Palaeoenvironments and palaeoclimates of the Quaternary molluscan faunas from the coastal area of Bahía Vera-Camarones (Chubut, Patagonia)

Quaternary molluscs are useful tools as indicators of environmental and climatic changes through time. The Patagonian coastal area exhibits a series of Quaternary marine terraces (MT) at various elevations with a well-preserved molluscan fauna. The assemblages from Mid- to Late Pleistocene and Holocene raised beach deposits exposed between Bahía Vera and Bahía Camarones (44.2°S-45°S) were examined, and systematic, palaeoecological and palaeobiogeographical aspects were reviewed and updated in terms of interpretation of the littoral area and biotic responses to climate changes. Collections at 10 fossiliferous localities and four modern sites of the adjacent nearshore show that molluscs (41 taxa: 24 gastropods and 17 bivalves) represent 91% of the total faunal content. Identification of the typical taxa for at least four sea-level highstands was based on the occurrence, relative abundance, species richness, and diversity indices (Margaleff's; Sannon Weaver's). Variations between terraces MTIII (Camarones, higher than + 30 m, probably ca. 400 ka), IV (Punta Pescadero and Camarones,+ 22-29 m, 178-239 ka), V (Bahía Vera, Punta Pescadero, Camarones,+ 16-18 m, 92-135 ka) and VI (Punta Lobería, Punta Pescadero, Camarones,+ 6-12 m, 2.5-8 ka) add to a better understanding of palaeoenvironments and palaeoclimates linked to sea-level highstands since MOIS11. Their original habitat was typical of rocky-shore, high-energy and euhaline waters, similar to the modern conditions of adjacent benthic communities. The most characteristic taxa are: Patinigera deaurata (Gm.), Fissurella spp., Crepidula protea d'Orb., C. aculeata (Gm.), C. cf. unguiformis Lam., Natica isabelleana d'Orb., Trochita pileus (Lam.), Buccinanops spp., Pareuthria plumbea (Philippi), Acanthina monodon (Pallas) and Trophon spp. (Gastropoda); Brachidontes purpuratus (Lam.), Protothaca antiqua (King), Clausinella gayi (Hupé), Mactra aff. patagonica (d'Orb.) and Ostrea tehuelcha (Feruglio). New records in this area for the Late Pleistocene are: C. aculeata (Gm.), C. onyx Sow., C. protea d'Orb., T. patagonica (d'Orb.), N. isabelleana (d'Orb.), B. rodriguezi (d'Orb.), A. tehuelchus (d'Orb.) and C. gayi (Hupé). Ostrea tehuelcha d'Orb. became extinct and Tegula atra (Lesson), N. isabelleana (d'Orb.), B. rodriguezi (d'Orb.), C. patagonica (d'Orb.) and D. vilardeboana (d'Orb.) migrated into the area. Exclusive for MTIII (MOIS11) are Pectinidae indet., Ostrea tehuelcha and Mactra cf. patagonica d'Orb. which, together with other taxa (i.e., Corbula patagonica, Diplodonta vilardeboana), suggest warmer sea surface temperature (SST) than at present. Typical of MTIV (MOIS7) are T. atra, biggest P. antiqua (King), and Veneroida indet. The assemblage from MTV (MOIS5c?, 5a?), T. atra, T. patagonica, C. dilatata Lamk., M. edulis Linn., B. purpuratus, P. antiqua, and P. rostratus (Koch), is not indicative of a climatic optimum and thus of the Last Interglacial maximum highstand (MOIS5e). MTVI (MOIS1) is characterized by B. cf. purpuratus, N. (Patinigera) magellanica (Gm.), N. (P.) deaurata (Gm.), Trophon geversianus (Pallas), B. purpuratus, and Aulacomya atra (Molina). N. delicatissima (Strebel), Chlamys sp., Panopea abbreviata, and Lyonsia sp. exclusively occur in the modern nearshore. According to the global isotope curve, MOIS5e highstand (125 ka BP) was the warmest since the Mid-Pleistocene. The innermost MTIII assemblage provides an opportunity to hypothesize that along the eastern coast of South America the corresponding highstand (probably MOIS11, ca. 400 ka BP ?) belongs to the warmest of the Pleistocene interglacials preserved, as proposed earlier for the Chilean coast (Ortlieb et al., 1996). This assemblage could be correlated with the Belgranense of the Bonaerensian littoral. The Holocene Climatic Optimum (5-8 ka) is confirmed to have influenced the littoral biota. A slightly higher SST (1-3 °C) implied atmospheric and palaeoceanographic changes, with a southwards shift of the dominant warm (Brazilian) and cool (Malvinas = Falkland) currents along the SWAtlantic and, consequently, of the Argentinean and Magellanean marine zoogeographical provinces.     

