With respect to Trichodesmium erythraeum itself, there’s the question of whether the response in the real world would mirror that observed in culture in terms of selection for the cultured irreversible phenotype, whether any such selection would completely wipe out non-selected phenotypes in the wild, and whether reversion would be impossible in the natural environment across the span of oceans and time should all non-selected variants be wiped out.

And do the observed effects (and caveats in the preceding paragraph) apply to all species of Trichodesmium?

And if Trichodesmium is wiped out by a post-enhanced carbon crash, would its niche(s) be filled by other nitrogen fixers? Would such replacements be able to provide the same ecosystem functions?

In the mean time, the ramping up of nitrogen fixation that was observed is not necessarily a good thing. One only needs to consider the profoundly negative consequences of much eutrophication that has occurred over the last century or so: in many ways this is simply a eutrophic process. A wholesale ramping of Trichodesmium could have profound ecological effects in (and beyond) the oceans, and given their crucial place in the marine trophic web they could even affect biotic influences on climate.

There are many provisos that arise from this work, but for the cautious biologist this is a disturbing study.

We already see something similar with algae blooms in Lake Erie.

https://www.google.com/search?q=what+eats++Trichodesmium

‘Liebig’s law of the minimum, often simply called Liebig’s law or the law of the minimum, is a principle developed in agricultural science by Carl Sprengel (1828) and later popularized by Justus von Liebig. It states that growth is controlled not by the total amount of resources available, but by the scarcest resource (limiting factor).’