Overview: Caddo Lake in East Texas is just one example of how invasive plants are taking Texas by land and water. In part four of a six part series on the Gulf of Mexico, take a look at conditions, both natural and man-made, that impact water quality along the Gulf. We will examine the infamous "Dead Zone," off Louisiana, how it occurs and what its effects are. Learn about harmful algal blooms, such as red tide, where and when they occur and what the public needs to know when they happen. We'll also look at how water pollution has led to fish consumption advisories for many coastal waters and the trends in coastal water quality.