Submitted by: CRG
Submitted to: Dave Lasenby
BIOL 305
Submitted on March 1, 2004
1

Seasonal variations can influence the distribution and abundance of organisms in lakes
(Järvinen et al, 2002). The variations are related to abiotic and biotic factors that change during the ice-cover and ice-free seasons (Baehr and Degrandpre, 2002). For example, dissolved oxygen is often limiting in the winter under the ice because it is depleted faster than it can be replaced (Phillips and Fawley, 2002). Ice-cover regulates the amount of light penetration into the lake (Belzile et al., 2001), especially if the ice is cloudy or contains air bubbles or dissolved organic matter (Wetzel, 2001, p. 63). Primary productivity and thus many planktonic communities are subsequently affected (Wetzel,
2001, p. 64). Severely low dissolved oxygen levels can lead to winterkills, a serious phenomenon that can kill fish each year (Phillips and Fawley, 2002; Wetzel, 2001, p. 64).
Oxygen can also be limiting in the hypolimnion during the summer due to high bacterial decomposition rates, predominantly at the sediment/water interface (Wetzel, 2001, p.
155). This in turn affects benthic communities that rely on oxygen availability. Seasonal succession of zooplankton communities are remarkably interesting since they help direct energy from primary producers to higher trophic levels throughout the year (Yoshida et al., 2001). These types of studies can help understand the seasonal changes in lake ecosystems.
The purpose of this experiment was to study the factors that regulate the distribution and abundance of organisms in a lake under ice. The results could then be compared to a similar water body to help understand seasonal variations. It is hypothesized that abiotic and biotic factors in a lake are affected by ice-cover, and that the change in these factors control the distribution and abundance of the organisms. It is also hypothesized that there
2

will be seasonal differences in the distribution and abundance of organisms in relation to these abiotic and biotic factors.
Sample site
The lake studied for this lab was Chemong Lake in Peterborough, Ontario, Canada.
Chemong Lake is a freshwater lake located on limestone bedrock. It was sampled in the morning and afternoon of February 2, 2004. The lake and ice volume were estimated using morphometric data from BIOL 305. Raw morphometry data can be seen in appendix A. Maximum depth for Chemong Lake appears to be close to 7m. Land-use surrounding the lake is mainly residential. The longitude and latitude coordinates for
Chemong Lake are 44 ° 29’30”N and 78 ° 20’W. Figure 1 shows the sampling sites on
Chemong Lake. Data from the Trent canal (44˚22’ N and 78˚18’ W) measured in the fall of 2003 by BIOL 305 was also used for comparison purposes. This small lake on the
Trent canal and Chemong Lake are part of the same water system (Lasenby, 2004).
Sampling materials and methods
Chemong Lake water was sampled for total phosphorus, chlorophyll a, light, temperature, conductivity, dissolved oxygen, zooplankton, and for benthic organisms. Snow and ice samples were collected and analysed for total phosphorus and pH. The depth of the snow on the lake was measured at 9 representative sites in the both the AM and PM. Ice thickness was measured at four representative sites in both the AM and PM. For most
3

water samples, a spoon auger was used to cut the ice. Where larger holes were needed, a gasoline-powered auger was used.
Total phosphorus (TP) in the lake water was sampled using a peristaltic hand pump.
Potassium persulfate was placed in each vial with the sample water to assist in breaking down the phosphorus prior to analysis. Samples were taken at the ice/water interface and then at 1m intervals until 4m in the AM, and 5m in the PM. Four representative ice samples and 3 representative snow samples for both AM and PM were collected and analyzed for TP. All samples were autoclaved at the lab, and the ammonium molybdate method was used for the analysis of total phosphorus using a spectrophotometer. See
Trent University WebCT for details on the ammonium molybdate method. The spectrophotometer standard curves for the AM and PM water samples can be seen in
Appendix B. Calculations of total phosphorus using the standard curves can be seen in
Appendix C.
Chlorophyll a was sampled using a peristaltic hand pump. Samples were taken at the ice/water interface and then at 1m intervals until 4m in both the AM and PM sampling events. The samples were then filtered through a 47mm glass fibre filter and the ethanol extraction method was used for the analysis. See Trent University WebCT for details on the ethanol extraction method. The concentration of chlorophyll a was calculated using the formula:
Chl a ( μ g/L) = v[13.7(665-750) – 5.76(649-750)]
VL x L
4

