Denitrification in Bahia Darwin (Galapagos Islands) an intermittent anoxic basin in the tropics

Changes in oxygen and nitrate in Bahia Darwin between July 1968 and March 1969 indicate that denitrification occurred in the deeper waters of this tropical, intermittently anoxic basin. Assuming constant rates of oxidation of organic matter in equally spaced depth intervals below the pycnocline depth, the rate of denitrification was estimated to be about 62.0 µg-atom NO₃-N/liter/year. This rate is attributable to denitrification in the water column because a smaller rate was estimated for strata closer to the sediment water interface.Contribution No. 3193 from the Woods Hole Oceanographic Institution. Woods Hole, Massachusetts 02543. This study was supported in part by the National Science Foundation Grants GA 29303 and GB 6870. Reprints should be requested from the second author.     

Effects of PCB on interspecific competition in natural and gnotobiotic phytoplankton communities in continuous and batch cultures

The toxicity of polychlorinated biphenyls (PCB) to the diatomThalassiosira pseudonana (formerlyCyclotella nana), grown in pure and mixed cultures, was greatest when in competition with other species. Continuous cultures were superior to batch cultures for studying competitive interactions, and PCB caused greater alteration of species composition in continuous cultures than it did in batch cultures. Natural phytoplankton communities from Vineyard Sound, maintained in continuous culture, responded to PCB stress the same as did gnotobiotic communities, withT. pseudonana showing similar responses in both communities. A PCB concentration of 0.1 μg/liter (0.1 part per billion), a level not uncommon in natural waters, did not affect algal growth in pure cultures but caused substantial disruption of continuous culture communities. The possible impact of PCB pollution on natural phytoplankton communities is discussed. Contribution No. 3181 from the Woods Hole Oceanographic Institution.     

Pelagic larvae of New England intertidal gastropods

Summary The egg case, pelagic larva and postlarva ofNassarius trivittatus Say are described and figured from specimens reared in the laboratory. Similarities and differences in the larvae of New England and European species ofNassarius are indicated.

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Zusammenfassung Die Arbeit beschreibt die Eierkapseln, die pelagischen Larven und die Postlarven vonNassarius trivittatus Say. Abbildungen von Examplaren, die im Laboratorium aufgezogen wurden, werden wiedergegeben.

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Contribution number 1453, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.     

Denitrification in salt marsh sediments: Evidence for seasonal temperature selection among populations of denitrifiers

Direct measurements of bacterial denitrification in salt marsh sediments near Woods Hole, Massachusetts were made over a 10-month period using a simple and precise gas-chromatographic technique. Based on laboratory experiments at 5°, 10°, and 20°C, it is shown that seasonal temperature variations select for at least two distinct populations of denitrifiers.In situ incubations suggest that resident populations of denitrifying bacteria are cold-sensitive. Salt marsh denitrifying bacteria are not optimally adapted to their thermal environment, but to temperatures 5°–10°C higher. In these water-logged muds, rates of bacterial denitrification (0.3–1.5g N₂/gm sediment-hr) are up to three orders of magnitude greater than maximum potential rates of insitu bacterial and algal nitrogen fixation.Supported by the Victoria Foundation and NSF grants GA 28365, GA 28272, and GA 41506. This is Contribution No. 3730 from the Woods Hole Oceanographic Institution.     

Photoacoustic spectroscopic analysis of marine phytoplankton

The 500–800 nm spectra of replicata phytoplankton cultures freeze-dried upon glass fiber filters were determined both by photoacoustic spectroscopy (PAS) and by photoelectric absorption spectrophotometry. A number of the features of biological interest are better resolved in the PAS spectra. Further, PAS is sufficiently sensitive that it could be applied in the analysis of readily obtainable field samples.Contribution number 9322 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. The work at Woods Hole was supported by the Office of Naval Research contract ONR N00014-66-c 0241, National Science Foundation grant GA 002783 and the Tai Ping Foundation. Reprint requests should be addressed to the first author.     

On the unlikelihood of non-aqueous biosystems

Theunique ability of the solvent liquid water to form polymorphic, 3-dimensional, H-bonded aggregates and solvation envelopes of widely different character (hydrophilic or coulombic hydration and hydrophobic hydration) is anecessary condition for the realization of the levels of order in form and complexity in function required by carbonaceous biotic systems.Woods Hole Oceanographic Institution Contribution No. 2572.     

Characteristics of two marine nitrite oxidizing bacteria,Nitrospina gracilis nov. gen. nov. sp. and Nitrococcus mobilis nov. gen. nov. sp.

Summary Two new nitrite oxidizing bacteria for which the names Nitrococcus mobilis and Nitrospina gracilis are proposed were isolated from the marine environment. Nitrococcus mobilis was cultured from South Pacific waters and it is a large motile coccus with unique tubular cytomembranes. Nitrospina gracilis was isolated from South Atlantic waters and it is a long slender rod which lacks an extensive cytomembrane system. Both are obligate marine organisms and both are obligate chemoautotrophs. The fine structure of these organisms is detailed.Contribution No. 2631 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543.     

