Kentucky Lake Research Articles

Assessment of toxicity potential of freely dissolved PAHs using passive sampler in Kentucky Lake and Ohio River

Polycyclic aromatic hydrocarbons (PAHs) are characterized with high KOW values, which lead to their recalcitrant nature, bioaccumulation, and biotoxicity, adversely affects the environment. Passive samplers (PS) have proven effective in measuring bioavailable PAH concentrations for toxicity assessments. In this study, we used low-density polyethylene (LDPE) to measure freely dissolved PAH concentrations (Cfree) in Kentucky Lake (KL) and Ohio River (OH), USA. PAHs toxicity potential in sediment was assessed using equilibrium partitioning sediment benchmarks toxic units (ESBTUs) and the interstitial water toxic units (IWTUs) that were derived from OC-normalized concentration (COC) and Cfree, respectively. The Cfree in April and June were 127 and 97 times higher in OH than in KL, respectively. Moreover, ESBTUs were higher in both the KL and OH compared to the IWTUs, suggesting that ESBTUs overestimate the toxicity potential to organisms. These results indicate that PS provides a reliable method for assessing the toxicity potential in sediments.

Geochemical and mineralogical proxies beyond temperature: Autumn seasons trapped in freshwater nacre

Measurements of trace element chemistry, mineralogy, and isotope geochemistry are rarely combined with known environmental data to provide a more complete story about how environmental conditions are recorded in biomineral carbonates. Here, cultured (farmed) pearls serve as relatively pristine time capsules to study these geochemical and mineral-based proxies. Cathodoluminescence (CL) imaging and Raman spectroscopic mapping on the µm-scale reveals that heterogeneous crystal bonding environments, geochemistry, and organic contents across the growth history of a freshwater pearl reflect environmental shifts in Kentucky Lake, TN, USA. A major CL peak at 551 nm aligns with increased manganese and organic contents and correlates with lake conductivity and alkalinity data. These CL features are temporally offset from previous 10-µm-scale aragonite nacre oxygen isotope measurements (δ18OArg) that record periods of minimum lake temperatures in winter seasons. Thus, we suggest that these trace element and organic features represent autumn or spring rainy seasons that experience lake turnover events and more land runoff rich in Mn and nutrients, increasing aragonite-bound Mn and organic contents in the nacre. This 551 nm signal is absent in Mn-poor saltwater pearl nacre. A second CL peak at 444 nm shows different heterogeneous features likely due to crystal structure shifts, as evidenced by correlations to a Raman map of translational (T): librational (L) mode height ratios typically signaling changes in nacre tablet orientation. Thus, we show that µm-scale CL and Raman mapping may serve as complementary environmental proxies to novel SIMS-based δ18OArg temperature proxies in order to capture additional information about local lake environments at seasonal to sub-seasonal temporal resolutions.

Determination and comparison of freely dissolved PAHs using different types of passive samplers in freshwater

Polycyclic aromatic hydrocarbons (PAHs) are well-known for their recalcitrant properties and biotoxicity in organisms, leading to serious environmental and health problems. Despite various analytical methods available, accurate determination of the bioavailable fraction is warranted in order to evaluate the precise toxic potentials of these compounds. Currently, the passive sampler is used worldwide to measure the bioavailable PAHs in the environment using the equilibrium partitioning principle. In this study, we co-deployed different types of passive samplers, which are linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), to determine freely dissolved concentrations (Cfree) of PAHs using the performance reference compounds (PRCs) in Kentucky Lake (KL), Ohio River (OH), and Mississippi River (MS). The fractional equilibrium (feq) of BeP-d12 was observed to be high in LLDPE compared with LDPE in OH and MS. In contrast, the feq of all PRCs was similar in both passive samplers in KL due to slow flow velocity. The sum of average freely dissolved PAH concentrations in LLDPE and LDPE during the exposure period were 2.89 and 1.27 ng/L in KL, 8.13 and 3.31 ng/L in OH, and 5.19 and 3.82 ng/L in MS, respectively. The results revealed that LLDPE is a suitable alternative tool to LDPE for both short-term and long-term monitoring of PAHs.

