Influence of light fleck and low light on foliar injury and physiological responses of two hybrid poplar clones to ozone

Five-month old hybrid poplar clones NE388 and NE359 were exposed to square-wave 30, 55, and 80 ppb O(3) (8 h/day, 7 day/week) under constant high light (HL) and light fleck (LF) during 28 May-29 June 1999, and exposed to 30 and 55 ppb O(3) under HL, LF, and constant low light (LL) during 22 May-28 June 2000 within Continuously Stirred Tank Reactors (CSTR) in a greenhouse. Ramets of these two hybrid clones received similar total photosynthetically active radiation (PAR) within the LF and LL treatments. Visible foliar symptoms, leaf gas exchange, and growth were measured. More severe O(3) induced foliar symptoms were observed on ramets within the LF and LL treatments than within the HL treatment for both clones. The LF treatment resulted in significantly greater foliar injury than the LL treatment for NE388. The LF and LL treatments generally resulted in lower photosynthetic rates (Pn) for both clones, but did not affect stomatal conductance (g(wv)); therefore, the ratios of g(wv)/Pn and the O(3) uptake/Pn were greatest in plants grown under the LF treatment, followed by those grown under LL treatment; plants grown under HL had the lowest ratios of g(wv)/Pn and O(3) uptake/Pn. Greater ratios of g(wv)/Pn and O(3) uptake/Pn were consistently associated with more severe visible foliar symptoms. The negative impacts of the LF treatment on growth were greater than those of the LL treatment. Results indicate that not only the integral, but also the pattern of photo flux density, may affect carbon gain in plants. Increased foliar injury may be expected under light fleck conditions due to the limited repair capacity as a result of continuity of O(3) uptake while photosynthesis decreases under LL conditions.     

Modelling of physical and reactive processes during biodegradation of a hydrocarbon plume under transient groundwater flow conditions

Numerical experiments of non-reactive and reactive transport were carried out to quantify the influence of a seasonally varying, transient flow field on transport and natural attenuation at a hydrocarbon-contaminated field site. Different numerical schemes for solving advective transport were compared to assess their capability to model low transversal dispersivities in transient flow fields. For the field site, it is shown that vertical plume spreading is largely inhibited, particularly if sorption is taken into account. For the reactive simulations, a biodegradation reaction module for the geochemical transport model PHT3D was developed. Results of the reactive transport simulations show that under the site-specific conditions the temporal variations in groundwater flow do, to a modest extent, affect average biodegradation rates and average total (dissolved) contaminant mass in the aquifer. The model simulations demonstrate that the seasonal variability in groundwater flow only results in significantly enhanced biodegradation rates when a differential sorption of electron donor (toluene) and electron acceptor (sulfate) is assumed.     

Monitoring land-use change effects on soil carbon in New Zealand: quantifying baseline soil carbon stocks

We designed a soil carbon monitoring system for New Zealand using country-specific land use and soil carbon information. The system pre-stratifies the country by soil type, climate, and land use. Soils were placed in six IPCC soil categories; Podzols were added as they are widespread throughout New Zealand. Temperature was stratified into two categories, each spanning 7 degrees C. Moisture categories were based on water balance, and included five categories. Temperature and moisture stratification was based on the USDA Soil Classification system. Land use (10 categories) was based on 1980s survey data. Overall, 39 combinations of these three factors (cells) described 93% of the New Zealand landscape. Geo-referenced soil carbon data (carbon concentration and bulk density) were used to quantify average soil carbon for each of the 39 cells. Aggregating the polygons gave an estimated 1990 soil carbon baseline of 1152+/-44, 1439+/-73, and 1602+/-167 Mt C (mean+/-S.D.) for the 0-0.1, 0.1-0.3, and 0.3-1.0 m depth increments (not including forest floor carbon). The system described could also be used to quantify equilibrium changes in soil C associated with land-use change if land use is updated periodically.     