Estudio paleoecológico de Foraminíferos de testigos del Holoceno de Golfo Nuevo (Patagonia, Argentina)

A micropaleontological study (Order Foraminiferida) was conducted on two Holocene cores from Golfo Nuevo (Patagonia, Argentina). The most abundant species are Buccellaperuviana f. campsi (Boltovskoy) and Bulimina patagonica (d’Orbigny), suggesting an inner-shelf environment. Qualitative and quantitative analyses indicate the paleoecological and paleoenvironmental variations along cores. A transition from normal marine conditions of the inner shelf during the Middle Holocene (ca. 8160-7700 years B.P.) to marginal marine conditions in the Late Holocene (ca. 1890 years B.P.) is inferred. This transition was accompanied by lower oxygen levels than the current values in Golfo Nuevo. These variations may have been due to an increase in precipitation near the study zone and a rise in sea level caused by an improvement in the climatic conditions related to the Climate Optimum (ca. 7000 years B.P.). These new conditions of higher temperature and lower salinity of the surface waters may have hindered deep-water renewal, producing a change in the circulation dynamics of the gulf and causing a reducing environment.     

New bivalve burrows from the mid-Holocene of northeastern Buenos Aires Province (Argentina): ichnotaxonomy and ethology

Oblongichnus vulpesi n. isp. is herein described as amygdaloid, oval or cleft-shaped burrows with a lining of variable thickness and an oblong to quadrangular elongated shaft from the mid-Holocene of the Destacamento Río Salado Member. Valves of the solenid bivalve species Solen tehuelchus were found within the burrows, indicating that this razor clam is the tracemaker. This new finding corroborates the validity of Oblongichnus and previous interpretation that the burrow was produced by infaunal, filter feeding bivalves with a foot of very limited horizontal movements. We found that the origin of oblong elongate bivalves may be dated back to the Ordovician, while an infaunal radiation likely occurred during late Paleozoic. We interpret that O. vulpesi was made in a moderate energy subtidal marine setting during the last marine highstand.     

Haemolytic and cytotoxic action of latarcin Ltc2a

Activity and action mechanisms of latarcin 2a (Ltc2a), an antimicrobial peptide from the venom of the spider Lachesana tarabaevi (Zodariidae), were studied in vitro on human cells. Cytotoxicity of Ltc2a for erythrocytes (EC₅₀ = 3.4 μM), leukocytes (EC₅₀ = 19.5 μM) and erythroleukemia K562 cells (EC₅₀ = 3.3 μM) has been found to be primary related to plasma membrane destabilization. Using fluorescently labeled Ltc2a, three common features are found for erythrocytes and K562 cells: pronounced inhomogeneity of cellular response to Ltc2a; complex multistage character of Ltc2a-cell interactions; a positive feedback between Ltc2a binding to plasma membrane and development of toxic effects. Discocyte - echinocyte - spherocyte - ghost is a sequence of Ltc2a-induced transformations of erythrocytes that are accompanied by multistage enhancement of Ltc2a membrane binding, formation of small (ca. 2.0 nm) membrane pores, osmotic imbalance development and reorganization of the pores into large (ca. 13 nm) membrane openings that are preserved in ghosts. Ltc2a induces membrane blebbing and swelling of K562 cells followed by cell death. Cytotoxic action occurs through formation of membrane pores (ca. 3.7 nm) which show greater permeability for anionic than cationic molecules. The pore formation is accompanied with self-assisted Ltc2a internalization and accumulation in mitochondria, mitochondrion inactivation and apoptosis-independent phosphatidylserine externalization.     

