Changes in style and intensity of production in the Southeastern Atlantic over the last 70,000 yr

Accomplishing reliable paleo-reconstructions of productivity and upwelling conditions in eastern boundary current systems requires the use of cores collected in a basin-wide spatial pattern. Based on diatom assemblage analysis and the concentration and the bulk biogenic components of three gravity cores recovered from the Benguela Upwelling System (BUS) between 19° and 25°S, I describe rapid paleoceanographic changes that occurred during the last 70 ka B.P. in the southeastern Atlantic. The pattern of biogenic production and accumulation differs to varying degrees among the three core sites along the SW African coast. The highest sedimentation and accumulation rates at 25°S off Lüderitz conform with the present-day, well-known pattern of highest productivity and most intense coastal upwelling. Highest diatom values at 25°S during MIS3 points to more intense upwelling due to the combination of strong seaward-extending upwelling filaments, shoaling of the upwelled water, and the influence of silicate-rich waters of Antarctic origin. Productivity decreased along the central BUS throughout MIS2, when the siliceous–calcareous productivity regime shifted toward a system dominated by calcareous producers. Although intensity and strength of winds created adequate conditions for upwelling during MIS2, diatom production decreased. The complete replacement of the upwelling-associated diatom flora by a non-upwelling-related diatom community during MIS1 reflects weakened upwelling, weakened seaward extension of the upwelling filaments, and dominance of warmer surface waters. Combining changes in the composition of the diatom assemblage and variations of the bulk biogenic components allows for reliable reconstruction of paleoproductivity and upwelling changes for the SE Atlantic during the last 70 ka B.P.     

Environmental and climatic changes in the central Mediterranean Sea (Siculo–Tunisian Strait) during the last 30 ka based on dinoflagellate cyst and planktonic foraminifera assemblages

A high resolution micropalaeontological study of the core MD 04-2797 CQ recovered in the Sicilian–Tunisian Strait provides insights into the paleoclimatic history of the Mediterranean Sea at the transition between the western and eastern basin over the last 30 ka. Using the analysis of dinoflagellate cyst and planktonic foraminiferal assemblages, we reconstruct the paleoenvironmental changes that took place in this region. High abundances of cold temperate dinocyst species (Nematosphaeropsis labyrinthus, Spiniferites elongatus, Bitectatodinium tepikiense) and the polar planktonic foraminifera Neogloboquadrina pachyderma (left coiling) reveal three major cooling events synchronous with North Atlantic Henrich events 1 and 2 (H1 and H2) and the European and North Atlantic Younger Dryas event. During the Holocene, the presence of warm dinocyst species (Spiniferites mirabilis and Impagidinium aculeatum) and planktonic foraminifera (Globorotalia inflata and Globigerinoides ruber), reflects a significant increase of sea surface temperatures in the western Mediterranean basin, but a full warming was not recorded until 1500 years after the onset of the Holocene. Moreover, our results show that the Holocene was interrupted by at least four brief cooling events at ~ 9.2 ka, ~ 8 ka, ~ 7 ka and ~ 2.2 ka cal. BP, which may be correlated to climatic events recorded in Greenland ice cores and in the Atlantic Ocean.     

Wilkes Land Late Pleistocene diatom age model: From bio-events to quantitative biostratigraphy

A new method merges conventional and quantitative biostratigraphic approaches, supported by magnetic polarity data, to develop a chronological framework for sediment core MD03-2595 retrieved on the continental rise off Wilkes Land, East Antarctica before proceeding to paleoceanographic and paleoclimatic analysis. This combined method helped to identify climatic cycles, highlight stratigraphic discontinuities and reworking, and assess regional sedimentological and diatom biostratigraphic evolution. Core MD03-2595 spans the last 0.8 Ma, from the Mid Pleistocene Transition (MPT) to the Early Holocene. A hiatus including Marine Isotope Stages (MIS) 19, 18 and 17 was identified, and a decreasing trend in sediment accumulation rates from MIS 16 to the Holocene was observed. This quantitative diatom biostratigraphic dataset, placed in its own sedimentological and paleomagnetic context, provides new information regarding the paleobiogeographic distribution and ecological responses of biostratigraphically significant diatom species, such as Thalassiosira elliptipora and T. fasciculata, for the Matuyama–Brunhes (M–B) transition, and Actinocyclus ingens, Hemidiscus karstenii and Rouxia spp. for the middle and late Pleistocene diatom biozonation.     

