Living in an oasis: Rapid transformations,resilience, and resistance in the North Water Area societies and ecosystems

Based on lake sediment data, archaeological findings, and historical records, we describe rapid transformations, resilience and resistance in societies and ecosystems, and their interactions in the past in the North Water area related to changes in climate and historical events. Examples are the formation of the polynya itself and the early arrival of people, ca. 4500 years ago, and later major human immigrations (different societies, cultural encounters, or abandonment) from other regions in the Arctic. While the early immigrations had relatively modest and localised effect on the ecosystem, the later-incoming culture in the early thirteenth century was marked by extensive migrations into and out of the area and abrupt shifts in hunting technologies. This has had long-lasting consequences for the local lake ecosystems. Large natural transformations in the ecosystems have also occurred over relatively short time periods related to changes in the polynya. Finally, we discuss the future perspectives for the North Water area given the many threats, but also opportunities.     

Microphytoplankton in the Strait of Otranto (eastern Mediterranean)

The Strait of Otranto is the connection between the Adriatic and Ionian Seas. Low nutrient concentrations, high transparency, and low phytoplankton cell density and biomass reflect the oligotrophic character of the area. Enrichment of the euphotic layer with nutrients is mainly due to discharge of Albanian and Greek rivers, as well as mixing and upwelling in winter/early spring. Following phytoplankton bloom in April, a progressive decrease of phytoplankton cell density is due to the consumption of nutrients throughout the proceeding summer and autumn. Nitrogen was a strong limiting factor for phytoplankton growth in summer. Deep biomass maxima were detected in the 50 to 100 m layer and corresponded mostly to cells smaller than 20 m. The eastern part of the strait is mostly influenced by the northerly inflowing current from the Ionian Sea, and the western part by the southerly outflowing current from the Adriatic Sea. This typical circulation could be disturbed by inertial oscillations in the current field, generated by the strong oscillating winds and cyclonic eddies. The type of circulation determined the distribution of thermohaline characteristics, abundance, biomass, as well as taxonomic composition of phytoplankton, across the strait. Ecological characteristics of the water masses on two sides of the strait were significantly different during the formation of a longitudinal thermohaline front in May 1990.     

Residency and depth movements of a coastal group of Atlantic cod (Gadus morhua L.)

Atlantic cod stocks are subdivided into geographically and biologically discrete populations; some being locally resident, others migratory. The reasons for the variation in migration pattern and the consequences it may have for population structuring is poorly understood. We studied a group of cod from the coastal waters of the Shetland Isles in the northern North Sea. During the spawning season, electronic tags that record depth and temperature over time were implanted into 133 individuals and the fish released within a few kilometres of where they were captured. Thirty-nine cod have been recaptured up to 608 days later, throughout the year and, in all but two cases, within 15 km of their release site. Geolocation methods based on temperature and bathymetry also suggested that the cod had a limited home range, remaining resident year-round in coastal waters. The cod were deeper during the winter and moved to shallower water in late spring and summer. They showed diel, fortnightly and monthly cycles in depth movement that varied much within and between individuals over the season. Residency and the individual variability in vertical movement may reflect a combination of locally complex depth strata, variable seabed substrate and the wide range of seasonally available prey resources.     

Chemistry of the postpharyngeal gland secretion and its implication for the phylogeny of IberianCataglyphis species (Hymenoptera: Formicidae)

