Browsing by Subject "nitrates"

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    Effects of Enrichment on Lake Superior Periphyton
    (Water Resources Research Center, University of Minnesota, 1973-05) Krogstad, B.O.; Nelson, R.R.; Odlaug, T.O.; Olson, T.A.; Ruschmeyer, O.R.
    The primary objective of this research as carried out in the summer and fall of 1969 and 1970 was to determine the possible changes which would take place in Lake Superior periphvton when polluting or enriching substances were added to the lake Hater. To this end, two natural rock basins were constructed at the lakeside along the north shore at Castle Danger, Minnesota for the purpose of exposing naturcll1y grown and regrowth periphyton to higher-than-normal levels of phosphate and nitrate. At weekly intervals, samples were collected and productivity was measured by enumeration of organisms, chlorophyll analysis, and weight, dry and organic. Lake Superior periphyton responds dramatical1 y to increased additions of phosphorus and nitrogen. If the near-shore area of Lake Superior ever received nutrients, such as those added to the experimental test pool at Castle Danger, a drastic change in the Lake.'s biota could occur. For example, as enrichment increased, the predominant clean-water diatom forms could eventually be replaced by the more tolerant green or blue-green algae. In addition, the very composition of the macrobenthic forms found in Lake Superior could be altered as a result of their dependence on the periphyton, which, as primary producers, form the first link in the food chain. Likewise, certain fish which depend on benthic organisms for their food may be adversely affected as an indirect result of a changing periphyton community. Having established that enrichment of Lake Superior water will drnmatically change the normal periphyton growth, another baseline has been established for future reference in the event that phosphorus and nitrogen rich wastes should be added to the 1ake. If certain types of algae appear as replacements of the normal flora now characterizing the periphyton and the productivity increases, one will have a means [or assessing the possible changes taking place in the water quality of Lake Superior.
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    Maximum Application Rates for Land Treatment of Septage
    (Water Resources Research Center, University of Minnesota, 1983-05) Anderson, James L.; Clanton, C.J.; Hansel, M.J.; Machmeier, R.E.
    During 1980, septage was applied in rates of 1120 and 1500 kg of nitrogen per hectare to three different soil textures in an attempt to determine maximum loading rates. These rates resulted in increased concentrations of nitrates in the soil water for a Hubbard loamy Sanci, Waukegan silt loam and Lester clay loam, indicating that the application rates exceeded the maximum rate that the soils could treat. The first year's results indicate that soil type, application rates and soil depth resulted in no significant difference in total Kjeldahl nitrogen, ammonia, fecal streptococcus and fecal coliforms in the soil water samples. Nitrate concentrations, however, were significantly different between the soils, application rates and soil depths. For the Hubbard loamy sand, rainfall had a larger effect on nitrate concentrations and movement within the soil profile than for the Waukegan silt loam or Lester clay 1oam. 0n the Waukegan silt loam and Lester clay loam there was relatively little change in the nitrate concentration in the soil profile during the period when septage was applied twice a week. After the design loading had been applied to the soil and no further applications made, a sharp increase in nitrate concentrations was observed in the soil profile. This probably resulted from changing the anaerobic surface layer to an aerobic condition resulting in nitrification and subsequent movement of nitrates through the profile following a rainfall event. With no additional septage application, the second year's data indicate a significant difference in nitrate-N between soils, application rates, and depths. Generally, the nitrate concentrations in the Hubbard loamy sand and Waukegan silt loam were less than the first year, but the concentrations in the Lester clay loam were higher than the first year. This indicates that nitrification and nitrate movement in the Lester clay loam are slower than the other two soils. Application resulted in a significant increase in the concentration of soil water calcium, magnesium, sodium and potassium during the first year of the study. However, there was no increase in the phosphorus content of the soil water.
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    Response of Nearshore Periphyton in Western Lake Superior to Thermal Additions
    (Water Resources Research Center, University of Minnesota, 1974-10) Drown, D.B.; Odlaug, T.O.; Olson, T.A.
    The intent of this research was to ascertain what effects a temperature increase in the order of 10 degrees to 12 degrees C would have on the near-shore periphyton assemblage of Western Lake Superior. To this end a field station, complete with holding tanks and a hot water source, was constructed on a rock ledge of the Lake Superior shore near Castle Danger, Minnesota. During the summer and fall of 1971 and 1972 periphyton covered rocks from the local area of the lake were placed in the experimental holding tanks where they were exposed to a continuous flow of lake water. In addition, denuded rocks were included as part of a regrowth study. One system provided a flow-through of unheated lake water while in the other the temperature was raised above ambient. Growth patterns were followed under both sets of conditions. Periphyton samples were collected on a weekly basis from the ambient control and heated water tanks and were analyzed for photosynthetic pigment concentration, dray and organic weight and total cell count. A quantitative and qualitative examination of the phyletic distribution of algae from the two systems was emphasized. Some of the more important findings and conclusions were as follows: 1. Diatoms were found to be the most prevalent algal type in both heated and cold water tanks. 2. Normal populations of Lake Superior periphytic diatoms (control), in terms of percent composition of the entire assemblage, were not greatly altered by the temperature increases used during the course of this study. 3. Three of the most common algal genera; Synedra, Navicula, and Achnanthes, showed essentially no difference in maximum growth levels attained in cold or heated water other than the fact that, in heated regrowth samples, peak concentrations were reached in a shorter period of time. 4. Several of the periphytic diatoms common to Lake Superior would continue to survive at temperatures well in excess of normal seasonal maxim. 5. Lake Superior contains genera of non-filamentous green algae which have species capable of adapting to extremely high ambient water temperatures. 6. The warm water system was more favorable to green filamentous algae, such as Mougeotia and Zygnema, than was the cold water system. 7. A prevalent green alga found in Lake Superior, Ulothrix zonata, was inhibited by the warmer water conditions. 8. In general, green algae common to Lake Superior are favored by temperatures in excess of those normally found in the lake. 9. Under conditions of these experiments blue-green algae did not increase as a result of thermal addition. 10. Analysis of pheo-pigments indicated that a substantial amount of “apparent” chlorophyll a was actually pheophytin a, a degradation product. Hence, the pheophytin analysis is important to any study dealing with the chlorophyll content of periphyton. 11. Concentrations of pheo-pigments were higher in the cold water tank than in the warm water system. 12. Supplementary observations have suggested that a separate invertebrate community occupied each of the tanks. While the above findings and conclusions indicate that a great deal more needs to be learned of the effects of thermal additions on Lake Superior, this study has pointed out that, if near-shore areas of the lake were warmed to the extent that could occur as the result of a thermal-electric generating station discharge, changes in the phyletic composition of the local periphyton community could be expected. The very nature of a change from diatoms to greens could have serious repercussions on benthic grazers and indeed the entire foodweb of the affected area.