There are actually quite a lot just suspended in the water column -- a
decent oceanic average is about a million per mL! It was generally thought
to be quite low, because the assay used was the standard plating out to see
how many CFUs form, but at least 90% of marine bacteria will not grow in
culture. Since UV can penetrate quite well in water (very significant in a
least the first few metres), UV radiation accounts for a significant amount
of bacterial damage and mortality (parallel with UV induced viral lysis).
Interesting stuff!
Matt
UBC Department of Biology
