Differences In Accumulation Rates Research Articles

Tolerance and accumulation of the trace metals zinc, copper and cadmium in three populations of the polychaete Nereis diversicolor

The comparative tolerance and accumulation of the trace metals zinc, copper and cadmium in populations of the littoral polychaete worm Nereis diversicolor from three sites: (a) heavily metal-contaminated Dulas Bay in Anglesey, north Wales, (b) the Blackwater estuary, Essex, as a control site, and (c) West Thurrock, the Thames estuary as a site of intermediate metal contamination, were investigated. Worms from Dulas Bay did not show increased tolerance to any metal, but worms from West Thurrock showed significantly increased copper sensitivity compared to the worms from Dulas Bay and the Blackwater. Worms accumulated zinc and copper from sediments with raised zinc and copper concentrations, and all three metals from solution in proportion to dissolved concentration. Accumulated metal was not excreted in 21 days and field concentrations of zinc and copper in the worms differed between sites. There was no evidence for inter-populational differences in accumulation rates of zinc and cadmium from solution, but worms from Dulas Bay accumulated copper from solution at a significantly higher rate than did worms from the other two sites. Nereis diversicolor takes up and accumulates zinc and cadmium from solution at similar rates per unit molar exposure, but cadmium is taken up at a greater rate per unit free metal ion molar exposure. Although N. diversicolor from Dulas Bay is exposed to very high availabilities of zinc and copper, accumulation and detoxification mechanisms are sufficient to cope with the extra metal influx (accentuated for dissolved copper) without selection for a metal-tolerant population.

Accumulation in East Greenland Fjords and on the Continental Shelves Adjacent to the Denmark Strait over the Last Century Based on 210Pb Geochronology

Sediment (SAR) and mass (MAR) accumulation rates for the last 100 years are derived from 210Pb profiles of box cores collected in three fjords and on the continental shelf in the Kangerlussuaq region, East Greenland, and on the SW Iceland continental shelf. The MAR is lower on East Greenland (0.09 g/cm²·yr) than on SW Iceland (0.14 g/cm²·yr) because of differences in the biogenic component of the sediments, although SAR is similar. The differences in accumulation rates of the three East Greenland fjords are due to their dominant sediment sources and basin areas. Kangerlussuaq Fjord, the largest fjord, is dominated by iceberg sediment input and has a MAR of 0.43 g/cm²·yr at 50 km from the fjord head. Miki Fjord, the smallest fjord, is dominated by glaciofluvial sediment input with a MAR of 0.29 g/cm²·yr of sediment at 10 km from the fjord head. Nansen Fjord is intermediate in size, with an iceberg-dominated sediment supply; MAR is 1.01 g/cm²·yr near the fjord head and 0.17 g/cm²·yr at 20 km from the fjord head. 137Cs is used as a secondary indicator of sediment source, and the high activity level of 137Cs in Miki Fjord indicates glaciofluvial sediment sources. Zones of constant activity in some of the box cores are attributed to either bioturbation in the surface mixed layer or turbidites. We would be hesitant to extend the recent 210Pb-based accumulation rates to estimate the Holocene accumulation rates.

7Be and 10Be concentrations in recent firn and ice at Law Dome, Antarctica

Over the past three years, the Australian National Tandem for Applied Research (ANTARES) AMS facility at ANSTO has been expanding its sample preparation and measurement capability, particularly for 10Be, 26Al and 36Cl. During this time, ANSTO has continued its collaboration with the AAD and CSIRO Atmospheric Research on the measurement of cosmogenic isotopes from Law Dome, Antarctica. This research program has been supported by the construction of a dedicated geochemistry laboratory for the processing of ice and rock samples for the preparation of AMS targets. Here we present our first results for 10Be concentrations measured in ice cores from three sites at Law Dome and describe the sample processing protocol and aspects of the AMS measurement procedure. These sites are characterised by an eightfold difference in accumulation rate with a common precipitation source. In combination with an established ice chronology, this has enabled some preliminary findings concerning the relationship between the snow accumulation rate and the measured 10Be concentration for Law Dome during recent times. Additionally, we present 7Be and 10Be/ 7Be measurements made for a few surface snow samples from Law Dome and Australia.

