Savannah National Wildlife Refuge Research Articles

Herpetofauna Occupancy and Community Composition along a Tidal Swamp Salinity Gradient

Occupancy patterns of herpetofauna in most tidal freshwater swamps are unknown. Tidal freshwater swamps currently face multiple threats, including salinization, which can influence their associated plant and animal communities. The impacts of salinization to herpetofauna communities in tidal freshwater swamps have not been assessed. To improve predictions regarding these herpetofauna, we conducted surveys in tidal freshwater swamps of the Savannah National Wildlife Refuge located in South Carolina, USA, from March to June, 2016 and 2017, using a variety of methods. Goals included inventorying species, determining communities, examining microhabitat associations, and modeling occupancy to predict the impacts of salinity changes. We detected 8 species of amphibians and 12 species of reptiles in our surveys. Community analyses failed to detect patterns related to measured environmental variables. Species richness and diversity declined along the salinity gradient, but the observed patterns did not match our predictions and may instead be related to site-level heterogeneity. Microhabitat associations were detected for two amphibian species via occupancy analyses. Occupancy and regression analyses indicated soil salinity may be a factor affecting nine species’ occurrences. Amphibian detections may be affected by water depth, pH values, and weather conditions. These results expand our understanding of herpetofauna within an understudied, and threatened, wetland type.

A Survey of the Amphibians of Savannah National Wildlife Refuge, South Carolina and Georgia

From 2004 to 2006, we used a variety of sampling techniques to survey the amphibians of Savannah National Wildlife Refuge (SNWR), a large protected area straddling the lower portions of the Savannah River on the border between South Carolina and Georgia. We documented 22 amphibian species—15 frogs and 7 salamanders—with a possible 23rd species present. Species richness was lower than what might be expected from amphibian field guides of species inhabiting the adjacent Coastal Plain, likely due to a lack of specialized habitats, such as temporary ponds and upland pine forest. Amphibians occupied a variety of habitats and appeared tolerant of the mildly acidic and low-oxygen conditions of many of the wetlands. Although additional species may be found at SNWR, this initial survey provides a historic baseline for monitoring amphibian populations as areas adjacent to the refuge are disturbed, the climate changes, and multi-use management objectives are implemented within refuge boundaries.

Decision Support System for Optimally Managing Water Resources to Meet Multiple Objectives in the Savannah River Basin

Managers of large river basins face conflicting demands for water resources such as wildlife habitat, water supply, wastewater assimilative capacity, flood control, hydroelectricity, and recreation. The Savannah River Basin, for example, has experienced three major droughts since 2000 that resulted in record low water levels in its reservoirs, impacting dependent economies for years. The Savannah River estuary contains two municipal water intakes and the ecologically sensitive freshwater tidal marshes of the Savannah National Wildlife Refuge. The Port of Savannah is the fourth busiest in the United States, and modifications to the harbor to expand ship traffic since the 1970s have caused saltwater to migrate upstream, reducing the freshwater marsh’s acreage more than 50 percent. A planned deepening of the harbor includes flow-alteration features to minimize further migration of salinity, whose effectiveness will only be known after all construction is completed. One of the challenges of large basin management is the optimization of water use through ongoing regional economic development, droughts, and climate change. This paper describes a model of the Savannah River Basin designed to continuously optimize regulated flow to meet prioritized objectives set by resource managers and stakeholders. The model was developed from historical data using machine learning, making it more accurate and adaptable to changing conditions than traditional models. The model is coupled to an optimization routine that computes the daily flow needed to most efficiently meet the water-resource management objectives. The model and optimization routine are packaged in a decision support system that makes it easy for managers and stakeholders to use. Simulation results show that flow can be regulated to substantially reduce salinity intrusions in the Savannah National Wildlife Refuge, while conserving more water in the reservoirs. A method for using the model to assess the effectiveness of the flow-alteration features after the deepening also is demonstrated.

Sediment quality in freshwater impoundments at Savannah National Wildlife Refuge.

Freshwater impoundments at Savannah National Wildlife Refuge (NWR), South Carolina, provide an important habitat for wildlife species, but degraded sediment quality in the Savannah River downstream of the discharge from two impoundments have caused concern about potential contaminant problems within the impoundments. The quality of sediments from five impoundments (impoundments no. 1, 2, 6, 7, and 17) on the NWR was evaluated using physical and chemical characterization, contaminant concentrations (metals, organochlorine pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons), and toxicity testing. Survival of Hyalella azteca (freshwater amphipod) exposed for 28 days to solid-phase sediments was not significantly different from controls, but growth was significantly decreased at several sites. Survival in 96-hour exposures to sediment pore water was significantly decreased at most sites. Factors contributing to the toxic responses were low pH (3.7 to 4.1), ammonia (20 mg/L), and increased concentrations of cations in the pore water. The excess of simultaneously extracted metals over the acid volatile sulfides in the sediments was also typical of sites displaying decreased sediment quality. Elemental concentrations in pore water were negatively correlated with pH, and the highest concentrations were observed in impoundment no. 7. The acidic nature of the sediment in this impoundment was exacerbated by recent draining, burning, and disking, which allowed oxidation of the previously anoxic wetland sediment. Sediment disturbance and mixing of vegetation into the sediments by disking may also have contributed to the formation of ammonia caused by microbial decomposition of the fragmented organic matter. Contaminants were not detected in sediments from the impoundments, but releases of acidic water with increased levels of sediment cations from the impoundments may have contributed to the degraded sediment conditions previously observed in the river. The practice of dewatering sediments for vegetation control may exacerbate the acidification of vulnerable sediments within impoundments of this NWR.

