Exceptions are that often only one or two species of algae grow when the urchins are very active but then control of urchins by sea otters and sea birds, lobster and fish all return things to normal.
(Exceptions; are; that) (only one or two species of algae; grow; T:when the urchins are very active but then control of urchins by sea otters and sea birds, lobster and fish; T:often) (the urchins; are; very active)
Exceptions only one or two species of algae the urchins
are grow are
that
T:when the urchins are very active but then control of urchins by sea otters and sea birds, lobster and fish T:often
very active