A proton buffering role for silica in diatoms

For 40 million years, diatoms have dominated the reverse weathering of silica on Earth. These photosynthetic protists take up dissolved silicic acid from the water and precipitate opaline silica to form their cell wall. We show that the biosilica of diatoms is an effective pH buffer, enabling the enzymatic conversion of bicarbonate to CO2, an important step in inorganic carbon acquisition by these organisms. Because diatoms are responsible for one-quarter of global primary production and for a large fraction of the carbon exported to the deep sea, the global cycles of Si and C may be linked mechanistically.     

Oxidation fronts in pelagic sediments: diagenetic formation of metal-rich layers

The periodic deposition of distal turbidites at a site on the Madeira Abyssal Plain causes the development of a nonsteady-state diagenetic system in which an oxidation front migrates downward into the sediment. Data presented here show that iron, manganese, and particulate organic carbon are oxidized at this front by oxidants (molecular oxygen and nitrate) diffusing from above. A numerical model of systems of this type predicts the formation of iron-rich layers under certain nonsteady-state conditions. The layers predicted by the model are closely comparable in thickness and general morphology to iron-rich layers found in certain ocean sediments, the origin of which has been until now unexplained.     

Fecal bacterial beta-glucuronidase: control by diet

The effect of a mixed Western, high meat diet or a nonmeat diet on the intestinal bacterial beta-glucuronidase activity was studied in human volunteers. This enzyme was significantly higher in stools of subjects on a high meat diet as compared to the nonmeat regimen. Thus, intestinal flora of subjects on a high meat diet was more able to hydrolyze glucuronide conjugates than that of individuals on a nonmeat diet. This, in turn, may raise the amount of substances, such as carcinogens, within the colonic lumen.     

Oxygen consumption in pelagic marine sediments

Measurements in the interstitial waters of pelagic red clay and carbonate ooze sediments in the central equatorial Pacific show that the dissolved oxygen content decreases with depth and levels off at nonzero values. The supply of reactive organic carbon introduced by bioturbation limits oxygen consumption at depth in the sediment. These gradients should produce diffusive fluxes across the sediment-water interface that average about 8.8 x 10(-14) mole per square centimeter per second or 0.08 milliliter per square meter per hour.     

Fecal eortisoi changes of captive forest musk deer in non-pregnant period with reference to its indicative role.

于2010年4月底至9月中旬采集了陕西风县圈养林麝的新鲜粪样,运用酶联免疫法（ELISA）测定了林麝非孕期的粪样皮质醇含量,探查林麝的应激生理状态。结果表明：圈养雌性林麝非孕期应激生理状态可以分为4个阶段（幼仔卧巢哺乳期、幼仔出巢哺乳期、幼仔单独饲养期、雌麝进入发情期）,其中,雌麝于产后的幼仔卧巢哺乳期处于较高的应激生理状态（产后第2～4周）,而雌麝与幼麝分离期处于较低的应激生理状态（产后第13～15周）;与此对应,单独饲养且与育幼无关的雄麝仅于饲料更换阶段（5月份）表现出一定的应激生理水平增高。分析得出,非孕期圈养林麝粪样皮质醇水平变化与重要的时间相联系,是导致应激生理状态变化的主导因素。认为圈养林麝非孕期应以雌麝的管护为主,尤其处于较高水平的第1阶段,是育幼雌麝饲喂和管护的敏感时期。     

The rise of the rhizosolenid diatoms

The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 +/- 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics.     

Pelagic sedimentation of aragonite: its geochemical significance

The relative importance of the pelagic flux of aragonite, as compared to calcite, to the deep-sea floor has been evaluated by means of a quantitative x-ray diffraction study of samples collected from sediment traps and from an unusually shallow portion of the open Atlantic Ocean (the Rio Grande Rise). The results suggest that the aragonite flux constitutes at least 12 percent of the total flux of calcium carbonate on a worldwide basis. The presence of high-magnesium calcite in several samples suggests that some of the calcareous material falling to the deep-sea floor may be derived from the long-distance transport of debris from shallow-water beenthic organisms as well as from the settling of planktonic remains. This observation supports the contention that 12 percent represents a minimum value. Aragonite and high-magnesium calcite transported laterally from shallow-water regions, upon dissolution during settling into deeper water, may contribute to the neutralization of excess anthropogenic carbon dioxide added to the oceans.     

