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USGS2024

Cytology in cnidaria using Exaiptasia as a model

A need exists for additional methods to examine cnidaria at the cellular level to aid our understanding of health, anatomy, and physiology of this important group of organisms. This need is particularly acute given that disease is emerging as a major factor in declines of ecologically important functional groups such as corals. Here we describe a simple method to process cnidarian cells for microscopic examination using the model organism Exaiptasia . We show that this organism has at least 18 cell types or structures that can be readily distinguished based on defined morphological features. Some of these cells can be related back to anatomic features of the animal both at the light microscope and ultrastructural level. The cnidome of Exaiptasia may be more complex than what is currently understood. Moreover, cnidarian cells, including some types of cnidocytes, phagocytize cells other than endosymbionts. Finally, our findings shed light on morphologic complexity of cell-associated microbial aggregates and their intimate intracellular associations. The tools described here could be useful for other cnidaria.

Diseases of Aquatic Organisms↗

USGS2004

Ultrastructure of Mycobacterium marinum granuloma in striped bass Morone saxatilis

An emerging epizootic of mycobacteriosis currently threatens striped bass Morone saxatilis populations in Chesapeake Bay, USA. Several species of mycobacteria, including Mycobacterium marinum , species resembling M. avium , M. gordonae , M. peregrinum , M. scrofulaceum and M. terrae , and the new species M. shottsii have been isolated from diseased and healthy bass. In this study, we describe the ultrastructure of developing M. marinum granulomas in experimentally infected bass over a period of 45 wk. The primary host response to injected mycobacteria was formation of large macrophage aggregations containing phagocytosed bacilli. M. marinum were always contained within phagosomes. Close association of lysosomes with mycobacterial phagosomes, as well as the presence of electron-opaque material within phagosomes, suggested phagolysosomal fusion. Development of granulomas involved epithelioid transformation of macrophages, followed by appearance of central necrosis. Desmosomes were present between mature epithelioid cells. The necrotic core region of M. marinum granulomas was separated from overlying epithelioid cells by several layers of flattened, electron-opaque spindle-shaped cells. These cells appeared to be formed by compression of epithelioid cells and, aside from a flattened nucleus, did not possess recognizable organelles. Following the development of well-defined, paucibacillary granulomas, secondary disease was observed. Recrudescence was marked by bacterial replication followed by disruption of granuloma architecture, including loss of epithelioid and spindle cell layers. In advanced recrudescent lesions, normal tissue was replaced by macrophages, fibroblasts, and other inflammatory leukocytes. Large numbers of mycobacteria were observed, both intracellular and suspended in cellular debris.

Maryland, Virginia↗

USGS2021

Viral-like particles are associated with endosymbiont pathology in Florida corals affected by stony coral tissue loss disease

Stony coral tissue loss disease (SCTLD) was first documented in 2014 near the Port of Miami, Florida, and has since spread north and south along Florida’s Coral Reef, killing large numbers of more than 20 species of coral and leading to the functional extinction of at least one species, Dendrogyra cylindrus . SCTLD is assumed to be caused by bacteria based on presence of different molecular assemblages of bacteria in lesioned compared to apparently healthy tissues, its apparent spread among colonies, and cessation of spread of lesions in individual colonies treated with antibiotics. However, light microscopic examination of tissues of corals affected with SCTLD has not shown bacteria associated with tissue death. Rather, microscopy shows dead and dying coral cells and symbiotic dinoflagellates (endosymbionts) indicating a breakdown of host cell and endosymbiont symbiosis. It is unclear whether host cells die first leading to death of endosymbionts or vice versa. Based on microscopy, hypotheses as to possible causes of SCTLD include infectious agents not visible at the light microscopy level or toxicosis, perhaps originating from endosymbionts. To clarify this, we examined corals affected with SCTLD and apparently healthy corals using transmission electron microscopy. Endosymbionts in SCTLD-affected and apparently healthy corals consistently had varying degrees of pathology associated with elongated particles compatible in morphology with filamentous positive single-stranded RNA viruses of plants termed anisometric viral-like particles (AVLP). There was apparent progression from early to late replication of AVLP in the cytoplasm of endosymbionts adjacent to or at times within chloroplasts, with morphologic changes in chloroplasts consistent with those seen in plant cells infected by viruses. Coral host cell pathology appeared limited to massive proliferation and lysis of mucus cells. Based on these findings, we hypothesize that SCTLD is a viral disease of endosymbionts leading to coral host death. Efforts to confirm the presence of a virus associated with SCTLD through other means would be appropriate. These include showing the presence of a virus through molecular assays such as deep sequencing, attempts to grow this virus in the laboratory through culture of endosymbionts, localization of virus in tissue sections using immunohistochemistry or in situ hybridization, and experimental infection of known-virus-negative corals to replicate disease at the gross and microscopic level.

