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Water Chemistry of Ravenswood Pond

Jon Anderson and Laura Ediger | Biology 345 | December 12, 1998

Introduction | Methods | Results | Discussion | Figures | Tables


INTRODUCTION

The primary purpose of this study was to assess the condition of Ravenswood Pond using water chemistry in order to determine management priorities for Ravenswood Pond. This study is a part of the Calvin Environmental Assessment Program (CEAP). The ultimate goal of this study is to provide management suggestions to the administration of Calvin College as to the best methods to sustain a healthy pond. While studies have also been completed on North Pond and President's Pond, Ravenswood Pond is a particular matter of concern due to its trend of large fluctuations and general instability. This is supported by previous studies, including that completed by Stephanie Swart during the summer of 1998, and was further evidenced by the significant fish kill that occurred on August 31, 1998. It also requires attention because of its location in the drainage basin for much of the East Grand Rapids area. Ravenswood Pond lies in the northwest region of Calvin College's campus. It is west of the East Beltline and borders the south side of Lake Avenue. It is the larger and more westerly of the two ponds in that area.

A secondary purpose of this study was to observe seasonal changes in the water chemistry of Ravenswood Pond. The time frame of this study begins with the end of the summer and continues through the course of the fall. The climate changes experienced over this period are temperature changes, length of day changes, and changes in the amount of precipitation. This study observes how these factors affect the pond.

The water chemistry in this study tests the following parameters: (1) turbidity, (2) dissolved oxygen, (3) temperature, (4) pH, (5) alkalinity, (6) hardness, (7) chloride levels, (8) ammonia levels, (9) nitrate levels, and (10) phosphorus levels. These parameters were used to quantitatively assess the status of Ravenswood Pond and to identify particular characteristics that would benefit from appropriate management strategies.

METHODS

Sampling

The samples taken from Ravenswood Pond were collected with a Lamotte water sampler (mfd. by Lamotte Chemical) and placed into plastic bags (Nasco Whirl-Paks). Water samples were collected from three different sites, as depicted in Figure 1, with the aid of a canoe. Site 1 was selected due to its close proximity to the input source of Ravenswood Pond. Site 2 was selected because it is away from the primary flow of water, which is from the input to the output of the pond. This site could possibly be a resting-place for solvents. Site 3 was selected because of its location near the output flow of the pond. Water samples were collected from two depths: (1) 30 cm below the surface of the water and (2) 15 cm above the bottom of the pond. After pH testing, these samples were then transported to the lab for further analysis.

Field Tests

There were three tests that we performed in the field: (1) turbidity, (2) dissolved oxygen and temperature, and (3) pH. The first field test that was performed at the three sites was a test of turbidity. Turbidity is the measure of the transparency of the water. The turbidity of the pond was measured with a Secchi disk on a rope, quantified with a yardstick, and recorded as Secchi depth in centimeters.

The second field test was the measurement of dissolved oxygen levels and temperature. A YSI 55 dissolved oxygen meter (mfd. by YSI Inc.) was used to assess the amounts of dissolved oxygen and temperature of the pond. The measurements were taken from each of the sites at the surface (10 cm. depth) and then at increments of half a meter up to 1.5 meter depths. The final field test that was performed was for pH. This was accomplished by the use of pH paper. The pH test was performed on the water samples immediately after the filling of the sample bags.

Laboratory Tests

The samples collected in the field were transported to the lab in order to be tested for six other components. The samples were tested for alkalinity (CaCO3), hardness (calcium and magnesium), chloride levels, ammonia levels, nitrate levels, and phosphorus levels. Hach kits were used to perform these tests. Each specific test has an appropriate box that contains all the necessary equipment and instructions to perform each individual test, and all of the analyses were performed according to the specific protocols. The necessary components for the test are pre-measured for simplified, consistent use. Titrations were completed with a Digital Titrator 16900, also manufactured by Hach. A full list of specific Hach test kits used in this study can be found at the end of this report. Tests for ammonia, nitrates, and phosphorus were performed within a few hours of collection time in order to certify the accuracy of the results. The other tests were completed at a later date (usually 1-2 days afterwards), and the samples were meanwhile refrigerated.

