Marine Pollution Bulletin 64 (2012) 1356–1366 Contents lists available at SciVerse ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Pollutant impacts to Cape Hatteras National Seashore from urban runoff and septic leachate ⇑ Michael A. Mallin , Matthew R. McIver Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC 28409, United States article info abstract Keywords: The sandy barrier islands of Cape Hatteras National Seashore, USA, attract large seasonal influxes of tour- Barrier island ists, and are host to numerous motels, rentals and second homes. To investigate the impacts of nearby Septic system urbanization on public trust waters, sampling was conducted in nine brackish water bodies within this Fecal bacteria coastal national park. A large tidal urban ditch delivered runoff-driven fecal-contaminated water directly Nutrients into public beach waters. At all sites except the control, ammonium, phosphorus and fecal bacteria con- Algal blooms centrations were high, strongly seasonal and significantly correlated with community water usage, indi- Hypoxia cating that increased septic tank usage led to increased pollutant concentrations in area waterways. Nutrients from septic systems caused ecosystem-level problems from algal blooms, BOD, and hypoxia while fecal microbes created potential human health problems. Septic system usage is widespread in sen- sitive coastal areas with high water tables and sandy soils and alternatives to standard septic systems must be required to protect human health and the environment. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction scientific, management, and political communities. One such area where urban impacts can have direct impacts upon undeveloped Protected coastal areas, such as national, state, provincial or lo- adjoining areas is Cape Hatteras National Seashore (CAHA) located cal parks offer public opportunities for relaxation, recreation, and along the Outer Banks of North Carolina, USA. nature appreciation. Under idealized conditions these areas also South Bodie Island is a barrier island that forms the northern- present researchers with a rich variety of terrestrial and aquatic most section of Cape Hatteras National Seashore (Fig. 1). The park habitats for study under (relatively) unimpacted conditions. How- wetlands in the area contain significant fresh and brackish water ever, some of these parks have suffered from impaired water qual- resources (Cole and Bratton, 1995; Mallin et al., 2006a). Adjoining ity from adjacent or upstream human sources, especially CAHA is the Town of Nags Head, with a residential area extending agriculture. One example is the Everglades National Park in Florida, south along the seashore next to CAHA for about 7.3 km (Fig. 1). which receives fertilized runoff and other pollutants from agricul- This part of Nags Head is zoned R-2, or medium density residential ture, primarily from sugar cane farming adjacent to the parklands (Stone Environmental Inc., 2005); dwelling density near the beach (Lapointe and Barile, 2004; Sheikh and Johnson, 2004; Perry, 2008). in Nags Head averages 7.5 units/ha or 3 units/acre (Town of Nags Cumberland Island National Seashore in Georgia is an example of a Head, 2000). Nags Head seasonally has high summer visitor usage, coastal park whose adjacent waterways are impacted by municipal and sewage treatment in the area abutting the park consists of and industrial point-source discharges, as well as non-point source septic systems. The soils in this area of Nags Head are primarily fertilizers and animal waste, from upstream municipalities and highly permeable sands while the water table in this area is mainly agricultural areas in the Satilla and St. Mary’s River basins (Alber 0–1 m from the surface (Stone Environmental Inc., 2005). This et al., 2005). Nearby urbanization is also a potential pollution combination of geological and hydrological factors can lead to inef- sources for coastal parks. With the rapid human urbanization of fective treatment of human sewage by septic systems (Cogger et al., coastal zones in recent decades (Crossett et al., 2004; US EPA, 1988), which require between 2 and 5 feet (0.6–1.5 m) of aerated 2004) areas where protected land and waterscapes are in direct soil (the vadose zone) beneath the septic drainfield to completely contact with already-developed or urbanizing situations can pres- treat the pollutants in sewage (US EPA, 2002). Otherwise, pollutants ent case studies from which the impacts of such encroachment on such as fecal bacteria and nutrients (nitrogen and phosphorus) can natural areas can be assessed and (hopefully) learned from by the enter the upper groundwater table and move laterally up to several hundred feet until they enter surface water such as a ditch, pond, tidal creek, bay or sound (Lipp et al., 2001a,b; US EPA, 2002). Evans ⇑ Corresponding author. Tel.: +1 910 962 2358; fax: +1 910 962 2410. E-mail address: [email