Task Force Report for Implementation of Great Lakes Water Quality
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SECTION II: TASK FORCE REPORT ON FERTILIZER NUTRIENTS AND ANIMAL HUSBANDRY OPERATIONS F.R. Hore A.J. MacLean Engineering Research Service Soil Research Institute Agriculture Canada Agriculture Canada TASK FORCE SUPPORT STAFF: Dick Coote Elsie MacDonald Jim Cooke Randy Wahab Rados Trisic ACKNOWLEDGEMENTS We wish to acknowledge the support, assistance, contributions and co-operation given to the Task Force by Dr. J. S. Clark, Director, Soil Research Institute; Mr. C. G. E. Downing, Director, Engineering Research Service; Cartography Section and Library, Soil Research Institute; other federal and provincial government departments as well as several universities contacted. PART 1. Agricultural Contributions To Nutrient Enrichment Of Waters In Watersheds Of Lake Erie, Lake Ontario And The International Section Of The St. Lawrence River Problems and Research on the Lower Great Lakes Although our primary concern in agriculture is with the use and management of land for crop and animal production, it is appropriate that we appreciate the urgency of restoring and maintaining the quality of the Great Lakes waters as outlined in the Report of the International Joint Commission (1970). Lake Erie has a surface area of 9900 square miles and a volume of 110 cubic miles. Lake Ontario is smaller in area, 7500 square miles, but it is deeper and has a volume of 393 cubic miles. The mean depth of water is only 23 feet in the Western Basin of Lake Erie as compared with 60 feet in the Central Basin, 80 feet in the Eastern Basin, and 280 feet in Lake Ontario. Aside from the presence of toxic chemicals and pathogenic organisms in the waters, the main problem is the growth of algae arising from nutrient enrichment. The decomposition of the algae and of organic wastes depletes the supply of oxygen in the water. Upon arrival of warmer weather in the spring, the warmer upper layer of water (epilimnion) is separated from the colder and heavier zone of deep water (hypolimnion) by a thermocline which may serve as a barrier against mixing of the warm and cold water. Thus, until the thermocline disappears in late autumn, nutrients and pollutants may be concentrated in the epilimnion and atmospheric oxygen may not reach the hypolimnion. An over-enriched lake is eutrophic whereas one with a relatively small supply of nutrients is oligotrophic and one with a medium supply is mesotrophic. The shallow Western Basin of Lake Erie is eutrophic, the Central Basin is primarily mesotrophic-eutrophic, the Eastern Basin is primarily oligotrophic-mesotrophic and Lake Ontario is primarily oligotrophic. II-1 Although any nutrient or growth factor may limit algal production, nitrogen, phosphorus and carbon are most important. Of these nitrogen and phosphorus are the main concern and emphasis has been placed on limiting phosphorus in waters since it is more controllable than nitrogen. Water surfaces receive considerable nitrogen but little phosphorus from precipitation. Some species of blue-green algae can use or fix molecular nitrogen. Furthermore, the well known capacity of soils and sediments to fix phosphorus is an assist in limiting the concentration of soluble phosphorus in waters. The phosphorus in sediment and in solution are in equilibrium, however, and when the concentration in solution is low, phosphorus may be released from the sediments particularly when oxygen is depleted. The low amount of phosphorus in water considered limiting for algal growth (about 0.01 ppm) makes control difficult and indicates the need to restrict phosphorus loads from any source including land. The corresponding limiting level of nitrogen for algal growth is about 0.3 ppm. Data on nitrogen and phosphorus in relation to eutrophication of lakes and flowing waters of many countries have been discussed by Vollenweider (1968). Nutrient control policies have been discussed recently by Prince and Bruce (1972). Goals in the management of water quality of the Great Lakes from the standpoint of social instead of just economic implications have been discussed by Lee (1971). In carrying out its responsibilities in research and in devising means to restore the quality of the Great Lakes, in conjunction with United States agencies, the Canada Centre for Inland Waters has invited considerable university participation as outlined by Bruce and Lee (1971). Within the framework of the International Hydrological Decade, the International Field Year for the Great Lakes, a joint U.S. - Canadian comprehensive study of Lake Ontario is underway (Bolsenga and MacDowall, 1970). The Canadian research effort involves several Canadian Government agencies, the Ontario Water Resources Commission and many Canadian universities. In addition, the biological community as a part of the International Biological Program were invited to conduct their investigations in Lake Ontario. II-2 