where: v is the volume of the extractant (10ml)
VL is the volume of lake water filtered in litres (1L)
L is the length of the light path of the cell (1cm)
665, 649 and 750 are the corrected optical densities at 665nm, 649nm, and
750nm
Appendix D shows the chlorophyll a concentration calculations.
Light penetration into the water column was measured using a Li-Cor LI-185B model light sensor and measured in units of μ Einsteins/m
2
/second. Light measurements were taken with and without snow on the ice at 0.5m intervals staring at the ice/water interface, and extending to a depth of 6.5m with the snow, and 5.5m without the snow.
Dissolved oxygen (DO) and temperature were measured simultaneously using a YSI 58 model dissolved oxygen meter. DO was measured in mg/L, and temperature was measured in °C. Dissolved oxygen and temperature were measured at 0.5m intervals from the ice/water interface to 7.0m in the AM and 6.0m in the PM.
Conductivity was measured using a YSI 33 model conductivity meter. Measurements were taken in μ mhos/cm at 0.5m intervals from the ice/water interface to a depth of 7.0m
(lake bottom) in the AM and 6.0m in the PM. Conductivity measurement were standardized to 25°C with a correction factor of 2% per °C.
5

The pH of 3 representative ice and snow samples in both the AM and PM were collected in plastic bags and measured at the lab using an Oakton pH Testr2 model.
Zooplankton were sampled using a 27 L Schindler Trap with a 72 μ m mesh net on the cod end. Samples were taken at 1.0m intervals from the ice/water interface, to a total depth of 4m in the AM, and 5m in the PM. All zooplankton were preserved in 70% ethanol and were identified and enumerated using dissecting microscopes in the lab.
Benthic communities were qualitatively sampled at 3 representative sites in both the AM and PM using a 15cm X 15cm Ekman Dredge. A 1.5mm box screen was used to located and separate the organisms. Species found were preserved in 70% ethanol in the lab and subsequently identified and counted.
According to the hypsographic curve in Figure A, the lake is approximately 5.1 x 10
6
m
3 in volume and the ice cover is approximately 1.1 x 10
6
m
3
in volume. Average ice and snow thickness and depth over the lake can be compared in Figure 2. Average snow depth was 17.6cm and average ice thickness was 43.3cm.
Total phosphorus samples taken in the AM and PM were averaged. The highest averaged concentration was 152 μ g/L and found at a depth of 3m. Figure 3 shows the average total phosphorus concentrations found at each depth in the water column. The average total
6

phosphorus concentration in the ice was 17 μ g/L, and the average snow concentration was
68 μ g/L.
Chlorophyll a concentrations were also averaged between the AM and PM results. Chl. a concentrations peaked at the ice/water interface at 6.5 μ g/L, and then fell at 1m to 2.4
μ g/L and continued to decline. Chl. a concentrations for the water column can be seen in
Figure 4.
Light penetration at different depth intervals under the ice can be seen in Figure 5. The results can be compared between those with snow cover and those without snow cover over the ice. Light penetration was the greatest at the surface for both snow cover and no snow cover. At the surface, light penetration was almost twice as great without the snow.
In both cases, light penetration decreased rapidly with depth. At 3m, 97-98% of the light had been attenuated in both cases. In the results taken with snow cover, there was a slight increase in light penetration at a depth of 3.5m, which then continued to decrease with depth.
Temperature readings were averaged and the lowest reading occurred at the ice/water interface. Temperature then proceeded to increase to no more than 5.9 ˚C with depth.
Figure 6 shows the averaged temperature readings at depths.
Figure 7 shows the averaged DO concentrations from the AM and PM readings.
Concentrations peaked at the ice/water interface with a value of 13.1 mg/L. DO
7