These samplings were completed on four different dates: October 1, October 22, November 3, and November 19 of 1998. Full chemical analyses were performed on each of these samples, but some results from the occasion of November 3 were discarded due to suspected contamination. This range included nearly two full months of unseasonably warm fall weather with a rather large amount of rainfall in October.

RESULTS

Dissolved oxygen measurements compiled from Ravenswood Pond were extremely stratified by depth at the beginning of the sampled time frame (Figure 2). These results are displayed as an average of the measurements from the three sampling sites. The distinction gradually decreased, and by the end of the study, the mg/L of dissolved oxygen was nearly identical at every depth. As shown in Figure 3, the water in the uppermost layer of the pond was supersaturated in early October, while the other layers were relatively unsaturated. As the season progressed, all levels proceeded nearer the saturation point and the pond approached its maximum load of dissolved oxygen.

Another change in the character of the pond occurred in the degree of turbidity. The water became clearer and Secchi depth steadily increased, as shown in comparison with the seasonal temperature drop in Figure 4. Temperature readings showed very little stratification in the pond.

Many of the analyses performed yielded unremarkable results. The pH tests completed in the field produced consistent results of a pH very close to 6.0. Assessment of the amounts of other dissolved solutes - CaCO3, calcium, magnesium, ammonia, phosphorus, and nitrates - did not follow discernible patterns over the season (see Table 1). Calcium increased notably by the time of the last testing, and chloride levels declined throughout. There were no nitrates detected in any of the samplings, and phosphorus was detected only in a very slight quantity at the last sampling date.

DISCUSSION

Throughout the time in which our water chemistry analysis was performed on Ravenswood Pond, there are no strong indications of a badly dysfunctional ecosystem. Dissolved oxygen levels were healthily near the point of saturation. As the fall progressed, the entire pond neared its maximum load as each layer became virtually saturated. Never did the levels of dissolved oxygen drop below 5 ppm (comparable to our mg/L), which is the level necessary to sustain warm-water fish (Cole 1983). There were seemingly few residual effects from the August fish kill, at which time dissolved oxygen levels dropped, at one point, to below 1 mg/L (Swart 1998 (report)). The progression from a variance of dissolved oxygen levels to a homogenous composition was perhaps caused by a variety of factors. With the drop in temperature came an increase in brisk winds, which thoroughly mixed the water. Another explanation for the increase in dissolved oxygen, particularly in the lower portion of the pond, is that levels of decomposition (a process which uses oxygen) subsided as populations of decomposers were killed off or at least slowed by the dropping temperature.

The decrease in turbidity is also a natural event for the fall cooling, as the biotic populations of the pond are reduced in population and productivity from the summer highs. The numbers of phytoplankton in Ravenswood (Laughlin & Mulder 1998) decreased in response to the cold, whether they died off or simply became encysted in preparation for a winter-adapted stage of their life cycle (Van Dragt 1998). Either way, their absence from the upper depths of the pond directly influenced the increase in Secchi depth that was evidenced by our study.

It is difficult to make a qualitative assessment of Ravenswood Pond from the specific chemical analysis of dissolved solutes, as there is little definitive literature on the subject. It is however possible to identify trends, make comparisons with other ponds, and attempt to trace the sources of some of these nutrients. Alkalinity was found at relatively high levels in our study, at least in comparison with North Pond. This correlates well with our consistent pH reading of around 6.0, as alkalinity in a pond has the capacity to neutralize strong acids (Wetzel & Likens 1991) and thus function as a buffer. North Pond exhibited a much more variable pH than did Ravenswood, and this is probably a direct effect of their low alkalinity (Hager & VandeGriend 1998).

