Benthonic Species Research Articles

The effect of bioturbation on the release behavior of polycyclic aromatic hydrocarbons from sediments: A sediment–seawater microcosm experiment combined with a fugacity model

The effects of two benthonic species, Perinereis aibuhitensis and Matuta planipes Fabricius, on the release of polycyclic aromatic hydrocarbons (PAHs) from sediments were investigated using a sediment–seawater microcosm. A Level IV fugacity model was used to simulate the behavior and fate of PAHs in the environment. This study revealed that both benthos significantly influenced the release of PAHs, and Matuta planipes Fabricius had a stronger disturbance effect than another. The final concentrations of Matuta planipes Fabricius group, Perinereis aibuhitensis group and the control group in the seawater phase reached 10.8, 9.94 and 7.90 μg/L, respectively. There were certain differences in the behaviour of the two benthonic species. Matuta planipes Fabricius caused more sediment resuspension, while Perinereis aibuhitensis increased the total organic carbon (TOC) content in the environment. The vertical concentration distribution of sediment indicated that vertical mixing was slightly stronger in the Matuta planipes Fabricius group than that in the Perinereis aibuhitensis group. The fugacity model effectively simulated the release behavior of PAHs, providing insight into PAH transport and distribution. The results demonstrated that bioturbation could promote the release of PAHs from seawater. The amount of PAHs released was significantly correlated with the biological habits of the benthos.

Paleoenvironments and Hydrocarbon Potential of Upper Cretaceous Shales in Agbabu-1 Well, Dahomey Basin – Insight from Geochemistry and Foraminifera Paleontology

Upper Cretaceous shales partially exposed in the northern fringes of the Dahomey Basin are well developed in the subsurface in Southwestern part of the basin where Agbau-1 well is sited. These shales were evaluated in respect to their paleoenvironments and potentials for hydrocarbon using foraminiferal assemblages, biomarkers and Rock Eval pyrolysis studies. The dominance of benthonic foraminifera species suggests a shallow marine environment and high percentage of calcareous to arenaceous benthic www.eujournal.org 195 foraminifera indicate high water salinity and hypersline environment. Dysoxic oxygen condition is also prevalent probably because most of the benthic foraminifera recovered are epifauna that live in a reduced oxygen condition. 1.90 wt%, 244 mgHC/gTOC and 429℃ average values of total organic carbon, hydrogen index and Tmax reveal that the Upper Cretaceous shales have relatively fair to good organic matter, predominantly Type II-III kerogen and currently immature. Though three is a trend of an increase in maturity down the hole. All the steranes have uniform distributions (C27>C28>C29), suggesting a relatively higher input from the marine red algae and a low level of land plant contribution to the source organic matter. Pristane/phytane ratios and C29/C27 steranes confirmed the organic matter type to be a Type II/III and anoxic source rock depositional condition as well as a reducing diagenetic system in the sediment water column. The Upper Cretaceous shales in Dahomey Basin can be targeted for exploration as an unconventional petroleum resource.

Biostratigraphy and Facies Analysis of Upper Valanginian-Upper Hauterivian (Sarmord Formation) in Maten Anticline, Northern Iraq

Biostratigraphical and sedimentological study of the Sarmord Formation (Upper Valanginian - Upper Hauterivian) at the southern limb of Maten anticline is conducted within a well-exposed section. The formation is composed of marl, marly limestone, limestone, and dolostone, which yielded moderately diversified benthonic foraminiferal fauna, green algae, echinoderms, gastropods and some bioclast. The stratigraphic distribution of the benthonic species permits the recognition of two well-defined biozones. These are Everticyclammina kelleri Assemblage Zone, which represents the Late Valanginian age and Pseudocyclammina lituus Assemblage Zone, indicating Hauterivian age. These larger benthonic foraminiferal biozones are correlated with other zonal schemes inside and outside of Iraq, which indicates that the age of the Sarmord Formation in Maten anticline extends from Late Valanginian to Late Hauterivian age. The Sarmord Formation in the studied section is composed of limestone, dolomite, marl and conglomerate lithofacies types. Limestone lithofacies is represented by lime wackestone microfacies. According to the characteristic features of these facies, the depositional environments extend from tidal flat to shallow open marine environments.