Long-term changes in unionid community in Kentucky Lake: Implications for understanding the effects of impoundment on river systems

Freshwater mussels are both critically important in their ecosystems and rapidly declining around the world. Damming is a key reason for this decline in many locations because it affects the flow and turbidity of river systems, leading to numerous detrimental effects on benthic communities. Although the ecological effects of impoundment have been well studied on timescales ranging from years to decades, the ecological effects of impoundment on longer (50–100 years) timescales are less well understood, with a key question being: how long after the building of dams and impoundments do we expect community structure to continue changing? In this study, we explore historical changes in the freshwater mussel assemblages in Kentucky Lake (dammed in 1944) using decades-long collections housed at Murray State University in combination with other historical records. After digitizing these collections and applying a robust rarefaction protocol to account for uneven sampling, we quantify changes in unionid assemblage structure alongside coeval water quality data collected through the Kentucky Lake Long-Term Monitoring Program. We find that subsampled richness exhibited declines after dam construction with losses among opportunistic taxa, channelization-tolerant taxa, and impoundment-intolerant taxa. We also find increases in the proportions of equilibrium taxa throughout the dataset. Overall, the assemblage composition reached an equilibrium by the year 2000 (50 years after impoundment). In concert, river water quality data show a decline in turbidity and increase in light penetration in the period 1988–2020. Although the geohistorical records treated in this study are patchy in time, we argue that they are nonetheless valuable and illustrate that freshwater ecosystems may serve as potential sites of restoration decades after anthropogenic disturbance. In turn, this emphasizes the importance of geohistorical collections to studying long-term changes in community structure and developing strategies for conservation and environmental remediation.

Isotopic niches of Silver Carp and two native planktivores in a large reservoir

Human-mediated biological invasions can greatly reduce native species diversity. More than 138 nonnative fishes have been introduced to the United States. Many of these nonnative species can alter ecosystem dynamics and compete with native species. The planktivorous Silver Carp (Hypophthalmichthys molitrix Valenciennes in Cuvier and Valenciennes, 1844) is a nonnative species of concern that is currently expanding its range across the Greater Mississippi River Basin in the Midwestern United States. The objective of our study was to determine the degree of potential competition among invasive Silver Carp and the native planktivores, Gizzard Shad (Dorosoma cepedianum Lesueur, 1818) and Threadfin Shad (Dorosoma petenense Günther, 1867), in Kentucky Lake, a large reservoir located in western Kentucky and Tennessee. We used data derived from N and C isotopes to model isotopic niches, calculate quantitative metrics to describe variability within and among isotopic niches and trophic positions, and qualitatively assess seasonal shifts in trophic positions. Our results suggest that in the spring, older (≥1 y old) Silver Carp share resources with older and young-of-year (YOY; <1 y old) Gizzard Shad, whereas YOY Silver Carp only share resources with YOY Gizzard Shad. Additionally, our analyses showed that older Silver Carp and older Gizzard Shad share resources in the summer. In contrast, we found no overlap in resource use between YOY Threadfin Shad and YOY or older Silver Carp. Furthermore, we provide evidence of intraspecific ontogenetic shifts in isotopic niche area and overlap between invasive and native fishes (measured by sample-size corrected standard ellipse area). If resources become limiting, invasive Silver Carp may compete with multiple life stages of Gizzard Shad in Kentucky Lake and alter foodweb dynamics.

Phytoplankton Survival in Hindgut of Invasive Silver Carp (Hypophthalmichthys molitrix)

The ability of organisms to survive ingestion and digestion by their predators, or endozoochory, is a fascinating ecological phenomenon that can facilitate predator-mediated dispersal of prey and alter interaction strengths within ecological networks. However, the role of endozoochory in the context of invasive species is considered less often. Throughout the United States, Silver Carp (Hypophthalmichthys molitrix) are prolific invaders that often alter food web structure of recipient ecosystems through the consumption of basal resources. Despite the biogeochemical and food web effects of Silver Carp, there is limited understanding of plankton prey survival after Silver Carp consumption and digestion, and even less known about the ecological effects of selective diets and potential survival. In this study, we quantify hindgut contents of Silver Carp collected from Kentucky Lake, Kentucky, Tennessee River Valley, United States. We found the majority (83%) of phytoplankters within hindguts of Silver Carp showed little digestion prior to egestion. Our study suggests digestion limitations of Silver Carp may have important ecological implications for invaded environments. These results may be applicable in understanding how this rapidly spreading invasive fish can influence food web dynamics and biogeochemical cycles pertinent to toxic algal blooms within recently invaded ecosystems, and forecasting invasion in the near future.

