Biological Debris Research Articles

Palaeoenvironmental assessment of marine organic-rich sediments using molecular organic geochemistry

Summary The solvent extracts of contemporary aquatic sediments contain a complex assemblage of compounds derived from living organisms. Among such biological debris many lipid components occur which possess structural and stereochemical characteristics that attest their origin from terrigenous higher plants, unicellular algae such as diatoms and dinoflagellates, or bacteria, including methanogens. Such compounds are markers of the organisms contributing to a given environment, and can provide information not available from micropalaeontological studies, namely evidence of bacterial activity, contributions from calcareous algae to sediments deposited below the calcite compensation depth and possibly sediment inputs from coccolithophorids in their non-coccolith bearing growth stage. In certain circumstances, especially in sedimentary sequences not subjected to elevated temperatures, many source-specific compounds can survive unaltered and thus are found in Mesozoic marine sediments deposited over 165 million years ago. In such immature ancient sediments, unaltered lipids occur together with their early stage diagenetic products, many of which retain molecular features that reflect their biological origins and are therefore also of value as source indicators. As diagenesis proceeds to catagenesis and kerogen breakdown increases, part of the molecular information is gradually lost as defunctionalization occurs and aliphatic and aromatic hydrocarbons come to dominate the sedimentary lipid distributions. Hence, attempts to identify the detailed sources of sedimentary organic matter from geolipid distributions become more difficult and rely more heavily on the occurrence of particular biologically-specific skeletons (e.g. head-to-head isoprenoids). The recognition of the diagenetic products of biolipids does, however, provide the basis for understanding lipid diagenetic pathways and offers the possibility of extending the scope of molecular assessment of sediment inputs to older and more thermally mature sediments. Despite these limitations imposed by the processes of sediment diagenesis and catagenesis, molecular organic geochemistry provides a unique record of past and present environments, with the potential of evaluating both biological inputs and subsequent sedimentary processes.

Influence of contamination on the analysis of precipitation samples

Liquid precipitation samples, collected in a standard open gauge, are often contaminated by biological debris, which can give rise to unusually high ammonium ion concentrations. In order to prevent this kind of contamination a 1-mm fibreglass teflon coated grid was mounted in the neck of the collection bottle. Collection characteristics of this gauge were compared with a standard open gauge by a parallel sampling of precipitation in the two gauges. 34 parallel samples were collected during 6 months (May–October. 1979) in a rural area. The results indicate that biological contamination has no effect on the concentration of chloride, nitrate, and sulphate ion in the liquid precipitation samples. As expected, biological contamination has a very strong influence on concentrations of ammonium ion, strong acid, and on pH.

Intraoral Adhesion to a Well Defined Surface

One male subject was used as test person in an in vivo-study of oral films formed on well defined germanium prisms under unprovoked oral conditions as well as in the presence of sucrose or blood. The following analytical techniques were performed on the adsorbed films: a. internal reflection infrared spectroscopy, b. ellipsometry, c. scanning electron microscopy and d. energy-dispersive x-ray analysis.The results show that in the created moderately stagnated intraoral system the formation of biological films was similar in different parts of the oral cavity. The process was not found to be markedly influenced by the presence of blood. Sucrose, on the other hand, was found to increase both the overall film thickness and the carbohydrate-content of the films.The attachment of microorganisms was found to be a process proceeding at a comparatively slow rate especially in the presence of sucrose and when compared with biological debris. The majority of the first adhering microorganisms were found to be rod-shaped.

