鳀鱼的生物量、渔业及其生物学特征

IntroductionThe Yellow Sea is characterized by a shallow continental shelf. High tides and seasonally varying mon-soons,freshwater discharge from surrounding landmasses and large amounts of sediments transported intothe sea as well as the effect of the Kuroshio current have strong effects on the environment in these areas.Productivity of an ecosystem may be measured in terms of abundance of the adult population and recruitmentof new year classes.Japanese anchovy(Engraulis jap onicus) is cons…     

Acidification in Norway the norwegian monitoring programme for long range transported air pollutants

Man-made emissions of sulphur and nitrogen in Europe is acidifying the precipitation in Norway. Extensive research activities in the seventies (the SNSF-project) clearly showed that acidification has a strong impact on the environment in Southern Norway. In order to further evaluate the cause-effect relationships and changes over time, a monitoring programme covering deposition, surface- and groundwater, soil, fish populations and invertebrates was initiated by the Norwegian Ministry of Environment. Intensive studies are performed in all regions of Norway by the Norwegian Institute for Air Research (NILU), the Norwegian Institute for Water Research (NIVA), the Norwegian Institute for Nature Research (NINA), the Norwegian Forest Research Institute (NISK), Geological Survey of Norway (NGU) and the University of Bergen (UiB). The Norwegian Pollution Control Authority (SFT) is responsible for the overall co-ordination of the programme and the funding of air and water monitoring, while the Directorate for Nature Management (DN) is funding the monitoring of fish and invertebrates.     

Corn and culture in central andean prehistory

The prehistoric development and spread of domesticated maize varieties in the highlands of Peru, unlike the drier coastal deserts, is little known because ancient maize remains in this area survive mainly as fragments, kernels, and cob parts. An analysis of fragmented charred maize from prehistoric households (A.D.450 to 1500) in the Mantaro Valley reveals a developmental sequence of maize varieties for Highland Peru. The evidence indicates an adoption of large-kernelled maize varieties beginning in the Late Intermediate (A.D. 1000). This is centuries later than a similar change in maize, associated with the Wari expansion, that occurred in coastal areas, and indicates minimal Wari impact in the Mantaro Valley.     

Sustained Swimming Speeds of Dolphins

Observations of fout large groups of dolphins suggest that they are able to swim at a sustained speed of 14 to 18 knots. The blackfish are able to maintain speeds of about 22 knots, and one killer whale seemed able to swim somewhat faster. This implies that the apparent coefficient of surface friction remains approximately constant for dolphins from 6 to 22 ft long, as is the case for rigid bodies.     

Remote sensing of the fram strait marginal ice zone

Sequential remote sensing images of the Fram Strait marginal ice zone played a key role in elucidating the complex interactions of the atmosphere, ocean, and sea ice. Analysis of a subset of these images covering a 1-week period provided quantitative data on the mesoscale ice morphology, including ice edge positions, ice concentrations, floe size distribution, and ice kinematics. The analysis showed that, under light to moderate wind conditions, the morphology of the marginal ice zone reflects the underlying ocean circulation. High-resolution radar observations showed the location and size of ocean eddies near the ice edge. Ice kinematics from sequential radar images revealed an ocean eddy beneath the interior pack ice that was verified by in situ oceanographic measurements.     

Upwelling: oceanic structure at the edge of the arctic ice pack in winter

Observations taken on an expedition into the Arctic Ocean north of Spitsbergen indicated the existence of a region of wind-driven upwelling along the edge of the ice pack. Models underestimate the 12-kilometer width of the upwelling region.     

Impact of acid precipitation on freshwater ecosystems in Norway

Extensive studies of precipitation chemistry during the last 20 yr have clearly shown that highly polluted precipitation falls over large areas of Scandinavia, and that this pollution is increasing in severity and geographical extent. Precipitation in southern Norway, Sweden, and Finland contains large amounts of H⁺, SO⁼ ₄, and NO^? ₃ ions, along with heavy metals such as Cu, Zn, Cd, and Pb, that originate as air pollutants in the highly industrialized areas of Great Britain and central Europe and are transported over long distances to Scandinavia, where they are deposited in precipitation and dry-fallout. In Norway the acidification of fresh waters and accompanying decline and disappearance of fish populations were first reported in the 1920s, and since then in Sørlandet (southernmost Norway) the salmon have been eliminated from several rivers and hundreds of lakes have lost their fisheries. Justifiably, acid precipitation has become Norway's number-one environmental problem, and in 1972 the government launched a major research project entitled ‘Acid precipitation — effects on forest and fish’, (the SNSF-project). Studies of freshwater ecosystems conducted by the SNSF-project include intensive research at 10 gauged watersheds and lake basins in critical acid-areas of southern Norway, extensive surveys of the geographical extent and severity of the problem over all of Norway, and field and laboratory experiments on the effect of acid waters on the growth and physiology of a variety of organisms. Large areas of western, southern, and eastern Norway have been adversely affected by acid precipitation. The pH of many lakes is below 5.0, and sulfate, rather than bicarbonate, is the major anion. Lakes in these areas are particularly vulnerable to acid precipitation because their watersheds are underlain by highly resistant bedrock with low Ca and Mg contents. Apart from the well-documented decline in fish populations, relatively little is known about the effects of acid precipitation on the biology of these aquatic ecosystems. Biological surveys indicate that low pH-values inhibit the decomposition of allochthonous organic matter, decrease the species number of phyto-and zooplankton and benthic invertebrates, and promote the growth of benthic mosses. Acid precipitation is affecting larger and larger areas of Norway. The source of the pollutants is industrial Europe, and the prognosis is a continued increase in fossil-fuel consumption. The short-term effects of the increasing acidity of freshwater ecosystems involve interference at every trophic level. The long-term impact may be quite drastic indeed.     