1.1.1 Chemistry of Lakes Erie and Ontario The major sources of chemical data for the Great Lakes have been summarized by Beeton (1971). Changes in the water chemistry of Lakes Erie and Ontario have been reviewed by Chawla (1971). He cited values of the Pollution Board for soluble phosphates in surface waters of Lake Eric as 51 - 120 µg PO4/L in the Western Basin, 15 - 60 µg PO4/L in the Central Basin and 9 - 30 µg PO4/L in the Eastern Basin, Tabulated data showed a 50 per cent increase in soluble phosphate between 1963-64 and 1967-68. Studies of Shiomi and Chawla (1970) showed an average concentration of soluble phosphate of 24 µg PO4/L in the surface and 33 µg PO4/L in the bottom waters of Lake Ontario. The values for total phosphorus were 73 and 76 µ g PO4/L in the surface and bottom waters, respectively. The authors reported that there did not appear to be any marked build-up of total phosphorus over the year although there was considerable variation in the amounts of soluble phosphate during the same period. In an intensive survey in western Lake Erie, Brydges (1971) found that total phosphorus and total iron concentrations were directly related and he postulated that they were coprecipitated and removed the high load of phosphorus from solution. Since limitation of phosphorus in the Lakes has been adopted as the approach to restricting algal growth and since there has been some debate on the relative role of carbon as a limiting factor, some comment may be in order. Following a comprehensive review of the relationship of carbon to eutrophication, Goldman et al.. (1972) concluded that carbon will rarely if ever be limiting in natural environments. Schindler (1971) found that nitrogen and phosphorus, added to an oligotrophic lake very low in CO2 resulted in production of phytoplankton in a short time and he concluded that carbon is unlikely to be limiting for such production in almost any situation. Brydges (1971) found that chlorophyll a and total phosphorus concentrations in Lake Erie were directly proportional and he suggested that phosphorus was an algal limiting factor in this lake. Participants II-3 in a symposium of the American Society of Limnology and Oceanography agreed that efforts to remove phosphorus from influents to lakes was not a waste of time or money (Likens et al., 1971). Dobson and Gilbertson (1971) reported a marked increase (0.075 mg/L/mo/yr) in the rate of deoxygenation in the bottom waters as a result of phytoplankton production in the epilimnion of the Central Basin of Lake Erie. In intensive surveys of this basin, Burns and Ross (1971) found that a massive algal bloom during the last week of July, 1970, reduced the phosphate concentrations to almost undetectable levels in most of the surface waters. This bloom resulted in a layer of sedimented algae about 2.0 cm thick being laid on the basin floor and was followed by marked oxygen depletion (88 per cent). The phosphorus regeneration rate under oxygenated conditions was 22 µmoles P/m2/day as compared with 245 µmoles/m2/day under anoxic conditions. They concluded that immediate reduction in phosphorus input to Lake Erie was vital. In his review, Chawla (1971) reports major increases in the concentrations of nitrogen compounds in Lake Erie during this century, the most marked being a thirteen fold increase in the concentration of ammonia-nitrogen in the Western Basin from 13 µg/L in 1930 to 170 µg/L at present. There was no such dramatic change in the open water of the Central Basin. The data of Shiomi and Chawla gave annual mean values of 27 and 32 µg NH3-N/L in the surface and bottom waters of Lake Ontario, respectively. The reported amounts of nitrate-nitrogen in Lake Ontario varied widely. Although the results will not be discussed here, the concentrations of several microelements in the waters of these lakes have been measured and are covered in Chawla's review. II-4 1.1.2 Sediments of Lakes Erie and Ontario The nearshore sediments westward from Wellington, Prince Edward county along Lake Ontario and then Lake Erie to Mohawk Point have been surveyed (Rukavina and St. Jacques, 1971). Lee and Beaulieu (1971) have provided a map of water use of the Great Lakes Basin. They attribute to agriculture 51.7 per cent of the shoreline land use along Lake Ontario on the Canadian side. The corresponding estimate for Lake Erie was 23.6 per cent. Coakley (1970) used textural and mineralogical characteristics and other techniques to study sands in the nearshore zone of Lake Ontario between Burlington and Toronto. The mineralogical data support the suggestion that most of the material was derived locally from bank erosion or stream discharge. Thomas et al. (1972) studied the distribution and composition of the surficial sediments of Lake Ontario and estimated that 55 per cent of the detrital material was derived from the drainage basin with the remaining 45 per cent being the result of shoreline and lake bottom erosional processes.