Early Summer Period Research Articles

BURROWING AND CRAWLING BEHAVIOUR OF THREE SPECIES OF UNIONIDAE IN FINLAND

The aim of this study was to examine the burrowing and crawling behaviour of three unionid clam species in the field. Of the four study lakes in southern Finland, Anodonta piscinalis occurred in all, Pseudanodonta complanata in three and Unio pictorum in only one. In all three species, there was a positive correlation between the height of the above-sediment part of the shell and the burrowing angle (deviation from the horizontal position). When surfacing, the position of the clam became more vertical. Anodonta piscinalis was more visible in June than in August in one population, while in other populations monthly differences were not found. The result suggests that A. piscinalis may be more visible during its spawning period in early summer (June) than in late summer. This behaviour could have a reproductive function, ensuring external fertilization. Monthly differences in crawling activity of A. piscinalis were also found in one population: in Lake Alvajarvi, A. piscinalis crawled more in August than in June. No monthly differences in the burrowing or crawling of P. complanatawere found. In Unio pictorum, no differences were observed in crawling, but the clams were more visible in August than in June. When compared with P. complanata, A. piscinalis and U. pictorum were more visible and in a more vertical position. In A. piscinalis, the bigger individuals were more visible than the smaller individuals, but this was not the case in P. complanata and U. pictorum.

Relative growth rate of leaf biomass and leaf nitrogen content in several mediterranean woody species

In many plant species, herbivory is a major determinant of leaf mortality and it can cause a strong reduction in productive potential. Most predation occurs on young, expanding leaves. Thus, a rapid growth of the leaves can reduce the impact of predation. Furthermore, in cold Mediterranean climates the length of the growing season is constrained to a short period in spring and early summer owing both to low winter temperatures and drought stress in early summer. Therefore, a rapid deployment of leaf area and a high photosynthetic capacity during the spring and early summer might have important positive effects on the final carbon balance of the leaf population. Relative growth rates (RGR) of leaf biomass were measured in 19 woody species typical of Central Western Spain with deciduous and evergreen habits. Highly significant differences were detected in the leaf growth rate of the different species. The differences between species, however, did not correlate either with the mean leaf life-span of each of the species or with other leaf traits such as photosynthetic capacity, specific leaf area or nitrogen content. Leaf growth rate was positively correlated with time elapsed between leaf initiation and fruit maturation, so that species with fruit dispersal in spring and early summer in general had lower leaf growth rates than species with autumn fruit shedding. This relationship shows the effects of the concurrence between vegetative and reproductive organs for nutrients and other resources. Nitrogen concentration in the leaves was very high at the time of bud break, and declined during leaf expansion owing to the dilution associated with the increase in structural components. The rate of nitrogen dilution was, thus, positively related to the leaf growth rate. Relative growth rates calculated for nitrogen mass in leaves were very low compared to the growth in total mass. This suggests that most leaf nitrogen is translocated from the plant stores to the leaf biomass before the start of leaf expansion and that the contribution of root uptake during leaf expansion is comparatively low.

Listeria monocytogenes Contamination Patterns for the Smoked Fish Processing Environment and for Raw Fish