Coupling Mineralogy and Oxygen Isotopes to Seasonal Environmental Shifts Recorded in Modern Freshwater Pearl Nacre From Kentucky Lake

AbstractBiominerals that accrete shell or skeleton are commonly used as windows to past geochemical environments. Using biominerals as paleoproxies depends on the assumption that biominerals faithfully and predictably record environmental parameters, yet little has been done from a mineralogical perspective to understand how various environmental shifts impact shell and skeleton mineralogy and how mineralogy influences proxy calibrations. In this study, we correlate a suite of environmental data from the Kentucky Lake Long‐Term Monitoring Program with mineralogical and chemical signatures of modern cultured pearl nacre. Six transects were measured across three pearls from nucleus to edge for oxygen isotope ratio (δ18O) using SIMS (10‐μm spots) and for mineralogy via nacre tablet thickness using SEM and via carbonate bonding environments using Raman spectroscopy. After confirming a strong seasonal correlation between δ18O and temperature, we extend δ18O correlations to relative nacre OH/O ratios, lake dissolved oxygen, and lake light levels at 1 m depth. Although nacre tablet thicknesses are not clearly correlated with temperature, we observe correlative trends with lake conductivity and relative nacre OH/O ratios. For the Raman spectroscopy measurements, there was a modest inverse correlation between increasing carbonate ν1 and ν4 vibrational mode peak heights with δ18O and lake dissolved oxygen levels. Standard deviations in Raman T:L peak area ratios, as an estimation of angle spread of tablet crystallographic orientation, correlate with lake reduction potential. This approach of combining geochemical, isotopic, mineralogical, and environmental data lends a more holistic view to biomineralization in natural systems and to the decoding of environmental mineral signatures.

Patterns of Antemortem Tooth Loss in Late Prehistoric West-central Tennessee

The later prehistoric subsistence-settlement pattern in the Kentucky Lake Reservoir (KLR) of northern west-central Tennessee is of interest as human occupation inexplicably terminates by AD 1450 as part of a larger regional depopulation. Antemortem tooth loss (ATL) collectively and by tooth type was identified in four site samples from the KLR. These are a Late Woodland (AD 600-900) sample (Hobbs) and three Middle Mississippian period (AD 1100- 1400) hierarchically organized and presumptively maize agriculturalist samples (Link/Slayden, Gray Farm , Thompson Village). ATL prevalence in the Hobbs sample is consistent with a native crop and seasonal foraging economy. The ATL in the Link sample is more congruent with the pre-maize Late Woodland sample than the essentially contemporaneous Gray Farm site sample. Thompson Village, a later-dated satellite community of the Gray Farm polity, exhibits significantly fewer ATL than the Gray Farm sample. This may flag climate-influenced agricultural shortfall of dietary carbohydrates later in the occupation sequence. Additionally, males in the Gray Farm site sample have significantly more ATL than males in the other two Mississippian samples. The patterns suggest regional, possibly shortfall mitigated, differences in maize intensification with a polity-specific male-focused maize consumption in the Gray Site.

Diel Influences on Silver Carp Catch Rates Using an Electrified Paupier in Lentic Habitats

AbstractThe CPUE (fish/6,000 m3) of Silver Carp Hypophthalmichthys molitrix obtained by using an electrified butterfly trawl (paupier) was evaluated among various temporal (time of day and season) and spatial (location, habitat [shoreline and open water], and water depth) factors that are likely to be influential in large lentic habitats. The paupier sampled the upper water column (1.5 m) in three locations (Kentucky Lake, Kentucky [two embayments]; Lake Barkley, Kentucky [forebay]; and upper Illinois River, Illinois [two backwaters]). Sampling commenced 2 h prior to sunset and continued into the night, not exceeding 5 h beyond sunset. Model selection showed that all temporal and spatial factors were important. Post hoc analysis revealed that Silver Carp CPUE was higher at night (beyond 1 h after sunset), in shoreline habitat, and in water generally no deeper than 5 m. Seasonal variation in CPUE occurred, but in general the CPUE was high in the fall for all locations. Considering these results for management application, we estimated the sampling effort required to reach precise CPUE and adequately assess size structure (125 stock‐length fish) in shoreline habitat at night. These sampling objectives were attainable in the spring and fall seasons for all locations (4–31 deployments) but were more variable in summer. We recommend consideration of the paupier as a standard method to sample Silver Carp in large lentic habitats by using the guidelines provided herein (i.e., sampling of the shoreline beyond 1 h after sunset during the fall season). An important next step to strengthen this method is to validate CPUE as an index of density.

