Case Study 3 1960_book.fm Page 117 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC 119 4 Delaware National Estuarine Research Reserve INTRODUCTION The National Oceanic and Atmospheric Administration (NOAA) designated the Delaware National Estuarine Research Reserve (DNERR) as a National Estuarine Research Reserve System (NERRS) program site on July 21, 1993. The DNERR consists of two well-deÞned component sites about 32 km apart (see Figure 4.1): 1. The Lower St. Jones River Reserve site located south of Dover in east- central Kent County, Delaware 2. The Upper Blackbird Creek Reserve site located between Odessa and Smyrna in southern New Castle County, Delaware Both the Lower St. Jones River Reserve site and the Upper Blackbird Creek Reserve site are subestuaries of the Delaware River estuary. Tidal marshes and tidal streams comprise the primary habitats of both reserve sites. The Lower St. Jones River Reserve site covers a 1518-ha area along the lower 8.8-km portion of the St. Jones River watershed. Here, agricultural land use pre- dominates in the watershed. The St. Jones River stretches for 16.8 km across the Delmarva Peninsula, and it discharges to the mid–Delaware Bay zone. The Trunk Ditch, Beaver Branch, and Cypress Branch are the largest tributaries of the Lower St. Jones River, which is characterized by mesohaline salinity conditions. The lower boundary of the reserve site extends 3.2 km into the open waters of Delaware Bay; it encompasses a 1036-ha area of subtidal bottom. The Upper Blackbird Creek Reserve site, which covers an area of 477 ha, lies ~9.0 to 18.5 km upstream of the Blackbird Creek mouth. This site is characterized by low salinity brackish or freshwater tidal creek habitat. Woodlots, croplands, and upland Þelds also occur within the designated boundaries of the reserve. Forested wetlands with coastal plain ponds blanket much of the land area upstream of the reserve site, notably in the Blackbird State Forest. Forested and agricultural land cover dominates much of the Blackbird Creek watershed. Extensive tidal mud ßats and Spartina marshes border Blackbird Creek bayward of the Beaver Branch trib- utary in the upper creek segment. This chapter provides an overview of the DNERR based in large part on pub- lished reports of the Delaware Department of Natural Resources and Environmental Control (1993, 1994, 1995, 1999) and the U.S. Environmental Protection Agency (Dove and Nyman, 1995; Sutton et al., 1996). The estuarine proÞle of the DNERR is a particularly important source of information on the reserve. 1960_book.fm Page 119 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC 120 Estuarine Research, Monitoring, and Resource Protection LOWER ST. JONES RIVER RESERVE SITE W ATERSHED More than 50,000 people reside in the 233-km 2 area of the St. Jones River watershed. Development is greatest in the middle and upper watershed, being highly concen- trated in the urbanized area of Dover, Delaware. Considering the entire St. Jones River watershed, approximately 48% of the land use cover is agriculture, 25% developed, 14% wetlands, 10% forested land, and 3% open water. Impervious land cover in the watershed amounts to nearly 25%. Within the reserve area, most of the FIGURE 4.1 Map of the Delaware National Estuarine Research Reserve showing the location of the Upper Blackbird Creek and the Lower St. Jones River DNERR sites. (From the Delaware Department of Natural Resources and Environmental Control. 1999. Delaware National Estuarine Research Reserve: Estuarine ProÞles. Technical Report, Delaware Depart- ment of Natural Resources and Environmental Control, Dover, DE.) Pennsylvania New Jersey Maryland Delaware Atlantic Ocean Delaware Bay Legend Major town Major highway DNERR Site DNERR watershed 10 0 10 20 Kilometers N Wilmington Newark Odessa Smyrna Dover Milford Lewes Georgetown River DNERR Lower St. Jones Upper Blackbird Creek DNERR 1960_book.fm Page 120 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC Delaware National Estuarine Research Reserve 121 land remains in private ownership despite the purchase of nearly 300 