Maastrichtian calcareous nannofossil biostratigraphy and paleoecology in the Equatorial Atlantic (Demerara Rise, ODP Leg 207 Hole 1258A)

Species richness, absolute and relative abundances of Maastrichtian calcareous nannofossils were analyzed in Hole 1258A. Absolute abundances of taxa were used for the biozonation of this hole and the record of successive bio-events. Distribution patterns of cool water taxa such as Ahmuellerella octoradiata, Gartnerago segmentatum and Kamptnerius magnificus underscore two major cooling events. These events occurred during Chron C31r and during undifferentiated Chrons C31n to C30n. The latter event appears to be accompanied by lowered productivity, as expressed by the lower abundances of fertility index taxa Biscutum constans and Zeugrhabdotus spp. An end-Maastrichtian warming event is recorded in Chron C29r by the sudden drop in abundance of cool water taxa and acme of tropical taxon Micula murus. The disappearance of B. constans just before this event and the significant increase of Micula decussata, respectively, suggest lowered productivity and high-stress environmental conditions prior to the K/P boundary (Cretaceous-Paleogene). These results correlate very well with the climatic scenario proposed by Li and Keller (1998a) in South Atlantic Hole 525A as suggested by stable isotopes and distribution patterns of planktic foraminifera.     

Planktonic foraminiferal response to the latest Maastrichtian abrupt warm event: a case study from South Atlantic DSDP Site 525A

An abrupt global warming of 3–4°C occurred near the end of the Maastrichtian at 65.45–65.10 Ma. The environmental effects of this warm event are here documented based on stable isotopes and quantitative analysis of planktonic foraminifera at the South Atlantic DSDP Site 525A. Stable isotopes of individual species mark a rapid increase in temperature and a reduction in the vertical water mass stratification that is accompanied by a decrease in niche habitats, reduced species diversity and/or abundance, smaller species morphologies or dwarfing, and reduced photosymbiotic activity. During the warm event, the relative abundance of a large number of species decreased, including tropical–subtropical affiliated species, whereas typical mid-latitude species retained high abundances. This indicates that climate warming did not create favorable conditions for all tropical–subtropical species at mid-latitudes and did not cause a massive retreat in the local mid-latitude population. A noticeable exception is the ecological generalist Heterohelix dentata Stenestad that dominated during the cool intervals, but significantly decreased during the warm event. However, dwarfing is the most striking response to the abrupt warming and occurred in various species of different morphologies and lineages (e.g. biserial, trochospiral, keeled globotruncanids). Dwarfing is a typical reaction to environmental stress conditions and was likely the result of increased reproduction rates. Similarly, photosymbiotic activity appears to have been reduced significantly during the maximum warming, as indicated by decreased δ¹³C values. The foraminiferal response to climate change is thus multifaceted resulting in decreased species diversity, decreased species populations, increased competition due to reduced niche habitats, dwarfing and reduced photosymbiotic activity.     

The response of calcareous nannofossil assemblages to the Paleocene Eocene Thermal Maximum at the Walvis Ridge in the South Atlantic

Compositions and abundances of calcareous nannofossil taxa have been determined in a ca 170 kyrs long time interval across the Paleocene/Eocene boundary at 1-cm to 10-cm resolution from two ODP Sites (1262, 1263) drilled along the flank of the Walvis Ridge in the South Atlantic. The results are compared to published data from ODP Site 690 in the Weddell Sea. The assemblages underwent rapid evolution over a 74 kyrs period, indicating stressed, unstable and/or extreme photic zone environments during the PETM hyperthermal. This rapid evolution, which created 5 distinct stratigraphic horizons, is consistent with the restricted brief occurrences of malformed and/or weakly calcified morphotypes. The production of these aberrant morphotypes is possibly caused by major global scale changes in carbon cycling in the ocean–atmosphere system, affecting also photic zone environments. No marked paleoecologically induced changes are observed in abundances of the genera Discoaster, Fasciculithus and Sphenolithus at the Walvis Ridge sites. Surprisingly, there is no significant correlation in abundance between these three genera, presumed to have had a similar paleoecological preference for warm and oligotrophic conditions.     

