Low Productivity Conditions Research Articles

Stability of bubbles in a linear elastic medium: Implications for bubble growth in marine sediments

Methane bubbles in muddy fine‐grained sediments grow initially through a process of elastic expansion, punctuated by discrete fracture events (LEFM‐growth). The ability of the surrounding sediments to support a stress and actively resist expansion can, under conditions of low gas production or high sediment toughness, result in the cessation of growth and the presence of stable bubbles. Thus, it is possible for a bubble to stop growing despite the presence of a source in the sediments that continues to produce gas. This contrasts with growth of bubbles in a fluid medium, which cannot support a stress and so will continue to grow as long as a surrounding source provides gas. This “no‐growth” condition is the result of the coupling between gas supply (methane production or supersaturation) and the sediment mechanics. Here we quantify this condition and present a criterion for the switch between no‐growth and the LEFM growth regimes. We apply this theory to the sediments of Eckernförde Bay, in the Kiel Bight, Germany, and despite the absence of measurements for the key sediment mechanical properties, we can provide a qualitative explanation for the sizes and shapes of the observed bubble population with depth in the sediment. We also show how the release of hydrostatic pressure can stimulate growth, by pushing otherwise stable bubbles into the LEFM growth regime. This could provide a mechanism for the release of bubbles during periods of low water, such as during low tide or wave events.

Application of the Digital Kreybig Soil Information System for the delineation of naturally handicapped areas in Hungary

EU’s Common Agricultural Policy encourages maintaining agricultural production in less favored areas (LFA) to secure both stable production and income to farmers and to protect the environment. Recently the delimitation of LFAs is suggested to be carried out using common biophysical diagnostic criteria on low soil productivity and poor climate conditions all over Europe. The criterion system was elaborated by European Commission’s Joint Research Center (JRC) and its operational implementation comes under member state competence. This process requires the existence of an adequate national spatial soil information system with appropriate data structure and spatial resolution as well as a proper methodology for its analysis. Hungary possesses an appropriate, nationwide, 1:25,000 scale legacy dataset originating from the national soil mapping project, which was digitally processed and developed into the Digital Kreybig Soil Information System (DKSIS). In the paper we present how DKSIS was applied for the identification and delineation of areas in Hungary concerned by the common biophysical criteria related to soil. Soil data linked to soil profiles and SMUs were jointly spatially analyzed for the compilation of nationwide digital maps displaying spatial distribution of specific limiting factors.

Interactions between leaf lifespan and defoliation frequency in temperate and tropical pastures: a review

AbstractIn continuously stocked swards or pastures the frequency at which individual tillers and individual leaves are defoliated by ruminant livestock, relative to leaf lifespan of the grass species within the sward, determines the proportion of each leaf defoliated before senescence, and hence the efficiency of harvesting of herbage. In this paper, sets of data obtained in a range of climatic conditions and with a range of grass species are used in order to document this relationship. It is shown that the frequency of defoliation of individual tillers or individual leaves is closely linked to the average stocking density used within a period of time for maintaining a steady state sward or pasture height, herbage mass or leaf area index. Consequently, any decrease in herbage growth rate should lead to a decrease in the efficiency of harvesting of herbage and then to a more than proportional decrease in total herbage consumption by ruminant livestock. These effects will be more important for grass species having short leaf lifespan than for species with long lifespan. In rotational stocking, the link between herbage growth rate and frequency of defoliation of leaves can be broken by controlling the grazing interval, so any decrease in herbage growth would not be systematically associated with a decrease in efficiency of harvesting of herbage. Rotational stocking should be more efficient than continuous stocking in low herbage production conditions, while in high herbage production systems rotational and continuous stocking would have similar efficiency. The implications of these conclusions for the management of swards and pastures to meet different objectives are discussed briefly.

