Government of Canada

About: Government of Canada is a government organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Monetary policy & Productivity. The organization has 796 authors who have published 886 publications receiving 21366 citations. The organization is also known as: federal government of Canada & Her Majesty's Government.

Phytoplankton Community Responses to Acidification of Lake 223, Experimental Lakes Area, Northwestern Ontario

Abstract: From 1976 to 1983 the pH of Lake 223 was artificially lowered by additions of H2SO4. From an initial level of 6.7, the pH was lowered at a rate of 0.5 pH units a year until it reached 5.0 and was held there for 3 yr. The decrease in pH caused major changes in the epilimnetic phytoplankton community in this lake. Biomass increased as pH decreased. Chlorophyte (Chlorella) abundance increased as pH decreased from 6.1 to 5.6 while Cyanophytes (Merismopedia and Chroococcus) and dinoflagellates (Gymnodinium and Peridinium) dominated once pH decreased below 5.6. Community diversities decreased because of these species shifts and a decrease in the number of species. The amount of edible biomass increased as the pH decreased from 6.7 to 5.6, then declined as pH decreased to 5.0.

Trichoptera and substrate stability in the Ochre River, Manitoba

Abstract: A total of 3999 Trichoptera adults, represented by 8 families, 17 genera and 33 species was collected in emergence traps in 1983 and 1984 from five stations on the Ochre River, Manitoba (50° 04′ N, 99° 48′ W). Species composition for the two years was comparable, but as the result of a summer spate in 1984, abundance was only 40% of that in 1983. Species diversity by station was negatively correlated with substrate instability of the reach, whereas density per trap was negatively correlated with substrate instability and local factors such as sedimentation in some reaches following peak discharges. Analysis of historical peak discharge records indicated that relatively infrequent mid-summer spates had a detrimental effect on subsequent emergence of the Trichoptera fauna. The combination of spates and unstable stream bed substrate resulting from land use practices in the drainage basin have resulted in an impoverished caddisfly fauna in the Ochre River in comparison with other rivers in Manitoba.

Scanning proton microprobe analysis of strontium in an arctic charr, Salvelinus alpinus, otolith: implications for the interpretation of anadromy

Abstract: Scanning proton microprobe imaging has been used to map the distribution of strontium (Sr) in an arctic charr, Salvelinus alpinus, otolith. X-ray maps show that Sr variation follows an oscillatory zoned pattern which correlates with optically resolved zones (annuli). The internal region of the otolith shows optical zonation but no significant Sr content. Comparison of the optical image with the Sr X-ray map provides evidence of when the fish entered a high Sr environment. This may be interpreted as when the fish migrated from fresh water to a marine environment; this particular fish first migrated to sea in its eighth year. Micro-PIXE point analysis was used to determine the abundance of Sr in annuli along a radius from the nucleus to an outer edge; Sr levels in the internal region were about 10 ppm and variation in the outer zoned region was between 62 and 175 ppm. Detection limits for Sr are in the 1–2 ppm range. Other trace elements, such as transition elements, were found to be present in some growth regions in the 1–20 ppm range. Proton beam analysis is a non-destructive analytical technique capable of preserving the spatial integrity of trace-element data in otoliths such that element distribution may be linked to the growth structure of the otolith.

Bioavailability of six organic chemicals to Chironomus Tentans larvae in sediment and water

Abstract: Uptake and elimination of 14C-labeled terbutryn, fluridone, triphenyl phosphate (TPP), trans-permethrin, methoxychlor and 2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) by Chironomus tentans larvae were studied in sediment-water systems. Animals were exposed to three different sediments containing 50 to 500 μg/kg (wet weight) of each chemical, or were held in screened containers in water above the treated sediment for 24 or 96-h. Elimination of radioactivity was determined over a 48-h interval. Results were analyzed by use of a one-compartment kinetic model. Larvae exposed in sand or in water above sand had significantly higher concentrations of each chemical than those exposed in or above river (silty) or pond (silty clay) sediments. Uptake of terbutryn and fluridone, two hydrophilic compounds, was similar (24-h exposure) to that of methoxychlor and greater than that for TPP, trans-permethrin or HCBP, due to much greater partitioning of the former compounds into water above each sediment. TPP, trans-permethrin, methoxychlor and HCBP concentrations were significantly higher in larvae from sediment than in animals held in water above sediment. Uptake rate constants from water for each chemical were much greater than those for sediment, but due to the relatively large sediment-to-water ratio (1:5) and the high proportion of chemical in sediment, relative contributions of sediment and water uptake to body burden were similar. Assimilation of each compound by larvae from ingested sediments appeared to be negligible except for TPP and HCBP. Estimates of assimilation of TPP and HCBP in sand-water systems were much greater than those for sediments with higher organic matter content.