Tennessee River Resource Stewardship and Protection: The Tennessee River Line Trail Project and Partnerships

The Tennessee River had a long and colorful history of transporting Native Americans, settlers, armies, and cargo of all types in 1700s and 1800s. The headwaters of the Tennessee River, the largest tributary of the Ohio River, originates in the Appalachian Mountains of eastern United States. Created by the confluence of the Holston and French Broad rivers at Knoxville, the Tennessee River flows approximately 1049 km to Paducah, Kentucky where it drains into the Ohio River. This paper highlights how the landscape and geological resources of the Tennessee River and tributaries watershed contributed to the successful economic development of this historical region of North America. The Tennessee River is one of the most biologically diverse freshwater systems in the United States. Environmental challenges included an unsuccessful attempt to keep invasive species, such as the Asian carp, out of the Tennessee River and the Kentucky Lake. The 1049 river kilometer Tennessee River regional trail system with charter River Towns was designed to promote recreational tourism, increase the use of the Tennessee River and to create generations of people who care about the river and are willing to provide environmental stewardship of the watershed resources and protect the river.

Caries as an archaeological problem-solving tool: reconstructing subsistence patterns in late prehistoric west-central Tennessee

The dentition from two Middle Mississippian period (~AD 1100-1350) site samples (Gray Farm [~AD 1150-1400], Link/Slayden [~AD 1200-1400]) from the Kentucky Lake Reservoir of west-central Tennessee area are examined for the presence of caries to assess whether a maize-intensive subsistence economy is evident or the retention of the cultivation of domesticated native seeds (i.e., the Eastern Agricultural Complex). Given the absence of archaeological context, the caries prevalence operates as an archaeological problem-solving tool. The caries prevalence by tooth type are compared to a Late Woodland period (~AD 400-900) site sample (Hobbs) from the Kentucky Lake Reservoir as well as three unequivocal maize-intensive site samples from the Late Mississippian period (~AD 1300-1550) of East Tennessee. The Gray Farm site aligns statistically with the maize-intensive samples; Link/Slayden does not and resembles the caries prevalence of the Hobbs sample. The Mississippianization process in the Kentucky Lake Reservoir clearly varies in the adoption of maize as a primary cultigen. This may reflect the difference in geo-political location of Gray Farm and Link/Slayden relative to neighboring Mississippian economies, particularly to the east (Middle Cumberland Culture), or it may reflect potential temporal differences among the Middle Mississippian period settlements within the Kentucky Lake Reservoir.

Diet of Invasive Silver Carp (Hypophthalmichthys molitrix) in a Mainstem Reservoir Ecosystem

Hypophthalmichthys molitrix (Silver Carp) is an invasive fish that threatens ecosystem function by consuming basal food web resources. In this study we quantify gut contents of 83 Silver Carp in the mainstem reservoir ecosystem of Kentucky Lake, Kentucky, Tennessee River Valley, United States. Silver Carp guts contained phytoplankton (63.5%), zooplankton (33.8%) and heterotrophic flagellates (2.7%) based on volume. Additionally, we compare existing literature on Silver Carp diet and trophic position (i.e., stable isotope information). Our study indicates that Silver Carp are planktivorous and consume organisms within multiple lower trophic levels across a range of habitats. However, we show that Silver Carp diets differ at finer taxonomic scales and suggest these differences may be driven by forage availability. To our knowledge, this is the first study to quantify diets of Silver Carp within a mainstem reservoir ecosystem designed for flood storage with a comparison to existing Silver Carp diet literature. The results of this study may be useful in predicting ecological implications of Silver Carp invasion across a diversity of habitats.

Comparison of trace elements in freshwater pearls cultured in Japan, China, and USA

In this paper, we performed PIXE analysis of trace elements in freshwater pearls cultured in four different areas: Lake Biwa (Japan), Lake Kasumigaura (Japan), an unidentified lake in China, and Kentucky Lake (USA). We investigated the difference of trace elements contained in the four pearls from different aquaculture environments. The observed trace elements are Mn, Fe, Cu, Zn, and Sr. The major trace elements are Mn, Sr for all the samples. From comparison of the proportions of elements contained, we found the following features: (1) The Kasumigaura pearl has a nucleus with a high Mn/Sr ratio, (2) The Biwako pearl is low in iron content, and (3) The American pearl has high in Fe/Sr, Cu/Sr, and Zn/Sr ratios.

