Refugee communities of Carbonicola

Hardy, Peter G. & Broadhurst, Frederick M. 1978 04 IS: Refugee communities ofCarbonirola
Sparse elongate forms of the non-marine bivalve Carbonirola are associated with an abundance of trace fossils comprising resting traces (Cubichnia) referable to Lockeia , trails (Repichnia) and escape shafts (Fugichnia), all in arenaceous sediments of the Upper Carboniferous. Associated organic-rich argillaceous sediments contain the well-known, abundant and highly variable Carbonirola body fossil faunas. The latter we interpret (in common with other workers) as the remains of shells preserved in what was the typical life environment (characterized by muddy sediments and slow rates of sedimentation). The elongate shells associated with escape shafts we interpret as the only form of Carbonicola capable of escape upwards from burial by rapid sedimentation. For such fugitives from preexisting 'established communities' we propose the term 'refugee community'.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition,standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition, standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

Multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and Late Quaternary shelf sediments,northern Canada

Benthic foraminifera in surface sediments from northeastern Canada and the Beaufort Shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth, temperature and salinity. Factor analysis shows that 7 factor assemblages account for 92% of the variance between samples. Multiple linear regression shows that different factors are significantly related to water depth, August bottom water temperature or salinity. Multiple correlation coefficients for depth, temperature and salinity are 0.94, 0.72 and 0.92, respectively. Labrador fjords contain arenaceous faunas dominated by eitherSaccammina atlantica andReophax fusiformis or byEggerella advena. Regression analysis shows that theSaccammina-Reophax factor is most strongly related to salinity. TheEggerella factor is related to depth and temperature. A fauna dominated byTrochammina nana andBuliminella elegantissima is correlated with warm, deep water in Davis Strait. Calcareous assemblages dominated byElphidium excavatum orCassidulina reniforme are found in Arctic bays and shelf areas. These factor assemblages are strongly related to temperature and depth;Cassidulina is also related to salinity. AnIslandiella helenae fauna on the inner Labrador Shelf is strongly correlated with depth and salinity. ANonionellina labradorica fauna in deep shelf basins is closely related to salinity.The multiple regression model for the sea-bed data estimates water depth, August bottom water temperature and salinity within confidence limits of ± 67 m, 1.3°C and 1.0‰. Paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the Labrador Shelf. Paleo-depth estimates obtained from the core data produce relative sea-level curves which are similar in shape to theoretical curves for this region. Paleo-salinity and -temperature estimates for offshore Core 12 show that the change from a postglacialNonionellina fauna to a late glacialE. excavatum fauna is accompanied by a decrease of about 2‰ in salinity and 4°C in temperature. Paleoecological estimates for fjord Core 111 show that the change from a modernSaccammina-Reophax fauna to a mid-HoloceneI. helenae fauna corresponds to a salinity increase of 3–5‰ and temperature increase of 1–2°C.     

A quantitative method of palaeolake-level reconstruction using ostracod assemblages: an example from the Bolivian Altiplano

This paper provides quantitative information concerning the response of ostracods to environmental variability in order to reconstruct past environments. Ostracod faunas from modern sediments of Bolivian lakes and swamps were studied. Ostracod distribution is controlled by several ecological characteristics such as lake-level and water chemistry. Statistical results indicate that three transfer functions (on water depth, Total dissolved Salts and water in Mg/Ca ratio) can be developed, from ostracod species frequencies in lacustrine sediments, with some restrictions for the two last ones.     

Gastropoden aus dem oberen Toarcium/unteren Aalenium (Jura) von Norddeutschland

Borings from northeastern Germany yielded a gastropod fauna with 31 species from the Upper Toarcian and Lower Aalenian. Eight species have already been described, nine species are new and 14 species are described in open nomenclature. The fauna comes from soft-bottom sediments and is a typical offshore fauna (relatively great distance from the coast, relatively great depth). The fauna has close relationships to faunas of the same age in southern Germany (Franconia).     

