Significance of ocean carbonate budgets for the global carbon cycle

Changes in the trace gas composition of the atmosphere over glacial–interglacial cycles are linked to changes in the oceanic carbon cycle. This paper examines the role of biologically driven fluxes of organic and inorganic carbon in modifying the carbon dioxide chemistry of the oceans, and the corresponding implications for the partitioning of CO₂ between the atmosphere and ocean. Relevant details of the marine carbon system are presented together with an assessment of the significance of remineralization and dissolution processes. Recent estimates of the marine carbonate fluxes show significant uncertainties and inconsistencies which must be resolved in order to assess fully the role of the oceans' biota in the marine carbon system. Various types of ocean carbon cycle models have been developed in order to interpret the changes in past atmospheric carbon dioxide. Some take account of the role of the oceans' biota, focussing in the main on the cycling of organic matter. Relatively few have considered the role of the carbonate pump and the subtle interactions between organic and inorganic carbon cycling. The significance of carbonate formation and dissolution, and of the effects of global change on the marine carbonate system, for air–sea fluxes of CO₂ are discussed. Finally some recommendations for future research are made in order to improve our understanding of how spatial and temporal variation in marine carbonate fluxes, in conjunction with processes determining the oxidation and burial of organic matter in the oceans, affect levels of CO₂ in the atmosphere.     

On the Evolutionary Foundations of Language

New data on the cognitive capacities of other primates requires a reevaluation of our position on the nature of human language and the factors that led to its development. Pressures on the limited display system of the social primates may have made changes in the vocal tract anatomy of man associated with the development of upright posture of great selective importance. Human vocal tract anatomy may be at least as important as brain capacity in accounting for the origins of human language. An apparent upper age limit on efficient language acquisition in man leads to the "foreign accent" phenomenon. This may have been adoptively significant as a device which helped in the maintenance of a population structure in which rapid genetic change was possible. Embedding in language may represent a cognitive ability that is also reflected in the capacity for cultural variation, and may be extremely important in maintaining efficient population structure and in selecting for increasing intelligence.     

Subcellular Effects of Cytochalasin B and Dimethylsulfoxide on Paramecium aurelia*

SYNOPSIS. Paramecium aurelia syngen 4, stock 57 (sensitive) cultivated in Cerophyl infusion were exposed to cytochalasin B CB and dimethylsulfoxide (DMSO), the solvent for CB, to distinguish between the effects of these agents on a cellular system. DMSO significantly inhibited survival, fission rate, [³H]leucine incorporation, and cell size. CB-treated cells generally had slower division and poorer survival rates than cells exposed to the equivalent DMSO concentration, although the [3H]leucine incorporation was generally greater at the lower CB concentrations than for DMSO alone. As seen by electron microscopy and a new grycerination technic for observing polysomes, DMSO caused nuclear (nucleolar, chromatin) abnormalities as well as membrane degradation and polysomal breakdown; CB caused the formation of aberrant membrane structures and ribosomal tetramers, crystals, and tubes.     

Shell colour polymorphism in a mangrove snail Littorina sp. (Prosobranchia: Littorinidae)

Shell colour polymorphism was examined in populations of a mangrove snail Littorina sp. in Queensland, Australia. Three morphs were recognized, yellow, red and brown, and morph frequencies varied both between widely spaced populations and between islands less than 1 km apart. Morph frequencies also varied with time of year. There was a relationship between shell colour and position on the tree, with yellow snails more often occurring amongst the foliage and brown snails more often on trunks and branches. In some populations yellow snails appeared to survive better than the other morphs, while in other populations there was no difference. The evidence for the maintenance of the polymorphism by natural selection is discussed.     

Effect of osmotic priming, rinsing and storage on the germination and emergence of carrot seed

Carrot seed, osmotically primed in polyethylene glycol solution (273 g/kg water) for 10 days at 15°C, was given 0–5 rinsing cycles, where each cycle comprised agitating the seed in 10 times its own bulk volume of distilled water for 20 to 30 s. Priming decreased the germination and emergence times whether the seeds were rinsed or not, and these effects were maintained even after storage for 450 days. The number of rinsing cycles had no effects, except that seed given five rinsing cycles deteriorated after 270 days storage.     

The effect of ryegrass mosaic virus on carbon assimilation and growth of ryegrasses

The growth of simulated swards of Italian and perennial ryegrass, artificially infected with ryegrass mosaic virus (RMV) or RMV-free, was investigated. During the build up of RMV infection, dry-matter yield was usually decreased in infected swards, and the effect was confirmed when single vegetative regrowths of swards were investigated in detail. The primary cause of lower yields in RMV-infected swards appears to be a decrease in net canopy photosynthesis (maximum decrease about 50%) and an associated increase in dark respiration (maximum increase about 50%). The decrease in net canopy photosynthesis is due primarily to a lowered rate of net photosynthesis of constituent leaves within the canopy. A secondary effect of RMV infection is to decrease tillering (maximum decrease about 30%) which results in a change in canopy structure and in particular a lower leaf area index. In the present experiments, lower light utilization by the swards is less important than the decrease in leaf photo-synthetic efficiency in lowering yield.     

