C4-C7 alkenones in deep sea sediments

It is believed that C4 to C7 hydrocarbons in petroleum are formed by the cracking of organic matter at depths generally exceeding 1,000 m at temperatures in excess of 50 °C (Cordel, 1972; Dow, 1974; Tissot et al., 1974)). Also, none of the alkanes in the butane-heptane range are formed biologically as far as is known at present. Consequently, it is thought that they do not occur in shallow, Recent sediments. In 1962, I analysed 22 samples of Recent sediments from 7 different environments and verified that these hydrocarbons were not present at the p.p.m. level (Dunton and Hunt, 1962) although traces of a few hydrocarbons such as butane, isobutane, isopentane and n-heptane have been found (Sokolov, 1957; Veber and Turkeltaub, 1958; Erdman et al., 1958; Emery and Hoggan, 1958). No identification of individual hexanes or heptanes has been reported except when there has been clear evidence of seepage from deeper source sediments (McIver, 1973).

Abundance of copepods from multinet samples during POLARSTERN cruise ANT-XX/1

Abundance and species composition of copepods were studied during the expedition ANT XXI/1 on a latitudinal transect in the eastern Atlantic from 34°49.5' N to 27°28.1' S between 2-20 November 2002. Stratified zooplankton tows were carried out at 19 stations with a multiple opening-closing net between 300 m water depth and the surface. Cyclopoid and calanoid copepods showed similar patterns of distribution and abundance. Oithona was the most abundant cyclopoid genus, followed by Oncaea. A total of 149 calanoid copepod species were identified. Clausocalanus was by far the most abundant genus, comprising on average about 45% of all calanoids, followed by Calocalanus (13%), Delibus (9%), Paracalanus (6%), and Pleuromamma (5%). All other genera comprised on average less than 5% each, with 40 genera less than 1%. The calanoid copepod communities were distinguished broadly in accordance with sea surface temperature, separating the subtropical from the tropical stations, and were largely determined by variation in species composition and species abundance. Nine Clausocalanus species were identified. The most numerous Clausocalanus species was C. furcatus, which on average comprised half of all adult of this genus. C. pergens, C. paululus, and C. jobei, contributed an average of 19%, 9%, and 9%, respectively. The Clausocalanus species differed markedly in their horizontal and vertical distributions: C. furcatus, C. jobei, and C. mastigophorus had widespread distributions and inhabited the upper water layers. Major differences between the species were found in abundance. C. paululus and C. arcuicornis were biantitropical and were absent or occurred in very low numbers in the equatorial zone. C. parapergens was found at all stations and showed a bimodal distribution pattern with maxima in the subtropics. C. pergens occurred in higher numbers only at the southern stations, where it replaced C. furcatus in dominance. In contrast to the widespread species, the bulk of the C. paululus, C. arcuicornis, C. parapergens, and C. pergens populations was concentrated in the colder, deeper water layers below the thermocline, thereby avoiding the warm surface waters. C. lividus was found only at the most northern and C. ingens only at the most southern stations. Both species were found almost exclusively in the upper 50 m. The distinct differences in abundance and horizontal and vertical distribution suggest a strong ecological differentiation among the Clausocalanus species.

Characterization of two polymorphisms in the leukotriene C4 synthase gene in an Australian population of subjects with mild, moderate, and severe asthma

Background: The cysteinyl-leukotrienes (cys-LTs) are proinflammatory mediators that are important in the pathophysiology of asthma. LTC4 synthase is a key enzyme in the cys-LT biosynthetic pathway, and studies in small populations have suggested that a promoter polymorphism (A(-444)C) in the gene might be associated with asthma severity and aspirin intolerance. Objective: We sought to screen the LTC4 synthase gene for polymorphisms and to determine whether there is an association between these polymorphisms and asthma severity or aspirin sensitivity in a large, well-phenotyped population and to determine whether this polymorphism is functionally relevant. Methods: The coding regions of the LTC4 synthase gene were screened for polymorphisms and the A(-444)C polymorphism was analyzed in a large Australian white adult population of mild (n = 282), moderate (n = 236), and severe asthmatic subjects (n = 86) and nonasthmatic subjects (n = 458), as well as in aspirin-intolerant asthmatic subjects (n = 67). The functional activity of the promoter polymorphism was investigated by transient transfection of HL-60 cells with a promoter construct. Results: A new polymorphism was identified in intron 1 of the gene (IVS1-10c>a) but was not associated with asthma. Association studies showed that the A(-444)C polymorphism was weakly associated with asthma per se, but there was no association between the C-444 allele and chronic asthma severity or aspirin intolerance. A meta-analysis of all the genetic studies conducted to date found significant between-study heterogeneity in C-444 allele frequencies within different clinical subgroups. In vitro functional studies showed no significant differences in transcription efficiency between constructs containing the A(-444) allele or the C-444 allele. Conclusions: Our data confirm that, independent of transcriptional activity, the C-444 allele in the LTC4 synthase gene is weakly associated with the asthma phenotype, but it is not related to disease severity or aspirin intolerance.