Quantum yields of phytoplankton photosynthesis in the Gulf of Aqaba (Elat), Northern Red Sea

The Gulf of Aqaba (Elat) is characterized by oligotrophic waters and low productivity conditions in summer, when the euphotic zone of the stratified water column is severely nutrient-depleted. Winter is moderately productive, when mixing injects nutrients into the lit upper waters. The annual phytoplankton cycle and the bathymetric distribution of biomass and photosynthetic activity in the Gulf are analyzed in conjunction with the harvesting and utilization of light by cells. The harvesting of light energy at any depth is shown as an interaction between the optical properties of cells, a*, and the intensity and spectral distribution of the underwater light field. The efficiency by which phytoplankton cells utilize the absorbed light energy is the quantum yield of the photosynthetic process, Φ. The efficiency of light utilization by phytoplankton depends on the nutrient status of cells, their photoacclimation to ambient light, and the irradiance to which they are exposed. We show that the seasonal and spatial changes in the quantum yield of photosynthesis control the wax and wane of the different phytoplankton assemblages in the Gulf, thereby ultimately determining the flux of energy fueling all of the Gulf's planktonic and benthic biota.

An expanded Cretaceous−Tertiary transition in a pelagic setting of the Southern Alps (central-western Tethys)

An integrated micropalaeontological (planktonic foraminifera and calcareous nannofossils), mineralogical and stable isotope investigation was carried out across the Cretaceous/Tertiary (K/T) boundary in a previously undescribed hemipelagic section (Forada section) cropping out in the Piave River Valley (Southern Alps, Belluno Province, NE Italy). Our results suggest that an apparently complete K/T transition with an expanded basal Danian is preserved in the Forada section. The K/T boundary is marked by a ca. 1.5-cm-thick clay interval intercalated in the pelagic carbonates of the Scaglia Rossa Formation. The boundary clay, characterised by an iridium anomaly, is constituted by a basal 1–2 mm-thick “green layer” and an overlying “red layer”. Below the boundary clay, the calcareous nannofossil Micula murus Zone and the planktonic foraminiferal Plummerita hankteninoides Zone, that characterise the terminal Maastrichtian in complete sections, have been identified. Virtually all the calcareous plankton biohorizons normally utilised in the early Danian have been recognised. Interestingly, the ranking of the various biohorizons is the same observed elsewhere if considering the single plankton groups separately, while several inconsistencies emerge if considering the relative succession of the two calcareous plankton groups simultaneously. We caution to infer hiatuses on a section based only on the spacing of the biohorizons of a single group because of the risk of diachroneities in the stressed early Danian environment. By comparing the “distance” of the key biohorizons (i.e. the First Occurrence (FO) of Cruciplacolithus primus and the Last Occurrence (LO) of Parvularugoglobigerina eugubina) from the boundary clay at Forada and in other complete classical sections, we have inferred that the early Danian is expanded in the Forada section. The section seems ideally suited for studying the recovery pattern of the pelagic ecosystem and calcareous plankton communities in the aftermath of the K/T catastrophe in a pelagic setting of the western central Tethys. The adaptive radiation of planktonic foraminifera was very rapid in contrast with the delayed diversification of coccolithophores. The latter show a ca. 21-cm-thick “dead zone” that is followed by a long-lasting survival interval (ca. 180-cm-thick, that might represent some 200 kyr) dominated by persistent Cretaceous coccolithophores and calcareous dinoflagellate Thoracosphaera spp. The temporal pattern in recovery of the coccolithophore and planktonic foraminiferal communities is decoupled as well pointing to their varying sensitivities to the K/T perturbation. It appears that the ecospace occupied by coccolithophores in the terminal Maastrichtian was occupied in the initial Danian by the calcareous dinoflagellates ( Thoracosphaera spp.), that remained a significant component of the assemblage up to the base of the Prinsius dimorphosus Zone of Romein [Romein, A.J.T., 1979. Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletins, 22. 231 pp.], probably in the early Chron C29n. On the contrary, planktonic foraminifera seem to reach stable conditions earlier, in the late Cruciplacolithus primus Zone. The early Danian interval considered is also characterised by low Sr/Ca ratio of the biogenic carbonates that would suggest dramatically low coccolithophore productivity conditions, in agreement with previous flux studies. We speculate that the altered ecological structure of phytoplankton community and the low productivity of coccolithophores severely affected the efficiency of the transfer of organic carbon from the photic zone to the deep ocean, thus supporting the early Danian “living ocean” model of D'Hondt et al. [D'Hondt, S., Donaghay, P., Zachos, J.C., Luttenberg, D., Lindinger, M., 1998. Organic carbon fluxes and ecological recovery from the Cretaceous–Tertiary mass extinction. Science 282, 276–279].

