Benthic Microfauna Research Articles

Late Miocene to Early Pliocene paleoceanographic evolution of the Central South Pacific: A deep-sea benthic foraminiferal perspective

The bottom water conditions in the Central South Pacific (CSP) and associated changes in the Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW) under warmer-than-present conditions need to be better understood. These water masses transfer their properties to the major ocean basins. We analyzed Late Miocene to Early Pliocene (5.6–3.6 Ma) marine sediment core sections from the CSP for benthic foraminifera, ice rafted debris (IRD), Ostracoda, planktic foraminifera Orbulina universa abundance, and organic geochemical proxies to assess the bottom water characteristics under warmer-than-present day conditions. A significant increase in IRD abundance between 5.3 and 4.9 Ma marks the Early Pliocene warm phase. The benthic foraminiferal assemblages indicate shifts in bottom water conditions over time in the CSP region. Between 5.6 and 5.3 Ma, predominantly oxygenated bottom water with moderate organic matter flux prevailed. This shifted to suboxic conditions with increased organic matter flux from 5.3 to 4.9 Ma. Subsequently, between 4.9 and 4.4 Ma, bottom water conditions alternated frequently between oxic and suboxic states. Enhanced bottom water formation and inflow of LCDW and AABW in the CSP during 4.4–4.0 Ma promoted oxygenated conditions, accompanied by low organic export flux. However, sluggish bottom water circulation from 4.0 to 3.6 Ma reverted to suboxic conditions, associated with increased carbon burial. Notably, productivity peaked intermittently between 5.3 and 3.6 Ma, as indicated by the occurrence of suboxic species assemblages and increase in the abundance of Orbulina universa, benthic microfauna (ostracods), and other paleoproductivity indicators.

A Recommended Monitoring Tool for the marine ecological status studies in the Western Moroccan Mediterranean coastal areas

This research provides general guidelines for monitoring the environmental quality state of the marine ecosystems using benthic microfauna as a bioindicator tool in the Western Moroccan Mediterranean coastal areas. The current faunistic composition of 18 superficial sediment samples collected in areas having a wild range of environmental conditions have been the subject of factorial correspondence and hierarchical classification analysis, allowing us to follow the distribution patterns of the benthic assemblages. Considering the influence of both hydrodynamic and sedimental conditions on the superficial sediment, recognized in this study as the main environmental factors affecting the distribution of species in this type of environment, we were able to delineate three environmental units, with specific faunistic response related to the corresponding environmental conditions. Leading us to identify the optimal sampling area for the biomonitoring surveys in this region. Shallow and high-energy coastal areas were found to limit data collection and the representation of the sampling area, while low-energy areas were identified as ideal for environmental surveys, showcasing strong faunistic response to stressful conditions. we recommend to conduct the ecological monitoring studies in the 10–30-meter depth range, where the environmental conditions favor the assessment of the current environmental quality state by the benthic microfauna.

Benthic foraminifera across the Albian–Cenomanian transition and their paleoceanographic significance during OAE1d in the western Tethys (Umbria–Marche Basin, Italy)

