ALBERT

Description: We evaluated the effects of self-selected diets on calcium absorption and calculated retention in girls during pre-, early, and late puberty. Dietary calcium absorption was measured in 51 girls aged 4.9–16.7 y by using a dual-tracer stable-isotope technique. We found that calcium intake was similar among girls of all ages and all degrees of pubertal development and was below the recommended dietary allowance (1200 mg/d) for 21 of 25 girls aged ≥ 11 y. The early pubertal period was associated with a higher percent of dietary calcium absorption (34.4 ± 11.9%) than was the prepubertal (27.7 ± 8.2%) or late pubertal periods (25.9 ± 7.8%). Calculated calcium retention averaged 132 ± 83 mg/d in prepubertal girls, 161 ±88 mg/d in early pubertal girls, and 44 ± 91 mg/d in late pubertal girls. Peak calcium retention during early puberty was far below that previously reported after higher calcium intakes. We conclude that peak periods for calcium retention for girls are in the pre- and early pubertal periods. The current calcium intake of American girls during the pubertal growth period may not enable maximal mineral retention; therefore, increased calcium intakes should be considered.

Description: in a recent publication von Brandt (1) gives a survey of all determinations of the calcium content of Baltic water hitherto published. He records in all 39 analyses made during the last century, which give us an idea of the order of magnitude of the calcium concentration; they cannot, however, serve for comparative purposes as in many cases chlorine determinations on the same water samples are lacking. Neither have we any clue for judging the accuracy of these analyses, the latest of which date from 1884. Fifty years later, in 1935, Za rin s and O z o 1 ins (8) published an extensive investi­gation of the water in the Bay of Riga and in the Baltic off the Latvian coast, their most westerly station nearly coinciding with the Finnish station F81 (Lat. 57° 22'N., Long. 19°57'E.) above the central depression of the Baltic. Their material comprised about 70 calcium analyses on water from all depths. Finally v o n B r a n d t in the above-mentioned paper publishes nearly 300 analyses of surface water collected in 1935 and 1936 during several voyages from Pillau to Helsingfors and back, and along the German coast as far as Kiel and back. The present material comprises analyses of only 48 samples of surface and bottom water collected during the summer cruise, in July 1935, of the s.s. "Nautilus" from the Gulf of Finland, the Gulf of Bothnia, and the northern half of the Baltic proper. In spite of the smaller number of samples this material is more comprehensive than the two preceding investigations in so far as it covers a greater area of the sea. I t was originally meant as a survey of the calcium content in these parts of the Baltic, but the surprisingly simple relationships between calcium content and chlorinity which it revealed, give the results far more scope than was expected.

Description: Seafloor topography is neither spatially homogeneous, nor does it obey Gaussian statistics; deviations from both of these assumptions are important from a geological and acoustic point of view. It has been found that the distribution of topographic slopes can be used as a primary tool for understanding the sources and extent of spatial heterogeneities and patterns on the seafloor. The covariance function has been widely used to characterize seafloor topography, but requires the assumption of Gaussian joint probability statistics to be valid. For heterogeneous topography characterized by large transient signals such as steep scarps and volcanoes, the covariance becomes dominated by the transients; in contrast the family slope distributions can still be used to derive stable descriptors for regions with large transient signals, as well as regions containing asymmetric features, and regions with only limited sampling. Knowledge of slopes is useful because a direct relation exists between the covariance and the slope distributions at different spatial scales. Studies of the slope distribution provide a means of identifying the presence of the non‐Gaussian elements in the topography, and flagging their spatial locations. The methods used here are demonstrated by applying them to three small patches of topography located within 20 km of each other in the Eastern Pacific. It is found that dominant azimuthal directions and dip angles differ widely between the patches. In addition, asymmetries in the cross‐sectional shapes of faulted abyssal hills are documented. [Work supported by ONR.]

Description: High‐frequency bottom acoustic and geoacoustic data from three well‐characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.

Description: Pelagic aquatic environments differ from terrestrial environments in being three-dimensional and relatively homogeneous, rather than two-dimensional and heterogeneous. The present paper examines the causes and consequences of these differences in the context of their influence on the interactions of animals with environmental light. Particular emphasis is placed on light as a determinant of effective modes of crypsis in the two different habitats. The terrestrial world has selected for the expression of crypticity in the form of superficial color patterns. The heterogeneity of this habitat has resulted in evolutionary divergence of these superficial color patterns, often in very closely-related animals. In contrast, in the homogeneous pelagic aquatic habitats, evolutionary convergence on three main forms of crypsis is evident: (1) transparency; (2) reflection of most, if not all visible wavelengths; and, (3) ventral bioluminescence as counterillumination; thus, to be cryptic most animals in these habitats use one or a combination of these modalities to variously transmit, reflect or mimic environmental light. In the present paper, special attention is given to transparency as the most prevalent, yet least understood, of these mechanisms that are used in predator-prey interactions.

Description: Work on the life histories of common antarctic benthic marine invertebrates over the past several decades demands a revision of several widely held paradigms. First, contrary to expectations derived from work on temperate species, there is little or no evidence for temperature adaptation with respect to reproduction (gametogenesis), devel? opment, and growth. It remains to be determined whether the slow rates of these processes reflect some inherent inability to adapt to low temperatures, or are a response to features of the antarctic marine environment not directly related to low temperature, such as low food resources. Secondly, contrary to the widely accepted opinion designated as "Thor- son's rule," pelagic development is common in many groups of shallow-water marine invertebrates. In fact in some groups, such as asteroids, pelagic development is as prevalent in McMurdo Sound, the southern-most open-water marine environment in the world, as in central California. In other taxonomic groups, especially gastropods, there does seem to be a genuine trend toward non-pelagic development from tropical to antarctic latitudes. Although this trend has been predicted by theoretical models, its underlying causes appear to be group specific rather than general. Thirdly, pelagic lecithotrophic development, often considered to be of negligible importance, occurs in many shallow-water antarctic marine macroinvertebrates. Pelagic lecithotrophy may be an adaptation to a combination of poor food conditions in antarctic waters most ofthe year and slow rates of development. Nevertheless, some of the most abundant and widespread antarctic marine invertebrates have pelagic planktotrophic larvae that take very long times to complete development to metamorphosis. These species are particularly prevalent in productive regions of shallow water (〈 30 m), which are frequently disturbed by anchor ice formation, and the production of numerous pelagic planktotrophic larvae may represent a strategy for colonization. Although planktotrophic larvae tend to be seasonal in occurrence, their production is not linked particularly closely to the mid-summer pulse of phytoplankton production. These larvae show no evidence of starvation, even during times when phytoplankton abundance is very low, and they may depend on unusual sources of food, such as bacteria. How they escape the selective conditions that apparently led to a predominance of non-feeding modes of development in antarctic marine invertebrates remains as a major challenge for antarctic marine biology.