Growth of Carbon Nanotubes by Combustion of Ethyl Alcohol

Many preparations of carbon nanotubes have been developed in the last decade, such as arc discharge, plasma-enhanced chemical vapor deposition, simple thermal chemical vapor deposition by pyrolysis of ethyl alcohol, etc. Here we present a simple growth technique of carbon nanotubes by combustion of ethyl alcohol. Pt filament can be employed as substrate, ethyl alcohol as carbon source, and iron nitrate as catalyst precursor. We have characterized the morphology of carbon nanotubes at the different synthesis conditions by both SEM and TEM. In our experiment, we also use other metal as substrate, such as Cu, top of pin, and other catalyst precursor of different concentration, such as nickel nitrate. This technique has some advantages, such as low cost, large production, and flexible reaction conditions, etc. We can use this technique to synthesize carbon nanotubes on metal substrate directly. So this technique has protential applications for fabricating nano-electrical devices.

CO 2 emissions and heat flow through soil, fumaroles, and steam heated mud pools at the Reykjanes geothermal area, SW Iceland

Carbon dioxide emissions and heat flow through soil, steam vents and fractures, and steam heated mud pools were determined in the Reykjanes geothermal area, SW Iceland. Soil diffuse degassing of CO 2 was quantified by soil flux measurements on a 600 m by 375 m rectangular grid using a portable closed chamber soil flux meter and the resulting data were analyzed by both a graphical statistical method and sequential Gaussian simulations. The soil temperature was measured in each node of the grid and used to evaluate the heat flow. The heat flow data were also analyzed by sequential Gaussian simulations. Heat flow from steam vents and fractures was determined by quantifying the amount of steam emitted from the vents by direct measurements of steam flow rate. The heat loss from the steam heated mud pools was determined by quantifying the rate of heat loss from the pools by evaporation, convection, and radiation. The steam flow rate into the pools was calculated from the observed heat loss from the pools, assuming that steam flow was the only mechanism of heat transport into the pool. The CO 2 emissions from the steam vents and mud pools were determined by multiplying the steam flow rate from the respective sources by the representative CO 2 concentration of steam in the Reykjanes area. The observed rates of CO 2 emissions through soil, steam vents, and steam heated mud pools amounted to 13.5 ± 1.7, 0.23 ± 0.05, and 0.13 ± 0.03 tons per day, respectively. The heat flow through soil, steam vents, and mud pools was 16.9 ± 1.4, 2.2 ± 0.4, and 1.2 ± 0.1 MW, respectively. Heat loss from the geothermal reservoir, inferred from the CO 2 emissions through the soil amounts to 130 ± 16 MW of thermal energy. The discrepancy between the observed heat loss and the heat loss inferred from the CO 2 emissions is attributed to steam condensation in the subsurface due to interactions with cold ground water. These results demonstrate that soil diffuse degassing can be a more reliable proxy for heat loss from geothermal systems than soil temperatures. The soil diffuse degassing at Reykjanes appears to be strongly controlled by the local tectonics. The observed diffuse degassing defines 3–5 elongated N–S trending zones (000–020°). The orientation of the diffuse degassing structures at Reykjanes is consistent with reported trends of right lateral strike slip faults in the area. The natural CO 2 emissions from Reykjanes under the current low-production conditions are about 16% of the expected emissions from a 100 MWe power plant, which has recently been commissioned at Reykjanes.

Fishing under low productivity conditions is further delaying recovery of Northwest Atlantic cod (Gadus morhua)

Excessive and unsustainable fishing mortality was the predominant factor in the depletion of Northwest Atlantic cod (Gadus morhua) stocks. However, despite imposition of severe catch restrictions for over a decade, stocks have mostly failed to recover at predicted rates. A number of explanations have been considered. Our analysis of demographic characteristics of 12 of these stocks indicates that recent productivity over the northern portion of the range is much lower than 20 years previous when several stocks recovered from less severe declines. Main contributing factors are, in rank order, increased natural mortality, decreased body growth, and in a few cases, reduced recruitment rates. Continued fishing in directed and bycatch fisheries is also an important factor. Under current conditions, we estimate negative or very low (<2% per year) average growth rates in eight stocks. If fishing ceases, growth rates of >5% would be expected in six stocks, with >10% in four of these. Although productivity is low, we conclude that fishing mortality is further delaying recovery.

