North Carolina Reservoirs Research Articles

Assessing vertical diffusion and cyanobacteria bloom potential in a shallow eutrophic reservoir

Han Y, Smithheart JW, Smyth RL, Aziz TN, Obenour CR. 2019. Assessing vertical diffusion and cyanobacteria bloom potential in a shallow eutrophic reservoir. Lake Reserv Manage. 36:169–185.Harmful blooms of cyanobacteria are an increasing threat to many lakes and reservoirs. While vertical mixing has been shown to be an important control on cyanobacteria dominance in some lakes, the relevance of mixing in relatively shallow turbid systems remains unclear. To explore mixing and its impact on cyanobacteria bloom potential, we leveraged data from a multiyear field campaign of a central North Carolina reservoir where artificial circulators were installed to (1) implement a parsimonious one-dimensional (1D) turbulent diffusion model with an artificial circulation term, (2) introduce a novel multi-objective calibration approach considering both water column temperature and stability, and (3) explore how mixing affects cyanobacteria bloom potential through changes in cyanobacteria light exposure relative to other algal taxa. Our multi-objective calibration approach is shown to realistically simulate both water temperature (R2 = 0.99) and water column stability (R2 = 0.62) throughout the year. Analysis of artificial mixing demonstrates the relative insignificance of the circulator deployment in our study area and suggests that at least eight times the implemented circulation rate would be required to substantially reduce the ability of buoyant cyanobacteria to outcompete other algal taxa for light. Overall, this study demonstrates an efficient and systematic approach for characterizing vertical mixing in lakes and reservoirs, which can be used to assess the viability of artificial circulation prior to deployment.

Beyond Selenium: Coal Combustion Residuals Lead to Multielement Enrichment in Receiving Lake Food Webs.

Effluents from coal-fired power plant ash ponds are a major source of environmental contamination, annually loading more than a million metric tons of pollutants to aquatic ecosystems in the United States alone. Though this waste stream is characterized by elevated concentrations of numerous inorganic constituents, decades of previous research effort have focused on the ecotoxicological consequences of a single stressor: selenium. In this study, we compared concentrations of 10 trace elements among three North Carolina reservoirs with varying burdens following decades of coal combustion residual (CCR) inputs. Along this pollution gradient, we examined (1) environmental compartment-specific trace element enrichment relative to reference lake levels and (2) differences in CCR accumulation patterns among abiotic and biotic compartments. We report significant multivariate differences between CCR-receiving and reference lakes for surface water, pore water, sediment, and fish tissues as well as differences in CCR accumulation among North Carolina resident fish species. Multiple-element enrichment across receiving lake compartments additionally highlighted that CCR pollution is a mixtures contamination issue. Our results inform the ongoing discussion about effective regulation of impaired water bodies and identify important questions that might guide the monitoring of these systems as they recover.

Correlation of consumer grade hydroacoustic signature to submersed plant biomass

Invasive macrophytes, such as non-native Hydrilla verticillata, negatively affect lentic systems of the Southeastern United States by impeding recreational activities and power generation as well as disrupting intrinsic ecological function. Expenditures associated with aquatic weed management include costs accompanied with monitoring, mapping, and implementing control measures. Traditional biomass sampling techniques have been widely utilized to assess the extent and abundance of submersed aquatic vegetation (SAV) incursions, but often require significant labor inputs which limits repeatability, the scale of sampling, and the rapidness of processing. Advances in consumer available hydroacoustic technology and data post-processing platforms offer the opportunity to estimate SAV biomass at scale with reduced labor and economic requirements. Research was conducted at two North Carolina reservoirs to compare acoustically derived cloud-based biovolume estimations from an over-the-counter echosounder, to in situ hydrilla biomass measurements. Temporal patterns, spatial developments, and hydrilla biomass prediction models are presented. Biomass and biovolume measurements were positively correlated at both the Shearon Harris and Roanoke Rapids study locations. The most robust predictive equation employed generalized additive models (GAMs) from the Shearon Harris dataset which, described environmental parameters with the lowest error and greatest agreement compared to other verified models. Each biovolume to biomass relationship supported the initial hypothesis that as biovolume increases, SAV biomass increases in a positive, non-linear trend. Implications from this study may prove useful for comparing seasonal growth patterns, littoral occupancy, and herbicide treatment effects on a spatiotemporal level.