A new stage 3 millennial climatic variability record from a SW France speleothem

We present a new high resolution speleothem stable isotope record from the Villars Cave (SW-France) that covers part of marine isotope stage (MIS) 3. The Vil14 stalagmite grew between ~ 52 and 29 ka. The δ¹³C profile is used as a palaeoclimate proxy and clearly shows the interstadial substages 13, 12 and 11. The new results complement and corroborate previously published stalagmite records Vil9 and Vil27 from the same site. The Vil14 stalagmite chronology is based on 12 Th-U dating by MC-ICP-MS and 3 by TIMS. A correction for detrital contamination was done using the ²³⁰Th/²³²Th activity ratio measured on clay collected in Villars Cave. The Vil14 results reveal that the onset of Dansgaard–Oeschger (DO) events 13 and 12 occurred at ~ 49.8 ka and ~ 47.8 ka, respectively. Within uncertainties, this is coherent with the latest NorthGRIP time scale (GICC05-60 ka) and with speleothem records from Central Alps. Our data show an abrupt δ¹³C increase at the end of DO events 14 to 12 which coincides with a petrographical discontinuity probably due to a rapid cooling. As observed for Vil9 and Vil27, Vil14 growth significantly slowed down after ~ 42 ka and finally stopped ~ 29 ka ago where the δ¹³C increase suggests a strong climate deterioration that coincides with both North Atlantic sea level and sea surface temperature drop.     

Distribution of large Emiliania huxleyi in the Central and Northeast Atlantic as a tracer of surface ocean dynamics during the last 25,000 years

The coccolithophore species Emiliania huxleyi is characterized by a wide range of sizes, which can be easily distinguished in the light microscope. In this study we have quantified the abundance of large (coccoliths > 4 µm in maximum length) E. huxleyi specimens during the last 25 kyr in sedimentary records from eleven cores and drill sites in the NE Atlantic and W Mediterranean Sea, to prove its usefulness in the reconstruction of water mass dynamics and biostratigraphic potential.During the Last Glacial Maximum this large form, a cold-water indicator, was common in the NE Atlantic and Mediterranean, and its regional variation in abundance indicates a displacement of the climatic zones southwards in agreement with the development of ice sheets and sea ice in the Northern Hemisphere during this period. On the other hand, the gradient between northern and southern surface water masses in the Subtropical Gyre appears to have been more pronounced than at present, while the Portugal and Canary Currents were more intense. In the western Mediterranean basin temperatures were cooler than in the adjacent Atlantic, provoking a quasi-endemism of these specimens until the end of Heinrich Event 1. This may have been due to a restriction in the communication between the Atlantic and Mediterranean through the Strait of Gibraltar, the arrival of cold surface water and the amplification of cooling after the development of ice sheets in the Northern Hemisphere.During the deglaciation, large E. huxleyi specimens decreased in abundance at medium and low latitudes, but were still numerous close to the Subarctic region during the Holocene. In transitional waters this decrease to present day abundances occurred after Termination Ib.The abrupt change in abundance of this large E. huxleyi form is proposed as a new biostratigraphic event to characterize the Holocene in mid- to low-latitude water masses in the North Atlantic, although this horizon seems to be diachronous by 5 kyr from tropical to subarctic regions, in agreement with the gradual onset of warm conditions.     

Paleoceanographic evolution of North Pacific surface water off Japan during the past 150,000 years

Hydrographic variability in the Mixed Water Region of the Northwest Pacific Ocean at latitudes 35°–40°N, between the Kuroshio Extension and Oyashio Front, causes complex upwelling, leading to large primary productivity and thus great fishery resources. We reconstructed the periodicity of the variability in North Pacific Intermediate Water upwelling and surface ocean hydrography based on the high-resolution analysis of diatom assemblages in seven cores, representing the last 150,000 years. We derived annual sea surface temperatures (SSTs) through a diatom-based proxy (Td′). The Td′-derived annual SSTs (°C) are controlled by orbital forcing, and show a reversed saw-tooth in southern cores, in contrast to a normal saw-tooth pattern in the northern cores. Oceanic diatom abundances along the northern margin of the Mixed Water Region are twice times as high as beneath the axis of the Kuroshio Extension, and fluctuated in a revised saw-tooth pattern with higher overall abundances interglacials. After the last deglaciation, annual SSTs declined markedly during Heinrich and Bond events in the northern North Atlantic, when ice-rafted detritus transported by icebergs was abundant. Wavelet analyses of the record of oceanic diatom abundances show significant variability at 2.0-kyr, 2 to 5.6-kyr and 3.2 to 9.6-kyr periods. Wavelet analyses of the annual SST records show significant periodicity at 1.4 to 2.6-kyr, 3.3 to 4.0-kyr, 7.2 to 12.8-kyr cycles.     

