Autochthonous Marine Research Articles

High incidence of antibiotic multi-resistant bacteria in coastal areas dedicated to fish farming

Marine bacteria exposed to antibiotics in fish farms can acquire antimicrobial resistance by mobile genetic elements and horizontal gene transfer. A total of 872 autochthonous marine bacterial strains was isolated from samples collected from four different fish farms located at northern and southern Italian Adriatic Sea. Resistance to only tetracycline (17%) and to trimethoprim–sulfadiazine (7%) were the most frequent patterns obtained, while flumequine resistance has recorded in only 0.3% of the strains. Comparing strains isolated from coastal areas and fish farms, a significant higher incidence (4% versus 10%) of multi-resistant strains in aquaculture centers was found. Significant differences in antibiotic resistance incidence were also detected among the four fish farms due probably to different approaches in farm management and the more or less frequent use of antibiotics. Antibiotic-resistant and multi-resistant strains isolated constitute an environmental reservoir directly involved in the seafood chain and might represent a public health concern.

Black shale formation during the Latest Danian Event and the Paleocene–Eocene Thermal Maximum in central Egypt: Two of a kind?

The Paleocene–Eocene Thermal Maximum (PETM; ~55.8Ma) is considered as the most severe of a series of transient warming events (“hyperthermals”) that occurred during the Early Paleogene. However, the extent and magnitude of environmental changes during the short-lived warming events pre- and post-dating the PETM are still poorly constrained. In this study, we focus on the Latest Danian Event (LDE, ~61.7Ma) and compare it to the PETM. We present high-resolution micropaleontological, geochemical, and mineralogical data of the PETM and the LDE in two adjacent sections from the Gebel Qreiya area in Egypt. There, both events are characterized by a distinct set of event beds overlying an unconformity. They are associated with intense carbonate dissolution and substantial changes in the benthic foraminifera fauna. Moreover, both show an abrupt drop of siliciclastic input (sediment starvation) correlative to the onset of black shale formation and a strong enrichment in redox-sensitive trace elements. The evidence for enhanced detrital input during the onset of the PETM and a longer recovery phase with enhanced phosphorus-sedimentation during the PETM attests a stronger environmental impact of this event compared to the LDE.According to Rock-Eval and elemental analysis, the PETM as well as the LDE event beds have up to 4wt.% organic carbon, small amounts of volatile hydrocarbons, but high amounts of highly weathered and inert organic matter (“black carbon”). During pyrolysis, the extremely high temperatures for the maximum release of hydrocarbons of the PETM and LDE samples correspond to thermal heating of >170°C, which is incompatible with the sediment burial history. Therefore, we suggest that the organic matter in both event deposits does not reflect well-preserved marine biomass but predominantly represents a mixture of heavily weathered autochthonous marine material and allochthonous combustion residues. Differences in preservation and/or type of organic matter are also likely to account for the divergent stable isotope anomalies of organic carbon: the well-known negative carbon isotope anomaly at the PETM and a positive anomaly at the LDE. Although warming, water column stratification, and enhanced nutrient input may have promoted anoxic conditions on the shelf during the LDE as well as during PETM, our results support rapid sea level rise and clastic starvation as one important mechanism for black shale formation and carbon sequestration for both events. This result underlines the similarity of both hyperthermal events in terms of environmental changes recorded on the Southern Tethyan margin, with the PETM showing an additional early phase of strong detrital input not revealed at the LDE.

Virulence genes and pathogenicity islands in environmentalVibriostrains nonpathogenic to humans