The benthic foraminiferal assemblages from the upper Albian-lower Cenomanian interval of the Scaglia Bianca Formation in the Monte Petrano (MP) and Le Brecce (LB) sections (Umbria–Marche Basin; Italy) provide a detailed record of the faunal changes across the Oceanic Anoxic Event 1d (OAE 1d). Fluctuations in abundance, diversity, and species composition reflect variations in bottom-water oxygenation and organic carbon fluxes. Benthic foraminifera are integrated with planktonic foraminifera, calcareous nannofossils, and geochemical proxies to reconstruct the bottom and surface water conditions across the OAE 1d in the Umbria–Marche Basin.The pre-OAE 1d interval was characterized by benthic foraminifera that thrived under stable mesotrophic condition in bottom waters. In surface waters, planktonic foraminifera indicate dominant mesotrophic conditions in agreement with calcareous nannofossil assemblages suggesting a regime of higher fertility under cooler conditions.During the OAE 1d interval, benthic foraminifera display an increase in the abundance of infaunal taxa, suggesting mesotrophic conditions in bottom waters. Nevertheless, within the Pialli Level, the six laminated black-to-dark grey shale horizons (MP1/LB1 to MP6/LB6), benthic foraminifera are absent or highly impoverished (MP1, MP2, MP4, MP6, LB5, LB6), suggesting hypoxic/anoxic conditions in bottom waters. Planktonic foraminifera in this interval reflect mesotrophic to oligotrophic conditions under the presence of an expanded mixed layer and deeper thermocline in the surface waters. Calcareous nannofossils record warm conditions and lower fertility starting just prior to and across the OAE 1d. However, higher values of fertility are recorded in the black-to-dark grey shales MP3/LB3, MP4/LB4 and MP5/LB5 of the Pialli Level.The post-OAE 1d interval is marked by an increase in the diversity of benthic foraminifera, indicating a restoration of the oxygen conditions in a continuous mesotrophic regime in bottom waters. The surface waters experienced oligotrophic conditions based on the planktonic and calcareous nannofossils.A minor discrepancy between benthic foraminifera and geochemical reconstruction of oxygenation levels of bottom waters was recorded, especially in the Pialli Level. The benthic microfaunas appear to be very sensitive to very short-term oxygen depletion at the seafloor when geochemical proxies suggest temporary suboxia. This might indicate that very rapid redox changes are not resolved by bulk elemental data. Otherwise, benthic foraminifera might be much more responsive to very low concentrations of oxygen in bottom waters and temporarily disappear under strong suboxia before reaching fully anoxic conditions.

Spatial Distribution of Benthic Foraminifera in the Neretva Channel (Croatia Coast): Faunal Response to Environmental Parameters

Benthic foraminiferal assemblages have been studied at 11 sediment surface samples located in the Neretva Channel covering the delta habitat and the adjacent open sea areas. The major objective of the investigation was to explore the main environmental parameters affecting the benthic foraminifera compositional changes. To this end, a statistical approach was applied that integrates micropaleontological data with physical, geochemical and sedimentological parameters (total organic carbon and grain size). Statistical analyses identified four distinct groups (cluster A1, A2, B1, B2) corresponding to different environmental settings. Cluster A1 groups samples under Neretva river influence and is characterized by Aubignyna perlucida, Nonionella turgida, Eggerelloides scaber and Rectuvigerina sp.; species able to live in organic-matter-rich sediments and in a wide range of oxygen content. Cluster A2 includes samples distant from the fluvial outlet and samples along the NW coast partially influenced by the Neretva river plume. In these environmental conditions, Ammonia beccarii, Bulimina marginata, Nonionella turgida and Textularia sp. resulted as the most characteristic taxa. Cluster B1 distinguishes the deepest stations which are in connection with the open Adriatic Sea. Here Asterigerinata mamilla, Buccella granulata, Cibicides group, Reussella spinulosa and Textularia sp. reach their maximum abundance associated with coarse-grained sediments. Cluster B2 groups samples collected in the inner bay of the southernmost sector of the studied area characterized by silt and clay and a negligible influence by river inputs. The benthic microfauna is principally composed of Miliolids, Porosononion granosum and Textularia sp.

CAGE-18-3 Cruise to the Barents Sea, Storfjorden Trough, East Greenland Ridge (Leg 1, 2), Arctic Ocean Vestnesa Ridge, and PKF, (Leg 3)

