University of New Hampshire

About: University of New Hampshire is a education organization based out in Durham, New Hampshire, United States. It is known for research contribution in the topics: Population & Solar wind. The organization has 9379 authors who have published 24025 publications receiving 1020112 citations. The organization is also known as: UNH.

Copepod hatching success in marine ecosystems with high diatom concentrations

Abstract: Diatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching. These findings challenge the classical view of marine food-web energy flow from diatoms to fish by means of copepods. Egg mortality is an important factor in copepod population dynamics, thus, if diatoms have a deleterious in situ effect, paradoxically, high diatom abundance could limit secondary production. Therefore, the current understanding of energy transfer from primary production to fisheries in some of the most productive and economically important marine ecosystems may be seriously flawed. Here we present in situ estimates of copepod egg hatching success from twelve globally distributed areas, where diatoms dominate the phytoplankton assemblage. We did not observe a negative relationship between copepod egg hatching success and either diatom biomass or dominance in the microplankton in any of these regions. The classical model for diatom-dominated system remains valid.

Role of Metal-Organic complexation in metal sorption by Soils

Abstract: Publisher Summary This chapter focuses on the nature of interaction among trace metals in soil solution, dissolved organics in soil solution, and solid surfaces. The interaction between metal cations and dissolved polyfunctional organic compounds of low molecular weight is important because of its role in mineral-weathering and soil-forming processes and its potential role in heavy metal contamination of soil and groundwater. The chapter presents the organics and metals in the soil solution. Dissolved organics that interact with soil constituents and trace metal ions are of two major kinds: a range of low-molecular-weight organic acids—including polyphenols, simple aliphatic acids, amino acids, sugar acids, and hydroxamate siderophores; and a series of soluble humic/fulvic acids. Numerous environmental issues arise in relation to the interaction of metal ions with soluble organics. Some of these include the phytoavailability of metals, plant nutrient availability, toxicological effects of coordinated metal ions on aquatic and marine organisms, and transport of contaminants, particularly in relation to implications for surface and groundwater quality and soil genesis. All of these issues are highly dependent on the nature and concentration of the contaminant in the soil solution phase. Extant research indicates that low-molecular-weight ligands in soil solution may either enhance or retard reactions with solid surfaces—depending on the functional groups on the organic molecule, soil surface properties, and soil solution conditions. It is imperative that increased research efforts be devoted to evaluating the effects of these organics on metal reactions in the soil.

Cone Opsin Genes of African Cichlid Fishes: Tuning Spectral Sensitivity by Differential Gene Expression

Abstract: Spectral tuning of visual pigments is typically accomplished through changes in opsin amino acid sequence. Within a given opsin class, changes at a few key sites control wavelength specificity. To investigate known differences in the visual pigment spectral sensitivity of the Lake Malawi cichlids, Metriaclima zebra (368, 488, and 533 nm) and Dimidiochromis compressiceps (447, 536, and 569 nm), we sequenced cone opsin genes from these species as well as Labeotropheus fuelleborni and Oreochromis niloticus. These cichlids have five distinct classes of cone opsin genes, including two unique SWS-2 genes. Comparisons of the inferred amino acid sequences from the five cone opsin genes of M. zebra, D. compressiceps, and L. fuelleborni show the sequences to be nearly identical. Therefore, evolution of key opsin sites cannot explain the differences in visual pigment sensitivities. Real-time PCR demonstrates that different cichlid species express different subsets of the available cone opsin genes. Metriaclima zebra and L. fuelleborni express a complement of genes which give them UV-shifted visual pigments, while D. compressiceps expresses a different set to produce a red-shifted visual system. Thus, variations in cichlid spectral sensitivity have arisen through evolution of gene regulation, rather than through changes in opsin amino acid sequence.

Kinetics of Arsenate Reduction by Dissolved Sulfide

Abstract: Arsenic toxicity and mobility in soil and aquatic environments depends on its speciation, with reducing environments generally leading to more hazardous conditions with respect to this element. Aqueous sulfide (H2S or HS-) is a strong reductant and often occurs at appreciable concentrations in reduced systems. Consequently, it may play an integral part in arsenic redox chemistry. Therefore, reactions between arsenic and sulfide may strongly influence water quality in arsenic-contaminated systems. To evaluate this possibility, we investigated the kinetics and reaction pathways of arsenate with sulfide. Arsenate reduction by hydrogen sulfide is rapid and conforms to a second-order kinetic model, having a rate constant, k = 3.2 × 102 M-1 h-1, that is more than 300 times greater at pH 4 than at pH 7. However, arsenite is not the direct reaction product. Rather, arsenic−sulfide complexes develop, including the formation of a trimeric species (HxAs3S6x-3), that persist in solution for several days, ultimately d...

A new look at an ancient order: generic revision of the bangiales (rhodophyta)1

Abstract: The red algal order Bangiales has been revised as a result of detailed regional studies and the development of expert local knowledge of Bangiales floras, followed by collaborative global analyses based on wide taxon sampling and molecular analyses. Combined analyses of the nuclear SSU rRNA gene and the plastid RUBISCO LSU (rbcL) gene for 157 Bangiales taxa have been conducted. Fifteen genera of Bangiales, seven filamentous and eight foliose, are recognized. This classification includes five newly described and two resurrected genera. This revision constitutes a major change in understanding relationships and evolution in this order. The genus Porphyra is now restricted to five described species and a number of undescribed species. Other foliose taxa previously placed in Porphyra are now recognized to belong to the genera Boreophyllum gen. nov., Clymene gen. nov., Fuscifolium gen. nov., Lysithea gen. nov., Miuraea gen. nov., Pyropia, and Wildemania. Four of the seven filamentous genera recognized in our analyses already have generic names (Bangia, Dione, Minerva, and Pseudobangia), and are all currently monotypic. The unnamed filamentous genera are clearly composed of multiple species, and few of these species have names. Further research is required: the genus to which the marine taxon Bangia fuscopurpurea belongs is not known, and there are also a large number of species previously described as Porphyra for which nuclear SSU ribosomal RNA (nrSSU) or rbcL sequence data should be obtained so that they can be assigned to the appropriate genus.