The geographical distribution and (palaeo)ecology of Selenopemphix undulata sp. nov., a new late Quaternary dinoflagellate cyst from the Pacific Ocean

Detailed palynological studies in the northeast (NE) Pacific, Strait of Georgia (BC, Canada), southeast (SE) Pacific and northwest Pacific (Dongdo Bay, South Korea) resulted in the recognition of the new dinoflagellate cyst species Selenopemphix undulata sp. nov. This species is restricted to cool temperate to sub-polar climate zones, where it is found in highest relative abundances in highly productive non- to reduced upwelling regions with an annual mean sea-surface temperature (aSST) below 16 °C and an annual mean sea-surface salinity (aSSS) between 20 and 35 psu. Those observations are in agreement with the late Quaternary fossil records from Santa Barbara Basin (ODP 893; 34°N) and offshore Chile (ODP 1233; 41°S), where this species thrived during the last glacial. This period was characterised by high nutrient availability and the absence of species favouring upwelling conditions. The indirect dependence of S. undulata sp. nov. abundances on nutrient availability during reduced or non-upwelling periods is expressed by the synchronous fluctuations with diatom abundances, since the distribution and growth rates of the latter are directly related with the availability of macronutrients in the surface waters.     

Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes

The late Quaternary record of Pulleniatina obliquiloculata was investigated from two well dated sediment cores from the Andaman Sea (NE Indian Ocean) to examine its paleoceanographic significance and the presence of the Pulleniatina Minimum Events (PME) in the western North Pacific. As in the Pacific, our study shows that PMEs exist in the Indian Ocean albeit with a lower intensity. The Holocene PME occurs between 4.5 and 3.0 cal ka BP with a considerable reduction in P. obliquiloculata abundance, and which matches well with the Pacific records influenced by the Kuroshio Current. Additionally, two significant minimum events of P. obliquiloculata are also seen during the Younger Dryas (YD) and late Last Glacial Maximum (LGM, 20–18 cal ka BP). Overall, the PMEs of the Andaman Sea are not current driven events like in the western Pacific margin either by the weakening of the Kuroshio Current or reduced winter SSTs. The PMEs of the Andaman Sea are characterised by lower abundances of thermocline species indicating the increased depth of the thermocline (DOT) and reduced winter SSTs mainly during the minimum events of the YD and late LGM. The high SSTs during the Holocene PME make this event a mystery. However, the presence of PMEs in the Andaman Sea suggests that these events are not confined to areas influenced by the Kuroshio Current but may be responding to a broad scale oceanographic–climatic process or mechanism which needs to be explored with a detailed study.     

Late Quaternary (Weichselian) alluvial history and neotectonic control on fluvial landscape development in the southern Körös plain,Hungary

Four drill cores and a clay pit section have been examined in the southern part of the Körös plain to understand the history and controls on alluvial sedimentation for the last ~ 40 ka. Four facies groups were identified, such as channel, channel margin, floodplain and floodbasin with seven distinctive facies. Magnetic susceptibility and mineralogy have further characterized the sedimentary facies indicating shifts in humidity conditions, variations in sediment flux and pedogenesis. Detailed pollen analysis of a 7.5 m thick clayey succession indicated climatic variability within the MIS 3 period. The spatial distribution of the different facies allowed outlining alluvial architecture of the study area. Three depositional units composed of various facies were identified based on OSL and radiocarbon data. These packages correspond to three major phases of channel activity: (F-I) pre-LGM period (> 30 ka to 24 ka), (F-II) post-LGM interstadial (18–16 ka), and (F-III) Late Glacial < 15 ka to ~ 10 ka). The pre-LGM and post-LGM “interstadial” phases are characterized by meandering river patterns, while the Late Glacial fluvial activity is characterized by a braided system in the area. Higher sediment supply feeding this braided river was probably caused by neotectonic uplift of the southern margin of the basin, documented by a significant stratigraphic gap between 25 and 14 ka.     