Foraminiferal Biozonation of Late Eocene - Early Oligocene sediments of BC-1 well, Onshore, Western Niger Delta Basin, Nigeria

Foraminiferal analysis was carried out on forty (40) ditch cutting samples from BC-1 well in the Onshore, Western Niger Delta at depth intervals of 5590 ft. - 8300 ft. Lithologic description of the samples together with the gamma ray log analytical data indicated the presence of four lithostratigraphic units composed of shale, sandstone, sandy shale and shaly sand corresponding to the continental Benin and paralic Agbada Formations. A total of twelve (12) species defined into eleven (11) genera, six (6) subfamilies and eleven (11) families were recovered. Benthonic and planktonic foraminiferal species constitute approximately 82 % and 18 % respectively. The calcareous benthics make up 44.4 % while the arenaceous benthics representing 37.7% of the total foraminiferal assemblages. Foraminiferal index marker species - Globorotalia opima nana, Nonion oyae, Cassigerinella chipollensis and Spiroplectammina wrightiirevealed that the age of the studied well is from Late Eocene - Early Oligocene epoch. This indicated that both the planktonic and benthonic foraminiferal recovered from the well contained the transition between the Priabonian and the Rupelian age. Three (3) informal foraminiferal zone were established - Nonion oyae zone, Cassigerinella chipollensis zone and undiagnostic zone. The zones compares with foraminiferal markers species whose stratigraphic ranges are well established in the Niger Delta and globally.
 Keyword: Lithostratigraphic units, Agbada Formation, Eocene, Oligocene and Biozone.

Macroalgae associated with aerial roots of <i>Rhizophora mangle</i> in Islas del Rosario, Colombia, Southwestern Caribbean

The roots of the red mangrove, Rhizophora mangle, provide a nursery habitat for many species, due to the tridimensional structure they provide, which delimits an area difficult to access to large predators. Moreover, they provide a hard substrate for many benthonic species, which attach to the roots and contribute to the tridimensional structure of the ecosystem. Among these organisms, there are several macroalgae, which contribute to the primary productivity of the ecosystem and provide food and shelter to herbivores. In the present study we identified the macroalgae associated with the roots of Rhizophora mangle, in Cholón beach, Rosario Islands National Park, Caribbean Colombia. We report a total of 36 species of macroalgae: 21 Rhodophyta, eleven Chlorophyta, and four Phaeophyceae. Of these, 19 are new records for the islands, and six are new records for Colombia. This is the first study on the macroalgae associated with mangrove roots in the Colombian Caribbean, and it highlights both the high diversity of the marine flora of the Southwestern Caribbean, as well as the paucity of studies on the topic.

Geochemistry and paleoecology of shales from the Cenomanian-Turonian Afowo formation Dahomey Basin, Nigeria: Implication for provenance and paleoenvironments

Cenomanian – Turonian (CT) Afowo shales selected from offshore X, and coastline Orimedu-1 and Ise-2 exploratory wells in the Dahomey Basin, southwestern Nigeria, were analyzed for foraminifera, major oxide and trace elements to evaluate their provenance and paleoenvironments.The hydrocarbon rich calcareous CT shale is about 100m thick in the coastline area and 300m thick in offshore area with abundant of marine planktonic and benthonic foraminifera. Benthonic species were significantly present in the coastline wells suggesting a shallow marine condition probably a neritic to inner shelf environments while abundant deep water Rotaliporid sp. and shallow water fauna heterohelix sp. in X well suggest inner shelf to bathyal (ca. >350 m) depositional environments.SiO2 and Al2O3 are the most abundant oxides of CT shale with average value of 46.4% and 12.7% in X, 57.1% and 15.65% in Orimedu-1 and 55.3% and 13.1% in Ise-2 respectively suggesting high influx of terrigenous and argillaceous sediments at the coastal area. Average Al2O3/TiO2 of 19.2 in X, 17.8 in Orimedu-1 and 19.3 in Ise-2 indicates that the sediments were sourced from intermediate igneous rock. Favorable oxic conditions for chemical weathering is more pronounce in the manganese concentration of 658–937 ppm in Orimedu-1 and 829–838 ppm in Ise-2 than 364–604 ppm in the shales from X well. Their degree of weathering estimated from chemical index of alteration (CIA) averaging 97 in the coastline wells is higher than 61 in X well, thus indicating high degree of oxidation in the depositional environments. Vanadium to nickel ratio ranging from 2.88 to 5.0 in X well suggest mixed marine and terrigenous source under dysoxic to oxic conditions for the shales while 0.48–1.2 values in Orimedu-1 further indicates a prevailing oxidizing condition at the time of deposition.Dysoxic-oxic and moderate deep-water conditions were more favorable in the offshore area and probably a significant paleo-factor for organic matter preservation of CT shales in the basin.