Facies distribution patterns of some marine benthic faunas in early paleozoic platform environments

Worldwide Late Cambrian—Silurian lithofacies patterns indicate that the platforms of that time were sites of accumulation of two essentially different rocks suites: the platform carbonate rocks and the platform terrigenous rocks. Most of the platform rocks accumulated as sediments in shallow marine environments similar to those of the present but far more widely spread.Present-day marine benthic faunas are distributed in depth zones which are primarily controlled by temperature. Faunas tend to occur in substrate-related discrete clusters (communities) within each life zone; similar substrates in different depth zones commonly have different faunal associations. Individual phyletic stocks may encounter environmental optimum or near-optimum conditions in certain areas, that commonly are revealed by an abundance of species and individuals within species in each stock. Environmental optimum conditions depend upon availability of food that may be utilized, modes of feeding of the animals present, water motion, and substrate, among other factors. Organisms in past seas were distributed in patterns similar to those of the present.Carbonate platforms were particularly widespread during the latest Cambrian—Early Ordovician. Intertidal environments spread widely across those platforms during that time and characteristic faunal associations developed in them. Saukiid and related tribolites dominated latest Cambrian carbonate platform intertidal faunas. The Early Ordovician carbonate platform intertidal was dominated by archeogastropod-nautiloid cephalopod faunas. These animals were joined by tabulate corals and certain brachiopods during the latter part of the Ordovician and Silurian as prominent faunal elements in the carbonate platform intertidal—shallow subtidal. Cruziana and related trace fossils, bivalves, and certain tribolites (notably homalonotids and dalmanitids) dominated most terrigenous platform intertidal—shallow subtidal faunas of the Ordovician and Silurian.Articulate brachiopods (primarily orthoids, strophomenoids, and rhynchonelloids) appear to have been relatively prominent during the Early Ordovician in shallow subtidal environments on both carbonate and terrigenous platforms and to have spread down the bathymetric gradient into increasingly deeper subtidal areas of both platforms during the latter part of the Ordovician. Tribolites dominated faunas in relatively moderate to deep subtidal environments on both platforms during the early part of the Ordovician. They were gradually replaced by brachiopods in first the shallower, and later the deeper subtidal as dominant members of the faunas. Brachiopods (primarily pentameroids and spiriferoids) dominated nearly all Silurian warm-water subtidal environments from the shallow subtidal to the edges of the platforms.Platform uplifts in the Middle Ordovician and glacio-eustatic sea-level fluctuations in the Late Ordovician caused environmental changes across the platforms that were accompanied by marked replacements among marine benthic faunas in all environments. The distribution of Ordovician carbonate platforms and glacial deposits suggests that an Ordovician polar region may have been close to present-day equatorial Africa and that Ordovician warm temperate-tropical regions lay close to the present-day North Pole.     

Ecology of the Ogun River estuary,Nigeria

The distribution of benthonic communities (particularly Foraminifera) were studied from fourteen samples obtained from the Ogun River estuary and environs. Ten species of benthonic Foraminifera were identified; two of these constitute over 90% of the total foraminiferal population.Two broad biofacies are recognisable, namely the upper estuarine facies of Ammobaculites and the lower estuarine facies comprising arenaceous and calcereous forms with a preponderance of Ammonia beccarii (Linnaeus).Large populations of few species occur in the lower estuary, an area of weakly saline water with marked salinity fluctuations. The upper estuary on the other hand is sparsely populated and contains tests mainly of arenaeous Foraminifera. A few species are distinctive of particular facies but some are distributed throughout the estuary. Substrate is not a causal ecological factor, because sediments are similar in physical attributes throughout the estuary. Salinity and rate of sedimentation are among the more important factors affecting the distribution of all species. The low-energy nature of the environment is established by the abundance of faecal pellets and the fragility of the tests of the arenaceous Foraminifera.     