USE OF OAK HAMMOCKS BY NEOTROPICAL MIGRANT SONGBIRDS: THE ROLE OF AREA AND HABITAT

Abstract Many species of Neotropical migrant songbirds have declined in recent decades, due in part to loss and fragmentation of stopover habitat. To properly manage forested landscapes for migrating songbirds, information is needed on how size and habitat structure of forest patches influence their use by migrants during stopover. We conducted surveys of Neotropical migrant birds in eight oak hammocks of varying size (0.32–3.08 ha) at the Savannah National Wildlife Refuge, Jasper County, South Carolina during spring migration 1999 and 2000 and fall migration 1999. Hammock size was the most important factor related to number of total species, species per day, individuals per day, and density of migrants. Differences in vegetation structure and patchiness among hammocks did not explain differences in migrant abundance. Density of migrants tended to be higher in smaller hammocks, particularly during spring. Hammock use was generally similar between seasons and years. Two forest-interior breeding species occ...

Spatial Monitoring of Salinity and Stage in the Tidal Freshwater Marshes Of the Savannah National Wildlife Refuge

Spatial Monitoring of Salinity and Stage in the Tidal Freshwater Marshes Of the Savannah National Wildlife Refuge

Haemoproteus greineri in wood ducks from the Atlantic flyway.

Thin smears of blood were examined from 157 wood ducks (Aix sponsa) trapped at Savannah National Wildlife Refuge (South Carolina, USA) and Harris Neck National Wildlife Refuge (Georgia, USA) during spring and summer, 1994 and 1995. Thirteen wood ducks (8%) were infected with blood parasites. Eleven of these birds were infected with Haemoproteus nettionis, seven with Leucocytozoon simondi, and five with unidentified microfilariae. Additionally, eight wood ducks (5%) were infected with Haemoproteus greineri. This is the first record of H. greineri in anatids trapped along the Atlantic Flyway south of Labrador and the first record of this species in wood ducks. To further characterize the distribution of H. greineri in the wood duck, blood smears were examined from hatching year ducks trapped at 10 different Atlantic flyway locations during spring and summer, 1980 to 1983. Haemoproteus greineri was found in wood ducks trapped in all 10 locations which extend from 46 degrees N latitude in New Brunswick to 37 degrees N latitude in Virginia. These findings indicate that H. greineri is not exclusively boreal in distribution, but also is found, at least in wood ducks, along much of the Atlantic Flyway.

Species association changes across a gradient of freshwater, oligohaline, and mesohaline tidal marshes along the lower Savannah River

In the present study, plant species patterns and associated environmental factors of freshwater, oligohaline, and meschaline marshes of the Savannah National Wildlife Refuge were compared. DECORANA, an ordination method, was used to group vegetation classes. Discriminant function analysis was applied to resulting classes to quantify differences in salinity, elevation, and distance from tidal channels among classes. Nine vegetation classes across freshwater and brackish marshes corresponded significantly to salinity differences between sites. Combinations of elevation and distance from tidal channel were significant in separating vegetation classes within sites.Scirpus validus (Vahl) was the only species to occur over the entire range of measured physical parameters and accounted for much of the overlap between vegetation classes. The proportion of correctly classified vegetation classes between sites was 70%. Within each site, the proportion of correct classification was lower in the freshwater marsh (77% correct classifications) when compared with the oligohaline (82%), strongly oligohaline (83%), and mesohaline (85%) sites. Although overlap among classes was greater in the more diverse freshwater marsh, our results may reflect differences in the steepness of environmental gradients between sites and the scale at which physical parameters were measured rather than actual plant distribution overlap. Results suggest that resources are more finely divided among species in the freshwater marsh, resulting in a less distinct dominance hierarchy when compared with the mesohaline marsh.

Environmental contaminant concentrations in biota from the lower Savannah River, Georgia and South Carolina

Planned harbor expansion and industrial developments may adversely affect the economically important aquatic resources of the lower Savannah River, including those at the Savannah National Wildlife Refuge. To establish the present level of chemical contamination in this system, we collected a total of 102 samples of nine species of fish and fiddler crabs (Uca pugilator) from eleven sites in the lower Savannah River and on the Savannah National Wildlife Refuge, and analyzed them for concentrations of organochlorine chemicals, aliphatic and aromatic petroleum hydrocarbons, and 13 elemental contaminants: aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, and zinc. Residues of DDT (mainly as DDE), trans-nonachlor, dieldrin, Aroclor 1260, mirex, and petroleum hydrocarbons were common in fish from the lower Savannah River, but concentrations were below those warranting environmental concern. In general, the concentrations of elemental contaminants also were low; however, arsenic, cadmium, and chromium concentrations were elevated in fish from river stations near the city of Savannah, and lead was elevated in samples from the National Wildlife Refuge. Contamination of the lower Savannah River by organic and elemental contaminants, as indicated by concentrations in fishes and fiddler crabs, did not appear to pose a hazard.