Summary A comparative morphological and chemical study of six endemic species ofCataglyphis from the Iberian Peninsula:C. ibericus, C. rosenhaueri, C. hispanicus, C. humeya, C. velox andC. floricola and the Moroccan speciesC. bombycinus is described. The morphological study relied primarily on genitalia characteristics, whereas the chemical study concentrated on the postpharyngeal gland constituents. Cladograms based on the morphological and chemical data were performed using Ward's method. The dendrogram based on morphological features revealed that the IberianCataglyphis can be classified into three species groupsalbicans, altisquamis andemmae. The same pattern occurred when the dimethylalkanes constituents of the postpharyngeal gland were utilised as character states, with a slight displacement of species within thealtisquamis group. However, when the complete hydrocarbon blend was utilised major discrepancies in the dendrograms occurred.Cataglyphis velox proved to be very similar toC. bombycinus, whereasC. floricola clustered with the other two species of thealtisquamis group. Based on the geographical distribution and paleontological data (Tinaut 1993) it is assumed thatC. floricola recently invaded the Iberian Peninsula. Based on the chemical findings we postulate that chemical character displacement occurred inC. floricola as a result of its sympatry withC. velox after the former colonized the Iberian Peninsula. We further discuss the possible reason for the different dendrograms obtained when only the dimethylalkanes are considered and its implication for the communicative role of the postpharyngeal gland secretion in these ants.     

What describes fecundity of Capitella sp. 1 better: macro- or micronutrient availability?

During a preliminary set of experiments (April 1987). I measured short-term (20 d) reproductive responses of laboratory-cultured Capitella sp. 1 at 20°C, at four daily ration levels (0.26 to 2.60 mg of organic nitrogen per bowl), and for four food types: Gerber's mixed cereals, Ulva sp., diatoms, and Tetramen fish food. Average female body size, number of fertile segments, and fecundity were significantly affected both by food type and food ration. Average fecundities ranged from 21 (Gerber, 0.26 mg N d^-1) to 448.3 eggs per female (Tetramen, 2.60 mg N d^-1). During a second set of experiments (May 1987), I measured the reproductive response of laboratory-cultured Capitella sp. 1 at 20°C at six ration levels of spring and summer sediment-trap material collected in the Patuxent Estuary, Maryland, USA. Worms raised on these two diets failed to reproduce during the period of this experiment. I used simple and miltiple linear-regression models to describe relationships between fecundity and daily rations and macro- (dry wt, C, N) and micronutrients (essential amino- and essential fatty acids). These models were carried out on three data sets corresponding to either 4 or 6 food types. The results suggest that different nutritional factors may be limiting for different foods. However micronutrients and especially essential amino acids probably more aptly describe nutritional limitation of reproduction in Capitella sp. 1.     

Swim speeds of free-ranging great cormorants

Information about foraging speeds is particularly valuable when the impact of a predator species upon a community of prey has to be defined, as in the case of great cormorants. We measured the swim speed of 12 (six males and six females) free-ranging great cormorants Phalacrocorax carbo, foraging off the Greenland coast during the summer of 2003, using miniaturized data-loggers. Although mean body mass of males was 27% greater than that of females, and mean swim speed of males were 29–57% higher than that of females during foraging phases (but not descent phases) of dives, these differences in speeds were not significant due to high variances. Birds descended to the mean maximum depth of 4.7 m at an average speed of 1.6±0.5 m s⁻¹, a speed similar to that measured in captive cormorants in previous studies. Although bursts of up to 4 m s⁻¹ were recorded, speed usually decreased during the deepest (foraging) phase of dives, being on average 0.8±0.6 m s⁻¹. Speeds measured here should be taken with caution, because the large propeller loggers used to measure speed directly decreased descent speeds by up to 0.5 m s⁻¹ when compared to smaller depth-only loggers. Cormorants in Greenland seem to combine two searching strategies, one requiring low speed to scan the water column or benthos, and one requiring high speed to pursue prey. These two strategies depend on the two main habitats of their prey: pelagic or demersal.     

Propagation of olfactory information within the honeybee hive

Transfer of information about food source characteristics within insect societies is essential to colony-foraging success. The food odor communicated within honeybee hives has been shown to be important for food source exploitation. When successful foragers return to the nest and transfer the collected nectar to hive mates through mouth-to-mouth contacts (trophallaxis), potential recruits receiving these samples learn the food odor by associative learning. The food then becomes rapidly distributed among colony members, which is mainly a consequence of the numerous trophallaxes between hive-mates of all ages during food processing. We tested whether the distribution of food among hive mates causes a propagation of olfactory information within the hive. Using the proboscis extension response paradigm, we show that large proportions of bees of the age groups representing the main worker castes, 4 to 9-day-old bees (nurse-aged bees), 12 to 16-day-old bees (food processor-aged bees), and actual foragers (about 17+ day old bees) associatively learn the food odor in the course of processing food that has been collected by only a few foragers. Results further suggest that the information is shared more or less equally between bees of the three age groups. This shows that olfactory information about the flower species exploited by foragers is distributed within the entire colony and is acquired by bees of all age groups, which may influence many behaviors inside and outside the hive.     

