Assessing environmental soil quality in rural areas

A base line study into the environmental quality of soils in the rural areas of the province of Zeeland, the Netherlands, was performed. The polder-landscape in this area was developed in a complex history of floodings and land-reclamation. Samples from 67 sites, at a density of roughly one per 25 km², were analyzed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in addition to a physicochemical characterization by pH(KCl), dry solids, organic matter, and clay content. At about 2/3 of the sites samples were taken at more than one depth. Fluoride and pesticides were determined in partly overlapping selections of 30 samples. Four land use classes were distinguished (arable land, grass land, orchards, uncultivated), and samples were labelled by region within the province. Data evaluation was aided by a recursive statistical approach, whereby statistical tests confirm and strengthen geochemical reasoning. Single- and multivariate statistics were used both as exploratory tools and as a measure of significance and relevance of conditions and processes. In general the environmental quality of the soils is satisfactory. Exceedence of the legal standards for natural background values at more than one site occurs for Cd, Cu, Hg and the pesticides DDT/DDE, dieldrin and HCH, at most by a factor of three. High levels of Hg appear related to arable land use; enhanced levels of Cu are found in orchards. High Cd levels primarily seem to follow a regional or geological pattern; yet, a relation with arable land use and clayey soils cannot be excluded. Pesticides are not detected in grass land, incidence is highest in orchards as well as in uncultivated areas. DDT levels appear to be generally inherited from the past. Variation in soil type as described by the macro physico-chemical characteristics is essential in explaining the variation in concentration level of the potential contaminants. Variations with depth also appear largely related to concurrent variation in soil properties. For As redox conditions and hydrological regime seem of importance, in addition to the geologic history. The influence of atmospheric input is inferred for Pb. The available data do not fully resolve the causes for the regional pattern that remains when the influences of soil type, geology, and land use have been taken into account. In addition to current concentration levels, the base line study offers general insight as to what degree variations in potential contaminants are of natural or anthropogenic origin. A succession of similar studies at suitable time intervals, each with a new selection of sampling sites, may constitute an evolving, flexible monitoring system. When putting up a monitoring system, authorities should weigh the advantages and disadvantages of a network composed of fixed sites against this alternative.     

Community metabolism of intertidal flats in the Ems-Dollard estuary

To obtain an insight into the flux of carbon through intertidal sediments of the Ems-Dollard estuary, the annual cycles of gross benthic primary production and community respiration were measured at six stations, together with a set of environmental parameters. In a stepwise multiple regression analysis it was shown that temperature alone and temperature plus viable bacteria explained 50 and 70% respectively of the observed variation in community respiration. Other variables, including the rate of primary production and amount of organic carbon in the sediment were less important. The rate of primary production could not be fitted adequately into a multiple regression equation. The annual values of community respiration (177–794 gO₂·m^-2·yr^-1) and primary production (82–628 gO₂·m^-2·yr^-1) were within the range of published values. except for one station in the vicinity of a wastewater outfall, which had an extreme production (average 984 gO₂·m^-2·yr^-1). At four stations, annual community respiration exceeded primary production by 40%. It is concluded that the main carbon flux within the sediment, from CO₂ to benthic primary producers, to benthic consumers and from there to CO₂ again,was completed within a month or so, leaving untouched the large bulk of organic matter within the sediment. Possible effects of wastewater discharges on community metabolism are discussed.Publication No. 43 of the project Biological Research in the Ems-Dollard Estuary     

Age-related shifts in the diet composition of southern elephant seals expand overall foraging niche

Southern elephant seals are important apex predators in a highly variable and unpredictable marine environment. In the presence of resource limitation, foraging behaviours evolve to reduce intra-specific competition increasing a species’ overall probability of successful foraging. We examined the diet of 141 (aged 1–3 years) juvenile southern elephant seals to test the hypotheses that differences between ages, sexes and seasons in diet structure occur. We described prey species composition for common squid and fish species and the mean size of cephalopod prey items for these age groups. Three cephalopod species dominated the stomach samples, Alluroteuthis antarcticus, Histioteuthis eltaninae and Slosarczykovia circumantarcticus. We found age-related differences in both species composition and size of larger prey species that probably relate to ontogenetic changes in diving ability and haul-out behaviour and prey availability. These changes in foraging behaviour and diet are hypothesised to reduce intra-specific food competition concomitant with the increase in foraging niche of growing juveniles.     

Twenty years of salt marsh succession on a Dutch coastal barrier island

After a formerly grazed salt marsh was released from cattle grazing, changes in plant species composition were monitored for 20 yr, using vegetation maps and permanent plots. Three areas, differing in age and nutrient status were compared. The number of plant species and plant communities decreased.Elymus athericus (Elytrigia pungens) became dominant in most plant communities after 5–20 yr on the oldest and most productive salt marsh. In younger areas it took more time forE. athericus to become dominant. At least 7 cm of clay seemed to be a prerequisite for this plant species to increase in dominance. The results from monitoring over decades are discussed in view of the knowledge on succession over centuries as derived from a chronosequence.     

