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5 In-Lake Processes: Dissolved Oxygen and Nutrients
Pages 153-188

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From page 153... ... Eutrophication can also lead to anoxia. Decreases in Dissolved Oxygen Elevated production of phytoplankton biomass due to increased nutrient loading can often lead to depletion of oxygen in the bottom waters of a lake, which occurs when organic matter produced by nutrient-driven phytoplankton sinks into the bottom layers and is decomposed by bacteria that consume oxygen. Read the entire page →
From page 154... ... ; obviously, the exact concentration below which dissolved oxygen has negative effects varies depending on the organism of interest, the environment, and the duration of exposure (e.g., Hrycik et al., 2017; Tellier et al., 2022) Read the entire page →
From page 155... ... Finally, the committee performed a Mann-Kendall test of trends in the monthly-averaged dissolved oxygen data in bottom waters at all four sites. To conduct these analyses, it was necessary to standardize the profile data with respect to sample collection methodologies, sample depth, and temporal frequency because the available data were quite heterogeneous with regard to these dimensions. Read the entire page →
From page 156... ... Higher oxygen concentrations are observed throughout the water column during the winter and spring, and lower concentrations are observed during the summer and fall, when CDA Lake is warmer at the surface. For example, both C1 and C4 dissolved oxygen concentrations averaged 11.2 mg/L from December to May and 8.7 mg/L from July to November. Read the entire page →
From page 157... ... SOURCE: Data plotted by the committee, courtesy of USGS and IDEQ. dissolved oxygen concentrations only averaged 1.7 mg/L, at depths of 8–11 m, whereas dissolved oxygen concentrations averaged 8.6 mg/L in the upper 5 m of the water column during this same time. Read the entire page →
From page 158... ... . Additionally, the average dissolved oxygen concentration in the surface and bottom waters of station C4 were similar during the months of December through August, and peaked at about 11.6 mg/L from January through April (Figure 5-5) Read the entire page →
From page 159... ... at the C1 Sampling Station Cl Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 1991 11.34 11.70 12.00 11.07 9.61 9.52 9.01 8.06 7.47 7.57 10.81 1992 11.89 10.98 10.51 9.74 9.62 8.49 8.06 8.19 7.01 7.34 10.25 1993 1994 1995 7.29 8.49 8.46 1996 8.82 7.67 8.22 7.86 1997 11.21 10.15 9.06 8.43 7.94 1998 9.05 8.36 7.20 6.65 1999 8.35 8.36 7.55 6.84 2000 8.93 8.61 6.90 6.74 2001 9.38 8.67 7.05 6.73 2002 7.83 7.41 6.73 2003 6.98 9.77 2004 11.28 11.33 10.48 9.96 8.95 8.43 6.73 9.15 2005 9.11 12.09 10.74 9.63 9.14 8.21 7.83 9.83 2006 11.57 12.20 11.31 9.99 9.52 8.70 2007 9.58 9.07 8.04 7.83 7.23 9.47 2008 12.12 11.99 11.21 10.06 9.26 7.34 7.14 2009 11.61 10.21 9.45 7.89 7.69 2010 10.87 11.13 10.59 9.45 8.19 7.47 6.48 9.46 2011 10.83 11.69 10.96 9.77 9.36 9.06 7.41 10.30 2012 10.56 12.89 11.71 10.31 9.11 8.65 7.68 6.86 6.80 2013 12.25 10.91 9.94 9.04 7.82 7.42 9.99 2014 11.36 12.57 10.61 9.63 9.18 8.07 7.71 10.10 2015 11.47 11.87 10.79 9.80 9.28 8.52 7.82 7.14 7.14 2016 11.92 10.75 9.84 9.19 8.59 8.06 7.12 7.08 2017 12.11 11.48 10.59 9.70 9.42 9.02 8.20 7.67 10.20 2018 11.80 12.48 12.03 11.39 10.73 9.99 9.25 8.97 8.33 7.80 2019 12.50 12.52 11.13 10.63 9.68 9.21 8.04 7.88 9.68 2020 11.96 11.71 10.79 10.11 9.20 8.63 6.82 9.69 2021 11.0 11.1 12.0 11.9 Monthly mean 10.8 11.3 11.7 11.9 10.8 9.9 9.1 8.4 7.8 7.3 7.7 9.9 Monthly SD 1.2 0.3 0.6 0.6 0.5 0.4 0.5 0.6 0.6 0.5 1.2 0.4 Note: Red shading denotes less favorable conditions (e.g., low dissolved oxygen) , while blue shading denotes more favorable conditions (e.g., high dissolved oxygen) Read the entire page →