Organic-walled dinoflagellate cyst assemblages in the tropical Atlantic Ocean and oceanographical changes over the last 140 ka

A palaeoceanographic reconstruction of the Late Quaternary tropical Atlantic Ocean has been made on the basis of dinoflagellate cyst associations of two sediment cores: the first core was recovered from below the highly productive waters of the equatorial divergence and the second from the oligotrophic western tropical Atlantic Ocean. Palaeoenvironmental indicators for productivity, sea surface temperature (SST) and salinity (SSS) based on selected organic-walled dinoflagellate cyst species have been established. On the basis of these palaeoenvironmental indicators, a strengthened intensity of the equatorial divergence in the eastern region during glacials and cold periods of interglacials has been reconstructed. The highest SST probably occurred around substage 5.5 and might refer to weakest upwelling intensity. In comparison, SST and SSS appear to have been generally higher in the western tropical Atlantic Ocean, with probably enhanced values during glacial intervals. Pronounced differences in accumulation rates and relative abundances of cysts formed by congruentidiacean dinoflagellates and relative abundances of oligotrophic cyst species between the eastern and the western region can be related to differences in palaeoproductivity, suggesting much higher values in the eastern area. The coherence between variation in frequency of the indicators for productivity and the boreal summer insolation and monsoon intensity in the eastern tropical Atlantic Ocean suggests an oceanographic reflection of regional intertropical, rather than boreal, dynamics.

Spectral properties of the Marius Hills volcanic complex and implications for the formation of lunar domes and cones

We have used multispectral data from the Clementine UV‐visible camera to study the volcanic features of the Marius Hills complex and their comparison to other lunar domes and cones. There are several mare units identified in the complex, each with a unique Ti content, as indicated by their 415/750 nm value. The domes in Marius Hills are spectrally identical to the mare plains of the complex, supporting similar compositions. In contrast, most of the volcanic cones of the complex are lower in reflectance, bluer in color, and have weaker mafic absorptions than the mare and domes. The spectral characteristics of the cones can best be explained by fine‐grained crystallization in the spatter that compose the cones. Other lunar cones, such as Mons Esam in northern Tranquillitatis, have spectral properties similar to those at Marius Hills. The Rima Parry cones and their associated dark mantle deposit appear redder with a stronger mafic absorption than the Marius Hills cones. The cones Isis and Osiris in southern Mare Serenitatis, the domes of Rumker Hills, and several domes in northern Mare Tranquillitatis are spectrally similar to adjacent mare units. The Mairan and Gruithuisen domes in northern Oceanus Procellarum have a feldspathic signature characteristic of highland material although they are redder and brighter than adjacent highland soils. They appear to represent highland material that resembles domes rather than actual mare domes, like those at Marius and Rumker Hills. The diversity of lunar volcanic features can best be explained by differences in accumulation rates and cooling of ejected clasts from various eruption styles. Mare domes may have formed at lower effusion rates, thereby allowing lava to construct small shields with slopes <3°. The steeper domes at Marius Hills require higher viscosities resulting from even lower effusion rates and enhanced crystallization in the magmas during the terminal stages of earlier eruptions that emplaced the mare. Cones like Mons Esam, Rima Parry, Isis, and Osiris are aligned along linear rules and are interpreted to result from degassing of near‐surface dikes. In contrast, the cones of Marius Hills show no linear alignment and may result from strombolian eruptions at the terminal stages of earlier effusive eruptions that emplaced the domes and mare in the complex.

Core Top 14C Ages as a Function of Latitude and Water Depth on the Ontong‐Java Plateau

Radiocarbon measurements on core tops from the Ontong‐Java plateau confirm a previous finding by Berger and Killingley [1982] that at any given water depth, cores taken on the equator have higher accumulation rates and younger core top ages than their off‐equator counterparts. Further, these new results fortify the conclusion by Broecker et al. [1991] that the increase in core top radiocarbon age with water depth rules out homogeneous dissolution within the pore waters as the dominant mechanism. Either most of the dissolution must occur prior to burial or it must occur during the first pass through the respiration‐CO2‐rich upper pore waters after which the calcite grains become armored against further dissolution. A puzzling aspect of this new data set is that despite the sizable difference in accumulation rate, the extent of dissolution as measured by either the CaCO3 content or the ratio of CaCO3 in the >150‐µm size fraction to that in the < 63‐µm fraction is no different off than on the equator. In order to reconcile the results of this study with those obtained by Hales and Emerson [1996] using in situ electrodes, it is necessary to call upon calcite armoring.