Comparison between properties of dorsal and ventral skin mucus in Senegalese sole: Response to an acute stress

Intensive culture of Senegalese sole, Solea senegalensis, represents an option to diversify Mediterranean aquaculture. As a flatfish species, the fish body presents marked asymmetry between the dorsal or ocular side and the ventral or blind side. Taking into account that different surroundings come into contact with each side, in the present study we aimed to compare the properties of skin mucus from both sides, which is the most external barrier and protection for the fish. Skin mucus has recently been proposed as a novel minimally invasive target for the study of physiological responses. Here, a group of ten Senegalese sole were used to measure basal mucus parameters; then four additional groups of ten specimens each were used to study a hypoxia stress challenge (post-stress groups: 15 min-PS, 1 h-PS, 6 h-PS and 24 h-PS), consisting of a 3-minute air exposure. Physicochemical parameters (viscosity, osmolality, pH and main osmotic ions) were analysed in dorsal and ventral mucus. Thereby, mucus components related to stress responses such as cortisol, glucose, lactate, soluble protein and antioxidant power, were measured and compared between the mucus types and in response to hypoxia. Rheograms revealed similar non-Newtonian behaviour of dorsal and ventral mucus viscosities, which suddenly increased in the 15 min-PS group, thus providing fish with immediate insulating and mechanical protection. However, ventral side viscosity of the 24 h-PS group was lower than basal values and its functionality was compromised. Whereas chemical parameters did not differ between sides or in response to hypoxia, components that are soluble in mucus showed asymmetry with soluble protein and lactate being twofold higher in ventral mucus. The classical stress response of increased plasma cortisol accompanying glucose and lactate release was observed. In parallel, mucus glucose and lactate showed rapid but transitory exudation in the 15 min-PS group, while cortisol was detected at minimal levels in skin mucus, and therefore is not recommended as a mucus indicator for this species. Mucus-soluble protein also rose in the 15 min-PS group, which indicates greater exudation of defensive-related proteins. Finally, the antioxidant power of dorsal mucus increased and accumulated, without returning to basal levels. All these findings indicate that flatfish skin mucus properties depend on animal side, and further studies will be necessary to elucidate whether other mucus defensive parameters show this asymmetry and their relevance in these benthonic species.

Biostratigraphic Analysis of the Cretaceous Abeokuta Group in the Eastern Dahomey Basin, Southwestern Nigeria

Shales of the Abeokuta Group in the Dahomey Basin yielded abundant foraminiferal tests. The study investigated sediments from three wells that were drilled for petroleum exploration: Well – X located in the offshore deep water, Orimedu-1 and Ise-2 in the coastline region to establish their Cretaceous biostratigraphic units through planktonic foraminiferal zonation. Calcareous benthonic foraminifers occur abundantly and consistently throughout the sequences in the three wells while planktonic foraminifera are more abundant in the Well X than those in the Orimedu-1 and Ise-2.The identified planktonic foraminiferal species are: Rotalipora greenhornesis, Rotalipora cushmani, Dicarinella primitiva, Praeglobotruncana helvetica, Marginotruncana sp. Heldbergella delrionensis, Helbergella planispira, Hedbergella simplex, Whitenella inonata, Whitenella baltica, Globotruncana aegytiaca, Globotruncana sp., Heterohelix reymenti, Heterohelix moremani, Heterohelix globulosa, Abathomphalus mayaroensis and occurrence of Orthokarstenina oyea, Ammobaculites corprolithiformis, Ammobaculities sp and Bolivina sp. Calcareous benthonic foraminiferal species were more abundant than the planktonic species in Orimedu-1 and Ise-2 wells. The benthonic species decrease drastically in the well-X offshore deep water where the planktonic species were most abundant. This trend may suggest an increasing water depth from near coastline to offshore regions in the Cretaceous times.Six planktonic foraminiferal zones were recognised across the three exploratory wells. These include Rotalipora greenhornesis (middle – late Cenomanian), Helvetoglobotruncana helvetica (early – late Turonian), Marginotruncana pseudolinneiana (late Turonian), Marginotruncana renzi (Coniacian – Santonian), Globotruncana calcarata (late Santonian – early Campanian) and Globotruncana aegytiaca (Maastrichtian) Zones. The Rotalipora greenhornesis and Praeglobotruncanae helvetica Zones (Cenomanian – Turonian) were correlated with the standard zones in the Tethyan regions.The Well-X indeed penetrated older Cenomanian to Turonian intervals in the investigated wells, thereby confirming the presence of older marine sequences in the Eastern Dahomey Basin contrary to previous suppositions.

