ALBERT

Description: Benthic foraminifera from surface Sediments of the Ross Sea were studied to determine modern distributions of important assemblages. Factor analysis of the raw data distinguished nine significant factor assemblages which account for 86% of the raw data. These factor assemblages provide a means of understanding modern oceanographic and ecologic conditions because they show the response of this faunal group to different environments. Environmental conditions are in turn controlled by the modern climatic regime of the region. Four benthic assemblages from the relatively shallow (500 to 700 m) eastern Ross Sea Continental shelf are predominantly arenaceous. This may be because the relatively late seasonal breakup of pack ice inhibits productivity in the surface waters and permits a buildup of CO, thus causing the CCD to occur at shallow depths. On the Western part of the Continental shelf, three assemblages are composed primarily of calcareous species even though water depths are often greater there than they are in the east. One of these calcareous assemblages occurs in samples from water depths as great as 755 m in the southwestern part of the region, below the CCD as defined for the Ross Sea by previous workers. We relate this depressed CCD to early seasonal breakup of pack ice in the Western Ross Sea. Within the eastern arenaceous and Western calcareous regions on the Continental shelf, distributions of benthic assemblages are probably related to water depth and other ecologic variables. Two benthic assemblages from the Continental slope north of the Ross Sea also are calcareous. We attribute their distributions to high rates of productivity in the overlying surface waters, where the interface between eastward-flowing Circumpolar Deep Water and Ross Sea water masses is marked by a narrow zone of intense upwelling.

Description: Foraminiferal evidence from the eastern equatorial Pacific and from the North Atlantic indicates that the dissolution of deep-sea carbonates was intensified during interglacials rather than during glacials, in contrast to widespread opinion. Pleistoccne dissolution cycles introduce a systematic bias into the Interpretation of calcareous fossil assemblages near and below the lysocline zone.

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: Morphological characters, interrelations, evolutionary trends, synonymies, Stratigraphie and paleogeographic distribution of 15 species here included in Globigerinatheka are discussed and illustrated by line drawings and SEM mircographs. In order to stress their interrelations, all taxa—with the exception of G. semiinvoluta—are given subspecific rank in a trinomial System. Holotypes and some additional types of the taxa discussed, which originally were published at widely varying magnifications, are reproduced at a uniform scale to facilitate their comparison. By this procedure alone the four species subconglobata, indes, mexicana and semiinvoluta become clearly distinct. The final chamber/bulla problem, of some importance in the genus, is discussed and illustrated. Evidence is given that G. semiinvoluta is a valid species, and not a synonym of G. mexicana mexicana. Its variability is demonstrated by a series of SEM micrographs. One subspecies, G. subconglobata luterbacheri, is described as new.

Description: Three closely related species ( A. beccarii (Linn.), A. batava (Hofker) and A. tepida (Cushman) have been studied. Each possesses a multilaminate “chitinoid” endoskeleton, the outermost lamina possessing imperforate pustulae of shape characteristic for the species. The pustulae are fused to segmented tubules of organically-bound carbonate granules; these tubules line the canaliculi linking the inner and outer perforations of the test wall, and differ only in length between the three species. The calcareous wall is essentially granular in internal morphology, and is built upon an organic framework in which the tubules play a significant part. The apertural structures are described, and it is confirmed that the toothplate is structurally continuous with the septal (“rotalid”) flap and the basal calcareous lamella of the test. The distribution of intrathalamous and extrathalamous cytoplasm in A. tepida is described, and the first sequential photographs of cytoplasmic extrusion are presented for Ammonia. The relationship between the organic skeleton, the calcareous exo- and endo-skeletons, and the cell, is discussed.

Description: Plankton records from three ATLANTIS II cruise tracks near the west African coast reveal a deep penetration of northern forms into tropical waters. They are carried there by the clockwise movement of the North Atlantic Gyre and are found mixed with subtropical and tropical forms. In light of these plankton records, and previous ones from other parts of the Gyre, a view of North Atlantic faunal parcelling is given. The traditional three-fold parcelling (northern, subtropical and tropical) is recognizable. However, gyral circulation tends to generate a rotary pattern of distribution with abundant faunal mixing. The subtropical fauna occupies the core of the Gyre and mixed faunal associations occur around the margins. The northern and tropical faunas contribute to these mixed faunal associations along clockwise dispersal routes.

Description: The strontium, magnesium, and calcium contents of the shells of the planktonic foraminifer Globorotalia truncatulinoides from continental rise sediments were determined by electron microprobe. This species spends the early part of its life cycle in the upper water column where it precipitates the lamellar portion of its shell. It then sinks below the permanent thermocline where it is secondarily calcified with a blocky calcite coating. This change of environments through the organism’s life allows a test of the hypothesis that an individual can change the composition of the carbonate material secreted in response to changes in the temperature of of the water mass in which it lives. All individuals except a juvenile showed decreasing magnesium contents in the outermost portion of their shells, corresponding to decreasing temperature in successively deeper water. The juvenile form showing no secondary calcification was uniform in composition. Because the Mg/Ca ratio in seawater is constant, this differentiation strongly supports the contention that an individual organism, as it precipitates shell material, can regulate its composition in response to environmental changes in temperature. No significant differences in composition were found between left- and right-coiling specimens. The difference between lamellar and blocky calcite was found to be significantly less in a sample from 10 cm below the top of the piston core than those from above or below this level. This difference is produced by a decrease in the magnesium content of the lamellar calcite and may correspond to a surface water temperature 2.5°C lower approximately 1,100 years ago.

