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Sediment-water Interface (sediment-water + interface)

Distribution by Scientific Domains
Earth and Environmental Science66%

Selected Abstracts

Effect of Campsurus notatus on NH+4, DOC Fluxes, O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment-Water Interface of an Amazonian Lake Impacted by Bauxite Tailings

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003
João José Fonseca Leal
Abstract The aim of this study was to evaluate the influence of Campusurus notatusEaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH4+) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment-water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment-water interface. The cores were incubated with 0 to 2,388 ind m,2 of Campsurus notatus nymphs, and the changes in NH4+, DOC, O2 concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two-way ANOVA, p < 0.05) in bacterial production (0.44 ,g C l,1 h,1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH4+) at the sediment-water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production. [source]

Factors Affecting Sediment Oxygen Demand in Commercial Channel Catfish Ponds

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2004
James A. Steeby
Sediment oxygen demand (SOD) measured in 45 commercial channel catfish ponds in northwest Mississippi using in situ respirometry (N = 167) ranged from 63 to 1,038 mg/m2 per h. Mean SOD in this study (359 mg/m2 per h) was greater than that reported previously for catfish ponds but was similar to SOD in semi-intensive marine shrimp ponds. Nine variables were selected and measured to assess their relative importance in accounting for variation in SOD. Six variables were included in multiple regression models that explained slightly more than half of the variation in SOD. These variables were: dissolved oxygen concentration at the beginning of respirometry incubation:, particulate organic matter concentration in water above the sediment surface: organic carbon concentration at the immediate sediment-water interface (flocculent or F-layer) combined with the upper 2 cm of sediment (S-layer); organic carbon concentration in the mature (M) underlying sediment layer: water temperature: and total depth of accumulated sediment. Sediment oxygen demand was most sensitive to changes in dissolved oxygen concentration in the overlying water, particulate organic matter concentration in the water, and the concentration of organic carbon in the combined flocculent and upper sediment (F+S) layer. Models for SOD in this research predict that the mass of sediment below the upper 2-cm surface layer on average contributes only ,20% of total SOD. Stratification and normal daily fluctuation of dissolved oxygen concentration in eutrophic culture ponds likely limit expression of sediment oxygen demand. Maintaining aerobic conditions at the sediment-water interface will minimize accumulation of organic matter in pond sediment. [source]

Paleoecology of a large Early Cambrian bioturbator

LETHAIA, Issue 3 2000
James W. Hagadorn
The Lower Cambrian Poleta Formation in the White-Inyo Mountains of eastern California contains well-preserved and laterally extensive exposures of the large looping and meandering trace fossil Taphrhelminthopsis nelsoni n.isp. Such traces are typical features on upper bed surfaces of Lower Cambrian shallow marine sandstones and occur with Ediacaran fossils at other localities. Morphologic, sedimentologic and goniogram analyses suggest that the inferred tracemaker was a large soft-bodied echinozoan- or mollusc-grade animal with a volume greater than 14 cm 3 that actively grazed or ingested sediment at the sediment-water interface. Although portions of these traces appear to reflect relatively ,complex' behavior, looping patterns are not periodic as expected for a systematic foraging strategy. T. nelsoni traces are patchy in distribution and commonly associated with suspect-microbial features, suggesting that tracemakers may have been targeting microbial-based or related concentrations of food resources. Such behavioral patterns are typical of shallow late Neoproterozoic-early Cambrian settings, and like suspect-microbial structures are later restricted to deep marine or stressed settings. [source]

A Rare, Larval-founded Colony of the Bryozoan Archimedes from the Carboniferous of Alabama

PALAEONTOLOGY, Issue 5 2001
Frank K. Mckinney
Very few basal attachments of the spiralled fenestrate bryozoan Archimedes are known. A newly discovered specimen is interpreted to have grown on a thin cylindrical ephemeral substratum that extended above the sediment-water interface, allowing paired spirals to develop and to extend in opposite directions when the colony was very small. [source]