## Gulf of Mexico Integrated Science - Tampa Bay Study **Characterization of Tidal Wetlands**

cal effects and ecological functions of mosquito ditches to plan andaccess restoration of ditched wetlands.
U.S. Geological Survey (USGS) scientists have permanently tagged mangrove trees to measure theirgrowth and survival rates in a variety of hydrological and ecological settings, both natural and altered. At ditched sites, sediments wereside cast during ditch construction, thereby forming raised areas, termed berms, along ditches. These berms tend to act as dams, thereby changing the timing and duration of fl ooding of adjacent forests aswell as the composition of streamside vegetation. For example, 

### Introduction
Tidal wetlands in Tampa Bay,Florida, consist of mangrove forests and salt marshes. Wetlands buffer storm surges, provide fi sh and wildlife habitat, and enhance water quality through the removalof water-borne nutrients and contaminants. Substantial areas of both mangroves and salt marsheshave been lost to agricultural, residential, and industrial development in this urban estuary. Wetlands researchers are characterizing the biological components of tidalwetlands and examining the physical factors such as salinity, tidal fl ushing, and sediment deposition that control the composition of tidal wetland habitats. Wetlands restoration is a priority of resource managers in Tampa Bay. Baseline studies such as these are needed for successful restoration planning and evaluation. 

### Approach
**Mangrove health**
Mangroves are trees that are adapted to grow in salt water, and are the dominant feature of the intertidal landscape in Tampa Bay. Mangroves are sensitive to sediments contaminated by oil and oil by-products. Red mangroves affected by such contaminants show changes in their physicalappearance in the form of albinism in their propagules, i.e., seedlings that germinate while still on the tree. Albinism is an easily observed characteristic because affected propagules are pink or yellow instead of their normalgreen color. Thus, a high percentage of albino propagules can beused as an indicator of contaminants in red mangrove-dominated wetlands. **Mangrove vegetation and fi shes**
Tampa Bay tidal wetlands arefl ooded and drained by both natural tidal creeks and by man-mademosquito control ditches constructed primarily between 1940 and 1970. These ditches were built to control salt marsh mosquitoes by promoting access by small fi shesthat eat mosquito larvae throughout the tidally inundated forests. More advanced means of mosquito control, including larvicides that solely target mosquito species, are now available. Therefore, resourcemanagers need data on the biologi**Map of Tampa Bay study area showing locations of sampling sites (red - fi sh sam**  **pling sites, green - landscape history and ecology, blue - mangrove genetic survey,**  **gold - vegetation study).**

**Normal propagules of the red mangrove are green. Those propagules lacking**  **normal pigments are termed albino and are pink or yellow in color.** 

USGS Open-File Report 05-1174 April 2005 U. S. Department of the Interior U. S. Geological Survey**Carole McIvor** , Task Leader U.S. Geological Survey, Biological Resource Discipline 600 4th Street South, St. Petersburg, FL 33701 Email: carole_mcivor@usgs.gov

**Kimberly Yates** , Project Chief U.S. Geological Survey, Geologic Discipline 600 4th Street South, St. Petersburg, FL 33701 Email: kyates@usgs.gov **For more information, please contact:**

**http://gulfsci.usgs.gov Tom Smith**  , USGS/Biological Resource Discipline
**Ed Proffi tt** , USGS/Biological Resource Discipline
**Steve Travis** , USGS/Biological Resource Discipline
**Ellen Raabe** , USGS/Geologic Discipline **Randy Runnels** , Florida Dept. of Environmental Protection
**Karen Hill** , Pinellas County Dept. of Environmental Management **Contributing Scientists:** elevated berms favor undesirable invasive species like Brazilian pepper over native mangroves.USGS scientists are also characterizing the species composition of fi sh, shrimp, and crabs that use natural creeks and man-made mosquito ditches. Wetland ditches with good tidal fl ushing support a wide variety of commercial and recreational species, including red drum, snook, spotted seatrout, sheepshead, mullet, black drum, pink shrimp, and blue crab. **Coastal landscape**
USGS scientists are incorporating data from modern and historic sources to identify changes in coastal vegetation communities. Cartographic and photographic analyses strongly suggest that mangroves have been replacing salt marsh and low-salinity coastal wetlands in a gradual northerly and landward direction in Tampa Bay since 1874. Factors favoringmangroves over salt marsh vegetation include a warming climate, freshwater diversions, and alteredwetland hydrology such as mosquito ditches. Rising sea levels mean that mangroves will also expand inland and upriver where there are no barriers such as berms or seawalls. Apparent mangrove expansion has implications for restoration. Long-term, freshwater wetlands and low-elevation coastal forests will need relatively greaterprotection as they receive simultaneous pressures from mangrove expansion from seaward, and urbanexpansion from inland. USGS scientists are working with resource managers from state and county agencies to defi ne the hydrological and physical conditions that favorthe dominance of a particular intertidal species over another. They are examining conditions under which engineering actions such as plugging mosquito control ditches and excluding tidal waters might promote long-term development of freshwater wetlands in selected locations. 

### Links to Other Project **Research**

Wetlands scientists use core data collected by geologists to understand the past history and longevity of tidal wetlands in their present locations. On a different timescale, remote sensing experts supply high-resolution mapping data that give a current view of bay wetlands and their elevations. Data from the water quality team on sediment contaminants adjacentto tidal wetlands supply information on past and ongoing stressors.**27 o** **54’ 82**  **o 39’** 

**1874 Historic T opographic Chart** 

**1999 CIR Aerial Photography 27** **o 54’** 

**82 o**  **39’ Salt Marsh** 

**Mangrove and Mosquito Ditch**  **Complex Mangrove**  **fringe Uplands** 

**1874 coastline 0**  **0.5 1 km** 

**USGS scientists track changes in Tampa Bay tidal wetlands by comparing historic**  **shoreline and wetland features at Feather Sound.**  **Researchers sample fi sh and crustaceans (shrimp, crabs) in a manmade mosquito**  **control ditch in a modifi ed wetland.**