Nitrogen budget of a subarctic stream altered by beaver (Castor canadensis)

Beaver (Castor canadensis) influence stream ecosystems through their wood cutting and dam building activities. To quantify this influence we have used measured rates of nitrogen dynamics to construct a nitrogen budget for a section of a second order stream in eastern Québec and a beaver dam in that stream. The budget demonstrates the importance of sediment accumulations and an expanded wetted area to the annual nitrogen economy and to pathways of nitrogen cycling. Major changes after impoundment (per unit area) include a reduction in allochthonous nitrogen and an increase in nitrogen fixation by sediment microbes. Overall, the beaver-modified section accumulated 10³ times more nitrogen than before alteration. The ecosystem implications of beaver activity suggest that current concepts of patterns and processes in running waters require modification.Research support by NSF grant DEB 81-05677 and the Woods Hole Oceanographic Institution. this is Contribution No. 5565 from the Woods Hole Oceanographic Institution and No. 88 from the Institution's Matamek Research Station     

The fine structure of Chromatium buderi

Summary The fine structure of the phototrophic sulfur bacterium Chromatium buderi was studied in ultrathin sections and freeze-etch preparations.In addition to an intracytoplasmic membrane system common to all species of the Chromatiaceae, C. buderi contained extended lamellar membrane structures possibly due to too high light intensities during growth. The cell wall of C. buderi was found to be covered by a honeycomb-like outer layer consisting of macromolecular wine-glass shaped subunits 60–80 nm by 60 nm in size. This outer cell wall layer appears to be a typical property of the large cell Chromatium species.Contribution No. 3008 of the Woods Hole Oceanographic Institution.     

Fünf neue Arten der Gattung Halacarus (Acari, Halacaridae) aus dern Atlantik

Five Halacarus species were found in deep sea collections of the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts. The five species, viz. Halacarus atlanticus sp.n. H. longior sp.n. H. obtusus sp.n. H. peregrinus sp.n. and H. triunguis sp.n. are described, and discussed in terms of related species.     

A similarity measure sensitive to the contribution of rare species and its use in investigation of variation in marine benthic communities

Summary We propose a new measure of similarity, the normalized expected species shared or NESS. The measure is based on the expected number of species shared between random samples of size, m, drawn from a population. The NESS measure is shown to be a generalization of Morisita's similarity and is demonstrated to be less biased than other commonly used measures. The contribution of dominant and rare species is explicit according to the sample size, m, chosen. For large m, NESS is sensitive to the less common species in the populations to be compared.The NESS measure has been used to cluster a 2-year sequence of subtidal benthic samples taken after a severe disturbance. The NESS measure is responsive to the less common species so that both a temporal progression in community recovery and seasonal variation are revealed.Contribution No. 3699 from the Woods Hole Oceanographic Institution     

Response of marine phytoplankton to low levels of arsenate

Phytoplankton species vary widely in their degree of inhibitionto low levels of dissolved arsenate (1 – 10 ? ambient).Similarly, natural phytoplankton assemblages cultivated outdoorsunder ambient temperature and nutrient conditions indicate thatthe observed variance in sensitivity is sufficient to causea marked change in species composition and succession in dosedassemblages relative to controls, again at very low levels ofarsenate. The changes in species that occurred, however, werenot always similar to the response predicted from single–speciescultures. In addition, a species' level of resistance to arsenateis often not comparable with its resistance to other anthropogenicstress. It is therefore questionable whether predictions concerningenvironmental consequences of a given pollutant can be madeon the basis of laboratory bioassays of a single species. ¹Contribution # 4695 Woods Hole Oceanographic Institution ²Present address: Academy of Natural Sciences, Division of EnvironmentalResearch, Benedict Estuarine Research Laboratory, Benedict,MD 20612, USA     

A lobular,ammonia-oxidizing bacterium,Nitrosolobus multiformis Nov. Gen. Nov. sp.

Summary Nitrosolobus multiformis is a lobular shaped, previously undescribed ammonia-oxidizing bacterium. The organism is ubiquitous and was isolated from soil samples obtained in various parts of the world. Its lobular nature and its internal, partially compartmentalized cytoplasm makes it morphologically unique and easily distinguishable from all other microorganisms. Physiological compartmentalization also occurs and is characterized by glycogen deposition in the peripheral compartments of the cell. The cells are obligate chemoautotrophs using CO₂ and ammonia as primary carbon and energy sources. Its obligate chemoautotrophic nature stems primarily from a metabolic deficiency. Even though the cells cannot be grown on an organic medium the cells still have a slight heterotrophic potential and are able to oxidize and assimilate minute amounts of acetate in the absence of an inorganic energy source.Contribution No. 2606 from the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543.     

A note on the transient stage of the random dispersal of logistic populations

The transient stage of the random dispersal of logistic populations is investigated, using a Sturm-Liouville series leading to an infinite system of non-linear integral equations. These equations are then solved via a successive approximation scheme. R. A. Fisher's (steady-state) velocity of advance paradox is discussed. An illustrative example is worked to the second order of approximation. Contribution No. 1020 of the Woods Hole Oceanographic Institution.     