Contribution à la connaissance des bivalves du Turonien d’Owendo dans le bassin côtier nord gabonais

The study of bivalves collected from Turonian deposits of Owendo region, within Gabonese coastal north basin, allows to identify 9 species belonging to 9 genera: Aphrodina dutrugei (Coquand 1862), Brachidontes eoexustus Klein and Ferreira 1979, Crassatella cf. pyrenaica d’Orbigny 1843, Entolium exilis (Reuss, 1854), Exogyra sp., Lopha sp., Mytilus cf. lineatus d’Orbigny 1844, Pholadomya adversa Riedel 1932 and Rastellum sp. Excepted A. dutrugei and P. adversa, which are known in Turonian localities of Gabon, other species are found here for the first time in Gabonese coastal basin. This is the same for genera named Brachidontes Swainson 1840, Entolium Meek, 1865 and Mytilus Linnée 1758. In Gabonese coastal basin, the stratigraphic and geographic ranges of the Crassatella genus are extended in Turonian and Owendo region respectively. The bivalve assemblage is dominated by specimens of Aphrodina genus. The bivalve specific diversity of Owendo region increase from 3 to 12 species.     

Mass spectrometric U-series dating of Huanglong Cave in Hubei Province,central China: Evidence for early presence of modern humans in eastern Asia

Most researchers believe that anatomically modern humans (AMH) first appeared in Africa 160-190 ka ago, and would not have reached eastern Asia until ∼50 ka ago. However, the credibility of these scenarios might have been compromised by a largely inaccurate and compressed chronological framework previously established for hominin fossils found in China. Recently there has been a growing body of evidence indicating the possible presence of AMH in eastern Asia ca. 100 ka ago or even earlier. Here we report high-precision mass spectrometric U-series dating of intercalated flowstone samples from Huanglong Cave, a recently discovered Late Pleistocene hominin site in northern Hubei Province, central China. Systematic excavations there have led to the in situ discovery of seven hominin teeth and dozens of stone and bone artifacts. The U-series dates on localized thin flowstone formations bracket the hominin specimens between 81 and 101 ka, currently the most narrow time span for all AMH beyond 45 ka in China, if the assignment of the hominin teeth to modern Homo sapiens holds. Alternatively this study provides further evidence for the early presence of an AMH morphology in China, through either independent evolution of local archaic populations or their assimilation with incoming AMH. Along with recent dating results for hominin samples from Homo erectus to AMH, a new extended and continuous timeline for Chinese hominin fossils is taking shape, which warrants a reconstruction of human evolution, especially the origins of modern humans in eastern Asia.     

Antimicrobial activities of Dilobeia thouarsii Roemer and Schulte,a traditional medicinal plant from Madagascar

The leaves of Dilobeia thouarsii (Roemer and Schulte), a tree that is endemic to Madagascar (Proteaceae), are used in traditional Malagasy medicine to treat bacterial skin infections and wounds. This study investigated the in vitro antibacterial activities of D. thouarsii leaf extracts and identified the bioactive compounds with the aim of providing a scientific basis for its use against skin diseases. Using broth microdilution method for leaf crude extract and its compounds, we investigated inhibition of the growth of Bacillus cereus, Bacillus megaterium, Staphylococcus aureus, Enterococcus faecalis, Vibrio harveyi, Vibrio fisheri, Salmonella Typhimurium, Salmonella antarctica, Escherichia coli, and Klebsiella pneumoniae. The two purified phenolic compounds from leaf ethyl acetate extracts (1, 2) were found to be more active than the crude extract itself. The structure of the two compounds was elucidated by NMR and mass spectrometry: compound 1 was identified as 4-aminophenol and compound 2 as 4-hydroxybenzaldehyde. A marked inhibitory effect (MIC < 0.1 mg/ml) was found against S. aureus, which is a major agent in skin infections. We observed moderate activities (MIC values of between 0.1 and 0.5 mg/ml) for E. faecalis, Vibrio spp., and Bacillus spp. Neither compound was active against Salmonella spp., E. coli and K. pneumoniae (MICs > 1 mg/ml). To conclude, the high antimicrobial activity of D. thouarsii leaf extracts against S. aureus supports its traditional use to treat skin infections.     