From the evening of June 29th to the evening of July 10th 2018, CAGE at the Department of Geology Uit, the Arctic University of Norway, arranged a scientific cruise aimed at investigating methane seep sites by surface sediment sampling, sediment core sampling, plankton sampling and water sampling. The areas for investigation were the Barents Sea (Crater area), Storfjorden Trough (Pingo area),East Greenland Ridge (non-seep, for IODP-proposal) (Leg 1 and 2) and the western Svalbard margin, Vestnesa Ridge, Arctic Ocean and Prins Karls Forland (Leg 3) on R/V “Helmer Hanssen”. The scientific sampling was done within the framework of several ongoing projects at the Department of Geology, University of Tromsø: “CAGE -Centre for Arctic Gas Hydrate, Environment and Climate”-WP6: “Methane Release, Ocean Acidification and CO2” hereunder ocean acidification impact on marine calcifiers (planktic foraminifera and pteropods, methane seeping impact on ocean acidification and productivity, the state of the inorganic and organic biological pump from foraminifera, bottom water temperature change and impact on release of methane, living benthic microfauna studies from seep sites for geochemical investigations for calibrations for paleostudies. A total of 15 gravity cores (c. 60 m),and 31 CTD (conductivity-temperature-depth) casts were performed, 11 plankton net (no. 12 failed because the net was torn completely), 22 boxcore samples x 6 surface samples for each. A total of 137 lines of acoustics and seismics together were performed. Chirp profiles and multi-beam lines were acquired during transits and in surveys mapping of new seep sites northeast of “Crater” area, seep sites in Storfjorden Trough, East Greenland Ridge, seeps in Hinlopen trough and Norske Banken, the east slope of Yermak Plateau, active and inactive pockmarks at Vestnesa Ridge and a small patch off PKF for WP4. All acoustic and seismic investigations were performed with soft-start of all instruments (Echo-sounders, deep-penetrating echosounder (‘Chirp’), Multi-beam echosounder and mini-air gun). The cruise may be known as: CAGE18_3_leg1 CAGE18_3_leg2 CAGE18_3_leg3

Micro- and macrofauna of benthic invertebrates of the estuary section of the Mokra Moskovka, a small river in the City of Zaporizhzhia

Nowadays, in the period of scientific and technological progress, the anthropogenic impact on the environment keeps increasing. At the same time, its forms and its degree are very diverse. The study of aquatic ecosystems, including ecosystems of small rivers, is one of the applied environmental researches. Small rivers form water resources, hydrochemical composition and water quality of medium and large rivers. They form natural landscapes and contribute to human economic activities.
 Most of the indicators classify the current environmental state of small and medium rivers of Zaporizhzhia Region as unsatisfactory. The main reason for this situation is an excessive anthropogenic load on environmental systems of small rivers that have a noticeable reaction to any interference. One of the consequences of this process includes siltation of small rivers. A small river Mokra Moskovka is not an exception to the above-described characteristics of aquatic ecosystems. The river flows through the territory of Zaporizhzhia Region and its lower part of about 11 km long flows in the densely built-up part of the City of Zaporizhzhya. The mouth section of the Mokra Moskovka River is 2.6 km long and runs through the territory of Aleksandrovsky and Kommunarsky districts of Zaporizhzhia from the river's mouth to the Zaporizhzhia-1-Zaporizhzhia-2 railway bridge. Over the years of its existence, the mouth section of the small river's bed silted up considerably and has an unsatisfactory condition. This is due to the rising of the Kakhovka Reservoir water level and daily fluctuations of the Dnipro's water level that together lead to the reverse movement of water masses and emergence of stagnant phenomena within the studied portion of the river's bed. In addition, the outlets of the municipal rainwater drainage system present a significant source of the sediment, debris and pollutants entering the river.
 In order to improve the environmental condition of the Mokra Moskovka and remove its silt sediments within the bounds of the city, the riverbed was being cleared during 2004-2013. Our data indicate that the thickness of the river's silt sediments reaches 1.0-1.5 m in some places. To restore and maintain favorable hydrological regime and sanitary condition of the mouth section of the Mokra Moskovka it is planned to clean the mouth section of the river channel from silt sediments using hydromechanization technologies and dredging mechanisms in 2022-2023 (scheduled activities).
 The research is aimed at studying the structural organization of the bottom fauna of the estuary section of a small river Mokra Moskovka within the urban ecosystem. The work is based on the results of our own hydrobiological research. During the observation that took place in 2021 53 species of benthic invertebrates were recorded at the mouth of the watercourse. It was found that, out of the total number, 21 species belonged to the macrozoobenthos and 32 – to the benthic microfauna groupings. The conducted saprobiological assessment of the studied river sections for the indicated organisms of micro- and macrozoobenthos revealed that the surveyed part of the watercourse belongs to the α-mesosaprobic zone and is classified as "polluted waters" according to the surface water quality classification. In order to improve the environmental condition of the mouth section of the Mokra Moskovka River it is necessary to implement certain measures of biological water treatment using modern biotechnological solutions developed in Ukraine.

