An exotic species originally introduced
into the Great Lakes via the ballast water of transoceanic
ships. This small bivalve mussel poses a multibillion dollar threat to industrial,
agricultural, and municipal water supplies across North America by clogging water
intake pipes. It can also have impacts on fisheries, native freshwater mussels,
and natural ecosystems. By moving along contiguous waters of the Great Lakes,
attached to ships, barges and recreational boats, this Eurasian native has rapidly
spread throughout the Mississippi River Basin and many of its major tributaries
such as the Ohio River. Free-swimming larvae are also spread by river currents.
Boater education campaigns focus on preventing further spread of this species.
Zero discharge refers to halting
all inputs from all human sources and pathways to prevent any opportunity for
persistent toxic substances to enter the environment from
human activity. To completely prevent such releases, the manufacture, use, transport,
and disposal of these substances would have to stop. The Binational
Program has designated nine toxic substances (critical
pollutants) to be part of the Zero Discharge Demonstration
Program for the Lake Superior Basin. These substances
are chlordane, dieldrin, dichloro-diphenyl-trichloro-ethane
(DDT and its metabolites such as DDE), hexachlorobenzene
(HCB), mercury, octachlorostryrene
(OCS), polychlorinated biphenyls (PCBs), 2, 3, 7,
8 tetrachlorodibenzo-p-dioxin (TCDD), and toxaphene.
Zero Discharge Demonstration Program
This international program
is in response to the recommendation by the International
Joint Commission that Lake Superior be designated a zero
discharge demonstration zone where no point source
discharge of any persistent bioaccumulative toxic substance
be permitted. Nine persistent toxic substances (critical
pollutants) have been designated as critical for the program. The first priority
of the program is the goal of achieving zero discharge of the nine substances
from point sources. To completely prevent such releases, the manufacture, use,
transport, and disposal of these substances must stop. This objective is to be
Related Program - Binational
- pollution prevention;
- enhanced controls and regulations,
- protection through special designations of all or part of the basin (See
also Outstanding International Resource Waters and Outstanding
National Resource Waters).
Zone of Initial Dilution ZID
The region of initial mixing surrounding or adjacent to the end of an outfall
pipe or diffuser. The ZID may not be larger than allowed by mixing
zone restrictions in applicable water quality standards.
Small, mostly microscopic animals
that swim or float freely in open water. Zooplankton eat algae,
detritus, and other zooplankton and in turn are eaten by fish.