Calcareous nannofossil biostratigraphic framework for middle Eocene sediments from ODP Hole 1260A, Demerara Rise

Ocean Drilling Program (ODP) Site 1260 recovered a near-continuous and expanded (187-m thick) middle Eocene carbonate sequence at mid-bathyal depths on Demerara Rise off Suriname, South America. A calcareous nannofossil biostratigraphic framework has been established for the sequence to aid multi-proxy cyclostratigraphic analyses. The diversity of calcareous nannofossils is reasonably high and preservation moderate throughout most of the section, and the proximity to the continent is indicated by the occurrence of braarudosphaerids in the lower three quarters of the section. The species richness of sphenoliths is particularly high, and our data confirm the occurrence of new sphenoliths during the middle Eocene as shown recently by Bown and Dunkley Jones (2006). In particular we corroborate the occurrences of Sphenolithus strigosus and S. runus that these authors found in their Zone NP16 Tanzania sediments, however we extend the ranges of these taxa down into Zone NP15 (CP13). Moreover we document the occurrence of Bramletteius serraculoides in Zone NP15 (CP13b) and the occurrence of Sphenolithus predistentus in NP16 (CP14a), extending their known ranges down column.     

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.     

Reproducibility and reliability of the Pliensbachian calcareous nannofossil biohorizons from the Basque-Cantabrian Basin (Northern Spain)

Based on calcareous nannofossil assemblages identified in four expanded and well-dated sections from the Basque-Cantabrian Basin, the main objective of this paper is to improve the knowledge of the Pliensbachian calcareous nannofossil events, and to calibrate these events to the ammonite zones established for this area. The semiquantitative analysis of more than 140 smear slides from the Tudanca and Santotis sections, and the re-analysis of more than 200 smear slides from the Camino and San Andrés sections, have been carried out in order to describe the succession of calcareous nannofossil assemblages. Related to their composition changes, we have recognized and calibrated to the ammonite zones two main events: the first occurrences (FOs) of Similiscutum cruciulus and Lotharingius hauffii, and six secondary events: the FOs of Biscutum novum, Biscutum grande, Biscutum finchii, Lotharingius barozii and the FCOs (first common occurrences) of Calcivascularis jansae and L. hauffii. In the Camino and San Andrés sections, we also identify the FOs of Biscutum dubium, Bussonius prinsii and Lotharingius sigillatus. The obtained data allow us to assess the degree of reproducibility of the Pliensbachian calcareous nannofossil events in the studied area. The biohorizon succession recognized in the Basque-Cantabrian Basin are compared to those proposed for NW Europe, Lusitanian Basin, Italy and Southern France.     

Calcareous nannofossil biostratigraphy of the Paleocene sediments of the Odessa Gas Field (NW Black Sea)

Calcareous nannofossils from Paleocene sediments of two boreholes (Odeska-6 and 20) from the north-western shelf of the Black Sea are examined. Five nannofossil Zones are identified according to the standard zonations of Martini (1971) and Quillévéré et al. (2002): the Chiasmolithus danicus Zone (NP3), the upper part of Ellipsolithus Macellus Zone (NP4b), the Fasciculithus tympaniformis Zone (NP5), the Heliolithus kleinpelli Zone (NP6) and the Heliolithus riedelii Zone (NP8). This biostratigraphical work allows us to correlate the Bilokamian and Kachian regional stages of the Stratigraphic Scheme of Southern Ukraine (Zernetskiy et al., 1993) to the standard nannofossil zonations and, therefore, to the International Chronostratigraphic scheme. The presence of an unconformity between the Bilokamian and Kachian regional stages in the borehole section of Odeska-6 is suggested by Linear Sedimentary Rates estimated for the two boreholes. This unconformity corresponds to the upper part of the Chiasmolithus danicus nannofossil Zone (NP3) and the lower part of Ellipsolithus Macellus (NP4a), and is estimated to last nearly 1.94 Ma.     