Freshwater amphipods as biomonitors of metal pollution in surface and interstitial aquatic systems

SUMMARY1. The relationships between levels of metals (Zn, Cu) in the environment (water, sediment) and in the tissues of three species of amphipod crustaceans were investigated in superficial and interstitial ecosystems of the Rivers Rhone and Ain, France.2. Epigean and hypogean amphipods differed in their ability to accumulate Zn and Cu. At all sites, Gammarus fossarum (epigean) showed lower Zn or Cu body concentrations than Niphargus of, rhenorhodanensis or Niphargopsis casparyi (hypogean). Differences were also observed between the two interstitial taxa.3. A significant difference among sites was observed for metal concentrations in sediment. In contrast, no significant inter‐site differences were found for metal concentrations in organisms.4. No significant correlation was found between metal concentrations in the three taxa and quantities of metals in the water. A positive correlation was observed between Zn and Cu body content in Gammarus fossarum and metal level in the sediment. No relationships were found between interstitial amphipods and metal concentrations in the sediment.5. Differences in accumulation rates among the three amphipod species suggest their potential use as biological indicators for monitoring metal pollution.

Neogene carbonate stratigraphy of Ontong Java Plateau (Western Equatorial Pacific): three unexpected findings

ABSTRACTThe Neogene carbonate stratigraphy of five sites drilled on Ontong Java Plateau during Leg 130 reveals a number of patterns which are unexpected, and which we refer to as loss paradox, equatorial insensitivity, and climate paradox. They denote the following unresolved questions. The loss of carbonate at depth (as derived from differences in accumulation rates) is much greater than suggested by the change in carbonate percentages (calculated under the assumption that carbonate dissolution is the cause of loss). This indicates an important role for redeposition processes, such as winnowing (bottom currents), sifting (resuspension and catabatic flow) and episodic sloughing or solifluction (presumably stimulated by earthquakes). Accumulation rates are not markedly increased at the time a site crosses the equator. There are several possible reasons. Equatorial upwelling may be unimportant in controlling sedimentation rates this far in the western Pacific, or its output may be spread over a considerable distance from the equator. Alternatively, increased supply below the equator is compensated for by increased removal (e.g. from resuspension by bioturbation, combined with catabatic flow). It is conceivable that errors in the timescale could also produce the effect seen. There is an overall tendency for agreement between the stratigraphic patterns of carbonate content and of accumulation rates, but neither pattern is readily explained by reference to changes in climate (represented by benthic δ18O) or in sea‐level (as derived from sequence stratigraphy).

Continuous but not intermittent administration of growth hormone to hypophysectomized rats increases apolipoprotein-E secretion from cultured hepatocytes.