Abandoned larvacean houses: a unique food source in the pelagic environment

Observations made by using conventional scuba techniques reveal that abandoned larvacean houses serve as food sources for marine, planktonic copepods. Techniques have been developed for photographing these houses in the field for the first time. The abundance of larvacean houses in the open ocean indicates that they are important in pelagic food webs and as a source of particulate organic matter.     

Marine snow: microplankton habitat and source of small-scale patchiness in pelagic populations

In near-surface waters of the neritic zone, the fragile aggregate material called "marine snow" is enriched by a variety of planktonic organisms and detrital products of plankton. Here marine snow is a source of patchiness and taxonomic diversity for microplankton populations and is a likely food resource and recycling agent for fecal particles.     

Fecal free: Biology and authority in industrialized Midwestern pork production

Ethnographically, “fecal free” is a lexical marker that invokes a form of industrialized swine husbandry used in large-scale confinement hog production. Using participant observation and interview research with Illinois contract hog producers, I explore the basis of this husbandry in the biological fragility of confinement hogs. Rather than biology being a simplistic “state of nature,” as it was in early neo-Marxist and populist studies of the 1970s, the frailty of confinement hogs suggests that industrial hog biology is a socially constructed state that justifies the use of contract-based hog production units and their coordination with animal processors. The frailty of confinement hogs results from their genetic characteristics, from the conditions in which they are raised, and from a production rationality that equates animal health with production efficiency. I detail the multiple-site methods, confinement technologies, and contract-based production organization required to raise biologically fragile hogs. And I link hog biology directly to the unequal contract-based relations between actors in industrial pork networks. My study emphasizes the relevance of ethnographic analyses within a political economy of agriculture by describing specific relations of inequalities in local and regional production units and distribution networks that form the building blocks of larger global agro-food systems.

Depth habitats of growth stages of pelagic foraminifera

Oxygen isotopic analysis of different size groups of shells of pelagic foraminiferal species shows that some species deposit their shells at constant depths while others deposit them at increasing or decreasing depths. These patterns show regional variations. Globigerinoides rubra and Globigerinoides sacculifera remain the most convenient species for oxygen isotopic determination of the past surface temperatures of the ocean.     

Digital model of evaporite sedimentation

A deterministic digital model to simulate evaporite sedimentation permits experimentation with depth of water, shape of salt basin, number, position, and strength of the inlets, and rate of evaporation. It provides a reasonable fit to salt thickness and distribution in the Upper Silurian Salina Formation of Michigan.     

Mississippi deltaic wetland survival: sedimentation versus coastal submergence

Seasonal sedimentation, measured with the aid of artificial marker horizons, was markedly different in deteriorating as compared with stable marshes in the Mississippi River deltaic plain. Deteriorating marshes receive most sediment during storm events, whereas stable marshes receive substantial amounts of sediments during the spring river flood. The deteriorating marshes are accreting at a faster rate (1.5 centimeters per year at streamside, 0.9 centimeter per year at inland areas) than the stable marshes (1.3 centimeters per year at streamside, 0.6 centimeter per year at inland areas). However, relative to local apparent sea-level rise as measured by tide gauges in each area, the deteriorating marshes are not maintaining their intertidal elevation as well as the stable marshes. These results indicate the importance of considering accretion relative to submergence.     

Estimates of cenozoic oceanic sedimentation rates

Estimation of average Cenozoic sedimentation rates for the Atlantic, Indian, and Pacific oceans indicates global synchronous fluctuations. Paleocene-early Eocene and late Eocene-early Miocene rates are only a fraction of middle Eocene and middle Miocene-Recent rates. These changes must reflect significantly different modes of continental weathering, which may be due to alternate states of atmospheric circulation marked by reduction of global precipitation.     

Copepod fecal pellets as a source of dihydrophytol in marine sediments

Dihydrophytol(3,7,11,15-tetramethylhexadecanol) was identified in the nonsaponified lipid fraction of fecal pellets from the copepod Calanus helgolandicus fed in the laboratory on a unialgal diet. Direct deposition in the fecal pellets of certain zooplankton species may explain the presence of dihydrophytol in marine sediments. Microbial reduction of phytol in sediment cores does not account for the origin of this compound in all sedimentary environments.