Evidence of increasing surface water oligotrophy during the Campanian–Maastrichtian boundary interval: Calcareous nannofossils from DSDP Hole 390A (Blake Nose)

The latest Cretaceous (Campanian–Maastrichtian) is characterized by several global cooling and intermittent warming events. These climatic changes influenced the palaeoceanography substantially, including changes of the deep water sources and surface water currents. One of the most prominent episodes of climatic cooling occurred during the Campanian–Maastrichtian transition. This study focuses on the palaeoclimate and palaeoceanography of the Campanian–Maastrichtian transition by analysing the calcareous nannofossils of DSDP Hole 390A (139.92–126.15 mbsf; Blake Nose). For the examination of calcareous nannofossils sixty samples were processed using the settling technique. Biostratigraphical index taxa (Broinsonia parca constricta, Uniplanarius trifidus, and Tranolithus orionatus) suggest a late Campanian age for the major part of the studied section. The calcareous nannofossils are well preserved, highly abundant (6.80 billion specimens/gram sediment) and diverse (80 species/sample). The assemblages are dominated by Prediscosphaera spp. (20.5%), Watznaueria spp. (20.3%) and Retecapsa spp. (9.8%). Cool water taxa (Ahmuellerella octoradiata, Gartnerago segmentatum, and Kamptnerius magnificus), however, appear less frequently and do not exceed more than 1%. Due to their rarity these cool water taxa do not support the existence of an intense cooling phase during the Campanian–Maastrichtian transition at DSDP Hole 390A. Around 133 mbsf several nannofossil taxa, however, show a distinctive turnover. Mesotrophic species like Discorhabdus ignotus, Zeugrhabdotus bicrescenticus and Zygodiscus exmouthiensis are abundant below 133 mbsf, whereas oligotrophic taxa like Watznaueria spp., Eiffellithus spp. and Staurolithites flavus become common above this level. These changes imply a decrease in the input of nutrients, perhaps caused by a reorganization of ocean currents (Palaeo Gulf Stream) and reduced upwelling.     

Response of calcareous nannofossil assemblages to paleoenvironmental changes through the mid-Pleistocene revolution at Site 1090 (Southern Ocean)

Quantitative study on calcareous nannofossil assemblages has been performed in high time resolution (2–3 kyr) at the Ocean Drilling Program Site 1090. The location of this site in the Southern Ocean is crucial for the comprehension of thermohaline circulation and frontal boundary dynamics, and for testing the employ of nannoflora as paleoceanographical tool. The chronologically well constrained investigated record spans between Marine Isotope Stage (MIS) 35 and 15, through an interval of global paleoclimate and paleoceanographical modification also known as mid-Pleistocene revolution (MPR). Measures of ecological (Shannon–Weaver diversity and paleoproductivity) and dissolution indices together with spectral and wavelet analyses carried out on the acquired time series provide valuable information for interpretation of data in terms of paleoecology and paleoceanography. Assemblages are mainly represented by dominant small Gephyrocapsa, common Calcidiscus leptoporus s.l., Coccolithus pelagicus s.l., Gephyrocapsa (4-5.5 μm), the extinct Pseudoemiliania lacunosa and Reticulofenestra spp. (R. asanoi and Reticulofenestra sp.). Morphotypes discriminated within Calcidiscus leptoporus s.l. and Coccolithus pelagicus s.l., reveal that they may have had different ecological preferences during Pleistocene with respect to the present. The composition and fluctuation in nannofossil assemblage and their comparison with the available Sea Surface Temperature (SST) and C-org curves suggest a primary ecological response to paleoenvironmental changes; relationships to different surface water features and boundary dynamics, as well as to different efficiencies and motions of the intermediate and deep water masses have been inferred. A more northward position of Subantarctic Front (SAF) during most of the Early Pleistocene record has been highlighted based on assemblage composition characterised by common Calcidiscus leptoporus s.l., Coccolithus pelagicus s.l., medium Gephyrocapsa (4–5.5 μm), and by the rarity or absence of Umbilicosphaera spp., Rhabdosphaera spp., Pontosphaera spp., Oolithotus fragilis. Exceptions are the more intense interglacials MIS 31, 17, and probably MIS 15, when a southward displacement of frontal system occurred, coincident with peaks in abundance of Helicosphaera spp. and Syracosphaera spp. Higher nutrient content and more dynamic conditions occurred between MIS 32 and MIS 25, in relation to shallower location of nutrient-rich Antarctic Intermediate Water (AAIW) core and to reduction of glacial–interglacial variability. A nannofossil barren interval is coincident with the known stagnation of South Atlantic deep water circulation during MIS 24, when North Atlantic Deep Water (NADW) was reduced or suppressed and an enhanced northward deep penetration of the more corrosive Circumpolar Deep Water (CPDW) took place. An event of strong instability in nutricline dynamics characterised the transition MIS 23–22 as suggested by sharp fluctuations in paleoproductivity proxies, linked to major changes in oceanographic circulation and to the first distinct increase of larger ice volumes at this time. From MIS 21 upward the nannofossil variations seem to be primarily controlled by glacial–interglacial cyclicity and temperature fluctuations. The cyclic fluctuation recognised in nannofossil abundance seems to be linked to orbitally-forced climatic variation, primarily to the obliquity periodicity recorded in the patterns of C. leptoporus intermediate (5–8 μm) and C. pelagicus pelagicus (6–10 μm); however no obvious and linear relations may be always observed between nannoflora fluctuation and Milankovitch parameters, suggesting more complex and unclear relationships between nannofossils and environmental change.     