CO2 exploitation and genetic diversity in winter varieties of oilseed rape (Brassica napus); varieties of tomorrow

We investigated the CO_2] exploitation and genetic diversity inthree old and three new winter varieties of oilseed rape (Brassicanapus L.). Plants were cultivated in growth chambers with 360 ppmCO₂ and 700 ppm CO₂ under conditions simulating a normalgrowth season. Exposed to elevated CO₂ the stomatal conductance(g_s) and the maximum photosynthesis capacity (A_max) werereduced and the dry biomass and the total seed-number were increased.The response in seed-yield differed among the varieties; it was increased inthree varieties and decreased in three. The analysis of variance (ANOVA)showed that there were Treatment- and Week-effects on the g_s, andthere were Variety-, Week- and Treatment-effects on the A_max. Itwas also evident that there were a Variety- and Variety-agegroup-effect onthe seed-yield, but the Variety-agegroup-effect could not explain theVariety-effect. When either or both covariates (seed-number andbiomass) were included in the model, the covariates themselves had asignificant effect and it became evident that there was a Treatment-effecton the seed-yield.From AFLP (amplified fragment length polymorphism) markers adendrogram was constructed by the UPGMA method (unweightedpair-group method using the arithmetic averages) and [G _ST wascalculated for all possible subsets of the varieties. The three old varietiescomprised the densest cluster and were also more genetically diverse thantwo of the three new varieties. Varieties with clear changes amongCO₂ levels were rather genetically diverse.Thus, the varieties represent different traits, which could be exploited infuture breeding of oilseed rape.     

Competition Affects the Production of First Backcross Offspring on F1-hybrids, Brassica Napus × B. Rapa

Summary Interspecific F₁-hybrids may arise in fields with transplastomic oilseed rape where B. rapa occurs as a weed. Spilled seeds, including transplastomic F₁-hybrids with B. rapa, may germinate, which creates an opportunity for production of transplastomic BC₁ with B. rapa as father (BC_1r). Field trials were made with three different proportions of B. napus, B. rapa and F₁-hybrids and three different densities. Contrary to most studies on how plant competition affects introgression between oilseed rape and B. rapa, this study focused on offspring produced on F₁-hybrids, where the F₁-hybrids had oilseed rape as maternal parent. We estimated the BC_1r production in all combinations of proportion and density, and found that B. rapa sired from 0.6–7.8% of the offspring. At the proportion with the highest abundance of F₁-hybrids the entire paternity was assessed. There was a significant density effect on the production of BC_1r but the effect differed among proportions. Both the highest and lowest frequencies of BC_1r were obtained at high plant density. Neither the proportion nor density affected the number of BC_1r per square-meter significantly. Biomass components decreased significantly from low to intermediate density, whereas a further increase in density only affected the thousand-seed weight significantly. On the basis of the results from the present experiment we conclude that introgression of transgenes from transplastomic oilseed rape to B. rapa seems most likely at current field densities of B. napus, and when B. rapa is an abundant weed.     

Effects of increased atmospheric CO2 on varieties of oat

The effects of elevated CO₂ were investigated on seven Scandinavian varieties of oat. Three landraces (before 1920), two varieties of intermediate‐age (1920‐1940), and two recent varieties (after 1940) were exposed to two atmospheric CO2 concentrations (approx. 380 and 700 ppm). Elevated CO₂ increased the yield 7% on average but with large variation between varieties. The yield‐response was variety specific and not related to the age of the variety. The mean seed number increased about 11%, with an increase in the landraces and diverging responses within the other age groups. The mean seed weight was reduced about 5.5%, with small changes within the landraces and diverging results within the two other age‐groups. The mean dry biomass was increased about 20%; the landraees had a marked increase in dry biomass, while the response in the other varieties ranged from a large increase to a small decrease. These different responses among varieties provide a spectrum of trait‐combinations desirable in breeding oats for different purposes. The quality of the seeds was not affected by the elevated CO₂.