Grain-size trend and ecological state of southern mediterranean coastal lagoons: Case of the Gulf of Tunis

Coastal lagoons are among the highest biological productive ecosystems; they offer a variety of habitats and feeding grounds for several species. These ecosystems are besmirched by human activities which entail the degradation to their environmental aspects. The purpose of this study is the identification of the grain-size characteristics and the unprecedented recognition of the vegetation cover, so as to assess the ecological state and the water body quality of Kalâat Andalous lagoon: a fast changing ecosystem under its dynamic sandy spit and human pressures. The methodology is based on the sedimentological analysis and the microfauna identification. The study of the environmental quality of the lagoon was built on an unprecedented identification of the macrophyte communities and the use of diversity indexes and the EXCLAME indicator; the latter combines the taxonomic composition and the species abundance. The sedimentological investigations showed that the northern and southern areas of the lagoon, as well as its channel area are all dominated by a sandy facies provided by the continental shelf i.e. the nearshore zone. The central area of the lagoon is characterized by the finest grain size facies (<0.063 mm) mostly supplied by the aeolian terrestrial fluxes and the delta flood yields. The harvested pelagic and benthic microfauna indicated that the lagoon is supplied by sediments of mixed continental-fluvial and marine origins. The inventory of macrophytes demonstrates the presence of 19 species, five of which are reference species. The dominant taxa are those of Green algae (53%) with several opportunistic and invasive species with a high outbreak altering the ecosystem's natural balance, then Brown algae (21%), Red algae (16%) and angiosperms (10%). Those results, along with the biodiversity indexes outcomes, revealed the quality loss of the ecosystem and the water eutrophication. The lagoon floristic communities are slightly unbalanced, which might be due to the natural disturbance and the anthropogenic activities. Those results conform to the EXCLAME indicator (EQRMAC = 0.24), illustrating the poor ecological state of the Kalâat Andalous lagoon water body.

Paleobathymetric Zonation of the Middle–Upper Jurassic Deposits in the Ulyanovsk–Saratov Trough (Russian Platform) Based on Benthic Foraminifers

The environments, favorable for the development of benthic microfauna were predominant in the Jurassic Sea in the northeastern part of the Ulyanovsk–Saratov Trough (Russian Platform). Such parameters as the distribution and the taxonomic composition of the assemblage of Jurassic benthic foraminifers, their abundance, generic and species diversity, the occurrence of new species, a ratio of species with agglutinating and calcareous shells serve as a basis for developing the paleobathymetric zonation of the basin. The tracing of the variations in these parameters through the section enables us to construct a quantity paleobathymetric curve for the Middle-Late Jurassic and to distinguish the sequence–stratigraphic elements.

