Benthische Foraminiferen auf dem Island-Schottland Rücken: Umwelt-Anzeiger an der Grenze zweier ozeanischer Räume

Surface sediment samples taken by box corer from 32 stations on the Iceland-Scotland Ridge have been investigated for their benthic foraminiferal content. The live (Rose Bengal stained) benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage. Principal component analysis of both the live and dead faunal data from the Iceland-Scotland Ridge reveals eight live species assemblages and six corresponding dead assemblages. Bottom water current conditions, surface sediment characteristics, particulate organic matter supply, and to some extent also the bottom water temperatures are the main factors limiting and governing the composition and distribution of live benthic foraminiferal species assemblages on the Iceland-Scotland Ridge. On the Atlantic slope of the Iceland-Scotland Ridge the dead species assemblages differ greatly from the foraminiferal fauna living there today due to winnowing processes and redeposition of Pleistocene sediments. In this area an investigation of distribution patterns of the empty tests only would lead to wrong results concerning ecologic interrelations between benthic foraminiferal species assemblages and their environment.     

Main features of foraminiferal distribution reflecting estuarine hydrography in Oslo Fjord

Foraminiferal assemblages have been analysed in sediment surface samples located along three profiles covering the depth interval 1–120 m in Breidangen, a wide basin forming the middle portion of Oslo Fjord. The study concentrates on the distribution of major faunal features, including suborders and diversities (number of species, Shannon-Wiener index, equitability). In addition, species distribution is recorded and Q-mode factor analysis has distinguished six assemblages. Measurements of hydrographical properties (temperature, salinity, dissolved oxygen) reveal the estuarine stratification of the water column, which is reflected also by the faunal parameters. On the basis of these features, the following subdivision is proposed (with increasing depth):(1) Seasonal layer dominated by calcareous species in the upper, and agglutinated species in the lower part, with low to intermediate diversities; (2) Transitional layer characterized by a maximum in diversity and a reduction in the agglutinated component; (3) Stable deeper water showing high diversity and a further decrease in the agglutinated component.The generally higher frequency of calcareous foraminifera below the seasonal water layer on the eastern side of Breidangen compared to the western side is mainly attributed to the influence of inflowing Skagerrak water. Additionally, it may be a result of increased supply of organic matter to the western side, increasing the oxygen demand in this area.     

The distribution of living benthic foraminifera on the continental slope and rise off southwest Norway

Surface sediment samples taken by ? corer from 45 stations on the Norwegian continental margin and in the Norway Basin have been investigated for their benthic foraminiferal content. Unlike previous studies, the living benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage. Factor analysis of both the living and dead faunal data reveals six living species assemblages and five corresponding dead assemblages. The additional living assemblage is characterized by the arenaceous speciesCribrostomoides subglobosum that dominates between 1400 and 2000 m water depth, but is rare in the dead faunal data.Trifarina angulosa and, to a lesser extent,Cibicides lobatulus characterize the shallowest foraminiferal assemblage from 200 to 600 m water depth, where it is associated with strong bottom currents and warm, saline Atlantic water of the North Atlantic Drift. On the slope between 600 and 1200 m water depth, theMelonis zaandami Species Assemblage dominates, particularly in areas characterized today by rapid sedimentation of terrigeneous material. Between 1000 and 1400 m depth, where the slope is covered by fine grained, organic-rich, terrigeneous mud, the living foraminiferal assemblage is characterized byCassidulina teretis andPullenia bulloides. Below 1400 m, three foraminiferal assemblages are found:C. subglobosum is found from 1400 to 2000 m,Cibicidoides wuellerstorfi andEpistominella exigua predominantly live from 2000 to 3000 m water depth, and below 3000 m,Oridorsalis umbonatus andTriloculina frigida dominate the fauna.All of theElphidium excavatum tests found in this study and theCassidulina reniforme tests found above 500 m water depth were found to be reworked.Analysis of the sediment grain-size distribution and the organic carbon content in surface samples from the deepest stations suggest that the abundance ofC. wuellerstorfi andE. exigua is positively correlated to relatively coarse (caused by planktic foraminifera) and organic-rich sediments, whereas high frequencies ofO. umbonatus andT. frigida coincide with low organic carbon content. We suggest thatC. wuellerstorfi is adapted to deep-sea environments with relatively high food supply, tolerating relatively low interstitial water oxygen content, whereasO. umbonatus may tolerate lower food supply prefering well-oxygenated interstitial waters.     