Characterization of a toxic Pseudo-nitzschia spp. bloom in the Northern Gulf of Mexico associated with domoic acid accumulation in fish

A toxic bloom of Pseudo-nitzschia spp. was observed in the Alabama coastal waters of the northern Gulf of Mexico (NGOM) in June 2009 that resulted in the accumulation of domoic acid (DA) in fish. The bloom initiated following a large storm event that likely caused increased groundwater discharge 16–20 days prior to peak densities. Eleven sites, located in littoral shoreline waters and inshore embayments spanning the entire Alabama NGOM coastline, were sampled during peak densities to assess Pseudo-nitzschia species composition and toxicity, and associated water-quality parameters. Small fish (0.27–11.9 g body weight) were collected at six of these sites for analysis of DA content. High Pseudo-nitzschia spp. densities (8.27 × 10⁴–5.05 × 10⁶ cell l⁻¹) were detected at eight sites located in the littoral shoreline and particulate DA was detected at six of these littoral sites (48.0–540 pg ml⁻¹). The bloom consisted primarily (>90%) of Pseudo-nitzschia subfraudulenta, a species previously characterized as forming only a minor component of Pseudo-nitzschia assemblages and not known to produce DA. Pseudo-nitzschia spp. were at low densities or not detected at the inshore sites and DA was detected at these sites. Pseudo-nitzschia spp. density varied along an estuarine gradient, with greater densities occurring in the most saline, clear, and nutrient-poor waters. Cell density was strongly and negatively correlated with silicate (Si) concentrations and the ratios of silicate to dissolved inorganic nitrogen and phosphate (Si:DIN and Si:PO₄). Cell toxin quota was negatively correlated with phosphate, and strongly and positively correlated with the ratio of total nitrogen to total phosphorus (TN:TP). These relationships are consistent with previous observations that indicate Pseudo-nitzschia spp. density and toxicity are likely to be greater in high salinity, high irradiance, and nutrient-poor waters. DA was detected in 128 of 131 (98%) of the fish collected, which included seven primary and secondary consumer species. This is the first demonstration of trophic transfer of DA in this region of the NGOM, indicating that toxic blooms of Pseudo-nitzschia spp. in Alabama coastal waters have the potential to transfer DA to recreationally and commercially important fish species.     

Foraminiferal oxygen and carbon isotopes during the last 34 kyr off northern Japan,northwestern Pacific

Oxygen and carbon isotopes of foraminifera were analyzed in core PC4, water depth 1366 m, off northern Japan, near the east side of the Tsugaru Strait (130 m depth) between the open northwestern Pacific Ocean and the Japan Sea. At present, the site is at the confluence of the Tsugaru Warm Current which flows eastwards out of the Sea of Japan through the Tsugaru Strait, the subarctic Oyashio Current and the subtropic Kuroshio Current. During the Last Glacial Maximum (LGM), the Oyashio Current penetrated further to the South and outflow from the Japan Sea was restricted by glacio-eustatic sea level lowering.The isotopic values of the planktic foraminifer Neogloboquadrina pachyderma (sinistral) and the benthic foraminifer Uvigerina akitaensis reflect rapid millennial-scale paleoceanographic changes between 34 and 6 ka. Hydrographic changes during deglaciation were related to events at high northern latitudes, but Holocene hydrographic changes were dominated by local effects, such as the development of the outflow of the Tsugaru Warm Current. High values of planktic δ¹⁸O during the LGM reflect the southward advance of the Oyashio Current. These values decreased by 0.3‰ from 19.4 to 18.9 ka, then increased by 0.5‰ at 18 ka, with highest values between 17.5 and 15 ka. The δ¹⁸O oscillations between 19.4 and 15 ka may reflect millennial-scale warm–cold oscillations during Heinrich event 1. Planktic microfossil data indicate that cold Oyashio waters flowed from the northwestern Pacific into the Japan Sea via the Tsugaru Strait between 17 and 16 ka, consistent with the occurrence of the highest planktic δ¹⁸O values in core PC4. Planktic δ¹⁸O values rapidly decreased by 0.9‰ at 15 ka, possibly reflecting the effects of both a rapid increase in fresh water flux and rising temperatures in the subarctic North Pacific. During the Younger Dryas, cold event planktic δ¹⁸O values increased by 0.5‰, followed by a gradual decrease by 1‰ from the early to middle Holocene, reflecting a gradual increase in eastward outflow via the Tsugaru Strait with sea level rise. Both planktic and benthic foraminiferal δ¹³C values oscillated between 34 and 10 ka, at relatively large amplitudes (about 0.5‰), then remained relatively stable during the last 10 kyr. Several negative planktic and benthic (∼ − 0.7‰) δ¹³C excursions were present in sediment dated between the precipitation of secondary carbonates during episodic methane release possibly associated with methane release from continental margin sediments.     

Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus

The ability of vertical flow (VF) constructed wetland systems to treat high-strength (ca. 300 mg L^?1 of COD and ca. 300 mg L^?1 total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6 m) were used: three units were planted with Typha angustifolia L., another three units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80 mm d^?1. Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water. The high evapotranspirative water loss from the Cyperus systems resulted in higher effluent concentrations of COD and total-P, but the mass removal of COD did not differ significantly between planted and unplanted systems. Average mass removal rates of COD, TKN and total-P at a HLR of 80 mm d^?1 were 17.8, 15.4 and 0.69 g m^?2 d^?1. The first-order removal rate constants at a HLR of 80 mm d^?1 for COD, TKN and total-P were 49.8, 30.1 and 13.5 m year^?1, respectively, which is in the higher range of k-values reported in the literature. The oxygen transfer rates were ca. 80 g m^?2 d^?1 in the planted systems as opposed to ca. 60 g m^?2 d^?1 in the unplanted systems. The number of Nitrosomonas was two to three orders of magnitude higher in the planted systems compared to the unplanted systems. Planted systems thus had significantly higher removal rates of nitrogen and phosphorus, higher oxygen transfer rates, and higher quantities of ammonia-oxidizing bacteria. None of the systems did, however, fully nitrify the wastewater, even at low loading rates. The vertical filters did not provide sufficient contact time between the wastewater and the biofilm on the gravel medium of the filters probably because of the shallow bed depth (0.6 m) and the coarse texture of the gravel. It is concluded that vertical flow constructed wetland systems have a high capacity to treat high-strength wastewater in tropical climates. The gravel and sand matrix of the vertical filter must, however, be designed in a way so that the pulse-loaded wastewater can pass through the filter medium at a speed that will allow the water to drain before the next dose arrives whilst at the same time holding the water back long enough to allow sufficient contact with the biofilm on the filter medium.     

Exposure of Agaricus bisporus to Trichoderma aggressivum f. europaeum leads to growth inhibition and induction of an oxidative stress response

Green mould disease of mushroom, Agaricus bisporus,is caused by Trichodermaspecies and can result in substantial crop losses.Label free proteomic analysis of changes in the abundance of A. bisporusproteins following exposure to T. aggressivumsupernatantin vitroindicated increased abundance of proteins associated with an oxidative stress response (zinc ion binding (+6.6 fold); peroxidase activity (5.3-fold); carboxylic ester hydrolase (+2.4 fold); dipeptidase (+3.2 fold); [2Fe-2S] cluster assembly (+3.3 fold)). Proteins that decreased in relative abundance were associated with growth: structural constituent of ribosome, translation (-12 fold), deadenylation-dependent decapping of nuclear-transcribed mRNA (-3.4 fold), and small GTPase mediated signal transduction (-2.6 fold). In vivoanalysis revealed that 10^-4 T. aggressivuminoculum decreased the mushroom yield by 29% to 56% and 10^-3 T. aggressivuminoculum decreased the mushroom yield by 68% to 100%. Proteins that increased in abundance in A. bisporusin vivofollowing exposure to T. aggressivumindicated an oxidative stress response and included proteins with pyruvate kinase activity (+2.6 fold) and hydrolase activity (+2.1 fold)). The results indicate that exposure of A. bisporusmycelium to T. aggressivum in vitroand in vivoresulted in an oxidative stress response and reduction in growth.     

Microalgal adaptation to a stressful environment (acidic,metal-rich mine waters) could be due to selection of pre-selective mutants originating in non-extreme environments

At least six species of eukaryotic microalgae inhabit the acidic (pH 2.4–2.7), metal-rich mine waters from ponds in the copper mine district of Mynydd Parys (N Wales, UK). Consequently, these ponds constitute interesting natural laboratories for analysis of adaptation by microalgae to extremely stressful conditions. To distinguish between the pre-selective and post-selective origin of adaptation processes that allow the existence of microalgae in these ponds, a Luria-Delbrück fluctuation analysis was performed with the chlorophycean Dictyosphaerium chlorelloides isolated from non-acidic waters. In this analysis, natural Mynydd Parys pond water (MPW) was used as selective factor. Pre-selective, resistant D. chlorelloides cells appeared with a frequency of 1.6 × 10^?6 per cell per generation. MPW-resistant mutants, with a diminished Malthusian fitness, are maintained in non-extreme waters as the result of a balance between new MPW-resistant cells arising by mutation and MPW-resistant mutants eliminated by natural selection (equilibrium at ca. 19 MPW-resistant per 10⁷ wild-type cells). We propose that the microalgae inhabiting these stressful ponds could be the descendents of chance mutants that arrived in the past or are even arriving at the present.     

