Evaluation of the effects, on canopy arthropods, of two agricultural management systems to control pests in olive groves from north-east of Portugal

This study aims to investigate the effect of management regime on canopy arthropod community of the olive tree (Olea europaea L.). Field studies were performed in two successive years, 2002 and 2003, in two olive groves, one under organic farming and the other under integrated protection. The integrated protection grove was sprayed once a year in June, with dimethoate, to control the anthophagous generation of the olive moth, Prays oleae (Bern.). From April to November of each year, the canopy arthropods were sampled weekly. PRC method was used to analyse the effect of management regime at the community level and results showed that taxa responded differently to insecticide application suggesting that the organic grove was a more suitable habitat for the arthropods than the integrated protection grove. Abundance of arthropods peaked in May and June for both years but, after spraying with dimethoate, decreased significantly in integrated protection grove, recovering very slowly thereafter. Psocoptera, Miridae, Formicidae and Coccinellidae were the most sensitive taxa to insecticide application. Their decreasing in abundance was more evident in the second year of the trial. On the other hand chrysopids showed some tolerance to insecticide applications. These results suggest that the timing of spray is of utmost importance in reducing the side effects of spraying on beneficial arthropods. Moreover, differences in population susceptibility as well as in life cycle patterns must be considered.     

Effect of the receding ice-edge on the condition of mid-water fishes in the northwestern Weddell Sea: results from biochemical assays with notes on diet

Electrona antarctica and Bathylagus antarcticus are dominant fishes in the Southern Ocean pelagic ecosystem with disparate life histories, making them excellent subjects for comparative studies. Twenty-one indices of nutritional condition were compared in both species by observing changes in each index as it varied spatially and temporally in association with the marginal ice-zone bloom in the northwestern Weddell Sea. E. antarctica and B. antarcticus exhibited very different patterns of response to the bloom. Nutritional condition increased in 11 of 21 measures in E. antarctica, suggesting that it was in poorer condition at ice-covered stations and in greatly improved condition in post-bloom, open-water stations. The data, combined with a few observations of larvae, indicate that E. antarctica increases feeding before the spring bloom, rapidly building stores of lipid, which are probably used for spawning. In contrast, only three measures of condition were variable in B. antarcticus, and lipid actually decreased from ice-covered to open water. RNA:DNA values increased in open water, coinciding with an increase in food volume present in their guts. These observations, coupled with observations of larvae in ice-covered stations, suggest that B. antarcticus possesses sufficient energetic stores to spawn prior to the bloom, so that larvae are able to fully utilize available resources associated with the spring bloom. Increased somatic growth, as indicated by RNA:DNA, may not begin until later, when the bloom was beginning to decline. Earlier work, which suggested that the deeper living, non-migrating species, like B. antarcticus, would not be affected by the bloom until after shallower, migratory species, like E. antarctica, is supported. Of the assays tested, RNA:DNA appeared to be the most sensitive. The combined assessment of many measures including biochemical, compositional, dietary, and age estimates from single specimens is possible if the samples are treated with sufficient care. The reliance upon a single measure to help interpret the ecology of a species, especially in nekton-sized species, is not as effective as techniques used in combination. Received: 12 January 2000 / Accepted: 16 August 2000     

A rapid method for 90Sr determination in the presence of 137Cs in environmental samples

A rapid method for the determination of 90Sr in the presence of 137Cs using the Cherenkov radiation technique is described. The contribution of 137Cs to gross Cherenkov radiation (90Y + 137Cs) was examined for 137Cs /90Sr ratios ranging from 0.09 to 2.50 for 137Cs activities ranging from 2 to 1,211 Bq. Results from direct Cherenkov radiation measurement and results after radiochemical separation of 90Y from 90Sr for samples containing both 90Sr and 137Cs were compared. Errors below 5% were obtained for 137Cs /90Sr ratios lower than 1, when no separation was performed, independently of the activity level. However, errors between 10% and 35% were obtained for 137Cs/90Sr ratios higher than 1. In order to determine 90Sr activity in the presence of 137Cs using the Cherenkov technique, a multiple linear regression analysis model was established to correct the data for 137Cs content. The mathematical correction proposed was validated using 66 artificially contaminated lettuce samples in a laboratory experiment by taking into account the activity levels of 137Cs and 90Sr and the radionuclide ratios. Comparison of mathematically corrected radionuclide ratios with the results obtained without correction shows that, for radionuclide ratios higher than 1, error values for measuring 90Sr activity using the mathematical model were much smaller than when no radiochemical separation was performed. On the other hand, for ratios lower than 1, error values when measuring 90Sr activity with radiochemical separation were smaller than when mathematical correction was performed. In spite of this, the mathematical correction is an appropriate way of reducing the time needed to determine radiostrontium using the Cherenkov radiation technique. The method proposed could be a powerful tool for environmental research whenever the contents of 90Sr and 137Cs have to be determined.     