Foraminiferal distribution on the continental margin off Nova Scotia

Q-mode factor analysis of total foraminiferal abundance data (living plus dead) from 250 grab samples taken from the continental margin off Nova Scotia allows the determination of eight factor assemblages. On the northeastern shelf, an exclusively agglutinated assemblage dominated byAdercotryma glomerata occupies both banks and basins. Central shelf basins contain a predominantly calcareous assemblage dominated byGlobobulimina auriculata andNonionellina labradorica. Transitional between these two factor assemblages is an agglutinated assemblage dominated bySaccammina atlantica. Consistently present along the shelf edge is aTrifarina angulosa assemblage. In northeastern bays and a few samples near Sable Island, an agglutinatedEggerella advena assemblage is found. A relict and transport affected assemblage dominated byElphidium excavatum occurs in the southwestern approaches to Emerald Basin. Sandy/gravelly areas of the inner shelf and outer bank regions are characterized by aCibicides lobatulus assemblage.The statistical relationships of these defined assemblages to various aspects of the marine environment (depth, temperature, salinity, percent gravel, sand and mud) were investigated through multiple regression techniques. Results indicate that the present foraminiferal distribution patterns off Nova Scotia are influenced by the prevailing watermass characters and substrate. TheAdercotryma glomerata assemblage is influenced by the presence of cold, (0–4°C) low salinity waters (32–33‰) of arctic, Labrador Current origin. The central basin assemblage (G. auriculata) is related to warmer (8–12°C) more saline waters (35‰) of slope origin. The transition between these two bottom waters is marked by the opportunisticSaccammina atlantica assemblage. Preferred substrate character possibly determines the occurrence of theCibicides lobatulus, Islandiella islandica andEggerella advena assemblages.Trifarina angulosa shows a significant relationship to salinity and depth.Although the surficial sediments on the Nova Scotian Shelf are largely the product of reworking of glacial deposits during late glacial and early Holocene times, all but theE. excavatum factor assemblage appear to be in equilibrium with the modern oceanographic regime.     

Living foraminifera and total populations in salt marsh peat cores: Kelsey Marsh (Clinton, CT) and the Great Marshes (Barnstable, MA)

Common species of intertidal agglutinated benthic foraminifera in salt marshes in Massachusetts and Connecticut live predominantly at the marsh surface and in the topmost sediment (0–2.5 cm), but a considerable part of the fauna lives at depths of 2.5–15 cm. Few specimens are alive at depths of 15–25 cm, with rare individuals alive between 25–50 cm in the sediments. Specimens living between the sediment surface and 25 cm deep occur in all marsh settings, whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh, and have an irregular distribution-with-depth. Lower and middle marsh areas are bioturbated by metazoa, suggesting that living specimens reach these depths at least in part by bioturbation. High-marsh sediments in New England consist of very dense mats of Spartina patents or Distichlis spicata roots and are not bioturbated by metazoa. In this marsh region bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment. The depth-distribution of living specimens varies with species: living specimens of Trochammina inflata consistently occur at the deepest levels. This suggests that species have differential rates of survival in the sediment, possibly because of differential adaptation to severe dysoxia to anoxia, or because of differing food preferences. There is no simple correlation between depth-in-core and faunal diversity, absolute abundance, and species composition of the assemblages. It is therefore possible to derive a signal of faunal changes and thus the environmental changes that may have caused them from the complex faunal signal of fossil assemblages.     