Reliable data on the sources of Listeria monocytogenes contamination in cold-smoked fish processing are crucial in designing effective intervention strategies. Environmental samples (n = 512) and raw fish samples (n = 315) from two smoked fish processing facilities were screened for L. monocytogenes, and all isolates were subtyped by automated ribotyping to examine the relationship between L. monocytogenes contamination from raw materials and that from environmental sites. Samples were collected over two 8-week periods in early spring and summer. The five types of raw fish tested included lake whitefish, sablefish, farm-raised Norwegian salmon, farm-raised Chilean salmon, and feral (wild-caught) salmon from the U.S. West Coast. One hundred fifteen environmental samples and 46 raw fish samples tested positive for L. monocytogenes. Prevalence values for environmental samples varied significantly (P < 0.0001) between the two plants; plant A had a prevalence value of 43.8% (112 of 256 samples), and plant B had a value of 1.2% (3 of 256 samples). For plant A, 62.5% of drain samples tested positive for L. monocytogenes, compared with 32.3% of samples collected from other environmental sites and 3.1% of samples collected from food contact surfaces. Ribotyping identified 11 subtypes present in the plant environments. Multiple subtypes, including four subtypes not found on any raw fish, were found to persist in plant A throughout the study. Contamination prevalence values for raw fish varied from 3.6% (sablefish) to 29.5% (U.S. West Coast salmon), with an average overall prevalence of 14.6%. Sixteen separate L. monocytogenes subtypes were present on raw fish, including nine that were not found in the plant environment. Our results indicate a disparity between the subtypes found on raw fish and those found in the processing environment. We thus conclude that environmental contamination is largely separate from that of incoming raw materials and includes strains persisting, possibly for years, within the plant. Operational and sanitation procedures appear to have a significant impact on environmental contamination, with both plants having similar prevalence values for raw materials but disparate contamination prevalence values for the environmental sites. We also conclude that regular L. monocytogenes testing of drains, combined with molecular subtyping of the isolates obtained, allows for efficient monitoring of persistent L. monocytogenes contamination in a processing plant.

North Atlantic Oscillation synchronizes food-web interactions in central European lakes.

A regular and distinct feature of seasonal plankton succession in temperate lakes is the early summer period of algal suppression by herbivores, i.e. the clear water phase. Within the last 30 years the timing of this food-web interaction between algae and herbivores has advanced on average by approximately two weeks in central European lakes due to faster population growth of herbivores in warmer water. Trend and inter-annual variability in clear water timing were strongly related to the climate dynamics of the North Atlantic, i.e. the North Atlantic Oscillation (NAO). Due to its large-scale effects, the NAO synchronized plankton succession in central European lakes, causing a striking temporal coherence of a food-web interaction over several hundreds of kilometers.

Intra-annual tree-ring parameters indicating differences in drought stress of Pinus sylvestris forests within the Erico-Pinion in the Valais (Switzerland)

The effects of drought on radial growth of Pinussylvestris were investigated by comparing sites along hydricgradients. The gradients were located in Valais, an inner Alpine dry valley inSwitzerland, with each consisting of two site types, an extreme dry, xeric siteand a less dry, moderate site. The two site types were assigned tophytosociological associations within the Erico-Pinion. The investigationcovered the responses of tree growth to climate and particularly concentratedonintra-annual features of tree-rings such as earlywood/latewood ratio,intra-annual density fluctuations (IADFs) and traumatic tissues (TTs) as wellasthe sapwood/heartwood ratio. Radial growth differed according to the sitetypes,with trees on dry sites generally showing more missing rings, lower mean ringwidths, lower autocorrelation, higher mean sensitivities, reduced latewoodproportions and lower sapwood areas than trees on moderate sites. Therelationships between climate and tree-ring width, studied using responsefunction analysis, varied strongly between the site types within theErico-Pinion: Tree growth on dry sites was positively influenced byprecipitation at the end of the winter and the beginning of the growing seasonand negatively influenced by temperature in June. Winter precipitation waspositively correlated with radial growth, demonstrating its importance for thesuccessful root and shoot growth of the plants in spring on dry sites. Onmoderate sites, tree growth was less controlled by climate than by priorgrowth.The intra-annual density fluctuations (IADFs) provided a valuable means todifferentiate between the site types. In comparison to the moderate sites, thetrees on dry sites contained more IADFs, and their frequency was increased.Moist-cool conditions in the middle of the growing season were the triggeringfactor for IADFs on dry sites, whereas on moderate sites, there must be anadditional warm period in early summer in order to initiate IADFs. Most IADFswere found in latewood. We found no relationship between climate and traumatictissues (TTs). It is unclear whether other abiotic or biotic factors such aswounding by insects or birds are responsible for the development of TTs. Theassignment of these differences in tree growth behaviour to phytosociologicalassociations will enable a deeper understanding of the site types and willfacilitate the comparison with similar studies. Furthermore, the results can becombined with studies from other scientific disciplines concerning thesephytosociological associations. The ecological indicator values of thevegetation was a precise method for the distinction of site types.