Middle to late Miocene fluctuations in the incipient Benguela Upwelling System revealed by calcareous nannofossil assemblages (ODP Site 1085A)

Middle to late Miocene calcareous nannofossil data of ODP Site 1085 from the eastern South Atlantic off Namibia were analysed to document spatial and temporal changes in surface-ocean circulation, upwelling initiation, and associated productivity.

Our data show that calcareous nannofossils constitute a significant part of the carbonate fraction throughout the investigated interval from 12.5 to 7.7 million years (Ma). Highest numbers of calcareous nannofossils (up to 38,000 × 10⁶ nannofossils g^− 1 sediment) were observed during the intervals 9.9 to 9.7 and 8.7 to 8.0 Ma. These elevated numbers of calcareous nannofossils may generally be linked to the initiation of upwelling at about 10 Ma in the studied region. In contrast, diminished numbers of calcareous nannoplankton, as in the interval 9.6 to 9.0 Ma, probably characterise time intervals of weaker productivity resulting in a decrease of nannofossil carbonate contents in the sediments of Site 1085. This decrease in nannofossil production could be one possible explanation for the major CaCO₃ depression in between 9.6 and 9.0 Ma. Coccoliths of the genus Reticulofenestra are the most abundant taxa. Their occurrences are characterised by changes in the investigated time interval. In addition, Coccolithus pelagicus, Calcidiscus leptoporus and Umbilicosphaera spp. contribute a common part of the assemblage. Calcareous nannofossils account for more than half of the carbonate, with peak contribution up to 80% at 8.8 Ma.     

Calcareous nannofossil biostratigraphy of the Thomel Level (OAE2) in the Lambruisse section, Vocontian Basin, southeast France