Expression of Fetal Hemoglobin among Adult Human Erythroblasts Is Associated with an Altered Expression Pattern for the Transcription Factor c-Myb.

The c-Myb transcription factor plays a central role in regulating growth and differentiation during definitive erythropoiesis. In addition, c-Myb expression has been previously linked to GATA-1 expression and hereditary persistence of fetal hemoglobin. Here we examined a potential role for c-Myb in signaled expression of fetal hemoglobin (HbF) among primary adult human erythroblasts. Initial experiments were performed to determine the expression pattern of c-Myb under conditions of low fetal hemoglobin production (CD34 cells cultured over 14 days in media supplemented with erythropoietin (EPO) alone). Quantitative PCR performed on cells sampled on days 2, 5, 8, 11, and 14 demonstrated highly regulated c-Myb expression. A dramatic increase (>30 fold) in c-Myb mRNA was measured between days 5 and 8 as the committed progenitor cells differentiated to the proerythroblast stage. That increase was followed by a 3-fold reduction in c-Myb during terminal differentiation. Western blotting of nuclear extracts obtained on days 7 and 14 in EPO cultures corroborated with the quantitative PCR analyses. Electrophoretic mobility shift assays performed using day 7 and day 14 nuclear extracts showed a shifted major band with a c-Myb consensus probe. That major band was competed by unlabeled c-Myb probe on both days. Moreover, day 14 extracts repeatedly revealed two additional bands that were not competed suggesting the possibility of other complexes binding to the Myb motif or changes in c-Myb conformation during terminal differentiation. Chromatin immunoprecipitation assays also revealed preliminary evidence for Myb binding directly to beta globin locus. When compared to low HbF culture conditions (EPO; HbF <1%), cells grown in high HbF conditions (erythropoietin + stem cell factor + TGF-beta (EST); HbF>35%) demonstrated a distinct pattern of c-Myb expression. Relative to the low HbF conditions, high HbF expressing cells had reduced c-Myb levels on day 7 followed by increased levels on day 14. These results suggest that c-Myb possesses highly regulated patterns of expression and DNA binding during erythroid maturation. In addition, the association of changes in c-Myb expression patterns with HbF production suggests that this growth-related transcription factor may help regulate fetal hemoglobin synthesis in patients with beta-hemoglobinopathies.

Trans-Mediterranean comparison of geochemical paleoproductivity proxies in a mid-Pleistocene interrupted sapropel

Sapropel layers in the sediment record of the Mediterranean Sea reflect periods of climate-induced elevated marine production associated with precessional minima. Some of these layers feature interruptions that represent centennial-to-millennial returns to the predominantly low-productivity conditions of this sea. We have measured multiple geochemical paleoproductivity proxies in the interrupted sapropel layer that corresponds to insolation cycle 90 (955 ka) at 1-cm intervals in a four-site transect from the Balearic Basin to the Levantine Basin to assess similarities and differences in its expression at the four locations. The interrupted sapropels are similarly divided by an organic-carbon-poor interval into an upper layer in which organic carbon concentrations reach 2–7 wt.% and a lower layer in which they peak between 1 and 3 wt.%. The interruption was essentially synchronous in the Balearic Basin, the Tyrrhenian Basin, and the Ionian Basin, but it was delayed and shorter in the Levantine Basin. Lighter nitrogen isotope compositions consistently accompany higher organic carbon accumulation rates in the sapropel layers, which implies a shift from coccolith-dominated organic matter production towards a mode of primary production in which cyanobacteria were important during times of sapropel deposition. Organic carbon isotopic compositions become heavier as organic carbon accumulation increases at three of the locations, which is consistent with elevated productivity. However, they become lighter at the Levantine Basin site, which suggests greater delivery of isotopically light fluvial waters to this part of the Mediterranean Sea. The local paleoclimate conditions conducive to sapropel formation evidently were not completely uniform across the Mediterranean region but their occurrences were synchronous. Moreover, the co-existence of an essentially same-age interruption of the sapropels at the four locations shows that climate could change rapidly and concordantly across the region at much less than precessional intervals.