ha of wetland and upland habitat by NERRS in 1991–1992. The Lower St. Jones River Reserve site and Upper Blackbird Creek Reserve site occur in the Atlantic Coastal Plain and are underlain by thick layers of unconsolidated sediments and semi-consolidated sedimentary rocks. The terrane is gently sloping; relief in the Lower St. Jones River Reserve ranges from sea level to 22 m. Soils in the upland areas of both reserve sites consist of well-drained or moderately drained sandy loams to poorly drained sandy–clay loams rich in organic matter. Because tidal wetlands are extensive, tidal marsh soils predominate in large areas of the reserve. These soils are composed of clay and sand layers mixed in many places with mucky peat. They attain a thickness of nearly 30 m in the marsh habitat at the mouth of the St. Jones River (DNERR, 1999). Upland Vegetation The Lower St. Jones River Reserve site supports two types of forest communities: upland forest and tidal marsh forest. Principal species of the upland forest community are the white oak ( Quercus alba ), southern red oak ( Q. falcata ), sassafras ( Sassafras albidum ), black cherry ( Prunus serotina ), American beech ( Fagus grandifolia ), American holly ( Ilex opaca ), black haw ( Viburnum prunifolium ), and tulip tree ( Liriodendron tulipifera ). The tidal swamp forest community includes red cedar ( Juniperus virginiana ), red maple ( Acer rubrum ), black gum ( Nyssa sylvatica ), sweet gum ( Liquidambar styracißua ), green ash ( Fraxinus pennsylvanica ), and willows ( Salix spp.). Farmland, old Þelds, and mixed deciduous hardwood forests comprise most of the upland land cover. Wetland Vegetation Forested wetland vegetation, scrub forest, and scrub–marsh mixes deÞne the marsh habitat along the St. Jones River, with 66 species of plants reported (Wetlands Research Associates and Environmental Consulting Services, 1995) (Table 4.1). Mixed associations of emergent vegetation typify tidal wetland habitat of the Lower St. Jones River Reserve site. Emergent vegetation of high marsh areas exhibits greater diversity of plant assemblages than that of low marsh areas. The smooth cordgrass ( Spartina alternißora ) is the dominant species of the tidal marsh, covering 62.2% of the Lower St. Jones River Reserve wetlands area (Table 4.2). Tall-form S. alternißora grows along tide-channel banks, and short-form S. alternißora spreads across broad expanses of intertidal habitat. The big cordgrass ( S. cynosuroides ) is also found along channel edges. Marsh edaphic algae (diatoms) in the top few millimeters of marsh sediments constitute a valuable food source for Þsh and other fauna of the salt marsh system. Pickerel weed ( Ponderia cordata ), marshpepper smartweed ( Polygonum hydropiper ), and swamp rose mallow ( Hibiscus palustris ) are subdominants within the cordgrass communities. Above mean high water (MHW), salt meadow cordgrass ( Spartina patens ) and salt grass ( Distichlis spicata ) concentrate in patches, most conspicously immediately below the border areas of the upper marsh. 1960_book.fm Page 121 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC 122 Estuarine Research, Monitoring, and Resource Protection TABLE 4.1 Taxonomic List of Plants Identified in St. Jones River Marshes Common Name Scientific Name Red maple Acer rubrum Ground nut Apios americana Orach Atriplex patula Grounsel bush Baccharis halimifolia Hedge bindweed Calystegia sepium Winged sedge Carex alata Greenish-white sedge Carex albolutescens Lone sedge Carex lonchocarpa Lurid sedge Carex lurida Uptight sedge Carex stricta Bitternut hickory Carya cordiformis Buttonbush Cephalanthus occidentalis Water hemlock or spotted cowbane Cicuta maculata Sweet pepperbush Clethra alnifolia Canker root Coptis trifolia Persimmon tree Diospyros virginiana Salt grass Distichlis spicata Spikerush Eleocharis ambigens American beech Fagus grandifolia Green ash Fraxinus pennsylvanicus Common madder Galium tinctorium Manna grass Glyceria stricta Swamp rose mallow Hibiscus palustris Many-ßowered pennywort Hydrocotyle umbellata Inkberry Ilex glabra American holly