Distribution of recent planktonic foraminifera in surface sediments of the Mediterranean Sea

The Mediterranean Sea is a partillay isolated ocean where excess evaporation over precipitation results in large east to west gradients in temperature and salinity. Recent planktonic foraminiferal distributions have been examined in 66 surface sediment samples from the Mediterranean Sea. In addition to mapping the frequency distribution of 16 species, the faunal data has been subjected to cluster analysis, factor analysis and species diversity analysis. The clustering of species yields assemblages that are clearly temperature related. A warm assemblage contains both tropical and subtropical elements, while the cool assemblage can be subdivided into cool-subtropical, transitional and polar-subpolar groupings. Factor analysis is used to delineate the geographic distribution of four faunal assemblages. Factor 1 is a tropical-subtropical assemblage dominated by Globigerinoiden ruber. It has its highest values in the warmer eastern basin. Transitional species (Globorotalia inflata and Globigerina bulloides) dominate factor 2 with highest values occurring in the cooler western basin. Factor 3 reflects the distribution of Neogloboquadrina dutertrei and is considered to be salinity dependent. Subpolar species dominate factor 4 (Neoglobuquadrina pachyderma and G. bulloides), with highest values occurring in the northern part of the western basin where cold bottom water is presently being formed. The Shannon-Weiner index of species diversity shows that high diversity exists over much of the western basin and immediately east of the Strait of Sicily. This region is marked by equitable environmental conditions and relatively even distribution of individuals among the species. Conversely, in areas where temperature and salinity values are more extreme, diversity values are lower and the assemblages are dominated by one or two species.     

Occurrence of viral haemorrhagic septicaemia virus (VHSV) in wild marine fish species in the coastal regions of Norway

This study was aimed at determining the occurrence of viral haemorrhagic septicaemia virus (VHSV) in selected stocks of wild fish species in the coastal regions of Norway. Six cruises were undertaken covering areas which included the coastal regions of northern Norway, the Norwegian Sea, the Barents Sea, and the Skagerrak area down to the Danish border. Collected, pooled samples of internal organs (kidney, spleen and heart) from 8395 fish were examined for the presence of VHSV by inoculation on BF-2 cells. Identification of virus was performed by a standard ELISA procedure with monoclonal antibody IP5B11, which is specific for the VHSV nucleocapsid protein (N-protein). VHSV was isolated from blue whiting and Norway pout in Skagerrak. No positive samples were detected in the northern coastal regions of Norway, the Norwegian Sea, or the Barents Sea. The findings indicate a very low occurrence of VHSV in the coastal regions of Norway. Geographically, the only positive samples were obtained from fish collected in areas where VHSV has previously been found in different species of fish.     

The spatial scale of homogenisation and differentiation in Chihuahuan Desert fish assemblages

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Effects of carbon dioxide sequestration on California margin deep-sea foraminiferal assemblages

Deep-sea sequestration of CO₂ is being considered as a possible mitigation tool to decrease atmospheric CO₂ concentrations and its associated negative effects. This study investigated potential effects of liquid carbon dioxide (CO₂) injection on deep-sea foraminiferal assemblages. Foraminifera are ideal for this ecological impact investigation because of differing test composition (calcareous and non-calcareous) and thickness, and diverse epifaunal and infaunal depth preferences. The experiment was conducted on August–September 2003, at 3600 m off the coast of Monterey Bay, California, aboard the R/V Western Flyer using the ROV Tiburon. The pH of the site was monitored throughout the experiment. Sediment push-cores were collected (both from the experimental and control sites) and stained to distinguish live (stained) from dead (unstained) individuals. Effects of CO₂ injection on assemblages have been tracked both vertically (to 10 cm depth below sea floor) and horizontally (up to 10 m from CO₂ injection sites), as well as between live and dead individuals. Within corrals (containing the injected CO₂) and their underlying sediments, severe pH changes (near 4.0 units) were recorded. This compares with a record of small average reductions in ocean pH (− 0.05 units) combined with large episodic excursions (− 1.7 units) over the experimental area due to the injection of CO₂. Exposure to this gradient of low pH caused increased mortality and dissolution of calcareous forms within corrals, as far as 5 m from the injection site, and to at least 10 cm depth in the sediments.This experiment revealed several major effects of CO₂ injection on foraminiferal assemblages in surficial sediments: 1) total number of foraminifera in a sample decreases; 2) foraminiferal species richness decreases in both stained and unstained specimens; and 3) relative percentage of stained (live) forms in the remaining tests increases. Down-core trends (to 10 cm below sea floor) have revealed: 1) percent agglutinated forms decline and calcareous forms increase with depth; 2) agglutinated species richness decreases with depth; and 3) experimental core assemblages become increasingly similar with depth to those in control cores not subjected to CO₂ injection. These results imply almost complete initial mortality and dissolution in the upper 10 cm throughout the corrals following liquid CO₂ injection. Since calcareous foraminifera represent more than 50% of the total assemblages, this clearly indicates that emplacement of CO₂ will result in negative effects to diversity and survivorship of the deep-sea benthic meiofauna.     