Factors affecting the periphytic diatom community in Mediterranean coastal wetlands (Emporda wetlands, NE Spain)

Species composition and ecological preferences of the most important periphytic diatom taxa were studied in lentic ecosystems in the salt marshes of Emporda wetlands (NE Spain). Correspondence analysis with the diatom communities suggested that water confinement/flooding gradient and productivity of the system were the principal factors affecting diatom distribution in the salt marshes of Emporda wetlands. Hierarchical analysis clusters allowed 5 diatom assemblages be distinguished, each one characteristic of different degrees of confinement and productivity. Bacillaria paradoxa appeared as the most characteristic species in low confinement and high productivity conditions. Navicula perminuta and N. salinarum were representative of flooding and low productivity conditions. During maximum confinement and low productivity situations Cocconeis placentula dominated the diatom community. When maximum confinement was attained in the waterbodies with higher productivity, this dominance was shared with Nitzschia archibaldii. The 39 species considered proved to be tolerant to salinity and nutrients (nitrogen, phosphorus and organic matter) variability. This seems to be a prerequisite for survival in salt marshes where the very dynamic nature of the system results in a large variability of the physical and chemical water composition.

Influence of environmental conditions on the production of phenazine-1-carboxamide by Pseudomonas chlororaphis PCL1391.

Pseudomonas chlororaphis PCL1391 produces the secondary metabolite phenazine-1-carboxamide (PCN), which is an antifungal metabolite required for biocontrol activity of the strain. Identification of conditions involved in PCN production showed that some carbon sources and all amino acids tested promote PCN levels. Decreasing the pH from 7 to 6 or decreasing the growth temperature from 21 to 16 degrees C decreased PCN production dramatically. In contrast, growth at 1% oxygen as well as low magnesium concentrations increased PCN levels. Salt stress, low concentrations of ferric iron, phosphate, sulfate, and ammonium ions reduced PCN levels. Fusaric acid, a secondary metabolite produced by the soilborne Fusarium spp. fungi, also reduced PCN levels. Different nitrogen sources greatly influenced PCN levels. Analysis of autoinducer levels at conditions of high and low PCN production demonstrated that, under all tested conditions, PCN levels correlate with autoinducer levels, indicating that the regulation of PCN production by environmental factors takes place at or before autoinducer production. Moreover, the results show that autoinducer production not only is induced by a high optical density but also can be induced by certain environmental conditions. We discuss our findings in relation to the success of biocontrol in the field.

Petrographic and geochemical study of organic matter in surficial laminated sediments from an upwelling system (Mejillones del Sur Bay, Northern Chile)

A study of recent laminated sediments, accumulated in the oxygen minimum zone of Mejillones Bay (Northern Chile), shows that the organic matter is autochthonous and deposited under varying oceanographic conditions. Sedimentary units dominated by light laminations have low values of total organic carbon, total nitrogen and sulphur, and Chaotoceros content, coupled with high values of yellow amorphous organic matter. These were deposited under conditions of low primary productivity, favoring the recycling of the major part of metabolizable organic matter in the water column, and the accumulation only of non-metabolizable organic matter in the bottom sediments. In contrast, a unit rich in dark laminations with high values of total organic carbon, total nitrogen and sulphur, shows high values of brown and black AOM, and Chaetoceros content. This sedimentary unit reflects increased flocculation of organic particles during a period of high productivity and fast transit of organic material through the column water, thus diminishing the recycling of metabolizable organic matter and its accumulation with non-metabolizable organic matter in the sediments. Finally, a unit characterized by presence of both light and dark laminations was formed by abrupt alternations of the two oceanographic states described previously.

