PSM in Böden:

The fate of pesticides in soil is incompletely described by the analytical determination of applied pesticides because a differentiation between the processes degradation and sorption which determine pesticide concentration in soils is not possible. By analyzing corresponding metabolites, degradation can be confirmed. Detailed mass balances considering the mineralization and formation of non-extractable residues are set up in closed model systems applying radiotracer techniques. This complex laboratory data can only be transferred to field conditions by mathematical modeling.     

Mass transfer limitation of photosynthesis of coral reef algal turfs

Algal turfs are the major primary producing component on many coral reefs and this production supports higher levels in the complex reef trophic web. Rates of metabolism of algal turfs are related positively to water motion, consistent with limitation by the diffusion of a substance through a boundary layer. Based on engineering mass transfer theory, we hypothesized that photosynthesis of algal turfs is controlled by rates of mass transfer and responses of photosynthesis to increasing flow speed should be predicted by engineering correlations. This hypothesis was tested in ten experiments where photosynthesis was estimated in a flume/respirometer from changes in dissolved oxygen at eight flow speeds between 0.08 and 0.52 m/s. Flow in the flume and over the reef at Kaneohe Bay, Oahu, Hawaii was estimated using hot-film thermistor and electromagnetic current meters. Rates of photosynthesis were related positively to flow in all experiments and plots of the log of the average Sherwood number (Sh _meas) versus log Reynolds number (Re _D) for each experiment are lower than predicted for mass transfer through a turbulent boundary layer. Algal turf-covered plates are characterized as hydrodynamically transitional to fully rough surfaces and the lower than predicted slopes suggest that roughness reduces rates of mass transfer. A negative correlation between algal turf biomass and slopes of the log Sh _meas−log Re _D plots suggests that mass transfer to algal turfs is affected significantly by the physical structure of the algal community. Patterns of photosynthesis based on changes in dissolved oxygen and dissolved inorganic carbon concentrations (DIC) indicate that the flow speed effect is not the result of increased flux of oxygen from the algal turfs, and combined with the short response time to flow speed, suggest that DIC may limit rates of photosynthesis. Although there are differences between flow in the flume and flow over algal turfs on the reef, these results suggest that photosynthesis is controlled, at least in part, by mass transfer. The chemical engineering approach provides a framework to pose further testable hypotheses about how algal canopy height, flow oscillation, turbulence, and substratum roughness may modulate rates of metabolism of coral reef algal turfs.     

Physiological stress responses in the edible crab, <Emphasis Type="Italic">Cancer pagurus</Emphasis>, to the fishery practice of de-clawing

We examined physiological stress responses in the edible crab, Cancer pagurus, subjected to the commercial fishery practice of manual de-clawing. We measured haemolymph glucose and lactate, plus muscular glycogen and glycogen mobilisation, in three experiments where the crabs had one claw removed. In the first, crabs showed physiological stress responses when ‘de-clawed’ as compared to ‘handled only’ over the short term of 1–10 min. In the second, de-clawing and the presence of a conspecific both increased the physiological stress responses over the longer term of 24 h. In the third, de-clawing was shown to be more stressful than ‘induced autotomy’ of claws. Further, the former practice caused larger wounds to the body and significantly higher mortality than the latter. Since the fishery practice is to remove both claws, the stress response observed and mortality data reported are conservative.     

A Numerical and Field Investigation of Surface Heat Fluxes from Small Wind-Sheltered Waterbodies in Semi-Arid Western Australia

Shelterbelts are used for a variety of purposes in agricultural environments, primarily because of their ability to improve the downwind microclimate. Excessive evaporative losses from small, agricultural water supply reservoirs in semi-arid Western Australia motivated a combined numerical modelling and field investigation into the potential for using shelterbelts to reduce evaporation from these open waterbodies. A numerical model of the disturbed momentum and turbulence fields in the region modified by the wind-shelter was employed and accounted for the presence of a waterbody downwind. The model was coupled with conservation equations for heat and moisture and sensible and latent heat fluxes were estimated from the simulated momentum, temperature and humidity fields. The numerical simulations were tested against four days of field data from two experiments conducted in the agricultural districts of southwest Western Australia that measured boundary-layer evolution over a variety of small waterbodies protected by artifical and natural wind-shelters. The model provided good predictions of windspeed during neutral conditions, but inadequate specification of the upwind boundary during non-neutral stabilities resulted in the model failing to capture any sensitivity to atmospheric stability as seen in the field data. Despite this limitation, the temperature and humidity fields were adequately captured by the model, and evaporative mass flux predictions also agreed well with estimates taken from water-balance measurements. It is concluded that well-designed wind-shelters can reduce evaporation from open waterbodies by 20–30% as a result of reductions in the velocity scales responsible for removing moisture from the water surface. The model can be used to estimate the values of various shelterbelt design parameters (e.g., porosity, height) that could be applied in the field to provide optimum evaporation reductions.     

Do Tidal-Channel Turbulence Measurements Support k−5/3?

We seriously challenge the belief that tidal-channel data of Grant et al. support the theory for the classical energy-spectrum behavior, k ^–5/3 in the inertial subrange [where k is wave number and (k) is the one-dimensional energy-spectrum function]. The behavior revealed by our re-examination is explained in terms of a more recent theory.     