Most Vibrio species in autochthonous marine microbial communities, such as Vibrio alginolyticus, Vibrio harveyi, Vibrio anguillarum among others, are considered nonpathogenic for humans. However, because many bacterial virulence genes are located in mobile genetic elements, the acquisition of mobile DNA could mediate the appearance of virulent or more virulent strains even in a species defined as nonpathogenic. In this study, we screened a collection of marine nonpathogenic Vibrio strains isolated in the area of the Venetian Lagoon for the presence of virulence and fitness genes usually present in Vibrio cholerae and Vibrio parahaemolyticus clinical isolates. More than one-third of the strains tested positive for the presence of at least one of the potential virulence/fitness genes with the gene encoding the V.cholerae neuraminidase the most frequently detected. Moreover, 13 of the environmental strains carried modified versions of the V.cholerae pathogenicity island VPI-2, and four of them also contained partial fragments of the V.parahaemolyticus Vp-PAI. The data obtained support the view of nonpathogenic Vibrio strains as a significant reservoir of virulence and fitness genes. The emergence of environmental bacteria with new virulence traits might constitute a direct concern for public health and a risk for human health.

Incorporating nutrients as a limiting factor in carbonate modelling

Nowadays, the use of process-based numerical models to predict facies distribution and stratal architecture constitutes an essential tool in sedimentary basin analysis. One of these models, the SIMSAFADIM-CLASTIC program, simulates clastic transport and sedimentation in three dimensions together with autochthonous marine carbonate production. In this code, carbonate modelling mainly follows predator–prey relationships among species associations based on Lotka–Volterra equations. The carbonate model also considers other environmental factors such as the presence of siliciclastic sediments and carbonate mud in suspension and water depth. Although these parameters are important, carbonate producers are largely conditioned by other variables, which have to be taken into account in order to obtain a more realistic approach. In this contribution, nutrient availability is added as a new limiting environmental parameter, which exerts control over carbonate producing organisms. A synthetic sample experiment is used to show that inclusion of nutrient availability is critical to reproduce carbonate lithofacies heterogeneity in a more accurate temporal and spatial disposition as a function of trophic resources.

Polyphasic approach for assessing changes in an autochthonous marine bacterial community in the presence of Prestige fuel oil and its biodegradation potential

A laboratory experiment was conducted to identify key hydrocarbon degraders from a marine oil spill sample (Prestige fuel oil), to ascertain their role in the degradation of different hydrocarbons, and to assess their biodegradation potential for this complex heavy oil. After a 17-month enrichment in weathered fuel, the bacterial community, initially consisting mainly of Methylophaga species, underwent a major selective pressure in favor of obligate hydrocarbonoclastic microorganisms, such as Alcanivorax and Marinobacter spp. and other hydrocarbon-degrading taxa (Thalassospira and Alcaligenes), and showed strong biodegradation potential. This ranged from >99% for all low- and medium-molecular-weight alkanes (C(15)-C(27)) and polycyclic aromatic hydrocarbons (C(0)- to C(2)- naphthalene, anthracene, phenanthrene, dibenzothiophene, and carbazole), to 75-98% for higher molecular-weight alkanes (C(28)-C(40)) and to 55-80% for the C(3) derivatives of tricyclic and tetracyclic polycyclic aromatic hydrocarbons (PAHs) (e.g., C(3)-chrysenes), in 60 days. The numbers of total heterotrophs and of n-alkane-, aliphatic-, and PAH degraders, as well as the structures of these populations, were monitored throughout the biodegradation process. The salinity of the counting medium affects the counts of PAH degraders, while the carbon source (n-hexadecane vs. a mixture of aliphatic hydrocarbons) is a key factor when counting aliphatic degraders. These limitations notwithstanding, some bacterial genera associated with hydrocarbon degradation (mainly belonging to α- and γ-Proteobacteria, including the hydrocarbonoclastic Alcanivorax and Marinobacter) were identified. We conclude that Thalassospira and Roseobacter contribute to the degradation of aliphatic hydrocarbons, whereas Mesorhizobium and Muricauda participate in the degradation of PAHs.