Florida↗

USGS2003

Exopolymer microenvironments of microbial flora: Multiple and interactive effects on trophic relationships

Microbial cells in natural environments are often encased in different types of exopolymer secretions (EPS), ranging from tight capsules surrounding individual cells to the looser slime matrices of biofilms. The different physical and chemical properties of exopolymers could have secondary effects on trophic interactions between microbial cells and consumer animals. Laboratory studies showed that capsule EPS is significantly less digestible to consumers than slime EPS, even when extracted from the same bacterial strain. Bacterial cells with EPS capsules are less efficiently digested than noncapsuled cells, suggesting that capsules protect against digestion. Follow-up experiments determined that polysaccharide-rich fractions of slime EPS are absorbed with very high efficiencies while protein portions, which are more abundant in capsular polymers, are absorbed relatively poorly. Another series of experiments showed that dissolved organic matter (DOM), when adsorbed directly to the mineralogical portions of sediment particles, is available to deposit feeders. However, the further presence of an exopolymer coating on sediments more than doubled the bioavailability of adsorbed DOM to the consumer. Observations using cold-stage scanning electron microscopy indicated that exopolymer microenvironments are a common feature of natural marine sediments. Microbial exopolymers range from easily digestible carbon sources to relatively refractory ones that effectively protect some microbial cells from consumer digestion. Exopolymer microenvironments may also make recently adsorbed DOM highly accessible to particle-ingesting animals.

Limnology and Oceanography↗

USGS1975

Linkage effects between deposit discovery and postdiscovery exploratory drilling

For the 1950-71 period of petroleum exploration in the Powder River Basin, northeastern Wyoming and southeastern Montana, three specific topics were investigated. First, the wildcat wells drilled during the ambient phases of exploration are estimated to have discovered 2.80 times as much petroleum per well as the wildcat wells drilled during the cyclical phases of exploration, periods when exploration plays were active. Second, the hypothesis was tested and verified that during ambient phases of exploration the discovery of deposits could be anticipated by a small but statistically significant rise in the ambient drilling rate during the year prior to the year of discovery. Closer examination of the data suggests that this anticipation effect decreases through time. Third, a regression model utilizing the two independent variables of (1) the volume of petroleum contained in each deposit discovered in a cell and the directly adjacent cells and (2) the respective depths of these deposits was constructed to predict the expected yearly cyclical wildcat drilling rate in four 30 by 30 min (approximately 860 mi 2 ) sized cells. In two of these cells relatively large volumes of petroleum were discovered, whereas in the other two cells smaller volumes were discovered. The predicted and actual rates of wildcat drilling which occurred in each cell agreed rather closely.

Montana, Wyoming↗

USGS2012

Immunological and reproductive health assessment in herring gulls and black-crowned night herons in the Hudson–Raritan Estuary

Previous studies have shown inexplicable declines in breeding waterbirds within western New York/New Jersey Harbor between 1996 and 2002 and elevated polychlorinated dibenzo- p -dioxins and polychlorinated biphenyls (PCBs) in double-crested cormorant ( Phalacrocorax auritus ) eggs. The present study assessed associations between immune function, prefledgling survival, and selected organochlorine compounds and metals in herring gulls ( Larus argentatus ) and black-crowned night herons ( Nycticorax nycticorax ) in lower New York Harbor during 2003. In pipping gull embryos, lymphoid cells were counted in the thymus and bursa of Fabricius (sites of T and B lymphocyte maturation, respectively). The phytohemagglutinin (PHA) skin response assessed T cell function in gull and heron chicks. Lymphocyte proliferation was measured in vitro in adult and prefledgling gulls. Reference data came from the Great Lakes and Bay of Fundy. Survival of prefledgling gulls was poor, with only 0.68 and 0.5 chicks per nest surviving to three and four weeks after hatch, respectively. Developing lymphoid cells were reduced 51% in the thymus and 42% in the bursa of gull embryos from New York Harbor. In vitro lymphocyte assays demonstrated reduced spontaneous proliferation, reduced T cell mitogen-induced proliferation, and increased B cell mitogen-induced proliferation in gull chicks from New York Harbor. The PHA skin response was suppressed 70 to 80% in gull and heron chicks. Strong negative correlations ( r = –0.95 to –0.98) between the PHA response and dioxins and PCBs in gull livers was strong evidence suggesting that these chemicals contribute significantly to immunosuppression in New York Harbor waterbirds.

