Beach rock, also called coquina, is known as the Anastasia Formation by geologists. It consists of weakly cemented shell fragments, whole shells, and sand. Coquina forms when sea level falls, leaving the shore line behind. The natural acidity of rainfall dissolves some of the calcium carbonate in the shell and it is gradually re-deposited, cementing the particles together. Iron can also be involved in the process. The rock has been used for construction, particularly the Castillo de San Marcos, built 1672-1695. The soft nature of the coquina rock made it well suited to absorbing the energy of cannon balls.

 Biological Characteristics

Vegetation communities associated with the IRL include seagrass beds, freshwater marsh and salt marsh, mangrove swamp, hardwood hammocks, pine flatwoods, coastal scrub, maritime hammock, tropical hammock, beach dune, and dredge spoil. Each of these communities has a suite of indicator species that can be used to identify it. 

There are seven species of seagrass found in the IRL. Seagrass beds provide habitat structure and are a major source of primary productivity in the IRL. The main threats they face arise from poor water quality. As the transparency of water declines, seagrasses do not receive enough light to thrive and the system switches over to one dominated by planktonic and drift algae, which are not seen as having as much ecological value as seagrasses. The algae then intercept more sunlight, causing seagrass to decline further. 

 Nutrient loading also damages seagrass by promoting growth of algae, which compete with seagrass for light. Tons of nutrients are brought into the IRL watershed every year by humans in the form of food and fertilizers. As population continues to rise, this problem will get worse. Additionally, scarring from recreational boating damages seagrass beds.

 Freshwater marshes are found along tributaries and swale marshes between relict beach ridges within the IRL. Indicator species include Carolina Willow (Salix caroliniana) in disturbed areas, pickerelweed (Pontederia cordata), and various emergent grasses and sedges.

Salt marshes in the IRL north of Cape Canaveral are dominated by non-woody vegetation, primarily smooth cordgrass (Spartina alterniflora) and needle rush (Juncus roemerianus). These plants usually exhibit a taller growth form near open water and a shorter form approaching land (Montague and Wiegert, 1991). South of Cape Canaveral these plants begin to be replaced by mangroves. Saltgrass (Distichlis spicata), annual and perennial glasswort (Salicornia bigelovii and Sarcocornia perennis respectively) are found throughout the lagoon. Non-woody saltmarsh plants typically exhibit strong zonation that might be explained by factors such as environmental gradients or vegetative reproduction (Montague and Wiegert, 1991).

Mangrove swamps, together with salt marshes, are exceedingly productive systems that supply energy to the lagoon, and adjacent marine and terrestrial systems, and provide habitat structure. There are three species of mangrove in the IRL. To varying degree, all possess three primary adaptations that distinguish them from other trees: the ability to excrete and exclude salt, roots modified to serve as aerial gas exchange organs, and a method of reproduction referred to as “vivipary” in which the embryo either germinates on the tree or while floating (Odum and McIvor. 1990).

Between 1954 and the early 1970’s the majority of saltmarsh and mangrove swamp associated with the IRL was impounded in efforts to control saltmarsh mosquitoes (Rey, Kain, and Stahl, 1991). The female saltmarsh mosquito will not lay its eggs in standing water. Instead it chooses to oviposit in moist sand or mud. By 1950 these mosquitoes were showing considerable resistance to DDT, and mosquito control efforts began to focus on “source reduction” (Patterson, 2004). The most effective means of source reduction is to impound the marsh by construction of a perimeter dike to isolate the marsh (fig. 5). The impoundment was then flooded during breeding season to prevent oviposition.

A major drawback of impoundments is their interference with exchange between the marsh and lagoon. This lack of exchange particularly affects any species that uses the marsh for habitat in its juvenile stage. Many impoundments have been opened to allow exchange with the lagoon. For impoundments remaining closed, water drawdown is important to wading birds (Rosier, 1993). Opening impoundments has been shown to benefit fish populations (Poulakis, 1996), and zooplankton densities have been shown to remain similar to open lagoon if the impoundment is open at least during the winter (Rey, Kain, Crossman, Peterson, Shaffer, and Vose, 1991).

Hardwood hammocks are found where hydroperiod, disturbance regimes such as fire and storm frequency, and other variables allow their development. Hardwood hammocks generally occur adjacent to freshwater or in swales between relict beach ridges. Indicator species include the laurel oak (Quercus laurifolia), red maple (Acer rubrum), sweetgum (Liquidambar styraciflua) Carolina willow (Salix caroliniana), and buttonbush (Cephalanthus occidentalis).

Pine flatwoods are found on marine terraces – flat areas of land once offshore when sea level was higher. The typical vegetation is slash pine (Pinus elliottii) and longleaf pine (Pinus palustris) with an understory of saw palmetto (Serenoa repens) and ericaceous shrubs. 

Coastal scrub/maritime hammock are generally found landward of the back-dune area. Depending on disturbances such as fire and storms, these communities can be dominated by saw palmetto (Serenoa repens) or oaks (Quercus spp.). Ericaceous shrubs become more abundant west from the dune (Schmalzer, pers. Comm.). The farther west from the dune one goes, the older the sediments. Older sediments have been more strongly leached, resulting in less calcium carbonate available to maintain a circum-neutral pH. This gradient of decreasing soil pH favors Ericaceous shrubs which are able to out-compete other plants in acidic soils. 

