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Stable isotopes of bulk sediment and well preserved tests of planktonic and benthic foraminifera from midlatitude NE Atlantic DSDP Site 551 (Goban Spur) provide the first estimates of carbon isotope gradients within the water column at a lower bathyal site during the Cenomanian/Turonian boundary interval (CTBI). The CTBI carbon isotope excursion is prominent (up to 2parts per thousand shift in delta(13)C) in the bulk (coccolith) signal, but less pronounced (approximately 0.5 parts per thousand shift in delta(13)C) in planktonic and benthic foraminifera. This difference indicates a very steep (13)C gradient in the upper water column and a very efficient biological pump during the CTBI carbon isotope excursion. We suggest significantly increased seasonal primary production in the uppermost water column with an enhanced shallow water chlorophyll maximum as a cause for this steep carbon isotope gradient. Deep-water and surface-water temperature changes during the CTBI are estimated using benthic and planktonic foraminiferal oxygen isotopes. Warm deep-water masses (13-16degreesC) and a low temperature gradient within the water column prevailed in the late Cenomanian. Additional warming (approximately 2degreesC for both surface and deep water) occurred in the latest Cenomanian prior to CTBI black shale deposition. This pattern of CTBI black shale deposition during a temperature maximum is also evident at two low latitude locations (ODP Site 1050, Blake Nose and Tarfaya, southern Morocco). (C) 2003 Published by Elsevier B.V.

Koljö Fjord and Havstens Fjord on the Swedish west coast are, like many silled fjords in Scandinavia, characterized by strong stratification and stagnant bottom water with periodically occurring low-oxygen and anoxic conditions. High organic production together with a stable water-column, very low tidal activity and existence of the sill create an ideal foundation for low-oxygen conditions to develop. The aim of this study was to find out how the fjord environments developed during the later part of the Holocene and, especially, how and when the low-oxygen conditions evolved. To achieve these goals, sediment cores were dated (210Pb and 14C) and x-rayed, the distribution of benthic foraminifera was analysed and their content of the stable isotopes d18O and d13C was investigated. In both fjords, the climate proved to be of importance for the environment and it seems that increased freshwater runoff increased the primary production between 500 bc and ad 500. Increasing freshwater runoff not only increased primary production but, at least since ad 1880, also made the water stratification stronger and the deep water more stagnant. Stagnant conditions are the main cause of the development of periodic anoxia and formation of laminated sediments in Koljö Fjord from ad 1930 to 1980 and in Havstens Fjord from ad 1950. In Koljö Fjord, the isostatic land rise and the shallow sill are the most important reasons for a general change from an almost normal saline deep-water environment to a brackish environment in ad 500. At that time the sill depth passed the pycnocline mean depth of 15 m. For Koljö Fjord, this is a threshold value of the depth for the quality of the deep water, marine or brackish.

Living (stained) benthic foraminifera were studied in the deepest part (116 m) of the classical marine study area, the Gullmar Fjord on the Swedish west coast. This is a silled fjord with a strongly stratified water column where stagnant conditions temporarily develop in the deeper parts. The aim of this study is to determine how the living foraminiferal assemblage develops with seasonal variations in bottom water hydrography and primary production in the surface water. From August 1993 to December 1994, monthly hydrographic and oxygen measurements were made. Parallel undisturbed sediment cores were taken using a Multiple-corer. Foraminifera from the >63 μm fraction were stained with Rose Bengal to separate living from dead specimens. Monthly values of the surface water chlorophyll a content were also available and give a measure of the primary production. During spring 1994 the dominant foraminiferal species, Stainforthia fusiformis, multiplied its population size by seven times during one month as a consequence of food input from the spring phytoplankton bloom. The abundance of this species correlates positively with the surface water chlorophyll a content. Populations of several other species also increased during the spring of 1994. A deep-water inflow in February 1994 may have triggered reproduction of several foraminiferal species, recognized as a temporary population decline. We also compared our results with Hoglund’s (1947) foraminiferal study, performed in the same area in the summer of 1927. We found that a major alteration trending towards a more opportunistic low oxygen tolerant fauna has occurred since then.

Tri-n-butyltin (TBT) has been used in the marine environment as a toxic agent in antifouling paints, but unfortunately it also has negative effects on non-target organisms in the environment. In this study, intact coastal sediment was exposed for seven months to three levels of TBT corresponding to nominal additions of 0.00, 0.02 and 2.00 nmol TBT per g dry sediment. This paper presents the first attempt to find out how living benthic foraminifera respond to TBT. Increased foraminiferal abundance in the 0.02 nmol mesocosm could be an effect of decreased predation (competition), since other representatives of meiofauna and macrofauna tended to be less tolerant to TBT. Increasing toxicity in the most contaminated mesocosm group (2.00 nmol) resulted in a less abundant foraminiferal population suggesting that TBT affects the foraminiferal community.

The deep Gullmar Fjord on the Swedish west coast may be subject to a trend of decreasing oxygen content of the bottom-water. Due to a non-uniform frequency of oxygen measurements before and after 1980, and small differences in the minimum concentrations, it is difficult to assess with certainty if this is true or not. We have used benthic foraminifera from three ultra-high resolution sediment records to try to find out if such a trend exists. The sediment records comprise the time between 1930 and 1996, with an almost year-based temporal resolution. The foraminiferal records show a significant change in faunal composition during the mid-1970's when it altered from a common Skagerrak fauna to an assemblage characterized by an opportunistic, low oxygen tolerant species; Stainforthia fusiformis. This species is an indicator of low oxygen environments of many Scandinavian fjords. The timing of this faunal change coincides with one of the first recorded severe low oxygen events in the Gullmar Fjord in the winter of 1973/1974. The change suggests that the Gullmar Fjord has actually been subject to a decrease in bottom-water oxygen concentrations. The reason for this change is not clear but here, for the first time, we present sediment records that suggest that there is a causal relation between variations in the North Atlantic Oscillation (NAO) indices and the marine environment. In the early 1970s the NAO-indices altered from a mainly negative phase towards a mainly positive period which is still ongoing. Positive NAO-indices (winter values) in the Skagerrak region are generally marked by westerly winds which normally prevent the exchange of bottom-water in the fjords, i.e., the oxygenation of the sea floor and the supply of oxygen to benthic life.

