NATURAL RESPONSES TO A RANGE OF ANTHROPOGENIC ALTERATIONS TO ESTUARIES: A CASE STUDY OF THE MATAGORDA BAY SYSTEM, NORTHERN GULF OF MEXICO

The Matagorda Bay system provides an ideal case study for how bays naturally respond to anthropogenic alterations. The wide range of responses to anthropogenic alterations generally fall into three broad categories, which are: 1) expansion and contraction of deltas due to changes within the respective drainage basins. Examples include two episodes of rapid expansion of the Colorado River delta and the retreat of the Lavaca River bayhead delta. 2) Alterations of the tidal prism and tidal inlet configuration due to installation of new inlets and river system alteration. The most dramatic example of this is the tidal prism capture by the Matagorda Ship Channel and the partial closing of Pass Cavallo, the historically permanent tidal inlet of the Matagorda Bay system. 3) changes in size and distribution of oyster reefs due to dredging; hydrocarbon gather system other infrastructure installation; and shell mining. Within Lavaca Bay, in upper Matagorda Bay, these combined impacts appear to have lead to a 75% loss surface area of the historical oyster reefs. However, the creation of dredge spoil piles, artificial reefs and other hard substrate has provided 25% more habitat, resulting in a net loss of 50% in oyster reef distribution since 1900.