Biostratigraphy and paleoenvironmental setting of the Lower Miocene succession at the west central Sinai, Egypt

Paleoenvironmental setting for the Lower Miocene successions exposed in a Wadi Gharandal can be interpreted using the integration of the lithologic characters and its foraminiferal association. Forty six agglutinated and seventy calcareous benthonic species has helped in segregate and distinguish six ecozones. Three transgressions (outer neritic to bathyal) and regressions (inner neritic and coastal) phases constitute three sedimentary cycles were recorded; the first transgression came with the deposition of the middle part of Mheiherrat Member; the second occurred during the deposition of the lower part of Hawara Member; while last one begins with the upper part of Asal Member. A great sea regression took place at the end of the Burdigalian forming an erosional surface, which represented by clastic sediments (sandstone lenses and pockets) and characterized by the absence of the microfaunal contents (foraminifera) followed by an anhydrite bed indicates a lagoonal environment for the lower part of Kareem Formation. The members of Rubies Formation are distinctively recognized and stratigraphically reconstructed based on its lithologic characters. Thirty-two planktonic foraminiferal species are also identified from the Aquitanian- Burdigalian successions that used to subdivide the studied rocks into three interval zoneszones (Globigerinoides primordius Zone; Globigerinoides altiaperturus Zone, Globigerinoides trilobus Zone) and one Barren Zone; these zones are correlated world wide with the standard international scheme of planktonic foraminiferal zoneszones and those recorded from neighboring areas.

Foraminifera spatial analysis as bioindicator in Java Sea to Flores Sea

Foraminifera is potential bioindicator to understand the modern and ancient marine environment and have been widely used as bioindicator. Java Sea to Flores Sea are productive area influenced by physical and chemical reactions from nature and human activity, so that their characteristics are important to recognize. The aim of this research is to determine oceanography condition of Java Sea to Flores Sea covers the depth, temperature, thermocline, and upwelling according to foraminifera analysis. The method used were inventory and species analysis from 12 stations along study area. The analysis was conducted based on species and abundance. Foraminifera species which are warm water bioindicators are Globigerinoides rubra and Globigerinoides sacculifera, upwelling bioindicators are Globigerina bulloides and Globorotalia menardii, and shallow thermocline bioindicators are Pulleniatina obliqueloculata and Neogloboquadrina dutertrei. The result show that Java Sea has more benthonic species and abundance because of its shallow depth while Flores Sea has more planktonic species and abundance because of its deep depth and part of open ocean. In Flores Sea the abundance of warm water species bioindicators fall significantly and high abundance of upwelling and shallow thermocline species bioindicators indicates that there are upwelling phenomenon with shallow thermocline, thin mix layer, and high productivity.

The isopod Eurydice spinigera and the chaetognath Flaccisagitta enflata: How habitat affects bioaccumulation of metals in predaceous marine invertebrates

We analyzed the concentrations of 20 trace elements in Eurydice spinigera (Isopoda) and Flaccisagitta enflata (Chaetognatha), which represent a hyperbenthic and a zooplanktonic marine species respectively, sharing the same predaceous feeding strategy, from a highly productive coastal region (Ligurian Sea, Northwestern Mediterranean). The same elements were also quantified in marine sediments, where geological anomalies were found for arsenic, chromium and nickel. Metal transfer seems to be deeply influenced by different habitats. The carnivorous isopod E. spinigera, which spends most of its lifetime on the seabed, was found to have the highest concentrations of most trace elements, such as Al, As, Cd, Ce, Cr, Fe, La, Mn, Ni, Pb, Se, V and Zn, and consequently have the highest bioaccumulation factors (BAFs). Moreover, the estimation of biota sediment accumulation factors (BSAFs) revealed that cadmium, copper and zinc concentrations were higher in the isopod than in the sediment.Conversely, in the carnivorous chaetognath F. enflata, which is not a benthonic species, the highest levels of copper and tin were found. Moreover, arsenic speciation analysis confirmed the presence of inorganic As (III+V) in E. spinigera. In the context of utilizing a marine organism as a bio-indicator of metal transfer, it is crucial to consider both feeding behavior and feeding habitat.