Redox potential of chlorophyll d in vitro

Chlorophyll (Chl) d is a major chlorophyll in a novel oxygenic prokaryote Acaryochloris marina. Here we first report the redox potential of Chl d in vitro. The oxidation potential of Chl d was + 0.88 V vs. SHE in acetonitrile; the value was higher than that of Chl a (+ 0.81 V) and lower than that of Chl b (+ 0.94 V). The oxidation potential order, Chl b > Chl d > Chl a, can be explained by inductive effect of substituent groups on the conjugated π-electron system on the macrocycle. Corresponding pheophytins showed the same order; Phe b (+ 1.25 V) > Phe d (+ 1.21 V) > Phe a (+ 1.14 V), but the values were significantly higher than those of Chls, which are rationalized in terms of an electron density decrease in the π-system by the replacement of magnesium with more electronegative hydrogen. Consequently, oxidation potential of Chl a was found to be the lowest among Chls and Phes. The results will help us to broaden our views on photosystems in A. marina.     

Coccolith evidence for Quaternary nutricline variations in the southern South China Sea

Nutricline variations during the last 1560 ka in the southern South China Sea are reconstructed using the relative abundance of the coccolithophore Florisphaera profunda in ODP Site 1143. Nutricline depth shows both long-term large magnitude variation and high frequency glacial–interglacial variation. On the long-term scale, the nutricline experienced four significant changes, which occurred at 900, 480, 250, and 50 ka respectively. According to these changes, five stages could be recognized during the last 1560 ka. From 1560 to 900 ka, the nutricline depth increased gradually. Around 900 ka, the nutricline abruptly shallowed and then remained stable until 480 ka. The nutricline was shallow during the time interval between 480 and 250 ka. At 250 ka, it deepened again and increased gradually until 50 ka. After 50 ka, the nutricline depth decreased gradually to modern values. On the glacial–interglacial scale, the variations in nutricline depth show different patterns before and after 900 ka. Before 900 ka, the nutricline was deep during glacial periods and shallow during interglacials. However, after 900 ka, the nutricline was deep during interglacials and shallow during glacials. Spectral analysis of the relative abundance of F. profunda shows a similar trend. In addition to the eccentricity (113, 76 ka), obliquity (55, 39 ka), and precession (24, 19 ka), we also find a 431 ka cycle. The former three periods reflect glacial–interglacial variations in nutricline, and the period of 431 ka reflects long-term variations in nutricline. We suggested that the variations in nutricline in the southern South China Sea were caused by global and regional climate changes. Glacial–interglacial variations in nutricline are mainly controlled by the East Asian monsoon, and the long-term variations might be related to the global climatic events, such as the mid-Pleistocene Revolution and the mid-Brunhes event.     

Cr isotopic insights into ca. 1.9 Ga oxidative weathering of the continents using the Beaverlodge Lake paleosol,Northwest Territories,Canada

The ca. 1.9 Ga Beaverlodge Lake paleosol was studied using redox‐sensitive Cr isotopes in order to determine the isotopic response to paleoweathering of a rhyodacite parent rock 500 million years after the Great Oxidation Event. Redox reactions occurring in modern weathering environments produce Cr(VI) that is enriched in heavy Cr isotopes compared to the igneous inventory. Cr(VI) species are soluble and easily leached from soils into streams and rivers, thus, leaving particle‐reactive and isotopically light Cr(III) species to build up in soils. The Beaverlodge Lake paleosol and two other published weathering profiles of similar age, the Flin Flon and Schreiber Beach paleosols, are not as isotopically light as modern soils, indicating that rivers were not as isotopically heavy at that time. Considering that the global average δ⁵³Cr value for the oxidative weathering flux of Cr to the oceans today is just 0.27 ± 0.30‰ (1σ) based on a steady‐state analysis of the modern ocean Cr cycle, the oxidative weathering flux of Cr to the oceans at ca. 1.9 Ga would have likely been shifted to lower δ⁵³Cr values, and possibly lower than the igneous inventory (–0.12 ± 0.10‰, 2σ). Mn oxides are the main oxidant of Cr(III) in modern soils, but there is no evidence that they formed in the studied paleosols. Cr(VI) may have formed by direct oxidation of Cr(III) using molecular oxygen or H₂O₂, but neither pathway is as efficient as Mn oxides for producing Cr(VI). The picture that emerges from this and other studies of Cr isotope variation in ca. 1.9 Ga paleosols is of atmospheric oxygen concentrations that are high enough to oxidize iron, but too low to oxidize Mn, resulting in low Cr(VI) inventories in Earth surface environments.     

