When dams impound water, they stop the current and permit silt to accumulate in the water, which can clog mussels' gills and tie up the oxygen they need to survive.
(dams; impound; water) (the water; tie up; the oxygen they need to survive) (they; stop; the current; T:When dams impound water) (they; need; to survive) Context(they need,List([143, 152))):(the oxygen; to survive; they) (they; permit; to accumulate in the water; T:When dams impound water) (silt; to accumulate; L:in the water) (the water; can clog; mussels' gills)
they need,List([143, 152))
dams the water they they the oxygen they silt the water
impound tie up stop need to survive permit to accumulate can clog
water
the oxygen they need to survive
the current T:When dams impound water
to survive
they
to accumulate in the water T:When dams impound water
L:in the water
mussels' gills