327 Glossary, acronyms and abbreviations dating: Method of absolute age determination based on the decay of radioactive lead-210, which is formed in the atmosphere. It rapidly attaches itself to aerosol par- ticles, and settles to the Earth’s surface. Lead-210 activity in lake sediments provides an indication of their age for the last ~ 150 years. absorption maximum: Wavelength at which light is absorbed most intensely; used for pigment identification. acarid mite: Mite in the suborder Acariformes, subgroup Oribatei, within the order Acari of the Arachnida. The chitinous bodies of free-living terrestrial and aquatic species are found in lake and bog sediments. acetylation: Chemical process to convert a primary or secondary hydroxyl group to an ester by addition of acetate. acid neutralizing capacity: The capability of natural waters to resist the influence of added acids; specifically measured as the amount of a strong acid that is necessary to reduce the pH of a water sample to a specific point. acrostom: A term to describe the apertural morphology of testate amoebae. In an acrostom test, the aperture is terminal. adnate: Used to describe a diatom whose valve face is attached to the host substrate. agglutinate: Stick together. agglutinated shells: Shells of testate amoebae made from mineral particles or diatoms, which are glued together by an organic cement. akinetes: Asexual spores (resting cells) which form through thickening of the walls of a normal vegetative cell. algae: Plant-like organisms of any of several phyla, divisions, or classes of chiefly aquatic, usually chlorophyll-containing, nonvascular organisms of polyphyletic origin. They usually include the green, yellow-green, brown, and red algae in the eukaryotes and the blue-green algae in the prokaryotes. Allerød: Warm interstadial period that occurred at the close of the Weichselian (or latest) Glacial Stage in Europe, approximately 11,800 to 11,000 years before present (about 12,700–13,900 calibrated yr B.P.). Allerød-Younger Dryas transition: The period in geological time (ca. 12,900–12,700 calibrated years BP) between the mild Allerød period and the cold Younger Dryas pe- riod. allochthonous: From elsewhere, as opposed to autochthionous (produced in situ). Used, for example, for organic matter that may be imported from elsewhere, or for organisms. 328 allomer: Organic compounds sharing the same empirical formula. amoeba: Unicellular naked protozoan, typically of indefinite shape, moving and feeding with pseudopodia. The several groups of amoebae are not closely related to each other. amorphous silica: A non-crystalline isotropic mineral It is often found in the siliceous skeletons of various aquatic organisms, including diatoms. It can also be found in phytoliths and inorganically precipitated in highly alkaline lakes. AMS: Accelerator mass spectrometry. AMS dating: Method of absolute age determination based on the radioactive decay of the carbon-14 isotope in organic material; method can use accelerator mass spec- trometry, which allows the dating of 1–2 mg of carbon. Method can cover the last ~50,000 years. analyte: A compound being analyzed. anemophilous pollen dispersal: Pollen dispersal by wind. Plants adapted for this gener- ally produce large amounts of pollen, and these pollen types are dominant in pollen assemblages in lake sediments. Trees such as Betula, Pinus, Alnus, Corylus, and Quercus are anemophilous, and the most common herb types are grasses (Gramineae or Poaceae), sedges (Cyperaceae), Chenopodiaceae, Artemisia, and Plantago. anemophilous: Pollinated by wind-dispersed pollen. angiosperm: A subdivision of seed plants that includes flowering plants. Features used to separate angiosperms from other seed plants include the enclosed nature of the ovary (the carpel), the presence of flowers, specialised conducting cells in the xylem and phloem, ovules that are surrounded by a double-layered seed coat, and the structure of the pollen grain. annual laminations: In undisturbed conditions at the sediment surface (e.g., in a meromic- tic lake) sediment components that are deposited at different times of the year may lead to the formation of discrete layers. If the components are visibly different, one year’s deposition often consists of a couplet of a light and dark layer. annulus of cyst: Shelf of silica between the inner and outer pore margin of a chrysophyte cyst. anterior lip: Front lip of the aperture of a test of testate amoebae. anther: The terminal part of a flower’s stamen-bearing pollen sacs that contain pollen. apertural: Near an opening; for example, in testate amoeba, apertural plates are those near the opening of the test. aphotic: Without light, or sufficient light for a given process (e.g., photosynthesis). apical: Belonging