Consistently High Trophic Overlap between Invasive White Perch and Native Black Crappies in Southeastern Reservoirs

AbstractThe detrimental impacts of invasive species often occur through deleterious trophic interactions (e.g., competition) with native species. However, the potential for competitive interactions between species may vary among systems, among seasons, or throughout the species’ ontogeny, requiring a thorough examination of trophic niches to determine whether overlap exists and to elucidate the likelihood of competition. The Black Crappie Pomoxis nigromaculatus is a popular game fish species across the United States, but recent invasions of White Perch Morone americana, which exploit a similar trophic niche, into southern reservoirs represent a major concern for the continued sustainability of Black Crappie fisheries. We examined the trophic niches of these species throughout their ontogeny in two North Carolina reservoirs during 2009 and 2010 using a combination of diet content and stable isotope analyses. Extensive and significant similarities in diet composition and isotopic niche overlap existed between Black Crappies and White Perch throughout their ontogeny and across seasons in both systems. Overlap was particularly high between smaller (<200‐mm), invertivorous Black Crappies and all sizes of White Perch. This overlap suggests that if invertebrate resources become limited, competition during the juvenile stage could reduce growth rates and survival of young Black Crappies. By evaluating variation in the trophic niches of each species among seasons, body sizes, and reservoirs, we conclude that the potential for competitive interactions between White Perch and Black Crappie is high in southern reservoirs. Management options to either reduce White Perch abundance or prevent their spread to novel habitats may be necessary to sustain native and supplemented Black Crappie populations that are potentially vulnerable to White Perch invasions.

Assessing the Influence of Tilapia on Sport Fish Species in North Carolina Reservoirs

AbstractRedbelly Tilapia Tilapia zilli and Blue Tilapia Oreochromus aureus are indigenous to Africa and the Middle East, but now occur throughout the southeastern United States. It is fairly well understood that foraging flexibility and wide salinity, oxygen, and temperature tolerances have led to general invasion success for most tilapia species. Conflicting empirical information about the influence of tilapia on native sport fish species, however, leaves natural resource managers unable to anticipate and prevent further introductions and potential associated risks to native sport fishes. This investigation focused on two North Carolina reservoirs with tilapia populations: Hyco Lake, a large reservoir in northcentral North Carolina and Lake Julian, a small impoundment in western North Carolina. These reservoirs receive heated effluent from power generation, which is assumed to provide winter refuge for tilapia at a time when temperatures would otherwise lead to mortality. We assessed relative abundances of the tilapias and native sport species (Bluegill Lepomis macrochirus, black basses Micropterus spp., and Black Crappie Pomoxis nigromaculatus) in these systems and examined their trophic interactions via diet and stable isotope analyses in both lakes. In Hyco Lake we assessed potential spatial interactions and influences on relative abundance using a priori candidate models and model selection via Akaike's information criterion (AIC). These analyses indicated little evidence of tilapias influencing the relative abundances of the sport species in Hyco Lake. In both lakes, however, we did find substantial diet overlap between the tilapias and Bluegill along with isotopic niche overlap between Blue Tilapia and Bluegill in Lake Julian and Redbelly Tilapia and Bluegill in Hyco Lake. Due to the omnivorous and flexible diet of all three species these interactions were not surprising, but the ultimate influence on Bluegill growth and size structure is unknown. Overall, our results suggest that tilapia are exploiting trophic niches that are not used by the sport fishes of interest in these two very different reservoir systems and that their direct impact on sport species is not substantial.

