Aquatic acetylene-reduction techniques: solutions to several problems

1976 ◽  
Vol 22 (1) ◽  
pp. 43-51 ◽  
Author(s):  
R. J. Flett ◽  
R. D. Hamilton ◽  
N. E. R. Campbell
Keyword(s):  
Nitrogen Fixation ◽  
Depth Profile ◽  
Acetylene Reduction ◽  
Canadian Shield ◽  
Experimental Lakes Area ◽  
Reduction Techniques ◽  
Northwestern Ontario ◽  
Refined Technique

Previous methods of performing aquatic acetylene-reduction assays are described and several problems associated with them are discussed. A refinement of these older techniques is introduced and problems that it overcomes are also discussed. A depth profile of nitrogen fixation (C2H4 production), obtained by the refined technique, is shown for a fertilized Canadian Shield lake in the Experimental Lakes Area of northwestern Ontario.

Comparison of the Nitrogen-15 Uptake and Acetylene Reduction Methods for Estimating the Rates of Nitrogen Fixation by Freshwater Blue-Green Algae

1980 ◽  
Vol 37 (3) ◽  
pp. 488-493 ◽  
Author(s):  
B. M. Graham ◽  
R. D. Hamilton ◽  
N. E. R. Campbell
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Experimental Lakes Area ◽  
Method Of Calculation ◽  
Blue Green Algae ◽  
Northwestern Ontario ◽  
Green Algal ◽  
Reduction Methods ◽  
Ratio Determination ◽  
Relationship Of

The relationship of acetylene reduction to nitrogen-15 uptake was investigated using blue-green algal populations in three lakes in the Experimental Lakes Area, northwestern Ontario. Nitrogen fixation rates, as estimated with both techniques, were compared and acetylene to nitrogen ratios determined. Lake ratios ranged from 6.3 to 9.1 moles of acetylene reduced per mole of nitrogen fixed varying from sample to sample and also with the method of calculation. Explanations of the discrepancies between theoretical and empirical ratios are discussed; these include hypotheses of excretion of assimilated nitrogen-15 labeled material and interference from nitrogenase-mediated hydrogen production.Key words: acetylene reduction, nitrogen-15 uptake, nitrogen fixation, C2H2/N2 ratio determination

Preliminary Chemical Characterization of Waters in the Experimental Lakes Area, Northwestern Ontario

1971 ◽  
Vol 28 (2) ◽  
pp. 171-187 ◽  
Author(s):  
F. A. J. Armstrong ◽  
D. W. Schindler
Keyword(s):  
Chemical Characterization ◽  
Specific Conductance ◽  
Canadian Shield ◽  
Nitrogen And Phosphorus ◽  
Experimental Lakes Area ◽  
Mean Values ◽  
Dissolved Phosphorus ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
Northwestern Ontario

Water analyses in 1968 and 1969 from 40 small lakes within a small area of the Canadian Shield in northwestern Ontario gave mean values for Ca, Na, Mg, and K of 1.6, 0.9, 0.9, and 0.4 mg/liter with Ca > Na > Mg > K on a molar basis. HCO3, SO4, and Cl (on a smaller number of samples) were 4.1, 3.0, and 1.4 mg/liter. Total CO2 was variable in the range 0.3–12.0 mg/liter. Specific conductance was in the range 10–35 μmho/cm at 25 C and pH 5.4–7.5. Color was < 5–150 Hazen units, and plant pigments (as chlorophyll a) < 1–21 μg/liter. Total dissolved nitrogen was in the range 110–300 mg N/liter and total dissolved phosphorus 3–20 μg P/liter. NO3-N and PO4-P were often undetectable in summer, and reached winter maxima around 100 and 10 μg/liter.Total dissolved nitrogen and phosphorus contents of five lakes were computed at the beginning and end of periods of several weeks during summer stagnation. Changes were negligibly small in three of the deeper lakes, but the two shallowest showed increases of 0.22 and 0.62 g N/m2 and 0.03 and 0.13 g P/m2. Analyses of precipitation and stream waters were used, with stream flow rates, to calculate input and output of nutrients from four of these lakes during the same periods. Retention of nutrients had occurred in all, and it was concluded that in the two deeper lakes nutrients had been lost to the sediments, whereas in the two shallower ones the increases in dissolved nutrients found were derived from the sediments.Analyses of 33 other Canadian Shield lake areas and of 13 other dilute lakes in other regions are tabulated. Comparison with the Experimental Lakes Area (ELA) lakes shows that the latter are more dilute than any in the Shield area except for some in the Northwest Territories, and much more dilute than any others in the world except for some alpine lakes in California.