Land–ocean distribution of allochthonous organic matter in surface sediments of the Chiloé and Aysén interior seas (Chilean Northern Patagonia)

We investigated the relative distribution of allochthonous (i.e., terrigenous) organic matter in the complex, continuous, river–fjord–sound–channel–gulf system of Chile’s North Patagonia (41.5–46.5°S) in order to establish whether this organic matter can reach the open ocean or whether it is largely retained near its fluvial sources. Grain size distribution, total organic carbon and total nitrogen contents, and carbon stable isotope contents (δ 13C) were quantified in 53 surface sediment samples collected during the CIMAR Fiordos cruises 1, 4, 8, and 10, as were salinity and silicic acid concentrations in the surface waters. A principal component analysis segregated the Chiloé and Aysén interior seas into two zones: (i) the continental fjords, with sediment enriched in allochthonous organic matter, having higher C:N molar ratios (10–14) and lower δ 13C composition (−23‰ to −27‰); and (ii) the channels and gulfs, with a prevalent autochthonous marine source, having lower C:N values (6–10) and higher δ 13C composition (−20‰ to −23‰). Estuarine waters with low salinity (2–30) and high silicic acid (10–90 μM) were associated with high C:N ratios and low δ 13C in surface sediments, meaning that terrestrial organic matter was transported up to the mouth of the continental fjords. A two-source mixing model confirmed that allochthonous (terrestrial) organic matter contents (50–90%) associated with local river discharges were present within the continental fjords. On the contrary, autochthonous (marine) organic matter was prevalent (50–90%) at the sites in the marine influenced channels, sounds, and gulfs.

Vibrio cholerae O1 detection in estuarine and coastal zooplankton

Vibrio cholerae is an autochthonous marine bacterium, and its association withdiverse planktonic crustaceans has been extensively investigated; however, the pres-ence of V. cholerae on individuals of most phyla of planktonic animals is still incom-pletely understood. The objective of this study was to analyze the distribution ofV. cholerae serogroup O1 associated with specific zooplankton taxa in an estuaryand the adjacent continental shelf of the southeastern Brazilian coast. The occur-rence of the bacterium was assessed in zooplankton samples, specifically on themost abundant taxa, using direct fluorescence assay (DFA) and direct viablecount–direct fluorescence assay (DVC–DFA) methods. Vibrio cholerae O1 wasdetected in 88% of samples collected from the Santos-Bertioga estuary and in67% of samples from the shelf. The salinity of the estuarine water ranged from21.8 to 34.6, significantly lower than the shelf water which was 32.1–36.1.Salinity was the only environmental variable measured that displayed a significantcorrelation with the presence of V. cholerae (P , 0.05). Vibrio cholerae O1 was detectedin chaetognaths, pluteus larvae of echinoderms and planktonic fish eggs(Engraulidae), all new sites for this bacterium.KEYWORDS: plankton; estuary; DFA; Southwest Atlantic

Palynomorph distribution in modern tropical deltaic and shelf sediments– mahakam delta, Borneo, Indonesia

The Mahakam Delta is a tropical, fluvio‐tidally dominated delta prograding onto a mixed siliciclastic‐carbonate shelf. Surface sediments were collected from 12 distinctive depositional environments extending from the head of the Mahakam Delta to the shelf edge. Organic matter was extracted from 200 samples by acid digestion, and seven palynomorph types (pollen, embryophyte spores, fungal spores, foraminiferal linings, copepod eggs, tintinnomorphs, and dinocysts) were identified and counted, and their percentages and concentrations calculated. Total organic carbon (TOC), lithology, and depositional environments were recorded for each sediment sample. The amounts of terrestrial palynomorphs in sediments can be explained by transport and depositional processes, and four groups of environments are identified (tidally influenced, detrital peat beach, lowland rain forest, and marine shelf)‐ Because of tidal flushing of the delta plain, pollen, embryophyte spores, fungal spores and soft plant debris from the soil litter are deposited together with clastic mud at slack‐water periods. As a result, all tidally‐influenced environments exhibit constant numbers of pollen, embryophyte spores, and fungal spores per unit of TOC. In lowland rain forest sediments, there is minor clastic dilution and the numbers of pollen and spores are three to 10 times higher per unit TOC than in tidally‐influenced sediments. In detrital peat beach and marine shelf sediments, the number of sporomorphs per unit TOC is lower than expected because of the selective removal of sporomorph‐sized particles by wave action and of dilution with autochthonous marine organic matter respectively. In contrast, the amounts of marine palynomorphs in sediments are related to the depositional environments. Relative amounts of marine palynomorphs increase gradually offshore, as both the sporomorph percentages and concentrations decrease simultaneously. Once in fully marine conditions, concentrations of marine palynomorphs are comparable in all shelf environments. The marine assemblages are mainly represented by Zooplankton (copepod eggs) and benthic protists (foraminiferal linings), the phytoplanktonic constituent (dinocyst) playing a subordinate role.