A reservoir siting tool for North Carolina: System design & operations for screening and evaluation

The North Carolina Reservoir Siting Tool (“NC-RES”) is a web-based, comprehensive, geographic information system designed to assist non-specialist and non-scientific users in carrying out first-pass, basic screening assessments of sites for potential municipal, county, or state reservoir locations. The tool operates based on terrain data, and is designed to take advantage of web mapping technology and the availability of North Carolina's LiDAR-derived, high-resolution digital terrain data. The tool presents users with an easy-to-use, “point and click” mapping interface and provides a variety of data and analyses about proposed reservoir sites, including quantitative information about reservoir inundation areas, drainage basins, and the effects of a proposed reservoir on the inundation and drainage areas. This paper provides a basic description of the processing framework and underlying data of the NC-RES tool as an automated approach to potential reservoir site evaluation and screening.

White Perch in Small North Carolina Reservoirs: What Explains Variation in Population Structure?

AbstractWhite Perch Morone americana have been introduced into many inland systems throughout the United States. To determine factors affecting White Perch abundance and size structure, we compared White Perch growth, timing of maturity, and trophic level; the abundance of a predator (Largemouth Bass Micropterus salmoides); the abundance of an ecologically significant mid‐level omnivore (Gizzard Shad Dorosoma cepedianum); prey availability (chironomid and zooplankton abundances); and environmental variables (specific conductivity, Secchi depth, dissolved oxygen concentration, and temperature) among four reservoirs (two with high White Perch abundance and two with low abundance). White Perch size structure was closely tied to abundance, with truncated size structure as abundance increased. Among the other variables we tested, only Largemouth Bass abundance had a significant (negative) relationship with White Perch abundance. White Perch size structure appeared to be highly density dependent, and variables that commonly explain variation in abundance of introduced fishes did not explain differences in the four White Perch populations we studied. Further study of the competitive and predatory interactions of White Perch and Largemouth Bass over ontogeny could shed light on the mechanism(s) potentially shaping population structure of the two species where they coexist.

Trophic Niche of Invasive White Perch and Potential Interactions with Representative Reservoir Species

AbstractThe trophic dynamics of invasive species can yield insights into the mechanisms of invasion success and aid in the prediction of potential impacts on established species. Additionally, the predicted effects of an invader may differ depending on how it integrates into the resident food web and whether its resource use changes throughout the invasion process. We investigated the trophic dynamics of populations of invasive White Perch Morone americana in three large North Carolina reservoirs and evaluated the potential for impacts on members of the resident fish community. Specifically, we used stable isotope and diet analyses to evaluate their trophic niche relative to three representative species in each reservoir chosen for their widespread range, potential overlaps with White Perch, recreational value, and representation of ecological guilds based on habitat and prey sources. The species were a native littoral generalist invertivore (Bluegill Lepomis macrochirus), native littoral piscivore (Largemouth Bass Micropterus salmoides), and stocked pelagic piscivore (Striped Bass Morone saxatilis or Walleye Sander vitreus, depending on their availability). Small (<70 mm TL), medium (120–170 mm TL), and large (>200 mm TL) White Perch occupied different trophic positions, and these positions were generally consistent among reservoirs relative to the representative species. Small and medium White Perch had the largest niche areas and high diet overlap with Bluegill in two of three lakes, whereas large White Perch had moderate diet overlap with Striped Bass, Largemouth Bass, and Walleye. As a species, White Perch occupy a wide trophic niche, which may aid in successfully establishing invasive populations. However, White Perch use resources shared by other members of the fish community, which could lead to negative impacts on these species.

Vertical Profiling Safeguards Drinking Water and Sheds Light on Cyanobacteria

This report discusses a search for algal toxins in North Carolina reservoirs that evolved into an ongoing early warning system for three important drinking water reservoirs that serve two large cities. The search also yielded a greater understanding of the dynamics of blue‐green algae, or cyanobacteria, in the state's reservoir system. Building on a pair of grants from the Centers for Disease Control and Prevention (CDC) to explore key reservoirs for cyanotoxins, the Center for Applied Aquatic Ecology (CAAE), directed by JoAnn Burkholder at North Carolina State University in Raleigh, teamed up with the North Carolina cities of Raleigh and High Point to track cyanobacteria blooms throughout the water column. On the basis of continuous in situ water quality monitoring of the water column near the intake structures in three reservoirs, treatment plant operators can vary the depth at which they draw water into their plants, avoiding cyanobacteria blooms that can introduce toxins or affect taste and odor. The in situ data as well as manually collected measurements and grab samples also provide insight about the effect of weather and land use on cyanobacteria.