Large‐scale patterns of biofilm‐dwelling ciliate communities in a river network: Only small effects of stream order

Although biofilm‐dwelling microfauna (i.e., small metazoans and protzoans) can play an important role in the flux of matter in running waters, their dynamics, and control within stream networks are as yet poorly understood. Here, we analyzed the longitudinal (from first order stream to large river) dynamics of ciliates associated to hard substrate within a river network. Both ciliate abundance and their taxonomical community structure showed no correlations to stream order, although the community structure of the largest river, the Rhine, differed from those of the other rivers. The abundances of biofilm‐dwelling bacteria, algae, rotifers, and nematodes also showed no correlation with stream order. The above results contrast to the abundances of planktonic algae and bacteria that were significantly and positively correlated with the stream order. The results showed that stream size and the corresponding planktonic resource concentration are not reliable parameters in predicting the abundances and community structures of biofilm‐dwelling ciliates. In fact, local parameters seemed to have stronger effects on benthic microfauna communities. Thus, the impact of small‐scale habitat patterns needs further attention in explaining the community structure of biofilm‐dwelling ciliates.

A Survey of the Benthic Microfauna of the Marine Ecosystem on IRIS-1 Oil Platform at the Cape Skirring in Casamance, Senegal

Long-time suspected as having great natural resources of petroleum, oil was only discovered as recently as 2001 in the West African marine coastal ecosystem. The potential area harboring this offshore oil extends on six countries: Mauritania, Senegal, Guinea Conakry, Guinea and Cape Verde. A large Shallow block called AGC Shallow is in offshore area located between Senegal and Guinea Bissau and has an offshore drilling called IRIS-1 drilling, which covers 1,700 km2. Although these oil reserves are likely to generate significant new economic interests, especially for local communities living along the Senegalese coast to Guinea Bissau, their exploitation must take into account the biological and ecological potential side effects on aquatic ecosystems and their biological diversity. The objective of this study was to characterize the habitat and benthic fauna present in IRIS-1 drilling area. The results showed that the benthic microfauna around the IRIS-1 drilling point has a medium specific diversity of about 44 species with a more or less pronounced spatial variability. Marine mollusks, essentially sessile species, are the most important benthic species groups encountered. These organisms are quite sensitive to oil disturbances, which at long-term, may have serious effects on them. We suggest the proposed mitigation and mitigation measures for the IRIS-1 should focus on elements that are at least harmful to the environment and wildlife populations inhabiting the drilling zone. Dispersants may also be used to reduce the toxicity of products discharged into the sea.

Diet of the amphi-Atlantic scaphopod Fissidentalium candidum in the deep waters of Campos Basin, south-eastern Brazil

Specimens of Fissidentalium candidum collected at Campos Basin, south-eastern Brazil, had their diet investigated in order to assess its feeding habits. Benthic prey exceeded the planktonic ones as expected and Foraminifera constituted the most frequent prey taxa, comprising about 99.5% of the scaphopod diet; the remaining components included a few molluscs (gastropods, bivalves and scaphopods), a nematode, an ostracod crustacean, fish otoliths, unknown partial organisms and inorganic material (e.g. sediment grains and polymetallic nodules). Amongst the species previously studied, F. candidum stood out by presenting the highest dietary diversity (H = 3.35) and species richness (N = 118). Predator and prey dimensions were not correlated and no spatial variation was observed in the diet amongst the three collection sites in the mid-slope of Campos Basin. Generalism, high rate of rare or unimportant species and high contribution of within-phenotype component to the niche width were important features of the trophic ecology of F. candidum. Inhabiting the deep water of Campos Basin, this dentaliid obtained most of its energy from the benthic microfauna, being a specialized foram predator with moderate preference for, and moderate selection against, several species.

Unburrowed mudstones may record only slightly lowered oxygen conditions in warm, shallow basins

