Identification of Tidal Flat Alterations and Determination of Effects on Biological Productivity of These Habitats Within the Coastal Bend

Withers, Kim; Tunnell, John

Tidal flats within the Corpus Christi Bay National Estuary Program (CCBNEP) study area are unique because they are inundated and exposed mostly in response to winds rather than astronomical tides, hence “wind-tidal flat”. On bay sides of barrier islands wind-tidal flats replace salt marsh as the primary wetland type. Because tidal inundation is irregular and extreme temperatures occur when thin sheets of water are heated by the sun, macrophytic plant communities cannot develop and biologic activity is often restricted to felts or mats of blue-green algae which form over the surface of and bind the sand and/or mud substrate. The public image of tidal flats as barren wastelands contributing nothing aesthetically, economically, or ecologically is the underlying cause of most human disturbances and alterations. However, their appearance belies their importance to overall productivity of estuaries within the CCBNEP study area. Worldwide, the most extensive wind-tidal flats are found around hypersaline lagoons like the Laguna Madre. There are nearly 62 square miles of wind-tidal flats within the study area, with almost 79% located on the bay sides of San Jose, Mustang and Padre islands. The remaining wind-tidal flats are found along mainland bay margins, around river deltas, and the mouths of creeks. Barrier island tidal flat sediments are mainly sands, whereas mainland sediments are mainly clays. The objectives of the present study are: (1) to compile and synthesize all published and unpublished information concerning ecology, geology, and hydrology, of wind-tidal flats in the CCBNEP study area; (2) to determine locations of anthropogenic and natural disturbances and alterations to wind-tidal flats in the study area and rate their severity; and, (3) to formulate an evaluation strategy to determine wind-tidal flat productivity for both baseline and postdisturbance monitoring.