Experiments with Zooplankton on Coral Reefs,or, Will the Real Demersal Plankton Please Come Up?

Abstract. Zooplankton was sampled with emergence traps on a Thalassia bed behind an insular reef at San Salvador. Bahamas. These traps tested the effect of sealing the trap to the substrate or allowing it to rest unsealed on the substrate. Total numbers of plankters collected did not differ between the two types of trap, but significantly more cyclopoid copepods were collected in unsealed traps and significantly more tanaids were found in sealed traps. Total densities in unsealed traps were inflated as much as 24–28 % by contamination with holoplankton. Both trap designs, but particularly the sealed traps, collected animals that apparently crawled up the insides. A substantial number of animals, as many as 9–31% of those collected in sealed traps, may not be actually planktonic. Our results suggest that reefs produce fewer meroplankters per unit of substrate, and thus meroplankters contribute less to reef foodwebs than formerly thought.     

Transport of molybdenum in mountainous streams,Colorado

Waters and sediments in some streams in Colorado contain elevated concentrations of Mo derived from mining areas upstream. In the streams studied, most of the Mo was transported in dissolved form. The suspended load carried a significant amount of Mo (up to 19%) only near the molybdenum mill at Climax.     

Evolution of the sverdrup basin, arctic canada

Sverdrup Basin underwent three periods of sudden and pronounced increases in rates of subsidence, beginning about 330, 225 and 124 m.y. ago. Subsidence curves indicate that initial high rates of subsidence (up to 11 cm/1000 year) decreased steadily for up to 100 m.y. until interrupted by the next sudden return to rapid subsidence. When the center of the basin was rapidly subsiding, areas adjacent to the basin were midly uplifting. The uplifted region expanded inward over a period 10–30 m.y. to include basin marginal zones thereby tending to shrink the area of active subsidence. Most of the observed record of basin subsidence (at least 70%) probably resulted from lithospheric response to loading of an initial depression. For most of basin history, deduced subsidence and peripheral uplift relations, together with the pattern of exponential decay constants determined from subsidence curves, are consistent with the loading response of a lithosphere modelled as a viscoelastic beam.     

Correction to: Multilevel Graph Partitioning for Three-Dimensional Discrete Fracture Network Flow Simulations

Mathematical Geosciences - The publication of this article unfortunately contained a mistake. The assignment to the affiliations of author Satish Karra was not correct     

Getting to the Bottom of It: Tools,Techniques, and Discoveries of Deep Ocean Geography

The initial impetus for developing a specialty in ocean geography resulted from the need to resolve applied problems in coastal resources, as opposed to development of oceanographic research methods and concepts. However, the development in the last 10 to 20 years of sophisticated technologies for ocean data collection and management holds tremendous potential for mapping and interpreting the ocean environment in unprecedented detail. With the understanding that ocean research is often very costly, yet deemed extremely important by large funding agencies, geographers now have the opportunity to perform coastal and marine studies that are more quantitative in nature, to formulate and test basic hypotheses about the marine environment, and to collaborate with geographers working in corollary subdisciplines (e.g., remote sensing, GIS, geomorphology, political geography as pertaining to the Law of the Sea, etc.), as well as with classically-trained oceanographers. This article reviews, for the non-specialist, the newest advances in mapping and management technologies for undersea geographic research (particularly on the ocean floor) and discusses the contributions that geographers stand to make to a greater understanding of the oceans.     

Dimensionless and unbiased CPT interpretation in sand

The cone penetration test (CPT) is widely used, and although initially developed as a stratigraphic logging tool its excellent repeatability and accuracy offers a benchmark quantitative test for sand in particular. A continuing difficulty, however, is that the CPT does not measure any soil property directly, so that parameters of interest must be recovered from solution of an inverse boundary value problem, which is difficult. To date most CPT interpretations in sand have been based on very limited calibration testing carried out in large chambers on a few sands from which mappings are developed. But there are differences in the CPT response from one sand to another leaving the interpretation imprecise (and arguably even speculative) because these differences remain poorly understood. In this paper we use the familiar spherical cavity expansion analogy to the CPT including large strains and a good, critical-state-based, soil model to develop a pattern of behaviour which we then compare to some of the reference chamber test data. We find that one of the issues of dispute in the empirical interpretation methods, the so-called stress-level effect, is caused by neglect of elasticity and that there are several additional parameters of first-order significance to cavity expansion in sands. More generally, we show that the difference in CPT response between various chamber sands in predicted. Our results are cast in dimensionless form and the inversion illustrates that extreme care is required in interpreting CPT data if the in situ sand state is to be determined with precision approaching that suggested as achievable by the repeatability of the CPT data itself. Aspects requiring particular care in interpreting CPT data in sand are discussed. © 1998 John Wiley & Sons, Ltd.     

Rock control on microweathering of bedrock surfaces in a periglacial environment

Microweathering of ice-smoothed bedrock surfaces was investigated in the Røldal area of Hardanger Plateau (60°), southern Norway. Postglacial rates of weathering were determined from surface lowering using quartz veins as reference surfaces. Weathering processes are inferred from assessment of weathering rind formation, surface hardness, and the preservation of small-scale glacial erosional features.Surface lowering rates for a range of metamorphic rocks vary from 0.05 to 2.20 mm ka^− 1 and are broadly comparable with those obtained from crystalline rocks in other periglacial environments. The mean rate of surface lowering at 0.55 mm ka^− 1 is low and demonstrates the relatively small impact of microweathering on postglacial landscape evolution. Variations in bedrock microweathering can be explained by lithological variation. Amphibolite and mica-rich bedrock surfaces experience greater denudation and weakening, least weathering rind formation, and abundant preservation of glacial striae, despite greater surface lowering. Conversely, quartz-rich bedrock surfaces are most resistant to denudation and weakening, but have greater weathering rind formation and fewer preserved striae. Postglacial microweathering is achieved primarily through granular disintegration involving detachment and removal of mineral grains and weakening from increased porosity. Granular decomposition is manifest in the formation of weathering rinds. Analysis of interactions between weathering indices indicates that rind accumulation is limited by microerosion.A conceptual model is proposed that illustrates the temporal interrelationships between in situ and erosional facets of microweathering in two contrasting mineral assemblages. The model proposes that cyclic processes of in situ disintegration, decomposition, and erosion are at work. The relative balance between these processes varies with lithology so that in more resistant quartz-rich rocks the net effect is minimal surface lowering and accumulation of weathering rind. In weaker, amphibolitic and micaceous rocks, the net effect is greater surface lowering and minimal accumulation of weathering rind. The results of the research demonstrate the important influence of rock properties, notably mineral composition, in postglacial microweathering of crystalline bedrock in a periglacial environment.