Autumn bloom of antarctic pack-ice algae.

An autumn bloom of sea-ice algae was observed from February to June of 1992 within the upper 0.4 meter of multiyear ice in the Western Weddell Sea, Antarctica. The bloom was reliant on the freezing of porous areas within the ice that initiated a vertical exchange of nutrient-depleted brine with nutrient-rich seawater. This replenishment of nutrients to the algal community allowed the net production of 1760 milligrams of carbon and 200 milligrams of nitrogen per square meter of ice. The location of this autumn bloom is unlike that of spring blooms previously observed in both polar regions.

Distributions of phytoplankton blooms in the southern ocean.

A regional pigment retrieval algorithm for the Nimbus-7 Coastal Zone Color Scanner (CZCS) has been tested for the Southern Ocean. The pigment concentrations estimated with this algorithm agree to within 5 percent with in situ values and are more than twice as high as those previously reported. The CZCS data also revealed an asymmetric distribution of enhanced pigments in the waters surrounding Antarctica; in contrast, most surface geophysical properties are symmetrically distributed. The asymmetry is coherent with circumpolar current patterns and the availability of silicic acid in surface waters. Intense blooms (>1 milligram of pigment per cubic meter) that occur downcurrent from continental masses result from dissolved trace elements such as iron derived from shelf sediments and glacial melt.

Who does well in a day treatment program? Following patients through 6 months of treatment.

Two rating scales were administered to 44 consecutive admissions to a day treatment program. The anticipated length of stay was 6 months. Better patient outcome was expected where the clinician's Global Assessment Scale (GAS) correlated with the patient's Self Assessment Scale (SAS). Data did not support the congruence of clinician and patient ratings. However, low GAS scores at the point of initial assessment seemed to "predict" early dropout. A follow-up inquiry showed that those who completed the program were in higher-functioning placements than those who dropped out early. Hence, those who benefited most were those who completed the program. Also observed was the fact that males had significantly higher SAS scores. How this contributed to length of stay is discussed.

Particulate organic matter delta 13C variations across the Drake Passage.

A 7 % gradient in the delta 13C of suspended particulate organic matter (POM) was observed in samples taken during two transects across the Drake Passage during March 1986. This POM delta 13C transition from -23.2 % at 53.3 degrees S to values as low as -30.3 % at > 62 degrees S does not track previously reported abrupt changes in water chemistry and plankton species composition associated with the Polar Front Zone that resides at approximately 58 degrees S in this region. Also, the north-south isotopic trend is not accompanied by significant changes in POM carbon or nitrogen concentrations, or in POM C/N. Differences in plankton standing crop or biochemistry (e.g., lipid content) therefore do not appear responsible for the isotopic trends observed. The latitudinal change in POM delta 13C is, however, highly correlated with water temperature and with the calculated concentration of CO2 (aq) at equilibrium with atmospheric CO2. These observations are consistent with the hypothesis that [CO2 (aq)] significantly influences POM delta 13C in ocean surface waters.

Staff and patients: divergent views of treatment.

A patient-staff survey, focusing on the efficacy of treatment and aftercare, showed inconsistencies in the way staff perceived treatment given patients at a large municipal acute care hospital. Primary therapists, psychiatrists, and psychologists saw treatment in a routine, standardized fashion, whereas nurses, social workers, activity therapists, and others viewed treatment in more elaborate, individualized terms. The survey also showed disparities between what staff intended to do and what patients perceived was happening to them. Implications of these findings and recommendations for coordinating staff efforts and clarifying patient understanding of treatment are presented.

Antarctic mesopelagic micronekton: evidence from seabirds that pack ice affects community structure.

