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Georgia's Marsh Die Back and Louisiana's Marsh Browning

Naturally Occurring Cycles or a Products of Human Disturbance? What can scientists in Georgia learn from Louisiana's efforts to understand a similar environmental disorder?

By: Dorset Hurley, Research Coordinator, Sapelo Island National Estuarine Research Reserve
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Estuarine and marine scientists working in the marshes of the southeastern United States became aware of vegetative denudation or "Marsh Browning" areas in the coastal marshes of Louisiana in the fall of 2000.

By the Spring of 2001 in the Barataria-Terrebone salt marshes alone which comprise 390,000 acres of Louisiana's salt marsh systems, displayed vegetation declines in over 260,000 of those acres. The Governor of Louisiana declared the situation a "state of emergency" and obtained 3 million dollars in state and federal support to assist in the study, control and hopefully the reversal of the disorder.

In Louisiana, this ecosystem-level phenomenon seemed to exhibit similar symptoms within many of the affected estuarine areas of the state. However, its causal agents were unknown. Louisiana scientists termed the phenomena "Marsh Browning" due to the diseases early-stage symptoms which caused affected Spartina alterniflora or smooth cord grass, to turn brown as the aboveground vegetation died.

Georgia salt marshes started displaying similar vegetation disease symptoms in the Fall of 2001, about the same time that Louisiana's marshes began their slow, natural recovery. By the Summer of 2002 Georgia's Department of Natural Resources assessed "Marsh Die-Back" as affecting approximately 1500 acres of Georgia's 400,000 acres of salt marsh.

In Georgia however, the phenomena's genesis and epidemiology appeared different than that noted in Louisiana. Affected marshes in Georgia seemed to undergo dramatic shifts in vegetation coverage which displayed sharp transition zones between vegetated and non-vegetated areas.

Georgia's Die-Back disease was affecting both Juncus romarianis.( black needlerush) and Spartina alterniflora. Other symptoms that appear unique to Georgia's coastal Die-Back include: complete rhizome (root mass) failure in affected plants, the advance of the disease from tidal creek and low marsh areas toward high marsh areas and the sporadic nature of the disease's expression which seems to chronically affect smaller areas of both high and lower salinity marshes. These observations in the expression of the disease add to the mystery of Georgia's Marsh Die-Back and Louisiana's Marsh Browning which have scientists baffled as to whether or not they are:
  • Studying the same marsh disease
  • Studying the same symptoms of different diseases
  • Investigating closely related causal factors which express similar but not identical symptoms.

Scientifically, an environmental situation of this magnitude represents a challenge that requires scholars of varying disciplines and programs to collectively partner and plan. This in-turn creates a sharing, intellectual environment, which much like the environmental system under study, responds to information input, energy flows and feedback loops.

In Louisiana, the issue was pervasive enough that the level of funding for studying the phenomena was sufficient in size to synthesize a wide range of applied science results. These results may provide future aid toward reversing the "Marsh Browning" trend should it reappear in Louisiana. Additionally, many of the results among Louisiana and Georgia scientists were shared in a very productive interactive two day forum facilitated by the Georgia Coastal Research Council in Savannah this Spring.

After extensive aerial assessment of Louisiana's marshes, certain trends emerged in the data related to coverage, extent and marsh condition of the states affected area. These trends helped formulate the baseline of scientific questions and management efforts directed at understanding Marsh Browning. The following commonalities were noted in affected Louisiana salt marshes:
Jerico River Site
Teal Marsh 40 FT.
Jerico Site #2

Photos taken in September 2003, from the DNR helicopter by AIMEE GADDIS, STEWARDSHIP COORDINATOR FOR SINERR
  • A landmark drought of three consecutive years precluded the occurrence of Marsh Browning in Louisiana.
  • High salinity marshes of near-Gulf waters seemed most highly affected.
  • Selective vegetative resistance to the disese was noted with Spartina alterniflora, or smooth cord grass being the only plant affected.
  • Affected areas seemed to demonstrate a browning of the Spartina often followed by complete vegetative failure which affected both above ground and below ground plant viability and seemed to follow an interior marsh genesis.
  • Many of the affected sites were characterized by either excessive submergence (water logging) or excessive dryness (desiccation).
  • Soil pH of the affected marshes was typically acidic.