Free-living amoebae (FLA) co-occurring with legionellae in industrial waters

Legionella pneumophila is known as the causative agent of Legionnaires’ disease and free-living amoebae (FLA) can serve as vehicles for legionellae. The aim of this study was to screen industrial waters for the occurrence of FLA and their co-occurrence with legionellae. A total of 201 water samples, including 129 cooling waters and 72 process waters, and 30 cooling lubricants were included in the study. Treated waters were screened periodically, pre and post treatment. Altogether, 72.6% of the water samples were positive for FLA, acanthamoebae being most prevalent (in 23.9% of the samples) followed by Vermamoeba vermiformis (19.4%). Only one cooling lubricant was positive (Acanthamoeba genotype T4). Legionella spp. were detected in 34.8% of the water samples and in 15% in high concentrations (>1000 CFU/100 ml). Altogether, 81.4% of the Legionella-positive samples were positive for FLA by standard methods. By applying a highly sensitive nested PCR to a representative set of random samples it was revealed that Legionella spp. always co-occurred with Acanthamoeba spp. Although the addition of disinfectants did influence amoebal density and diversity, treated waters showed no difference concerning FLA in the interphases of disinfection. It appears that FLA can re-colonize treated waters within a short period of time.     

Changes in calcareous nannofossil assemblages during the Mid-Pleistocene Revolution

The distribution of calcareous nannofossils are quantitatively analysed in high-resolution deep-sea core samples from North Atlantic DSDP Site 607 and Eastern Mediterranean ODP Site 967, between marine oxygen isotope stage (MIS) 35 and 15, in order to observe the response of calcareous nannofossils to the Mid-Pleistocene Revolution (MPR). Nannofossil abundance patterns show major variations through MIS 25–22 and distinct higher amplitude changes from MIS 21 upward, sometime clearly correlatable to glacial–interglacial cycles. High amplitude, short-term, fluctuations of small placoliths and F. profunda characterize the interval through MIS 24 to 22/21, suggesting strong instability in nutricline dynamics and surface water productivity. Principal Component Analysis and Shannon–Weaver indices (diversity and dominance) highlight significant shifts, mainly related to variations in the characteristics of surface waters. In both sites a minimum in diversity is recorded at MIS 22/21, corresponding to a maximum in the dominance of Reticulofenestra spp. at Site 607 and of Pseudoemiliania lacunosa at Site 967. Above MIS 21 the increase in abundance of various taxa (C. leptoporus, Umbilicosphaera spp., Syracosphaera spp., Rhabdosphaera spp., Oolithotus spp.) and a general increase in diversity are related to a distinct trend toward more stable and oligotrophic surface waters in contrast to the higher productivity and less stratified surface waters of the Early Pleistocene.     

Antagonist effects of strains of Bacillus spp. against Rhizoctonia solani for their protection against several plant diseases: Alternatives to chemical pesticides

Rhizoctonia solan Kühn (teleomorph: Thanatephorus cucumeris (Frank) Donk (R. solani) is a soil-borne phytopathogenic species complex as well as a necrotic fungus that causes significant crop yield losses worldwide. Agronomic practices (crop rotation), resistant cultivars, and chemical pesticides are widely used to control R. solani. However, these practices are insufficient to control the pest. Moreover, the application of chemical pesticides is harmful to both the environment and human health. Therefore, the use of biocontrol agents (BCAs) and that of plant-growth promoting bacteria (PGPB) are considered to be potentially sustainable, cost-effective, efficient, and eco-friendly ways to control R. solani. Several microorganisms have been used as biocontrol agents (BCAs) to manage R. solani. Among these, biocontrol agents (BCAs) Bacillus spp. are used to promote plant growth. Furthermore, due to its broad range of antibiotic-producing abilities, Bacillus spp. is widely used against R. solani. In this review, current and previous studies about the ability of Bacillus spp. to control diseases caused by R. solani are reported. It also focuses on the plant-growth promotion attributes of Bacillus spp. in response to the deleterious effects of R. solani.     