protected] (M.A. Mallin). and Houston (2000) reported that septic leachate from drainfields 0025-326X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpolbul.2012.04.025 M.A. Mallin, M.R. McIver / Marine Pollution Bulletin 64 (2012) 1356–1366 1357 Fig. 1. Map of sampling sites on South Bodie Island, Cape Hatteras National Seashore, North Carolina, USA. Upper panel – northern area; lower panel – southern area. in Nags Head increased nitrate concentrations in downslope nitrate concentrations that exceeded the US Environmental groundwater wells, with the wells nearest the drainfields having Protection Agency drinking water standard of 10 mg/L. 1358 M.A. Mallin, M.R. McIver / Marine Pollution Bulletin 64 (2012) 1356–1366 A ridgeline passing north to south through Nags Head delineates The main drainage ditch along Old Oregon Inlet Road in Nags the drainage direction (Evans and Houston, 2000; Fig. 1). Water Head collects urban runoff surface drainage (and possibly shallow (surface runoff and upper groundwater) moves from the ridgeline groundwater) and conveys it into a beachfront outfall adjacent to in Nags Head into a series of drainage ditches and tidal creeks that CAHA property at Ramp 1 (Fig. 1). Elevated Enterococcus bacteria run perpendicular to Old Oregon Inlet Road and flow westward, counts in the vicinity of the discharge into the beach water have pass under Highway 12, and drains into Roanoke Sound (Fig. 1). necessitated frequent beach swimming advisories by the N.C. In a comparison of ditch water quality and marsh sites within Shellfish Sanitation group (Stone Environmental Inc., 2005; Mallin CAHA west of Nags Head, Cole and Bratton (1995) found that drain- et al., 2006a). The urban ditch supports large surface algal blooms age ditches had significantly higher nutrients and fecal bacteria, and dense mats of free-floating and loosely-attached aquatic mac- but lower dissolved oxygen, than the marsh sites. East of the ridge- rophyte vegetation mats. line, much of the surface runoff in the part of Nags Head adjoining Wetland ponds occur throughout the area (Fig. 1). Some are CAHA flows into a 5 m wide ditch that parallels the west side of Old connected to the drainage system, while some are well away from Oregon Inlet Road. This ditch flows south and enters the ocean at an obvious urban drainage. These ponds are critical to area wildlife, outfall at Ramp 1 of CAHA beach property (Fig. 1). High fecal and water quality of the ponds affects the fish and other biota. bacteria counts from this outfall pollute the beach and have led Thus, selected potentially-impacted and control ponds were sam- to beach postings and closures by the N.C. Shellfish Sanitation Sec- pled to assess and compare their water quality. tion (Mallin et al., 2006a). This large drainage ditch also hosts dense algal blooms and macrophyte coverage, suggesting inputs of 3. Methods nutrients. Thus, stormwater runoff, as well as septic leachate, was considered a potential problem impacting adjacent public areas. 3.1. Sampling sites Development has continued in Nags Head (as well as in other municipal areas adjoining CAHA property on barriers further Sampling was conducted at the five drainage ditches (D-1 south); thus comprehensive water quality information was needed through D-5) where they intersect Highway 12 (Table 1; Fig. 1). to assess potential anthropogenic inputs on these drainage systems Additionally, the main drainage ditch along Old Oregon Inlet Road and associated natural areas. We hypothesized that: (1) based on (UR-D) was sampled before it is piped under the road and into the previous data, topography and local hydrology, elevated pollutant beach water at Ramp 1. Three ponds were sampled (Table 1; loads were draining from the adjacent urbanized areas into Fig. 1): the first is an urban pond (UR-P) that during rain events ac- ditches, tidal creeks, wetlands and beach waters on CAHA property, cepts surface runoff from the roads, lies on both town and park either through overland runoff or septic system leachate, (2) these property and is hydrologically connected to the ditches that flow pollutants were likely leading to associated ecosystem impacts across the island. The second (C-P) is on the west side of Highway caused by such pollutant loads, and (3) such pollutants also pres- 12 with no apparent hydrological connection to the ditches, and ent a human health problem to park users. To investigate these was considered a control pond. The third pond (WW-P) is within hypotheses we obtained physical, chemical, and biological water NPS property and located about 25 m west of Highway 12 (Table 1; quality data for tidal creek/ditch and brackish pond sites on, or Fig. 1). It is tidally influenced and there is evidence of considerable impacting NPS property in the South Bodie Island area adjoining wildlife usage in the immediate area, with well-worn trails and northern Cape Hatteras National Seashore.