Baboon loud calls advertise male quality: acoustic features and their relation to rank,age, and exhaustion

Free-ranging adult male baboons give loud two-syllable wahoo calls during dawn choruses, interactions between groups, when chasing females, and in aggressive interactions with other males. Previous research has shown that the rate and duration of these contest wahoos are correlated with a males competitive ability: high-ranking males call more often, call at faster rates, and call for longer bouts than do low-ranking males. Here we report that acoustic features of wahoos also reveal information about male competitive ability. High-ranking males give wahoos with higher fundamental frequencies (F0) and longer hoo syllables. Within-subject analyses revealed that, as males fall in rank, the hoo syllables tend to shorten within a period of months. As males age and continue to fall in rank, F0 declines, hoo syllables shorten, and formant dispersion decreases. Independent of age and rank, within bouts of calling F0 declines and hoo syllables become shorter. Because wahoos are often given while males are running or leaping through trees, variation in these acoustic features may function as an indicator of a males stamina. The acoustic features of contest wahoos thus potentially allow listeners to assess a males competitive ability.Communicated by C. Nunn     

Multimodal signals,imperfect information,and identification of sex in red-backed salamanders (<Emphasis Type="Italic">Plethodon cinereus</Emphasis>)

Theoretical treatments and empirical studies both suggest that signals that occur in multiple sensory modes have superior detectabilities, discriminabilities, and memorabilities. There is also an intuitive link between signal detectability, discriminability, and memorability and the quality of information that is transferred via the signaler. We investigated the role of information quality and sensory modality in the sexual identification of intruding conspecifics by territorial male red-backed salamanders (Plethodon cinereus). Our results imply that these salamanders are able to discriminate between intruding male and female conspecifics (based on the allocation of aggression) in bimodal scenarios (vision and olfaction) even under situations in which the information available about the intruders sexual identities is reduced in quality. In unimodal scenarios (olfaction only), male residents exhibited heightened levels of aggression toward male secretions and reduced levels of aggression toward female secretions. In unimodal scenarios where information pertaining to the sex of the stimulus was reduced in quality, male residents displayed intermediate levels of aggression relative to the responses that male and female stimuli received respectively. Although resident males touched bimodal stimuli significantly more than they touched unimodal stimuli, we were unable to find support for the notion that sensory modality greatly influences how male resident red-backed salamanders allocate aggression toward intruding male versus female stimuli.Communicated by H. Kokko     

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.     

Feeding aggregations of sea stars (<Emphasis Type="Italic">Asterias</Emphasis> spp. and <Emphasis Type="Italic">Henricia sanguinolenta</Emphasis>) associated with sea urchin (<Emphasis Type="Italic">Strongylocentrotus droebachiensis</Emphasis>) grazing fronts in Nova Scotia

Migrating feeding aggregations (or fronts) of sea urchins can dramatically alter subtidal seascapes by destructively grazing macrophytes. While direct effects of urchin fronts on macrophytes (particularly kelps) are well documented, indirect effects on associated fauna are largely unknown. Secondary aggregations of predators and scavengers form around fronts of Strongylocentrotus droebachiensis in Nova Scotia. We recorded mean densities of the sea stars Asterias spp. (mainly A. rubens) and Henricia sanguinolenta of up to 11.6 and 1.7 individuals 0.25 m⁻² along an urchin front over 1 year. For Asterias, mean density at the front was 7 and 15 times greater than in the kelp bed and adjacent barrens, respectively. There was strong concordance between locations of peak density of urchins and sea stars (Asterias r = 0.98; H. sanguinolenta r = 0.97) along transects across the kelp–barrens interface, indicating that sea star aggregations migrated along with the urchin front at rates of up to 2.5 m per month. Size–frequency distributions suggest that Asterias at the front were drawn from both the barrens (smaller individuals) and the kelp bed (larger individuals). These sea stars fed intensively on mussels on kelp holdfasts and in adjacent patches. Urchin grazing may precipitate aggregations of sea stars and other predators or scavengers by incidentally consuming or damaging mussels and other small invertebrates, and thereby releasing a strong odor cue. Consumption of protective holdfasts and turf algae by urchins could facilitate feeding by these consumers, which may obtain a substantial energy subsidy during destructive grazing events.     

Seasonal variation in movement,aggregation and destructive grazing of the green sea urchin (<Emphasis Type="Italic">Strongylocentrotus droebachiensis</Emphasis>) in relation to wave action and sea temperature

Hydrodynamic forces are an important determinant of subtidal community structure, particularly when they limit the distribution and foraging ability of mobile consumers. We examined the effect of wave action on the rate of movement and destructive grazing of a kelp bed by the green sea urchin (Strongylocentrotus droebachiensis) under field conditions. We measured density and rate of advance at fixed intervals along ∼100 m of a grazing front over 1 year, and quantified individual movement rates in the barrens 5–10 m behind the urchin front using a time-lapse videography. Seasonal variation in the mean rate of advance of the front (range: 0–4 m month⁻¹) was explained by changes in urchin density at the front (120–360 individuals m⁻²), which in turn varied inversely with significant wave height (0.5–2 m). Water temperature (0.8–17.6°C) had no effect on the rate of advance or on urchin density (aggregation) at the front, except when temperature exceeded 17°C. Movement of individual urchins also was affected by wave action: we observed a significant decrease in speed and displacement of urchins with increasing significant wave height. Wave action had no effect on the proportion of urchins moving or the degree of linearity of their movements. We propose that the decrease in urchin density at the front associated with increased wave action, results from de-aggregation, which reduces the risk of dislodgement, combined with a reduction in urchin movement in barrens, which supplies new urchins to the front.