Cichlid species‐area relationships are shaped by adaptive radiations that scale with area

A positive relationship between species richness and island size is thought to emerge from an equilibrium between immigration and extinction rates, but the influence of species diversification on the form of this relationship is poorly understood. Here, we show that within‐lake adaptive radiation strongly modifies the species‐area relationship for African cichlid fishes. The total number of species derived from in situ speciation increases with lake size, resulting in faunas orders of magnitude higher in species richness than faunas assembled by immigration alone. Multivariate models provide evidence for added influence of lake depth on the species‐area relationship. Diversity of clades representing within‐lake radiations show responses to lake area, depth and energy consistent with limitation by these factors, suggesting that ecological factors influence the species richness of radiating clades within these ecosystems. Together, these processes produce lake fish faunas with highly variable composition, but with diversities that are well predicted by environmental variables.     

Late Mississippian to Early Pennsylvanian conodont biofacies in central Montana

Later Mississippian (upper Chesterian) to Early Pennsylvanian (lower Morrowan) conodont faunas were recovered from limestones and calcareous mudstones of the Alaska Bench Formation in central Montana. These faunas define four biofacies, each recognized by the dominance of a particular single element genus for which the biofacies is named. The Adetognathus biofacies represents lagoonal, tidal flat, and barrier sediments. The Declinognathodus/Idiognathoides biofacies represents a deposition in shallow, open marine, offshore conditions. The Rhachistognathus biofacies represents a transitional environment between restricted, intertidal environments and normal marine, offshore environments. The Neognathodus biofacies represents shallow-water bay or lagoonal deposition, where environmental controls have effectively excluded other conodont faunas. The investigation of conodont biofacies provides improved biostratigraphic and paleoenvironmental uses of conodonts.     

Late Carboniferous postglacial brachiopod faunas in the Southwestern Gondwana margin

The glaciomarine sediments related to the Late Paleozoic Ice Age (LPIA) have an excellent stratigraphic record in Argentina, particularly those associated to the Late Carboniferous glacial episode identified along the southwestern margin of South America: Bolivia (Tarija Basin), west central Argentina (Calingasta-Uspallata Basin) and Patagonia (Tepuel-Genoa basins). The aim of this contribution is mainly a biostratigraphy update of the carboniferous brachiopod faunas that occur in the earliest postglacial interval (late Serpukhovian–Bashkirian) in the west central Argentina (i.e., Levipustula and Aseptella-Tuberculatella/Rhipidomella-Micraphelia faunas) and its regional correlation with those equivalents in the nearby basins. Components of these faunas are recognized from the Bolivia to Argentine Patagonia and their compositional variations appear to be controlled principally by a paleolatitudinal factor. The affinities showed by the postglacial faunas of the Calingasta-Uspallata Basin and the faunal assemblages that integrate the Lanipustula and Tuberculatella biozones in Patagonia differ from the significant contrast proposed by other authors, based on the paleogeographical position of Patagonia in the Late Paleozoic. Paleoecological studies focused on the paleoenvironmental controls related with the glacial dynamic are suggested to understand the complex relationship between these postglacial faunas.     

Depth-related changes in the arctic epibenthic megafaunal assemblages of Kangerdlugssuaq, East Greenland

The effects of depth-related differences in environmental factors (pressure, hydrography, habitat and disturbance) on the benthic megafauna at the mouth of Kangerdlugssuaq Fjord in Arctic Greenland were investigated using a towed camera platform and autonomous underwater vehicle photographs. Large reductions in faunal density (60,132 to 1881 individuals ha^-1) and increases in diversity (H'=0.93-2.54), through increases in richness (ES₍₂₂₀₎=7.6-18.8) and reductions in dominance (Berger-Parker index=0.77-0.38) were found between 270 and 720 m water depth. Assemblages were separated into distinct shallow, intermediate and deep faunas by multivariate community analysis. In the shallower sites there were high levels of iceberg disturbance, directly reducing diversity as well as creating a complex, patchy environment inhabited by high densities of mobile suspension-feeding epifauna. In the deeper areas there was small-scale disturbance from the deposition of drop stones, but at a relatively low frequency and magnitude, which allowed increased species diversity. Proportions of deposit-feeding epifaunal and infaunal taxa rose with depth, as indicated by an increase with depth in faunal traces. Decreases in faunal density probably resulted from decreased food supply with depth.     