Ilex opaca Winterberry Ilex verticillata Jewel weed Impatiens capensis Marsh elder Iva frutescens Black walnut Juglans nigra Red cedar Juniperus virginiana Rice cutgrass Leersia oryzoides Sweet gum Liquidambar styracißua Japanese honeysuckle Lonicera japonica Sweet bay magnolia Magnolia virginiana Yellow pond lily Nuphar lutea Black gum Nyssa sylvatica Cinnamon fern Osmunda cinnamomea Royal fern Osmunda regalis Arrow arum Peltandra virginica Common reed Phragmites australis Black bindweed Polygonum convolvulus 1960_book.fm Page 122 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC Delaware National Estuarine Research Reserve 123 Marsh shrub communities proliferate in higher marsh areas. Two types of shrub communities are evident: 1. Fresher, lower salinity tidal communities 2. Brackish, higher salinity tidal communities Woody plants dominate the lower salinity tidal communities; smooth alder ( Alnus serrulata ), winterberry ( Ilex verticillata ), buttonbush ( Cephalanthus occiden- talis ), sweet pepperbush ( Clethra alnifolia ), and dogwoods ( Cornus spp.) are plant species commonly observed here. In higher salinity tidal communities, the predom- inant marsh shrubs include the marsh elder ( Iva frutescens ) and groundsel bush Black cherry Prunus serotina Mock bishopweed Ptilimnium capillaceum Willow oak Quercus phellos Swamp honeysuckle Rhododron viscosum Multißora rose Rosa multißora Swamp rose Rosa palustris Swampdock Rumex verticillatus Saltwort Salsola kali Common elderberry Sambucus canadensis American three-square Scirpus americanus Saltmarsh bulrush Scirpus robustus Giant bulrush Scirpus validus Sawbriar Smilax glauca Smooth cordgrass Spartina alternißora Big cordgrass Spartina cynosuroides Saltmeadow cordgrass Spartina patens Skunk cabbage Symplocarpus foetides Tall meadow-rue Thalictrum pubescens Poison ivy Toxicodendron radicans Narrow-leaf cattail Typha angustifolia Broad-leaf cattail Typha latifolia Highbush blueberry Vaccinium corumbosum Northern arrowwood Viburnum recognitum Black haw Viburnum prunißoloium Source: From the Delaware Department of Natural Resources and Envi- ronmental Control. 1999. Delaware National Estuarine Research Reserve: Estuarine ProÞles. Technical Report, Delaware Department of Natural Resources and Environmental Control, Dover, DE. TABLE 4.1 (CONTINUED) Taxonomic List of Plants Identified in St. Jones River Marshes Common Name Scientific Name 1960_book.fm Page 123 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC 124 Estuarine Research, Monitoring, and Resource Protection ( Baccharis halimifolia ). Red cedar ( Juniperus virginiana ) is also evident in the brackish tidal communities. Deep-water emergents form a low-marsh mixed association along the edges of creeks and ponds. Comprising this plant association are arrow arum ( Peltandra virginica ), yellow pondweed ( Nuphar lutea ), marshpepper smartweed ( Polygonum hydropiper ), and pickerel weed ( Ponderia cordata ). Dense monospeciÞc stands of yellow pondweed occur in some areas. The common reed ( Phragmites australis ), an invasive species, inhabits fresh and brackish marshes along marsh upland borders. This nuisance species has spread most rapidly in the Upper Blackbird Creek marshes but also has been documented in more restricted areas along the upland edge and major river banks of the Lower St. Jones River Reserve site. Increasing distribution of the common reed in reserve marshes is a growing concern because this species generally degrades coastal wetland habitat values for wildlife. Efforts to control the spread of Phragmites in the DNERR have consisted of aerial herbicide spraying followed by prescribed burning. However, this species is resilient, and its persistent monotypic stands remain a target for various remedial programs. Monotypic stands of Phragmites currently cover about 10 to 15% of Delaware’s tidal wetlands (DNREC, 1993). Three other emergent wetland plant communities exist in the DNERR: Typha spp., Scirpus americanus , and Zizania aquatica communities. Although relatively TABLE 4.2 Vegetation Cover in Wetlands of the Delaware National