Biogeochemistry of tube-dwellings: A study of the sedentary polychaete Amphitrite ornata (Leidy)

Most studies of near interface sediments assume that chemically and biologicalJy important properties are stratified vertically in a deposit. Sampling patterns reflect this assumption and little attention has been paid to three-dimensional heterogeneity. In this study the effects of burrow structures formed by Amphitrite ornata on the distribution of physical, chemical, and biological characteristics of a deposit are investigated...

Effects of the marine deposit-feeders Heteromastus filiformis (Polychaeta), Macoma balthica (Bivalvia), and Tellina texana (Bivalvia) on averaged sedimentary solute transport, reaction rates, and microbial distributions

Experimental studies of the deposit-feeders Heteromastus flliformis, Tellina texana, and Macoma balthica demonstrate that, at natural population abundances, each species has major effects on sediment overlying water solute transport, bulk sediment reaction rates, and microbial distributions. Using Cl− as a conservative tracer, one-dimensional transport models show that the effective diffusion coefficient, De, in the presence of these macrofauna is ∼2–5× the molecular diffusion value in the upper 8–12 cm of sediment. In general, the exact value of De is time dependent as shown by time-course experiments with Heteromastus and by comparison of one-dimensional model predictions with a transient-state, two-dimensional cylindrical coordinate model. This latter model takes into account changes in diffusion geometry caused by irrigated burrow structures. The magnitude of apparent time variation in De depends on burrow abundance, size, and depth of burrowing; larger values of De are measured at longer times of tracer transport. In contrast, the simple nonlocal parameter required to mimic the two-dimensional model distributions is essentially constant with time and can be related to different solutes by the ratio of their diffusion coefficients.Models of pore water distributions demonstrate that the production rates of NH4+ in sediments are increased by at least 20–30% in the presence of macrofauna compared to controls or anoxic incubations, regardless of the model used. This is presumably due to the overall lowering of inhibitory metabolite concentrations as well as stimulation of bacteria during grazing. Total bacterial numbers increase at depth in the presence of Heteromastus and Tellina relative to controls but are depleted in fecal material. A substantial increase in ATP/bacteria ratios occurs in fecal and surface sediment, presumably indicative of active growth and conversion from anaerobic to aerobic metabolism. Apparent elevated numbers and stimulation of metabolic activity is consistent with a microbial gardening effect by macrofauna.Most of the NH4+ produced in experimental sediment was apparently oxidized at the sediment-water interface and, along with the oxidation of sulfide and metals, results in a major surficial zone of low pH and HC03− consumption at a rate \u3e24 meq/m2/d. This should cause substantial dissolution of CaCO3 as shown in previous studies. A zone of elevated Si(OH)4 production is also associated with the redoxcline, but Si(OH)4 is otherwise produced at a sufficiently slow rate that detectable decreases in concentration occur in irrigated sediments. Although no measurable effects of infauna on Si(OH)4 reaction constants could be demonstrated from pore water profiles, lowered concentrations result in higher net production rates, and sediment-water fluxes of Si(OH)4 increased in the presence of macrofauna by ∼1.4–1.6×, in agreement with theoretical models. Despite their limitations, the transport-reaction models and the two-dimensional or nonlocal parameterization models in particular, provide a consistent basis for description of the effects of macroinfauna on bulk sediment properties, and allow for comparison of different species at similar population abundances

Geologic Mapping of the Marius Quadrangle, the Moon

The authors seek to construct a 1:2,500,000-scale map of Lunar Quadrangle 10 (LQ10 or the Marius Quadrangle) to address outstanding questions about the Moon's volcanologic history and the role of impact basins in lunar geologic evolution. The selected quadrangle contains Aristarchus plateau and the Marius hills, Reiner Gamma, and Hevelius crater. By generating a geologic map of this region, we can constrain the temporal (and possibly genetic) relations between these features, revealing more information about the Moon's chemical and thermal evolution. Although many of these individual sites have been investigated using Lunar Orbiter, Clementine, Lunar Prospector and Galileo data, no single investigation has yet attempted to constrain the stratigraphic and geologic relationships between these features. Furthermore, we will be able to compare our unit boundaries on the eastern boundary of the proposed map area with those already mapped in the Copernicus Quadrangle. Geologic mapping of the Marius Quadrangle would provide insight to the following questions: the origin, evolution, and distribution of mare volcanism; the timing and effects of the major basin-forming impacts on lunar crustal stratigraphy; and, the Moon's important resources, where they are concentrated, and how they can be accessed

The effect of mangrove development on coral reef fish in Bocas del Toro, Panama and global mangrove management methods