New Jersey, New York↗

USGS2019

Wetland management strategy to reduce mercury export in water and bioaccumulation in fish

Wetland environments provide numerous ecosystem services but also facilitate methylmercury (MeHg) production and bioaccumulation. We developed a wetland‐management technique to reduce MeHg concentrations in wetland fish and water. We physically modified seasonal wetlands by constructing open‐ and deep‐water treatment cells at the downstream end of seasonal wetlands to promote naturally occurring MeHg‐removal processes. We assessed the effectiveness of reducing mercury (Hg) concentrations in surface water and western mosquitofish that were caged at specific locations within 4 control and 4 treatment wetlands. Methylmercury concentrations in wetland water were successfully decreased within treatment cells during only the third year of study; however, treatment cells were not effective for reducing total Hg concentrations. Furthermore, treatment cells were not effective for reducing total Hg concentrations in wetland fish. Mercury concentrations in fish were not correlated with total Hg concentrations in filtered, particulate, or whole water; and the slope of the correlation with water MeHg concentrations differed between months. Fish total Hg concentrations were weakly correlated with water MeHg concentrations in April when fish were introduced into cages but were not correlated in May when fish were retrieved from cages. Fish total Hg concentrations were greater in treatment wetlands than in control wetlands the year after the treatment wetlands’ construction but declined by the second year. During the third year, fish total Hg concentrations increased in both control and treatment wetlands after an unexpected regional flooding event. Overall, we found limited support for the use of open‐ and deep‐water treatment cells at the downstream end of wetlands to reduce MeHg concentrations in water but not fish. We suggest that additional evaluation over a longer period of time is necessary.

Environmental Toxicology and Chemistry↗

USGS2011

Toxic effects of dietary methylmercury on immune function and hematology in American kestrels (Falco sparverius)

Fifty-nine adult male American kestrels ( Falco sparverius ) were assigned to one of three diet formulations including 0 (control), 0.6, and 3.9 μg/g (dry wt) methylmercury (MeHg). Kestrels received their diets daily for 13 weeks to assess the effects of dietary MeHg on immunocompetence. Immunotoxic endpoints included assessment of cell-mediated immunity (CMI) using the phytohemagglutinin (PHA) skin-swelling assay and primary and secondary antibody-mediated immune responses (IR) via the sheep red blood cell (SRBC) hemagglutination assay. Select hematology and histology parameters were evaluated to corroborate the results of functional assays and to assess immunosuppression of T and B cell-dependent components in spleen tissue. Kestrels in the 0.6 and 3.9 μg/g MeHg groups exhibited suppression of CMI, including lower PHA stimulation indexes ( p = 0.019) and a 42 to 45% depletion of T cell-dependent splenic lymphoid tissue ( p = 0.006). Kestrels in the 0.6 μg/g group exhibited suppression of the primary IR to SRBCs ( p = 0.014). MeHg did not have a noticeable effect on the secondary IR ( p = 0.166). Elevation of absolute heterophil counts ( p < 0.001), the heterophil to lymphocyte ratio ( p < 0.001), and total white blood cell counts ( p = 0.003) was apparent in the 3.9 μg/g group at week 12. Heterophilia, or the excess of heterophils in peripheral blood above normal ranges, was apparent in seven of 17 (41%) kestrels in the 3.9 μg/g group and was indicative of an acute inflammatory response or physiological stress. This study revealed that adult kestrels were more sensitive to immunotoxic effects of MeHg at environmentally relevant dietary concentrations than they were to reproductive effects as previously reported.

