Waterfront Property Stewardship II - Nutrification

(Published June 2001)

In addition to the cardinal rule of never throwing anything into the water, there are many other actions that waterfront property owners (and others) can take which will improve our local waterways:

Keep the shoreline clean. Remove all litter, as well as excess leaves and branches.

If there is a marsh adjacent to your property, do a bit of “marsh gardening”. Your marsh needs care just like your shrubs and flowers. Remove logs and large branches to open up space for the grass to grow. Most important, prune all overhanging limbs and brush to allow light to penetrate. Healthy marshes require full sunlight in order to perform several extremely important roles. Marshes are the most productive ecosystems on the planet and provide food and habitat for many juvenile organisms of both commercial and recreational value. The roots (called rhizomes) of marsh grasses also retard erosion. Marshes have been called "nature's kidneys". In addition to trapping sediment, marshes also literally destroy nitrate. The bacteria which convert dissolved nitrate into nitrogen gas (a process called denitrification) require a unique set of circumstances. Denitrifying bacteria can only function under anoxic (or no-oxygen) conditions such as exist in the black organic-rich mud in the marsh. Here the nitrate from excess fertilization and from our septic systems enters the marsh by both runoff and groundwater discharge, and is converted into harmless nitrogen gas before the nitrate can enter the water and promote the growth of suspended algae.

Encourage marine grass growth along the margins of creeks by pruning limbs that overhang the water. You accomplish three useful things by this simple act. First and foremost, with the limbs gone, more light can penetrate so the marine grasses won’t be shaded out. Second, the reduced weight of limbs toward the water will slow the tipping of the tree. And finally, you will reduce the number of leaves, needles and branches that enter the water. Less organic matter in the water means less oxygen will be consumed as bacteria decompose it, and fewer nutrients will be released to the water by the bacterial decomposition process.

Expand marine grass growth along your shoreline by transplanting grasses in May. Single plants or small clumps of plants with adequate root mass can be taken from lush marshes (with permission, of course), or they can be bought (contact SEAS, the Shoreline Erosion Advisory Service at (804) 443-3803 or http://www.dcr.virginia.gov/soil-and-water/seas for the names of suppliers). The common “smooth cordgrass”, Spartina alterniflora, should be planted in intertidal zones on about 2 foot-centers. A pinch of a slow-release fertilizer will get the plants off to a good start.

Prevent shoreline erosion and don't allow soil and dirt to run into the water off your property. Sea level is rising about 4 millimeters (3/16 inch) each year in Northumberland County (2 inches each decade, or over a foot in your lifetime). Rising sea level, along with boat wakes, is the reason why so many trees are toppling into the water and the edges of our marshes are eroding. Sediment from the eroded creek margins causes the creeks to shoal up, and smothers bottom dwelling organisms like oysters. SEAS will be glad to give you free advice about how to best combat erosion on your property.

Always proceed at No-Wake speed if you are boating in restricted waterways so as to minimize erosion. Never make waves larger than Nature makes. Open your throttle(s) in the open Bay, not in the creeks and narrow rivers. Owners of personal watercraft should enter small creeks at idle speed only. Wakes from fast-moving (and noisy!) watercraft create waves much larger than are generated during the largest storms, and are major causes of both marsh and bank erosion in our small creeks.

Grow oysters in floats. Oysters feed by filtering small organisms out of the water, which cleanses it. If the water can be made clearer, light can penetrate to the bottom of the waterway and sub-aquatic vegetation (SAV) can establish itself. Like intertidal marsh grasses, SAV increases the oxygen content of the water, provides habitat for organisms of commercial and recreational value, and retards erosion. Many local creeks once had plenty of oysters, and maybe they will come back if: (1) more breed stock is present in floats, especially if the breed stock is resistant to the two diseases which kill adult oysters, (2) undisturbed substrate is available (or made available - thick piles of oyster shell over old “reefs” are best), (3) bank erosion is curtailed, and (4) nutrification of the creeks is reduced. To get involved in "oyster gardening" contact

TOGA (Tidewater Oyster Gardeners Association) at www.oystergardener.org.