Port Royal Sound –Water Quality

There are five important steps to protecting water quality in Port Royal Sound:

1. Prevent sediment from washing into local marshes and tidal creeks by maintaining sediment fences at construction sites.
2. Retain storm water so that it reaches the marsh at slow, continual rates rather than sudden large amounts.
3. Follow printed instructions when applying pesticides and nutrients.
4. Maintain vegetative buffers along marsh edges to prevent sediments and pesticides from reaching the marsh.
5. Maintain septic tanks as scheduled.

Potential Water Quality Issues

Compared to other coastal areas, Port Royal Sound still has excellent water quality.  To its advantage, it does not receive pollutants from upstream rivers and -until recently - the uplands surrounding its marshes were covered with forests.

The presence of coliform bacteria has been the most widespread and well-studied water quality issue in Beaufort County.  Coliform bacteria originate from the digestive tracts of waterfowl and mammals, including humans.  The SC Dept of Health and Environmental Control (SC DHEC) uses elevated levels of coliform bacteria in the water to determine whether a waterway has been contaminated by bacteria from a septic tank drainage field. 

When levels of coliform bacteria exceed 40 colonies per milliliter, SC DHEC closes oyster beds in the area.  Oysters are such highly efficient filter feeders that they filter even very small bacteria from the water.  The presence of elevated coliform bacteria levels may indicate that other disease-causing bacteria such as diphtheria or cholera might also be present.  Some oyster beds are closed permanently because they are located near a known source of pollution, such as a heavily developed area with an outfall of a sewage treatment plant.  Some marshes bordered by rural developments may be closed after heavy rainfall events because of the increased likelihood of bacteria being washed from the soil into the marsh.

In 1994 the closure of the oyster beds in Broad Creek at Hilton Head initiated a local group of interested citizens called the Clean Water Task Force.  This group worked with state agencies to create the Beaufort County Special Area Management Plan, which included specific recommendations that were adopted by Beaufort County in 2000.

Other Potential Threats to Water Quality

Large amounts of stormwater runoff into the upper sections of tidal creeks can cause rapid drops in salinity, which kills some species of small marine worms and crustaceans.  These small marine animals are important food for shrimp and larval crabs. A decrease in the abundance of these animals could therefore have a negative impact on larger animals.  Effective retention of stormwater from large paved areas is required to prevent this negative impact.

Pesticides pose a potential threat to some marine organisms in Port Royal Sound.  Pesticides such as fipronil and bifenthrin bind to sediment particles and are not soluble in water.  These pesticides can enter waterways, however, if contaminated sediment washes into the marsh.  Currently, the potential threat of pesticide pollution to the marshes of Port Royal Sound is not known.

Nutrients - especially nitrogen and phosphorus - can cause water pollution in some waterways, but in Port Royal Sound this is not likely to be a threat.  In Port Royal Sound soils are naturally high in phosphorus due to marine deposits and the availability of nitrogen, rather than phosphorus, usually limits growth.  Unlike freshwater ponds and rivers, the high-saline salt marsh has the ability to uptake large amounts of nutrients because the large tides mix and disperse these nutrients which are quickly taken up by Spartina alterniflora, the most saltmash grass.  Also, detritivores (detritus-consuming animals) are abundant and much of the marsh is exposed to the air daily. 

Copper can be highly toxic to crustacean larvae in certain forms.  This is why copper paint is used on the bottom of boats to prevent barnacles (which are crustaceans) from attaching.  The toxicity of copper depends on its chemical form, which is determined by the relative hardness of the water.  Toxic levels of copper are most likely to occur in or near marinas, but there have not been any cases documented in the Port Royal Sound area.

Arsenic and Lead pose potential serious health hazards if taken up by aquatic organisms because they accumulate in tissues.  These compounds, however, tend to stay bound to sediments.  An accumulation of arsenic was discovered in soils near the base of the McTeer Bridge in Port Royal at the former site of a fertilizer plant from the early 1900’s.  These soils were subsequently removed.  The most common human sources of lead are remnants of atmospheric lead from the twentieth century when lead gasoline was used and spent lead ammunition in marshes where thousands of rounds of ammunition were fired.  Currently, there are no documented cases of contamination of marine food webs from either of these two substances.

Contaminants from parking lots and roads include derivatives of oil (PAH’s) and zinc from tire wear.  Oil contaminates ground water making it unusable for drinking water.  Chemicals created by the breakdown of oil and other hydrocarbons bind to soil and can be carried into the marsh with sediment.  These byproducts are toxic to marine life only at high concentrations, but they can accumulate in the soil.  Elevated levels of zinc have been recorded in other aquatic systems near roadways but the levels were not high enough to have a negative effect on the health of marine life.

Water Pollutants not of concern in Port Royal Sound

PCBs and dioxin are both known water pollutants that are not present in Port Royal Sound.  PCBs occur in rivers with a history of industrialization, such as the Savannah River and Charleston Harbor.  Dioxins are created by pulp mills, such as those on the Savannah River and the Sampit River in Georgetown.  Since Port Royal Sound has never had industrial sites or pulp mills, it is free of these problems.