Spatial and temporal variations in copepod community structure in the lower St. Lawrence Estuary, Canada

The lower St. Lawrence estuary (LSLE) is a narrow and deep basin under the influence of both estuarine and marine processes. As a result, the LSLE is characterized by strong spatiotemporal heterogeneity in biological and physical environmental conditions. Previous studies have indicated a bias in the summer composition of the copepod population for predominance of late-development stages of Calanus spp., in comparison with adjacent waters of the Gulf of St. Lawrence (GSL) and northwest Atlantic. In this study, we use a 22 mo spatial survey of the LSLE to determine spatial and temporal variations in the copepod community and the relative contribution of Calanus spp. (C. finmarchicus and C. hyperboreus). Multivariate analysis revealed 4 copepod assemblages associated with seasonal patterns in temperature and chlorophyll a. Calanus spp. dominated the early summer community whereas the seasonal increase in abundance of the more surface-dwelling species (Acartia spp., Oithona spp. and Pseudocalanus spp.) explained the mixed Calanus spp./surface species community observed in late summer-autumn and winter. Three recurrent geographic zones can be discriminated in the LSLE on the basis of specific composition and abundance. The copepod community in the upper-central Laurentian Channel was dominated by Calanus spp. Downstream, in late summer-autumn and winter, a mixed Calanus/surface species assemblage was observed. In the shallow region, a very low abundance of Calanus spp. resulted in dominance of surface species after the early summer period. The genus Calanus spp. was the dominant component of the copepod community in LSLE as a whole because of its consistently high abundance along the Laurentian Channel during different seasons. A change in environmental conditions in the 1990s associated with a decadal climate variation in the GSL-LSLE region appears to be related to a dramatic increase in abundance of midwater copepod species (mainly Metridia longa) and, subsequent decline in the relative abundance of Calanus spp. We develop the hypothesis that the observed patterns in copepod species composition in the LSLE are primarily a consequence of the combined effect of the export in the residual surface outflow of early life stages of Calanus spp. and small surface-dwelling species and the upstream advection of late-development stages of Calanus spp. and midwater species in the inflowing deep water of the Laurentian Channel.

Assessment of the potential of willow SRC plants for energy production in areas contaminated by radionuclide deposits: methodology and perspectives

The objective of this paper is to assess the suitability of willow short rotation coppice (SRC) as land use alternative for farmland contaminated by radiocaesium ( 137 Cs ) fallout from the Chernobyl nuclear power plant disaster. The Polessie district, a typical rural area located close to Chernobyl, was chosen as reference for the development of a GIS-based multidisciplinary approach combining maps of soil resources and 137 Cs deposits, modelling of SRC biomass production and estimations of 137 Cs soil-to-wood transfer. From an agronomic viewpoint, the very dry sandy podzolic soils in the reference area are not suitable for SRC growing because they cannot supply adequate water for SRC during the early summer period. Moreover, on the other soil types, both careful weeding and water supply during the early months after plantation are required, until both leaf cover and root system are sufficiently developed. From the radio-ecological viewpoint, and according to the local legislation, the SRC biomass produced on loamy sand, sandy loam and loamy soils is suitable for firewood. SRC biomass from the highly productive peaty soils (39.4% of the land area of Polessie) may also be used but only if its conversion into heat or electricity is carefully managed. From an economic viewpoint, due to the very low local prices for fossil fuels, the gasification of SRC wood is at present not economically competitive with fossil fuels in Ukraine. Only strong political will and incentives could favour the implementation of bioenergy routes through subsidies and a major reorganisation of the energy market.

