Kyle D. Hoagland

University of Nebraska at Lincoln | NU · School of Natural Resources

The cyanobacterial neurotoxin β - N -methylamino-L-alanine (BMAA) is considered to be an “excitotoxin,” and its suggested mechanism of action is killing neurons. Long-term exposure to L-BMAA is believed to lead to neurodegenerative diseases including Parkinson’s and Alzheimer’s diseases and amyotrophic lateral sclerosis (Lou Gehrig’s disease). Obje...

Several groups of microorganisms are capable of producing toxins in aquatic environments. Cyanobacteria are prevalent blue green algae in freshwater systems, and many species produce cyanotoxins which include a variety of chemical irritants, hepatotoxins and neurotoxins. Production and occurrence of potent neurotoxic cyanotoxins β-N-methylamino-l-a...

Recently developed hillslope storage dynamics theory can represent the essential physical behavior of a natural system by accounting explicitly for the plan shape of a hillslope in an elegant and simple way. As a result, this theory is promising for improving catchment-scale hydrologic modeling. In this study, grid digital elevation model (DEM) bas...

Periphyton diversity was highest at low to intermediate levels of grazing by the freshwater snail Physella and suppressed at high grazer densities, in partial support of the intermediate disturbance hypothesis. For the first time, the response curve of algal biomass versus a range of snail densities was used to establish low, intermediate, and high...

The effects of total phosphorus reduction on a lake community were investigated in a microcosm study involving 15 1000-L tanks containing natural plankton assemblages. A 28-day replicated gradient-design tank study was conducted, which included five treatments with three replicates each. (i-iii) three treatment levels of ferric sulfate, a phosphoru...

The function of diatom mucilage in the formation of spatially complex periphyton communities was investigated in McConaughy reservoir (Nebraska, U.S.A.). Seasonal biofilms on natural and artificial substrates revealed high densities of periphytic diatoms (up to 3.5 × 104 cells mm-2). Growth habits of the dominant taxa (short stalk, Achnanthes minut...

Extracellular polymeric substance (EPS) secretion was examined in the stalked marine diatom Achnanthes longipes Ag. in defined medium. This common biofouling diatom exhibited an absolute requirement for bromide for stalk production and substratum attachment, whereas elevated iodide concentrations in the growth medium inhibited stalk formation and a...

Nebraska agencies and public health organizations collaboratively addressed cyanobacterial issues for the first time after two dogs died within hours of drinking water from a small private lake south of Omaha on May 4, 2004. A necropsy on one of the dogs revealed that the cause of death was due to ingestion of Microcystin toxins. Within two weeks a...

Effectiveness of filter strips may change over a period of years because key soil and vegetation conditions change after conversion of cultivated farmland to permanent vegetation. The main objectives of this study were to: 1) determine if effectiveness of a filter strip changes over years since establishment, and 2) determine if temporal change dep...

Wetland restoration typically includes modifications to soils, flora, and hydrology. Will the return of wetland hydrology to former saline wetlands create conditions suitable for wetland taxa, especially saline wetland indicator species? To answer this question we evaluated the potential restoration efficacy of historical saline wetland soils by re...

We describe effect of a pathogen that spread through a dense, rapidly growing, benthic diatom community during two infection periods (February and mid-April 1991) in Sycamore Creek, Arizona. Infected areas appeared as gray rings within a matrix of healthy diatom growth and spread rapidly, eventually covering all benthic substrata and causing algal...

The development of the mucilage on the outer surface of Navicula confervacea (Kütz.) Grun., a raphed, filamentous diatom, was studied with scanning electron microscopy. This nonstructural cell wall material, present on the surface after critical-point drying and absent after acid cleaning, was of two types: strands and papillae. Strands were associ...

Adverse weather and resultant turbulence caused sloughing of attached diatom communities during the first two weeks of colonization on artificial substrates. In contrast to Pacific macroalgal systems, older communities (8–12 d) were the most affected by wave action. Ash-free dry weight of the periphyton and diatom cell density generally increased,...

Experimental field manipulations of artificial substrata were used to examine the mechanisms controlling attached algal zonation down the face of the dam in Lake McConaughy, a large reservoir in western Nabraska. Sets of clay tiles were incubated in the upper (2.5 m depth) and lower (8 m depth) growth zones for two weeks. Five sets tiles were then...

Achnanthes longipes Ag. is a marine stalk-forming diatom that grows in dense biofilms. The effects of cell density, temperature, and light on growth and stalk production were examined in the laboratory to determine how they affected the ability of this diatom to form a biofilm. Stalk production abruptly increased when A. longipes was cultured at a...

