What is the author's purpose in this passage? mostly persuasive mostly explanatory slightly persuasive

zebra mussels

the zebra mussel is a nuisance species that
has been invading u. s. lakes since 1988.
native to eastern europe and asia, it probably
entered the great lakes on a commercial ship.
that event delivered the mussel to a new
environment where it has no natural enemies to
control its growth. in less than 10 years, it spread
to 19 states, ranging from canada to the gulf of
mexico and concentrating in the eastern half of
the country. this species causes widespread
and costly damage to the environment and
industries.

how they spread
the spread of zebra mussels across the
u. s. is facilitated by boats that go from one lake
to another. the mussels attach themselves to
the bilge or to live-bait wells and are transported
to another lake. there, they take over space
from native mussel species, disrupting the
native species' ability to feed, grow, breathe,
and reproduce, and causing many of them to
become endangered. for example, clams have
nearly disappeared from parts of lake erie.

the damage
as this species grows, it threatens the
microscopic aquatic plant and animal life
necessary to maintain lakes' ecosystems. the
mussels often clog intake pipes, damaging
water supplies and industrial processes. one
paper company had to spend $1.4 million to
clear its intake pipe of zebra mussels.

preventing the spread
it's extremely difficult to kill these mussels
once they have contaminated an area. chlorine,
for example, will kill them, but would also be
toxic to the whole marine ecosystem where they
thrive. so, preventing their spread is key to
containing their increasing presence in our
water bodies.
people who take boats (or other watercraft)
into lakes should take several precautions to
keep from transporting zebra mussels from one
lake to another. after removing the boat from a
fresh water body, boat operators should use hot
water to rinse the hull. they must flush the
engine, clean the bait wells, and drain standing
water from the bilge, live wells, and bait buckets.
bait should not be brought from one lake, which
may be infested, to another, but thrown out. all
screens and water intakes must be checked for
mussels, and the boat left out in dry heat for
several days to kill any mussels or larvae.