Cancer-Causing Arsenic Is Building Up in the Rice

"The more root growth, the more carbon in the soil, which can be a source of food for soil bacteria that multiply under warming temperatures. When soil in a rice paddy is waterlogged, oxygen gets depleted, causing the soil bacteria to rely further on arsenic to generate energy. The end result is more arsenic building up in the rice paddy, and more roots to take it up to the developing grain."

It is said that the bacteria rely further on arsenic to generate energy, where I understand "rely on" as "consume". So how would this lead to a build up of arsenic? If anything, it should lead to the opposite, shouldn't it? Unless they meant to say that because of the lack of oxygen in the soil, bacteria rely on anaerobic methods to produce energy, which has arsenic as a by-product?

https://health.osu.edu/wellness/exercise-and-nutrition/how-t...