Browsing by Author "Tikkanen, Craig A"

Now showing 1 - 4 of 4
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    An Assessment of Phytoplankton Nutrient Deficiency in Northern Minnesota Acid-Sensitive Lakes
    (University of Minnesota Duluth, 1991) Axler, Richard P; Tikkanen, Craig A; Rose, Charles
    The Northern Lakes and Forests ecoregion of Minnesota contains thousands of lakes, characterized by their sensitivity to acid rain, and their typically low productivity. Four acid- sensitive lakes were studied for 1988-1991 to determine if phytoplankton were deficient in nitrogen, phosphorus, or both N and P, and if nutrient input via atmospheric deposition could increase primary production. The relative accuracy of predictions based on growth response bioassays, physiological assays, and nutrient deficiency indices was also evaluated. Our results show that: (1) N enrichment generally caused a greater biomass response than P, although N+P almost always yielded the greatest effect and co-limitation was likely in two of the lakes; (2) predictions based on DIN:TP ratios generally agreed with the growth bioassays, TN:TP and DIN:SRP were not useful and could be misleading; and (3) atmospheric deposition could satisfy most of the daily algal N demand and increase the fertility of these lakes. These results suggest that although water quality protection based solely upon phosphorus may not protect against this non-point source of nutrients, without these control strategies, P-inputs would be expected to have a disproportionally greater impact on phytoplankton growth.
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    Demonstration of the FIS-C Aqucultural Bioenergetics Model for Estimating Waste Loads and Optimizing Feeding at Two Commercial Rainbow Trout Farms
    (University of Minnesota Duluth, 1995) Axler, Richard P; Schuldt, J; Tikkanen, Craig A; McDonald, Michael E; Henneck, Jerald
    Fish culture has great potential in Minnesota but the potential for water quality impacts has slowed its development. Since 1989 we have been developing an aquacultural effluent model (FIS-C) for assessing the actual and potential impacts of Chinook salmon waste loads. FIS-C is a based on a bioenergetics model where growth = (consumption - waste losses - respiration losses), where waste losses are egestion and excretion, and metabolic costs are incorporated into respiration losses. The model provides a novel way of estimating the magnitude and seasonality of discharges, because it can discriminate among waste fractions, and also has excellent potential for predicting the effects of different waste collection strategies. The model has already proven to be a robust estimator of consumption, when fish growth is known, for a variety of wild species and for net-pen cultured Chinook salmon. Maximum utility for Minnesota's industry requires expanding its library of physiological parameters to other species and culture systems, and then verifying its predictions in the field. Although FIS-C would be applicable to recirculating systems, land-based flow-through facilities, with short detention times and minimal "in-water" transformations such as solubilization, sedimentation, mineralization and nitrification, provide the best opportunity to accurately verify its predictions. The present study developed the model for rainbow trout, an economically important species in Minnesota, assessed its accuracy for two different successful, commercial trout farms, and initiated the development of an extension bulletin for disseminating our results to the industry.
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    Effects of Aquaculture on Mine Pit Lakes near Chisolm, MN: Restoration of Twin City-South pit lake by fallowing and status of Fraser pit lake
    (University of Minnesota Duluth, 1995) Axler, Richard P; Yokom, Shane; Tikkanen, Craig A; Henneck, Jerald; McDonald, Michael E
    Net-pen salmonid aquaculture was carried out from 1988 to 1993 in the Twin City-South mine pit lake on the Mesabi Iron Range in northeastern Minnesota. A water quality controversy enveloped the aquaculture operation from its inception in 1988. In 1992 the Minnesota Pollution Control Agency mandated that all intensive aquaculture operations in the Twin City - South mine pit lake be terminated by July 1993 and that restoration to baseline (i.e. preaquaculture) conditions be demonstrated within three years. This "fallowing" has led to a rapid recovery to near baseline water quality conditions and an oligomesotrophic, i.e. unproductive, status. Water column improvement in regard to phosphorus and hypolimnetic oxygen concentrations has been particularly rapid. Although baseline conditions were not well defined for TC-S, the P budget for the lake in September and November 1994 was typical of reference pit lakes in the area. Oxygen concentrations in near-bottom water remained above 5 mg02/L in November 1994 even without artificial mixing or aeration during the 1994 growing season. Algal growth was low in 1993, as expected due to artificial mixing, and remained low in 1994 without any artificial mixing. Ammonium has been naturally converted to nitrate which is decreasing faster than expected and at a rate similar to its increase during intensive aquaculture. More rapid reductions in water column phosphorus and nitrogen might have been accomplished during the first summer by allowing the lower hypolimnion to become anoxic in order to promote denitrification and minimize sediment resuspension. The natural burial of sedimented aquaculture wastes due to high ambient rates of erosion of inorganic sediment from the basin walls has effectively minimized sediment nutrient transport to the overlying water column. Fallowing for several years appears to be an effective method for lake restoration of these pit lakes. Our data, and our analysis of the NPDES monitoring data, has shown no change in the water quality of Chisholm's drinking water source, the Fraser pit lake, attributable to aquaculture impacts. This, and no apparent change in the water quality of two nearby pit lakes, Grant and Ironworld in recent years, suggests little or no significant off-site migration of aquaculturally impacted water.
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    Limnological Assessment of Mine Pit Lakes for Aquaculture Use
    (University of Minnesota Duluth, 1992) Axler, Richard P; Larsen, Christen; Tikkanen, Craig A; McDonald, Michael E; Host, George E
    This study addresses water quality issues associated with current and future uses of mine pit lakes for intensive aquaculture. In current net pen aquaculture operations (Minnesota Aquafarms, Inc.), metabolic wastes and uneaten food are dispersed into the lakewater. Intensive aquaculture at Twin City-South and Sherman increased levels of phosphorus (P) and nitrogen (N) and reduced dissolved oxygen (DO) in the water column, and increased the deposition of organic matter to the bottom relative to their previous conditions and to unused mine pit lakes. Numerous trophic status indices suggest that TC-S and Sherman have shifted (or are shifting) from an oligotrophic state to a more eutrophic one. However, due to MAPs intensive aeration, and circulation, conditions necessary for algal blooms (typical of eutrophication) have been infrequent, due to light limitation from vertical mixing. Blooms of scum-forming bluegreen algae have never been observed.