Baits Bite Lock at Milton is closed after a survey revealed structural issues.
A boating firm says money needs to be found and the Cam could be reduced to a "trickle" if locks fail.
Paul Bristow says if the locks fail "it threatens everyone who uses and enjoys the river".
Paul Bristow is one of several politicians worried that Ely and Haughley rail junctions may be forgotten.
A project to transform Peterborough's station is on the cusp of getting funds from the government.
A passenger who relies on the route tells the BBC its axing will "have a huge impact".
The Lib Dem councillor for Cambourne has been confirmed as the county council leader for a second term.
It is hoped works on the railway station and surrounding area will begin this year.
Paul Bristow was elected as mayor for the Cambridgeshire and Peterborough Combined Authority on Friday.