Unbioturbated mudstones and highly bioturbated silty and sandy mudstones from the late Albian of Alberta, Canada, are characterized by their ichnological, foraminiferal, and geochemical signatures. A comparison of these data sets is undertaken to isolate the dissolved oxygen (DO) conditions that led to the preservation of unbioturbated mudstones versus highly bioturbated silty and sandy mudstones. Highly diverse and abundant benthic foraminiferal assemblages, coupled with conclusive geochemical signatures, indicate that unbioturbated mudstones were deposited under oxic bottom waters. The paucity of bioturbation in these rocks is attributed to the persistence of low-oxic conditions (5 > DO > 2 mg L–1) at the seafloor, comparable to the present-day Gulf of Mexico. We assert that unbioturbated mudstone should not automatically be attributed to oxygen deficiency (<2 mg L–1). Instead, it may reflect oxygenation sufficient to support benthic microfauna (foraminifera) but insufficient to sustain a diverse ecosystem of macrofauna (burrowing fauna). Moreover, we propose that the distribution of unburrowed mudstones deposited below low-oxic waters is predictable. A paucity of bioturbation is normal in shallow marine (below fair-weather wave base to ∼200 m water depth) deposits of subtropical to tropical ocean basins and/or semienclosed seaways.

Cyclically-arranged, storm-controlled, prograding lithosomes in Messinian terrigenous shelves (Bajo Segura Basin, western Mediterranean)

This work focuses on a Messinian shallow-marine terrigenous unit, termed the La Virgen Formation, which forms part of the sedimentary infill of the Bajo Segura Basin (Betic margin of the western Mediterranean). This formation was deposited during a high sea level phase prior to the onset of the Messinian Salinity Crisis. Stratigraphically, it comprises a prograding stack of sandstone lithosomes alternating with marly intervals (1st-order cyclicity). These lithosomes are characterized by a homoclinal geometry that tapers distally, and interfinger with pelagic sediments rich in planktonic and benthic microfauna (Torremendo Formation). An analysis of sedimentary facies of each lithosome reveals a repetitive succession of sandy storm beds (tempestites), which are separated by thin marly layers (2nd-order cyclicity). Each storm bed contains internal erosional surfaces (3rd-order cyclicity) that delimit sets of laminae. Two categories of storm beds have been differentiated. The first one includes layers formed below storm wave base (SWB), characterized by traction structures associated to unidirectional flows. The second category consists of layers deposited above the SWB, which display typical high regime oscillatory flow structures. The 1st-order cyclicity recorded in the La Virgen Formation corresponds to sapropel/homogeneous marl precessional cycles formed in a pelagic basin context (Torremendo Formation).

The Genus Cladophora Kützing (Ulvophyceae) as a Globally Distributed Ecological Engineer.

The green algal genus Cladophora forms conspicuous nearshore populations in marine and freshwaters worldwide, commonly dominating peri-phyton communities. As the result of human activities, including the nutrient pollution of nearshore waters, Cladophora-dominated periphyton can form nuisance blooms. On the other hand, Cladophora has ecological functions that are beneficial, but less well appreciated. For example, Cladophora has previously been characterized as an ecological engineer because its complex structure fosters functional and taxonomic diversity of benthic microfauna. Here, we review classic and recent literature concerning taxonomy, cell biology, morphology, reproductive biology, and ecology of the genus Cladophora, to examine how this alga functions to modify habitats and influence littoral biogeochemistry. We review the evidence that Cladophora supports large, diverse populations of microalgal and bacterial epiphytes that influence the cycling of carbon and other key elements, and that the high production of cellulose and hydrocarbons by Cladophora-dominated periphyton has the potential for diverse technological applications, including wastewater remediation coupled to renewable biofuel production. We postulate that well-known aspects of Cladophora morphology, hydrodynamically stable and perennial holdfasts, distinctively branched architecture, unusually large cell and sporangial size and robust cell wall construction, are major factors contributing to the multiple roles of this organism as an ecological engineer.

