ALBERT

Description: Two thousand and twenty well-characterized coral specimens from 17 localities have been analyzed for Sr. Seventy-three genera and subgenera, mostly hermatypic scleractinians, are represented. For some genera, specimens living in surface reef environments are compared with those from 18.3 m depths on the same reefs. Growth rates for some species have also been measured at these depths at one of the sampling sites. Skeletal strontium for a given genus decreases with increasing water temperature, a relationship which previously eluded detection. Aragonite deposited by corals living on the reef at a depth of 18.3 m contains more strontium than the skeletal aragonite of the same coral genera from shallow-water, surface environments. Quantitative treatment of the data for Acropora, one of the most abundant and widely distributed of the reef-building corals, suggests that the observed strontium variations may reflect variations in the rate of skeletal calcification, rather than direct dependence upon temperature or water depth. There is evidence for ‘species effects’, apparently unrelated to growth rate differences, in that certain coral genera are consistently enriched or depleted in skeletal strontium content relative to other genera living in the same reef environments under identical ambient conditions. Temperature, salinity, water depth, seawater composition, and/or other such parameters may in part determine the levels of trace element concentration in carbonates deposited by corals and other marine invertebrates, but it would appear that these variables more directly affect physiological processes which in turn control skeletal chemistry.

Description: Experiments are described to define further the fatty acid requirements of rainbow trout (Salmo gairdneri). In all cases, feeding semipurified diets containing no polyunsaturated fatty acids resulted in poor growth and feed conversion. Linolenic acid was superior to linoleic in stimulating growth and improving feed conversion. The requirement of linolenic acid (ω3 fatty acids) for rainbow trout is 1% of the diet or approximately 2.7% of the dietary calories. Essential fatty acid deficiency symptoms that were cured or prevented by linolenic acid included fin erosion, heart myopathy, and a shock syndrome. It is concluded that linolenic acid has an essential role in rainbow trout similar to that assigned to linoleic acid in man and higher animals.

Description: Nine semipurified diets containing protein/energy ratios that ranged from 73 to 162 mg protein/kilocalorie were fed to young rainbow trout for 18 weeks. A casein-gelatin (70–30) mixture and herring oil were each fed at three levels in a factorial type of experiment. Each of the casein-gelatin levels (36, 44 and 53%) was fed at each of the fat levels (8, 16 and 24%). Cornstarch was added at the expense of the casein-gelatin mix to adjust dietary protein levels. Caloric intake regulated feed consumption; and except for diets low in both fat and protein, no significant differences in weight gains were noted, although feed and energy conversions were markedly influenced. Higher protein/calorie ratios were positively correlated with liver size, level of liver sugars, percentage body fat, percentage body protein, and negatively correlated with percentage liver lipids, size of gastrointestinal tract and gain/gram ingested protein. These correlations were observed for similar protein/calorie ratios regardless of the dietary levels of protein and lipid.

Description: When determining vertical velocity spectra from temperature time series and the mean vertical temperature gradient, restrictions may arise friom the existence of fine-structre. Phillips (1971) and Garrett and Munk (1971_ have shown that the fine-structure contamination of internal gravity wave spectra can be written as a function of some statistical properties of the internal wave field and the vertical wave number spectrum of the fine-structure. A consistent set of current and temperature data was obtained during an experiment at Site D to study this problem. The wave number spectrum of the vertical temperature fine-structure and the apparent frequently spectrum of internal waves are determined from these data. In contrast to the asasumptions in the above models, our fine-structure data imply a wave number spectrum proportional to (wave number)−3 in the range which is important here. Using the above set of data, a model is suggested to describe the effect of fine-structure on vertical velocity spectra computed with the mean vertical temperature gradient. It indicates a maximum fine-structure contamination of the true frequency spectrum of internal gravity waves in the middle of the internal wave band, with less contamination at low and high frequencies.

Description: Volcanic ash layers, which represent the products of volcanic activity within the ocean basins, are common in sedimentary cores taken near Cobb Seamount and on the actively spreading Gorda and Juan de Fuca Ridges. Petrographic and chemical analyses of the glass shards from these deposits have revealed that they are unaltered and are as chemically representative of local volcanic events as are the glassy margins of fresh pillow basalts recovered from the same areas. The presence of unhydrated glass shards in samples as old as 3.8 my is in direct conflict with published hydration rates of both terrestrial and submarine volcanic glasses. A study of a sequence of ash layers from Cobb Seamount, which spans in time much of the Seamount's history, indicates that the volcanic products from Cobb Seamount have had alkaline affinities and that its eruptions have been becoming progressively enriched in Al2O3. Recent experimental petrological evidence and the data on the chemical compositions of Cobb Seamount and the adjacent Juan de Fuca Ridge magmas are in agreement with the hypothesis that magmas are being generated at progressively greater depths beneath Cobb Seamount as it migrates away from the Juan de Fuca Ridge.

Description: A study is described which attempts to obtain information about the vertical correlation of ocean currents at frequencies higher than inertial. Current velocity and temperature data for sensor separations of 4–12 m were taken with a mooring at ‘Site D’. The coherence and phase spectra for velocity component pairs reveals that motions are rotational at low frequencies. A cut-off frequency exists above which coherence drops to low values. The limiting frequency coincides with the minimum Väisälä frequency of the total water column. These cross-spectral properties support the assumption that the motion in this frequency range is governed by internal wave dynamics. The coherence and phase spectra of temperature pairs indicate that a field of temperature structure is superimposed on the mean field which is weakly correlated to the field of motion.