Omapatrilat increases renal endothelin in deoxycorticosterone acetate-salt hypertensive rats

Vasopeptidase inhibitors are a new class of antihypertensive drugs that are single molecules having dual inhibitory action on angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The best known drug in this class is omapatrilat, which has been proposed to be more efficacious than ACE inhibitors because of its ability to inhibit NEP and prevent the breakdown of atrial peptides and bradykinin. However, survival of endothelin (ET) may also be enhanced and therefore, NEP inhibitors may have limited efficacy under conditions of low renin and high ET production. The purpose of the current study was to contrast the effects of the ACE inhibitor, enalapril, with omapatrilat in a model of established hypertension where ACE inhibitors are ineffective, the deoxycorticosterone acetate (DOCA)-salt-treated rat. Two weeks after starting DOCA-salt treatment, rats were given either enalapril (10 mg/kg/day) or omapatrilat (30 mg/kg/day) for 5 days. Mean arterial pressure (MAP) measured by radiotelemetry in untreated DOCA-salt rats increased from 102±2 to 181±12 mm Hg ( P<.05) as a result of DOCA-salt treatment for 3 weeks. MAP was unaffected by either enalapril (189±3 mm Hg) or omapatrilat (184±8 mm Hg). DOCA-salt treatment significantly increased urinary ET excretion compared to baseline (1.6±0.2 vs. 0.5±0.1 pmol/day). Administration of omapatrilat significantly increased urinary ET excretion in DOCA-salt rats (2.9±0.4 pmol/day) compared to enalapril-treated (1.6±0.2 pmol/day) or untreated (1.5±0.1 pmol/day) rats. These results indicate that combined ACE/NEP inhibition does not lower blood pressure in a model of established hypertension with high ET activity. These results also support the hypothesis that combined ACE/NEP inhibition can increase renal ET production.

A sediment–nutrient–oxygen feedback responsible for productivity variations in Late Miocene sapropel sequences of the western Mediterranean

Cyclic sediments observed throughout the Mediterranean during the Late Miocene have been related to precessional forcing of ocean stratification. Individual couplets, typically 2-m-thick sequences of sapropels and diatom-rich marls, can be reliably traced from western Spain to Crete, and were formed in restricted marginal basins. Micropaleontological evidence indicates paradoxically that the organic carbon-rich sapropels were formed under low productivity conditions marked by surface water stratification and deep anoxia, whereas the diatom-rich marls were formed under high productivity conditions marked by upwelling. Here we present geochemical evidence, mainly from detailed phosphorus determinations and paleo-redox proxies, indicating that a sediment–nutrient–oxygen feedback (herein dubbed the SNO Effect) is in part responsible for driving the observed productivity variations. During stratification, anoxic conditions in these basins cause the release of the limiting nutrient phosphorus from reducible oxide phases in the sediments. Basin stagnation causes the buildup of phosphorus below the photic zone. Subsequent overturn driven by precessionally-driven winds injects phosphorus-rich bottom waters into the photic zone. The biotic response to this overturn is high productivity in marls directly overlying the sapropels culminating in diatom mat formation. Exhaustion of the stored excess phosphorus results in lower productivity marls, which grade back into sapropels due to lower wind stresses and the return of stagnant basin conditions. These findings indicate that the SNO Effect may in part be responsible for precessional-scale productivity variations observed in parts of the Mediterranean, and perhaps present in other restricted ocean basins, like the Miocene Monterey Formation and the modern Santa Barbara Basin.

Agricultural supply response and poverty in Mozambique

This paper identifies key causal factors behind farmers’ marketing decisions in Mozambique. A two-step decision making process is outlined. Farmers decide, first, whether or not to participate in the market. Next, they decide how much to sell. The model is estimated using a Heckman switching regression approach. The key importance of non-price factors such as risk, technology and transport infrastructure come out clearly. Marginal effects are calculated for poor and nonpoor households and broken down into a market participation and a quantity (sales value) component. The marginal effects for the poor are not substantially different from those of the nonpoor. This suggests that differences in area-based characteristics (especially risk and technology) are more influential in the commercialization process than differences in how the poor and the nonpoor respond to incentives. Moreover, interventions to promote market access are likely to solicit a greater volume of additional supply from peasants entering the market for the first time than from existing market participants stepping up their production and sales. To achieve pro-poor rural growth it is essential to address explicitly the conditions of high-risk, low productivity and low capital endowments of poor farmers.

