I think you definitely want to treat in sections - a whole lake full of dying plants (any kind) is begging for water quality problems.

Classic definition: My 1 acre BOW is a lake. Your 10 acre BOW is a pond.

More seriously, a dividing line can be drawn anywhere between, say, 10 and 30 acres. Much material for discussion.

"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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