One mystery that merits further study is the complete absence of phosphorus in the first three samplings of Ravenswood Pond. It most likely is caused by the rapid uptake of phosphorus by the large algal populations that reside there. The fact that a minute amount of phosphorus was detected at the time of the last sampling may be a result of the decrease in those populations. The highest level was located in the surface sampling at Site 1, which is a good indication of the high levels of phosphorus being channeled into Ravenswood through that input site (Lester & Weemhoff 1998).

Ammonia levels were consistently in a satisfactory range. A certain amount is necessary, as it is an important source of nitrogen for bacteria, algae, and larger plants (Wetzel & Likens 1991), but a high amount of this nutrient (over 2.5 ppm) is detrimental to aquatic organisms (Welch 1952), and is also an indication of severe population reductions (Swart 1998). Chloride levels were quite variable, but anomalous results can be traced to the effect of precipitation. The highest reading was obtained on 10/1/98, the day after a relatively high rainfall (12.2 mm). All other samplings occurred without this effect. Calcium chloride is applied to the roadways in winter and settles into the ground nearby to be washed away during precipitation events (Swart 1998), which explains the higher level of chloride in the ponds immediately after a rainfall.

In conclusion, it is helpful to understand that this study added another layer of data to an existent body of data regarding this pond. Hopefully these results will be helpful in considering the management suggestions which have been made. The instability which has been exhibited by this pond would likely benefit from appropriate management strategies.

Hach Kits

Alkalinity 10-4000 mg/L. Model AL-DT.

Ammonia, Mid-range. Model NI-8.

Chloride 10-8000 mg/L. Model CD-DT.

Hardness, Total and Calcium 10-4000 mg/L. Model HAC-DT.

Nitrates 0-50 mg/L. Model NI-11.

Phosphate, Ortho 0-50 mg/L. Model PO-19.

Literature Cited

Brower, James E. and Jerrold H. Zar, Carl N. Von Ende. 1998. Field and Laboratory Methods for General Ecology. 4th edition. WCB/McGraw-Hill, Boston.

Cole, Gerald A. 1983. Textbook of Limnology. 3rd edition. The C.V. Mosby Company, St. Louis.

Hager, Rebecca and Andrew Vandegriend. 1998. Personal communication.

Laughlin, Daniel and Amanda Mulder. 1998. Personal communication. Lester,

Matthew and Ryan Weemhoff. 1998. Personal communication.

Swart, Stephanie. 1998. Personal communication.

Swart, Stephanie. 1998. Plankton Community Succession and Water Quality in Shallow Eutrophic Ponds. Unpublished report.

VanDragt, Randy. 1998. Personal communication.

Welch, Paul S. 1952. Limnology. 2nd edition. McGraw-Hill Book Company, Inc., New York.

Wetzel, Robert G. and Gene E. Likens. 1991. Limnological Analyses. 2nd edition. Springer- Verlag, Inc., New York.


FIGURES

Figure 1 not available

Figure 2

 

Figure 3

 

TABLE

Table 1. Results from chemical analysis of Ravenswood Pond, Calvin College, at various sites and times during Fall 1998.

