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Remediation Trials

---Part 5 of a 6-Part Series---

As with many of the project areas within the larger Brown Marsh Project, efforts aimed at creating remediation strategies began prior to the project's official start date. Greg Grandy, senior project manager for the Louisiana Department of Natural Resources (LDNR), wasted no time in putting the groundwork for remediation efforts in place.

Using Greg Linscombe's fly-overs and the McKee-Mendelssohn team's 21 plots as a starting point, Grandy commissioned a series of helicopter overflights intended to assess the dieback from a remediation-specific standpoint. Prior to the detailed classification protocol put forward by Handley and the mapping team at USGS, this "quick and dirty" assessment guided the formulation of the remediation projects, allowing the remediation specialists to proceed even as the search for causes was getting under way.

One of the experts central to the project's remediation studies is Mike Materne, a coastal wetlands plant specialist with the Natural Resources Conservation Service (NRCS). A researcher at NRCS's Golden Meadow Plant Materials Center, Materne brings a history of specialized, applied research to the problem at hand, having released a "cultivar," or "cultivated variety," of smooth cordgrass with heightened salinity and water tolerance in 1989.

Materne accesssion study

Given this experience and his early involvement with the dieback, Materne was eventually charged with heading up three principal tasks in the Brown Marsh Project. The first task is an "accession characterization," the second involves aerial seeding trials, and the third examines the viability of the on-the-ground placement of treatment plots in critical areas, areas such as those under the erosive force of high wave energy.

Materne's accession study is an effort to cultivate various "ecotypes" from among the survivors at the McKee-Mendelssohn team's 21 test plots and subsequently test their heartiness by placing them back into three severely affected sites in the Terrebonne and Lafourche basins. In botanical terms, "ecotype" refers to a population within a species that exhibits genetic adaptation to a specific local environment and whose phenotype-that is, unique physical characteristics-survives transplantation into new surroundings. Materne's group allowed the 40 separate ecotypes they identified to propagate by the rhizomal method, the same method of extending horizontal, subsurface runners that causes grass to fill barren soil in suburban lawns.

With plots of the 40 ecotypes planted in the three severely affected areas, Materne's research group is measuring a number of heartiness indices in each, among them plant productivity, the number of seeds produced, their mass, and height. But chief among the characteristics they are keen on observing are the survivorship rates. After determining the handful of ecotypes with the highest survival rates, Materne plans to select among this narrowed group for the highest productivity, as these would be the best candidates for replanting and reseeding efforts.

Moreover, given the presence of aluminum and iron discovered in the original soil assays, Materne's group is in the process of examining survivorship and productivity in relationship to the presence of these metals. And according to Materne, "Even if the most metal tolerant ecotype turns out to be the scrawniest of the 40, it will still make a tempting candidate for crossbreeding with the most productive."

Such crossbreeding, should it occur, would occur by way of seed-based, sexual germination. Germination in smooth cordgrass, as with many grasses, is a little used secondary reproductive system in a plant that has spent eons largely reproducing via asexual, vegetative means. Nevertheless, restoring vast expanses of brown marsh by means of aerial reseeding is the focus of Materne's second remediation task.

When asked by Governor Foster at the outset of the dieback whether the brown marsh could be replaced, Materne and other scientists could do little more than give the Governor a flat "no" for an answer. Given that smooth cordgrass purchased in bulk for smaller, ground-based restoration efforts costs $6.00 per plant, the massive reach of the impacted areas, and the labor cost that would have been required, the price tag of a planting program was clearly far too prohibitive.

Seeding smooth cordgrass, however, comes with its own set of problems. Not only do the seeds mature slowly, they mature in what botanists refer to as "indeterminate inflorescence," meaning the seeds are in a variety of developmental stages at any one time on any one plant. In nature, the seed would be dropped into the water where it would spend the winter before germinating in the spring. Hence, seed storage requires water kept slightly above freezing, along with the addition of salt or some other fungicidal agent. Over and above the problems inherent in collection and storage, however, Materne's team also had the mechanics of the seeding process to work out as well.

