The other day, as I was relaxing a bunch of chemical "balancing" equations came to mind, mostly having to do with the Long Island Sound Oxygen deprivation.
2O2 + H2S + CaCO3 → H2CO3 + CaSO4
NH4+ + 2O2 → NO2 + 2H2O
NO2 + O2 → H2O + NO3-
The reality is that we are getting a lot of low oxygen levels with no or little plankton/algae present.
What i saw in the sediment suddenly came to life as I realized that it was the reaction of H2S with carbonates, using up significant oxygen in the process.
The issue Art Glowka brought up for consideration is not out of the equation, rather may be an even more important part of it.
He brought to mind cyano bacteria, bacteria which fix nitrogen into ammonia and then to Nitrite and then on to Nitrate. They are not facultative anaerobic organisms and so need oxygen to survive, unlike the organisms that are and many times produce H2S as a byproduct.
The high level of Sulfate in the water fits the balanced equation.
Still asking questions about all of this, so this is not an end post.