Reintroduction of eelgrass (Zostera marina) in the Dutch Wadden Sea; review of research and suggestions for management measures

Eelgrass (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km² in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km² eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal flats. The most suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level.     

Social regulation of egg-laying by queenless honeybee workers (Apis mellifera L.)

Summary If a honeybee (Apis mellifera L.) colony loses its queen and remains queenless, a small percentage of the workers will develop into egg-layers and subsequently will produce males. The process of differentiation into laying and non-laying workers is accompanied by a great deal of aggression within the colony. In this study, I tried to establish the relationship between the potential to become egg-layers and behavioural differences at the individual level. To eight observation hives, I introduced 200 individually marked workers of similar age and observed their behavioural differentiation during a queenless period. Shortly after the first egg-laying worker appeared, the marked workers were dissected in order to determine their level of ovarian activation. The future laying-workers seemed to be slightly more involved in the rearing of new queens than other workers. As reported by other authors, aggression was mostly directed towards workers with activated ovaries. Only a very small number of aggressive workers were aggressive; on an average, slightly fewer of these marked workers had activated ovaries. Aggression resulted in physical damage in only a small number of cases. The possible disadvantage of aggression for the bees under attack is discussed, as well as the possible benefit for the aggressors. Evidence is presented that the most detrimental effect of aggression for bees under attack is the fact that they lose considerable quantities of food through trophallaxis to other workers. Workers with activated ovaries withdrew inside empty cells significantly more often than other workers, possibly to avoid attacks. Aggressive workers were (almost) never seen to receive food from the bees they attacked. It is suggested that by preventing other workers from becoming egg-layers, aggressors increase their own chances of future reproduction.     

Simple and reliable methods for the fixation,mounting and staining of small and delicate marine plankton for light microscopic identification

The fixation capacity of mixtures of acrolein, glutaraldehyde, and tannic acid, was investigated to arrive at a fixative for small and delicate marine plankton that is more universal than the current selective fixatives. A mixture containing 4% acrolein, 4% glutaraldehyde and 2% tannic acid added 1:1 to the cell suspension proved to be satisfactory. Mounting of the material in euparal before staining is recommended. Of several dyes tried, fuchsin acid proved suitable for observation of flagella and cell shapes. Delafield haematoxylin staining gave the best results for internal details. Fuchsin base staining, requiring a complex procedure, is recommended when it is necessary to search for flagellar hairs as found in Ochromonas spp. Schedules for the fixation, mounting and staining are given.     

OLAND生物脱氮系统运行及其硝化菌群的分子生物学检测

采用两阶段限氧自养硝化 -反硝化生物脱氮系统 (oxygen limitedautotrophicnitrificationanddenitrificationsystem ,以下简称OLAND)处理高氨氮、低COD的废水 .应用内浸式多聚醚砜中空膜 ,实现了污泥的完全截留 ,阻止了生物量的大量洗脱 ,并通过控制溶氧在 0 .1～ 0 .3mgL-1之间 ,实现了硝化阶段出水中氨氮与亚硝态氮浓度的比例达到最适值〔1 (1.2± 0 .2 )〕 ,从而为第二阶段的厌氧氨氧化提供理想的进水 ,进而获得较高的脱氮率 .同时应用荧光原位杂交技术对硝化阶段不同时期硝化菌群的变化进行分子生物学检测 ,揭示了随溶氧浓度的降低 ,氨氧化菌的数量基本保持恒定、亚硝酸氧化菌的数量略有减少的变化规律 ,并且发现 ,在两阶段限氧自养硝化 -反硝化生物脱氮系统中氨氮的氧化主要是由Nitrosomonassp .完成 ,亚硝酸的氧化主要由Nitrobactersp .完成 .图 4表 2参 2 2     

A model for leveling coalitions among primate males: toward a theory of egalitarianism

We present a simple model of within-group leveling coalitions among male primates. The model assumes that the value of the coalition is the sum of the payoffs of its members, that the individuals payoff is monotonically decreasing with its rank and that coalitions do not cause rank changes. It predicts that mainly mid- to low rankers engage in leveling coalitions, and that most coalition partners are of adjacent ranks. These predictions agree reasonably well with observations in nature. The model also makes the novel predictions that leveling coalitions are found where male mating competition has only a moderate contest component, and that male dominance ranks will become poorly differentiated where leveling coalitions are frequent. Both these predictions are consistent with observations on groups of macaques and baboons. The model also may account for leveling coalitions among egalitarian human foragers, without making additional assumptions about special human capabilities.