Ostracode Mg/Ca paleothermometry in the North Atlantic and Arctic oceans: Evaluation of a carbonate ion effect

The reconstruction of deep‐sea bottom water temperature (BWT) is important to assess the ocean's response to and role in orbital‐ and millennial‐scale climate change. Deep‐sea paleothermometry employs magnesium to calcium (Mg/Ca) ratios in calcitic benthic microfaunas (foraminifera, ostracodes) as a primary proxy method. Mg/Ca paleothermometry may, however, be complicated by bottom water carbonate ion chemistry, which might affect Mg/Ca ratios in shells. To address temperature and carbonate ion influence on Mg/Ca ratios, we studied Mg/Ca ratios in the benthic ostracode genus Krithe in the North Atlantic and Arctic oceans using a 686‐specimen core top collection, including 412 previously unpublished analyses. Mg/Ca ratios are positively correlated to temperature in multiple species from the North Atlantic [BWT = (0.885 × Mg/Ca) − 5.69, r2 = 0.73] and for K. glacialis in the Arctic Ocean and Nordic Seas [BWT = (0.439 × Mg/Ca) − 5.14, r2 = 0.50], consistent with previously published calibrations. We found no evidence for a relationship between Krithe Mg/Ca and carbonate ion saturation in the North Atlantic Ocean, Nordic Seas, and Arctic Ocean, supporting the use of Krithe Mg/Ca for reconstructing past BWT.

Coastal Sedimentation Associated with the Tohoku Tsunami of 11 March 2011 in South Kuril Islands, NW Pacific Ocean

Sediment deposited by the Tohoku tsunami of March 11, 2011 in the Southern Kurils (Kunashir, Shikotan, Zeleniy, Yuri, Tanfiliev islands) was radically different from sedimentation during local strong storms and from tsunamis with larger runup at the same location. Sediments from the 2011 Tohoku tsunami were surveyed in the field, immediately and 6 months after the event, and analyzed in the laboratory for sediment granulometry, benthos Foraminifa assemblages, and diatom algae. Run-up elevation and inundation distance were calculated from the wrackline (accumulations of driftwood, woody debris, grass, and seaweed) marking the distal edge of tsunami inundation. Run-up of the tsunami was 5 m at maximum, and 3–4 m on average. Maximum distance of inundation was recorded in river mouths (up to 630 m), but was generally in the range of 50–80 m. Although similar to the local strong storms in runup height, the tsunami generally did not erode the coast, nor leave a deposit. However, deposits uncharacteristic of tsunami, described as brown aleuropelitic (silty and clayey) mud rich in organic matter, were found in closed bays facing the South Kuril Strait. These closed bays were covered with sea ice at the time of tsunami. As the tsunami waves broke the ice, the ice floes enhanced the bottom erosion on shoals and destruction of low-lying coastal peatland even at modest ranges of runup. In the muddy tsunami deposits, silt comprised up to 64 % and clay up to 41.5 %. The Foraminifera assemblages displayed features characteristic of benthic microfauna in the near-shore zone. Deep-sea diatoms recovered from tsunami deposits in two closely situated bays, namely Krabovaya and Otradnaya bays, had different requirements for environmental temperature, suggesting these different diatoms were brought to the bays by the tsunami wave entraining various water masses when skirting the island from the north and from the south.

Riverine habitat heterogeneity: the role of slackwaters in providing hydrologic buffers for benthic microfauna

Slackwater habitats within lowland rivers support abundant biotic communities and provide these communities with a refuge from increases in discharge. These refuges allow biota to persist as discharges, vary and provide a source of colonists for slackwaters further downstream. In order to investigate the response of slackwater benthic microfaunal communities to changes in discharge, artificial slackwaters were created within the main channel of a lowland river and benthic microfaunal communities were sampled over a 60-day period. Benthic microfauna within the artificial and reference slackwaters were recorded in higher richness and abundance than in the main river channel. Within days the communities in the artificial slackwaters were similar to those in the reference slackwaters. The rapid speed of colonisation suggests that initial colonisation of slackwaters is likely to occur via active or passive dispersal of biota and that these systems and communities are resilient to changes in discharge.