Environmental Toxicology and Chemistry↗

USGS2000

A flow cytometric approach to the study of crustacean cellular immunity

Responses of hemocytes from the crayfish Procambarus zonangulus to stimulation by fungal cell walls (Zymosan A) were measured by flow cytometry. Changes in hemocyte physical characteristics were assessed flow cytometrically using forward- and sidescatter light parameters, and viability was measured by two-color fluorescent staining with calcein-AM and ethidium homodimer 1. The main effects of zymosan A on crayfish hemocytes were reduction in cell size and viability compared to control mixtures (hemocytes in buffer only). Adding diethyldithiocarbamic acid, an inhibitor of phenoloxidase, to hemocyte to zymosan mixtures delayed the time course of cell size reduction and cell death compared to zymosan-positive controls. The inclusion of trypsin inhibitor in reaction mixtures further delayed the reduction in hemocyte size and cell death, thereby indicating that a proteolytic cascade, along with prophenoloxidase activation, played a key role in generating signal molecules which mediate these cellular responses. In addition to traditional methods such as microscopy and protein chemistry, flow cytometry can provide a simple, reproducible, and sensitve method for evaluating invertebrate hemocyte responses to immunological stimuli.

Journal of Invertebrate Pathology↗

USGS2019

Establishing genome sizes of focal fishery and aquaculture species along Baja California, Mexico

Genome size—the total haploid content of nuclear DNA— is constant in all cells in individuals within a species, but differs among species. Consequently, the genome size is a quantifiable genetic signature that not only characterizes a species, but it can reflect chromatin modifications, which play fundamental roles in most biological processes that are involved in the manipulation and expression of DNA. This characteristic makes the genome size a crucial parameter for genetic research on endemic aquatic species and for genetic manipulations in aquaculture species. Technologies for genetic assessments and improvements applied to fishery and aquaculture species use genome size values as a means by which hybrids, polyploids, and sex can be identified, when sex chromosomes exist. The objectives of this study were to determine genome sizes of aquatic species with economic and biological importance along the Pacific coast of Mexico, as well as to identify the appropriate reference standards for use in this study. Blood, hemolymph or milt were collected from 10 species occurring along the coast of Baja California: Sablefish Anoplopoma fimbria , Black Snapper Lutjanus novemfasciatus , California Halibut Paralichthys californicus , Pacific Sardine Sardinops sagax , Flag Rockfish Sebastes rubrivinctus , Starry Rockfish Sebastes constellatus, Totoaba Totoaba macdonaldi , Whiteleg Shrimp Litopenaeus vannamei and two Yellowtail Seriola lalandi and S. dorsalis . Nuclear DNA was stained with propidium iodide solution and the genome size was determined by flow cytometry, with results ranging from 0.61 pg (1.22 pg/diploid cell) to 2.59 pg (5.18 pg/diploid cell), with the smallest value in Sablefish and the largest in the Whiteleg Shrimp. No significant differences were detected ( P ≤ 0.05) among individuals of the same species; the likely reason behind any dissimilar DNA content values with those from the literature were differences in methodologies or variations in genetics. Red-ear Slider Turtle Trachemys scripta elegans 2.65 pg (5.30 pg/diploid cell) and Red Junglefowl Gallus gallus 1.27 pg (2.54 pg/diploid cell) were chosen as the standards for reference values. These results establish the basis for the Mexican National Aquatic Genetic Resources project supporting genetic improvements for aquaculture and conservation status parameters for fisheries species.

Baja California↗

USGS1992

Petrographic and anatomical characteristics of plant material from two peat deposits of Holocene and Miocene age, Kalimantan, Indonesia

Samples from two peat-forming environments of Holocene and Miocene age in Kalimantan (Borneo), Indonesia, were studied petrographically using nearly identical sample preparation and microscopic methodologies. Both deposits consist of two basic types of organic material: plant organs/tissues and fine-grained matrix. There are seven predominant types of plant organs and tissues: roots possessing only primary growth, stems possessing only primary growth, leaves, stems/roots with secondary growth, secondary xylem fragments, fragments of cork cells, and macerated tissue of undetermined origin. The fine-grained matrix consists of fragments of cell walls and cell fillings, fungal remains, spores and pollen grains, and resin. Some of the matrix material does not have distinct grain boundaries (at ??500) and this material is designated amorphous matrix. The major difference between the Holocene peat and Miocene lignite in reflected light, oil immersion is a loss of red coloration in the cell walls of tissue in the lignite, presumably due to loss of cellulosic compounds. In addition, cortex and phloem tissue (hence primary roots and stems) are difficult to recognize in the lignite, probably because these large, thin-walled tissues are more susceptible to microbial degradation and compaction. Particle size in both peat and lignite samples display a bimodal distribution when measurements are transformed to a - log2 or phi (??), scale. Most plant parts have modes of 2-3?? (0.25 - 0.125 mm), whereas the finer-grained particulate matrix has modes of 7-9?? (0.008-0.002 mm). This similarity suggest certain degradative processes. The 2-3?? range may be a "stable" size for plant parts (regardless of origin) because this is a characteristics of a substrate which is most suitable for plant growth in peat. The finer-grained matrix material (7-9??) probably results from fungal decay which causes plant material to weaken and with slight physical pressure to shatter into its component parts, i.e. fragments of cell walls and fillings. The absence of differences in particle size between the peat and lignite also indicate little compaction of organic components; rather an extreme loss in water content and pore space has occurred from between the particles of organic material. ?? 1992.