Inorganic and organic nitrogen uptake by the toxigenic diatom Pseudo-nitzschia australis (Bacillariophyceae)

The nitrogen uptake capabilities of the toxigenic diatom Pseudo-nitzschia australis (Frenguelli), freshly isolated from Monterey Bay California, were examined in unialgal laboratory cultures at saturating photosynthetic photon flux densities (100 μmol photons m⁻² s⁻¹) and 15 °C. The kinetics of nitrogen (nitrate, ammonium, urea and glutamine) uptake as a function of substrate concentration were estimated from short (20.5 min) incubations using the ¹⁵N-tracer technique. Based on the estimated maximum specific uptake rates and measures of N affinity (the initial slope of the uptake versus nutrient concentration curve), nitrate is the preferred nitrogen substrate, followed by glutamine and ammonium, which are equivalent. Rates of urea uptake by P. australis did not saturate at concentrations as high as 36 μg-at N L⁻¹, and urea uptake as a function of concentration could not be described by Michaelis–Menten kinetics over the concentration gradient tested. Although there is a clear preference for nitrate at equivalent concentrations (compared to ammonium, urea, and glutamine), these laboratory results demonstrate the capability of this pennate diatom to utilize both inorganic and organic forms of nitrogen, supporting field observations that P. australis blooms during both upwelling and non-upwelling conditions off the west coast of North America. Substantial differences in the nitrogenous nutrition of P. australis can be expected in these environments, and anthropogenic inputs of N substrates such as ammonium and urea can support its growth, and may contribute significantly to both harmful diatom blooms and the maintenance of seed populations at non-bloom abundances, particularly during periods of reduced or absent upwelling.     

Nouvelles données sur la chronologie des sites paléolithiques en contexte lœssique du Nord-Est et du Sud-Est de la Roumanie (Périphérie orientale des Carpates)

In the present study, the chronology of several intraloessic Upper and Middle Palaeolithic sites, located in Moldova, Dobrogea and the eastern Danube Plain, is re-examined and better defined on the basis of new chronological data (IRSL ages on loess, ESR/U-Th ages on teeth) and also biostratigraphic and pedostratigraphic evidence. Middle Palaeolithic occupations have been identified in the MIS 6 loess L2 (interstadial episode), the MIS 7 pedocomplex S2 and the red soils S3 presumably assigned to MIS 9. These results are questioning the chronological extension of the Middle Palaeolithic in Romania which until early 2000 (Păunescu, 1999 a, b; Cârciumaru, 1999) was restricted to the Upper Pleistocene (short chronology: 130–35 ka; MIS 5-MIS 3). Hence, we demonstrate herein that Humans were already present during the Middle Pleistocene at the eastern periphery of the Carpathian Mountains, along the Danube valley and its tributary, the Prut River.     

Avian fossil assemblages at the onset of the LGM in the eastern Alps: A palaecological contribution from the Rio Secco Cave (Italy)

The avian fossil assemblages from the late Pleistocene deposits of the Rio Secco Cave (north-eastern Italy) is presented herein. We studied the layers that date back to the end of MIS3 and the beginning of MIS2, which also contain evidence of Gravettian frequentation dated to 33.5–30 ka cal BP. The systematic analysis revealed the presence of 18 species and other supraspecific taxa that supported palaeoenvironmental reconstructions. Taxa indicate that, at the onset of LGM, site surroundings were characterised by conifer or mixed forests, open grasslands, slow-flowing water bodies and mountain meadows with rocky outcrops, as indicated by Lagopus muta. Today, this environment is found above the tree line (beyond 1500–2000 m) and cannot be detected near the site, located at 580 m asl. Noteworthy, is also the finding of the second Italian late Pleistocene fossil record of Picus canus.     