Diversity and structure of epifaunal communities on mollusc valves,Buzzards Bay,Massachusetts

The diversity, homogeneity and population structure of epifauna living on dead bivalve shells in a shallow marine bay are examined. Twenty-eight shells of Mercenaria mercenaria were artificially emplaced on each of three different sediment types in Buzzards Bay, Massachusetts, for one year. Living faunas (53,000 individuals assignable to 106 species) and preservable faunas (16,000 individuals assignable to 25 species) which colonized these shells are compared.Living epifaunas demonstrate a moderately good fit to the Preston truncated lognormal distribution but deviate consistently from the MacArthur broken-stick model. Homogeneity and diversity of living faunas are greater on shells resting on coarse sediments. The rarefaction methodology overestimates faunal diversity in both living and preservable faunas.Preservable epifaunas posses a higher homogeneity but one which is generally parallel to that of the living communities from which they are derived. The diversity of preservable epifaunas does not reflect the diversity of the living faunas from which they are derived.Abundant species living on shells are more likely to possess preservable hard parts than are rare species. This is indicative of the evolutionary success of various protective devices in epibenthic communities exposed to predation and environmental vagaries.     

北部湾中部海域底质沉积物中的有孔虫

本文对北部湾中部海域水深2.4m到61m、共计184个站位表层沉积物中的有孔虫进行研究。结果显示浮游有孔虫丰度非常低,种类也较稀少,仅在南侧水深较大的少数站位有发现,且含量不超过5%;而底栖有孔虫则较丰富,多数样品中以含有螺旋式与平旋式的玻璃质壳类型为主,暖水或大型底栖有孔虫分子常见。和其它海区相较而言,该海域底栖有孔虫中胶结壳类含量偏高,可能与沉积物底质颗粒较粗及海水盐度较低有关。该研究详细报道了底栖有孔虫主要属种在北部湾的分布特征。与海洋环境对比显示,水深和沉积物底质类型是影响这些属种平面分布的主要因素,而湾外温暖水团则是控制暖水种分子分布的另一重要因素。     

Graptolites from glacial erratics of the Laerheide area,northern Germany

Ordovician and Silurian glacial erratics of the Laerheide area (Lower Saxony, north-western Germany) bear well-preserved graptolites. The faunas provide important information on the origin and transport direction of the sediments preserved in a kame, representing the Drenthe stadial of the Saalian glaciation. The faunas even include species not commonly encountered in the successions of mainland Sweden, from where the erratics presumably originated. The most common graptolites are from Upper Ordovician (Sandbian to Katian) limestones and from Katian black shales. More common, however, are greenish limestones, sand- and siltstones, often combined in the term ‘Grünlich-Graues Graptolithengestein’, in which upper Wenlock to Ludlow (upper Silurian) graptolites are common.     

Radiolarian and sedimentologic paleoproductivity proxies in late Pleistocene sediments of the Benguela Upwelling System,ODP Site 1084

The changing composition of radiolarian faunas from late Neogene deep-sea sediments has been used in recent years as a proxy for changes in marine paleoproductivity. We examine radiolarian faunas, organic carbon content (TOC), opal and coarse-fraction components over the last 270,000 years in sediments from ODP Hole 1084A, drilled in a high productivity upwelling region within the Benguela Upwelling System off the west coast of Africa. Age control is provided by stable oxygen isotope measurements of benthic foraminifera. Prior research has established that late Pleistocene glacial intervals in this upwelling system generally had higher productivity than interglacials. The radiolarian WADE (water-depth ecology) paleoproductivity index correlates well with TOC and opal in these samples, and all three parameters change in synchrony with the benthic isotope curve over all but the MIS 5e–6 time interval. WADE inferred productivity is significantly higher in glacials than interglacials. We conclude that the WADE index is a useful proxy for paleoproductivity at this location, as are also opal and organic carbon accumulation rates. Carbonate and carbonate based indices such as the accumulation rate of benthic foraminifera (BFAR) by contrast do not correlate well either to productivity indices or to the glacial–interglacial cycle, and are interpreted to primarily reflect carbonate dissolution.     