Diel and seasonal variation of a molluscan taxocoenosis associated with a Zostera marina bed in southern Spain (Alboran Sea)

The diel and seasonal variation of molluscs living in a Zostera marina bed (12–14 m depth) from southern Spain have been studied for one year using a small Agassiz trawl for collecting the samples (222 m²). The frequent and dominant species were very similar in both diurnal and nocturnal samples, including mainly gastropods such as Jujubinus striatus, Nassarius pygmaeus, Mitrella minor, Calliostoma planatum, Rissoa membranacea or Smaragdia viridis. Nevertheless, a significant increase of abundance of scavengers (e.g. Nassarius spp.) and carnivores (e.g. cephalopods) was registered in nocturnal samples. The abundance was maximal in spring and summer in diurnal and nocturnal samples and also in autumn for nocturnal ones, displaying significantly higher values in nocturnal samples. The species richness, diversity and evenness displayed a similar seasonal trend for diurnal and nocturnal samples, with maximum values during summer months. Monthly variation of the molluscan composition (species presence-absence data) was more acute than diel variation, according to the Cluster, MDS and ANOSIM results. Nevertheless, both monthly and diel changes in the structure (species abundance data) of the molluscan taxocoenosis were important throughout the year. Diel changes in the structure of the molluscan fauna are related to an increase of abundance of some species at nighttime due to vertical movements from the sediment to the shoots or along them (e.g. J. striatus, Nassarius spp.) or due to horizontal movements from adjacent habitats (e.g. cephalopods). Nevertheless, some species such as Rissoa spp. or Bittium spp. stay on the leaves of Z. marina during day as well as nighttime. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Late Cretaceous (Cenomanian–Maastrichtian) calcareous nannofossils from Goban Spur (DSDP Sites 549, 551): Implications for the palaeoceanography of the proto North Atlantic

The early late Cretaceous (Cenomanian–early Turonian) is thought to have been one of the warmest periods of the Phanerozoic. This period was characterised by tropical sea surface temperatures of up to 36 °C and a pole-to-equator-gradient of less than 10 °C. The subsequent Turonian–Maastrichtian was characterised by a continuous climatic cooling, peaking in the Maastrichtian. This climatic cooling and the resulting palaeoceanographic changes had an impact on planktic primary producer communities including calcareous nannofossils. In order to gain a better understanding of these Cenomanian–Maastrichtian palaeoceanographic changes, calcareous nannofossils have been studied from the proto North Atlantic (Goban Spur, DSDP Sites 549, 551). In order to see potential differences between open oceanic and shelf dwelling nannofossils, the data from Goban Spur have been compared to findings from the European shelf (northern Germany).A total of 77 samples from Goban Spur were studied for calcareous nannofossils revealing abundant (mean 6.2 billion specimens/g sediment) and highly diverse (mean 63 species/sample) nannofossil assemblages. The dominant taxa are Watznaueria spp. (mean 30.7%), Prediscosphaera spp. (mean 18.3%), Zeugrhabdotus spp. (mean 8.3%), Retecapsa spp. (mean 7.2%) and Biscutum spp. (mean 6.6%). The Cenomanian assemblages of both Goban Spur (open ocean) and Wunstorf (shelf) are characterised by elevated abundances of high fertility taxa like Biscutum spp., Zeugrhabdotus spp. and Tranolithus orionatus. Early Turonian to Maastrichtian calcareous nannofossil assemblages of Goban Spur are, however, quite different to those described from European sections. Oceanic taxa like Watznaueria spp., Retecapsa spp. and Cribrosphearella ehrenbergii dominate in Goban Spur whereas the fertility indicators Biscutum spp. and T. orionatus are more abundant in the European shelf assemblages. This shift from a homogeneous distribution of calcareous nannofossils in the Cenomanian towards a heterogeneous one in the Turonian–Maastrichtian implies a change of the ocean circulation. The “eddy ocean” system of the Cenomanian was replaced by an oceanic circulation similar to the modern one in the Turonian–Maastrichtian, caused by the cooling. The increased pole-to-equator-gradients resulted in an oceanic circulation similar to the modern one.