Through a multidisciplinary project (AMERIEZ), with an unusual complement of components, previously unknown temporal and spatial dimensions to the structure of Antarctic epipelagic and mesopelagic communities were revealed. In late spring, an abundance of crustacean species thought to occur only below 300 meters was detected in ice-covered surface waters. Evident in ice-free waters were the expected occurrence patterns of these normally nonmigratory mesopelagic organisms. Where the pack was consolidated and little light penetrated to depth, primary and secondary production was confined to ice floes, and the physical environment immediately beneath the ice was reminiscent of a mesopelagic one. This suite of characteristics possibly explains why the crustaceans resided at the surface.

Silicification by diatoms.

The species-specific, genetically determined silica frustule of diatoms provides an excellent eukaryotic model for understanding the process of biomineralization and how it is regulated. An effort is made to define molecular events and biochemical constituents in silicon mineralization and to correlate these events with those aspects of silica frustule morphogenesis which have been reported in the published work. A sequential series of steps of silicic acid interaction with the cell is proposed which might be expected for silicon metabolism leading to cell wall formation. A model is put forward that provides for a conceptual framework for continued studies in this area, and provides testable hypotheses which should lead to a greater understanding of biomineralization processes in general and silicification in particular.

Heat-labile alkaline phosphatase from Antarctic bacteria: Rapid 5' end-labeling of nucleic acids.

A heat-labile alkaline phosphatase has been purified to near homogeneity from HK47, a bacterial strain isolated from Antarctic seawater. The active form of the enzyme has a molecular weight of 68,000 and is uniquely monomeric. The optimal temperature for the enzymatic activity is 25 degrees C. Complete and irreversible thermal inactivation of the enzyme occurs in 10 min at 55 degrees C. By using this heat-labile enzyme for dephosphorylation followed by a 10-min heat treatment, rapid end-labeling of nucleic acids by T4 polynucleotide kinase has been achieved.

Bacterial plasmids in antarctic natural microbial assemblages.

Samples of psychrophilic and psychrotrophic bacteria were collected from sea ice, seawater, sediments, and benthic or ice-associated animals in McMurdo Sound, Antarctica. A total of 155 strains were isolated and tested for the presence of plasmids by DNA agarose gel electrophoresis. Thirty-one percent of the isolates carried at least one kind of plasmid. Bacterial isolates taken from sediments showed the highest plasmid incidence (42%), and isolates from seawater showed the lowest plasmid incidence (20%). Plasmids were significantly more frequent in the strains which had been first isolated from low-nutrient media (46%) than in the strains which had been isolated from high-nutrient media (25%). Multiple forms of plasmids were observed in two-thirds of the plasmid-carrying strains. A majority of the plasmids detected were estimated to have a mass of 10 megadaltons or less. Among 48 plasmid-carrying strains, 7 showed antibiotic resistance. It is concluded that bacterial plasmids are ubiquitous in natural microbial assemblages of the pristine marine ecosystem of Antarctica.

Sea Ice Microbial Communities: Distribution, Abundance, and Diversity of Ice Bacteria in McMurdo Sound, Antarctica, in 1980.

An abundant and diverse bacterial community was found within brine channels of annual sea ice and at the ice-seawater interface in McMurdo Sound, Antarctica, in 1980. The mean bacterial standing crop was 1.4 x 10 cells m (9.8 mg of C m); bacterial concentrations as high as 1.02 x 10 cells m were observed in ice core melt water. Vertical profiles of ice cores 1.3 to 2.5 m long showed that 47% of the bacterial numbers and 93% of the bacterial biomass were located in the bottom 20 cm of sea ice. Ice bacterial biomass concentration was more than 10 times higher than bacterioplankton from the water column. Scanning electron micrographs showed a variety of morphologically distinct cell types, including coccoid, rod, fusiform, filamentous, and prosthecate forms; dividing cells were commonly observed. Approximately 70% of the ice bacteria were free-living, whereas 30% were attached to either living algal cells or detritus. Interactions between ice bacteria and microalgae were suggested by a positive correlation between bacterial numbers and chlorophyll a content of the ice. Scanning and transmission electron microscopy revealed a close physical association between epibacteria and a dominant ice alga of the genus Amphiprora. We propose that sea ice microbial communities are not only sources of primary production but also sources of secondary microbial production in polar ecosystems. Furthermore, we propose that a detrital food web may be associated with polar sea ice.