Hatching Date Influence on Age-Specific Diet and Growth of Age-0 Largemouth Bass

Largemouth bass can hatch over a 70-d period, and among fish less than 90 d old, those hatched earlier can grow faster than those hatched later. Because faster growth of age-0 largemouth bass has been positively linked with fish consumption, it has been suggested that faster growth of largemouth bass hatched earlier was also due to higher fish consumption. We determined hatching-date-specific diets and growth of largemouth bass up to about 180 d old, collected in summer and fall 1987 in a North Carolina reservoir. Frequency of fish consumption for age-0 largemouth bass of all sizes tended to decrease as the growing season progressed. Largemouth bass that hatched earlier, however, were piscivorous at a younger age and maintained a higher level of piscivory late in the growing season than did fish that hatched later. Dietary differences that were hatching-date-dependent seemed to be due to seasonal decrease in prey fish availability. The growth advantage for fish hatched earlier was primarily expressed for fish less than about 85 d old. No growth differences related to hatching date were observed among fish older than 85 d. Studies are needed to determine whether the faster growth of fish hatched earlier results in lower mortality and ultimately in greater recruitment.

A Bioenergetics Analysis of Diel Vertical Migration by Kokanee Salmon, Oncorhynchus nerka

Diel vertical migration of fishes is probably a result of the combined effects of several selective forces, including predator avoidance, foraging efficiency, and bioenergetic efficiency. We considered both foraging efficiency and energetic efficiency as a combined effect which we called growth maximization. The importance of growth maximization as a selective force was evaluated with a bioenergetics-based model to estimate growth rates of various migration scenarios of kokanee salmon, Oncorhynchus nerka. Environmental parameters (temperature and zooplankton distributions) in the model were obtained from a North Carolina reservoir with an established population of kokanee. The simulations demonstrated that vertical migrations can be energetically advantageous when kokanee and their prey are thermally segregated and that ontogenetic and seasonal differences in the optimal migration strategy should be expected. The general rule for vertical migration as determined from the simulations is to feed where net energy intake is maximized and then reside when not feeding where energetic costs are minimized and food is digested to the point that consumption during the next feeding period is not limited by the amount of undigested food remaining in the stomach. Data obtained from vertical gill nets and hydroacoustics were compared with model predictions.

Effects of Nutrients and Non-algal Turbidity on Blue-green Algal Biomass in Four North Carolina Reservoirs

ABSTRACT An analysis of data from four turbid North Carolina reservoirs showed that both the summer mean biomass and relative biomass of planktonic blue-green algae (Cyanophyta/Cyanobacteria) are frequently lower than would be predicted by models developed from natural north temperate lakes. These results are consistent with the hypothesis that the growth of blue-green algae in these reservoirs is reduced in the presence of high concentrations of non-algal turbidity.

The Suprapopulation Dynamics of Bothriocephalus acheilognathi in a North Carolina Reservoir: Abundance, Dispersion, and Prevalence

A 2 1/2-year study (September 1980-March 1983) of abundance, dispersion, and prevalence of the pseudophyllidean cestode, Bothriocephalus acheilognathi, in 3 species of fish (Gambusia affinis, Notropis lutrensis, and Pimephales promelas) was conducted in 3 ecologically distinct areas of a North Carolina cooling pond. Mean infrapopulation density and prevalence differed by site, season, and species and size of hosts. Degree of aggregation and abundance and prevalence of gravid worms differed by species of host. Abundance of gravid worms was significantly lower in metapopulations from localities that received power plant effluents. The differences in infrapopulation density, prevalence, and aggregation appeared to be related to predator-prey interactions, which varied with season and local community structure. Differences in abundance of gravid worms, on the other hand, were probably caused by differential suitability of hosts and by local variation in selenium concentration in the water column. Thus, it appears that both biotic and abiotic components of the host community determined the suprapopulation dynamics of B. acheilognathi in Belews Lake.

