What is missing in that article is "what, exactly, causes the production of oxygen in the first place", and then maybe they should look at a transport mechanism likely to get it down though perhaps kilometers of ice to the hypothesized water.
To this end, researchers sought to estimate the level of oxygen reaching the ocean. To find out more, experts led by Greenberg considered the age of the moon’s surface. Its geology and a lack of impact craters, suggests that the ice is continually reformed in an active process and the current surface maybe no more than 50 million years old, just a fraction of the age of the Moon.
The experts considered three generic resurfacing processes: the gradual layering of fresh material on the surface; cracks which are filled with fresh ice from below; and patches of ice that are disrupted and replaced with fresh material.
Using estimates for the production of oxygen at the surface, Greenberg found that the delivery rate into the ocean is so fast that the oxygen concentration could exceed that of the Earth’s oceans in only a few million years.
The continual supply of oxygen could support roughly 3 billion kilograms of 'macrofauna', the research suggests - assuming similar oxygen demands to terrestrial fish.
To sum up the salient points of logic:
“Ice is continually reforming… the current surface is a fraction of the age of the moon…experts considered 3 resurfacing properties (forming new ice)…using estimates of oxygen production at the surface… the oxygen concentration could exceed that of Earth’s ocean’s in a few million years.”
The disconnect is his going from examining theories of how new ice is formed to "therefore oxygen production at the surface does thus and such". No wonder this scientist merely suggested that the ocean may be highly oxygenated. The article, anyway, fails to describe how that oxygen is created in the first place! New ice, maybe. Ice production by itself doesn't create oxygen or else our refrigerators' ice makers might be a source of an explosion when we open the door and the light comes on!
I could have attended that conference and showed ways that new ice could be being made and all that and then suggested in the next breath, "Using estimates for the production rate of sodium at the surface based on the surprising amount seen in the plume ejecta, we estimated that within a few million years the ocean would have achieved a salinity 7 to 8 times that of Earth's oceans." My suggestion, using precisely the same non sequitur
as his, should be equally valid. --Maybe better; who knows?
That's the big question here, for the conferees: who the #@* knows
If he had said that ionization from a source of radiation or from the solar wind is stripping the H from the H2O, or maybe Eskimos with refrigerator-freezers that can't be resolved by Cassini, maybe he'd be going somewhere, and we'd have some silly thing to think critically about, but he doesn't go there.