Neocembrene A, a major component of the trail-following pheromone in the genus Prorhinotermes (Insecta, Isoptera, Rhinotermitidae)

Summary. The diterpene neocembrene A or (1E,5E,9E,12R)-1,5,9-trimethyl-12-(1-methylethenyl)-1,5,9-cyclotetradecatriene, known as the trail-following pheromone of the advanced Termitidae Nasutitermitinae Nasutitermes exitiosus and Trinervitermes bettonianus, has been identified after SPME-GC/MS as the major component of the trail-following pheromone of the Rhinotermitidae Prorhinotermitinae, Prorhinotermes canalifrons and P. simplex. In all the other Rhinotermitidae studied until now, the major component of their trail pheromones is dodecatrienol ((3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol). This biochemical data further add to the anatomical and molecular characteristics that give a special status to the taxon Prorhinotermes among Rhinotermitidae. In Prorhinotermes canalifrons and P. simplex, neocembrene A was the only secretory compound specific to the sternal gland surface that could be detected after SPME. It elicited orientation as well as recruitment behavioral effects. However, the comparison of the respective biological activities triggered by neocembrene A and by sternal gland secretion suggests that minor components of the latter are acting in synergy with neocembrene A.     

加拿大北方森林过去、当前和未来的火灾频率:对于森林可持续经营的意义

在过去的几十年里,对基于对历史上自然干预动力的理解的森林经营方法的开发兴趣日益增加.这一方法的理由是,有利于景观组成和林分结构及自然生态系统的经营活动也应当保持生物多样性和基本的生态功能.在火灾居支配地位的景观,用森林经营替代火灾这一方法只在当前火频率和未来火频率比工业化以前的火频率低得多的情况下才有可能.通过将当前火频率、未来火频率与在加拿大北方森林中再现的森林火灾历史的比较,我们讨论了这一问题.对于多块研究地而言,当前火频率和2倍CO.及3倍CO2情形下模拟的未来火频率都低于过去火频率,这暗示着森林经营可以被用于重建受控于火灾的、工业化以前景观的林木年龄结构.但对目前的同龄林经营来说,还有一些重要的限制因子.     

Trace gas emissions from German agriculture as obtained from the application of simpler or default methodologies

For the assessment of emission inventories matching pairs of activities (emission explaining variables) and emission factors are used. Simpler and detailed methodologies are proposed within the emission inventory handbooks. The data sets needed to serve the detailed methodologies have not been at public disposal so far. Therefore, this paper investigates the applicability of simpler methodologies to the statistical data sets of activities officially available in Germany. The statistical data base for the assessment of emissions from fertilised soils is adequate if one assumes that fertilisers sold in one financial year are applied in the same year. For grassland, statistical data describing the actual management do not exist. Lack of nitrogen inputs with crop residues and due to nitrogen fixation make it impossible to deduce the respective emissions. The assessment of indirect emissions due to reactions of leached nitrogen is also impossible. For extensively managed grasslands, data concerning fertiliser application or grazing are missing when calculating emissions. The determination of emissions from organic soils presupposes the knowledge of both the area concerned and the degree of mineralisation which has been attained at the time of the inventory. The results of the biennial animal census meet the requirements of the simpler methodologies. However, the assumptions made to evaluate the mean emission factors are not correct in many cases, as far as animal performance, housing, storage and application of animal excreta are concerned. The simpler methodologies are biassed, as the emission factors are (Northwest) European means. Changes in the raising of statistical data make the construction of meaningful time-series difficult.