An analytical theory is presented to describe the combined motion of waves and currents in the vicinity of a rough bottom and the associated boundary shear stress. Characteristic shear velocities are defined for the respective wave and current boundary layer regions by using a combined wave‐current friction factor, and turbulent closure is accomplished by employing a time invariant turbulent eddy viscosity model which increases linearly with height above the seabed. The resulting linearized governing equations are solved for the wave and current kinematics both inside and outside the wave boundary layer region. For the current velocity profile above the wave boundary layer, the concept of an apparent bottom roughness is introduced, which depends on the physical bottom roughness as well as the wave characteristics. The net result is that the current above the wave boundary layer feels a larger resistance due to the presence of the wave. The wave‐current friction factor and the apparent roughness are found as a function of the velocity of the current relative to the wave orbital velocity, the relative bottom roughness, and the angle between the currents and the waves. In the limiting case of a pure wave motion the predictions of the velocity profile and wave friction factor from the theory have been shown to give good agreement with experimental results. The reasonable nature of the concept of the apparent bottom roughness is demonstrated by comparison with field observations of very large bottom roughnesses by previous investigators. The implications of the behavior predicted by the model on sediment transport and shelf circulation models are discussed.

In accordance with Recommendation 30b of the International Code of Nomenclature of Bacteria, which calls for the development of minimal standards for describing new species, we propose minimal standards for description of new taxa in the order Hulobucteriules. The minimal standards include information on the following characteristics: cell morphology; motility; pigmentation; the requirement for salt to prevent cell lysis; optimum NaCl and MgCl, concentrations for growth and range of salt concentrations enabling growth; temperature and pH ranges for growth; anaerobic growth in the presence of nitrate or arginine; acid production from a range of carbohydrates; ability to grow on single carbon sources; catalase and oxidase tests; hydrolysis of starch, casein, and Tween 80; sensitivity to different antibiotics; and polar lipids. The placement of a new taxon should be consistent with phylogeny, which is usually based on 16s rRNA nucleotide sequence information, and with DNA-DNA hybridization data in the case of descriptions of new species. This proposal has been endorsed by the members of the Subcommittee on the Taxonomy of Hulobucteriuceue of the International Committee on Systematic Bacteriology.In accordance with Recommendation 30b of the International Code of Nomenclature of Bacteria (21), which calls for the development of minimal standards for describing new species, we propose minimal standards for descriptions of new taxa of aerobic halophilic archaea (order Halobacteriales).General principles. The purpose of this article is to provide microbiologists involved in the taxonomy of the aerobic halophilic archaea (order Halobacteriales, family Halobacteriaceae; also called halobacteria below) a framework for studying them. Adherence to the suggested minimum standards below should help stabilize the taxonomy of the Halobacteriales. With the consent and support of the Subcommittee on the Taxonomy of Halobacteriaceae we have adopted a polyphasic view of halophile taxonomy as suggested by Murray et al. (26). We recommend that all future taxonomic publications on the Halobacteriales should contain data on phenetic, chemical, and molecular properties. We thus recognize that modern natural classification requires as complete a data set as possible, including phenotypic and genotypic information. Table 1 provides a list of the presently recognized genera and species in the Halobacteriales. The current classification is based on the following three kinds of data: (i) phenotypic data, such as cell morphology, growth properties, etc. (34); (ii) chemical data, especially the patterns of polar lipids present in the membranes (34, 36) (differences in polar lipid patterns have been particularly important at the genus level); and (iii) 16s rRNA sequence information and DNA-DNA hybridization data. During the last few years a fairly complete database of 16s rRNA sequences of the type strains of the species in the Halobacteriales has become available and has enabled the con-*

A model to predict the roughness in unsteady oscillatory flows over movable, noncohesive beds is presented. The roughness over movable beds is shown to be a function of the boundary shear stress, rather than a fixed geometrical scale as is the case for fully rough turbulent boundary shear flows over immobile beds. The model partitions the roughness into two distinct contributions. These two contributions are due to the form drag around individual bed forms and to the near-bed sediment transport. The form drag over the bed forms is treated explicitly as a function of the boundary geometry and shear stress. The ripples are predicted as a function of the local skin friction, and a semiempirical expression is derived using standard law-of-the-wall arguments, which gives the ripple or form roughness as a function of the boundary geometry. The ripple roughness is found to be proportional to the product of the ripple steepness and height. Favorable comparison of the form drag model with the results of Bagnold's (1946) fixed ripple study is found. The value of Zo associated with intense sediment transport in oscillatory flow over a flat bed is determined from Carstens et al.' s (1969) experiments. This value is found to be 7 or 8 grain diameters. An expression is derived for the roughness associated with the maximum thickness of a near-bottom sediment-transporting layer consistent with Owen's (1964) roughness hypothesis for saltation of uniform grains in air. At large values of the boundary shear stress relative to the critical value for initial sediment motion, the derived expression is similar to the results of Smith and McLean's (1977) unidirectional flow approach modified for oscillatory flow. The total roughness model is found to compare favorably with Carstens et al.'s (1969) data. In contrast to Smith and McLean's (1977) steady flow findings, the results here show that when ripples are present, they account for a significant portion of the boundary roughness. Recent field measurements, such as those of Smith and McLean [1977] and Dyer [1980], made in turbulent shear flows over bottoms of sand, silt, or mud, indicate that fixed bed roughness models do not always explain the observed roughness magnitudes. The discrepancy between fixed bed models and field observations can be explained by movable bed effects. It is well established that where sediment transport occurs, bed forms develop and are modified in response to the boundary shear flow. Owen [1964] hypothesized for aeolian flows above a layer of saltating sediment that the flow sees the layer as a solid wall roughness and that this roughness is comparable to the depth of the saltation layer. Smith and McLean [1977] adopted Owen's [1964] hypothesis to explain the hydrodynamic roughness over a sand bottom in the Columbia River. They developed an expression for the roughness consisting of two contributions: the Nikuradse sand grain roughness and the roughness associated with the thickness of the bed load layer. The roughness is a function of the boundary shear str...

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Two major types of environment provide habitats for the most xerophilic organisms known: foods preserved by some form of dehydration or enhanced sugar levels, and hypersaline sites where water availability is limited by a high concentration of salts (usually NaCl). These environments are essentially microbial habitats, with high-sugar foods being dominated by xerophilic (sometimes called osmophilic) filamentous fungi and yeasts, some of which are capable of growth at a water activity (a w ) of 0.61, the lowest a w value for growth recorded to date. By contrast, high-salt environments are almost exclusively populated by prokaryotes, notably the haloarchaea, capable of growing in saturated NaCl (a w 0.75). Different strategies are employed for combating the osmotic stress imposed by high levels of solutes in the environment. Eukaryotes and most prokaryotes synthesize or accumulate organic so-called 'compatible solutes' (osmolytes) that have counterbalancing osmotic potential. A restricted range of bacteria and the haloarchaea counterbalance osmotic stress imposed by NaCl by accumulating equivalent amounts of KCl. Haloarchaea become entrapped and survive for long periods inside halite (NaCl) crystals. They are also found in ancient subterranean halite (NaCl) deposits, leading to speculation about survival over geological time periods.