Polycyclic aromatic hydrocarbons in mountain soils of the subtropical Atlantic

Surface soil samples from various altitudes on Tenerife Island, ranging from sea level up to 3400 m above mean sea level, were analyzed to study the distribution of 26 polycyclic aromatic hydrocarbons (PAHs) in a remote subtropical area. The stable atmospheric conditions in this island define three vertically stratified layers: marine boundary, trade-wind inversion, and free troposphere. Total PAH concentrations, 1.9 to 6000 microg/kg dry wt., were high when compared with those in tropical areas and in a similar range to those in temperate areas. In the marine boundary layer, fluoranthene (Fla), pyrene (Pyr), benz [a]anthracene (BaA), and chrysene (C + T) were largely dominant. The predominance of Fla over Pyr may reflect photo-oxidative processes during atmospheric transport, although coal combustion inputs cannot be excluded. The PAHs found in higher concentration in the soils from the inversion layer were benzo[b + j]fluoranthene (BbjF) + benzo[k]fluoranthene (BkF) > benzo[e]pyrene (BeP) approximately indeno[1,2, 3-cd]pyrene (Ind) > benzo[a]pyrene (BaP) approximately benzo[ghi]perylene (Bghi) > coronene (Cor) approximately dibenz[a,h]anthracene (Dib), reflecting that high temperatures and insolation prevent the accumulation of PAHs more volatile than BbjF in significant amounts. These climatic conditions involve a process of standardization that prevents the identification of specific PAH sources such as traffic, forest fires, or industrial inputs. Only soils with high total organic carbon (TOC) (e.g., 10-30%) preserve the more volatile compounds such as phenanthrene (Phe), methylphenanthrenes (MPhe), dimethylphenanthrenes (DMPhe), and retene (Ret). However, no relation between PAHs and soil TOC and black carbon (BC) was found. The specific PAH distributions of the free tropospheric region suggest a direct input from pyrolytic processes related to the volcanic emission of gases in Teide.     

Air Quality in Major Portuguese Urban Agglomerations

This paper presents some recent research work that has beendeveloped for the major Portuguese agglomerations. Threemain topics are developed: the methodology used in Portugalto limit agglomerations (as they are defined by theEuropean Air Quality Framework Directive 96/62/EC), thepreliminary assessment of the air quality levels in themost densely populated agglomerations over the last fiveyears and their influence on the air quality levels acrossthe country (a requirement by Directive 96/62/EC), and theuse of an air quality index to raise public awareness aboutair quality levels. It is concluded that particulate matteris the critical pollutant in Portuguese populated urbanareas. In Lisbon and Oporto, based in 1999 data, in allmonitoring stations, the daily average limit value of 50g m^-3 for particulate matter (PM₁₀) isexceeded more times during a year period then allowed byDirective 99/30/EC. In the same areas, nitrogen dioxideconcentrations are above the annual limit value of 40g m^-3 for the protection of human health set byDirective 99/30/EC, and influence pollution concentrationswithin a few tens of kilometres surrounding the urbanareas.     

Respiration and chemical composition of the bathypelagic euphausiid Bentheuphausia amblyops

Bentheuphausia amblyops is a cosmopolitan bathypelagic euphausiid with a vertical range of from 280 to 7 000 m. Determinations of proximate and elemental composition show that B. amblyops has a more robust structure (lower water content and higher protein content) than is typical of other bathypelagic Crustacea. B. amblyops is a strong swimmer and is capable of employing its thoracic legs in raptorial fashion. Discrete depth trawls taken between depths of 400 and 2 500 m on a diel basis show no evidence of vertical migration. There was no significant difference in oxygen consumption within the species environmental temperature range (1.5° to 7.5°C), which may be partially ascribed to a limited temperature effect and partially to variability in spontaneous activity at the different temperatures. Between 7.5° and 9.5°C there was a marked temperature effect on metabolism (Q₁₀=6.4). The observed vertical distribution and metabolic response to elevated temperature preclude the migrations to the surface that have been postulated for B. amblyops. The robust composition of the species, its behavioral characteristics, and published diet information strongly suggest that the species is omnivorous with a strong predatory component in its foraging strategy.     