From page 160... ... at the C4 Sampling Station C4 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 1991 10.85 11.21 11.45 11.45 10.05 9.53 9.27 8.70 8.11 7.95 10.98 1992 12.12 11.10 11.11 10.08 9.69 8.82 8.27 8.05 7.28 6.28 10.71 1993 1994 1995 7.54 8.36 8.05 1996 9.12 9.05 8.44 8.17 1997 10.98 10.40 9.42 8.83 8.18 1998 9.01 8.82 7.73 6.76 1999 8.65 8.63 7.90 6.84 2000 9.07 7.29 6.41 2001 8.95 7.65 7.21 7.22 2002 7.98 7.61 8.96 2003 7.16 10.15 2004 11.24 10.83 9.75 9.64 8.98 8.20 6.69 8.99 2005 9.66 11.42 10.69 9.45 9.33 8.25 7.75 10.13 2006 11.35 12.05 11.16 10.04 9.46 9.05 2007 9.99 9.38 8.06 7.36 9.59 2008 11.66 10.94 10.40 9.62 7.53 7.42 2009 11.05 10.39 9.44 8.86 7.18 2010 10.67 11.42 10.61 9.69 8.26 7.77 6.71 9.83 2011 10.86 11.08 10.44 10.26 9.40 8.04 10.62 2012 10.69 11.91 11.55 9.41 8.76 7.68 7.19 6.79 2013 11.90 10.64 10.00 8.88 8.13 7.81 10.20 2014 11.83 11.70 11.07 10.06 9.47 8.73 8.12 10.13 2015 11.72 11.67 10.97 10.06 9.19 8.88 8.06 7.25 7.09 2016 11.60 10.71 9.63 9.27 8.75 8.11 7.15 7.33 2017 11.30 10.92 10.82 9.05 9.50 9.24 8.61 7.85 10.40 2018 11.80 12.09 11.87 11.32 10.64 9.99 9.49 9.27 8.36 7.93 10.37 2019 12.59 12.08 11.00 10.34 9.71 9.47 8.47 7.68 10.23 2020 12.00 11.51 10.87 10.08 9.22 8.73 7.32 6.67 9.74 11.19 2021 11.43 11.98 11.99 Monthly mean 11.0 11.5 11.6 11.5 10.08 9.9 9.3 8.6 8.0 7.5 7.6 10.2 Monthly SD 1.0 0.4 0.6 0.4 0.4 0.4 0.5 0.6 0.6 0.6 1.1 0.6 Note: Red shading denotes less favorable conditions (e.g., low dissolved oxygen) , while blue shading denotes more favorable conditions (e.g., high dissolved oxygen) Read the entire page →
From page 161... ... at the C5 Sampling Stationa C5 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 1991 11.2 10.7 10.1 9.6 8.3 6.9 5.2 3.8 9.7 11.2 1992 11.0 10.4 10.0 9.7 8.3 6.0 4.8 6.6 4.7 9.5 11.4 1993 1994 1995 5.1 4.8 9.3 1996 7.2 6.0 4.8 4.8 1997 10.4 8.4 6.7 6.6 9.1 1998 7.0 6.0 3.6 3.2 1999 2000 2001 2002 2003 5.9 10.4 2004 10.6 8.9 9.9 6.3 4.8 4.3 10.2 2005 10.7 9.3 8.7 7.0 4.6 7.9 9.6 2006 11.0 10.7 9.9 8.2 7.0 4.8 2007 7.5 6.6 3.8 4.2 11.1 2008 10.8 9.9 10.4 9.0 7.8 6.3 5.8 10.0 2009 11.1 10.7 9.7 7.9 5.8 5.2 10.3 2010 11.3 11.1 10.4 8.6 6.8 6.4 5.2 10.1 2011 10.9 10.6 8.9 8.1 5.8 5.4 10.1 2012 11.9 10.6 9.6 8.2 6.1 5.1 6.3 10.7 2013 10.7 11.3 10.6 8.6 6.8 5.8 8.1 10.9 2014 12.9 11.6 11.6 9.6 9.4 7.4 6.2 6.2 10.9 2015 12.8 12.4 10.9 9.3 7.4 6.4 5.8 5.4 11.0 2016 11.5 10.5 8.6 8.5 6.2 5.2 6.5 11.3 2017 11.0 11.1 10.5 9.1 7.2 5.8 7.7 11.5 2018 12.5 12.9 11.3 11.1 10.6 8.6 6.6 5.9 7.7 8.9 2019 11.9 12.3 11.0 9.7 8.3 6.7 5.7 6.6 11.7 11.3 2020 12.8 11.2 10.8 9.5 6.9 5.5 5.9 11.4 12.6 2021 Monthly mean 11.9 11.8 11.6 10.9 10.5 9.4 7.9 6.1 5.4 6.2 10.6 10.8 Monthly SD 0.9 1.0 0.9 0.6 0.7 0.9 1.0 1.0 0.8 1.7 0.9 0.9 Note: Red shading denotes less favorable conditions (e.g., low dissolved oxygen) , while blue shading denotes more favorable conditions (e.g., high dissolved oxygen) Read the entire page →
From page 162... ... at the C6 Sampling Station C6 Jan Feb Mar April May June July Aug Sept Oct Nov Dec 1991 9.1 9.5 8.2 5.1 1.7 1.3 7.1 9.8 1992 11.2 9.1 5.3 0.4 1.5 8.1 12.2 13.6 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 8.1 2004 10.0 9.4 6.5 3.7 0.4 8.5 10.6 2005 11.2 9.5 6.7 0.5 2.8 8.4 2006 10.7 8.1 3.2 0.3 2007 6.0 1.4 0.18 1.7 12.4 2008 11.0 10.2 9.5 9.9 5.7 0.36 9.2 9.4 2009 10.9 10.2 7.3 3.5 0.18 8.4 11.3 2010 10.6 9.8 2.8 0.20 3.4 10.7 2011 11.1 8.2 3.68 0.7 7.8 10.8 2012 12.0 10.7 9.4 4.9 0.24 1.5 10.0 11.2 2013 11.0 10.8 7.4 1.6 0.07 0.3 10.5 11.9 2014 12.9 12.7 11.6 9.5 6.1 0.26 2.1 8.8 12.0 2015 12.7 12.0 8.0 2.9 0.2 0.08 8.1 8.9 11.3 2016 12.5 10.5 6.3 0.6 0.00 3.2 9.5 11.8 2017 11.7 11.4 8.5 3.2 0.09 1.3 10.4 12.0 2018 12.8 13.0 12.2 10.3 8.2 0.7 0.04 2.7 10.1 10.8 2019 11.5 10.3 6.6 1.8 0.00 1.3 9.7 12.2 2020 11.6 10.2 5.5 0.48 2.4 9.6 12.3 2021 Mean 12.7 12.2 11.2 10.2 7.6 3.1 0.66 2.7 9.2 11.5 11.0 SD 0.0 0.8 1.0 1.0 1.9 2.3 1.0 2.4 1.2 0.9 1.5 Note: Red shading denotes less favorable conditions (e.g., low dissolved oxygen [DO] Read the entire page →