Mid-Cenozoic ostracod biostratigraphic range extensions and taxonomic notes on selected species from a new Oligocene (Duntroonian–Waitakian) fauna from southern New Zealand

AYRESS, M., ROBINSON, J.H. & LEE, D.E., March 2017. Mid-Cenozoic ostracod biostratigraphic range extensions and taxonomic notes on selected species from a new Oligocene (Duntroonian–Waitakian) fauna from southern New Zealand. Alcheringa 41, 487–498.This paper discusses a highly diverse assemblage of Ostracoda, particularly biostratigraphically useful species, from a richly fossiliferous shallow-marine deposit of late Oligocene age on Cosy Dell farm, near Waimumu, Southland, New Zealand. The ostracod fauna, consisting of 126 species, is yet to be fully analysed, although it is clear that this new window into the nearshore fauna of the mid-Cenozoic provides the earliest records of many characteristic extant New Zealand genera and species, including several species hitherto only known as far back as the early Miocene (Otaian–Altonian New Zealand local Stages). Finding these younger species in an Oligocene deposit was unexpected and indicates that our current knowledge of mid-Cenozoic ostracod age ranges, particularly for nearshore species, is incomplete. Using nannofossils and molluscs, the Cosy Dell deposit is dated as late Oligocene (Duntroonian or lower Waitakian local Stages) in age; therefore, the new ostracod species occurrences described here are considered valid range extensions. Although the biostratigraphic application of the benthonic ostracod species discussed is limited owing to the effects of sedimentary facies and other palaeoenvironmental factors, the ostracod fossil record does include significant extinction and inception events that offer correlative potential for mid-Cenozoic stratigraphical studies. This study identified a need for modern illustration of many species, and we provide scanning electron microscope illustrations of those Cosy Dell taxa previously considered biostratigraphically useful, as support for species identification and associated biostratigraphic conclusions.Michael Ayress [mike.ayress@rpsgroup.com], RPS ichron Group, Gadbrook Business Centre, Northwich CW9 7TN, UK; Jeffrey Robinson [jeffreyhrobinson@yahoo.co.nz] and Daphne Lee [daphne.lee@otago.ac.nz], Geology Department, University of Otago, Dunedin, New Zealand

Bioaccumulation of heavy metals in marine organisms from the Romanian sector of the Black Sea

The aim of this research was to study the accumulation of heavy metals (cadmium - Cd, lead - Pb, chromium - Cr, nickel - Ni, and copper - Cu) from water and sediments into living tissues of relevant marine species from different trophic levels of a food web, representative for shallow waters of the Romanian Black Sea Coast where the main anthropogenic impacts exist. The heavy metals concentrations were analysed by using an Atomic Absorption Spectrometer with graphite furnace, the results being further used to calculate the bioconcentration factors for a few key taxa like green and red algae, molluscs and fishes. Seven sampling sites influenced by anthropogenic pollution sources (municipal wastewater treatment plants and diffuse sources) were considered and a total of 300 samples were analysed for the period 2011-2012, this being the first unitary study for the Romanian Black Sea marine ecosystem. In 2011 and 2012 there were no significant differences between the sampling areas considering the heavy metals concentrations in water. For the sediments significant differences were observed between sampling sites for some heavy metals, namely Pb in 2011 and Pb, Cu and Cd in 2012, the highest concentrations being registered in the southern sector of the Romanian Black Sea shore, where the anthropogenic pollution sources are represented by the harbour and wastewater treatment plants. The values of the bioaccumulation factors (BCFsed) shows that algae are good accumulators for Cu>Pb>Ni>Cr>Cd, in comparison with BCFwater where the order of heavy metal accumulation was different: Cr>Ni>Pb>Cd>Cu. Molluscs have higher bioconcentration factors for Cu and Cd for sediments and for Cu and Ni for water. Rapana venosa accumulated more Cd and Cu. For fishes, Pb, Cu and Ni had the highest values in the tissues of benthonic species Mullus barbatus. In bivalve molluscs and fishes, in the majority of cases, there were not recorded exceeding mean concentrations as compared to the maximum allowed concentrations for Cd and Pb.

Acidobacteria appear to dominate the microbiome of two sympatric Caribbean Sponges and one Zoanthid.