More than simply dropping seeds and hoping they would produce results, the goal was to examine both germination and seedling survival rates in an effort to establish the most efficient seed density. To this end, Materne conducted three trials in the spring of 2001: one serving as a freshwater control group, one in Bayou Lafourche, and the third in Lake Felicity. As expected, while the germination rate was 75% in the control group, the fresh water setting allowed no seedling survival. At Bayou Lafourche, there was a 40% germination rate, but, once again, no measurable seedling survival. At Lake Felicity, however, not only was the germination rate 40%, but 35% of the seeds that germinated went on to become viable seedlings.

With the freshwater control demonstrating that germination rates higher than 40% were possible, Materne and his group then set about the business of selecting seeds for their germination and survival rates. Combining this with their previously measured rates from the Bayou Lafourche and Lake Felicity trials, for their second study in the spring of 2002, the team calculated that 70 seeds per square foot (30 pounds of seed per acre) would likely result in the on-ground density of 10-15 plants per square foot needed for the grass to take hold and propagate on its own. And while the ultimate survivorship of the smooth cordgrass has yet to be determined as of fall 2002, the initial results seem to indicate that Materne's group has hit its target. The 25-acre study area had a 60% germination rate and a subsequent 50% seedling survivorship, amounting to an average of 10-15 plants per square foot.

Moreover, Materne is confident that the collection and storage problems are on the verge of being solved, and he is "hopeful that seeded restoration will become a reality inside the next three to five years." In other words, if there should be another brown marsh dieback in, say, 2006 and the next Governor should come to the scientific community and ask if the marsh can be revegetated, chances are good that the scientists will be able to answer with a practical, cost-effective "yes." And while six years might seem to be a long time, in the world of applied science the move from a complete standstill to the ability to revegetate hundreds of thousands of afflicted acres is, in fact, "science at warp speed."

The third task that Materne and affiliated researchers are heading up is an investigation of revegetating "critical target areas," marsh-edge areas that are highly resistant to aerial reseeding because they are subjected to wave energy and other erosive forces. The approach of this investigation has been to examine the viability of a third alternative to planting or seeding, namely the placement of fiber mats impregnated with smooth cordgrass material. Materne's group has anchored two types of mats in large sections within critical areas, and they are testing the mats themselves for durability.

More important than mere durability, they are also examining three various methods of impregnating the mats: seeds, shredded rhizomal matter, and plants themselves. The success of these methods in environments especially sensitive to the vagaries of seasonal events such as tropical storms calls for extended trials before "success" can be accurately measured. However, Materne is hopeful that a "cost-effective middle path" may eventually be achieved, a means that may prove crucial to restoring the protective, outermost edges of the marsh.

A final remediation task that began in July 2002 involve the placement of nutrient-rich dredged material in Bayou Lafourche, one of the areas most severely affected by the dieback. Headed by Greg Grandy, the plan calls for thin layers of material to be placed in severely compromised areas in six-, nine-, and twelve-inch layers. Although the increased elevation these layers will create will likely provide some small degree of boost to smooth cordgrass tracts that are having trouble coping with subsidence-related water levels, the main interest for Grandy and his team is the role, if any, that the nutrients within the dredged material can play in helping dead and struggling areas regain their vigor.

Once this series of vegetative platforms is established in the fall of 2002, some will be set aside to receive vegetative plantings derived from McKee-Mendelssohn's laboratory studies and Materne's field work. For the most part, the vegetative studies will follow the McKee-Mendelssohn team's experimental design, planting black needlerush and black mangrove along with smooth cordgrass so that the success of each species and smooth cordgrass ecotype can be monitored with respect to the others. In addition, Grandy's forthcoming field trials will involve two additional indigenous species, saltgrass (Distichlis spicata) and saltmeadow cordgrass (Spartina patens).