Pelagic distribution of lake trout (Salvelinus namaycush) in small Canadian Shield lakes with respect to temperature, dissolved oxygen, and light

1998 ◽  
Vol 55 (1) ◽  
pp. 170-179 ◽  
Author(s):  
Todd J Sellers ◽  
Brian R Parker ◽  
David W Schindler ◽  
William M Tonn
Keyword(s):  
Light Intensity ◽  
Dissolved Oxygen ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Canadian Shield ◽  
Small Lakes ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Oxygenated Water ◽  
Shield Lakes

The distribution of lake trout (Salvelinus namaycush) with respect to water temperature, dissolved oxygen, and light intensity was surveyed in three small Canadian Shield lakes at the Experimental Lakes Area, northwestern Ontario. Based on hydroacoustic and gillnet surveys, there was considerable variation among lakes in temperatures occupied by lake trout during the summer. During the day, lake trout were concentrated at 4-8°C in Lake 375, broadly distributed from 6 to 15°C in Lake 442, and concentrated in the epilimnion at 19°C in Lake 468. At night, lake trout in all lakes occupied epilimnetic waters at 19-20°C. Lake trout inhabited highly oxygenated water, with 75-90% of fish at >6 mg dissolved oxygen ·L-1 throughout the spring and summer in all three lakes. Light intensity did not affect lake trout distribution in Lake 468 but may have contributed to lake trout daytime descent into cool waters in Lakes 375 and 442. We suggest that previously assumed niche boundaries of lake trout do not adequately describe critical habitat for the species in small lakes, the same lakes that are likely most sensitive to erosion of such habitat.

scholarly journals Nitrogen Fixation in Canadian Precambrian Shield Lakes

1980 ◽  
Vol 37 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Robert J. Flett ◽  
David W. Schindler ◽  
Robert D. Hamilton ◽  
Norman E. R. Campbell
Keyword(s):  
Nitrogen Fixation ◽  
Green Algae ◽  
Acetylene Reduction ◽  
Low Oxygen ◽  
Experimental Lakes Area ◽  
Blue Green Algae ◽  
Methane Oxidizing Bacteria ◽  
Bloom Formation ◽  
Littoral Sediments ◽  
Shield Lakes

Acetylene reduction assays in the water columns of several artificially eutrophied lakes in the Experimental Lakes Area revealed that nitrogen fixation by planktonic blue-green algae could supply a significant portion of the nitrogen income to these lakes. In situ 15N2 uptake experiments in one lake indicated that nitrogen fixation was proceeding at a slow rate in the low oxygen region of the thermocline, probably via methane oxidizing bacteria. Other 15N2 uptake experiments in the littoral sediments of an oligotrophic lake failed to detect nitrogen fixation. Generally, algal nitrogen fixation occurred in Shield lakes that were subject to total N:total P loading ratios (wt/wt) of less than approximately 10. This suggests that in these lakes phosphorus removal from loading is the best technique for eutrophication abatement and that nitrogen removal, when applied by itself, may be detrimental because it could encourage bloom formation of nitrogen fixing blue-green algae.Key words: nitrogen fixation, eutrophication, blue-green algae, acetylene reduction, nitrogen-15

Aphanizomenon schindleri sp.nov.: a new nostocacean cyanoprokaryote from the Experimental Lakes Area, northwestern Ontario

1994 ◽  
Vol 51 (10) ◽  
pp. 2267-2273 ◽  
Author(s):  
Hedy J. Kling ◽  
David L. Findlay ◽  
Jiri Komárek
Keyword(s):  
Cell Shape ◽  
Canadian Shield ◽  
Experimental Lakes Area ◽  
N Limitation ◽  
Northwestern Ontario ◽  
Cell Dimensions ◽  
N Loading ◽  
Shield Lakes

Aphanizomenon schindleri sp.nov., a new nostocacean, bluegreen, cyanoprokaryote (cyanobacterium), is described from artificially eutrophied Canadian Shield lakes in the Experimental Lakes Area, northwestern Ontario. It is unique to low conductivity Canadian Shield waters to which nutrients have been added, and it became the dominant bloom species after years of phosphorus (P) and nitrogen (N) loading followed by N limitation (N:P ≤ 5:1 by mass) (Findlay et al. 1994. Can. J. Fish. Aquat. Sci. 51: 2254–2266). The new Aphanizomenon species appears to be most closely related to A. gracile but also resembles species of Anabaena with straight filaments. It differs from other species of Aphanizomenon in cell dimensions, length and width of akinetes and heterocytes, and in akinete and end cell shape.