Partitioning of organic matter in continental margin sediments among density fractions

Hydrodynamic processes sort and redistribute organic matter (OM) and minerals on continental margins. Density fractionations were conducted on sediments from diverse margins (Mexico margin, Gulf of Mexico, Mississippi River delta, Eel River margin) to investigate the nature, provenance and age of OM among density fractions. Mass, elemental (C and N), lignin, and surface area distributions, as well as stable carbon and radiocarbon isotopic compositions were measured. The lowest density fractions (< 1.6 g cm − 3 ) contained the highest organic carbon (OC) (up to 45%) and lignin concentrations (up to 8 mg g − 1 ) due to abundant woody debris, whereas high density fractions (> 2.5 g cm − 3 ) were OC-poor (%OC < 0.5) mineral material. Most sediment mass was found in the mesodensity fractions (1.6 to 2.5 g cm − 3 ) that contained the highest proportion of OC (up to ~ 75%) for each sediment. Stable carbon isotope compositions (δ 13C − 25.5‰ to − 22.9‰) show terrigenous OC as a significant component of density isolates from the river-dominated sediments (Gulf of Mexico, Mississippi River, and Eel margin), whereas the Mexico margin, least influenced by riverine input, was dominated by autochthonous marine OC (δ 13C ~ − 21.5‰). Radiocarbon compositions of density fractions indicate significant pre-aged OC (Δ 14C as low as − 900‰) in river-influenced sediments but not on the Mexico margin (Δ 14C > − 200‰). Ratios of vanillic acid to vanillin (Ad/Al)v among lignin oxidation products increase with increasing particle density suggesting variable lignin sources or selective degradation of lignin among the different density fractions.

Characteristics of lipid tracer compounds transported to the Arabian Gulf by runoff from rivers and atmospheric dust transport

River runoff and atmospheric fallout (dust and air particulate matter) are major input sources of natural and anthropogenic terrestrial organic and inorganic components to the Arabian seas. In this study, we report on the various lipid tracer compounds that might be transported to the Arabian Gulf by rivers, dust, and air particulate matter. These are based on geochemical analysis of sediment, dust, and particulate samples collected from Iraq, Kuwait, and Saudi Arabia. The samples were extracted with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry. The extractable organic compounds (lipids) in the samples include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, triterpenoids, carbohydrates, and petroleum hydrocarbons. The steroids and triterpenoids were major components in river and wetland samples. The major sources of these lipids were from natural vegetation, microbial (plankton and bacteria) residues in the sediments, sand, and soils, with some contribution from anthropogenic sources. Accordingly, these sources could be major inputs to the Arabian seas besides the autochthonous marine products. Future studies of the organic and inorganic biogeochemistry on river, dust, and coastal areas are needed to characterize the various regional sources, transformation, and diagenetic processes of the organic matter en route to the marine environment.

SIMSAFADIM-CLASTIC: A new approach to mathematical 3D forward simulation modelling for terrigenous and carbonate marine sedimentation

Most sedimentary modelling programs developed in recent years focus on either terrigenous or carbonate marine sedimentation. Nevertheless, only a few programs have attempted to consider mixed terrigenous-carbonate sedimentation, and most of these are two-dimensional, which is a major restriction since geological processes take place in 3D. This paper presents the basic concepts of a new 3D mathematical forward simulation model for clastic sediments, which was developed from SIMSAFADIM, a previous 3D carbonate sedimentation model. The new extended model, SIMSAFADIM-CLASTIC, simulates processes of autochthonous marine carbonate production and accumulation, together with clastic transport and sedimentation in three dimensions of both carbonate and terrigenous sediments. Other models and modelling strategies may also provide realistic and efficient tools for prediction of stratigraphic architecture and facies distribution of sedimentary deposits. However, SIMSAFADIM-CLASTIC becomes an innovative model that attempts to simulate different sediment types using a process-based approach, therefore being a useful tool for 3D prediction of stratigraphic architecture and facies distribution in sedimentary basins. This model is applied to the neogene Valles-Penedes half-graben (western Mediterranean, NE Spain) to show the capacity of the program when applied to a realistic geologic situation involving interactions between terrigenous clastics and carbonate sediments.

Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of Bay of Bengal

Actinomycetes population from continental slope sediment of the Bay of Bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 (May–June) and 2005 (July) respectively from 11 transects (each transect had ca. 200 m, 500 m, and 1 000 m depth stations). The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations (ANOVA two-way, P 0.05). Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.

Antagonistic interactions among marine bacteria impede the proliferation of Vibrio cholerae.

Changes in global climate have raised concerns about the emergence and resurgence of infectious diseases. Vibrio cholerae is a reemerging pathogen that proliferates and is transported on marine particles. Patterns of cholera outbreaks correlate with sea surface temperature increases, but the underlying mechanisms for rapid proliferation of V. cholerae during ocean warming events have yet to be fully elucidated. In this study, we tested the hypothesis that autochthonous marine bacteria impede the spread of V. cholerae in the marine environment. It was found that some marine bacteria are capable of inhibiting the growth of V. cholerae on surfaces and that bacterial isolates derived from pelagic particles show a greater frequency of V. cholerae inhibition than free-living bacteria. Vibrio cholerae was less susceptible to antagonism at higher temperatures, such as those measured during El Niño-Southern Oscilliation and monsoonal events. Using a model system employing green fluorescent protein-labeled bacteria, we found that marine bacteria can directly inhibit V. cholerae colonization of particles. The mechanism of inhibition in our model system was linked to the biosynthesis of andrimid, an antibacterial agent. Antibiotic production by the model antagonistic strain decreased at higher temperatures, thereby explaining the increased competitiveness of V. cholerae under warmer conditions. These findings suggest that bacterium-bacterium antagonism is a contributing mechanism in regulating the proliferation of V. cholerae on marine particles.

Author Index Vol. 79 (2002)

During the ARCTIC '91 expedition with RV Polarstern, numerous short (multicorer) and long cores (kastenlot cores), including surface sediments, were recovered along a transect crossing the eastern part of the Arctic Ocean. In this paper we present data on the concentration and distribution of short- (C17, C19) and long-chain (C27, C29, C31) n-alkanes as well as fatty acids (16:0, 16:1, 18:0, 18:1) in the surface sediments from this transect. These compounds, among others, have been used to distinguish between autochthonous marine organic matter and allochthonous terrigenous organic matter supply. Changes in short-chain n-alkane as well as fatty acid contents of the sediments allow us to distinguish between regions characterized by higher or lower marine productivity. Organic carbon contents of the surface sediments are generally high and vary between 0.3% and 2%. In general, the high organic carbon content of the sediments is derived from a high input of terrigenous organic matter. Marine productivity in the Arctic Ocean is mainly controlled by reduced sea-ice cover which allows a higher production rate of phytoplankton. Regions with a higher marine organic matter content are the area NW of Svalbard, the Yermak Plateau, a part of the Lomonosov Ridge and Makarov Basin, and the Morris Yesup Rise. The pattern of distribution of long-chain n-alkanes in Arctic Ocean surface sediments is mainly controlled by sea-ice and/or direct transport from the adjacent shelf areas, although dilution by turbidites influences the deep basins.