Lower Devonian brachiopod communities of the northern Canadian Cordillera

The northern Canadian Cordillera can be divided into three more or less parallel arrayed lithofacies, which from east to west correspond to progrcssively deepening waters. The shallow water, yellow, or orange-weathering carbonates occupy essentially the eastern half of the region and northwestern Yukon. Shallowest water carbonates yield fairly abundant ostracodem faunas, ostracodes, and little else. Slightly deeper water carbonates contain brachiopod faunas rich in individuals but low in generic diversity. The name Howellella-Protathyris Community is applied to the Lower Lochkovian shallow water faunas: the Sieberella-Nymphorhynchia-Athyrhynchus Community is the approximate Upper Pragian-Zlichovian equivalent. Deep water calcareous shales and limestones occupy a narrow band and yield faunas rich both in number and diversity. These faunas are designated the Skenidioides-Spirigerina-Vagrania Community and are recognized through the entire Lower Devonian interval. An intermediate depth fauna from Upper Pragian and Zlichovian dark carbonates is probably recognizable in northwestern Yukon, and termed the Strophochonetes-Proreticularia- receptaculitid Community. The widespread deep water graptolitic shales and carbonates contain a rich fauna of graptolites and relatively rare trilobite, sponge, and brachiopod faunas.     

Foraminiferida from Neogene sediments,Vestfold Hills,Antarctica

Sediment samples from several locations in the southern part of the Vestfold Hills have been examined for their foraminiferid content. Those from Early Pliocene sediments of Marine Plain immediately east of Burton Lake contain little foraminiferid evidence of marine deposition. Those from mid-late Holocene sections in and near the lakes contain good open marine faunas of species now known to be living on the continental shelf west of Cape Darnley.Foraminiferid faunas characterized by calcareous forms are most common, the most prevalent dominated by Globocassidulina crassa.The faunas examined contrast markedly with those in the present Prydz Bay which is characterized by agglutinated forms.The results, in relation to planktonic faunas, conflict with an earlier record of a diverse fauna.     

Analysis of Bacterial Communities in Seagrass Bed Sediments by Double-Gradient Denaturing Gradient Gel Electrophoresis of PCR-Amplified 16S rRNA Genes

Bacterial communities associated with seagrass bed sediments are not well studied. The work presented here investigated several factors and their impact on bacterial community diversity, including the presence or absence of vegetation, depth into sediment, and season. Double-gradient denaturing gradient gel electrophoresis (DG-DGGE) was used to generate banding patterns from the amplification products of 16S rRNA genes in 1-cm sediment depth fractions. Bioinformatics software and other statistical analyses were used to generate similarity scores between sections. Jackknife analyses of these similarity coefficients were used to group banding patterns by depth into sediment, presence or absence of vegetation, and by season. The effects of season and vegetation were strong and consistent, leading to correct grouping of banding patterns. The effects of depth were not consistent enough to correctly group banding patterns using this technique. While it is not argued that bacterial communities in sediment are not influenced by depth in sediment, this study suggests that the differences are too fine and inconsistent to be resolved using 1-cm depth fractions and DG-DGGE. The effects of vegetation and season on bacterial communities in sediment were more consistent than the effects of depth in sediment, suggesting they exert stronger controls on microbial community structure.     

Biotic and abiotic interactions between surface and interstitial systems in rivers

Water chemistry and community assemblages of surface and interstitial invertebrates were studied at seven sues on the French Rivers Rhône and Am at surface and at 50 cm depth into the bed sediments Chemical factors allowed differentiation of surface water from groundwater and detection of water exchanges defining clear downwelling and upwelling zones At some sites, interstitial water showed both surface and phreatic conditions, characterizing the underflows of the Rhone or of the Am In the interstitial area, most taxa showed no significant correlations with water chemistry Some epigean and hypogean fauna showed correlations with certain factors Clear relationships appeared between the water exchanges and the distribution of surface and interstitial faunas In interstitial samples, epigean and some hypogean species characterized the downwelling zones while others seemed to be strictly linked to the upwelling zones In surface samples, the presence of hypogean species was associated with regions of groundwater upwelling