The Thomel Level of the Lambruisse section in the Vocontian Basin (southeast France), which is marked by intercalations of black shales and organic-rich marls, accumulated during the oceanic anoxic event 2 (OAE2) occurring in the Cenomanian-Turonian (C-T) boundary interval. Calcareous nannofossil biostratigraphic investigation of this interval revealed a total of five nannofossil zones, corresponding to the UC3-UC8 zones (Middle Cenomanian-Middle Turonian) as defined by Burnett. Biostratigraphically important taxa observed in the section include Cretarhabdus striatus, Axopodorhabdus albianus, Lithraphidites acutus, Corollithion kennedyi, Helenea chiastia, Quadrum gartneri, Q. intermedium, Eiffellithus eximius, Eprolithus octopetalus and E. eptapetalus. The two nannofossil events commonly used in the delineation of the C-T boundary, namely the LO of H. chiastia and the FO of Q. gartneri, occur less than 2 m apart in the studied section. These two bioevents define the limits of the UC6 nannofossil Zone and occur within the Whiteinella archaeocretacea foraminifer Zone. Previous litho- and chemostratigraphic analyses indicate that the δ¹³C profile of the section corresponds well with changes in lithofacies and fluctuations in the total organic carbon (TOC) and calcium carbonate content of the section. Initial increase in the δ¹³C values occurs within the UC3-UC4a undifferentiated zone, coinciding with the onset of the deposition of the organic-rich sediments of the Thomel Level and a drastic decline in the CaCO₃ values. The plateau of high δ¹³C values, on the other hand, occurs within the UC5 zone, between the LO of C. kennedyi and the LO of H. chiastia (and FO of Q. gartneri). This interval of high δ¹³C values also corresponds to the interval of high TOC and low CaCO₃ values. The integrated nannofossil, planktonic foraminifer and δ¹³C data provide a precise biostratigraphic and chemostratigraphic framework of the C-T boundary in the Lambruisse section that can be used in future studies in the Vocontian Basin and allow correlations with other well-studied C-T boundary sections.     

Post-sampling dissolution and the consistency of nannofossil diversity measures: A case study from freshly cored sediments of coastal Tanzania

This study investigates the potentially deleterious effect of prolonged sample storage on the reliability of calcareous nannofossil species abundance and community diversity measures and their subsequent interpretation as paleoceanographic proxies. Nannofossil assemblages from two freshly cored successions of hemipelagic clay were documented over a one-year period using a series of paired smear-slides, the first made from sediment samples within a day of coring and the second either 6 months or 1 year later. Diversity measured by Shannon's H is consistent between the two sets for the majority of samples, however significant changes, both positive and negative, were recorded in a number of cases and appear to be largely due to variations in smear-slide thickness and not to post-sampling dissolution. There is no significant change in nannofossil fragmentation or abundance over time, although the relative abundances of small, dissolution susceptible placoliths of Reticulofenestra minuta do appear to decrease with time in some samples. Counts of mineral grains show that there is a significant loss of fine, 1–2 μm, cubic pyrite within months of drilling, and this, combined with the decline in abundance of R. minuta, suggests that limited pyrite oxidation coupled to carbonate dissolution is occurring. Geochemical analyses confirm that these sediments contain significant concentrations of sulphate one year after sample recovery, which may be the result of gypsum formation associated with the oxidation of pyrite. Estimates of pyrite oxidation suggest that up to 3% of the original calcium carbonate has dissolved in the year after coring, which could account for the observed loss of small placoliths. Effects of this kind are almost certainly confined to hemipelagic sequences rich in organic matter and/or reduced iron but are frequently offset by the exceptional preservation of calcareous microfossils that can occur within such sediments.     

The human bioclimates of Western and South Pacific islands and climate change

The current bioclimates of equatorial Western and tropical South Pacific have been assessed, using the concepts of effective temperature and relative strain as a basis for evaluating likely changes in human comfort regimes as a consequence of global warming. Current bioclimates may be considered marginally stressful for indigenous populations. Global warming will result in changes in the frequency, duration and intensity of physioclimatically stressful conditions.     

Refinements of calcareous nannofossil biostratigraphy at the Miocene/Pliocene Boundary in the Mediterranean region

The high-resolution quantitative study of the calcareous nannofossil assemblages in two Mediterranean deep-sea successions (ODP Sites 969B and 975B) encompassing the Miocene/Pliocene boundary allows the recognition of a set of reliable bioevents useful to detecting the base of the Zanclean stage. The results have been successfully compared with two on-land sections (Cava Serredi, Tuscany, and Montepetra borehole, Marche Region, Central Italy). This study confirms that Ceratolithus acutus and Triquetrorhabdulus rugosus, the markers traditionally used for identifying the Miocene/Pliocene Boundary are very rare in the Mediterranean area and cannot be used for biostratigraphic correlation. Conversely, the absence interval (paracme) of Reticulofenestra pseudoumbilicus and the distribution range of a new species belonging to the Reticulofenestra genus (Reticulofenestra zancleana nov. sp.) show high biostratigraphical potential. The position of the new biohorizons has been compared to those of the planktonic foraminifers events, and correlated to the CaCO₃ cycles reconstructed for the two sections. On the basis of these new nannofossil bioevents, Rio et al.’s (1990) MNN12 biozone is subdivided into three subzones, thus improving the biostratigraphic resolution of the Early Pliocene.     

