I.A UNMODIFIED MANAGED

Marshes under this category have not been impounded or ditched. Mosquito control is achieved by using larvicides when breeding becomes a problem.

I.B UNMODIFIED UNMANAGED

These are unmodified wetlands where no larvicides are used for mosquito control.

A closed impoundment is one which is not connected to the adjacent estuary at any time during the year. Impoundments maintained in this fashion may be actively flooded via pumps or wells, or passively flooded by trapping rainfall or stormwater runoff. Impoundments may be flooded year-round, or only seasonally.

Impoundment cells can be managed on a continuous flooding basis to provide suitable conditions for growth of waterfowl food plants and for feeding of resident and overwintering waterfowl. Although continuous flooding is not necessary to promote waterfowl utilization (see ¨Seasonal Drawdown¨), the technique may be used when there are no provisions for draining down the impoundment (no culverts), or when flooding must be maintained throughout the year for other reasons (e.g. for stormwater retention).

For best results for waterfowl, impoundments are flooded with 12 to 24 inches of water. Moderate salinities (about 10 ppt) are desirable but not imperative to grow Chara the primary waterfowl food plant. Depending upon the amount of freshwater inflow, the impoundment can be pumped-up with Indian River Lagoon water as needed to maintain desirable water levels and eliminate weeds.

Advantages:

1) If the marsh is kept flooded, salt marsh mosquito (and sandfly) production from that site is eliminated year-round with no need for larviciding.

2) If proper salinities can be maintained, the marsh may be managed for waterfowl habitat.

3) Conducive to development of large populations of resident fish.

Disadvantages:

1) Many of the natural marsh functions are eliminated.

2) Not having any estuarine connection, means that benefits provided by the late summer/early fall rise in sea level that normally penetrate a marsh are eliminated.

3) Biodiversity is reduced.

4) May adversely affect marsh vegetation.

5) Precludes the use of other management techniques.

6) Long term maintenance of a closed system may degrade waterfowl habitat.

An open impoundment is one where a connection to the adjacent estuary is maintained year-round through breaches in the dike or through open culverts. By definition, open systems interfere the least with the natural pathways of material, energy, and organism exchange between wetlands and the lagoon. Several types of open systems can be envisioned:

1. impoundments with breached dikes
2. impounded marshes where the culverts remain open all year.
3. connections maintained year-round by opening culverts only part way or by restricting spillage over riser boards. This is usually done to manipulate salinity, to control overdrainage of the marsh and/or to control water levels in all or parts of the marsh.

Open systems are best suited for areas where mosquito production is not a major problem such as areas removed from population centers, or in areas where other types of mosquito control can be effective. Open systems may also be appropriate as part of management schemes where management techniques in different members of an impoundment block alternate from year to year.

Advantages:

1) The marsh is able to largely function in a natural fashion.

2) If mosquito production is not a problem, continued management efforts are not required.

Disadvantages:

1) It is impossible to accomplish mosquito source reduction through flooding thus requiring other forms of mosquito control such as OMWM or the application of chemicals as needed (larvicides directly to the marsh and adulticides in nearby areas).

2) Large sand fly populations often develop along the marsh edges and along the edges of creeks.