Impact of the Middle Miocene climate transition on elongate,cylindrical foraminifera in the subtropical Pacific

Fifty-eight species of elongate, cylindrical benthic foraminifera (here referred to as the Extinction Group) belonging to genera that became extinct during the mid-Pleistocene Climate Transition (MPT), were documented (~ 50 kyr resolution) through the early middle Miocene (15–13 Ma) in two sites on opposite sides of the subtropical Pacific Ocean (ODP Sites 1146, South China Sea; ODP Site 1237, southeast Pacific). The study was undertaken to investigate the response of the Extinction Group (Ext. Gp) to the major cooling during the middle Miocene Climate Transition (MCT) to look for clues that might explain the causes of the extinction during the glacials of the mid-Pleistocene Climate Transition. Ext. Gp faunal differences between the two sites (attributed to regional and bathymetric differences in food supply to the seafloor) are greater than those that occurred through the 2 myr time span at either site. The middle Miocene Climate Transition was not an interval of enhanced species turnover or a decline in Ext. Gp abundance, in contrast to the major extinctions that occurred during the mid-Pleistocene Climate Transition. Distinct changes in the composition of the Ext. Gp faunas did occur through this time (more pronounced in Site 1237). At both sites the pre-middle Miocene Climate Transition faunas were transformed into their post-middle Miocene Climate Transition composition during the period of major cooling (14.0–13.7 Ma). During this transition interval the faunal composition swung back and forth between the two end member faunas. These faunal changes are attributed to changes in productivity (decrease in South China Sea, increase in southeast Pacific), brought about by major changes in global climate and continental aridity.     

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.     

Sea-surface temperature for left-coiling Neogloboquadrina populations inhabiting the westernmost Mediterranean in the middle Pleistocene and the Pleistocene-Pliocene transition

Using the modern analog methodology applied to planktonic foraminifers, we analyze the relation between the frequency of the coiling type in Neogloboquadrina populations and the sea-surface temperatures (SST) during the middle Pleistocene and the Pleistocene-Pliocene transition in the Alboran Sea (westernmost Mediterranean), close to the Atlantic connection. The results reveal that the present-day positive correlation between the two variables (r = 0.649) is maintained even with a higher coefficient (r = 0.783) in the middle Pleistocene but falls slightly (r = 0.517) in the Pleistocene-Pliocene transition due mainly to a dispersal of the temperatures for the samples bearing predominantly left-coiling Neogloboquadrina. The temperature used as a reference for the coiling change resulted 5-6 °C above its North Atlantic present-day reciprocal, but these thermal differences could be caused by: i) a slight overestimate (1–2 °C) due to the lumping of all neogloboquadrinids into a single variable when SST are estimated; ii) only the warmer range of temperatures for the left-coiling populations would be represented in the samples; and iii) a remarkable warming inside the westernmost Mediterranean during the summer stage mixing cold and warm assemblages in bottom sediments. In addition, these results in combination with those derived from the isotopic analyses (δ¹⁸O) in G. bulloides tests, suggest that during the Pliocene-Pleistocene transition two different populations of left-coiling Neogloboquadrina could have existed with different environmental requirements: one, derived from late Miocene-Pliocene (i.e., left-coiling N. acostaensis group), and another being the ancestor of the modern N. pachyderma (left-coiling). Similarity analyses were achieved in order to locate the position of the core-tops with the assemblages most analogous to those of the fossil samples containing left-coiling Neogloboquadrina. The results reinforce the idea that the presence of these forms in the Mediterranean during the intervals studied would be related mainly to the input of cold waters from the North Atlantic during glacial stages, although it could be secondarily favored by the establishment of upwelling conditions, as in the present-day North Alboran waters.     

Nitrate and phosphate uptake kinetics of the harmful diatom Eucampia zodiacus Ehrenberg,a causative organism in the bleaching of aquacultured Porphyra thalli

