Geomorphic response of a headwater channel to augmented flow

Since 1974, flow releases from Long Draw Reservoir have increased annual peak flows on La Poudre Pass Creek, Colorado, from ~ 5.6 m³/s to > 8.4 m³/s. The creek drains 61 km² and channel morphology varies from step-pool to pool-riffle. Comparison of five channel reaches along the creek to channel reaches along neighboring rivers without flow regulation indicates that channel width has increased by as much as a factor of three along La Poudre Pass Creek. Width-to-depth ratio has also increased, the bed material in step-pool channel reaches has coarsened, and residual pool volumes have increased in pool-riffle channel reaches. Pool-riffle channel reaches have undergone the greatest change in response to flow augmentation. Although discharge has increased consistently for all five channel reaches, morphologic response varies in relation to gradient and channel morphology, making it impractical to precisely predict a priori the magnitude of channel response to flow augmentation.     

Separation of core and intact polar archaeal tetraether lipids using silica columns: Insights into living and fossil biomass contributions

Intact polar lipids (IPLs) are frequently used as biomarkers for living microbial cells and can be separated from core lipids (i.e. lipids without polar headgroups), which are mainly derived from fossil (i.e. dead) cell material, using column chromatography. We have compared the effect of various silica column conditions on the separation and recovery of archaeal glycerol dialkyl glycerol tetraether (GDGT) core lipids, glycolipids and phosphoglycolipids using authentic standards and direct analysis with various high performance liquid chromatography-mass spectrometry (HPLC-MS) techniques. The commonly used procedure to separate these compound classes using dichloromethane, acetone and methanol as eluents, respectively, did not separate core GDGTs from glyco- and phosphoglyco-GDGTs. In contrast, a recently described procedure using hexane:ethyl acetate (3:1, v:v), ethyl acetate and methanol achieved both high recovery and successful separation of core GDGTs from the other IPLs. Application of the method to a geothermally heated soil and suspended particulate matter from the North Sea showed that it separates most of the core GDGTs from the other IPLS and that considerable qualitative and quantitative differences can occur between core and IPL-GDGTs. We conclude that the method is therefore appropriate for the separation of intact archaeal IPLs and their fossil analogues.     

LOCATIONAL PROBLEMS AND PREFERENCES IN PRESCHOOL CHILD CARE*

With the increased use of formal child care, the number of child care alternatives has grown. The locational problems and preferences of University of Connecticut employees who use formal child care for children under age 6 are examined because an on-site program is available as one option. Difficulty finding care at a convenient location is related to residential location. Preference for worksite care decreases with increasing commuting distance. Variations in reported locational preferences by commuting zone are consistent with the notion of locating services within the activity spaces of the users. As commuting distance increases, worksite day care represents a greater displacement from the activity spaces of the child and possibly of other family members.     

Behavioural response of blackfly larvae (Simuliidae, Diptera) to different current velocities

Video equipment was used to record and to compare the behaviour of different blackfly species at two flow velocities 0.25 m s⁻¹ and 1.35 m s⁻¹. Simulium noelleri Friederichs, Simulium ornatum (complex) Meigen and Simulium variegatum Meigen were studied. Effects of flow velocity on larval locomotive activties were analysed. Looping activity and the time needed to attach for filter feeding again were affectet to some extend, depending on species and flow velocity. While in S. ornatum no differences were recorded in locomotive activity, larvae of S. noelleri and S. variegatum were less active at high flow velocities. Larvae of S. noelleri also moved over shorter distances when exposed to high flow velocities. Consequences of the differences in behavioural response to flow velocities are discussed with respect to drift and silk pad adhesion.     

Gelelectrophoretic studies on labial gland secretions of immature blackflies (Simuliidae, Diptera)

Any contact of blackfly larvae and pupae to the substrate they colonise relies on the adhesion of the secretion which is produced in their large labial glands. This secretion anchors their filter-feeding position, any locomotive activity, and the pupal cocoon as well. The secretion works as a biological adhesive which adheres to nearly any substrate surface — even to wood or the integument of other aquatic animals. We began analysing the proteinaceaous compounds of the labial gland secretions of Simulium ornatum (complex) Meigen. According to the SDS-PAGE and amino acid analyses, blackfly gland secretion consists of a variety of proteins ranging from high to low molecular weights. The most prominent proteins form broad bands at about 70, 40 and 20 kDa. These main proteins were present in secretions from young to old larvae as well as in pupal cocoon secretion, but their relative amounts change with larval development. Results of N-terminal sequencing of prominent proteins revealed no obvious homologies to protein sequences deposited in the databases up to now.     

Determination of the miscibility gap on the solid solution series paragonite-margarite by means of the infrared spectroscopy

In order to study the miscibility gap of the solid solution series margarite-paragonite oxide mixtures corresponding to intermediate compositions were crystallized at H₂O-pressures between 1 and 6 kb at 400 to 600 °C. Run products were examined by x-ray method and IR-spectroscopy; the latter proved to be the tool which allowed to distinguish between the two phases, the calcic and the sodic mica. A solvus exists in the region between 20 and 50 mole% margarite. Its width is temperature-dependent with a critical temperature above 600 °C.     

Growth and ripening of silica polymers in aqueous solutions

The molecular weights and number densities of polymers formed in neutral solutions of silicicacid, at the low concentrations that are typical of hydrothermal waters, were determined by gel filtration chromatography. The polymers exhibit Ostwald ripening that is characteristic of growth limited by a first order reaction of monomer at the surfaces of growing particles. Three divalent inorganic salts at 0.1 M are more effective at promoting polymer growth than is sodium chloride at the same concentration. The results support a recent theoretical model of the silica polymerization reaction but also identify ways in which the model might be improved.     

Geomorphology and climate interact to control organic carbon stock and age in mountain river valley bottoms

Organic carbon (OC) in valley bottom downed wood and soil that cycles over short to moderate timescales (10¹ to 10⁵ years) represents a large, dynamic, and poorly quantified pool of carbon whose distribution and residence time affects global climate. We sought to quantify this potentially important OC pool at the watershed scale to estimate its magnitude and age, as well as determine the controls on its variability within watersheds. To do this, we compared four disparate mountain river basins to show that mountain river valley bottoms store substantial estimated OC stocks in floodplain soil and downed wood (median OC of MgC/ha, n = 178). Although soil OC is generally young (exhibiting a median radiocarbon fraction modern value of , n = 121), geomorphic processes regulate soil burial and processes that limit microbial respiration, preserving aged OC in especially deep, unconfined, wet, and/or high-elevation floodplain soils. We statistically modeled OC stocks to show that valley bottom morphology and hydrology regulate variability in floodplain soil retention and resulting variability in OC stock and age in floodplain soil throughout river networks. Comparing the distribution of OC stocks between wood and soil, we find that where floodplain soils are present, their OC stocks are generally greater than OC stocks stored in wood. Our results suggest that although mountain rivers may accumulate large OC stocks relatively rapidly, those stocks are highly sensitive to alterations in soil and wood retention, implying that human alterations to either disturb or restore floodplain wood and soil storage may have substantial impacts on OC storage in river corridors. © 2020 John Wiley & Sons, Ltd.