Sea ice microbial communities. III. Seasonal abundance of microalgae and associated bacteria, Mcmurdo Sound, Antarctica.

Numbers of bacteria in annual sea ice increased directly with numbers of algae during the 1981 spring ice diatom bloom in McMurdo Sound, Antarctica. Algae and bacteria in a control site grew at rates of 0.10 and 0.05 day(-1), respectively, whereas in an experimentally darkened area neither increased after six weeks. Epiphytic bacteria grew at a rate twice that of the nonattached bacteria and were significantly larger, contributing approximately 30% of the total bacterial biomass after October. The microalgal assemblage was dominated by two species of pennate diatoms, anAmphiprora sp. andNitzschia stellata. Greater than 65% of epiphytic bacteria were associated withAmphiprora sp. after October.N. stellata, however, remained largely uncolonized throughout the study. We hypothesize that microalgae stimulate bacterial growth in sea ice, possibly by providing the bacteria with organic substrates.

Studies on the biochemistry and fine structure of silica shell formation in diatoms : Division cycle and chemical composition of Navicula pelliculosa during light-dark synchronized growth.

Cell division in Navicula pelliculosa (Bréb.) Hilse, strain 668 was synchronized with an alternating regime of 5 h light and 7 h dark. Cell volume and dry weight increased only during the light period. DNA synthesis, which began during the third h of light, was followed sequentially by mitosis, cytokinesis, silicic acid uptake, cell wall formation, and cell separation. Silicification and a small amount of net synthesis of DNA, RNA and protein occurred during the dark at the expense of carbohydrate reserves accumulated during the light period. Cells kept in continuous light, after synchronization with the light-dark regime, remained synchronized through a second division cycle; the sequence of morphological events was the same as that in the light-dark division cycle, but the biosynthesis of macromolecular components changed from a stepwise to a linear pattern. The silicon-starvation synchrony was improved by depriving light-dark synchronized cells of silicic acid at the beginning of their division cycle, then resupplying silicic acid to cells blocked at wall formation.

Synergistically stimulated (Na+,K+)-adenosine triphosphatase from plasma membrane of a marine diatom.

An ATP-hydrolyzing activity with the properties of a Mg(2+)-dependent (Na(+),K(+))-ATPase (ATP phosphohydrolase, EC 3.6.1.3) from a 20-fold purified plasma membrane fraction of the marine diatom, Nitzschia alba is described. The basal activity requires Mg(2+) and further stimulation by Na(+) or Na(+) plus K(+) is dependent on the presence of Mg(2+); Mn(2+) or Co(2+) can partially substitute for the divalent cation requirement but Ca(2+) equimolar with Mg(2+) inhibits the activity by 54%. ATP is the preferred substrate for the Na(+) plus K(+) stimulated activity, while CTP, UTP, and ADP are only slightly hydrolyzed. The apparent K(m) is 8 x 10(-4) M ATP. The ATP hydrolysis-rate is dependent on the relative concentrations of Na(+) and K(+); the K(0.5) for Na(+) and K(+) are 2 mM and 50 mM, respectively. Basal activity is synergistically stimulated by Na(+) plus K(+) only at certain ion concentrations and shows a strong specificity for both cations. In the presence of Na(+) at 5 mM and K(+) at 350 mM, the ATPase is completely inhibited by p-chloromercuric benzoic acid 10(-4) M, N-ethyl maleimide 10(-3) M, and iodoacetamide 10(-2) M, but is insensitive to ouabain at 10(-7) to 10(-3) M. This study demonstrates for the first time that algal plasma membrane contains an ATPase that is synergistically stimulated by Na(+) and K(+).