Organic matter distributions in the Eastern North Atlantic–Azores Front region

Temperate, transitional and subtropical waters of the remote Azores Front region east of Azores (24–40°N, 22–32°W) were sampled during three cruises conducted under increasing stratification conditions (April 1999, May 1997 and August 1998). Despite the temporal increase of surface temperature (by 5 °C) and stratification (by 2.1 min −2), as well as the thermocline shoaling (by ∼15 m), dissolved organic carbon (DOC) and nitrogen (DON) in the surface layer were not significantly different for the early spring, late spring and summer periods, with average concentrations of 69±2 μM-C and 5.2±0.4 μM-N, respectively. The surface excess of semi-labile DOC, compared with the baseline DOC concentration in the deep ocean (47±2 μM-C), represents 33% of the bulk DOC concentration and as much as 85% of the TOC (=POC+DOC) excess. When compared with the winter baseline (56±2 μM-C), the seasonal surface DOC excess is 20% of the bulk DOC concentration and 87% of the seasonal TOC excess. These results confirm the major role played by DOC in the carbon cycle of surface waters of the Azores Front region. The total amount of bioreactive DOC transported from the temperate to the subtropical North Atlantic by the Ekman flux between March and December represents only ∼15% of the average annual primary production, and ∼15% and ∼30% of the measured sinking POC flux+vertical DOC eddy diffusion during early spring and summer, respectively. Vertical eddy diffusion is 35% and 2% of the spring and summer sinking POC flux, respectively. On the other hand, DOC only contributes 13% to the local oxidation of organic matter in subsurface waters (between the pycnocline and 500 m) of the study region.

Cloud water contents and hydrometeor sizes during the FIRE Arctic Clouds Experiment

During the year‐long Surface Heat Budget of the Arctic Experiment (1997–1998) the NOAA Environmental Technology Laboratory operated a 35‐GHz cloud radar and the DOE Atmospheric Radiation Measurement Program operated a suite of radiometers at an ice station frozen into the drifting ice pack of the Arctic Ocean. The NASA/FIRE Arctic Clouds Experiment took place during April‐July 1998, with the primary goal of investigating cloud microphysical, geometrical, and radiative properties with aircraft and surface‐based measurements. In this paper, retrieval techniques are utilized which combine the radar and radiometer measurements to compute height‐dependent water contents and hydrometeor sizes for all‐ice and all‐liquid clouds. For the spring and early summer period, all‐ice cloud retrievals showed a mean particle diameter of about 60 μm and ice water contents up to 0.1 g/m3, with the maximum sizes and water contents at approximately one fifth of the cloud depth from the cloud base. The all‐liquid cloud retrievals had a mean effective particle radius of 7.4 μm, liquid water contents up to 0.7 g/m3, and a mean droplet concentration of 54 cm−3. Maximum retrieved liquid drop sizes, water contents, and concentrations occurred at three fifths of the cloud depth from the cloud base. As a measure of how representative the FIRE‐ACE aircraft flight days were of the April‐July months in general, retrieval statistics for flight‐day clouds are compared to the mean retrieval statistics. From the retrieval perspective the ice particle sizes and water contents on flight days were ∼30% larger than the mean retrieved values for the April‐July months. Retrieved liquid cloud parameters during flight days were all about 20% smaller. All‐ice and/or all‐liquid clouds acceptable for these retrieval techniques were observed about 34% of the time clouds were present; at all other times, mixed‐phase clouds precluded the use of these single‐phase retrieval techniques.

