About Bay Grasses Maryland Dept of Natural Resources
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What are Bay Grasses

Bay grasses or submerged aquatic vegetation (SAV) are vascular plants that live underwater and are found through-out Marylandís tidal and non-tidal waters. Approximately fifteen varieties of bay grasses are typically found in the Chesapeake Bay and surrounding bodies of water. Unlike terrestrial plants which have rigid stems and leaves, bay grasses have specialized cells which provide buoyancy in the water environment. Bay grasses serve many important ecological roles such as improving water quality, providing food and shelter for other species as well as stabilizing sediment at the bottom of the water column.

Recent declines in water quality in the Bay caused by excess nutrients and sediment has caused significant losses of bay grass populations. Because of their importance, the restoration of bay grasses in the Chesapeake and Coastal Bays is a priority for Maryland DNR as well as the other Bay partners.


Importance of Bay Grasses

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graphic showing the importance of bay grasses

  • Generate food and habitat for waterfowl, fish, shellfish, and invertebrates.
    Many components of the plant structure such as seeds, tubers, and even the leafy vegetation are a major source of food for a variety of organisms around the bay. The leaf and stem structures of bay grasses also provide excellent habitat and nursery sites for species such as killifish and minnows. Softshell crabs are known to seek cover in grass beds during their time of vulnerability.
  • Release oxygen During photosynthesis, plants utilize sunlight and water to convert carbon dioxide (CO2) from the atmosphere into organic material that can be used by the plant. Oxygen, essential to other underwater organisms such as fish, is a byproduct of this process.
  • Inhibit wave action that erodes shorelines. In healthy bay grass beds, dense plant structures including leaves, stems, reduce water currents and root systems hold bottom sediments in place.
  • Remove sediment from the water column. Inhibiting wave action allows bay grasses to filter and trap sediment from the water column that would otherwise bury organisms on the bottom and cloud the water column.
  • Absorb excess nutrients. During photosynthesis, Plants utilize sunlight and water to convert carbon dioxide (CO2) from the atmosphere into organic material that can be used by the plant. During photosynthesis plants require the uptake of nutrients, nitrogen and phosphorus in particular, that may fuel the growth of unwanted algae in surrounding water.

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Factors Affecting Growth of Bay Grasses

graphic showing factors that affect the growth of bay grasses

  • Available Light Light is the single most important factor affecting bay grass growth. Photosynthesis, the process whereby plants convert carbon dioxide (CO2) from the atmosphere into a useable form of energy, is a light dependent process. Therefore, there must be adequate light reaching the bottom of a body of water for bay grasses to grow. In areas with high concentrations of suspended solids and algae, almost all available light is absorbed or scattered preventing growth of bay grasses.

  • Nitrogen and Phosphorus Like all plants, bay grasses need a certain amount of nutrients including nitrogen and phosphorus to grow. However, excess nutrients can cause adverse effects and bay grasses can suffer as a result. Plant and animal matter (including human waste), fertilizer, and even deposition from car exhaust contribute nutrients to the bay. The excess nutrients promote the growth of algae in the water column, which reduce or block the amount of light available for bay grass survival.

  • Algae Nutrients encourage the growth of plants. However, excess nutrients can cause increases in algae, microscopic floating plants. Where there is too much algae, the water becomes cloudy and blocks the light needed by bay grasses. Algae can also coat the leaves of bay grasses, further reducing the amount of light received by the plants.

  • Suspended Solids Small particles in the water, like silt, scatter and absorb light as they pass through the water column. These particles come from land erosion, and disturbances to the bottom of the bay. Turbidity is a measure of how clear the water is and how much the suspended solids hinder the passage of light. In areas of high turbidity, or increased suspended solids, bay grasses do not receive adequate light for survival.

  • Wave Energy Bay grasses do not typically grow in areas with heavy wave action due to bottom scouring and resuspension of fine particles.

  • Seed Source Seed sources or other reproductive structures are necessary for bay grasses to reproduce. Without a source of seed in a given area or upstream of an area, bay grasses will not exist. There are many regions within Chesapeake Bay in which habitat conditions are suitable for bay grass growth, but are currently lacking vegetation, probably due to a lack of adequate seed or propagule source. DNR is currently working to identify these places, and target them for reseeding efforts. Read more about DNR's bay grass restoration efforts.

  • Grazing Several species living in and around the bay including the cow-nose ray, mute swans, and other waterfowl can cause significant damage to bay grass populations by feeding directly on the vegetative (leaves and stems) and reproductive (seeds and propagules) structures of bay grasses. A single adult mute swan has been know to consume 8 pounds of bay grass a day!

  • Sediment Quality Bay grasses require sediment to provide mechanical support of roots and sufficient nutrients. Although preferences for particular sediment type varies among species, most prefer more stable sediments composed of sand or mud with low organic matter content.

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