Review of Palaeobotany and Palynology↗

USGS2013

A wetting and drying scheme for ROMS

The processes of wetting and drying have many important physical and biological impacts on shallow water systems. Inundation and dewatering effects on coastal mud flats and beaches occur on various time scales ranging from storm surge, periodic rise and fall of the tide, to infragravity wave motions. To correctly simulate these physical processes with a numerical model requires the capability of the computational cells to become inundated and dewatered. In this paper, we describe a method for wetting and drying based on an approach consistent with a cell-face blocking algorithm. The method allows water to always flow into any cell, but prevents outflow from a cell when the total depth in that cell is less than a user defined critical value. We describe the method, the implementation into the three-dimensional Regional Oceanographic Modeling System (ROMS), and exhibit the new capability under three scenarios: an analytical expression for shallow water flows, a dam break test case, and a realistic application to part of a wetland area along the Georgia Coast, USA.

Georgia↗

USGS2004

Inhibition and enhancement of microbial surface colonization: the role of silicate composition

Classical treatment of cell attachment by models of filtration or coulombic attraction assumes that attachment of cells to mineral surfaces would be controlled by factors such as response to predation, collision efficiency, or coulombic attraction between the charged groups at the mineral and cell surfaces. In the study reported here, the passive model of attachment was investigated using a native microbial consortium and a variety of Al- and Fe-bearing silicates and oxides to determine if other controls, such as mineral composition, also influence the interaction between cells and surfaces. Results from in situ colonization studies in an anaerobic groundwater at pH 6.8 combined with most probable number analyses (MPN) of surface-adherent cells demonstrate that electrostatic effects dominate microbial colonization on positively charged oxide surfaces regardless of mineral composition. In contrast, on negatively charged silicate minerals and glasses, the solid phase composition is a factor in determining the extent of microbial colonization, as well as the diversity of the attached community. In particular, silicates containing more than 1.2% Al exhibit less biomass than Al-poor silicates and MPN suggests a shift in community diversity, possibly indicating Al toxicity on these surfaces. When Fe is present in the silicate, however, this trend is reversed and abundant colonization of the surface is observed. Here, microorganisms preferentially colonize those silicate surfaces that offer beneficial nutrients and avoid those that contain potentially toxic elements.

Chemical Geology↗

USGS2010

Absorption and biotransformation of polybrominated diphenyl ethers DE-71 and DE-79 in chicken (Gallus gallus), mallard (Anas platyrhynchos), American kestrel (Falco sparverius) and black-crowned night-heron (Nycticorax nycticorax) eggs

We recently reported that air cell administration of penta-brominated diphenyl ether (penta-BDE; DE-71) evokes biochemical and immunologic effects in chicken (Gallus gallus) embryos at very low doses, and impairs pipping (i.e., stage immediately prior to hatching) and hatching success at 1.8 ug g-1 egg (actual dose absorbed) in American kestrels (Falco sparverius). In the present study, absorption of polybrominated diphenyl ether (PBDE) congeners was measured following air cell administration of a penta-BDE mixture (11.1 ug DE-71 g-1 egg) or an octa-brominated diphenyl ether mixture (octa-BDE; DE-79; 15.4 ug DE-79 g-1 egg). Uptake of PBDE congeners was measured at 24 h post-injection, midway through incubation, and at pipping in chicken, mallard (Anas platyrhynchos), and American kestrel egg contents, and at the end of incubation in black-crowned night-heron (Nycticorax nycticorax) egg contents. Absorption of penta-BDE and octa-BDE from the air cell into egg contents occurred throughout incubation; at pipping, up to 29.6% of penta-BDE was absorbed, but only 1.40-6.48% of octa-BDE was absorbed. Higher brominated congeners appeared to be absorbed more slowly than lower brominated congeners, and uptake rate was inversely proportional to the log Kow of predominant BDE congeners. Six congeners or co-eluting pairs of congeners were detected in penta-BDE-treated eggs that were not found in the dosing solution suggesting debromination in the developing embryo, extraembryonic membranes, and possibly even in the air cell membrane. This study demonstrates the importance of determining the fraction of xenobiotic absorbed into the egg following air cell administration for estimation of the lowest-observed-effect level.