Growth rate stimulation of marine pseudomonads by thiosulfate

The oxidation of thiosulfate to tetrathionate exerts a definite growth rate stimulation in glucose, acetate, and yeast extract cultures of some marine pseudomonads. The failure to find this effect in earlier studies with terrestrial isolates may lie in the particular conditions used in the present experiments (constant pH, high ratio of thiosulfate to organic substrate) or in the different metabolic characteristics of the marine isolates.Contribution No. 3220 from the Woods Hole Oceanographic Institution.     

Sclerosponge growth rate as determined by 210Pb and Δ14C chronologies

Measurements of bomb-produced radiocarbon and ²¹⁰Pb provide concordant estimates of the growth rate of the sclerosponge Ceratoporella nicholsoni collected from the reef slope of northern Jamaica. Radiocarbon measurements of older growth bands in the same specimen are similar to the time history of radiocarbon in coral bands from two sites in the northwestern Atlantic. Furthermore, ²¹⁰Pb and stable Pb analyses reveal that the sclerosponge incorporates this element at much higher concentrations than corals.Contribution No. 5955 to the Woods Hole Oceanographic Institution     

Pelagic larvae of New England intertidal gastropods II. Anachis avara

Summary The egg case, pelagic larvae, and young juvenile of Anachis avara Say, a species of prosobranch gastropod belonging to the family Columbellidae, are described and figured from specimes reared in the laboratory.

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Zusammenfassung Die Arbeit beschreibt die Eierkapseln, die pelagischen Larven und die Jugendformen von Anachis avara Say, einer prosobranchen Gastropoden-Spezies, die zur Familie der Columbelliden gehört. Abbildungen von Exemplaren, die im Laboratorium aufgezogen wurden, werden wiedergegeben.

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Contribution number 1341, Woods Hole Oceanographic Institution. This research was supported by N.S.F. grant no. 17883.     

Enrichments of aquatic bacteria in continuous culture

Summary A chemostat was employed for the enrichment and eventual isolation of a variety of heterotrophic bacteria from seawater. Experimental attempts to separate single species from mixed cultures of known composition showed that successful or unsuccessful competition for the limiting substrate is based upon the particular growth parameters of the individual species under the given culture conditions. The technique appears to be suitable to enrich reproducibly for bacterial species of little substrate specificity. Applications in ecological studies are discussed.Dedicated to Prof. C. B. Van Niel on the occasion of his 70th birthday.Contribution No. 1919 of the Woods Hole Oceanographic Institution. Supported by the National Science Foundation Research Grant No. GB-5199.     

Growth and metabolism in a marine nematode,Enoplus communis Bastian

Summary The life history and metabolism of a marine nematode, Enoplus communis Bastian, was studied. The species has an annual life cycle, spawning taking place in early spring. Maturity is reached in fall and early winter, and both sexes overwinter with their gonads fully developed.The metabolism is not temperature-compensated and there is no difference in respiration between the two sexes.The respiration rate is fairly low in the fertilized, uncleaved eggs (about 600 mm³ O₂/g/hr). Right after hatching, the oxygen consumption increases sharply to a value about three times that of the eggs. Then it drops quickly, but in animals weighing between 6 and 10 g, another sudden rise occurs, followed by a second drop and subsequent leveling of the curve. The first increase in metabolic rate from egg to first juvenile stage might be due to the activation of metabolically important substances. The following changes, however, are most likely correlated with the process of molting and are probably due to changes in the percentage of dry tissue matter in animals prior to and after ecdysis.The large fluctuations in respiration rate occuring in animals of different size, despite a constant surface/volume ratio, suggest that body surface proper does not control oxygen consumption in this species.Contribution no. 1059 from the Woods Hole Oceanographic Institution, Woods Hole, Mass.Supported by NSF grant G-4813.     

Characterization of a DMSP-degrading bacterial isolate from the Sargasso Sea

A bacterium which cleaves dimethylsulfoniopropionate (DMSP) to form dimethylsulfide (DMS) was isolated from surface Sargasso Sea water by a DMSP enrichment technique. The isolate, here designated LFR, is a Gram-negative, obligately aerobic, rod-shaped, carotenoid-containing bacterium with a DNA G+C content of 70%. Sequencing and comparison of its 16S ribosomal ribonucleic acid (rRNA) with that of known eubacteria revealed highest similarity (91% unrestricted sequence similarity) to Roseobacter denitrificans (formerly Erythrobacter species strain OCh114), an aerobic, bacteriochlorophyll-containing marine representative of the -Proteobacteria. However, physiological differences between the two bacteria, and the current lack of other characterized close relatives, preclude assignment of strain LFR to the Roseobacter genus. Screening of fifteen characterized marine bacteria revealed only one, Pseudomonas doudoroffii, capable of degrading DMSP to DMS. Strain LFR is deposited with the American Type Culture Collection (ATCC 51258) and 16S rRNA sequence data are available under GenBank accession number 15345.Contribution no. 8337 of the Woods Hole Oceanographic Institution