Bromine oxide—ozone interaction over the Dead Sea

Atmospheric measurements were performed during a 1 month period in early summer of 1997 at the Dead Sea in Israel in an attempt to identify bromine monoxide BrO, and evaluate its effect on ozone chemistry. The differential optical absorption spectroscopy (DOAS) technique was utilized to identify and measure BrO present in the air masses. Concurrent to the DOAS measurements, continuous monitoring of SO2, NO/NOx, O3, and CO was performed. Filter samples for aerosol analysis and whole air canister samples for bromocarbon analysis were also collected. The present paper reports the complete comprehensive data set of the measurements at the Dead Sea site and is a continuation to our preliminary communication [Heberstreit et al., 1999]. The more complete data now available enable a more detailed examination of the sources and mechanisms of the reactive halogen species and the presentation of new conclusions. The results showed a diurnal repeating cycle of O3 and BrO variations, correlated with solar radiation and wind direction. During the elevated BrO events, where bromine oxide rose to daily maximum values often exceeding 100 ppt, a clear negative correlation with O3 was observed. During these episodes, the O3 regularly decreased from noontime levels of 50–80 ppb or higher down to 10–30 ppb and occasionally to levels below the detection limit of 2 ppb. The enhanced BrO levels were associated with southerly winds that are typical for the location during midday hours. This suggests that a possible source for the reactive bromine species is the interaction of atmospheric oxidants with bromide at the surface of the large salt pans located at the southern end of the Dead Sea. Research flights flown over the area showed that ozone destruction to levels well below the background values were observed over large areas of the Dead Sea Valley.

Phytoplankton biomass in the sub-Antarctic area of the Straits of Magellan (53°S), Chile during spring-summer 1997/1998

In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S), surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer). Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September: <0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.

Seasonal patterns of photosynthetic response and acclimation to elevated carbon dioxide in field-grown strawberry.

Strawberry (Fragaria x ananassa) plants were grown in field plots at the current ambient [CO(2)], and at ambient + 300 and ambient + 600 mumol mol(-1) [CO(2)]. Approximately weekly measurements were made of single leaf gas exchange of upper canopy leaves from early spring through fall of two years, in order to determine the temperature dependence of the stimulation of photosynthesis by elevated [CO(2)], whether growth at elevated [CO(2)] resulted in acclimation of photosynthesis, and whether any photosynthetic acclimation was reduced when fruiting created additional demand for the products of photosynthesis. Stimulation of photosynthetic CO(2) assimilation by short-term increases in [CO(2)] increased strongly with measurement temperature. The stimulation exceeded that predicted from the kinetic characteristics of ribulose-1,5-bisphosphate carboxylase at all temperatures. Acclimation of photosynthesis to growth at elevated [CO(2)] was evident from early spring through summer, including the fruiting period in early summer, with lower rates under standard measurement conditions in plants grown at elevated [CO(2)]. The degree of acclimation increased with growth [CO(2)]. However, there were no significant differences between [CO(2)] treatments in total nitrogen per leaf area, and photosynthetic acclimation was reversed one day after switching the [CO(2)] treatments. Tests showed that acclimation did not result from a limitation of photosynthesis by triose phosphate utilization rate at elevated [CO(2)]. Photosynthetic acclimation was not evident during dry periods in midsummer, when the elevated [CO(2)] treatments conserved soil water and photosynthesis declined more at ambient than at elevated [CO(2)]. Acclimation was also not evident during the fall, when plants were vegetative, despite wet conditions and continued higher leaf starch content at elevated [CO(2)]. Stomatal conductance responded little to short-term changes in [CO(2)] except during drought, and changed in parallel with photosynthetic acclimation through the seasons in response to the long-term [CO(2)] treatments. The data do not support the hypothesis that source-sink balance controls the seasonal occurrence of photosynthetic acclimation to elevated [CO(2)] in this species.

A landscape-level assessment of understory diversity in upland forests of North-Central Wisconsin, USA

