year after the accident.
Buesseler speculates that this is because much of the radioactivity has settled into the sediment around the plant. Caesium 137 has a half life of 30 years or more, and this could mean that fish from the region will be inedible for decades to come.
The plots also raise some worrying questions: if caesium is continuing to enter the ecosystem and will enter it for some years to come, how might this affect things in the long term? What will happen as contaminated fish swim outside the area around the plant? Buesseler believes that understanding the patterns of contamination on the sea floor, and how it enters and leaves the food chain, will be crucial to managing local fish stocks in the coming years.