Chemosphere↗

USGS2011

Increasing accuracy of dispersal kernels in grid-based population models

Dispersal kernels in grid-based population models specify the proportion, distance and direction of movements within the model landscape. Spatial errors in dispersal kernels can have large compounding effects on model accuracy. Circular Gaussian and Laplacian dispersal kernels at a range of spatial resolutions were investigated, and methods for minimizing errors caused by the discretizing process were explored. Kernels of progressively smaller sizes relative to the landscape grid size were calculated using cell-integration and cell-center methods. These kernels were convolved repeatedly, and the final distribution was compared with a reference analytical solution. For large Gaussian kernels ( σ > 10 cells), the total kernel error was <10 −11 compared to analytical results. Using an invasion model that tracked the time a population took to reach a defined goal, the discrete model results were comparable to the analytical reference. With Gaussian kernels that had σ ≤ 0.12 using the cell integration method, or σ ≤ 0.22 using the cell center method, the kernel error was greater than 10%, which resulted in invasion times that were orders of magnitude different than theoretical results. A goal-seeking routine was developed to adjust the kernels to minimize overall error. With this, corrections for small kernels were found that decreased overall kernel error to <10 −11 and invasion time error to <5%.

Ecological Modelling↗

USGS2005

Control of Fe(III) site occupancy on the rate and extent of microbial reduction of Fe(III) in nontronite

A quantitative study was performed to understand how Fe(III) site occupancy controls Fe(III) bioreduction in nontronite by Shewanella putrefaciens CN32. NAu-1 and NAu-2 were nontronites and contained Fe(III) in different structural sites with 16 and 23% total iron (w/w), respectively, with almost all iron as Fe(III). Mo??ssbauer spectroscopy showed that Fe(III) was present in the octahedral site in NAu-1 (with a small amount of goethite), but in both the tetrahedral and the octahedral sites in NAu-2. Mo??ssbauer data further showed that the octahedral Fe(III) in NAu-2 existed in at least two environments- trans (M1) and cis (M2) sites. The microbial Fe(III) reduction in NAu-1 and NAu-2 was studied in batch cultures at a nontronite concentration of 5 mg/mL in bicarbonate buffer with lactate as the electron donor. The unreduced and bioreduced nontronites were characterized by X-ray diffraction (XRD), Mo??ssbauer spectroscopy, and transmission electron microscopy (TEM). In the presence of an electron shuttle, anthraquinone-2,6-disulfonate (AQDS), the extent of bioreduction was 11%-16% for NAu-1 but 28%-32% for NAu-2. The extent of reduction in the absence of AQDS was only 5%-7% for NAu-1 but 14%-18% for NAu-2. The control experiments with heat killed cells and without cells did not show any appreciable reduction (<2%). The extent of reduction in experiments performed with a dialysis membrane to separate cells from clays (without AQDS) was 2%-3% for NAu-1 but 5%-7% for NAu-2, suggesting that cells probably released an electron shuttling compound and/or Fe(III) chelator. The reduction rate was also faster in NAu-2 than that in NAu-1. Mo??ssbauer data of the bioreduced nontronite materials indicated that the Fe(III) reduction in NAu-1 was mostly from the presence of goethite, whereas the reduction in NAu-2 was due to the presence of the tetrahedral and trans-octahedral Fe(III) in the structure. The measured aqueous Fe(II) was negligible. As a result of bioreduction, the average nontronite particle thickness remained nearly the same (from 2.1 to 2.5 nm) for NAu-1, but decreased significantly from 6 to 3.5 nm for NAu-2 with a concomitant change in crystal size distribution. The decrease in crystal size suggests reductive dissolution of nontronite NAu-2, which was supported by aqueous solution chemistry (i.e., aqueous Si). These data suggest that the more extensive Fe(III) bioreduction in NAu-2 was due to the presence of the tetrahedral and the trans-octahedral Fe(III), which was presumed to be more reducible. The biogenic Fe(II) was not associated with biogenic solids or in the aqueous solution. We infer that it may be either adsorbed onto surfaces of nontronite particles/bacteria or in the structure of nontronite. Furthermore, we have demonstrated that natural nontronite clays were capable of supporting cell growth even in medium without added nutrients, possibly due to presence of naturally existing nutrients in the nontronite clays. These results suggest that crystal chemical environment of Fe(III) is an important determinant in controlling the rate and extent of microbial reduction of Fe(III) in nontronite. Copyright ?? 2005 Elsevier Ltd.

