BIOLOGICAL POLLUTION - Marine Pollution: What Everyone Needs to Know - page 189

scuba gear, as consignments of live organisms traded to pro-
vide live bait or food, and as symbionts or parasites carried by
other organisms. The mechanisms, extent, and consequences
of marine and estuarine invasions have been reviewed by
Gregory Ruiz and colleagues. In the 1800s, trans-Atlantic ship-
ping increased dramatically and many species were trans-
ported between Europe and the East Coast of North America.
The periwinkle snail (Littorina littorea) arrived in the early
1800s and is now widespread on rocky shores from Canada to
New Jersey. It has greatly altered the ecology of these shores.
Increased trade and shipping moves more organisms around
the world in ship ballast water in one month, than used to be
moved in a century. It is estimated that 7,000 species are car-
ried around the world in ballast water every day and 10 bil-
lion tons of ballast water are moved each year. Which species
will survive in a new location, and which ones may thrive and
cause problems cannnot easily be predicted, a phenomenon
that James Carlton has termed “ecological roulette.”
Fouling by attached organisms is another important vec-
tor. Organisms attach to the hull, to propellers and propeller
shafts, anchors, and anchor chains. Paints with tributyltin
are being phased out due to environmental concerns. With
less effective antifoulants, fouling will likely transport more
organisms in the future.
Many marine species including oysters, marsh grasses,
and fish were deliberately introduced for food or for erosion
control, with little knowledge of the impacts they could have.
Fish and shellfish have been intentionally introduced all over
the world for aquaculture, providing food and jobs, but they
can escape and become a threat to native species, ecosystem
function, or livelihoods. Pathogens or parasites associated
with the species that are moved can infect native species and
even humans. Atlantic salmon are reared in ocean net-pens
in Washington State and British Columbia. Many escape each
year, and they have been recovered in both saltwater and
freshwater in Washington State, British Columbia, and Alaska.