THE FEEDING ECOLOGY OF THE BLUE TILAPIA (T. AUREA) IN A NORTH CAROLINA RESERVOIR

ABSTRACT The blue tilapia (T. aurea) has been introduced at times in the southeast as a biological control agent for nuisance vegetation. The winter and summer food habits of this fish were studied in a heated North Carolina reservoir during 1984. Stomachs from fish captured in February contained mainly organic and inorganic detritus and large amounts of phytoplankton, which was blooming at the time. In August, when plankton was scarce, nearly the entire volume of the stomachs consisted of detritus gleaned from the sediments. The ratio of inorganic to organic material increased along with fish size. Zooplankton and benthic invertebrates comprised only small percentages of the tilapia stomach contents in this reservoir. The data indicate that the blue tilapia is an opportunistic feeder that will successfully utilize whatever food source is available.

The production of five genera of Chironomidae (Diptera) in Lake Norman, a North Carolina reservoir

The production of five genera of chironomids collected at 4- and 8-m depths at four stations in Lake Norman, North Carolina, was estimated using the size-frequency method. To correct for multivoltinism, the estimates were adjusted by multiplying by 365/Cohort Production Interval. Ranges of production estimates (P) in milligrams dry mass m-2 yr-1 and production/mean annual biomass ratios (P/B ratios) for each genus over both depths were: Tanytarsus, P = 744 to 8788, P/BB = 66 to 176; Cladotanytarsus, P = 74 to 2387, P/B = 69 to 100; Stempellina, P = 19 to 412, P/ B = 74 to 132; Chironomus, P = 166 to 7293, P/ B = 50 to 70; Cryptochironomus, P = 92 to 398, P/ B = 71 to 221. These estimates are among the highest reported for chironomids, due primarily to the rapid larval development times estimated for these genera.

A model for the density ofAeromonas hydrophila in Albemarle Sound, North Carolina

The abundance ofAeromonas hydrophila was measured monthly at 29 sites in Albemarle Sound, North Carolina and its tributaries from April 1977 through July 1979. Simultaneous measurements included heterotrophic plate count bacteria, fecal coliform bacteria, and 18 physical and chemical parameters. Using only 6 water quality parameters, multiple correlation and regression analysis of the data produced a best-fit regression which explained 38% of the variation observed inA. hydrophila density. The 6 water quality parameters included dissolved oxygen, temperature, orthophosphate, chlorophyll A trichromatic, total Kjeldahl nitrogen, and ammonia. Heterotrophic plate count bacteria and fecal coliform densities were highly correlated withA. hydrophila density, but made the model very unstable. The model was successfully tested against similar data collected for 2 other North Carolina reservoirs, Lake Norman and Badin Lake. Data from 10 sites in Badin Lake over 18 months and from 7 sites on Lake Norman over 5 months were not significantly different from the Albemarle Sound model. Conditions of water quality that may give rise to "blooms" ofA. hydrophila will simultaneously contribute to the probability of increased epizootics in fish in the southeastern United States.

Epistylis and Aeromonas Hydrophila Infections in Fishes from North Carolina Reservoirs

brought to the attention of the Division of Inland Fisheries of the North Carolina Wildlife Resources Commission by fishermen in the fall of 1972. The fishermen were concerned about the presence of red lesions on game species which made the fish unappealing and undesirable as table fare. The health of fish in these river chains has since become a source of widespread interest and concern in North Carolina.

Limnology of a North Carolina Reservoir and Its Use in Water Treatment

By the use of limnologic sampling techniques and a program of systematic surveys, variations in water quality in University Lake, Chapel Hill, North Carolina were studied and defined. Sharp changes in water quality associated with specific seasonal phenomena were anticipated and intake levels or treatment procedures adjusted accordingly. The data in this article was collected in 1960. All analytic techniques followed those outlined in the tenth edition of Standard Methods except as otherwise noted. Temperature measurements were made with direct‐reading thermistor telethermometers.