Meiofauna and sedimentary organic matter off Central Chile: response to changes caused by the 1997–1998 El Niño

Quantitative surveys of metazoan meiofauna were carried out in an upwelling region off Central Chile (36ºS). During May 1997 and May 1998, coinciding with the onset and end of El Niño, five benthic stations (respectively 27, 34, 64, 88, and 120 m depth), from the middle of Concepción Bay to the edge of the adjacent continental shelf, were sampled. The sedimentary organic matter biopolymeric fraction (proteins, carbohydrates and lipids) and chloroplastic pigments were also assessed. Total meiofauna abundance and biomass increased significantly between sampling dates at the mid-bay and inner shelf sites, from 1474 ± 354 to 5035 ± 291 individuals 10 cm –2 and from 2618 ± 332 to 5241 ± 903 individuals 10 cm –2, respectively. The relative importance of copepods in the top 2 cm increased at all sites (except in the bay mouth). During May 1998, meiofauna, especially nematodes, penetrated deeper in the bay, as well as in the inner and middle shelf sediments. Changes observed in meiobenthos structure among sites and periods were attributed to the higher oxygenation of bottom waters during the summer of 1998 (i.e. El Niño conditions). This was most evident at sites such as the mid bay, where during non-El Niño years, oxygen-deficient conditions prevail. A decrease of organic matter quantity and quality, related to low primary productivity conditions in 1998 (El Niño), apparently caused few changes in meiofauna structure. A positive correlation between Thioploca and the meiofauna biomass was observed in May 1997, whereas in May 1998 no relationship was found.

Angiotensin, fibrinolysis, and vascular homeostasis

There is strong evidence that imbalance of the fibrinolytic system is involved in the pathogenesis of ischemic cardiovascular events. A reduction in fibrinolytic function may also mediate part of the adverse response of the vasculature to conditions of low nitric oxide production. Because reduced nitric oxide activity predisposes to the development of atherosclerosis, imbalance of the fibrinolytic system is heavily implicated in the development of cardiovascular pathology. The renin–angiotensin system exerts substantial control over the fibrinolytic system, and pharmacologic interventions that reduce the activity of angiotensin II also have favorable effects on fibrinolytic balance and on the incidence of adverse cardiovascular events. This review summarizes the evidence for a link between activation of the renin–angiotensin system, fibrinolytic imbalance, and cardiovascular pathology.

Differences in Shoot Size and Allometry between Two Evergreen Broad-Leaved Shrubs, Aucuba japonica Varieties in Two Contrasting Snowfall Habitats

, an evergreen broad-leaved shrub. Aucuba Japonica var. borealis is widely distributed in heavy snowfall areas in Japan and is covered, shaded and physically pressured by snow for more than four months of the year. On the other hand, var. japonica is widely distributed in light snowfall areas. The sizes of new shoots and leaves were significantly different between the two varieties with different critical shoot sizes for flowering. The average new shoot dry mass of var. borealis was about one third of that of var. japonica. Despite the differences in growing conditions and shoot size, no significant differences were observed in the allometry of their shoot organs between the two varieties. Large new shoots had thicker and longer stems per biomass than small shoots because of their larger pith volume. The large shoots showed higher efficiency of stem growth per invested biomass and had a higher rate of annual height increase than small shoots. When the size of new shoot rapidly increased from year to year, i.e. the plants are growing well, initiation of flowering was postponed and vegetative growth continued. Small new shoots were tolerant of low productivity conditions but traded vertical growth for an increase in matter allocation to leaves.

Temporal variability in the northern Arabian Sea oxygen minimum zone (OMZ) during the last 225,000 years

The northern Arabian Sea is one of the few regions in the open ocean where thermocline water is severely depleted in oxygen. The intensity of this oxygen minimum zone (OMZ) has been reconstructed over the past 225,000 years using proxies for surface water productivity, water column denitrification, winter mixing, and the aragonite compensation depth (ACD). Changes in OMZ intensity occurred on orbital and suborbital timescales. Lowest O2 levels correlate with productivity maxima and shallow winter mixing. Precession‐related productivity maxima lag early summer insolation maxima by ∼6 kyr, which we attribute to a prolonged summer monsoon season related to higher insolation at the end of the summer. Periods with a weakened or even non‐existent OMZ are characterized by low productivity conditions and deep winter mixing attributed to strong and cold winter monsoonal winds. The timing of deep winter mixing events corresponds with that of periods of climatic cooling in the North Atlantic region.