Description: The causes of the growth and collapse of the large Pleistocene ice sheets is a topic of intense scientific debate. The amount of new data and ideas has been prodigious during the last ten years. This review concentrates on the shifting patterns of glacial advance and shrinkage during the last Glaciation. We also examine reconstructions of conditions during the maximum of this Glaciation about 18,000 BP, and the mechanisms that might have caused the rapid collapse of many of the world's ice sheets between 18,000 and 8000 BP. Our paper focuses on the North Atlantic sector because it is there that the major Pleistocene ice sheets grew, developed, and retreated.

Description: Planktonic foraminifera were collected from an oceanic front off Baja California, Mexico, during April and May, 1965, in connection with studies of the physical oceanography of the front. Four major water masses were present: Southern Surface Water at approximately 0-50 m, Northern Surface Water, forming a submerged intermediate layer between about 150-50 m, Southern Deep Water below 150 m, and Northern Deep Water deeper than 250 m. Planktonic organisms smaller than 2 mm were concentrated in the surface waters, suggesting that food for foraminifera was most abundant there. Organisms larger than 2 mm, considered a measure of potential predators of foraminifera, were abundant in both surface and intermediate waters. Most foraminiferal concentrations were from 1 to 100 specimens per m :J, with the largest concentrations in Southern Surface Water above the front and in deep water along the front. Lowest concentrations were in intermediate water, except in the frontal mixing zone, and at depths below 450 m. Empty shell concentrations were about one-tenth of associated living concentrations. Possible errors of concentration estimates were assessed by comparing paired net and paired tow results. Seventy percent of these estimates appear to be precise within a factor of 1.3. The error introduced by patchiness probably is much larger. Four foraminiferal assemblages are recognized: ( 1 ) Southern Surface Water assemblage, (2) widespread species with southern affinity which apparently tolerate the intermediate water, ( 3) species brought in with the submerged northern water, and ( 4) the assemblage inhabiting the deep waters. The estimated average minimum flux of empty shells was approximately 6% of the living standing crop I day by volume. The relative empty shell output was greater than this for many intermediate water species, and less for species restricted to southern and to deep water. The intermediate layer contributed approximately one-half of the empty shell flux, where specimens with small terminal chambers (kummerforms) were abundant. The sediment produced in the front contained about 50% kummerforms, but the total standing crop of living foraminifera contained only about 10%. The tongue of advected intermediate water may have represented an unfavorable habitat for foraminifera, where northern species were submerged and possibly deprived of food or otherwise impeded in their normal growth. Southern species also may have been displaced from their normal habitat by mixing processes. These displacements are suggested as one cause for the formation of small terminal chambers in specimens inhabiting intermediate depths. Empty shells apparently arise through reproduction, stress from displacement, and predation, with predation being the least important mechanism.

Description: Plankton records from three ATLANTIS II cruise tracks near the west African coast reveal a deep penetration of northern forms into tropical waters. They are carried there by the clockwise movement of the North Atlantic Gyre and are found mixed with subtropical and tropical forms. In light of these plankton records, and previous ones from other parts of the Gyre, a view of North Atlantic faunal parcelling is given. The traditional three-fold parcelling (northern, subtropical and tropical) is recognizable. However, gyral circulation tends to generate a rotary pattern of distribution with abundant faunal mixing. The subtropical fauna occupies the core of the Gyre and mixed faunal associations occur around the margins. The northern and tropical faunas contribute to these mixed faunal associations along clockwise dispersal routes.

Description: The foraminifer Rosulina globularis d'Orbigny from natural and laboratory populations is occasionally preyed upon by free-living, marine nematodes. Borings 3.7 to 14.3 in diameter in the tests of living and dead specimens of R. globularis and dead specimens of Eolivina doniezi Cushman and Wickenden from the same natural and laboratory populations are attributed to the predaceous nematodes. Predation in the laboratory populations is greater than in the natural populations, especially among juvenile specimens of R. globuluris. Borings in R. globuluris occur characteristically in the outer whorl, whereas, those in B. doniezi are generally confined to the apertural half of the test. This preference for the area of wall penetration is thought to correspond to the accessibility or living position of the prey. However, several incomplete borings coincide with test pores, and thus represent test penetration in an area of least resistance. Identical borings occur in Holocene and Cretaceous bathyal and neritic foraminifers. Another kind of borings in these specimens, while in part resembling gastropod boreholes, may likewise be due to soft-bodied organisms. Evidence of predation provides ecologic and paleoecologic information on the living habits, habitat, and community structure of the foraminiferal prey, and can directly influence the interpretation of foraminiferal production and rates of sedimentation based on foraminiferal production.