Geochimica et Cosmochimica Acta↗

USGS2017

Influence of genetic background, salinity, and inoculum size on growth of the ichthyotoxic golden alga (Prymnesium parvum)

Salinity (5–30) effects on golden alga growth were determined at a standard laboratory temperature (22 °C) and one associated with natural blooms (13 °C). Inoculum-size effects were determined over a wide size range (100–100,000 cells ml −1 ). A strain widely distributed in the USA, UTEX-2797 was the primary study subject but another of limited distribution, UTEX-995 was used to evaluate growth responses in relation to genetic background. Variables examined were exponential growth rate ( r ), maximum cell density (max-D) and, when inoculum size was held constant (100 cells ml −1 ), density at onset of exponential growth (early-D). In UTEX-2797, max-D increased as salinity increased from 5 to ∼10–15 and declined thereafter regardless of temperature but r remained generally stable and only declined at salinity of 25–30. In addition, max-D correlated positively with r and early-D, the latter also being numerically highest at salinity of 15. In UTEX-995, max-D and r responded similarly to changes in salinity − they remained stable at salinity of 5–10 and 5–15, respectively, and declined at higher salinity. Also, max-D correlated with r but not early-D. Inoculum size positively and negatively influenced max-D and r , respectively, in both strains and these effects were significant even when the absolute size difference was small (100 versus 1000 cells ml −1 ). When cultured under similar conditions, UTEX-2797 grew faster and to much higher density than UTEX-995. In conclusion, (1) UTEX-2797’s superior growth performance may explain its relatively wide distribution in the USA, (2) the biphasic growth response of UTEX-2797 to salinity variation, with peak abundance at salinity of 10–15, generally mirrors golden alga abundance-salinity associations in US inland waters, and (3) early cell density – whether artificially manipulated or naturally attained – can influence UTEX-2797 bloom potential.

Harmful Algae↗

USGS2015

Validation of a spatial model used to locate fish spawning reef construction sites in the St. Clair–Detroit River system

Lake sturgeon ( Acipenser fulvescens ) populations have suffered precipitous declines in the St. Clair–Detroit River system, following the removal of gravel spawning substrates and overfishing in the late 1800s to mid-1900s. To assist the remediation of lake sturgeon spawning habitat, three hydrodynamic models were integrated into a spatial model to identify areas in two large rivers, where water velocities were appropriate for the restoration of lake sturgeon spawning habitat. Here we use water velocity data collected with an acoustic Doppler current profiler (ADCP) to assess the ability of the spatial model and its sub-models to correctly identify areas where water velocities were deemed suitable for restoration of fish spawning habitat. ArcMap 10.1 was used to create raster grids of water velocity data from model estimates and ADCP measurements which were compared to determine the percentage of cells similarly classified as unsuitable, suitable, or ideal for fish spawning habitat remediation. The spatial model categorized 65% of the raster cells the same as depth-averaged water velocity measurements from the ADCP and 72% of the raster cells the same as surface water velocity measurements from the ADCP. Sub-models focused on depth-averaged velocities categorized the greatest percentage of cells similar to ADCP measurements where 74% and 76% of cells were the same as depth-averaged water velocity measurements. Our results indicate that integrating depth-averaged and surface water velocity hydrodynamic models may have biased the spatial model and overestimated suitable spawning habitat. A model solely integrating depth-averaged velocity models could improve identification of areas suitable for restoration of fish spawning habitat.

Michigan↗