The study measured landscape level diversity of the understory plants of mature, upland forests in north-central Wisconsin USA. Habitat types were used to segregate the landscape along a moisture-nutrient gradient. Forty sites that had closed canopies, had been undisturbed for at least 20 years, and were at least 8 ha in size were used. The percent cover of groundlayer species was ocularly estimated in 12–18 randomly located, one meter square plots in June and August, 1995. Shrub cover was estimated by the line intercept method. Alpha, beta and gamma diversity were determined for early and late summer periods separately. Gamma diversity was quantified using a new method, affinity analysis, which generates a list of modal and outlier sites and calculates mosaic diversity, a measure of landscape complexity. Generally, communities in the middle of the moisture-nutrient gradient were modal, whereas those at the mesic end of the gradient were outlier. Mosaic diversity values were very similar for early summer and late summer (2.88±0.04, 2.95±0.03, respectively), but was much higher for both periods combined (3.95±0.07). Whittaker's Index (beta diversity) revealed varying rates of species turnover along presumed moisture and nutrient gradients, whereas species densities and richness were relatively constant among habitat types. A one-way analysis of variance of Shannon-Weaver values found no significant differences among habitat types (p≥0.05). Regional diversity mainly resulted from high beta values which appears to be primarily a function of the moisture gradient. The other factors influencing compositional differences among sites are variation in site history, especially disturbance, with niche partitioning and differences in seed dispersal capacity having a minor influence. The affinity analysis method indicated that sampling once per season is inadequate, and that many types of sites are modal. This method for estimating gamma (landscape) diversity shows considerable promise, but information on the processes that produce outlier sites is needed to fully understand and use the results of this method.

The influence of phytoplankton assemblage composition on biogeochemical characteristics and cycles in the southern Ross Sea, Antarctica

To test the hypothesis that phytoplankton assemblages dominated by different taxa have distinct biogeochemical characteristics and cycles, the temporal and spatial variations in phytoplankton biomass and composition were studied within the Ross Sea polynya, where diatoms and the haptophyte Phaeocystis antarctica are thought to have spatially distinct distributions. Two cruises were completed, with the first conducted in spring, 1994, and the second in late spring–early summer, 1995/1996. Ice concentrations decreased substantially from spring to summer. Mixed layer depths for the region decreased markedly in early spring and were relatively invariant thereafter; the strength of the stratification varied both in time and space. Mixed layers were greater in spring in assemblages dominated by diatoms (as determined by HPLC pigment concentrations) than those dominated by Phaeocystis antarctica, whereas in summer no difference was observed. Nutrient concentrations were initially high and near winter values, but decreased throughout November and December. Nitrate : phosphate removal ratios varied widely, with ratios exceeding 20 in spring but decreasing below 14 in summer. N : P removal ratios at stations dominated by diatoms were less than the Redfield ratio in both spring and summer, and at those stations dominated by P. antarctica the N : P removal ratio was ca. 19 in both seasons. Chlorophyll and particulate matter concentrations increased as nutrients decreased. Spatial and temporal variations of phytoplankton pigments occurred, with 19′-hexanoylfucoxanthin, a pigment of P. antarctica, exceeding 3.9 μg l −1 during spring in the south-central polynya, and fucoxanthin, an accessory pigment of diatoms, found in concentrations >1 μg l −1 in the western Ross Sea. The distributions were not mutually exclusive, and concentrations of both pigments were greatest in spring. The early growth of P. antarctica appears to be related to earlier stratification and disappearance of ice from the south-central Ross Sea. Ratios of FUCO/CHL were relatively invariant, but substantial changes in the HEX/CHL and POC/CHL ratios were observed through time. A one-dimensional nitrogen budget for the spring–early summer period suggests that much of the surface production was partitioned into particles, most (53%) of which remained in the upper 200 m. The rest was partitioned into dissolved organic matter (14%), remineralized as ammonium (19%), or sank from the surface layer as particles (13%). The region may serve as a useful analog to other polar systems, and an understanding of the processes controlling assemblage composition, production, and biomass accumulation may provide insights into biogeochemical cycles of other Antarctic environments.

