(Sorry for the delayed response; this one slipped through the cracks)
Psg B is referential to things mentioned in Psg A in a way that allows us to use information we learned in A and plug it into B.
The "literature" in psg A discussing the impact of loosestrife on wildlife mentions waterfowl and aquatic furbearers.
Psg B then references 'waterfowl' (which is definitely aquatic) in line 51 and then mentions furbearers (which we can understand to be the same aquatic furbearers that were being discussed in psg A).
This actually does pop up sometimes in ID the Disagreement questions in LR. You might see a correct answer in which there's some word that definitely didn't appear in the 2nd person's comments, but because the 2nd person is referentially addressing the 1st person's comments, it's fair for us sometimes to reasonably think that the 2nd person is alluding to what the 1st person was talking about.
Finally, you have the author of psg B saying that "none of the furbearing mammals discussed as being adversely affected by loosestrife can be considered threatened".
Since psg B thinks "there isn't a serious threat to any of the furbearing mammals ", even without saying 'aquatic' you can infer that psg B would say "there isn't a serious threat to any of the aquatic furbearing mammals".
Aquatic furbearers are a subset of furbearers, so if you've said "no furbearers are threatened", that includes aquatic / terrestrial / intergalactic, etc.
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Intergalactic Furbearers