Land water linkages: influences of riparian deforestation on lake thermocline depth and possible consequences for cold stenotherms

1997 ◽  
Vol 54 (6) ◽  
pp. 1299-1305 ◽  
Author(s):  
Robert France
Keyword(s):  
Thermal Stratification ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Thermocline Depth ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Riparian Trees ◽  
Tree Removal ◽  
Riparian Tree ◽  
Land Water

The purpose of the present study was to determine if riparian deforestation would expose lake surfaces to stronger winds and therefore bring about deepening of thermoclines and resulting habitat losses for cold stenotherms such as lake trout (Salvelinus namaycush). Removal of protective riparian trees through wind blowdown and two wildfires was found to triple the overwater windspeeds and produce thermocline deepening in two lakes at the Experimental Lakes Area. A survey of thermal stratification patterns in 63 northwestern Ontario lakes showed that lakes around which riparian trees had been removed a decade before through either clearcutting or by a wildfire were found to have thermocline depths over 2 m deeper per unit fetch length compared with lakes surrounded by mature forests. Riparian tree removal will therefore exacerbate hypolimnion habitat losses for cold stenotherms that have already been documented to be occurring as a result of lake acidification, eutrophication, and climate warming.

Overexpression of the dctA gene in Rhizobium meliloti: effect on transport of C4 dicarboxylates and symbiotic nitrogen fixation

1992 ◽  
Vol 38 (6) ◽  
pp. 555-562 ◽  
Author(s):  
Vipin Rastogi ◽  
Monika Labes ◽  
Turlough Finan ◽  
Robert Watson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Symbiotic Nitrogen Fixation ◽  
Plasmid Stability ◽  
Rhizobium Meliloti ◽  
Mrna Synthesis ◽  
Dicarboxylate Transport ◽  
Fusion Strain ◽  
Tryptophan Operon ◽  
Specific Mrna

Symbiotic nitrogen fixation may be limited by the transport of C4 dicarboxylates into bacteroids in the nodule for use as a carbon and energy source. In an attempt to increase dicarboxylate transport, a plasmid was constructed in which the Rhizobium meliloti structural transport gene dctA was fused to a tryptophan operon promoter from Salmonella typhimurium, trpPO. This resulted in a functional dctA gene that was no longer under the control of the dctBD regulatory genes, but the recombinant plasmid was found to be unstable in R. meliloti. To stably integrate the trpPO-dctA fusion, it was recloned into pBR325 and recombined into the R. meliloti exo megaplasmid in the dctABD region. The resultant strain showed constitutive dctA-specific mRNA synthesis which was about 5-fold higher than that found in fully induced wild-type cells. Uptake assays showed that [14C]succinate transport by the trpPO-dctA fusion strain was constitutive, and the transport rate was the same as that of induced control cells. Acetylene reduction assays indicated a significantly higher rate of nitrogen fixation in plants inoculated with the trpPO-dctA fusion strain compared with the control. Despite this apparent increase, the plants had the same top dry weights as those inoculated with control cells. Key words: acetylene reduction, genetic engineering, nodule, plasmid stability, promoter.

Nitrogen fixation associated with 'Park' Kentucky bluegrass (Poapratensis L.)

1979 ◽  
Vol 25 (10) ◽  
pp. 1197-1200 ◽  
Author(s):  
R. C. Shearman ◽  
W. L. Pedersen ◽  
R. V. Klucas ◽  
E. J. Kinbacher
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Poa Pratensis ◽  
Kentucky Bluegrass ◽  
Acetylene Reduction Activity ◽  
Controlled Environment ◽  
Nitrogen Accumulation ◽  
Reduction Activity ◽  
Significant Difference ◽  
Reduction Assay

Associative nitrogen fixation in Kentucky bluegrass (Poa pratensis L.) turfs inoculated with five nitrogen-fixing bacterial isolates was evaluated using the acetylene reduction assay and nitrogen accumulation as indicators of fixation. 'Park' and 'Nugget' Kentucky bluegrass turfs were grown in controlled environment chambers and inoculated with Klebsiella pneumoniae (W-2, W-6, and W-14), Erwinia herbicola (W-8), and Enterobacter cloacae (W-11). 'Park' inoculated with K. pneumoniae (W-6) had significant acetylene reduction activity using undisturbed turfs. Other treatments including turfs treated with heat-killed cells had no significant difference in acetylene reduction. In a second study, 'Park' and 'South Dakota Certified' turfs were grown in a greenhouse and inoculated with K. pneumoniae (W-6) and E. herbicola (W-8). 'Park' inoculated with K. pneumoniae (W-6) had increased acetylene reduction activity rates and also a greater nitrogen accumulation in aerial tissues when compared to controls. Acetylene reduction activity was correlated (r = 0.92) to nitrogen accumulation. Other treatments did not effectively increase acetylene reduction activity or nitrogen accumulation.

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