Chesapeake Bay National Estuarine Research Reserve

Monitoring the Deal Island Impoundment at Monie Bay

​​Deal Island Impoundment. Photo credit: P. Delgado

The Deal Island Impoundment is a 2,800 acre man-made “pond” built in the 1960’s within the Deal Island Wildlife Management Area of the Lower Eastern Shore of Maryland to support waterfowl. This impoundment consists of large expanses of marsh, frequently broken by open water, forming ponds of different sizes. These ponds are often colonized by submerged aquatic vegetation or underwater grasses (SAV), particularly widgeon grass (Ruppia maritima), which provides a valuable food source to waterfowl. Over the past 25 years, changes have been observed in the impoundment including increased water levels and flooding, marsh vegetation decline, and decrease of SAV abundance and species diversity. SAV decline has particularly occurred in the biggest pond of the impoundment known as “Main Pond” or “Big Water.”

In an effort to better understand the observed decline, CBNERR-MD in collaboration with the Maryland Department of Natural Resources’ Wildlife and Heritage Service started in 2008 a comprehensive monitoring effort involving the sampling of marsh vegetation, SAV, and water quality. Two ponds are currently being monitored within the impoundment: Main Pond and Snag Pond.

Marsh plants and SAV are currently being surveyed along five transects established within each Main and Snag Ponds. Marsh transects are sampled once during the growing season using the Point Intercept method, which provides information on species presence (diversity) and their ground cover. Other parameters measured include number of individuals per species (density) and species maximum height. SAV transects are sampled three times a year during the growing season: June, August, and October using a 0.25 m2 quadrat. An aquascope is used to visually estimate species cover; plant maximum height is also measured. Water quality is sampled once a month (April-October) at one station in two of the SAV transects per pond. At each station readings of water temperature, oxygen level, and salinity are taken using a handheld YSI instrument. Total water depth is also recorded. Water is then collected and filtered to be sent to a laboratory for nutrient analyses. Some of the nutrients that are analyzed include ammonium (NH4), nitrate (NO3), phosphate (PO4), total nitrogen, and total phosphorus; other analyses are done for total suspended solids and Chlorophyll a (an indirect measurement of the amount of algae in the water).

Sampling marsh plants and SAV at Deal Island Impoundment. Photo credit: B. Ebersole and P. Delgado 

Monitoring water quality at Deal Island Impoundment. Photo Credit: P. DelgadoThe main objectives of this project are to:

  1. Better understand the current degradation of the marsh and underwater grass communities within the Deal Island Impoundment.
  2. Promote the use of long-term monitoring data to evaluate change at the Deal Island Impoundment.

Results from this experiment would be used to better inform management and any restoration efforts in the Deal Island Impoundment.

How to Get Involved:

If you are interested in helping with our monitoring efforts at our Monie Bay component please contact Stewardship Coordinator, Chris Snow ( Activities include, but are not limited to: barn owl box and water quality monitoring, secretive marsh bird surveys, water trail maintenance.

Available Information:

If you are interested in obtaining data collected through these efforts, please contact Stewardship Coordinator, Chris Snow (


Sampling marsh vegetation at Jug Bay (Credit: L. Carroll)

Our Science

Explore and learn about the interesting research and long-term monitoring projects we are conducting at Otter Point Creek (Bush River), Jug Bay (Patuxent River), and Monie Bay (eastern shore). Our projects range from water quality monitoring to marsh plants to monitoring secretive marsh birds and fish.​​​​​


Links to Our Data

Our Data

We invite you to use our data to support research, modeling, management, and/or education goals. Our data could serve as baseline information to start a new research project, to look for interesting trends, to support modeling efforts, or to complement a project already in progress. We hope our data can help you to make a difference!