The diatom Eucampia zodiacus Ehrenberg is a harmful diatom which indirectly causes bleaching of aquacultured Nori (Porphyra thalli) through competitive utilization of nutrients during bloom events. In the present study, we experimentally investigated the nitrate (N) and phosphate (P) uptake kinetics of E. zodiacus, Harima-Nada strain. Maximum uptake rates (ρ_max), which were obtained by short-term experiments, were 0.777 and 0.916 pmol cell^?1 h^?1 for nitrate and 0.244 and 0.550 pmol cell^?1 h^?1 for phosphate at 9 and 20 °C, respectively. The half-saturation constants for uptake (K_s) were 2.59 and 2.92 μM N and 1.83 and 4.85 μM P at 9 and 20 °C, respectively. Although the maximum specific uptake rate (V_max; V_max = ρ_max/Q₀, Q₀; minimum cell quota) and V_max/K_s for nitrate at 9 °C are about 1/2 of those obtained at the optimum temperature (20 °C), they are still higher than those obtained for many other phytoplankton at their optimum temperature conditions for uptake. These results suggest that E. zodiacus utilizes nitrogen efficiently at low water temperature, and it is one of the important factors causing the serious damage to Porphyra thalli by bleaching due of this species. For phosphate, the K_s values of E. zodiacus were higher than those reported for other species; the V_max and V_max/K_s values were much lower than those of other diatoms such as Skeletonema costatum (Greville) Cleve. These results suggest that E. zodiacus is disadvantaged compared to other diatom species during competitive utilization of phosphate.     

Nitrate and phosphate uptake kinetics of the harmful diatom Coscinodiscus wailesii,a causative organism in the bleaching of aquacultured Porphyra thalli

The large diatom Coscinodiscus wailesii is one of the problematic species which indirectly cause bleaching damage to “Nori” (Porphyra thalli) cultivation through competitive utilization of nutrients during its bloom. In the present study, we experimentally investigated the nitrate (N) and phosphate (P) uptake kinetics of C. wailesii, Harima-Nada strain. Maximum uptake rates (ρ_max), obtained by short-term experiments, were 58.3 and 95.5 pmol cell⁻¹ h⁻¹ for nitrate and 41.9 and 59.1 pmol cell⁻¹ h⁻¹ for phosphate at 9 and 20 °C, respectively. The half saturation constants for uptake (K_s) were 2.91 and 5.08 μM N and 5.62 and 6.67 μM P at 9 and 20 °C, respectively. The ρ_max values of C. wailesii, much higher than those of other marine phytoplankton species, suggest that C. wailesii is able to take up large amounts of nutrients from the water column. On the other hand, V_max/K_s (V_max; V_max = ρ_max/Q₀, Q₀; minimum cell quota) values of C. wailesii, which is a better measure to evaluate the competitive ability for nutrient uptake, were low in dominant diatom species. This parameter indicates that C. wailesii is disadvantaged compared to other diatom species in competing for nutrients, and the decreasing nutrient concentrations from winter to spring is an important factor limiting C. wailesii blooming in early spring.     

Diatoms as indicators of isolated herbaceous wetland condition in Florida,USA

Benthic, epiphytic, and phytoplanktonic diatoms, as well as soil and water physical–chemical parameters, were sampled from 70 small (average 0.86 ha) isolated depressional herbaceous wetlands located along a gradient of human disturbance in peninsular Florida to (1) compare diatom assemblage structure between algal types; (2) develop biological indicators of wetland condition; (3) examine synecological relationships between diatom structure and environmental variables, with the ultimate goal of developing an index of biological integrity using a single assemblage. Collected diatom samples were enumerated to 250 valves and identified to species or subspecies. An assessment of wetland condition was made using a landscape-scale human disturbance score (Landscape Development Intensity index, LDI), calculated for each site using land use maps and GIS.Assemblages from both impaired and reference sites were compared using blocked multi-response permutation procedures, the percent similarity index, and visually examined using non-metric multidimensional scaling (NMDS). No ecologically significant compositional differences were found within sites. Mantel's test (Mantel's r = 0.29, p < 0.0001) and NMDS (stress: 14.52, variance: 78.5%) identified epiphytic diatoms as the most responsive to human disturbance. Strong significant correlations (|r_s| > 0.50, p < 0.05) were found between epiphytic NMDS site scores and soil pH, specific conductivity, water total phosphorous, and LDI, while soil pH, water color, soil TP, and turbidity were also significantly correlated (p < 0.05).Metrics to assess wetland condition were developed using epiphytic abundance data. Epiphytic taxa sensitive or tolerant to human landscape modification were identified using Indicator Species Analysis, and autecological indices relating diatom sensitivity to nutrients, pH, dissolved oxygen levels, saprobity, salinity, and trophic status were calculated. Fourteen final metrics were identified, scored on an ordinal scale, and combined into the Diatom Index of Wetland Condition (DIWC). The DIWC was highly correlated with the disturbance score (Spearman's r_s = −0.71, p < 0.0001), although the results need to be validated.     