Benthic foraminiferal responses to absence of fresh phytodetritus: A two-year experiment

Sediment and bottom water from 320 m water depth in the Skagerrak basin (NE North Sea) was maintained in the laboratory and kept unfed in the dark, at ambient temperature, for two years. Although the relative abundance of agglutinated taxa in the sediments increased at the expense of allogromiids and calcareous forms, the deprivation of fresh phytodetritus caused only a moderate change of the faunal composition of the bathyal, benthic foraminiferal assemblage (six of the seven most abundant species were the same before and after the treatment; overall similarity was 58%). Among the most common species, the halt in supply of fresh organic material promoted population growth in some (e.g., Textularia earlandi, Leptohalysis gracilis, Melonis barleeanum), some maintained their populations (e.g., Globobulimina auriculata, Liebusella goësi, Eggerelloides medius), while others (e.g., Nonionella iridea, Cassidulina laevigata, and some allogromiids, particularly Micrometula hyalostriata) nearly disappeared. The different responses probably reflect the species' relative dependence on fresh phytodetritus. Those species which could utilize food stored or produced in the sediments (e.g., bacteria and degradation products) increased or maintained their populations, whereas those dependent on fresh phytodetritus and/or associated early-decomposition products declined. In spite of these changes, the species diversity showed only a minor reduction. The overall moderate response to lack of fresh phytodetritus was probably due to the fact that the assemblage already was adapted to an environment dominated by poor quality food particles. The study illustrates that the quality of organic material has an important impact on the composition and maintenance of some benthic foraminiferal communities, that the faunal response to reduction, or even a halt, in the supply of fresh phytodetritus, is not necessarily immediate or dramatic, and that the response depends on the trophic conditions prevailing in the area when the halt occurs.     

Recent benthic foraminiferal assemblages in deep high-energy environments from the Gulf of Cadiz (Spain)

The benthic environment in the Gulf of Cadiz, north-eastern Atlantic, is strongly affected by the Mediterranean outflow water undercurrent (MOW) which flows northwards along the western Iberian Margin at 500–1500 m water depth. Foraminiferal census counts of living and dead assemblages from 27 surface samples ranging from 103 to 1917 m water depth, and the examination of hard substrates reveal a close correlation of the fauna with the local hydrography and sediment facies. Four different faunal groups are separated by factor analysis of the living fauna. Assemblage 1 contains typical lower slope species and dominates samples from the lower MOW core layer and in the North Atlantic deep water below. Shelf edge foraminifera are common in assemblage 2a which shows the highest proportions in samples from 103 to 272 m. Assemblage 2b is dominated by upper slope species and suspension-feeders that are frequent in the upper MOW core layer and in distal settings between 396 and 901 m. Species from assemblage 3 prefer epibenthic habitats and are recorded with high proportions exclusively in the immediate flow paths of the upper MOW between 496 and 881 m. Colonisation structures and species composition of epibenthic assemblages from the proximal facies largely differ from those in distal settings. In general, epibenthic foraminifers only use elevated substrates under the influence of near-bottom flow. Under high current velocities, epibenthic foraminifers prefer large and heavy objects. They colonise high attachment levels where a maximum yield of advected food particles can be achieved. In distal settings at lower flow velocities, the elevation height does not exceed 20 mm above the surrounding sediment surface. This level is related to a hydrologic transition layer with high concentrations of suspended particles. The comparison of microhabitat preferences and faunal structure under high and low current velocities reveal that substrate stability may be a confining environmental variable for endobenthic and shallow epibenthic foraminifers. The observations also indicate that the preferential settling height of epibenthic foraminifera is related to the highest lateral flux rates of food particles within reach from the sea floor. A dynamic selection of elevated microhabitats is only used by 7.8% of all species recognised in the Gulf of Cadiz area.     