From page 163... ... This site also has the most severe seasonal dissolved oxygen depletion in its bottom waters, with concentrations routinely averaging well below 1 mg/L at 8–11 m depth during the month of August, and concentrations only averaging 2.9 mg/L in July and September. During these months, the bottom dissolved oxygen concentrations also averaged 7.0 mg/L lower than the surface concentrations (Figure 5-7) Read the entire page →
From page 164... ... dissolved oxygen concentrations at the C1 vertical profile sampling station. The monthly means are for 1991–2021 data, and the error bars represent ± 1 SD. Read the entire page →
From page 165... ... dissolved oxygen concentrations at the C6 vertical profile sampling station. The error bars in this plot are ± 1 SD. Read the entire page →
From page 166... ... are positive and none are negative.5 Five of those 22 were moderately significant upward trends and none were highly significant. However, when aggregated over the months using the Seasonal Kendall test, both C1 and C4 show highly significant upward trends in dissolved oxygen. Read the entire page →
From page 167... ... The overall result using the Seasonal Kendall test shows a moderately significant upward trend in dissolved oxygen. The downward trends indicated for July and August are important because they come at the time of year with the lowest dissolved oxygen levels. Read the entire page →
From page 168... ... Solid vertical lines mark the start of the calendar year, and the dashed lines separate the year into four quarters. SOURCE: Data plotted by the committee, courtesy of IDEQ and the CDA Tribe. Read the entire page →
From page 169... ... Furthermore, the total phosphorus concentrations in the CDA River observed in 2019 and 2020 were very low when compared to the other years that are also in the lowest third of the records for the past 26 years. Thus, the committee would argue that these two low concentration years are not simply an artifact of these being low flow years. Read the entire page →
From page 170... ... At sites C6 and SJ1 there are no regular seasonal patterns in the total phosphorus concentrations. Figure 5-10 shows a set of plots for the entire total phosphorus record at all five sites, distinguishing between surface water (or photic zone) Read the entire page →
From page 171... ... The red and blue curves are loess smooths of the bottom and surface water datasets, respectively. Note that the vertical axes are identical across all of the panels. Read the entire page →
From page 172... ... . Median values in 2020 are determined using the loess smoothing shown in Figure 5-10. Read the entire page →
From page 173... ... The ability to project future changes in phosphorus inputs and concentrations in the Lake will depend on research aimed at better understanding the causative mechanisms of these recent trends. Future trends in total phosphorus will depend on a combination of factors, including continuing improvements in landscape stability in formerly mined parts of the watershed and in the channel of the CDA River, changes in rain intensity and river discharges, and the implementation of additional phosphorus control measures under the Lake Management Plan. Read the entire page →
From page 174... ... 174 THE FUTURE OF WATER QUALITY IN COEUR D'ALENE LAKE FIGURE 5-11 Continued Read the entire page →
From page 175... ... . FIGURE 5-12 Total nitrogen concentration versus time at five sampling locations: C1, C4, C5, C6, and SJ1, with red symbols representing water samples below 21 meters and blue symbols representing surface water samples. Read the entire page →
From page 176... ... 176 THE FUTURE OF WATER QUALITY IN COEUR D'ALENE LAKE FIGURE 5-12 Continued Read the entire page →