Temperature and sex dependent effects on cardiac mitochondrial metabolism in Atlantic cod (Gadus morhua L.)

To test the hypothesis that impaired mitochondrial respiration limits cardiac performance at warm temperatures, and examine if any effect(s) are sex-related, the consequences of high temperature on cardiac mitochondrial oxidative function were examined in 10 °C acclimated, sexually immature, male and female Atlantic cod. Active (State 3) and uncoupled (States 2 and 4) respiration were measured in isolated ventricular mitochondria at 10, 16, 20, and 24 °C using saturating concentrations of malate and pyruvate, but at a submaximal (physiological) level of ADP (200 µM). In addition, citrate synthase (CS) activity was measured at these temperatures, and mitochondrial respiration and the efficiency of oxidative phosphorylation (P:O ratio) were determined at [ADP] ranging from 25–200 µM at 10 and 20 °C. Cardiac morphometrics and mitochondrial respiration at 10 °C, and the thermal sensitivity of CS activity (Q₁₀=1.51), were all similar between the sexes. State 3 respiration at 200 µM ADP increased gradually in mitochondria from females between 10 and 24 °C (Q₁₀=1.48), but plateaued in males above 16 °C, and this resulted in lower values in males vs. females at 20 and 24 °C. At 10 °C, State 4 was ~10% of State 3 values in both sexes [i.e. a respiratory control ratio (RCR) of ~10] and P:O ratios were approximately 1.5. Between 20 and 24 °C, State 4 increased more than State 3 (by ~70 vs. 14%, respectively), and this decreased RCR to ~7.5. The P:O ratio was not affected by temperature at 200 μM ADP. However, (1) the sensitivity of State 3 respiration to increasing [ADP] (from 25 to 200 μM) was reduced at 20 vs. 10 °C in both sexes (K_m values 105±7 vs. 68±10 μM, respectively); and (2) mitochondria from females had lower P:O values at 25 vs. 100 μM ADP at 20 °C, whereas males showed a similar effect at 10 °C but a much more pronounced effect at 20 °C (P:O 1.05 at 25 μM ADP vs. 1.78 at 100 μM ADP). In summary, our results demonstrate several sex-related differences in ventricular mitochondrial function in Atlantic cod, and suggest that myocardial oxidative function and possibly phosphorylation efficiency may be limited at temperatures of 20 °C or above, particularly in males. These observations could partially explain why cardiac function in Atlantic cod plateaus just below this species׳ critical thermal maximum (~22 °C) and may contribute to yet unidentified sex differences in thermal tolerance and swimming performance.     

Holocene and Late Pleistocene climate in the sub-Mediterranean continental environment: A speleothem record from Poleva Cave (Southern Carpathians,Romania)

The PP10 stalagmite from Poleva Cave provides a Late Pleistocene and Holocene isotopic record characteristic for the SW of Romania, a sub-Mediterranean climatic region. The speleothem was dated by eight TIMS and one alpha U-series dates which showed that it was precipitated between ∼ 75 ka and ∼ 2 ka with at least two hiatuses. The basal sector of the stalagmite showed a slow-growing regime of ∼ 0.26 cm/ka, while the upper one grew relatively fast with about 5 cm/ka. The temporal resolution for the isotopic sampling is thus ∼ 2 ka/sample for the lower sector, and ∼ 150 years/sample for the upper one. The relationship between δ¹⁸O and temperature was found positive. The isotopic record of the lower sector shows two marked cold intervals during ∼ 67 and 58 ka and ∼ 40–35 ka, respectively, which correlate well with the Villars and Soreq records. The upper sector record is so far the most detailed Holocene isotopic record in Romania and the only one available for the regions located at the exterior of the Carpathians Range. The signal shows a gradual warming after the GS1 event punctuated by several cold events at ∼ 8, 7.2 and 4.2 ka and also by warm oscillations centered at about 5.2 and 3.3 ka. The results seem to indicate that if the North-Atlantic first-order signals may extend well to the south-eastern Europe, their amplitude and general trend may be diminished by the interferences with the Mediterranean circulation.