Estuarine Research Reserve Upper Blackbird Creek Lower St. Jones River Map Unit Percent Cover Map Unit Percent Cover Spartina alternißora 28.64 Spartina alternißora 62.23 Tidal ßat 26.44 Phragmites australis 13.38 Open water 14.21 Impoundment 7.54 Phragmites australis 11.05 Open water 7.03 Spartina alternißora mix 4.74 Marsh shrub 3.63 Tidal swamp forest 4.20 Salt hay 2.37 Marsh shrub 3.64 Spartina cynosuroides 1.68 Spartina cynosuroides 2.72 Tidal swamp forest 0.92 Typha spp. 1.53 Tidal ßat 0.72 Zizania aquatica 1.09 Marsh shrub 0.43 Peltandra virginica 0.96 Typha (latifolia/angustifolia) 0.04 Ponderia cordata 0.44 Scirpus americanus 0.02 Impoundment 0.30 Atriplex triangularis 0.01 Nuphar lutea 0.04 Peltandra virginica 0.01 Scirpus americanus 0.01 Source: From the Delaware Department of Natural Resources and Environmental Control. 1999. Delaware National Estuarine Research Reserve: Estuarine ProÞles. Technical Report, Delaware Department of Natural Resources and Environmental Control, Dover, DE. 1960_book.fm Page 124 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC Delaware National Estuarine Research Reserve 125 minor emergent wetland components, these communities provide important hab- itat for a number of animal populations such as muskrats (Ondatra zibethicus) and an array of bird species. Two cattail species (Typha angustifolia and T. latifolia) have been documented in Typha communities of the reserve. The cattails may be present as monospeciÞc stands or a mixed community with a number of co-dominants (i.e., smooth cordgrass, Spartina alternißora; rice cutgrass, Leersia oryzoides; salt marsh water hemp, Acnida cannabina; and nodding bur-marigold, Bidens cernua). Emergent plants of the Scirpus community grow along brackish shorelines as either monotypic stands of the American three-square (Scirpus americanus) or a mixed community with a few other common marsh plants (i.e., Spartina alternißora, S. patens, and Distichlis spicata). Extensive monospeciÞc stands of wild rice comprise the Zizania aquatica community, which proliferates in fresh to slightly brackish water areas. AQUATIC HABITAT The lower 8.8-km section of the St. Jones River site is a medium-salinity tidal river subjected to semidiurnal tides. The mean tidal range at the mouth of the river amounts to about 1.5 m; at spring tide, however, the mean tidal range averages 1.7 m. SigniÞcant tidal range attenuation occurs upriver. The channel width of the Lower St. Jones River at the site of the reserve ranges from ~40 to 90 m. Mid-channel depths at low tide along this stretch of the river range from ~2.4 to 5.5 m. The highest current velocities are recorded in the lower segment of the river. Here, maximum current velocities observed during spring tides and neap tides are ~30 to 40 and ~20 to 30 cm/sec, respectively. The water column is relatively well mixed, with little evidence of two-layered estuarine ßow. Hence, ßow is mainly unidirectional from surface to bottom in the lower river with slight differences (10 to 20%) in current velocity observed throughout the water column. Water Quality A YSI Model 6000 data logger deployed at Scotton Landing in the middle reach of the Lower St. Jones River during 1996 recorded physical–chemical data semi- continuously (every 30 min) year-round. The water quality parameters monitored were temperature, salinity, dissolved oxygen, pH, turbidity, and depth (Figure 4.2 and Figure 4.3). The absolute temperature over the annual period at the Scotton Landing site ranged from less than 0 to 30°C. The monthly mean water temper- ature, in turn, ranged from less than 0°C in February to 25.5°C in August. The annual salinity range in the middle reach of the river ranged from ~1‰ to more than 20‰. Mean monthly salinity values ranged from ~3‰ in December to more than 12‰ in September. Waters in the Lower St. Jones River are generally clas- siÞed as mesohaline. Annual dissolved oxygen values (% saturation) varied from less than 20% to more than 120% saturation. The monthly mean dissolved oxygen, however, ranged from more than 40% in July to more than 80% in