Some Effects of 'Hardening' Carrot Seed

Carrot seed and water were mixed in the ratio of 100 : 70 byweight, kept in a covered petri-dish for 24 h at 20 °C andthen dried by exposure to the atmosphere at 20 °C. Threecycles of this ‘hardening’ treatment gave seed havingembryos 51 per cent longer than those in untreated seed. Thisincrease in embryo length was due mainly to cell division duringhardening rather than to cell expansion. Hardened seed imbibedwater more quickly to start with and germinated and producedseedlings which emerged in the field 3–4 days earlierthan untreated seed. Relative growth-rates during early growthwere similar from both types of seed. At harvests 14 to 21 weeksafter sowing the mean yields of roots from the hardened seedwas 64.0 compared to 59.2 tons per hectare from the untreatedseed. Variations of the hardening treatment were tried but it appearedthat the above treatment was the most effective for enhancingthe rate of germination, although embryo length and numbersof cells per embryo increased progressively with cycles of hardeningup to six cycles. The moisture content of seed ripening in a field at Wellesbournefluctuated diurnally over the same range as that used in theexperiments to produce a hardening effect, but the embryos didnot increase in length during field ripening.     

Personal view. Is it reality or an illusion that liquid‐based cytology is better than conventional cervical smears?

Liquid-based cytology (LBC) has been heralded as the way forward for cervical screening, and as the answer to many of its problems. It is already used as a sole method of cell preparation in many private clinics in the UK. It is being used for colposcopy smears in many NHS clinics and is now being piloted for primary screening in three screening centres in England, as well as one in Scotland and one in Wales. LBC has been welcomed as a new technology because it deals with the problem of specimen adequacy at source, removing responsibility for slide preparation and fixation from the clinician or nurse. It provides uniformly well-fixed preparations that are free of inflammatory exudate and blood, and seem easier to screen than conventional smears. There are many articles in the world literature suggesting that LBC is more accurate than conventional screening, and it is thought likely to reduce the number of false negative tests. The main reasons for piloting LBC in the NHS Cervical Screening Programme (NHSCSP) lie in its potential for reducing screening times and for reducing the numbers of repeats for inadequate tests. LBC is expensive in terms of equipment, capital costs, maintenance, consumables, training, technical preparation time, transportation and disposal of liquid media. Its costs could be justified if they were offset by the money saved from reduced screening time and repeat tests, but only if its accuracy in terms of sensitivity and specificity were proven to be equal to or better than conventional cytology. Although that is generally held to be true by the public and medical profession alike, there is very little hard evidence to support it.     

A comparative analysis of population structuring and genetic diversity in sympatric lineages of freshwater shrimp (Atyidae: Paratya): concerted or independent responses to hydrographic factors?

1. We determined whether two sympatric mitochondrial DNA (mtDNA) lineages of freshwater shrimp (Decapoda: Atyidae: Paratya australiensis) represent biological species and if they had concerted or independent population responses to hydrographic factors in small streams (the Granite Creeks) in southeastern Australia. 2. Allozyme data indicated the presence of two gene pools at sites where the P. australiensis lineages were co‐occurring and the gene pools were statistically assigned with high probability to each respective lineage. This indicated that these mtDNA lineages in P. australiensis were reproductively isolated and thus biological species. 3. Populations of both lineages were genetically homogeneous among lowland sites within streams, but were isolated by steep stream gradients among upland sites and for lowland–upland site comparisons. However, the magnitude of differentiation was markedly different between the two lineages. Allozyme diversity also differed between the two lineages, suggesting that they have different effective population sizes. Thus, differences in the magnitude of genetic divergence among populations were probably because of different life‐history characteristics, including dispersal ability and population size. 4. Genetic population structure was mostly temporally stable, despite the extreme effects of drought during the first year and substantial stream‐flow during the second. However, stable isotope analyses revealed greater local movement in both lineages during the second year, as greater hydrological connectivity provided more opportunities for dispersal. Thus, although lowland populations within streams were genetically homogeneous, stable isotope data indicated that connections may be sporadic and result from accumulated small‐scale movements among refugial pools. 5. Both lineages were therefore found to have similar small‐scale population responses to the unstable habitats of the Granite Creeks. Results highlight the importance of refugia for the capacity of biota to recover from drought and the need for multiple restored patches to reinstate natural population processes (e.g. resilience, recolonization) in degraded systems.     

MODELING CONSUMER INTENTION TO PURCHASE FRESH PRODUCE

The effect of some fresh‐cut carrot label attributes on consumer purchase intention was evaluated using conjoint analysis. The following three attributes were chosen and manipulated: price (high and low), packaging type (polyethylene bags and expanded polystyrene trays) and production process (organic with certification stamp, organic without certification stamp and no information). A complete factorial design was used, and 12 hypothetical packages of fresh‐cut carrot were developed and evaluated by 96 consumers based on their purchase intention. The consumers were divided into four groups with different opinions. Low price and organic with certification label were the favorite choices of the groups. Only one group preferred expanded polystyrene trays. No interactions were exhibited among the attributes in all groups.