  AVERAGES **********  *******  ********                         
  10/1/98 10/22/98 11/3/98 11/9/98 10/1/98     10/22/98     11/3/98     11/9/98    
          Site 1 Site 2 Site 3 Site 1 Site 2 Site 3 Site 1 Site 2 Site 3 Site 1 Site 2 Site 3
Depth 142.33 148.67   146.00 151 145 131 159 158 129       173 160 105
Secchi depth 31.33 45.17   66.33 30 30 34 46 45.5 44       62 67 70
Dissolved oxygen:                                
0.1 m   10.44 9.45 11.48       10.65 10.42 10.25 9.3 9.47 9.57 11.76 11.42 11.26
0.5 m 12.22 10.30 9.35 11.42 12 12 12.67 10.5 10.24 10.17 9.31 9.44 9.3 11.6 11.39 11.27
1.0 m 7.91 9.97 9.31 11.44 7.61 7.61 8.51 10.11 10.32 9.49 9.37 9.22 9.33 11.56 11.39 11.38
1.5 m 5.23 7.54 7.87 11.39 4.75 4.75 6.2 8.69 8.05 5.88 6.47 8.52 8.62 11.52 11.39 11.25
Temperature:                                
0.1 m  /font> 12.03 10.47 6.47       12.1 11.9 12.1 10.6 10.4 10.4 6.6 6.4 6.4
0.5 m 18.70 11.63 10.47 6.43 18.4 18.4 19.3 11.5 11.3 12.1 10.6 10.4 10.4 6.5 6.4 6.4
1.0 m 17.90 11.03 10.37 6.40 17.8 17.8 18.1 10.8 11.2 11.1 10.4 10.3 10.4 6.4 6.4 6.4
1.5 m 17.83 10.77 10.27 6.37 17.8 17.8 17.9 10.7 10.7 10.9 10.4 10 10.4 6.4 6.4 6.3
pH (s) 7.00 6.00   6.00 7 7.5 6.5 6 6 6       6 6 6
pH (b) 6.00 6.00   6.00 6 6 6 6 6 6       6 6 6
alkalinity [CaCo3]                                
surface: phenol 0.00 0.00   0.00 0 0 0 0 0 0       0 0 0
green-methyl red 116.67 103.33   112.33 120 120 110 106 104 100       118 95 124
pH 4.92 5.00     4.9 4.9 4.95 5 5 5            
bottom: phenol 0.00 0.00   0.00 0 0 0 0 0 0       0 0 0
green-methyl red 110.00 98.67   126.67 110 110 110 94 96 106       130 124 126
pH 4.95 5.00     4.95 4.95 4.95 5 5 5            
hardness:                                
calcium (s) 78.67 72.00   88.00 80 80 76 70 76 70       82 92 90
magnesium (s) 63.00 56.00   74.00 55 55 79 60 58 50       76 78 68
total hardness 141.67 128.00   162.00 135 135 155 130 134 120       158 170 158
calcium (b) 73.33 73.33   101.33 74 74 72 70 74 76       102 102 100
magnesium (b) 96.67 58.67   56.67 101 101 88 62 56 58       52 60 58
total hardness 170.00 132.00   158.00 175 175 160 132 130 134       154 162 158
chloride (s) 60.00 59.33   35.67 55 55 70 64 58 56       38 35 34
chloride (b) 76.00 58.67   34.00 80 80 68 60 54 62       36 36 30
ammonia (s) 0.40 0.48 0.48 0.64 0.36 0.48 0.36 0.48 0.48 0.48 0.48 0.48 0.48 0.6 0.72 0.6
ammonia (b) 0.36 0.52 0.52 0.76 0.36 0.36 0.36 0.36 0.72 0.48 0.48 0.6 0.48 0.84 0.72 0.72
phosphorus (s) 0.00 0.00 0.00 0.11 0 0 0 0 0 0 0 0 0 0.16 0.08 0.08
phosphorus (b) 0.00 0.00 0.00 0.08 0 0 0 0 0 0 0 0 0 0.08 0.08 0.08
nitrates (s) 0.00 0.00 0.00 0.00 0 0 0 0 0 0 0 0 0 0 0 0
nitrates (b) 0.00 0.00 0.00 0.00 0 0 0 0 0 0 0 0 0 0 0 0
                                 
  10/1 10/22 11/3 11/19                        
CaCO3 113.33 101.00   119.50                        
calcium 76.00 72.67   94.67                        
magnesium 79.83 57.33   65.33                        
total hardness 155.83 130.00   160.00                        
chloride 68.00 59.00   34.83                        
ammonia 0.38 0.50 0.50 0.70                        
phosphorus 0.00 0.00 0.00 0.09                        
nitrates 0.00 0.00 0.00 0.00