Microorganisms and Interfaces

Microorganisms are, by definition, the smallest of all living organisms, yet they play a dominant role in primary productivity in aquatic systems, in decomposition of waste organic materials, and in biogeochemical transformations of mineral elements in both terrestrial and aquatic systems (Alexander 1971). All microorganisms are dependent upon inorganic nutrients and, in the case of heterotrophs, organic nutrients for satisfactory growth and metabolism. Some natural microbial habitats are characterized by a relatively constant input of nutrients, which sustain a high level of microbial activity; but many habitats receive only spasmodic or chronically low nutrient inputs, resulting in relatively low microbial activity. Such habitats include many soils, the open oceans, and oligotrophic lakes and streams. The majority of microorganisms require an aqueous environment for growth. Where the aqueous phase is nutrient-deficient, substantial microbial activity usually is encountered only at interfaces in the system. Interfaces are boundaries between any two phases in a heterogeneous system and possessing physicochemical properties that differ from those of either phase. Natural microbial habitats are heterogeneous systems containing a wide range of solid-liquid, gas-liquid, liquid-liquid, and, occasionally, solid-gas interfaces. Such interfaces serve as sites of nutrient accumulation in the form of lipids, macromolecules, other organic molecules, and inorganic nutrients. Microorganisms tend to accumulate at solidliquid interfaces (Stark et al. 1938, ZoBell and Anderson 1936) and gas-liquid interfaces (Parker and Barsom 1970). They achieve substantial growth at these interfaces even in highly oligotrophic conditions. The interfaces can be regarded as sites of escape from the nutrient-deficient aqueous phase; thus, all interfaces exert a potential influence on microbial distribution, growth, metabolism, and succession in such habitats. The solid phases found in nature include large surfaces, such as rocks, ship hulls, plants, and animals, as well as small surfaces, such as clay particles, plankton, and biological debris suspended in the aqueous phase. The major gas phase is air at the surface of large water bodies, but this phase also may consist of H2, CO2, CH4, and H2S in anaerobic sediments and soils, as well as in gas bubbles originating from sediments. The most obvious liquid-liquid interface is that encountered following an oil spill in oceans and estuaries, where the oil phase overlies the aqueous phase. Although interfaces provide an advantageous situation with respect to the growth of microorganisms, there are instances where microbial activity at such sites is of nuisance value to man. Microbial growth on the inside of pipelines and on ship surfaces, for example, increases surface roughness and thus creates greater fluid frictional resistance; microbial growth on heat transfer surfaces has an insulating effect that alters the heat transfer characteristics of the system (Characklis 1980). A study of microorganisms and interfaces, then, must consider the modes of transport of the organisms to interfaces and the physicochemical factors involved in interactions between the microorganisms and the interfaces. Recent research has concentrated mainly on the behavior of bacteria at interfaces, because bacteria colonize interfaces very rapidly. The smallest of all living organisms (most range from 0.5 to 2.0 /tm in length), bacteria possess a net negative surface charge and tend to behave as colloidal particles in an aqueous phase. Critical studies of both the biological and colloidal properties of bacteria (Marshall 1976) have substantially expanded the information on bacteria at interfaces. The surface charge properties of bacteria may be altered by lowering the pH of the aqueous phase or by adding polyvalent cations (Santoro and Stotzky 1967), as well as by adsorption of organic materials to the bacterial surface (Neihof and Loeb 1974).

Geochemistry of oceanic ferromanganese deposits

Deposits of mixed manganese and iron oxides, with high concentrations of minor metals, cover large areas of the deep-sea floor. They occur as nodules , over a very wide depth range, but most abundantly on the abyssal sea floor in water depths between 4 and 5 km, and as unconsolidated sediments , rocks and crusts , which are restricted to areas of the world-wide active ridge system. The two types of deposit have different chemical compositions and are the products of different precipitation and accretion mechanisms on the abyssal sea floor. Ferromanganese nodules grow very slowly, they generally have Mn/Fe ratios greater than or equal to 1, and they contain high levels of Ni, Cu, Co, Ba, Pb, Zn and Mo. Regional, inter- and intra-ocean variations in composition are marked. Such variations can be easily mapped throughout the Pacific and are most plausibly explained by a combination of the variety of metal sources on the sea floor (including abyssal water, biological debris and perhaps volcanism), and by the different environmental conditions under which the nodules form. Some of the vai lability in the contents of Ni and Cu, two of the metals for which the nodules are considered a valuable resource, can be interpreted as a reflection of intensive metal recycling and diagenetic reaction at the sediment surface. Iron- and manganese-rich sediments, rocks and crusts accumulate quite rapidly, they have highly variable Mn/Fe ratios, and they contain a different suite of minor metals, generally at lower concentrations, compared with ferromanganese nodules. Compositional variations in this case are on the scale of an individual specimen as well as regional, although clear trends are not evident at the present time. They are thought to form by precipitation from the reaction products of newly extruded basalt and seawater; isotopic evidence also indicates that there is significant adsorption of metals from seawater by the poorly crystalline oxides produced by this reaction.