Concentrated flow of surface runoff from agricultural fields may limit the capability of riparian buffers to remove pollutants. This study was conducted on four farms in southeastern Nebraska to develop a method for assessing the extent of concentrated flow in riparian buffers and for evaluating the impact that it has on sediment-trapping efficienc...

In agriculturally dominated regions, land use practices have an unusually large impact on water bodies and, therefore, land use may reduce the utility of current ecoregion-based approaches to lake classification by dampening the signals that underlie the ecoregion framework. A team of water quality researchers has been assembled to develop a compre...

A model combining algal mortality due to selective zooplankton grazing with the Monod model of phytoplankton growth was used to predict phytoplankton species composition along a gradient of phosphorus (P) concentration and zooplankton grazing pressure. Model predictions were compared to the results of a mesocosm experiment of phytoplankton species...

Filter strips are widely prescribed to reduce contaminants in surface runoff from agricultural fields. This study compared performance of different filter strip designs on several contaminants and evaluated the contributing processes. Different vegetation types and widths were investigated using simulated runoff event on large plots (3 m x 7.5 or 1...

The effects of prior chronic exposure to atrazine on responses to subsequent acute exposures were investigated using a common benthic diatom. Clonal, axenic cultures of Craticula cuspidata were established from the Platte River (Nebraska) and obtained from a culture collection (unlikely prior exposure to atrazine). All cultures received a chronic 6...

The effects of a reduction in total phosphorus concentration on the water quality and plankton community structure in a 86-ha hypereutrophic sandpit lake with high internal phosphorus loading were assessed by dosing an isolated 4.6-ha section of the lake with 34,065 L (dose = 10 mg Al·L) of liquid aluminum sulfate (alum). During the three summers f...

The attachment of diatoms to surfaces is an important and poorly understood step in the development of biofouling communities. Experiments were performed in vitro on a common fouling diatom (Achnanthes longipes) to determine the influence of the base material and bacterial conditioning on diatom attachment. The first series of experiments compared...

A duplicated factorial approach was used to assess the combined effects of three environmentally realistic levels of alachlor (0.0, 5.0, and 90.0 μg/L), cross-classified with three environmentally realistic levels of atrazine (0.0, 12.0, and 150.0 μg/L), on indigenous epipelic algae (mud-dwelling species, characteristic of agricultural streams). Th...

Atrazine bioconcentration and uptake were determined for eight freshwater green algae and diatoms. Atrazine uptake was extremely rapid in all species examined, with nearly 90% of total uptake occurring within the first hour of exposure. Within each division, different species had different bioconcentration capacities, although the accumulation of a...

Glutathione-S-transferase (GST) activity toward atrazine and a model substrate was characterized in eight species of freshwater algae. All algal species exhibited measurable GST activity, and the involvement of these enzymes in atrazine metabolism was indicated by the glutathione-dependent formation of water soluble metabolites. Significant differe...

We have answered fundamental questions regarding the mechanisms of attachment and the nature of the biocomposite adhesives utilized by the marine biofouling diatom Achnanthes longipes and the freshwater Cymbella cistula. During the course of this grant we have: (1) delineated the sequence of events involved in attachment of the organisms to a varie...

The effects of a single pulse, 21-d exposure of the commonly used herbici de a achlor (2-chloro-2′, 6′-diethyl-N-methoxymethyl acetanilide) on an algal community from a typical agricultural stream in Nebraska were studied using 18 stream microcosms located in a greenhouse, at six alachlor concentrations (0, 1, 10, 30, 100, and 1,000 μg/L). Effects...

Genetic variation in 126 clones of the planktonic diatom,Fragilaria capucina, collected from seven lakes from Manitoba to Texas, was determined by RAPD analysis. Five primers yielded 48 scorable RAPD fragments in 123 unique combinations. Patterns of genetic variation were analysed by cluster analysis, which showed that most clones grouped together...

The effects of reservoir aging on the phytoplankton community of amidwestern U.S. reservoir constructed in 1965 (Pawnee Reservoir) werestudied by comparing algal biovolume and species composition from April 1992through November 1992 to surveys conducted in 1968–73 and 1990. Meansummer total phosphorus, nitrate-nitrogen, Secchi disk depth, totalsusp...

Changes in zooplankton diversity and density in response to reservoir aging in Pawnee Reservoir were investigated. Zooplankton samples collected from April 1992 through April 1993, were compared to a similar study conducted after initial impoundment by Helzer (1971), in 1968–1970. Since this initial study, increases in turbidity and resulting chang...

The relative effects of light intensity, color, and UV radiation on the herbivory component of an epilithic food web were examined in a small spring-fed stream in the Sand Hills region of western Nebraska. Plexiglass, solar-radiation filters were suspended over artificial substrata at 4 sites with open riparian canopies. Periphyton and macroinverte...

