摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f73-232

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Lake 227, a small lake with extremely low concentrations of dissolved inorganic carbon, was fertilized with PO4and NO3for 4 years, beginning in 1969. The additions increased natural inputs of phosphorus and nitrogen about five times.Phytoplankton standing crop increased nearly two orders of magnitude, and the Cryptophyceae and Chrysophyceae present in natural lakes of the area were replaced by Chlorophyta and Cyanophyta. The standing crop of phytoplankton per square meter was near the maximum which could theoretically be maintained by surface light, in spite of the low carbon concentrations. Added phosphate and nitrate were rapidly removed by phytoplankton, so that concentrations in the lake remained low.Almost all of the added nutrient was retained by the lake, in spite of relatively fast water renewal times. An average of 80% of the phosphorus income of the lake was sedimented. There was no return of phosphorus from sediments in spite of anoxic conditions in the hypolimnion.Photosynthesizing plankton reduced dissolved inorganic carbon concentrations severely, causing a flux of atmospheric CO2into the lake. From 69 to 95% of the inorganic + particulate carbon supplied to the lake was from the atmosphere. Results demonstrate that low carbon concentrations do not hinder eutrophication if phosphorus and nitrogen supplies are adequate.

ISSN:0706-652X    

DOI:10.1139/f73-233

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A simple, rapid method for determining dissolved inorganic carbon in water is described. A 20-cm3sample of water is drawn into a 50-cm3polypropylene syringe and acidified by injection of 1 cm3of dilute sulphuric acid. Twenty-nine cubic centimeters of helium at atmospheric pressure is injected into the syringe followed by 10 sec of manual agitation to partition CO2between gas and liquid phase. The gas phase containing 60% of CO2from the sample is then analyzed by gas chromatography. This method has been used to determine dissolved inorganic and organic carbon in Canadian Shield waters and to determine total carbonates in sediments.

ISSN:0706-652X    

DOI:10.1139/f73-234

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A computer-based model for determining production by phytoplankton, integrated over depth and over an arbitrary time interval, is described. The solution incorporates light inhibition and uses the actual distribution of surface irradiance for the time interval of interest, since it is not possible to predict the detailed nature of cloudiness. Statistical procedures for estimating the model parameters from experimental data relating the rate of carbon uptake to irradiance are described. The model is applied to data collected from May 27, 1970 through February 3, 1971 from Lake Michigan.Integral primary production was bimodal at inshore and offshore stations with minimum production in midsummer and winter. There was great daily variability of integral production, due solely to variation of light. From this it is inferred that occasional in situ measurements would give a very poor knowledge of true seasonal trends.The model output was verified by performing two in situ experiments. The agreement was better than 95% on both dates. The model makes it possible to estimate integral primary production on a routine basis in large water bodies with well-mixed photic zones.

ISSN:0706-652X    

DOI:10.1139/f73-235

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A new model for computing integral daily phytoplankton primary production is described. The model incorporates vertical variations of algal biomass, complex photosynthesis vs. light responses, nonexponential extinction of light vs. depth, and any distribution of surface light over a day. The basic approach is to combine measured relations for photosynthetic rate vs. light, light vs. depth, and light vs. time in an interpolative scheme rather than attempting to fit equations to the data and using the resulting equations to obtain a mathematical solution. The model is general and should have wide applicability. Model predictions agreed well with in situ measurements of production.

ISSN:0706-652X    

DOI:10.1139/f73-236

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The radon method, used previously in ocean-atmosphere systems, is used here to determine the gas-exchange rate between the atmosphere and lake 227 of the Experimental Lakes Area. Fertilization of the lake with nitrogen and phosphorus caused the carbon dioxide partial pressure in the lake water to drop well below atmospheric levels; hence, in order to better understand the carbon budget of the lake, an estimate of the CO2gas-exchange rate was necessary.To determine gas-exchange rates by measuring radon evasion to the atmosphere the source of radon in the lake water must be dissolved radium. Since the radon concentration in lakes derives not only from the decay of dissolved radium but also from the inflow of radon-rich groundwaters, radium was added to the lake to increase the radon concentration well above this fluctuating background level. Although this procedure was complicated by algal uptake of the radium in the lake (Emerson and Hesslein 1973), we were able to place limits on the gas-exchange rate.Our results indicate that the "stagnant boundary layer" thickness is approximately 300 μ. This value is among the largest observed in natural waters. Using this value and the partial pressure of CO2in the lake water we have calculated an invasion rate of 17 ± 8 mmoles CO2/m2day.