Mangroves provide a variety of ecosystem services to humans, such as timber for construction and a place for tourists to visit. They are also important nursery habitats for juvenile fish that migrate to nearby coral reefs, providing humans fish for food and recreation. In this study, 50-meter transects were conducted in Bocas del Toro, Panama, on coral reefs near coastlines under three categories: (1) with intact mangroves, (2) with mangroves interspersed with development, and (3) without mangroves. Transects were used to determine species richness, species diversity, and biomass of reef fish. The results showed a statistically significant difference in species richness, species diversity, and biomass of reef fish on coral reefs near intact and degraded mangroves when compared to coral reefs without mangroves. The results indicate that the development of mangroves in Bocas del Toro at these sites has minimized harm to reef fish because it has not removed many mangroves and has potentially provided an alternative habitat for juvenile fish. Studies need to be conducted on the relationship between the anthropogenic impact on mangroves and reef fish because mangroves face increasing disturbance due to rises in population and tourism. In addition to the sites in Bocas del Toro, this thesis also examines global mangrove management practices, including the role that ecotourism plays in mangrove conservation. It demonstrates that education about mangroves in local communities, combined with bottom-up management and research through multiple academic disciplines, is the most effective way to conserve mangrove habitats for both local and tourism opportunities

Lunar Geologic Mapping: A Preliminary Map of a Portion of the LQ-10 ("Marius") Quadrangle

Since the first lunar mapping program ended in the 1970s, new topographical, multispectral, elemental and albedo imaging datasets have become available (e.g., Clementine, Lunar Prospector, Galileo). Lunar science has also advanced within the intervening time period. A new systematic lunar geologic mapping effort endeavors to build on the success of earlier mapping programs by fully integrating the many disparate datasets using GIS software and bringing to bear the most current understanding of lunar geologic history. As part of this program, we report on a 1:2,500,000-scale preliminary map of a subset of Lunar Quadrangle 10 ("LQ-10" or the "Marius Quadrangle," see Figures 1 and 2), and discuss the first-order science results. By generating a geologic map of this region, we can constrain the stratigraphic and geologic relationships between features, revealing information about the Moon s chemical and thermal evolution

Comparative biogeochemistry of water in intertidal Onuphis (polychaeta) and Upogebia (crustacea) burrows: temporal patterns and causes

The burrows of macrobenthos represent an important class of sedimentary microenvironments which significantly influence chemical, biological, and physical characteristics of a deposit. In intertidal regions, the time-dependent changes in composition during ebb-tide of water contained in burrows is a sensitive indicator of biogenic and abiogenic chemical reactions in burrow walls and adjacent sediment. Comparison of time series water samples taken from Onuphis jenneri (polychaete) and Upogebia affinis (crustacean) burrows in the same tidal flat demonstrate substantial differences in biogeochemical microenvironments despite the spatial proximity of the two species. Both types of burrows are influenced by the same general kinds of biogeochemical reactions but the relative intensity of these reactions differs in each case. Evidence for both heterotrophic and chemoautotrophic metabolic activity in each burrow type comes from the build-up or consumption patterns in burrow water of solutes such as NH4+, NO3−, Mn++, l−, HPO4−, and HCO3−. Burrow irrigation models and the stoichiometry of solute build-up imply that Upogebia burrows are sites of more intense nitrification-denitrification and microbial activity generally than are Onuphis tubes. Upogebia burrow water is also distinctly undersaturated with respect to carbonate minerals and has high numbers of bacteria relative to Onuphis. In addition to reaction rates, burrow geometry and the adsorption-diffusive permeability properties of the burrow wall also affect transient behavior of solutes. The organic burrow lining of Onuphis shows linear adsorption isotherms for positive, negative, and neutrally charged solutes represented by NH4−, HP04−, and Si(OH)4. Diffusion-reaction modeling demonstrates that adsorption, in particular, can significantly lower the transient state concentrations of burrow water trace solutes even for tube wall thicknesses of only 200 μm. The observed differences between burrow microenvironments of the two species living in close proximity suggest distinct biogeochemical associations between microbes and species specific biogenic structures

Volcanogenic Fluvial-lacustrine environments in Iceland and their utility for identifying past habitability on Mars

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.Publisher PDFPeer reviewe

A Characterization of Homeomorphic Bernoulli Trial Measures.

We give conditions which, given two Bernoulli trial measures, determine whether there exists a homeomorphism of Cantor space which sends one measure to the other, answering a question of Oxtoby. We then provide examples, relating these results to the notions of good and refinable measures on Cantor space

Knowledge, attitudes, and practices regarding avian influenza (H5N1), Afghanistan.

From February through April 2007, avian influenza (H5N1) was confirmed in poultry in 4 of 34 Afghan provinces. A survey conducted in 2 affected and 3 unaffected provinces found that greater knowledge about reducing exposure was associated with higher socioeconomic status, residence in affected provinces, and not owning backyard poultry