Propulsion efficiency and cost of transport for copepods: a hydromechanical model of crustacean swimming

In the absence of direct measurement, costs of locomotion to small swimming Crustacea (<10 mm) have been derived exclusively through application of the fluid dynamic theory. Results indicate very low swimming costs, and contradict experimental data on larger Crustacea (15 to 100 mm) that suggest a three-fold increase in metabolic rate with increasing swimming speed. This paper introduces a swimming model that analyzes the hydrodynamic forces acting on a crustacean swimming at non-steady velocity. The model treats separately the hydrodynamic forces acting on the body and the swimming appendages, approximating the simultaneous solution of equations quantifying the drag and added-mass forces on each by stepwise integration. Input to the model is a time-series of instantaneous swimming-appendage velocities. The model output predicts a corresponding time-series of body velocities as well as the mechanical energy required to move the swimming appendages, dissipated kinetic energy, and metabolic cost of swimming. Swimming of the calanoid copepod Pleuromamma xiphias (Calanoida) was analyzed by extrapolating model parameters from data available in the literature. The model predictions agree well with empirical observations reported for larger crustaceans, in that swimming for copepods is relatively costly. The ratio of active to standard metabolism for P. xiphias was >3. Net cost of transport was intermediate to the values found experimentally for fish and larger crustaceans. This was a consequence of the predicted mechanical efficiency (34%) of the copepod's paddle propulsion, and of increased parasitic resistance resulting from non-steady velocity swimming.     

Metabolic cold adaptation in Antarctic fishes: evidence from enzymatic activities of brain

To evaluate the concept of metabolic cold adaptation (MCA) in fishes, we compared - in brain, red muscle, and white muscle of Antarctic notothenioid fishes and tropical/subtropical fishes - the activities of two enzymes of ATP-generating pathways, citrate synthase (CS), an indicator of citric acid cycle activity (aerobic metabolism), and lactate dehydrogenase (LDH), an indicator of potential for ATP production through anaerobic glycolysis. Brain was chosen because, unlike locomotory muscle, its metabolic activity is not likely to be influenced by a species' level of activity or nutritional status, so MCA should be readily observed if present. CS and LDH activities in brain exhibited a high level of MCA, but compensation to temperature was not complete (48% for CS; 46% for LDH). CS and LDH activities in red and white muscle varied widely among species, according to the general level of locomotory activity. The 'mode of life'-related enzymatic activities in locomotory muscle show that study of MCA at the level of whole organism metabolism is fraught with difficulties and experimental ambiguities. In contrast, the low variation among species within each group in enzymatic activities in brain, and the large differences between groups in CS and LDH activity, show that brain is an excellent study system for evaluating metabolic compensation to temperature.     

Oxygen consumption of midwater fishes and crustaceans from the eastern Gulf of Mexico

Oxygen consumption was measured as a function of temperature, oxygen partial-pressure (P_O2)and species depth of occurrence for twenty-three species of midwater fishes and crustaceans collected from the eastern Gulf of Mexico from June 1981 to July 1985. Q₁₀s (7° to 20°C) of 3.90 and 3.24 were recorded for myctophid and non-myctophid fish groups, respectively, while values of 2.22, 2.19, 2.19 and 2.54 were calculated for sergestid, penaeid, carid and euphausiid crustacean groups, respectively. Q₁₀s were consistent for species within each group. All of the species tested regulated their oxygen consumption to P_O2levels normally encountered within the eastern Gulf. Values of critical partial pressure (P_c) ranged from 20 to 40mm Hg and increased slightly with increasing temperature and respiration rate. Declining respiration with increasing minimum depth of occurrence was primarily a function of temperature alone. Changes in size, dry weight and water content contributed only a small fraction to the observed decrease. This finding contrasts with studies from the eastern Pacific Ocean, where temperature is a minor contributor to changes in respiration rate with depth.