Neogene biofacies in eastern Venezuela and their calibration with seismic data

A detailed micropaleontologic study of Miocene foraminifers was made in order to integrate the seismic and biostratigraphic information in the Maturín sub-basin, eastern Venezuela. The sequence studied involves the Freites, Oficina, and Carapita Formations: The Freites and Oficina Formations are characterized by interbedded shale, siltstone, and sandstone. However, the Carapita Formation is formed mainly by shale and occasional thin sandstone beds, which sometimes represent turbiditic deposits.Analysis of existing biostratigraphic information from several wells and the recent exploration in the area, serve as a basis for distinguishing the faunal assemblages and their distribution and faunal variations, as well as, for determining chronological and paleobathymetric changes in the sequence studied.Towards the northeast, biofacies are useful for correlation throughout the area. These assemblages contain a higher diversity and abundance of calcareous forms, plus deep-water agglutinated foraminifers, typical of normal marine outer-neritic to bathyal conditions. To the southwest, however, we found shallow biofacies which are represented mainly by agglutinated genera and lower values for the abundance and diversity of calcareous specimens, especially planktic species. These parameters suggest the existence of water masses with low-oxygen content and large amounts of terrigenous and organic material in suspension.Biofacies and paleobathymetric data from each of the wells were compared with regional seismic lines to interpret changes from platform to slope water depths within the area.Analysis of species associations in the Miocene strata of the Maturín sub-basin, Venezuela, established a faunal variation that demonstrates a deepening trend from southwest to northeast.     

Radiolarian faunal turnover across the Oligocene/Miocene boundary in the equatorial Pacific Ocean

The global warming trend of the latest Oligocene was interrupted by several cooling events associated with Antarctic glaciations. These cooling events affected surface water productivity and plankton assemblages. Well-preserved radiolarians were obtained from upper Oligocene to lower Miocene sediments at Ocean Drilling Program (ODP) Leg 199 Sites 1218 and 1219 in the equatorial Pacific, and 110 radiolarian species were identified.Four episodes of significant radiolarian faunal changes were identified: middle late Oligocene (27.5 to 27.3 Ma), latest Oligocene (24.4 Ma), earliest Miocene (23.3 Ma), and middle early Miocene (21.6 Ma). These four episodes approximately coincide with increases and decreases of biogenic silica accumulation rates and increases in δ¹⁸O values coded as “Oi” and “Mi” events. These data indicate that Antarctic glaciations were associated with change of siliceous sedimentation patterns and faunal changes in the equatorial Pacific.Radiolarian fauna was divided into three assemblages based on variations in radiolarian productivity, species richness and the composition of dominant species: a late Oligocene assemblage (27.6 to 24.4 Ma), a transitional assemblage (24.4 to 23.3 Ma) and an early Miocene assemblage (23.3 to 21.2 Ma). The late Oligocene assemblage is characterized by relatively high productivity, low species richness and four dominant species of Tholospyris anthophora, Stichocorys subligata, Lophocyrtis nomas and Lithelius spp. The transitional assemblage represents relatively low values of productivity and species richness, and consists of three dominant species of T. anthophora, S. subligata and L. nomas. The characteristics of the early Miocene assemblage are relatively low productivity, but high species richness. The two dominant species present in this assemblage are T. anthophora and Cyrtocapsella tetrapera. The most significant faunal turnover of radiolarians is marked at the boundary between the transitional/early Miocene assemblages.We also reviewed changes in other microfossil assemblages in the low latitudes during the late Oligocene through early Miocene. The microfossil assemblages of major groups show sequential changes near the Oligocene/Miocene (O/M) boundary (23.8 Ma). Many extinction events and some first occurrences of calcareous nannofossils and many occurrences of radiolarians are found from about 24.8 to 23.3 Ma, and first occurrences of planktic foraminifers and diatoms followed from 23.2 through 22 Ma. Hence, the O/M boundary is identified as a significant level for microfossil evolutions.     