Bioturbational redistribution of Danian calcareous nannofossils in the uppermost Maastrichtian across the K-Pg boundary at Bidart, SW France

In this paper we present the effects of different tracemakers on the redistribution of calcareous nannofossils throughout the K-Pg boundary at the Bidart section (SW France), along with their consequences for our knowledge of the K-Pg boundary event. Danian calcareous nannofossil assemblages are present in Maastrichtian samples due to infiltration into dark trace fossil infillings proceeding from the earliest Paleogene. This is evidenced by the appearance of abundant paleogene calcareous nannofossils just below the K-Pg boundary, showing the relevance of the trace fossil infillings in the context of the K-Pg boundary event.     

The potential effects of climate change on winter mortality in England and Wales

In Britain death rates from several important causes, particularly circulatory and respiratory diseases, rise markedly during the colder winter months. This close association between temperature and mortality suggests that climate change as a result of global warming may lead to a future reduction in excess winter deaths. This paper gives a brief introductory review of the literature on the links between cold conditions and health, and statistical models are subsequently developed of the associations between temperature and monthly mortality rates for the years 1968 to 1988 for England and Wales. Other factors, particularly the occurrence of influenza epidemics, are also taken into account. Highly significant negative associations were found between temperature and death rates from all causes and from chronic bronchitis, pneumonia, ischaemic heart disease and cerebrovascular disease. The statistical models developed from this analysis were used to compare death rates for current conditions with those that might be expected to occur in a future warmer climate. The results indicate that the higher temperatures predicted for 2050 might result in nearly 9000 fewer winter deaths each year with the largest contribution being from mortality from ischaemic heart disease. However, these preliminary estimates might change when further research is able to make into account a number of additional factors affecting the relationship between mortality and climate.     

A review of indicators of climate change for use in Ireland

Impact indicators are systems/organisms, the vitality of which alters in response to changes in environmental condition. The indicators assessed in this review fall within the impact category of the driver-pressure-state-impact-response (DPSIR) framework. Instrumental records have shown unequivocal changes in climatic conditions over the past 30 years at a global level but impact indicators allow these changes to be monitored at a finer resolution. Our main aim was to review sets of indicators of climate change currently used in various countries and to make recommendations for their use in the Irish environment. We review a preliminary set of climate change impact indicators in five sectors: agriculture; plant and animal distribution patterns; phenology; palaeoecology and human health. Currently, the most effective impact indicators of climate change have proved to be phenological observations of tree developmental stages. The strongest factor limiting the use of indicators is the lack of long-term data sets from which a climatic signal can be extracted.     

Paleocene-Pleistocene benthic foraminiferal evidence of major paleoceanographic events in the eastern South Atlantic (DSDP Site 525, Walvis Ridge)