A survey of the benthic microfauna (foraminifera, Ostracoda) on the Basque shelf, southern Bay of Biscay

In this work we describe by the first time the microfaunal content (foraminifers and ostracods) of the benthos of the Basque continental shelf, by studying the spatial distributions of benthic foraminifer and ostracod assemblages in relation to the environmental parameters affecting the sediments of this region of the Bay of Biscay. Most abundant benthic foraminifer species in the surface samples are Brizalina spathulata, Bulimina marginata, Cassidulina laevigata, Hyalinea balthica, Lobatula lobatula, Rosalina globularis, Textularia sagittula and Uvigerina peregrina. Most abundant and widespread ostracod species are Lindisfarnia guttata, Costa edwardsii and Pterygocythereis ceratoptera-jonesi group. Multivariate analyses (Cluster Q, R; DCA) of samples and species of these organisms have been performed to provide an accurate description of these distributions. Based on these analyses six different facies are characterised in this shelf, according to their microfaunal content as well as to the average values of environmental parameters (CaCO 3, POC, silt–clay and hypoxic biological markers). Of these facies, the eastern fringe and the mudpatch have a more pronounced hypoxic character relative to the western facies in this shelf. Results provided by benthic foraminifer and ostracod assemblages totally agree and indicate their dependence of the environmental parameters of the sediment. In the eastern area the influence of deeper waters has been detected, probably as upwelling through the canyons, evidenced by the occurrence of bathyal species of foraminifers ( Fontbotia wuellerstorfi, Hoeglundina elegans) and ostracods ( Krithe spp., Cytheropteron spp., Buntonia spp.). The noticeable oil-affection found in benthic specimens, very likely caused by the oil-spill of the “Prestige” in the benthonic environment of the Basque continental shelf, has been detected eight months after the spill. Despite the studied bathymetric range of 50 to 150 m, the depth interval of specimens affected by oil-spill is that of the outer shelf (93–150 m). Benthic microfauna evidence oil-pollution in the bottom sediments and demonstrate a wider affected area in the bottom of the Basque shelf than previously stated.

THE BAGELEN BEDS, CENTRAL JAWA

The Bagelen Beds of Cential Java are re-defined and described as a very deep marine olistostrome deposit of Early Oligocene age (about 32 1 / 2 MYBP). There is no indication that the clays have been tectonised and they are considered a pebbly-claystone or slump deposit rather than a tectconic melange.The benthic microfaunas are analogous to those found in open-ocean palaeobathymetries at around 3,000 metres, but it is argued that this interpretation may not be applicable to semi-restricted basins in a tectonically complex area. A shallower depth,of very roughly 1,000 to 2,000 m, is argued to be possible and that this would better fit tile epi-cratonic geological setting. The significance of a deep marine, slump-filled environment in the Early Oligocene of Central Java is discussed, and a suggestion made for the origin of the unusual mud-volcano found in the Sangiran Dome. Keywords: Bagelen beds, Olistostrome, slum deposit benthic microfaunas, epi-cratonic

Foraminiferal biofacies and paleoenvironmental implications of the Early Tortonian deposits of Gavdos Island (Eastern Mediterranean)

In this paper two adjacent (Bo and Potamos) sections from the Early Tortonian of the island of Gavdos, Eastern Mediterranean, are extensively studied and compared as for their lithology and micropaleontological content with final aim their paleoecological and paleoenvironmental interpretation. These two sections are composed of clayey sediments and reefal limestones and of marls and sands of turbiditic origin, respectively. The qualitative and quantitative micropaleontological analyses that were realised in the contained benthic microfauna showed that the two sections are characterized by a shallowing upwards-general trend. However, the combined lithological and micropaleontological data suggest that, although adjacent, the two sections underwent different paleoenvironmental evolutions during the early Late Miocene: on the one hand, reef growth at the Bo shelf is suggestive of a current, providing warm, clear and low-nutrient waters to the shelf, and on the other hand, benthic foraminiferal assemblages from the Potamos shelf indicate cooler and eutrophic conditions, induced by enhanced river runoff and upwelling, impeding reefal promotion. This difference may be due to the separation of Bo and Potamos shelf by an island acting as a local oceanographic and biogeographic barrier.