Species richness and assemblage structure of Trichoptera in Danish streams

• 1 Species richness and assemblages of Trichoptera from 157 ‘pristine’ Danish lowland stream sites were analyzed, for dependence on geographical position of the sites and simple physical variables, using two way indicator species analysis and detrended correspondence analysis.
• 2 A total of 106 species were recorded, representing ≈ 90% of the species pool known from Danish streams. Only seven species occurred at more than half the sites, whereas an additional 11 species were found at more than a quarter of the sites.
• 3 Although sites showed significant regional differences in environmental variables (stream order, width, slope and presence/absence of riparian forest), species richness and assemblages were primarily correlated with stream order, width and slope. Maximum richness was found at the largest (5th order) stream sites.
• 4 Regional differences in species assemblages were found, with several species being absent from the islands Funen and Bornholm. Species assemblages also differed between forested and non‐forested stream sites.
• 5 We found evidence that stream temperature may be of only minor importance in determining Trichoptera species richness and assemblage composition in Danish streams compared to other size‐related physical factors.

     

Patterns in cumulative increase in live and dead species from foraminiferal time series of Cowpen Marsh, Tees Estuary, UK: Implications for sea-level studies

We have collected live and dead foraminiferal times-series data at 2-weekly intervals for a 12-month period from the intertidal zone of Cowpen Marsh, Tees Estuary, UK. The data from the 689 samples show profound differences between live and dead assemblages, although assemblages are dominated by just three species, Haynesina germanica, Jadammina macrescens and Trochammina inflata, which represent over 70% of the assemblage. The cumulative increase in species of most environments approximates to a lognormal or log series. None of the datasets show a broken stick pattern. The cumulative maximum number of species, which represents the species carrying capacity of the environment, is recorded earlier in the life assemblages than the dead counterparts. The dead assemblage of Cowpen Marsh is found to have a higher abundance (435 compared to 163 individuals/10 cm³) and number of species (52 compared to 28) than its live counterpart because the dead assemblage represents many generations added over a long period of time. In contrast, some species are recorded in the live dataset that were not found in the dead assemblage, indicating the dead record is either incomplete (e.g. taphonomic change) or inadequately sampled.We investigated the influence of patterns in cumulative increase on dead assemblages for sea-level reconstructions through the development of foraminiferal-based transfer functions. The cumulative transfer functions suggest that the performance improves during the first six sample intervals of the time-series dataset with reconstruction differing by 1.2 m and remains constant thereafter.     

Benthic foraminifera of a Miocene canyon and fan

We present benthic foraminiferal assemblage data from an exhumed Miocene canyon and fan system from the Tabernas Basin (SE Spain). The presence of good indicator taxa and unique assemblages occupying specific environments allows the distinction of slope, canyon and fan environments within the Tabernas Basin by foraminiferal assemblages alone. Five assemblages are defined on the basis of the occurrence of the indicator taxa. Primary control on the distribution of these assemblages is consistent with trends of physical disturbance and consequent defaunation. Barren samples, which are predominantly found in high-energy parts of the proximal canyon, are recognized as representing recently defaunated substrates (i.e. early successional assemblages). High diversity assemblages containing a high abundance of agglutinated taxa are recognised in the undisturbed slope sequences as being the regional equilibrium (“climax”) fauna. Intermediate between these end-members are assemblages with low diversity, dominated by calcareous taxa typically found in the relatively low-energy canyon and fan environments, which are recognized as representing the middle phases of the ecological succession. Two further assemblages, a low diversity assemblage typified by Cassidulina laevigata and Bulimina costata and a very low diversity assemblage dominated (> 10% of all benthic tests) by Globobulimina spp., are restricted to low-energy parts of the canyon and fan, and are absent from the proximal canyon and slope. The composition of these assemblages indicate that nutrient supply/oxygenation is a secondary control on the palaeoecology of the canyon system. A conceptual model for the recolonisation of defaunated substrates in El Buho Canyon is proposed, in which either an oligotrophic climax assemblage or a eutrophic climax assemblage can be achieved at the completion of recolonisation of defaunated substrates, depending on environmental conditions.     