In Georgia, scientists collaborating with the states Coastal Zone Program and Department of Natural Resources representing the organizations listed below, mobilized a collective research approach through a venue provided by the Georgia Coastal Research Council. With limited funding, the concerned agencies developed an integrated research approach which led to the development of a standard monitoring protocol. The monitoring effort includes simultaneously acquired, seasonal data, submitted from several affected sites around the state, which is collated toward characterizing Georgia's Marsh Die Back (MDB) phenomena. Parameters monitored are vegetation type, stem density, pore water pH, temperature, salinity and macrofaunal abundance. For more information on Georgia's research efforts view the Marsh Die-Back Index pages.

  • The Sapelo Island National Estuarine Research Reserve
  • The Georgia Coastal Research Council
  • The Georgia Department of Natural Resources: Coastal Resources Division
  • The University of Georgia School of Marine Programs
  • Savannah State University
  • The Georgia Coastal Ecosystems Long-Term Ecological Research initiative

    Much of the information provided by researchers in both states hold striking similarities in conditions associated with the onset of the disease. To date, a cause and effect relationship has not been established for individual or combinational factors due to the complexity that open systems such as salt marshes present to environmental scientists. Most scientists participating in the research and information exchange related to the disorder agree that combinations of environmental and biological factors are likely the culprits.


    Furthermore, as each system has different and unique environmental gradients and biological constituents, it is likely that the expression of the disorder assumes a unique form within each state's marshes. One overriding environmental theme common to both states occurrence of the disease is drought.

    Dr. David Stooksbury , Georgia's state climatologist analyzed rainfall data for the state from 1924- current and noticed that for four consecutive years preceding the expression of MDB, the Altamaha watershed had an average compounded rainfall deficit of approximately 5" or 10% annually.

    Stooksbury noted that the combined or cumulative effect of this type of drought has tremendous potential to serve as a forcing mechanism upon vegetation declines. Dr. James Morris of South Carolina, a scientist specializing in Spartina alterniflora responses offered concurring information based upon his research.

    Morris's work demonstrates that although Spartina alternifora is the dominant vegetation of southeastern salt marshes it is highly stressed by thermal (heat) gradients found within these lower latitudes. In fact, the marshes of Georgia and the Northern Gulf coast effectively constitute the southern range limit of the plant.

    Morris has documented that Spartina alterniflora from Northeast coastal areas is much more efficient at absorbing photosyntheticly active radiation (PAR). Simply stated, Spartina is best adapted to a cool climate, and summer temperatures in the southeast are higher than its optimum temperature. Coupling Morris's information with that of Stooksbury it is plausible that heat stress in combination with prolonged drought (desiccation stress) and high salinities have collectively created a physio-chemical interaction that is lethal to Spartina alterniflora under certain environmental conditions such as drought, in areas close to its southerly limits.

    Many other theories and combinations of theories have been discussed and researched within scientific circles ranging from herbivory to soil and pore water chemistry. The reason for the occurrence of such a catastrophic disease within our Southeastern marshes is alarming and still poorly understood however, it has promoted some unique applied work that has application to many different aspects of coastal management.

    One such product is the technology and methods developed by Louisiana's Department of Agronomy that conducted large-scale restoration of Spartina alterniflora in marsh settings by aerial seeding.

    Mike Materne, the project leader conducted experimentation in two impacted marshes and accomplished successful aerial seeding restoration projects complete with cost analysis, expected germination rates, optimum seed dispersal density and deployment methodology. This project developed new restoration tools for Spartina alterniflora establishment and as such is a landmark agronomy study with far reaching future potential to coastal restoration and management.

    Regardless of your use of terms, the causal factors of Marsh Die Back or Marsh Browning remain largely unknown. Salt marsh ecological studies driven by concern over the heath of our valuable coastal systems continue in both states. The products of these scientific efforts have allowed for a more comprehensive understanding of issues related to the disease and the production of management tools which may someday help in controlling, minimizing and understanding the effects and genesis of this disorder.
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