BackgroundMarine invertebrate-associated microbial communities are interesting examples of complex symbiotic systems and are a potential source of biotechnological products.ResultsIn this work, pyrosequencing-based assessment from bacterial community structures of sediments, two sponges, and one zoanthid collected in the Mexican Caribbean was performed. The results suggest that the bacterial diversity at the species level is higher in the sediments than in the animal samples. Analysis of bacterial communities’ structure showed that about two thirds of the bacterial diversity in all the samples belongs to the phyla Acidobacteria and Proteobacteria. The genus Acidobacterium appears to dominate the bacterial community in all the samples, reaching almost 80% in the sponge Hyrtios.ConclusionsOur evidence suggests that the sympatric location of these benthonic species may lead to common bacterial structure features among their bacterial communities. The results may serve as a first insight to formulate hypotheses that lead to more extensive studies of sessile marine organisms’ microbiomes from the Mexican Caribbean.Electronic supplementary materialThe online version of this article (doi:10.1186/0717-6287-47-67) contains supplementary material, which is available to authorized users.

Palaeoenvironment of the lower and middle Miocene successions in the Gulf of Suez region based on both planktonic and benthonic foraminifera

Based on the planktonic and benthonic foraminiferal content the lower and middle Miocene successions at the Gulf of Suez in Egypt have been identified (30 planktonic species and 101 benthonic species), seven paleoecologic parameters are studied, which include; foraminiferal frequency; predominance of the planktonic foraminiferal groups; predominance of benthonic foraminiferal groups, diversity of the foraminiferal species, P/B foraminiferal ratio, A/C foraminiferal ratio and benthonic genus/genera predominance. According to this study, the studied successions are divided into five ecozones. The paleoenvironment of each ecozone is deduced. The deduced paleoenvironments point to outer neritic for the Nukhul formation, middle neritic to inner neritic for the Rudeis formation, inner neritic to littoral for the Kareem formation and littoral neritic for the Belayim formation. A proposed paleobathymetric curve is presented. The interpretation of this curve helped to deduce the tectonic history of the early and middle Miocene in the studied areas.

The impact of Paleocene/ Eocene (P/E) Thermal Maximum (PETM) of some sections in Sinai - Egypt, based on benthonic foraminifera

The present study deals with lithostratigraphy, biostratigraphy and paleoecology of paleocene – Early Eocenebenthonic foraminifera northeast Sinai, Egypt; G. El Falig, G. El Qusaima, G. Holet Abu Senna and G. Um Thamallahave been collected, sampled and studied based on benthonic foraminifera. The measured sections comprises; EsnaFormation and Thebes Formation. The exposed rock units contain rich and high diverse assemblage of benthonicforaminifera that are discussed. They yield 109 foraminiferal benthonic species belonging to 48 genera, 24subfamilies, 25 families, 18 super families, 3 suborder and one order. The investigation of the foraminiferal content ledto the identification of two assemblage zones; the Early - Late Paleocene Neoflabellina - Spiroplectammina -Gavelinella Assemblage Zone and Late Paleocene – Early Eocene Loxostomoides - Cibicidoides - BuliminaAssemblage Zone. During the investigated interval three biofacies with three faunal turnover events have beenidentified in the studied area reflecting a major sea level change. These turnovers are characterized by discontinuousdistribution of species, changes of the relative abundance of species and diversification. The Esna Shale was depositedin middle neritic to upper bathyal environment and Thebes Formation was also deposited in progressively shallowingmiddle neritic environment.

Nukhul Formation in Wadi Baba, southwest Sinai Peninsula, Egypt

ABSTRACTThe Nukhul Formation is the oldest syn-rift rock unit in the Gulf of Suez rift system in Egypt. The age of the formation is inadequately resolved by biostratigraphy and it is generally assigned to the Lower Miocene by stratigraphic position. For this study a surface section was measured and sampled at Wadi Baba, located in the southwestern Sinai Peninsula. It yielded 17 planktonic foraminiferal species and 17 foraminiferal benthonic species. The planktonic foraminiferal assemblage was used to divide the formation into two planktonic foraminiferal zones: (1) Globigerina ciperoensis Zone (O6) of Late Oligocene Chattian age; and (2) Globigerinoides primordius Zone (M1) of Early Miocene Aquitanian age. The two zones coincide with depositional sequences: (1) Chattian Lower Nukhul Sequence, with its upper boundary coinciding with the Chattian/Aquitanian (Oligocene/Miocene) boundary; and (2) Aquitanian Upper Nukhul Sequence, with its upper sequence boundary coinciding with the Aquitanian/Burdigalian boundary.