Hypophysectomy of female rats has been shown to decrease the serum levels of apolipoprotein E (apoE). Continuous but not intermittent administration of GH to hypophysectomized (HX) rats increases these levels to those of normal rats, indicating that the sexually dimorphic secretion of GH is important in the regulation of apoE metabolism. In this study, these effects of GH were further investigated by studying the biosynthesis and secretion of apoE from isolated hepatocytes. Hepatocytes were isolated from HX rats as well as from HX rats that had received hormonal treatment with T4 and cortisol (C) or T4 and C together with GH given either as two daily sc injections (GH x 2) or as a continuous infusion (GHc). Hypophysectomy decreased by 47% the amount of apoE present in the culture medium after a 4-h incubation. Treatment of HX rats with T4 and C alone or in combination with GH x 2 did not influence the amount apoE present in the medium, whereas treatment with T4, C, and GHc increased the amount of apoE to that of normal controls. The different levels of apoE in the medium was not due to differences in the disappearance of apoE, indicating that it was caused by changes in the rate of apoE secretion. Consistent with this, hypophysectomy decreased the rate of intracellular accumulation of apoE measured by incubation of the cells with [35S]methionine for 0, 8, and 20 min. Treatment with T4, C, and GHc increased the rate of accumulation, but T4, C, and GH x 2 had no effect. The differences in the initial rate of intracellular accumulation of apoE were not due to variations in apoE messenger RNA pools or to differences in the degradation of apoE at a step early in the secretory pathway. These results indicate that the differences in the initial rate of accumulation of apoE results from differences in the translational rate. The major amount of apoE that was secreted to the medium appeared in the high-density lipoprotein fraction, whereas small amounts were present in the very-low-density lipoprotein fraction (VLDL). Hypophysectomy decreased the amount of newly secreted apoE in the VLDL fraction. Only therapy with T4, C, and GHc could restore the normal distribution of apoE in the VLDL fraction. In conclusion, the results indicate that the secretory pattern of GH is involved in the regulation of the apoE secretion by influencing the rate of translation.

The effect of different alleles at the r locus on the synthesis of seed storage proteins in Pisum sativum

Rocket immunoelectrophoresis was used to measure the accumulation of storage proteins in developing cotyledons of two Pisum sativum (pea) genotypes, that were close to isogenic except for the nature of the allele at the r locus. There was a marked decrease in legumin accumulation in the rr (wrinkled-seeded) genotype compared to the RR (round-seeded) genotype. The accumulation of vicilin did not differ greatly between the two genotypes. Pulse-labelling studies indicated that the differences in rates of accumulation of legumin between the rr and RR genotypes were a consequence of differences in rates of protein synthesis. Measurements of relative amounts of specific mRNAs, using cDNA clones as probes, showed lower amounts of legumin mRNA in developing cotyledons of the rr, compared to the RR, genotype. Both vicilin mRNAs and convicilin mRNA, the latter of which shows a similar temporal pattern of expression to those of the major legumin species, are relatively unaffected by the nature of the allele at the r locus. Nuclear run-on transcription experiments indicated no differences in the rate of synthesis of legumin transcripts in the rr and RR near-isolines. The consequences of homozygosity for the r allele on storage protein mRNA levels in vitro may be mimicked by manipulating the sucrose concentration of the culture medium.

Uptake of lead, chromium, cadmium and cobalt byCladophora glomerata

The kinetics of heavy metal uptake by algal cells involves two stages. The first phase is very rapid, occurring immediately after initial contact with the cell and usually lasting for less than 30 minutes. The second phase is slow and extended, and has been observed to continue for more than one month. The slow phase appears to be active and related to metabolic activities of the cell. The relative importance of these two stages depends on the organism involved. Previous studies dealing with uptake of heavy metals by freshwater algae have noted differences in accumulation rates of individual elements. The purpose of the present communication is to describe the time-course of uptake of lead, chromium, cadmium and cobalt by Cladophora glomerata (L.) Kutz., a common filamentous green alga in freshwaters.

Profitability and Accumulation

It is common in location theory, regional growth theory, and development theory to assume that differences in rates of accumulation are correlated with differences in rates of profit and then to seek factors that would explain why rates of profit (or unit production costs) differ. This paper argues that this procedure is invalid, for there is evidence that profitability and accumulation are not well correlated. Even in well behaved models, there may be net capital flows towards low profit regions or industries (and some examples demonstrate that such behavior does indeed occur); furthermore, the concept of a profit is not relevant to such enterprises as independent commodity producers, union pension funds, and the state; exports of steel from Brasil are not based on low production costs. With this assumption out of the way, spatial economic theories can become more sensitive to such other factors as class agency.

