Wetland effects on lake water quality in the Minneapolis/St. Paul metropolitan area

A method developed to evaluate the cumulative effect of wetland mosaics on water quality was applied to 33 lake watersheds in the seven-county region surrounding Minneapolis-St. Paul, Minnesota. A geographic information system (GIS) was used to record and measure landscape variables derived from aerial photos. Twenty-seven watershed land-use and land-cover variables were reduced to eight principal components which described 85% of the variance among watersheds. Relationships between lake water quality variables and the first six principal components plus an index of lake mixis were analyzed through stepwise multiple regression analysis. A combination of three landscape components (wetland/watershed area, agriculture/wetlands, and forest/soils components) explained 49% of the variance in a trophic state index, even though most of the lakes examined were already highly eutrophic, and thus were influenced by internal loading. The regression equations explained a range of 14 to 76% of the variation in individual water quality variables. Forested land-use was associated with lower lake trophic state, chloride, and lead. High lake trophic state was associated with agricultural land-use and with wetland distance from the lake of interest. The extent of wetlands was associated with low total lead and high color in lakes downstream. Wet meadows or herbaceous, seasonally-flooded wetlands contributed more to lake water color than did cattail marshes.     

Light sources with different spectra affect root and mycorrhiza formation in Scots pine in vitro

We studied the effects of broad-spectrum light quality on the interaction between the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch and Scots pine (Pinus sylvestris L.) seedlings and hypocotyl cuttings cultured in vitro. The light sources were cool white (CW), warm white (WW) and red-rich daylight (RD) fluorescent lamps. Inoculation with P. tinctorius enhanced adventitious root formation of the cuttings in all light treatments. Rooting of the inoculated cuttings was highest in WW light (89%), followed by CW (73%) and RD light (66%). During 6 weeks of in vitro culture, rooted cuttings formed only a few lateral roots. The fungus grew over lateral roots, but the Hartig net was absent in all light treatments. In non-inoculated cuttings, neither root formation nor subsequent root growth was affected by light quality. In the seedling experiment, inoculation in the WW treatment resulted in a significantly (P < 0.05) greater number of lateral roots than inoculation in the RD treatment. The percentage of lateral roots covered with fungal hyphae was also highest in WW light (62%), followed by CW (50%) and RD (27%) light. A similar pattern was observed in the intensity of Hartig net formation. We conclude that effects of broad-spectrum light quality on the ectomycorrhizal fungus-root interaction are dependent on the developmental stage of the root.     

Contrasting effects of elevated carbon dioxide concentration and temperature on Rubisco activity,chlorophyll fluorescence,needle ultrastructure and secondary metabolites in conifer seedlings

Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings were grown for 50 days in growth chambers in an ambient or twice ambient carbon dioxide concentration ([CO2]) at a day/night temperature of 19/12 degrees C or 23/16 degrees C. Although elevated [CO2] (EC) had only slight effects on the growth parameters measured, elevated temperature (ET) increased above ground dry mass of both species. Among treatments, biomass accumulation of both species was greatest in the combined EC + ET treatment. The EC treatment induced thylakoid swelling and increased numbers of plastoglobuli observed in Scots pine needles. Although EC had little effect on Rubisco protein or N concentration of needles, ET had a large effect on N-containing compounds and enhanced N allocation from 1-year-old needles. Terpenoids were more responsive to EC and ET than total phenolics. Generally, terpene concentrations were reduced by EC and increased by ET. Increased terpenoid concentrations in response to ET might be associated with thermotolerance of photosynthesis. In Norway spruce, EC decreased total phenolic concentrations in needles, probably as a result of increased growth. We conclude that, in seedlings of these boreal species, the effects of elevated [CO2] on the studied parameters were small compared with the effects of elevated temperature.     

Prolamin hydrolysis in wheat sourdoughs with differing proteolytic activities

The prolamins of wheat, rye, and barley contain structures that are harmful to gluten-sensitive people, and an extensive degradation of these prolamins during food processing might eliminate this problem. Sourdough fermentation is a cereal food process during which some protein degradation occurs. In this study, the prolamin hydrolysis that occurred in a high-proteolytic-activity germinated-wheat sourdough (GWSD) was compared with that of wheat sourdough systems which contained moderate or no proteolytic activities. Virtually all of the wheat prolamins (gliadins and glutenins) were degraded during the GWSD fermentation. Quantification of its prolamin levels confirmed that extensive prolamin hydrolysis had occurred in the GWSD. This hydrolysis was attributed to the cysteine proteinase activities of the germinated wheat. The use of high-proteolytic sourdoughs in baking could make it possible to prepare new low-prolamin cereal-based products for use by gluten-sensitive people, who could then diversify their diets by including these whole-grain containing products into their every-day diets.     