Reef fish mass mortality event in an isolated island off Brazil, with notes on recent similar events at Ascension, St Helena and Maldives

Events of mass mortality of marine fish have been reported to occur world wide, mainly in coastal regions of continental shelves. Here we report an event at Trindade Island, located 1160 km from the Brazilian coast. Melichthys niger was the species most commonly seen affected. Twenty-four other species were found washed ashore. Victims were demersal (72% of species), pelagic (20%) and benthonic species (8%), comprising eight trophic categories. There is evidence that fish kills have occurred at Trindade since at least the 1990s. Mortality events mainly involving primarily Balistidae (Trindade, Maldives and Ascension), Chaetodontidae (St Helena) and Serranidae (Ascension) have been reported for other isolated oceanic localities with low human occupation. It is possible that blooms of toxic algae, under certain conditions cause cascading intoxication along the trophic web. A second hypothesis is that seasonal upwelling events of anoxic or hypoxic waters may be implicated.

The significance of iron-stained foraminifera off SE Trinidad, West Indies, western central Atlantic Ocean

AbstractEleven samples of seafloor sediment were taken from water depths of 78–90 m within the Savonette Field, off SE Trinidad, western Atlantic Ocean. This surface sediment is relict, having been deposited during an early Holocene transgression. The samples yielded much iron-stained quartz and a rich assemblage of dead foraminifera, of which 75% of planktonic foraminifera were stained with iron, as was 66.5% of the calcareous benthonic foraminiferal assemblage. The fauna, both iron-stained and unstained, was dominated byCibicidoidesex. gr.pseudoungerianus, and is concluded, despite the proximity of the Orinoco Delta, to be equivalent to a relictCibicidoidesbiofacies in carbonate-rich areas of the Gulf of Mexico. Staining was by limonite and hematite. Differing percentages of calcareous benthonic species had been stained with iron, ANOVA revealing three groups of species within which the mean percentage of iron-stained specimens per sample did not differ: (a)Globocassidulina subglobosaandHanzawaia concentrica; (b)Amphistegina gibbosa, Cassidulina norcrossi australis Cibicioidesex. gr.pseudoungerianus,C. io,Elphidium translucensandQuinqueloculina lamarckiana; and (c)Eponides antillarumandE. repandus. It is concluded that species differ in their susceptibility to iron staining, and that planktonic foraminifera are more susceptible than most benthonic species. Although waters off northern South America are turbid and the photic zone only ~25 m deep, the relict assemblage contained 8.4% algal symbiont-bearing foraminifera (especiallyA. gibbosaandE. translucens) that would be limited to the photic zone. These are thought to have lived at a time early in the Holocene transgression when sequestration of sediment within the Orinoco delta rendered the water sufficiently clear for viable populations of symbiont-bearing foraminifera. Should iron-stained foraminifera prove to be restricted to transgressive systems tracts, this would make them a useful sequence stratigraphic tool.

Análise Sedimentar e Micropaleontológica (Foraminíferos) de Seções Quaternárias do Talude Continental Superior do Norte da Bahia, Brasil

Sediment from four cores of the north part of the continental upper slope, Bahia State, consist predominantly of siliciclastic mud in its bottom and carbonatic mud in the top of the majority of the studied cores. The sediment color varies from light olive gray to brownish black. The sediments are mainly composed of foraminifera, mollusk fragments, coralline algae debris, plant fragments and quartz grains. The following major foraminifera benthonic species were recorded in the studied cores: Cibicides pseudoungerianus, Bulimina marginata, Amphistegina lessonii, Cassidulina laevigata, Bolivina subaenariensis, Uvigerina peregrina. The following major foraminifera planctonic species are frequent in the cores: Globigerinoides ruber, Globigerina bulloides, Orbulina universa, Globigerinoides trilobus, G. elongatus, Globigerina quinqueloba, Globigerinoides ruber f. pyramidalis. The siliciclastic sediment (higher quartz percentage) in the core bottom, suggests that sedimentation occurred with strong continental influence, indicating proximity to the coast line. The benthonic foraminifera predominance in the bottom cores and the higher planctonic frequency toward the top cores is an indicative of the sea-level oscilation events during Quaternary time.