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Section 2 Existing Conditions/Affected Environment

EAA Storage Reservoirs Revised Draft PIR and EIS February 2006

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2.9.1.3 Exotic Plants

The most recent vegetation mapping of the western Lake Okeechobee littoral

zone and marsh, conducted by SFWMD, clearly depicts the dynamic state of

vegetative succession within the littoral zone and the spread of less desirable

and invasive exotic species into new areas. Results of this vegetation mapping

show extensive areas of melaleuca along the rim canal and near shore; spike

rush particularly in the Moonshine Bay area; cattail mostly interspersed in

smaller stands; hydrilla where large monotypic floating and submergent mats

dominate in Fisheating Bay; and, large stands of torpedograss, which largely out

compete other species at most water levels.

2.9.2 Northern Estuaries

Seagrasses are undoubtedly among the most important vegetation of the St.

Lucie and Caloosahatchee River Estuaries as well as the Indian River Lagoon.

Seagrass meadows improve water quality by removing nutrients, dissipating the

effects of waves and currents, and by stabilizing bottom habitats thereby

reducing suspended solids. Seagrass beds support some of the most abundant

and diverse fish populations in the Indian River Lagoon. Seagrass and

macroalgae (collectively referred to as submerged aquatic vegetation, or SAV)

are highly productive areas and are perhaps the most important habitat of the

Indian River Lagoon (IRL CCMP, 1996).

In the St. Lucie Estuary, the predominant species of seagrass is shoalgrass.

Shoalgrass often occurs in shallower areas and is commonly used as an indicator

species for salinity tolerance ranges and general ecosystem health. Johnson’s

seagrass, listed as a threatened plant species by the National Oceanic and

Atmospheric Administration, may also occur in the vicinity of the St. Lucie

Estuary or Indian River Lagoon. In the Indian River Lagoon, turtlegrass occurs

in waters generally deeper than 1-2 feet and is often associated with

manateegrass.

In the Caloosahatchee River, the primary species of importance is vallisneria.

Like the seagrasses of the St. Lucie Estuary and Indian River Lagoon,

vallisneria is used extensively as an indicator species for a wide variety of other

biota for this area. Vallisneria is a valuable waterfowl food and is considered an

excellent plant for fish spawning areas along the river margin. In some areas,

vallisneria is declining due to competition with hydrilla and Eurasian

watermilfoil, an invasive exotic species (USACE, 1988).

The SAV communities have experienced substantial declines in acreage and

quality in recent years. An estimated 30% of the seagrass communities have

been destroyed in Florida’s estuaries since the 1940s. The Indian River Lagoon

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Wenger 72944 Dokumentacja Strona 74