to the apex; situated at the tip. 329 aplanospores: Spores formed directly from the contents of separate vegetative cells when the protoplast contracts and a new cell wall is formed inside the enclosing vegetative cell wall. aquatic succession: (= hydrosere). Plant succession from colonisation of open-water habitats, through various aquatic plant assemblages, leading to fen communities as the water becomes shallower, and then to either bog or woodland development above the water table. Evidence of the succession is preserved in the sediments below it. Many factors affect aquatic successions, and the directions of development can be diverse, and even retrogressive. arcellaceans: Testate amoebae belonging to the order Arcellinida. arctic tree-line: The northward limit of tree occurrence in the northern hemisphere; the northern limit of the tree growth-form. Beyond is usually shrub-tundra (low-arctic vegetation). areola: Simple or chambered pore-like perforation through the diatom wall. areolate surface: Shell surface of Arcella species (testate amoebae) with a honeycomb structure generated by the regular arrangement of small organic building units. Ascomycetes: Class of higher fungi with septate hyphae and spores formed in an ascus. ascospores: Spores produced in the ascus of an Ascomycete. ascus: The membranous oval or tubular spore case of an Ascomycete. athalassic waters: Inland or continental saline water bodies (cf. thalassic). atmospheric pressure chemical ionization: Process of production of mass ions using chemical means at atmospheric pressure in an inert gas, rather than in a vacuum, or by using high-energy molecular collisions. autecology: That division of ecology which treats the relations of a single species to its environment. autochthonous: From within, as opposed to allochthonous, which is material from else- where. Used, for example, to describe material, such as algal cells, which are produced within a lake basin. autotrophy: Self-nourishing; ability to feed on simple substances. azeotropic distillation: Method to remove small amounts of water. Small volumes of benzene are added to methanolic solutions containing water and subject to a mild vacuum. Water is evaporated in conjunction with the benzene by rotating the solution, often with mild external warming, under vacuum. background charcoal component: Slowly varying component of a charcoal record, which may reflect changes in fuel accumulation and its influence on charcoal production over long time periods. 330 baculate spines: Cylindrical spines with a blunt apex on chrysophyte cysts. bathochromatic: Towards longer wavelengths (e.g., red, infrared). benthic: Living attached to or associated with a substrate. Beringia: The unglaciated lands of eastern Siberia, Alaska, and western Yukon and the intervening continental shelves comprise Beringia. During the glacial periods of low- ered sea-level, the Bering and Chukchi seas were dry land, known as the Bering Land Bridge, that allowed the intercontinental migration of plants, animals, and people. bilobate: A type of two-lobed phytolith found only in grasses. They are also commonly referred to in the literature as dumbbells. binary solvent system: Chromatographic system in which two solvents or mixtures of differing polarity are used sequentially to elute compounds from a chromatographic substrate. biogenic silica (BSi): An amorphous form of Si biogenically precipitated by a variety of or- ganisms including chrysophytes, diatoms, radiolarians, silicoflagellates, and sponges. In most sedimentary environments diatoms are the major contributor to the biogenic silica measured in the sediments. biogeographic indicator taxa: Taxa with a restricted geographical distribution (e.g., Gondwanaland species). biome: A geographic zone characterized by similar animal and plant life. biotope: An area, usually of uniform environmental conditions, where a characteristic assemblage of organisms lives. bioturbation: Mixing of sediments by animal activity. blue-green algae: See Cyanobacteria. bog: Wetland environment often with large peat deposits. Raised bogs have an elevated central part and are usually dominated by Sphagnum. Blanket bogs cover flat or gently sloping areas in upland areas with a highly oceanic climate. Both types are usually fed by rainwater exclusively. bootstrapping: A computer intensive procedure to estimate parameters or derive confi- dence intervals by resampling the original sample with replacement. Boreal: An interval in Holocene time, from 10,500 to 7800 calibrated years BP, with a relative warm and dry climate. BP: Before Present (AD 1950). brackish water: Water with a salinity between that of freshwater and seawater (approxi- mately between 3 and ). 331 bright field microscopy: Standard compound