March. Hypoxic events were also 1960_book.fm Page 125 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC 126 Estuarine Research, Monitoring, and Resource Protection documented during the summer months. Absolute dissolved oxygen measurements varied from 0 to 14.9 mg/l. The monthly mean absolute dissolved oxygen values ranged from ~4 mg/l (July) to 10 mg/l (March). The mean annual dissolved oxygen value was 6.45 mg/l. FIGURE 4.2 Comparison of monthly mean water temperature, pH, speciÞc conductivity, and salinity for Blackbird Landing and Scotton Landing in 1996. (From the Delaware Department of Natural Resources and Environmental Control. 1999. Delaware National Estuarine Research Reserve: Estuarine ProÞles. Technical Report, Delaware Department of Natural Resources and Environmental Control, Dover, DE.) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 30 25 20 15 10 5 0 Temperature (C) Water Temperature Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 30 25 20 15 10 5 0 -5 Temperature (C) Water Temperature Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 8 7.5 7 6.5 6 8 7.5 7 6.5 6 pH pH Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 4 3.5 2.5 2 1.5 0.5 3 1 0 Specific Conductivity (%) Specific Conductivity Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 2.5 2 1.5 1 0.5 0 Salinity (ppt) Salinity Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 14 12 10 8 6 4 2 0 Salinity (ppt) Salinity Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 25 15 20 10 5 0 Specific Conductivity (%) Specific Conductivity Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. pH pH Blackbird Landing Scotton Landing 1960_book.fm Page 126 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC Delaware National Estuarine Research Reserve 127 The pH measurements at Scotton Landing for 1996 ranged from 6.01 to 8.87. The mean pH value for the year was 7.02. Highest pH levels were observed in March, and lowest pH levels were noted in June and July. Turbidity generally ranged from 50 to 125 NTU, with highest levels (mean ~125 NTU) registered in September. However, spiked events of more than 500 NTU FIGURE 4.3 Comparison of monthly mean water depth, dissolved oxygen, and turbidity for Blackbird Landing and Scotton Landing in 1996. (From the Delaware Department of Natural Resources and Environmental Control. 1999. Delaware National Estuarine Research Reserve: estuarine proÞles. Technical Report, Delaware Department of Natural Resources and Envi- ronmental Control, Dover, DE.) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 2 1.5 1 0.5 0 Water Depth (m) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 2 1.5 1 0.5 0 Water Depth (m) Water Depth Water Depth Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 12 10 8 6 4 2 0 Dissolved Oxygen (mg/l) Dissolved Oxygen Jan. Mar. May July Sept. Nov. 100 80 60 40 20 0 100 80 60 40 20 0 Dissolved Oxygen (%) Dissolved Oxygen Jan. Mar. May July Sept. Nov. 400 200 250 300 350 150 100 50 0 Turbidity (ntu) Turbidity Jan. Mar. May July Sept. Nov. 150 125 100 50 25 0 Turbidity (ntu) Turbidity Jan. Mar. May July Sept. Nov. Dissolved Oxygen (%) Dissolved Oxygen Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 12 10 8 6 4 2 0 Dissolved Oxygen (mg/l) Dissolved Oxygen Blackbird Landing Scotton Landing 1960_book.fm Page 127 Friday, August 15, 2003 1:37 PM Copyright © 2004 CRC Press, LLC [...]... Percent of total loading by source 43 .8/7.3 87 .4/ 20.1 82.1/18.7 70.3/13.2 10.1/0.2 100.0/2.2 52.6/33 .4 — 39.5/0 .4 66.7/ . 1 .4 Zn 52.6/33 .4 43.5/59.8 — 4. 0 /43 .6 39.6 PAH—95.1/10.6 — 4. 9 /4. 4 3.2 Chlorinated pesticides 39.5/0 .4 2.6/0.1 57.9/7.8 — 0.7 PCBs 66.7/<0.01 — — 33.3/0.1 <0.01 Volatile organics 79.0 /4. 5. Page 129 Friday, August 15, 2003 1:37 PM Copyright © 20 04 CRC Press, LLC 130 Estuarine Research, Monitoring, and Resource Protection TABLE 4. 4 Loading of Toxic Substances to the Delaware Estuary Contaminant Source. 1 24 Estuarine Research, Monitoring, and Resource Protection ( Baccharis halimifolia ). Red cedar ( Juniperus virginiana ) is also evident in the brackish tidal communities. Deep-water