Resistance, susceptibility and accumulation of glyceollins I–III in soybean organs inoculated with Phytophthora megasperma f. sp. glycinea

The expression of resistance and susceptibility to inoculation with zoospores of Phytophthora megasperma f. sp. glycinea race l was determined in roots, hypocotyls, and cotyledons of etiolated and green seedlings and in leaves of soybean cvs Harosoy (rps1) and Harosoy 63 (Rps1). Gene-specific resistance was demonstrated in all organs tested, except for cotyledons of etiolated seedlings. In each case higher concentrations of the glyceollins accumulated in resistant than in susceptible reactions; the differential being greatest in hypocotyls and smallest in roots. The relative proportions of glyceollins I, II and III varied with the organ, exposure of the seedlings to light, the interaction type and the incubation period. Glyceollin I was relatively the most abundant isomer in roots and to a lesser extent in hypocotyls. Glyceollin III was relatively the most abundant isomer in leaves. Major differences in accumulation rates were observed in time-course experiments and, after reaching a maximum, all three isomers decreased in leaves and glyceollin I decreased in hypocotyls, suggesting that concentrations and hence isomeric proportions were finely controlled by rates of biosynthesis and metabolism.

Accumulation of modern sediment in Quinault submarine canyon

Twenty box cores have been studied from Quinault submarine canyon, a major pathway between the Washington continental shelf and the deep sea for silt and clay originating from the Columbia River. Sediment accumulation rates (on a 100-yr time scale) are calculated from profiles of excess 210Pb and of 137Cs. Accumulation rates decrease with increasing distance downcanyon: from 14 × 10 −2 g cm −2 yr −1 in the upper canyon (lower head) to 3 × 10 −2 g cm −2 yr −1 in the lower canyon. In the upper canyon (lower head), channel-floor areas have a higher mean accumulation rate ( 12 × 10 −2 g cm −2 yr −1 ) than channel-wall areas ( 5 × 10 −2 g cm −2 yr −1 ). The difference in accumulation rate between channel-floor and channel-wall areas indicates preferential accumulation (i.e., focusing) in topographic lows. The decrease in accumulation rate (from high rates in the channel floors of the upper canyon to low rates in the lower canyon) may be caused by progressive depletion of a nepheloid-layer source and/or may be an artifact of sediment focusing in the upper canyon. The silty clay and clayey silt accumulating in the canyon show no significant trend in grain size or clay mineralogy with depth in cores or with distance downcanyon. The lack of sorting probably results from the transport of sediment in aggregate form, with a nearly random distribution of size and mineralogy within aggregates. Quinault Canyon is accumulating approximately 5.5 × 10 5 MT of sediment yr −1. The lithogenic component (64%) accounts for 1–4% of the Columbia River discharge. Similarity of sediment-trap deposition rates (including storm events) and 210Pb accumulation rates indicates that the vertical flux is a major input of sediment to Quinault Canyon and that storms are important in the accumulation of sediment on a 100-yr time scale.

Effect of an allozyme polymorphism on regulation of cell volume.

Biochemical differences have been described among allozymes1–4, but the physiological consequences (that is, physiological phenotypes) of such differences have only rarely been demonstrated5–7. Such a relationship is necessary both to the argument that natural selection maintains allozymic diversity in natural populations and for understanding biochemical mechanisms of adaptation8. We report here a genotype-dependent difference in the rate of cellular free amino acid accumulation during adjustment to hyperosmotic conditions in the mussel Mytilus edulis. The product of the Lap locus in M. edulis is the lysosomal enzyme aminopeptidase-I (AM-I; E.C.3.4.11.-) which hydrolyses oligopeptides to their constituent amino acids9. Total AM-I activity is positively correlated with salinity; a 120% increase in salinity increases AM-I activity twofold10–13. Adjustment to hyperosmotic stress in osmoconforming marine bivalves, including M. edulis, involves rapid accumulation of cellular free amino acids14,15. The biochemical properties of AM-I, and its activation by salinity changes, suggest that it is important for providing cellular free amino acid pools during adjustment to hyperosmotic stress11. We show that individuals carrying the allele for high catalytic efficiency (kcat) accumulated cellular amino acids more rapidly than other genotypes. The difference in accumulation rate was also demonstrated by an interruption of hyperosmotic adjustment, which resulted in genotype-dependent rates of amino acid excretion. These results demonstrate the role of AM-I in the physiological processes that regulate cell volume. Thus, differing catalytic properties of allozymes are manifested as phenotypic differences at the physiological level and provide a mechanism for the known selective mortality of mussels in natural populations7.