Mixed Siliciclastic-Skeletal Carbonate Lagoon Sediments from a High Volcanic Island, Viti Levu, Fiji, Southwest Pacific

Modern sedimentation in the Navua-Suva Lagoon, southeastern Viti Levu, Fiji, derives from both allochthonous siliciclastics and autochthonous marine carbonates. Sediments are characterized by a high insoluble load, small grain size, a wide range of textures, and a high degree of mixing. The distribution of the two facies (skeletal-dominated muddy sandy gravel and skeletalbearing very fine sand to mud) is controlled by both the shallow-marine carbonate sediment productivity and sediment supply and dispersal processes from siliciclastic point sources across a narrow lagoon. Mollusks and Halimeda dominate the gravel fraction of the skeletal grains. Sediment budget estimates indicate that 97% of the siliciclastic supply bypasses the lagoon. Some 0.2 Mt/yr is accumulating in the lagoon, not yet enough to inhibit potential carbonate production (~0.1 Mt/yr) by a interreefal benthos that is at least somewhat sediment-tolerant. Contemporary allochthonous siliciclastic and autochthonous skeletal carbonate sedimentation in the lagoon results in true syndepositional (in situ) mixing. The central high volcanic island mass in a tropical setting produces the geomorphological (high topographic relief, narrow shelf ), environmental (high rainfall), and ecological (shallow benthic area) conditions that lead to carbonate-siliciclastic mixing in lagoons along adjacent, mostly carbonate, coasts of oceanic islands, a high volcanic island mass effect. We propose that tropical in situ mixing of carbonate and siliciclastic sediments is more common in high volcanic island settings than previously appreciated. Such islands are thus excellent testing grounds for the study of carbonate-siliciclastic interactions. Their special characteristics highlight the need for better understanding of coastal physical processes of tropical Pacific high volcanic islands.

Silurian spores and cryptospores from the arisaig group, Nova Scotia, Canada

The Arisaig Group in northern mainland Nova Scotia has the most complete sequence of Silurian, fine grained, siliciclastic, near‐shore marine sediments in Western Avalonia. In this setting, the Arisaig Group received a nearly continuous supply of autochthonous marine and allochthonous nonmarine palynomorphs. One hundred and seventy‐seven samples, ranging in age from latest Ordovician?‐early Llandovery to Prídolí (Beechhill Cove to Stonehouse formations) yield the most diverse spore assemblage yet known from the Silurian of North America. This paper describes the spores and cryptospores and reexamines age relationships of the Arisaig Group, placing both within context of early land plant evolution. Thirty‐six species of spores and cryptospores were found in the Arisaig Group. Six new species are Ambitisporites marginatus sp. nov., A. capitaneus sp. nov., Scylaspora asperverruca sp. nov., Chelinospora textilis sp. nov., Hispanaediscus scabiosus sp. nov., and Hispanaediscus imbricatus sp. nov. A new genus, Vermiverruspora is created and the original description of Chelinospora Allen 1965 is resurrected. Six species of Chelinospora are reassigned to Vermiverruspora gen. nov. (C. paravermiculata Loboziak et al. 1988, C. vermiculata Chaloner & Streel 1968, C. Ivermiculata McGregor & Camfield 1976, C. retorrida Turnau 1986, C. rumneyi Burgess & Richardson 1995, C. vermoluta Burgess & Richardson 1995) and one species transferred to Stellatispora (pattersonii Wellman 1993). Four additional sporomorphs believed to be new, are not formally named because better preserved specimens are needed. The Arisaig Group (West Avalonia) is similar to sporomorphrich type sections in the Anglo‐Welsh Basin (East Avalonia). Four assemblage zones (avitus‐dilutus, brevicosta‐verrucatus, libycuspoecilomorphus, and tripapillatus‐spicula), and four assemblage sub‐zones (A. brevicosta, E. protophanus, C. obscura, and S. inframurinata var. inframurinata) have been recognized. Sporomorphs indicate that the contacts between the Lower and Upper Members of the McAdam Brook Formation and Green Member of the Moydart Formation may be one to two graptolite biozones older than previously reported. The Arisaig palynomorphs support the theory that a major radiation of vascular land plants occurred during the latter half of the Silurian Period. Llandovery and early Wenlock deposits at Arisaig contain only a few species of smooth walled spores and cryptospores. Sixteen trilete spore and fifteen cryptospore species appear between the Homerian and the late Prídolí. The tempo and composition of this diversification reflect evolutionary events observed elsewhere in the world.