Home transport and wastage: environmentally relevant household activities in the life cycle of food

In environmental systems analysis of food production systems, the consumer phase (home transport, cooking, storing, and wastage) is an important contributor to the total life-cycle environmental impact. However, households are the least investigated part of the food chain. Information gathering about households involves difficulties; the number of households is large, and food-related activities are embedded in other household activities. In cooperation between researchers from environmental systems analysis and consumer research, Swedish households were surveyed by questionnaire, diary, and interviews. Data on home transport of food and wastage were collected. The average weekly driving distance was 28 to 63 km per household, depending on how trips made in conjunction with other errands are allocated. The wastage of prepared food ranged between 0 and 34% for different food categories, and wastage from storing between 0 and 164% (more food was discarded, e.g. by cleaning out a cupboard, than consumed). In both cases dairy products scored highest.     

Immunohistochemical detection of polychlorinated biphenyls in field collected damselfish (Abudefduf sordidus; Pomacentridae) embryos and larvae

Antibodies against polychlorinated biphenyls (PCBs) were used to determine if immunohistochemical methods could detect PCBs in embryos and larvae of a territorial coral reef fish (Abudefduf sordidus; Pomacentridae) collected from Johnston Atoll, Central Pacific Ocean. Sites with differing levels of contamination were sampled, one with relatively high sediment PCB concentrations of up to 389.0 ng/g and another with low PCB concentrations of only 0.5 ng/g. Immunostaining suggested that PCB concentrations were higher in fish larvae from the PCB contaminated site and that PCB concentrations within abnormal embryos were higher than normal embryos from the same nest. This technique will be useful for detecting exposed populations in the field and assessing correlations with adverse effects, particularly in potential indicator organisms such as Abudefduf sordidus.     

Feeding ecology and interannual variations in diet of larval jack mackerel,Trachurus declivis (Pisces: Carangidae), from coastal waters of eastern Tasmania

Changes in the biochemical composition of the digestive gland and in the proteins of the mantle muscle of Sepia officinalis L, collected in September 1989 from the Ria de Vigo (northwest Spain), were measured during periods of 2, 4, 10 and >53 d starvation. The digestive gland lost weight faster than the rest of the body throughout the whole period of starvation. In the digestive gland, carbohydrate and protein contents did not change during starvation; however, lipid levels decreased significantly after 53 d. Phospholipid content increased during longterm starvation. The content of free fatty acids rose after 16 d. Sterols, diacylglycerylethers, triacylglycerols and carotenoids contents did not change significantly. Of the total fatty acids, 18:0, 20:2n6, 20:4n6 and the monounsaturated moieties were preferentially consumed; others, such as 22:5n3, 22:6n3 and 16:4n1, were selectively retained. In the mantle muscle, water content increased and total protein content decreased. The myofibrillar proteins decreased after 53 d starvation, whereas the sarcoplasmic fraction did not change and the stromatic proteins increased. No changes were observed in the electrophoretic patterns of sarcoplasmic and myofibrillar proteins. The digestive gland of S. officinalis does not seem to be an important reserve organ during long-term starvation, but does seem to be important during shortterm starvation.     

No. 2 fuel oil compounds in Mytilus edulis

Mytilus edulis contaminated by a brief 2-d exposure to a slick from a No. 2 fuel oil spill in the Cape Cod Canal, Massachusetts, USA were sampled six times during an 86-d post-spill period to study the rate of release of fuel oil compounds under field conditions. Detailed measurements of compounds by high resolution glass capillary gas chromatography and quantitative glass capillary gas chromatography-mass spectrometry-computer systems analyses provided a more comprehensive examination of release rates of different types of compounds. Biological half-lives were calculated for selected compounds for the first 21 d during which the release rates were exponential. Typical half-lives were n-alkanes, 0.2–0.8 d; pristane, 1.5 d; C-2 (dimethyl or ethyl) napthalenes, 0.9 d; methyl phenanthrenes, 1.7 d. Changes in relative ratios of C-2 phenanthrenes during the release period were observed. The evidence available to date strongly supports the role of molecular weight and accompanying properties of water solubility as the main controlling factors in the rate of release of fuel oil compounds by M. edulis. However, the data for the rapid release of n-alkanes and C-2 phenanthrenes also indicate molecular type and molecular configuration as additional key factors. The data from this study are compared and contrasted to data from short term experimental studies in the laboratory, longer term studies from chronic exposure conditions, and data from two other oil spills with longer term exposure.     

Should heterogeneity be the basis for conservation? Grassland bird response to fire and grazing.