SUCCESSFUL NATURAL RESOURCE DAMAGE CLAIM FOR A COASTAL OIL SPIL1

ABSTRACT In September 1987 a consent order was signed providing a damage settlement of $1.2 million to the U.S. government and the States of Georgia and South Carolina for an oil spill at Savannah, Georgia. This settlement, which included funds for injuries to fish and wildlife resources at Savannah National Wildlife Refuge and adjoining areas in the lower Savannah River, was reached through a cooperative natural resource damage assessment using the U.S. Department of the Interior's Natural Resource Damage Assessment Regulations. This paper describes this first and successful implementation of the damage assessment regulations and provides guidance for their future use in support of natural resource damage claims.

RESPONSE STRATEGIES IN A HIGH TIDAL RANGE ESTUARINE SYSTEM: THE SAVANNAH RIVER OIL SPILL

ABSTRACT In early December 1986, the tank vessel Amazon Venture discharged approximately 500,000 gallons of No. 6 fuel oil into the Savannah River. From the outset, the on-scene coordinator (OSC) placed the highest priority on protecting the Savannah National Wildlife Refuge and adjacent wetlands from environmental impacts. During 12 days of continuous effort, over 6,500 feet of sorbent and containment boom were deployed in the refuge. Nearly all of the containment and deflection barriers were ineffective due to tidal changes in flow direction and associated very high current, which were frequently over 6 meters per second. In spite of protection efforts concentrated in the refuge, less than 100 gallons of oil were recovered there. In other contaminated areas, cleanup focused on removal of oil from the water surface (recovering about 150,000 gallons) and on shoreline cleaning of rocks and seawalls in public places. No cleanup of wetlands was recommended. This paper is a discussion of the various response strategies evaluated and used in mitigating the effects of a major oil spill in this high tidal range estuarine system.

Sex- and Age-Ratio Bias of Cannon-Netted Geese

Age ratios of Canada geese (Branta canadensis), derived from catches in cannon traps, are of questionable value unless time on bait is taken into account. Findings were based on examination of 2,879 geese caught in 46 timed catches at Swan Lake National Wildlife Refuge in 1961 and 1962. The proportion of adults in the catches increased with length of time on bait. No significant differences were found in sex ratios as time on bait increased. This study was designed to determine whether any measurable sexor age-ratio biases are obtained in the cannon-net trapping of Canada geese. It has been speculated that the period of time geese spend on the bait at the trap sites, before the catch is made, may influence sex and age ratios obtained. Correct interpretation of band recoveries is important in analysis of population dynamics. One problem that plagues wildlife research is the difficulty of obtaining random samples from wild populations. If sex and age ratios from trap samples contain biases of unknown magnitude, we cannot accurately determine flock composition or predict productivity and turnover from these samples. Until we know the magnitude of bias involved, we cannot make corrections and must assume that present trap samples and band recoveries are indicative of the populations. This study was carried out at Swan Lake National Wildlife Refuge in north-central Missouri during October, November, and December of 1961 and 1962. Financial assistance was supplied by the Missouri Conservation Commission and an Edward K. Love Fellowship from the University of Missouri. Dr. W. H. Elder, Rucker Professor of Zoology at the University of Missouri, guided the study. I am also grateful to the following: Dr. Donald H. Hazelwood, Department of Zoology, University of Missouri, for advice on statistics; Richard Vaught, Waterfowl Biologist, and Fred Veach, Area Manager, Missouri Conservation Commission; Leo Kirsch, Manager, and Howard Thornsberry, Wildlife Technician, Swan Lake National Wildlife Refuge. Richard Thompson, from the Savannah National Wildlife Refuge, Georgia, and Earl Cunningham, of the Carolina Sand Hills National Wildlife Refuge, South Carolina, also assisted with observations and handling of geese for several days during the fall of 1962. MATERIALS AND METHODS Determination of time on bait before each catch necessitated observation of the bir s from the time they came near the trap site until the actual shot was fired for the catch. The two trap sites used during this study were located on opposite sides of Swan Lake. The points of concealment and detonation control were an old silo, now an observation tower, and a storage barn. The silo is about 400 yards from one site, the barn only 30 yards from the other. Nets and cannons were laid out parallel to the shoreline in conventional fashion 'Contribution from the Missouri Cooperative Wildlife Research Unit, U. S. Fish and Wildlife Service, Wildlife Management Institute, Missouri Conservation Commission, Edward K. Love Foundation, and the University of Missour , cooperating. 2 Present address: Bureau of Sport Fisheries and Wildlife, 403 Perlstein Bldg., Beaumont, Texas.