Incognita, you are quite right about the Murray river and the situation going on over there. it is sad.

I'm a biologist, and one thing in your post was glaring at me: Algal blooms deplete the oxygen in the water because heterotrophic organisms consume the algae and use the oxygen in respiration. I'm sure you'll remember that plants (algae) produce sugar and oxygen through photosynthesis, so there is no way the algae can be using the oxygen themselves.

sorry to be particular.

Thanks