Breeding bird response to partially harvested riparian management zones

We compared avian communities among three timber harvesting treatments in 45-m wide even-age riparian management zones (RMZs) placed between upland clearcuts and along one side of first- or second-order streams in northern Minnesota, USA. The RMZs had three treatments: (1) unharvested, (2) intermediate residual basal area (RBA) (targeted goal 11.5 m²/ha, realized 16.0 m²/ha), and (3) low RBA (targeted goal 5.7 m²/ha, realized 8.7 m²/ha). Surveys were conducted one year pre-harvest and three consecutive years post-harvest. There was no change in species richness, diversity, or total abundance associated with harvest but there were shifts in the types of birds within the community. In particular, White-throated Sparrows (Zonotrichia albicollis) and Chestnut-sided Warblers (Dendroica pensylvanica) increased while Ovenbirds (Seiurus aurocapilla) and Red-eyed Vireos (Vireo olivaceus) decreased. The decline of avian species associated with mature forest in the partially harvested treatments relative to controls indicates that maintaining an unharvested RMZ adjacent to an upland harvest may aid in maintaining avian species associated mature forest in Minnesota for at least three years post-harvest. However, our observations do not reflect reproductive success, which is an area for future research.     

Detection of traces of tetracyclines from fish with a bioluminescent sensor strain incorporating bacterial luciferase reporter genes

Bioluminescent Escherichia coli K-12 strain for the specific detection of the tetracycline family of antimicrobial agents was optimized to work with fish samples. The biosensing strain contains a plasmid incorporating the bacterial luciferase operon of Photorhabdus luminescens under the control of the tetracycline responsive element from transposon Tn10 (Korpela et al. Anal. Chem. 1998, 70, 4457-4462). The extraction procedure of oxytetracycline from rainbow trout (Oncorhynchus mykiss) tissue was optimized. There was neither need for centrifugation of homogenized tissue nor use of organic solvents. The lowest levels of detection of tetracycline and oxytetracycline from spiked fish tissue were 20 and 50 microg/kg, respectively, in a 2-h assay. The optimized assay protocol was tested with fish that were given a single oral dose of high and low concentrations of oxytetracycline. The assay was able to detect oxytetracycline residues below the European Union maximum residue limits, and the results correlated well with those obtained by conventional HPLC (R = 0.81).     

Fecal contamination of Finnish fresh waters in 1962–1984

We investigated fecal contamination of Finnish lakes and rivers on the basis of 132 476 observations of total coliform bacteria (TC), thermotolerant coliform bacteria (ThC) and fecal streptococci (FS) enumerated in a nationwide monitoring programme during the period 1962–1984. The number of analyses of TC was 19 672, of ThC 16 456 and of FS 96 348. The waters were classified into three groups, influenced mainly by municipal wastewaters, industrial wastewaters or diffuse loading. Annual median bacterial concentrations were used for presenting the trends. All the concentrations decreased until about 1976, except TC concentrations in the industrialized and diffuse load areas. Since 1976 the concentrations decreased more slowly or occasionally even increased, especially those of TC. In the whole data the dynamics of bacterial loads (CFU s^?1) were similar to those of annual median bacterial concentrations. The most probable explanations for the declining bacterial concentrations are increase in the human population served by wastewater treatment plants, improved sewage treatment processes, decreased wastewater volumes of the forest industry and decrease in the number of cattle. The monitoring programme continues.     

Experimental Salmonella-associated conjunctivitis in cats.

Cats were infected experimentally with Salmonella typhimurium via the conjunctiva. Clinical signs consisted of lacrimation, conjunctivitis, blepharospasm, prominent nictitating membrane and scleral injection. These signs were accompanied by an absolute neutrophilia and conjunctival smears indicative of moderate to severe suppurative inflammation. Ocular signs disappeared by day 6 postinfection. Salmonella typhimurium was cultured intermittently from the inoculated conjunctivae and rectal swabs through day 7. At necropsy, mesenteric and cervical lymph nodes were enlarged. Histopathological findings included chronic conjunctivitis and lymphoid hyperplasia in cervical and mesenteric lymph nodes. This study confirms that S. typhimurium can cause a primary conjunctivitis and that the ocular route of infection can lead to fecal excretion of Salmonella, in the absence of other clinical manifestations.