In tallgrass prairie, disturbances such as grazing and fire can generate patchiness across the landscape, contributing to a shifting mosaic that presumably enhances biodiversity. Grassland birds evolved within the context of this shifting mosaic, with some species restricted to one or two patch types created under spatially and temporally distinct disturbance regimes. Thus, management-driven reductions in heterogeneity may be partly responsible for declines in numbers of grassland birds. We experimentally altered spatial heterogeneity of vegetation structure within a tallgrass prairie by varying the spatial and temporal extent of fire and by allowing grazing animals to move freely among burned and unburned patches (patch treatment). We contrasted this disturbance regime with traditional agricultural management of the region that promotes homogeneity (traditional treatment). We monitored grassland bird abundance during the breeding seasons of 2001-2003 to determine the influence of altered spatial heterogeneity on the grassland bird community. Focal disturbances of patch burning and grazing that shifted through the landscape over several years resulted in a more heterogeneous pattern of vegetation than uniform application of fire and grazing. Greater spatial heterogeneity in vegetation provided greater variability in the grassland bird community. Some bird species occurred in greatest abundance within focally disturbed patches, while others occurred in relatively undisturbed patches in our patch treatment. Henslow's Sparrow, a declining species, occurred only within the patch treatment. Upland Sandpiper and some other species were more abundant on recently disturbed patches within the same treatment. The patch burn treatment created the entire gradient of vegetation structure required to maintain a suite of grassland bird species that differ in habitat preferences. Our study demonstrated that increasing spatial and temporal heterogeneity of disturbance in grasslands increases variability in vegetation structure that results in greater variability at higher trophic levels. Thus, management that creates a shifting mosaic using spatially and temporally discrete disturbances in grasslands can be a useful tool in conservation. In the case of North American tallgrass prairie, discrete fires that capitalize on preferential grazing behavior of large ungulates promote a shifting mosaic of habitat types that maintain biodiversity and agricultural productivity.     

Chalk and limestone quarries as wildlife habitats

Natural recolonisation by volunteer species of chalk and limestone quarries has led to the development of attractive and species-rich communities in many parts of the United Kingdom. These communities have a basic similarity in floristic composition wherever they occur, but they also show a great deal of individual variation resulting from differences in the location, history and variability of the quarry itself and in the nature of the surrounding habitats. The interest of old quarries may be enhanced by the presence of individually rare or local species and especially by their refuge status in relation to the loss of semi-natural calcareous grassland in the district. It is suggested that some sites play an important role in wildlife conservation and that this factor should be considered in any programme of land reclamation. Natural regeneration is very slow compared with the rate of land use in modern quarrying but the development of ecological techniques may make it possible to rehabilitate derelict and barren sites for amenity and conservation purposes using older quarries as models.     

The effect of inhibitors of photosynthesis on zooxanthellae in corals and other marine invertebrates

The effect of the selective photosynthesis inhibitors Monuron (CMU), Diuron (DCMU) and methyl viologen on intact algal-marine invertebrate symbiotic associations was studied. CMU or DCMU (5x10^-4M) completely inhibited photosynthesis, both in intact branches, and in suspensions of isolated zooxanthellae from the reef-building coral Pocillopora damicornis. The inhibitory effect was totally reversible in 1 to 3 h after removal of the inhibitor. Similar inhibition of photosynthesis occurred in 8 other marine coelenterates symbiotic with zooxanthellae, and in 1 marine gastropod symbiotic with functional chloroplasts. Neither CMU nor DCMU appeared to affect behavior of the various hosts, such as swimming, phototaxis, phototropism, photoreception, tentacle contraction, ciliary beating and locomotion. Methyl viologen, however, was ineffective in inhibiting photosynthesis in intact P. damicornis at low concentrations, and lethal to the tissues at high concentrations. These observations indicate that CMU and DCMU are potential useful tools for investigation of symbiotic associations. DCMU (5x10^-4M) also reversibly inhibited light-enhanced calcification in P. damicornis. This strongly suggests that light-enhanced calcification is largely photosynthesis dependent, and probably not dependent on some other photobiological effect.Contribution No. 385, Hawaii Institute of Marine Biology, University of Hawaii