Author Index Vol. 76 (2001)

During the ARCTIC '91 expedition with RV Polarstern, numerous short (multicorer) and long cores (kastenlot cores), including surface sediments, were recovered along a transect crossing the eastern part of the Arctic Ocean. In this paper we present data on the concentration and distribution of short- (C17, C19) and long-chain (C27, C29, C31) n-alkanes as well as fatty acids (16:0, 16:1, 18:0, 18:1) in the surface sediments from this transect. These compounds, among others, have been used to distinguish between autochthonous marine organic matter and allochthonous terrigenous organic matter supply. Changes in short-chain n-alkane as well as fatty acid contents of the sediments allow us to distinguish between regions characterized by higher or lower marine productivity. Organic carbon contents of the surface sediments are generally high and vary between 0.3% and 2%. In general, the high organic carbon content of the sediments is derived from a high input of terrigenous organic matter. Marine productivity in the Arctic Ocean is mainly controlled by reduced sea-ice cover which allows a higher production rate of phytoplankton. Regions with a higher marine organic matter content are the area NW of Svalbard, the Yermak Plateau, a part of the Lomonosov Ridge and Makarov Basin, and the Morris Yesup Rise. The pattern of distribution of long-chain n-alkanes in Arctic Ocean surface sediments is mainly controlled by sea-ice and/or direct transport from the adjacent shelf areas, although dilution by turbidites influences the deep basins.

SILURIAN SPORES AND CRYPTOSPORES FROM THE ARISAIG GROUP, NOVA SCOTIA, CANADA

Research Article| January 01, 2001 SILURIAN SPORES AND CRYPTOSPORES FROM THE ARISAIG GROUP, NOVA SCOTIA, CANADA JOHN H. BECK; JOHN H. BECK Weston Observatory Paleobotany Laboratory, 381 Concord Road, Weston, MA 02193, U.S.A. Search for other works by this author on: GSW Google Scholar PAUL K. STROTHER PAUL K. STROTHER Weston Observatory Paleobotany Laboratory, 381 Concord Road, Weston, MA 02193, U.S.A. Search for other works by this author on: GSW Google Scholar Palynology (2001) 25 (1): 127–177. https://doi.org/10.2113/0250127 Article history first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation JOHN H. BECK, PAUL K. STROTHER; SILURIAN SPORES AND CRYPTOSPORES FROM THE ARISAIG GROUP, NOVA SCOTIA, CANADA. Palynology 2001;; 25 (1): 127–177. doi: https://doi.org/10.2113/0250127 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyPalynology Search Advanced Search Abstract The Arisaig Group in northern mainland Nova Scotia has the most complete sequence of Silurian, fine grained, siliciclastic, near-shore marine sediments in Western Avalonia. In this setting, the Arisaig Group received a nearly continuous supply of autochthonous marine and allochthonous nonmarine palynomorphs. One hundred and seventy-seven samples, ranging in age from latest Ordovician?–early Llandovery to Přídolí (Beechhill Cove to Stonehouse formations) yield the most diverse spore assemblage yet known from the Silurian of North America. This paper describes the spores and cryptospores and reexamines age relationships of the Arisaig Group, placing both within context of early land plant evolution.Thirty-six species of spores and cryptospores were found in the Arisaig Group. Six new species are Ambitisporites marginatus sp. nov., A. capitaneus sp. nov., Scylaspora asperverruca sp. nov., Chelinospora textilis sp. nov., Hispanaediscus scabiosus sp. nov., and Hispanaediscus imbricatus sp. nov. A new genus, Vermiverruspora is created and the original description of ChelinosporaAllen 1965 is resurrected. Six species of Chelinospora are reassigned to Vermiverruspora gen. nov. (C. paravermiculata Loboziak et al. 1988, C. vermiculata Chaloner & Streel 1968, C. ?vermiculataMcGregor & Camfield 1976, C. retorrida Turnau 1986, C. rumneyiBurgess & Richardson 1995, C. vermolutaBurgess & Richardson 1995) and one species transferred to Stellatispora (pattersoniiWellman 1993). Four additional sporomorphs believed to be new, are not formally named because better preserved specimens are needed.The Arisaig Group (West Avalonia) is similar to sporomorph-rich type sections in the Anglo-Welsh Basin (East Avalonia). Four assemblage zones (avitus–dilutus, brevicosta–verrucatus, libycus–poecilomorphus, and tripapillatus–spicula), and four assemblage sub-zones (A. brevicosta, E. protophanus, C. obscura, and S. inframurinata var. inframurinata) have been recognized. Sporomorphs indicate that the contacts between the Lower and Upper Members of the McAdam Brook Formation and Green Member of the Moydart Formation may be one to two graptolite biozones older than previously reported.The Arisaig palynomorphs support the theory that a major radiation of vascular land plants occurred during the latter half of the Silurian Period. Llandovery and early Wenlock deposits at Arisaig contain only a few species of smooth walled spores and cryptospores. Sixteen trilete spore and fifteen cryptospore species appear between the Homerian and the late Přídolí. The tempo and composition of this diversification reflect evolutionary events observed elsewhere in the world. You do not currently have access to this article.