Benthic foraminifers in the size-fraction greater than 0.073 mm were studied in 88 Paleocene to Pleistocene samples from Deep Sea Drilling Project Site 525 (Hole 525A, Walvis Ridge, eastern south Atlantic). Clustering of the samples on the basis of the 86 most abundant foraminifers (in total, 331 taxa were identified) allowed separating two major assemblage zones: the Paleocene to Eocene interval, and the Oligocene to Pleistocene interval. Each of these, in turn, were subdivided into three minor subzones as follows: lower upper Paleocene (approx. 62.4 to 57.8 Ma); upper upper Paleocene (56.6 to 56.2 Ma); lower and middle Eocene (55.3 to 46.8 Ma); upper Oligocene to middle Miocene (25.3 to 16 Ma); middle Miocene to Pliocene (15.7 to 4.2 Ma); and lower Pleistocene (0.4 to 0.02 Ma), with only minor differences with the previous zone. Some very abundant taxa span most of the column studies (Bolivina huneri, Cassidulina subglobosa, Eponides bradyi, E. weddellensis, Gavelinella micra, Oridorsalis umbonatus, etc.). Several of the faunal breaks recorded coincide with conspicuous minima in the specific diversity curve, thus suggesting that the corresponding turnovers signal the final stages of periods of faunal impoverishment. At least one major bottom-water temperature drop (as derived from δ¹⁸O data) is synchronous with a decrease in the foraminiferal specific diversity. On the other hand, a specific diversity maximum in the middle Miocene might be associated with a δ¹³C increase at approx. 16 to 12 Ma. Highest foraminiferal abundances (up to 600–800 individuals per gram of dry sediment) occurred in the late Paleocene and in the early Pleistocene, in coincidence with the lowest diversity figures calculated. The magnitude of the most important faunal turnover recorded, between the middle Eocene and the late Oligocene, is magnified in our data set by the large hiatus which separates the middle Eocene from the upper Oligocene sediments. Considerably smaller overturns occurred within the late Paleocene (in coincidence with changes in the specific diversity, absolute abundance of foraminiferal tests, and δ¹³C), and in the middle Miocene (in coincidence with a specific diversity maximum and a δ¹³C excursion). New information on the morphology and the stratigraphic ranges of several species is furnished. For all the taxa recorded the number of occurrences, total number of individuals identified and first and last appearances are listed.     

A Skate in the Lowermost Maastrichtian of Southern Sweden

A new skate, Walteraja exigua gen. et sp. nov., is described from the lowermost Maastrichtian Belemnella lanceolata Zone of Balsvik quarry, Kristianstad Basin, southern Sweden. It is the earliest known skate with a largely modern tooth morphology and the only known pre-Cenozoic rajoid displaying a very marked gynandric heterodonty, comparable to that in many living forms. The occurrence of W. exigua in the basal Maastrichtian at Balsvik coincides with a mass occurrence of the small 'deep-water' squaloid shark Proetmopterus hemmooriensis . Most living skates, and virtually all extant squaloids closely related to P. hemmooriensis , inhabit deep and/or cool water environments and do not occur in warm temperate to tropical coastal waters. The Walteraja/Proetmopterus association in a marginal, relatively shallow-water facies of the B. lanceolata Zone adds to other, recently described, unexpected occurrences of Late Cretaceous rajoids and etmopterids/centroscymnids in warm temperate to subtropical shelf environments.     

An indoor mesocosm system to study the effect of climate change on the late winter and spring succession of Baltic Sea phyto- and zooplankton

An indoor mesocosm system was set up to study the response of phytoplankton and zooplankton spring succession to winter and spring warming of sea surface temperatures. The experimental temperature regimes consisted of the decadal average of the Kiel Bight, Baltic Sea, and three elevated regimes with 2°C, 4°C, and 6°C temperature difference from that at baseline. While the peak of the phytoplankton spring bloom was accelerated only weakly by increasing temperatures (1.4 days per degree Celsius), the subsequent biomass minimum of phytoplankton was accelerated more strongly (4.25 days per degree Celsius). Phytoplankton size structure showed a pronounced response to warming, with large phytoplankton being more dominant in the cooler mesocosms. The first seasonal ciliate peak was accelerated by 2.1 days per degree Celsius and the second one by 2.0 days per degree Celsius. The over-wintering copepod populations declined faster in the warmer mesocosm, and the appearance of nauplii was strongly accelerated by temperature (9.2 days per degree Celsius). The strong difference between the acceleration of the phytoplankton peak and the acceleration of the nauplii could be one of the “Achilles heels” of pelagic systems subject to climate change, because nauplii are the most starvation-sensitive life cycle stage of copepods and the most important food item of first-feeding fish larvae. Priority programme of the German Research Foundation—contribution 3.