Background

    Seagrass mapping data from a multitude of previous projects in the Mississippi and Chandeleur Sounds were gathered and combined to provide information on seagrass change from 1940 to 2011.

A Brief History of Seagrass Observations and Mapping

• • Widgeongrass (Ruppia) was noted to occur in the Chandeleur Sound in 1900 (Lloyd and Tracy, 1901).

• Submerged flowering plants (Thalassia, Halodule, Halophila) were reported in the MS Sound as early as the 1950s (Humm and Caylor, 1955; Humm, 1957).

  • The first map of MS Sound seagrass was published (Eleuterius, 1973) based on fieldwork conducted during the spring and summer of 1969.

• Eleuterius included seagrasses in his 1978 vegetation maps of Horn and Petit Bois Islands.

• The United States Geological Survey – National Wetland Research Center (USGS-NWRC, 1998b) published a map of SAV in MS by interpreting June 1992 natural color aerial photography.

• Moncreiff et al. (1998) published the first report on changes in seagrass area and potential seagrass habitat in MS with a a decline in seagrass area from 5252 to 809 ha.

• Moncreiff (2007) provided an update in the USGS Gulf of Mexico Seagrass Status and Trends, and suggested a slow increase in seagrass area throughout the MS Sound between 1992 and 1999.

• Peneva et al (2008) developed a technique to analyze high resolution imagery for seagrass vegetation classification on Horn Island.

• The vegetated seagrass area on the MS barrier islands spanning the 1940-2007 period was mapped and then recalculated by Carter et al (2011) from analysis of high-spatial-resolution imagery.

• Pham et al (2014) updated and collated all previous mapping data to provide a more comprehensive regional analysis of seagrass change for the MS and Chandeleur Sounds.

    The following are some examples of these various mapping efforts made by various investigators and using a variety of different mapping techniques. Note that direct comparisons of seagrass area among these various studies that used different mapping methods can result in overestimation of area change and misleading conclusions.

1. Eleuterius first provided a map of seagrasses in Mississippi Sound from data collected during the summer of 1969:

3. Moncreiff and others provided the first maps comparing seagrass extent across decades (1969 vs 1992):

4. Moncreiff (2007) updated the previous map to include additional data from 1999:

5. Resource managers at the Grand Bay National Estuarine Research Reserve provided an updated map of seagrass after Hurricane Katrina (2006-2009):

6. Pham and others collated previous mapping data and developed a comprehensive GIS dataset for MS and Chandeleur Sounds:

Below are copies of original reports and a presentation summarizing this information given in 2011 at the Submerged Aquatic Vegetation and Seagrass workshop.