From page 177... ... Gaining a better understanding both of the nitrogen cycle, and of nitrogen trends in the Lake and rivers is an important topic that needs to be included in the research agenda supporting adaptive management of CDA Lake trophic status. IN-LAKE PRODUCTIVITY ANALYSES To complement the preceding analyses of dissolved oxygen and nutrients, the committee analyzed additional measures of lake productivity -- trophic status and chlorophyll a. Read the entire page →
From page 178... ... Thus, average total nitrogen and chlorophyll values are likely overestimates. The committee also compared total nitrogen:total phosphorus (TN:TP) Read the entire page →
From page 179... ... was a moderately significant downward trend. The overall trend as determined by the Seasonal Kendall test was slightly negative, but not even close to being significant. Read the entire page →
From page 180... ... It compared CDA Lake's chlorophyll values relative to its total phosphorus concentrations and compared these to global relationships. If high zinc concentrations in CDA Lake inhibit phytoplankton biomass, then one would expect CDA Lake chlorophyll values to be lower than those observed in other lakes with similar total phosphorus values. Read the entire page →
From page 181... ... That is, C6 also shows a lower chlorophyll concentration given its total phosphorus level relative to the global lake dataset. Thus, this lack of a within-lake, zinc-dependent pattern in the chl–TP relationship is not consistent with the hypothesis that high zinc concentrations inhibit phytoplankton biomass in CDA Lake.6 6 Our conclusion (lack of support for Zn suppression) Read the entire page →
From page 182... ... + b2 · ln(TZn) + e The expectation based on the zinc inhibition scenario is that b1 should be positive (more total phosphorus leads to more chlorophyll) Read the entire page →
From page 183... ... However, from the multiple regression analysis, it is clear overall that zinc inhibition of chlorophyll in the Lake is not consistently detectable in a statistical sense in data from multiple sites across multiple years. Nor is it consistent with the zinc inhibition hypothesis that locations in the Lake with low zinc concentrations also fall below the global chlorophyll–total phosphorus relationship. Read the entire page →
From page 184... ... Given the physiological plausibility of zinc inhibition of phytoplankton growth, continued monitoring and investment in both passive and active adaptive management will be critical tools in the future. CONCLUSIONS AND RECOMMENDATIONS This chapter analyzed water column data from CDA Lake over the past 30 years to reveal trends in dissolved oxygen, nutrients, and lake productivity. Read the entire page →
From page 185... ... According to these widely used metrics of lake trophic status, the Lake can be classified as oligotrophic. Indeed, median values of total phosphorus and chlorophyll are seven times and five times lower, respectively, in CDA Lake than median values in lakes in the National Lakes Assessment. Read the entire page →
From page 186... ... 1994. Abundance of marine resources in relation to dissolved oxygen in Long Island sound. Read the entire page →
From page 187... ... 2012. Estimating risks to aquatic life using quantile regression. Read the entire page →

From page 153...

... Eutrophication can also lead to anoxia. Decreases in Dissolved Oxygen Elevated production of phytoplankton biomass due to increased nutrient loading can often lead to depletion of oxygen in the bottom waters of a lake, which occurs when organic matter produced by nutrient-driven phytoplankton sinks into the bottom layers and is decomposed by bacteria that consume oxygen.

5 In-Lake Processes: Dissolved Oxygen and Nutrients Pages 153-188

5 In-Lake Processes: Dissolved Oxygen and Nutrients
Pages 153-188