Encouraging Efforts at Environmentalism

Texas is home to one of the largest hypersaline estuaries in the world, the Laguna Madre. From Mexiquita Flats to the Boat Hole, the striking beauty of the mother lagoon is largely defined by the grass beds which carpet a significant percentage of its mud and sand bottom. Those of us who love to fish this vast, majestic body of water use the features in these grass beds to find and catch fish.

Redheads, pintails, herons, egrets, sea turtles, blue crabs, shrimp and other aquatic species use the grass beds for food, shelter, breeding and even as sites for simply loafing. The vital role these sea grass beds play in the continued health of the Laguna Madre cannot be overstated.

Five types of sea grass may be found in the lagoon: turtle grass, shoal grass, manatee grass, widgeon grass and halophila. With the exception of the relatively rare halophila, whose value to wildlife is basically unknown, each type of grass provides some benefit to various marine organisms. Also, the grass acts as a kind of insulation against turbidity, allowing the waters of the flats in the lagoon to maintain exceptional clarity even in relatively high winds.

The U.S. Army Corps of Engineers Galveston District is conducting a multi-year monitoring program intended to determine whether a newly developed management plan for dredging in the Gulf Intracoastal Waterway (GIWW) is reducing disposal impacts on these critically important sea grass beds in the Laguna Madre. Through the study of aerial images taken annually and with the support of survey efforts called "ground truthing," the Corps hopes to verify whether the plans are reducing or eliminating damage to the grass.

"The Corps is interested in working in more environmentally sensitive ways than we have in the past," says Terry Roberts, Environmental Lead for the project. "We hope that by monitoring the presence of the grass over time, we can refine our understanding of how to select the proper disposal methods and sites for dredge material."

The Corps currently works with Texas Parks and Wildlife, U.S. Fish and Wildlife, Texas Department of Transportation, National Marine Fisheries Service, Texas Commission on Environmental Quality and other groups to select sites. "We are working to minimize impact on water quality and subsequently sea grass beds not only through proper selection of disposal sites but also improved methods for disposal."

Mr. Roberts mentions an island recently constructed for dredge disposal near the intersection of the GIWW and the Port Mansfield channel. "The U.S. Fish and Wildlife Service tell us that brown pelicans have already started using the island. The good news is that we now have to take care not to disturb the pelicans while they are nesting."

After consulting with Ken Dunton of The University of Texas Marine Science Institute, the Corps determined that dredging in the Laguna Madre should only occur during the normal period of dormancy for sea grass, roughly between November 1^st and the end of February. "Since we are dredging during that time, our impact on sea grass and on nesting birds is minimal," Roberts says.

I was able to take part in the ground truthing portion of the study over a five day period around the turn of the new year. Working with Casey Hardin and Jeremy Marshall, employees of PBS&J, the company contracted by the Corps to do the bottom surveys, I was impressed with the depth of knowledge these men showed regarding sea grass and their commitment to documenting exactly what they found. Part skin-diver, part scientist and part enthusiastic eco-tourist, the surveyors provide needed data to the scientists ultimately charged with determining the effects of the dredging on the grass beds.

The ground truthing is used to provide a quality control for those scrutinizing the aerial images, so that they can be more confident in their interpretation and analysis of the images. The surveying is scheduled to continue until the scientists are certain they can properly utilize the annually renewed pictures.

Ground truthing starts with computer selection of 276 random points for surveying, then a list of GPS coordinates for those points is generated. Each point is labeled according to the amount of sea grass expected at the site and placed in four categories: "non-sea grass, light, moderate or heavy." A spot that is perceived to have over fifty percent coverage in sea grass is designated "continuous"; if less than fifty per cent coverage, as "patchy". Each point must then be visited by a team of trained personnel to determine the type or types of grass present and the actual density of coverage.

At each location, surveyors record the depth of the water, and if sea grass is present, drop one meter square quadrates to the bottom, three in a line for continuous spots, nine for patchy spots, spanning a total of ten or thirty meters. Then they must visually or tactually verify the presence of sea grass within the quadrates and record the percentage of coverage and relative abundance of type or types of grass present.

The depth of survey sites varies from zero (some are on dry land) to about two meters. The deepest spots are most difficult to survey, as they require the surveyors to dive to the bottom and verify the presence of grass with their hands. Working those sites requires wet suits, snorkels, masks and other gear, sometimes diving weights to combat swift currents.

The shallowest of the points are also difficult to survey, as they are often remotely located on flats navigable only by airboat, which the company doing the survey does not possess. After positioning bay boats as near to those sites as possible, the surveyors must then row kayaks and/or walk the rest of the way to record their data. In the worst-case scenarios, they traverse miles of shallow, muddy bottom on foot.

The folks from PBS&J are paid to go those miles, but more importantly, I got the impression that they are generally willing to go the extra mile to make the data accurate and complete. Likewise, the Corps seems genuinely intent on continuing to fund this project in the future, with the purpose of ensuring that damage to sea grass from dredging in the Laguna Madre is minimized or eliminated altogether.

Let's hope that Project Manager Karl Brown and the Corps continue to get enough money from Congress to maintain this well-intentioned project. It's safe to say that the days of cutting ditches through the Laguna Madre are not over, but maybe future efforts will have far less negative environmental impact than those of the past. As a bonus, a few lucky birds should find new nesting places suitable for continuing their kind.