Identification of Culturable Oligotrophic Bacteria within Naturally Occurring Bacterioplankton Communities of the Ligurian Sea by 16S rRNA Sequencing and Probing.

> Abstract Typical marine bacteria (i.e., obligately oligotrophic) that were numerically dominant members of naturally occurring marine communities were identified by cloning and sequencing the amplified 16S rRNA genes obtained from dilution cultures of the original samples. The data reported here refer to two different habitats of a marine pelagic environment (28 miles offshore, in the northwestern Mediterranean Sea). The samples were taken from the water column at two representative layers, i.e., the 30-m depth, corresponding to the chlorophyll maximum layer, and the 1800-m depth, representative of a deep, oligotrophic environment. Three major lineages were found in the 16S rDNA clone libraries prepared from the two samples, two of which could be assigned to the Vibrio and the Rhodobacter groups. The third lineage was a distant relative of the genus Flavobacterium, but it was not closely related to any marine isolate. Six oligonucleotide probes, either complementary to the conserved sequence domains or selectively hybridizing to the clone sequences, were designed for use as hybridization group-specific and strain-specific probes. A single-mismatch discrimination between certain probes and nontarget sequences was demonstrated by detecting the probes' specificity at different hybridization and washing conditions. The screening of the clone libraries with the obtained probes revealed that neither the 30-m sample higher dilution nor the 1800-m one were pure cultures. While some representatives of the Vibrio group were found in both the surface and the deep sample, the members of the Flavobacterium and Rhodobacter lineages were detected only in the deep and the euphotic layers, respectively. We suggest an approach for analyzing autochthonous marine bacteria able to grow in unamended seawater.

Organic geochemical studies of sinking particulate material in China sea area II

We have for the first time studied the compositions of ketone, aldehyde and alcohol lipid compounds in sinking particulate materials from Yongshu Reef lagoon and the continental shelf of the East China Sea collected by sediment trap sampling apparatus. The results indicate that sinking particulate materials contain abundant isoprenoid ketone, aldehyde and alcohol lipid compounds which take part in marine chemical cycling. The compositional features of these compounds show that sinking particulate organic matter mainly comes from autochthonous marine organisms and Yongshu Reef lagoon has more submerged macrophytes-derived component, while the continental shelf of the East China Sea contains more dinoflagellate-derived constituent. The contribution of higher land plant to sinking particulate organic matter may be very small. In contrast, it is greater in Yongshu Reef lagoon than that in the continental shelf of the East China Sea. Sinking particulate organic matter in the two regions undergoes strong biochemical transformation processes before reaching the depth of 5 m to the sea floor, and its intensity is greater in Yongshu Reef lagoon than in the continental shelf of the East China Sea. These results have certain reference value to the researches of marine chemistry, marine biology and marine sedimentology in China, and reveal the importance of organic geochemistry to the study of oceanology.