Some aspects of the great success of lichens in Antarctica

The terrestrial vegetation in Antarctica is restricted to small, very isolated, ice-free areas on the continent and on the islands adjacent to the Peninsula region. Lichens, a symbiosis between a fungus and an alga or cyanobacterium, form the most prominent component in the vegetation. They have the greatest number of species compared with other cryptogamic and unicellular organisms. They are able to colonize all types of solid substrata and have a low mineral nutrient demand. Their physiological vigour is derived from high freezing tolerance and the ability to be photosynthetically activated by water vapour uptake from snow at temperatures as low as c. -20°C. Long-term monitoring in their natural habitats demonstrates that lichens are photosynthetically active at suboptimal temperatures. Locally, however, they can benefit from meltwater on insolated rocks, but only for short periods in early summer. Although at this time they may be exposed to substrate temperatures of &gt; 20°C and strong light they do not suffer from photostress. If, in winter, lichens are covered and kept dark by snow with temperatures close to 0°C, lichens enter a negative carbon balance. This effect may be relevant to lichens under conditions of global or regional warming.

Analysis of ozone pollution in the Shuaiba industrial area in Kuwait

Analysis of ozone pollution in the Shuaiba Industrial Area of Kuwait was performed over a period of 12 months, from December 1994 to November 1995. The Shuaiba Industrial Area houses several large scale industries which include a petroleum refinery, a complex of petrochemical plants, cement plant, chlorine and soda factory, desalination plant, power station, and shipping port for oil export. Measurements were performed by a mobile station capable of measuring 18 pollutants and meteorological parameters. Measurements were made at 5 minute intervals and were stored on a data station. Variables used in the analysis included measured concentrations for ozone, nitrogen oxides, and non‐methane hydrocarbons. In addition, the meteorological parameters, which included air temperature, wind speed and direction, and solar radiation were used in the analysis. The collected data were averaged on hourly basis, which were used to generate a monthly hour‐averages. Reported data are shown to be consistent with literature data for similar urban pollution data. In this regard, the maximums of the hourly‐averages for ozone concentration coincided with the minimums for the concentrations of nitrogen oxides and non‐methane hydrocarbons. Ozone maximums occurred on daily basis during the period from 12 pm to 2 pm. Formation rates of ozone were found to decrease during the very hot summer season and the mild winter season. The highest ozone concentrations were measured during the spring, early summer, and fall periods.

The timing of hunting in short-eared owls (Asio flammeus) in relation to the activity patterns of Orkney voles (Microtus arvalis orcadensis)

Using radio-telemetry, short-term cycles of activity, with a period of about 3 h, were detected in Orkney voles Microtus arvalis orcadensis and in one short-eared owl Asio flammeus, their principal predator. Visual observations showed that owls from four adjacent nests had similar activity patterns. These cycles tended to be synchronous both within and between the two species. Short-eared owls thus appeared to be foraging optimally by timing their hunting to coincide with peaks in vole activity, i.e. at times of maximum potential yield. The extent of diurnal activity in short-eared owls varied seasonally. Daytime activity was conspicuous for only a short period in spring and early summer. Otherwise owls were almost exclusively nocturnal. These seasonal changes in activity were probably a response to variations in vole diurnality, vole population size and daylength. Harassment and kleptoparasitism may have been additional influences that interacted with these seasonal factors to determine the extent of preferred nocturnal hunting. In addition, it is possible that the energetic constraints of breeding may force owls to hunt during daylight. Were males only to hunt at night then they may not be able to provide enough food for their mate and young at a time when nights are short and vole populations are only starting to increase.

The timing of hunting in short‐eared owls (Asio flammeus) in relation to the activity patterns of Orkney voles (Microtus arvalis orcadensis)

AbstractUsing radio‐telemetry, short‐term cycles of activity, with a period of about 3 h, were detected in Orkney voles Microtus arvalis orcadensis and in one short‐eared owl Asio flammeus, their principal predator. Visual observations showed that owls from four adjacent nests had similar activity patterns. These cycles tended to be synchronous both within and between the two species. Short‐eared owls thus appeared to be foraging optimally by timing their hunting to coincide with peaks in vole activity, i.e. at times of maximum potential yield. The extent of diurnal activity in short‐eared owls varied seasonally. Daytime activity was conspicuous for only a short period in spring and early summer. Otherwise owls were almost exclusively nocturnal. These seasonal changes in activity were probably a response to variations in vole diurnality, vole population size and daylength. Harassment and kleptoparasitism may have been additional influences that interacted with these seasonal factors to determine the extent of preferred nocturnal hunting. In addition, it is possible that the energetic constraints of breeding may force owls to hunt during daylight. Were males only to hunt at night then they may not be able to provide enough food for their mate and young at a time when nights are short and vole populations are only starting to increase.