Comparison of Belowground Biomass in C3- and C4-Dominated Mixed Communities in a Chesapeake Bay Brackish Marsh

Belowground biomass is a critical factor regulating ecosystem functions of coastal marshes, including soil organic matter (SOM) accumulation and the ability of these systems to keep pace with sea-level rise. Nevertheless, belowground biomass responses to environmental and vegetation changes have been given little emphasis marsh studies. Here we present a method using stable carbon isotopes and color to identify root and rhizomes of Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller (C3) and Spartina patens (Ait.) Muhl. (C4) occurring in C3− and C4-dominated communities in a Chesapeake Bay brackish marsh. The functional significance of the biomass classes we identified is underscored by differences in their chemistry, depth profiles, and variation in biomass and profiles relative to abiotic and biotic factors. C3 rhizomes had the lowest concentrations of cellulose (29.19%) and lignin (14.43%) and the lowest C:N (46.97) and lignin:N (0.16) ratios. We distinguished two types of C3 roots, and of these, the dark red C3 roots had anomalously high C:N (195.35) and lignin:N (1.14) ratios, compared with other root and rhizome classes examined here and with previously published values. The C4-dominated community had significantly greater belowground biomass (4119.1 g m−2) than the C3-dominated community (3256.9 g m−2), due to greater total root biomass and a 3.6-fold higher C3-root:rhizome ratio in the C4-dominated community. C3 rhizomes were distributed significantly shallower in the C4-dominated community, while C3 roots were significantly deeper. Variability in C3 rhizome depth distributions was explained primarily by C4 biomass, and C3 roots were explained primarily by water table height. Our results suggest that belowground biomass in this system is sensitive to slight variations in water table height (across an 8 cm range), and that the reduced overlap between C3 and C4 root profiles in the C4-dominated community may account for the greater total root biomass observed in that community. Given that future elevated atmospheric CO2 and accelerated sea-level rise are likely to increase C3 abundance in Atlantic and Gulf coast marshes, investigations that quantify how patterns of C3 and C4 belowground biomass respond to environmental and biological factors stand to improve our understanding of ecosystem-wide impacts of global changes on coastal wetlands.

Mapping of C4 plant input from North West Africa into North East Atlantic sediments

Mapping the abundance of 13C in leaf-wax components in surface sediments recovered from the seafloor off northwest Africa (0-35°N) reveals a clear pattern of delta13C distribution, indicating systematic changes in the proportions of terrestrial C3 and C4 plant input. At 20°N latitude, we find that isotopically enriched products characteristic of C4 plants account for more than 50% of the terrigenous inputs. This signal extends westward beneath the path of the dust-laden Sahara Air Layer (SAL). High C4 contributions, apparently carried by January trade winds, also extend far into the Gulf of Guinea. Similar distributions are obtained if summed pollen counts for the Chenopodiaceae-Amaranthaceae and the Poaceae are used as an independent C4 proxy. We conclude that the specificity of the latitudinal distribution of vegetation in North West Africa and the pathways of the wind systems (trade winds and SAL) are responsible for the observed isotopic patterns observed in the surface sediments. Molecular-isotopic maps on the marine-sedimentary time horizons (e.g., during the last glacial maximum) are thus a robust tool for assessing the phytogeographic changes on the tropical and sub-tropical continents, which have important implications for the changes in climatic and atmospheric conditions.

TABLE 1. - Taxa list at Bahi'a Ushuaia and Bahi'a Golondrina

This paper describes the composition and abundance of mesozooplankton of Bahi'a Ushuaia and Bahi'a Golondrina. These small bays are located in the northern Beagle Channel. Sampling was carried out from January 20 to 23, 2001 and samples were collected from the upper layer at nine stations. This study is the first research on mesozooplankton in this part of the Beagle Channel. Due to their dominance in the mesozooplankton community, we compared our Copepoda data with those reported by other authors from Antarctic coastal environments. By applying cluster analysis, we found two station groups in both bays: one in slightly polluted zones and the other in undisturbed external zones. Four assemblages in Bahi'a Ushuaia and two in Bahi'a Golondrina were determined by using non-metric multidimensional scaling (MDS) and cluster analysis. Mesozooplanktonic assemblages showed a certain resemblance in zones with and without anthropogenic influence. Most of the copepod species in our samples are typical of the sub-Antarctic region. Oithona similis (=0. helgolandica sensu Ramirez, 1966), Oncaea curvata, and Ctenocahmus citer show either similar or higher abundances at Antarctic coastal sites, including the upper layer in oceanic areas, in comparison with sub-Antarctic coastal localities. This suggests that, in agreement with other findings, the Polar Front is probably not a major geographic boundary for the distribution of these species.