The effects of reservoir aging on the benthic macroinvertebrate community in Pawnee Reservoir were documented by comparing species composition and biomass of samples collected from October 1991 through September 1992, to a similar survey conducted in 1968–70 by Hergenrader & Lessig (1980). Filling of the basin with sediment and associated material...

In Sycamore Creek, Arizona, infected areas appeared as gray rings within a matrix of healthy diatom growth and spread rapidly, eventually covering all benthic substrata and causing algal sloughing. A pathogenic bacterium was the most probable cause of this phenomenon. -from Authors

Influences of the transmission properties of the riparian canopy and the water column on spectral irradiance and periphyton composition were examined at four sites in Otter Creek, a small spring-fed stream in the Sand Hills region of western Nebraska. Values for per cent sky in the canopy at the four sites were: 65.1% (open site), 31.9% (partial sh...

The acute toxicities of four recently developed pyrethroid insecticides (bifenthrin, cyfluthrin, lambda cyhalothrin and tralomethrin) were experimentally compared to the acute toxicity of a first generation pyrethroid (permethrin), in static-flow, 48-h bioassays with Daphnia magna and Ceriodaphnia dubia. The four new generation pyrethroids exhibite...

The impact of short-term atrazine exposures on attached algal community composition and standing crop was investigated during the summer in a small, spring-fed stream in western Nebraska. Replicate trays of clay tiles were anchored to the stream bed, allowed to colonize for two weeks, then enclosedin situ with plexiglass boxes and exposed to a puls...

Microalgal communities on clay tiles in Lake McConaughy (Nebraska, USA) were subjected to simulated wave disturbance after 6, 12, 18, or 24 d of development to examine the effects of community age on resistance and recovery in these communities. Six-day communities were less resistant than older communities; diatom standing crops in 6-d communities...

Diatom-dominated biofilm communities which developed in one-month periods over two years were monitored in tributaries of a small eutrophic prairie stream with agricultural watershed subject to extensive soil erosion. Site A, which was spring fed, had a year-round flow, the highest silica and nitrate-nitrogen levels, and a distinct diatom community...

The source of algal colonizers onto rock substrates in a eutrophic reservoir was analyzed during the spring diatom pulse by placing sediment traps in and beyond the periphyton growth zone and by scraping intact surfaces of known age. Impingement or "raining" of diatom cells from the water column was more important in the recolonization of rock surf...

Glass microscope slides were immersed in the tiny Headwaters of a midwestern stream Achnanthes lanceolata (Bréb.) Grunow was the dominant or co-dominant species in 14 out of 15 one-month-old communities over a two-year period. Minutely streaked, periphyton-free areas mostly lacked live diatoms but had cell-free mucilage pads and attached raphe valv...

Deep-water sediment cores from 32 Scandinavian and 19 northern New England, U.S.A., lakes were analyzed for 137Cs; 210Pb was analyzed in cores from 16 and 14 of these lakes, respectively. Additional dating of the New England cores was based on chronostratigraphic pollen markers. The profiles in sediment of 137Cs deviate greatly from expectations ba...

Acid-cleaned, uncoated diatom cell walls examined with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) indicated a porous or granular siliceous matrix; however, high resolution scanning electron microscopy (SEM) revealed no such features on uncoated walls. To demonstrate such features with SEM it was nece...

An initial thermal evaporative coating with Au/Pd protects delicate biological surfaces from thermal damage caused by diode sputtering, allowing additional coating if necessary by the quicker and more complete sputtering method. Additional coating by either method (1) reduces charging and bright areas, (2) improves the physical stability of entire...

We call attention to the occurrence of an oily residue in the CPD bomb after critical point drying, as well as the presence of rust, dirt, and an oily residue in CO2 and Freon supply cylinders. Bottled gas is often tested for purity once after manufacturing and then is pumped and stored, perhaps several times, before the consumer's cylinders are fi...

The attenuation of down-welling quantum irradiance (400–700 nm) was monitored seasonally in three eutrophic Nebraska reservoirs from July, 1975, to June, 1976. Measurements were made at four stations in McConaughy, three in Pawnee, and three in Yankee Hill using a commercially available, quantum irradiance sensor. The mean vertical attenuation coef...

Acid cleaned cells from clonal cultures of Fragilaria capucina var. mesolepta Rabh. were examined with light and scanning electron microscopy. Recently isolated cells are linear-lanceolate in shape with a median constriction. After several transfers over 25 mo, cells exhibit size diminution resulting in small elliptically shaped valves. Adjacent va...

This cooperative Augmentation Award for Science and Engineering Research Training has provided training for two doctoral students in several important areas of marine microalgal biofouling, including marine diatom mass culturing and adhesive isolation, biochemistry of adhesives, and laboratory experiments on the effects of substrate preconditioning...