The dependence of synchrony on timescale and geography in freshwater plankton

AbstractSpatial synchrony is defined by related fluctuations through time in population abundances measured at different locations. The degree of relatedness typically declines with increasing distance between sampling locations. Standard approaches for assessing synchrony assume isotropy in space and uniformity across timescales of analysis, but it is now known that spatial variability and timescale structure in population dynamics are common features. We tested for spatial and timescale structure in the patterns of synchrony of freshwater plankton in Kentucky Lake, U.S.A. We also evaluated whether different mechanisms may drive synchrony and its spatial structure on different timescales. Using wavelet techniques and matrix regression, we analyzed phytoplankton biomass and abundances of seven zooplankton taxa at 16 locations sampled from 1990 to 2015. We found that zooplankton abundances and phytoplankton biomass exhibited synchrony at multiple timescales. Timescale structure in the potential mechanisms of synchrony was revealed primarily through networks of relationships among zooplankton taxa, which differed by timescale. We found substantial interspecific variability in geographic structures of synchrony and their causes: all mechanisms we considered strongly explained geographic structure in synchrony for at least one species, while Euclidean distance between sampling locations was generally less well supported than more mechanistic explanations. Geographic structure in synchrony and its underlying mechanisms also depended on timescale for a minority of the taxa tested. Overall, our results show substantial and complex but interpretable variation in structures of synchrony across three variables: space, timescale, and taxon. It seems likely these aspects of synchrony are important general features of freshwater systems.

Using geography to infer the importance of dispersal for the synchrony of freshwater plankton

Spatial synchrony in population dynamics is a ubiquitous ecological phenomenon that can result from predator–prey interactions, synchronized environmental variation (Moran effects), or dispersal. Of these, dispersal historically has been the least well studied in natural systems, partly because of the difficulty in quantifying dispersal in situ. We hypothesized that dispersal routes of plankton were based on the major and consistent water current movements in Kentucky Lake, a large reservoir in western Kentucky, USA. Then, using 26‐year time series collected at 16 locations, we used matrix regression techniques to test whether spatial heterogeneity in strengths of hypothesized dispersal predicted spatial patterns of synchrony of phytoplankton and zooplankton, thereby testing for evidence of dispersal as a possible mechanism of synchrony in this system. Nearly all taxa showed significant spatial synchrony that did not decline with increasing linear distance between locations. All taxa also showed substantial geographic structure in synchrony that was not explained by linear distance. Matrix regression revealed that our hypothesized matrix of dispersal pathways, which differed substantially from linear distance, was a significant predictor of spatial variability in synchrony in phytoplankton biomass, and Bosmina longirostris and Daphnia lumholtzi densities. Thus dispersal was a likely mechanism of synchrony for these taxa. Our hypothesized dispersal matrix was a significant predictor of spatial patterns of synchrony for these taxa even after accounting for numerous alternative possible mechanisms, including possible Moran effects through any of ten physical/abiotic constraints. Our findings indicate that statistically comparing hypothesized or measured dispersal pathway information to synchrony data via matrix regressions can provide valuable evidence for the importance of dispersal as a mechanism of spatial synchrony.

Distribution, Age Structure, and Growth of Bigheaded Carps in the Lower Tennessee and Cumberland Rivers

Abstract Invasive Asian carps Hypophthalmichthys nobilis (Bighead Carp) and H. molitrix (Silver Carp), collectively referred to as bigheaded carps, were introduced to the US in the 1970s to control noxious algae blooms in aquaculture ponds. Fish subsequently escaped, and by the 1980s bigheaded carps were widespread and established in the upper Mississippi River, lower Missouri River, and the Ohio River and some of its tributaries. We sampled bigheaded carps in the lowermost reservoirs on the Tennessee River (Kentucky Lake) and Cumberland River (Lake Barkley) in 2015 and 2016 using multiple gears, including gill nets, hoop nets, electrofishing, and cast nets, to describe their distribution and estimate several population attributes. Additional electrofishing samples on the Duck River, a system renowned for its diverse ichthyofauna and mussel communities, revealed that Silver Carp range extends 220 river kilometers (rkm) upstream below the Columbia Dam. We collected a total of 737 Silver Carp and 10 Bighead...