Late Cenozoic Sedimentation and Erosion on the Rio Grande Rise

The Rio Grande Rise is capped by a thick sequence of pelagic carbonate and reefal sediments, ranging in age from upper Cretaceous to Recent. The north flank of the Rise is dissected by deep erosional canyons which expose the near-horizontally layered calcareous strata as outcrops on the canyon walls. Lithologic and stratigraphic studies of twenty-two piston cores from a small area ($$~25 km^{2}$$) on the north flank allow an interpretation of the depositional environment on the Rise during the late Cenozoic, and place constraints on the origin of the erosional canyons. A major unconformity of Pliocene age was penetrated by 12 of the cores. Sediments beneath the unconformity range in age from upper Eocene to lower Pliocene, and correspond approximately in depth with that of equivalent strata recovered at DSDP Site 357 nearby. Pliocene-Pleistocene sediments above the unconformity show systematic regional differences in rate of accumulation, extent of reworking, and the presence of stratigraphic gaps. On the flanks of canyons, an apparently continuous depositional record extends back to ~370,000 y.B.P., with some evidence of effects of winnowing and terrigenous dilution. On the adjacent ridge axes, local variations (on a scale of km or less) in topography or near-bottom flow have created "pockets'* of virtually uninterrupted Pliocene-Pleistocene sedimentation separated by regions where Pleistocene sediments are virtually missing. The ridge axes are current-swept today, and contain considerable local variation in sedimentation rates and in the presence of erosional unconformities. Of several models considered to account for the origin and development of the erosional canyons, the one most consistent with the available lithologic and stratigraphic information includes: (a) initiation of canyon cutting during the late Cretaceous or early Tertiary when portions of the Rise were at or above sea level; (b) deepening of the canyons between the latest Miocene and late Pleistocene via a sequence of erosional episodes alternating with relatively quiescent depositional intervals; and (c) cessation of major canyon cutting in the late Pleistocene (~370,000 y.B.P.).

Cone-Induction Response of Douglas Fir to Form of Nitrogen Fertilizer and Time of Treatment

Cone production increases of 2.5, 5.0 and 1.5 times that of control were obtained the year following treatment with 400 lb nitrate nitrogen per acre (1 lb/acre = 1.12 kg/ha), applied 6 weeks before vegetative bud break, at the start of bud break, and 10 days after the midpoint of the bud break period, respectively, on 20-year-old Douglas fir (Pseudotsugamenziesii (Mirb.) Franco.). Cone counts of 15, 26, 72, 142 and 155 were obtained from 0, 200, 400, 800 and 1600 lb nitrate nitrogen per acre, applied to 13-year-old trees during early bud break. Ammonium nitrogen, applied at the same rates and times, was ineffective for stimulation of cone production on either age of tree. There were no differences in rate of accumulation of total nitrogen in buds and foliage, shoot-growth responses, or total number of buds per shoot due to form of nitrogen. Nitrate treatment enhanced cone production through a reduction in bud failure during the shoot elongation period. These results suggest responses are not primarily due to improved mineral nutrition, but to a specific chemical stimulation from critically timed changes in type of nitrogen metabolism. Possible influences of temperature and rainfall on natural cone crop periodicity and on proper timing of nitrate treatment are discussed.

Physiological studies of differentiation in Mytilus edulis: II. Accumulation of phosphate in isolated blastomeres and polar lobes

Accumulation rates of radioactive phosphate were determined for eggs, isolated blastomeres, and polar lobes of Mytilus edulis. A fractionation of the labeled phosphate in eggs indicates that 96 per cent enters the labile compounds and the remaining enters nonlabile compounds. No regional differences in uptake rates of phosphate into either labile or nonlabile compounds could be demonstrated in the fertilized egg prior to cleavage. After cleavage the uptake of phosphate into the AB and CD blastomeres correlates with surface area. Isolated polar lobes and D blastomeres, however, exhibit a significantly lower accumulation rate of phosphate than AB and C blastomeres. Limiting factors in phosphate uptake are considered and it is possible that the differences in accumulation rates may reflect changes at the cell surface.