Aquatic Vegetation in MD's Coastal Bays

Marine flora, which include bay grasses and algae (macro and micro), play an important role in the coastal bays environment. These marine plants are considered to be the base of the food chain since they are the aquatic primary producers, organisms that can transform unusable energy (inorganic carbon) to food that other organisms can digest (organic carbon) through the process of photosynthesis. As a by-product of photosynthesis, algae produces oxygen which is very important in the aquatic environment because all animals that live in water need oxygen to survive, just like humans. Some algae may act as buffers between the land and the sea.

Coastal Bay News
Living Resources Info:
Horseshoe Crabs
Bay Grasses
Volunteer Data
Coastal Bays Home
Bays & Streams Home
DNR Home

Bay Grasses

Bay grasses (technically known as Submerged Aquatic Vegetation or SAV) are rooted plants that resemble terrestrial plants, but live and grow completely under water up to the water surface. The stems and leaves of bay grasses are supported by the water that surrounds them as they lack tissues for structural support. The leaves and stems also contain specialized thin-walled cells with large intercellular air spaces that provide additional buoyancy and support to the plants. The leaves and stems lack a waxy covering that is present in most terrestrial plants. When bay grasses are removed from the water it will dry out quickly and die. They have a complex vascular system and obtain their nutrients from the soil via the root system and from the water column.

Two species, eelgrass and widgeon grass, are common to the Maryland Coastal Bays.


Algae are generally divided into macroscopic (seen by the human eye) and microscopic. Microscopic algae, generally referred to as phytoplankton, are a diverse group. Phytoplankton are the basis of most aquatic food chains, and are one of the primary producers of oxygen in the water columns that support other aquatic life. They are also responsible for many of the harmful algal blooms that are toxic to aquatic organisms and, in some cases, humans.

Macroalgae, also known as seaweeds, are commonly found in coastal waters worldwide. They are large plant like structures that are seen with the naked eye. They appear in a variety of colors and forms. They can appear as small "fur like clumps", moderate-sized branched specimens, or large leaf-type structures. There are three general groupings that are based on the color of the plant - red, brown and green macroalgae. They are photosynthetic, using chlorophyll to synthesize their food. Macroalgae absorb nutrients from the water, and are good regulators of nutrients in the water column. However, in the summer when the water temperature increases, they tend to die back because the microscopic algal abundance increases, and they are unable to compete for nutrients with these smaller more efficient algal forms.

Though they are related to the microscopic, toxic, bloom-forming algae, macroalgae do not cause toxic water conditions. In fact, some species are a desirable delicacy in some parts of the world, and others are commercially harvested and used as food additives and for medical applications.

A survey conducted over the past two years in the Maryland Coastal Bays, revealed that there are 24 genera found in the coastal bays. The most common of these include the red alga, Agardhiella spp. and Gracilaria spp. These species are common in coastal waters, and have been shown to be beneficial habitat for small fish and invertebrates.

However, like all good things, an excess of algae can become problematic for boaters (prop fouling) and for other aquatic life.  If large amounts of algae die in a short period of time, decompostition will lower dissolved oxygen in the water, possibly low enough to kill fish.  This can particularly be a problem in dead end canals.

If you have any questions about Maryland's Coastal Bays, 
please feel free to e-mail, Cathy Wazniak, or call (410) 260-8638.

Search Maryland DNR


Water Quality | Harmful Algae | Living Resources
Bay Life Guide | Restoration & Protection | Coastal Links

Return to the Maryland DNR Home Page.
Your opinion counts! Take a