Top-down effects of an invasive omnivore: detection in long-term monitoring of large-river reservoir chlorophyll-a

Invasive species are capable of altering ecosystems through the consumption of basal resources. However, quantifying the effects of invasive species in large ecosystems is challenging. Measuring changes in basal resources (i.e., phytoplankton) at an ecosystem scale is an important and potentially translatable response vital to the understanding of how introduced species influence ecosystems. In this study, we analyzed patterns of early summer chlorophyll-a in a large-river reservoir in response to invasion of silver carp (Hypophthalmichthys molitrix). We used 25years of ecological data from a 30-km reach of Kentucky Lake collected before and after silver carp establishment. We found significant decreases in chlorophyll-a within certain reservoir habitats since establishment of silver carp. Additionally, environmental and biological drivers of phytoplankton production showed no significant differences before and after invasion. These results suggest seasonal, and habitat-specific consumptive effects of invasive silver carp on an important basal food web resource. Further, our results convey the utility of long-term quantitative biological and physiochemical data in understanding ecosystem responses to elements of global change (i.e., species invasions). Importantly, the observed changes in the basal food web resource of Kentucky Lake may apply to other ecosystems facing invasion by silver carp (e.g., Laurentian Great Lakes). Our study offers insight into the mechanisms by which silver carp may influence ecosystems and furthers our understanding of invasive omnivores.

Chironomus Magnus, A New Name forChironomus MajorWülker and Butler, with Observations on its Ecology

ABSTRACT: Chironomus major Wulker and Butler is a junior homonym of Parachironomus major (Goetghebuer) and is replaced with Chironomus magnus. A first description of the adult is provided along with observations on its ecology in Kentucky Lake (USA) including emergence, burrowing patterns, and geographical distribution.

The Benthic Macroinvertebrates of Kentucky Lake, a Mainstem Reservoir on the Tennessee River, U.S.A.

More than 230 species of benthic macroinvertebrates are recorded from Kentucky Lake, a major reservoir on the Tennessee River system, and compiled in an annotated list. Chironomidae (Diptera) and Unionidae (mussels) comprise more than 60% of the total taxa. Most species are restricted to shallow or marginal areas of the lake with only about 12 being common everywhere. The common species were similar to those found in both large and small reservoirs in the eastern United States. High disturbance regimes and sedimentation patterns are thought to control the similarities, limiting the communities to a small suite of adaptable species. This may reduce the usefulness of reservoirs in understanding climate change. A small number of invasive benthic species are well-established but appear to have had little affect on the rest of the benthic community. Invasive zooplankton and fish seem to have had little influence on the benthos, but the recent invasion of silver carp, Hypophthalmichthys molitrix (Valenciennes), may be a tipping point.

Life history and secondary production ofHexagenia bilineata(Say) in an embayment of Kentucky Lake

Spatial distribution, life history, and secondary production of Hexagenia bilineata (Say) were studied in Ledbetter Embayment of Kentucky Lake, Kentucky, USA. We sampled the naiad population using a PONAR grab based on (1) geographically-referenced random sampling for the whole embayment, and (2) targeted sampling in a known high-density area. Secondary production was calculated with the size-frequency method. Greatest densities of naiads were collected in the shallow area (water depth <2 m) of the embayment with sediments containing gravel and sand. Mean density and biomass in the high-density transect (70.8 m−2, 587.3 mg ash-free dry mass, AFDM/m2) were more than 4× higher than estimates for the whole embayment (16.6 m−2, 121.5 mg AFDM/m2). H. bilineata population in Ledbetter Embayment had a mixed voltinism composed of two major cohorts, 14 and 22 month long with the majority of adult emergence occurring June through August. Annual production of H. bilineata was 333 mg AFDM/m2 for the embayment and 1736 mg AFDM/m2 for the high-density transect. The production of H. bilineata in Ledbetter Embayment was lower than previous estimates from similar reservoirs and lakes in the North America. The unusual spatial distribution pattern and low productivity of H. bilineata in Ledbetter Embayment were attributed to seasonal and spatial variations in water temperature and dissolved oxygen that affected naiad growth and development. H. bilineata population has been relegated from a species often responsible for a large percentage of the benthic macroinvertebrate production and carbon turnover to peripheral importance in total benthic energy flow in Ledbetter Embayment.