ISSN:0706-652X    

DOI:10.1139/f73-237

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Radium-226 was added to lake 227 of the Experimental Lakes Area in August 1970 so that gas-exchange rates between the atmosphere and the lake could be traced by its gaseous daughter product radon-222. Although we expected the radium to remain in solution it did so for only about 1 month. An investigation to locate the radium after it left solution revealed that it was taken up on the bottom in the littoral zone. Further experiments indicated that it had adsorbed to the algal detrital material on the littoral sediment surface. Seasonal movement of this material could thus be monitored by following the movement of the radium with time.

ISSN:0706-652X    

DOI:10.1139/f73-238

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Values for K, the coefficient of vertical eddy diffusion in the thermocline of lake 227, a small, highly stratified, and artificially eutrophied lake in northwestern Ontario, Canada, are presented. Three methods: the classical temperature method of McEwen, a dye method, and a new method using aRAGAPOS(Radon Gas Point Source), were used. Results ranged from 2 × 10−4 cm2/sec by the Rn method to 34 ×10−4 cm2/sec by temperature method; the dye method resulted in an average value of 12 × 10−4 cm2/sec. The recycling of ΣCO2resulting from particulate degradation below the epilimnion was calculated. The results ranged from 8 to 53% of the net loss of carbon from the empilinion depending on the K value used. Results from the radon method are considered to be more accurate than results from the temperature method.

ISSN:0706-652X    

DOI:10.1139/f73-239

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Standard in situ measurements of phytoplankton production and14C bottle bioassays gave erroneous results when applied to lake 227, a eutrophic softwater lake in the Canadian Shield. Errors were found to be due to diurnal variations in the degree of carbon limitation of phytoplankton, and to invasion of CO2from the atmosphere and hypolimnion.A method based on diurnal measurements of dissolved inorganic carbon, community respiration, and invasion of CO2, using gas chromatography, is described. Production by phytoplankton in lakes fertilized with nitrogen and phosphorus was found to be several times higher than in natural lakes of the area. Net production during summer stratification was found to equal invasion of CO2from the atmosphere.The new technique should have application in other eutrophic low carbon lakes, where14C tracer techniques are encumbered by serious technical complications.

ISSN:0706-652X    

DOI:10.1139/f73-240

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Two new techniques for measuring photosynthesis by benthic algal flora in waters low in dissolved inorganic carbon are described. The first uses gas chromatography to measure changes in DIC in incubation chambers directly. The second is a variation of the usual14C procedure, in which disappearance of14C from the water is measured by liquid scintillation instead of uptake of14C by the algae. This procedure is simpler than measuring the uptake of14C, because digestion and/or combustion of samples is not necessary. Results are compared with the commonly employed14C uptake and O2release techniques.Tests showed that heterogeneity of substrate was the major source of variation in in situ results, being large enough to make interpretation of seasonal effects and other causal factors extremely difficult.Annual production by epilithiphyton in two natural lakes in the Experimental Lakes Area (ELA) was 5.19 g C and 5.18 g C/m2of substrate annually for lakes 239 and 240, respectively. These are the lowest values recorded for freshwater lakes at temperate latitudes.Because DIC and O2concentrations could be measured simultaneously, it was possible to calculate photosynthetic quotients on several dates. These were extremely high, averaging 2.6 for the summer of 1971.

ISSN:0706-652X    

DOI:10.1139/f73-241

出版商:NRC Research Press    

年代:1973

数据来源: NRC