The effect of grazing by cattle on animal performance and floristic composition in Nardus‐dominated swards

Four groups of six spring‐calving beef cows and their calves were allocated to two replicated grazing treatments on a Nardus stricta‐dominated hill pasture in the UK during six consecutive summer grazing seasons. Treatments were applied by continuous variable stocking to maintain a sward height of either 4–5 cm (short) or 6–7 cm (tall) between tussocks of N. stricta.Cows on both treatments ingested a greater proportion of N. stricta than was present in the sward. The short treatment reduced the herbage intake of cows proportionally by 0·35 (P &lt; 0·001) and reduced herbage digestibility by 0·03 (P &lt; 0·01) compared with the tall treatment. Cows lost 0·02 kg d−1 live weight on the short treatment but gained 0·27 kg d−1 live weight on the tall treatment (s.e.d. 0·077; P &lt; 0·001). Calf liveweight gains were 0·60 and 0·86 (s.e.d. 0·034; P &lt; 0·001) kg d−1 for the short and tall treatments respectively. The greatest liveweight gains for both cows and calves occurred during the first 5–6 weeks of the grazing season and differences between treatments increased over the season. Cattle on the short treatment consistently grazed a higher proportion of N. stricta tillers more closely than those on the tall treatment, and the percentage cover of N. stricta declined more rapidly on the short treatment. After 6 years of grazing there was a considerably greater (P &lt; 0·001) proportion of very small tussocks, i.e. less than 140 cm2 basal area, on the short treatment than on the tall treatment. The percentage cover of broad‐ and fine‐leaved grasses also declined, in contrast to previous studies. This may have been due to lower soil fertility on the site of the current experiment.It is concluded that high levels of utilization of N. stricta are incompatible with high levels of individual animal performance in lactating cows, although short periods in early summer may give acceptable performance. Lower levels of utilization such as that achieved on the 6–7 cm treatment resulted in moderate levels of animal performance and also gradually reduced the cover of N. stricta, although it took longer for the effect to be established.

Environmental quality of the Jordanian coastal waters of the Gulf of Aqaba, Red Sea

Abstract Records of long term (14 months) fine temporal resolution (weekly) monitoring of the ambient water temperature, dissolved oxygen concentration and percent saturation, the inorganic nutrients ammonia, nitrate, nitrite, phosphate and silicate and chlorophyll a concentrations were generated to assess sea water quality within the Jordanian coast of the Gulf of Aqaba. Surface water (1 m) samples were collected from four coastal stations, contrasting in their natural benthic habitats and adjacent human activities. Offshore surface water was also concurrently sampled at two locations. The offshore stations were reference sites. Modifications in the coastal water quality were assessed as the difference between the magnitude of a specific parameter recorded at a coastal station and the concurrently recorded value of the parameter at the reference offshore station, relative to the annual mean value at the reference offshore station. A sandy beach–sea grass bed habitat was found to have significantly positive modifications in chlorophyll a concentration, mainly during the spring–early summer period. A semi-enclosed harbour within the Port of Aqaba was found to be acutely modified with respect to all measured parameters. A coral reef exhibited positive modifications of nitrogen and dissolved oxgen concentrations and percent oxygen saturation during summer. An industrial site had consistently positive modifications in phosphate concentration, but not in nitrogen or chlorophyll a concentrations. In addition to these site specific modifications, ammonia and silicate concentrations were positively modified at all the coastal stations. Natural and anthropomorphic factors that shape the coastal water characteristics and result in the specific modifications are discussed.