Maritime hammock is dominated by live oak (Quercus virginiana). Mixed in the understory are plants such as beautyberry (Callicarpa americana), marlberry (Ardisia escallonioides), myrsine (Rapanea punctata), wild coffee (Psychotria nervosa), snowberry (Chioccoca alba), and stoppers (Eugenia axillaris, and E. foetida), (Johnson and Barbour, 1990). Scrub also contains myrtle and Chapman’s oaks, (Q. myrtifolia and chapmanii).

Tropical hammock is often associated with shell middens (Norman, 1976). Tropical species are found much farther north along the east coast of Florida due to the moderating effect of the ocean and lagoon on climate (Henry, Portier, and Coyne, 1994). Vegetation is similar to that found in maritime hammocks with additional species such as the Jamaican capertree (Capparis cynophallophora) and torchwood (Amyris elemifera). 

The beach dune community is inhabited by species able to tolerate salt, wind, and dry sandy conditions. These species include seaoats (Uniola paniculata), bitter panicgrass (Panicum amarum), seacoast marshelder (Iva imbricata), and railroad vine (Ipomoea pes-caprae). 

Dredge spoil communities are found along the perimeters of impoundments and dredged channels. This community often suffers the greatest invasion by non-native plants such as Brazilian pepper (Schinus terebinthifolius). Common species include salt myrtle (Baccharis halimifolia), Florida swampprivet (Forestiera segregata), and red cedar (Juniperus virginiana).

References

Bader, S. F., and R. W. Parkinson. 1990. Holocene evolution of Indian River Lagoon in
central Brevard County, Florida. Fla. Sci. 53(3): 204-215.

Cook, C. W. 1945. Geology of Florida. Fla. Geol. Surv. Bull. No. 29.

Cooper, J. A. G. 1994. Lagoons and micro-tidal coasts In (Carter, R. W. G., and C. D.
Woodroffe eds.) Coastal evolution, late Quarternary shoreline morpho-dynamics. pp. 219-265.

Henry, J. A., K. M. Portier, and J. C. Coyne. 1994. The climate and weather of Florida. 
Pineapple Press, Sarasota. 279 pp.

Johnson, A. F., and M. G. Barbour. 1990. Dunes and maritime forests. In R. L. Myers
and J. J. Ewel (editors) Ecosystems of Florida. Univ. of Central Florida Press, Orlando. pp. 429-480.

Montague, C. L., and R. G. Wiegert. 1990. Salt marshes. In R. L. Myers and J. J. Ewel
(editors) Ecosystems of Florida. Univ. of Central Florida Press, Orlando. pp. 481-516.

Moore, R. H. 1992. Low-salinity back bays and lagoons. In C. T. Hacking, S. M.
Adams, and W. H. Martin (editors) Biodiversity of the southeastern U.S. aquatic communities. John Wiley & Sons, Inc., New York. pp. 541-685.

Norman, E. M. 1976. An analysis of the vegetation at Turtle Mound. Fla. Sci. 39(1):
19-31.

Odum, W. E., and C. C. McIvor. 1990. Mangroves. In R. L. Myers and J. J. Ewel
(editors) Ecosystems of Florida. Univ. of Central Florida Press, Orlando. pp. 517-548.

Osmond, J. K., J. P. May, and W. F. Tanner. 1970. Age of the Cape Kennedy barrier-
and-lagoon complex. J. Geophys. Res. 75: 467-479.

Patterson, G. 2004. The mosquito wars, a history of mosquito control in Florida. 
University Press of Florida, Gainesville. 264 pp. 

Parkinson, R. W. 1995. Managing biodiversity from a geological perspective. Bull. Of
Mar. Sci., 57(1): 28-36.

Poulakis, G. P. 1996. Patterns of habitat use by fishes within a newly reconnected
impounded mangrove marsh in east-central Florida. Unpublished master’s thesis Florida Institute of Technology. 

Rey, J. R., T. Kain, and R. Stahl. 1991. Wetland impoundments of east-central Florida. 
Fla. Sci., 54(1): 33-40.

Rey, J. R., T. Kain, R. Crossman, M. Peterson, J. Shaffer, and F. Vose. 1991. 
Zooplankton of impounded marshes and shallow areas of a subtropical lagoon. Fla. Sci., 54(3/4): 191-203.

Rosier, J. C. 1993. Wading bird feeding responses to manipulated water levels in
Florida saltmarsh impoundments. Unpublished master’s thesis, Florida Institute of Technology. 135 pp.

Stickney, R. R. 1984. Estuarine ecology of the southeastern United States. Texas A&M
University Press, College Station. 310 pp. 

White, W. A. 1958. Some geometric features of central peninsular Florida. Fla. Geol.
Surv. Bull. No. 41. 

Woodward-Clyde Consultants. 1994. Indian River Lagoon Nat. Est. Project, Physical
Features of the Indian River Lagoon. Indian River Lagoon National Estuary Program, Melbourne , FL. Final Tech. Report. Project # 92F274C. Tampa , FL.
 

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