The Koljo fjord on the Swedish west coast is a silled fjord characterised by strong stratification and stagnant bottom water, with periodically occurring hypoxic or anoxic conditions. In the Koljo fjord, renewal of the deep water generally occurs during winter. This study investigates how living benthic foraminifera react to hydrographic variations, periodic oxygen deficiency and variations in primary production. A series of monthly hydrographic measurements was made from August 1993 to December 1994, combined with sediment sampling along a (12–43 m) depth transect at five different sites. Monthly values of surface chlorophyll-a were available. Two periods of hypoxia to anoxia with one intervening period of oxic conditions, together with two autumn phytoplankton blooms and a spring phytoplankton bloom, made it possible to achieve the aims of this study. Below the pycnocline, three foraminiferal species: Elphidium excavatum clavatum , Elphidium incertum and Elphidium magellanicum represented more than 95% of the fauna. When oxygen content was very low, the foraminiferal fauna decreased but did not die out completely. A deep-water inflow in January 1994 caused the oxygen content to rise, but the foraminiferal population did not start to grow until three months later when the spring phytoplankton bloom sedimented out. Under oxic conditions, food availability seemed to limit the foraminiferal population. In itself, a very high organic content in the sediments does not seem to be a suitable food source; it is more likely that fresh phytoplankton is a potent food for these foraminifera. Reproduction of E. excavatum clavatum and E. incertum seems to have been triggered by increased food supply and sudden fluctuations in hydrographic variables. These foraminifera appear to grow from juvenile to adult in less than a month.

The effect of intracellular free Ca2+ ([Ca2+]i) on the intracellular aggregation of Chlamydia trachomatis serovars L2 and E in McCoy and HeLa cells is investigated. Loading the cells with the Ca2+ chelator MAPT/AM (1,2-bis-5-methyl-amino-phenoxylethane-N,N-n'-tetra-acetoxymethyl acetate), thereby decreasing the [Ca2+]i from 67 to 19 nM, decreased the number of cells with a local aggregation of chlamydiae in a dose-dependent manner. Neither the attachment nor the uptake of elementary bodies (EBs) was, however, affected after depletion of Ca2+ from the cells. There was no significant difference in the level of measured [Ca2+]i between infected and uninfected cells. Reducing the [Ca2+]i also significantly inhibited chlamydial inclusion formation. Differences in the organization of the actin filament network were observed in response to [Ca2+]i depletion. In Ca(2+)-depleted cells, where few EB aggregates were formed, few local accumulations of F-actin were observed in the cytosol. These results suggest that the aggregation of EBs in eucaryotic cells requires a normal homeostasis of intracellular Ca2+. By affecting F-actin reorganization and putatively certain Ca(2+)-binding proteins, [Ca2+]i plays a vital role in the infectious process of chlamydiae.

Upon contact with the eukaryotic cell, Yersinia pseudotuberculosis increased the rate of transcription of virulence genes (yop), as determined by in situ monitoring of light emission from individual bacteria expressing luciferase under the control of the yopE promoter. The microbe-host interaction triggered export of LcrQ, a negative regulator of Yop expression, via the Yop-type III secretion system. The intracellular concentration of LcrQ was thereby lowered, resulting in increased expression of Yops. These results suggest a key role for the type III secretion system of pathogenic bacteria to coordinate secretion with expression of virulence factors after physical contact with the target cell.

In a previous 16-month seasonal study on living (stained) benthic foraminifera from two fjords on the Swedish west coast, it was reported that foraminifera proliferated in response to phytodetritus input; the strongest response came from the opportunistic species Stainforthia fusiformis. In this study, our objective was to find out if that phytodetritus input resulted in a change in the carbon isotopic composition of the foraminiferal tests. We also wanted to examine if variations in salinity and temperature (due to seasonality or deep-water exchanges) were reflected in the δ18O values. From S. fusiformis that were obtained from the Havstens Fjord (20 m) and the Gullmar Fjord (119 m) during the 16-month study, we developed a time series of δ18O and δ13C. After the spring blooms in the Havstens and the Gullmar Fjord, decreases of about 0.2‰ to 0.3‰ in the foraminiferal δ13C values were noted; in the Gullmar Fjord after the autumn blooms, decreases of the same order were also noted. Comparing the Havstens and the Gullmar Fjord, we found a 1‰ difference in both δ13C and δ18O; we attribute this to hydrographic differences between the two fjords. Using calculated values of δ18O, together with the measured ones, we noticed that S. fusiformis in the Gullmar Fjord seems to calcify close to equilibrium with respect to the oxygen isotopes. During autumn, water temperatures were relatively high in the Havstens Fjord, and foraminiferal abundance in the fjord was also high after a phytodetritus input; but, the measured δ18O values do not reflect these higher temperatures. This apparently contradictory combination of results might be explained by a varying δ18O composition of the water during the year, which counterbalances the temperature effect.