Importance of historical factors on species richness and composition of butterfly assemblages (Lepidoptera: Rhopalocera) in a northern Iberian mountain range

ABSTRACT. The butterfly assemblages of three vegetation types (pasture, heathland and rocky outcrop with Genista spp.) and two geographical orientations (a northern slope and a sheltered gorge) were studied along an altitudinal gradient in the Picos de Europa in northern Spain. In order to study the effects or historical climatic changes on current butterfly assemblages, it was examined if changes in richness and faunal composition of assemblages were joined with changes in their biogeographical composition. The three vegetation types showed characteristic butterfly assemblages, but no difference in species richness and biogeographical composition was found. Species richness in the sheltered gorge was higher than in the northern slope. Faunal composition also varied between orientations and there were more widespread and Mediterranean species in the sheltered gorge than in the northern slope. Species richness declined with increasing altitude, though a midaltitudinal peak was observed. There was a faunal segregation between high and low localities. Species richness of widespread and Mediterranean butterflies decreased as altitude increased, whereas the reverse was true for montane species. Moreover, biogeographical elements differed in their climatic tolerances measured as altitudinal ranges. Therefore, changes in richness and composition of butterfly assemblages between both slopes and along the altitudinal gradient were joined in part with variation in their biogeographical composition. These results suggest that current species richness and composition of butterfly assemblages in the Picos de Europa might be the consequence of differential colonization of refuges during the past climatic changes.     

Biostratinomy and palaeoecology of the cassian formation (Triassic) of the Southern Alps

The sediments forming the Cassian Formation (Middle—Upper Triassic) of the Central Dolomites represent the following environments: back-reef areas, shallow marginal basins, slope, and central basin. In each of these major environments faunal assemblages were found whose composition, mode of preservation and occurrence proved to be characteristics. In the back-reef areas, algal/foraminifera- and calcareous sponge/coral-patch reefs with a highly diverse fauna of frame-builders and reef-dwellers, in some localities excellently preserved, form the most conspicuous feature. In the shallow marginal basins autochthonous algal meadow/soft-bottom associations dominated by gastropods and deposit-feeding bivalves prevail. Slope deposits do not contain any autochthonous associations but either remains of pelagic faunas or transported faunal elements of shallow-water origin in the form of Cipit boulders (subaerially cemented parts from the outer edge of the carbonate platforms), worn Pachycardia rugosa-dominated, or echinoderm debris-dominated assemblages. Sediments of the central basin lack benthic faunas but contains pelagic assemblages of low diversity dominated by Daonella, Posidonia, and some ammonites.     

Pleistocene agglutinated foraminifera from the Lomonosov Ridge and Amundsen Basin, Arctic Basin. Initial report on piston cores 2177-5 (KAL) and 2176-3 (KAL)

Noncalcareous Pleistocene sediments of the Central Arctic Ocean contain sparse benthic foraminiferal assemblages consisting entirely of agglutinated taxa. Deep water agglutinated foraminifera are studied from two piston cores collected from the Lomonosov Ridge and Amundsen Basin [Cores PS 2177-5 (KAL) and 2176-3 (KAL)]. Core PS 2177-5 (KAL) contains an assemblage of 10 species, dominated by Cyclammina pusilla Brady, and is interpreted to reflect a bathyal environment with variable organic flux and nutrition levels. Core PS 2176-3 (KAL) in the Amundsen Basin yielded a very depauperate benthic foraminiferal assemblage. It is assumed that the environment was inhospitable for agglutinated foraminifera.     

Spatial-temporal distribution of preimaginal blackflies in Neotropical streams

The current study investigates the spatial-temporal distribution of preimaginal blackflies in three a priori established, adjacent areas of Brazil and Venezuela. First we tested the hypothesis that the distribution of individual simuliid species, over two geographic scales, were predictable on the basis of several habitat parameters. Secondly, we determined if local species assemblages remain constant over two spatial axes, i.e., were species assemblages predictable within and between defined regions. Finally we compared the species assemblage between Venezuelan streams sampled in both the wet (October) and dry (February) seasons. As stream conditions changed across a north–south gradient, so did the occurrence of the most common species. This change in species composition from upland to lowland areas is consistent with the patterns of faunal change seen in North American simuliid assemblages. Discriminant Function Analysis showed a strong association between regional demarcations and stream site conditions. These results were paralleled by the strong correspondence between species assemblages and these regions. Thus each region presented both distinct stream environments and species assemblages. Monte Carlo analysis suggests that some if not all species are not only present in both the wet and dry season but that they are continuing to use the same stream sites. Three broad contingent rules for blackfly species assemblages in new world streams are put forward; (i) the ubiquitous nature of simuliids; (ii) species often distribute themselves along an axis of stream size and; (iii) there is a strong and consistent correspondence between regional characteristics of streams and the species assemblage.