concentrations then declined with depth to 0.5mg/L. Figure 7a shows the relationship between DO and chl. a abundance.
Conductivity measurements increased with depth. Averaged AM and PM measurements can be seen in Figure 8. Greatest conductivity concentration was 431 μ mhos/cm, which occurred nearest to the sediment/water interface. Conductivity of the black ice was measured at 18 μ mhos/cm.
Figure 9 shows the averaged pH readings from the snow samples collected over the ice.
The pH of the ice was close to neutral at 6.85, and the snow pH was more acidic at 5.17.
Averaged AM and PM zooplankton density results at depths can be seen in Figure 10.
Calanoid copepods were most abundant at all depths, but their density peaked at 2m with a value of 17 organisms/L. Cyclopoid copepods were the second most abundant, and their greatest density also occurred at 2m but with a value of 1 organism/L.
Results from 3 Ekman dredges during each AM and PM sampling event revealed a total of 2 Chironomus in the AM, and 13 Chironomus in the PM for a total average of 8
Chironomus.
All raw data collected from this experiment can be reviewed in appendix E.
8

The thickness of the ice on Chemong Lake was similar to average lake ice thickness in the Kawartha Region (Lasenby, 2003). The ice observed on the lake was black ice due to its appearance and low conductivity. Black ice is very transparent with little gas bubbles
(Wetzel, 2001, P. 63). During black ice formation, freeze-out of gases, nutrients, and major ions occurs (Belzile et al., 2001; Baehr and Degrandpre, 2002). Ice that has thawed and mixed with snow and water is termed white ice (Wetzel, 2001, p. 63). The lake to ice volume ratio is 5:1, or 20% of the lake was ice. Ice volume is of concern for shallow lakes because this portion of the lake is unavailable to organisms. There is reduced habitat and a shallower photic zone that limits the amount of primary productivity in the lake.
Total phosphorus concentrations indicate that Chemong Lake is a eutrophic lake (Wetzel,
2001, p. 283). Other lakes and rivers in the area have been found to contain between 8.2 to 27.9 μ g/L total phosphorus (Gartner Lee Ltd., 2002). The peak in TP at 3m may have occurred for many reasons and further studies are required to help fully understand this.
In a study by Shammon and Hartnoll (2002), dissolved organic nitrogen and phosphorus formed the majority of the dissolved substances in the winter, however dissolved organic phosphorus showed little variation between summer and winter. The slight increase is TP near the bottom of the lake may be attributed to redox reactions that release phosphorus at low oxygen concentrations (Gibson et al., 2001; Wetzel 2001, p. 246, 250). TP concentrations analysed in the ice and snow were lower than those found in the water column. Reduced levels were found in the ice due to the freeze-out process during ice
9

formation (Belzile et al., 2001; Baehr and Degrandpre, 2002). Snow TP concentrations were a bit elevated and close to those classified at the mesotrophic-eutrophic boundary in lakes (Wetzel, 2001, p. 285). The addition of this phosphorus to the lake after snowmelt can increase the productivity of this already eutrophic lake (Wetzel, 2001, p. 275). This additional productivity in the spring and summer can have negative effects on the oxygen concentration next winter under ice, especially in the deeper waters. The more organic material present, the more oxygen needed to break down the material (Baehr and
Degrandpre, 2002).
Chlorophyll a concentrations characterize Chemong Lake as oligotrophic to mesotrophic
(Wetzel, 2001, p. 283, 389). These chl. a concentrations suggest that algal biomass is fairly low in this lake. Considering the high concentration of total phosphorus in the lake, there should also be high concentrations of algae (Delgadillo-Hinojosa et al., 1997).
This reduced amount of algae may be attributed to the grazing f zooplankton or the time of year (Belzile et al., 2001). This is possible since the dominant zooplankton present are primarily herbivores (Wetzel, 2001, p. 417-418). Also, since the amount of daily sunlight received in Canada in February is less than that of the growing season, a reduced amount of light is available for algae reproduction. However, reduced levels of chlorophyll a coupled with high total phosphorus values were also observed in the Trent canal in the fall. It may be that since total phosphorus was measured, the majority of the phosphorus is in a form not suitable for biological uptake. Further studies would help understand why chlorophyll a levels are low while phosphorus levels are continually high.
10

Light penetration and phytoplankton abundance are related through photosynthesis
(Wetzel, 2001, p. 342). Algae require light to photosynthesize, therefore most algae can be found where photosynthetically available radiation (PAR) is accessible (Belzile et al.,
2001). This was observed in this experiment. Highest concentrations for both parameters occurred at the ice/water interface. Abundance of chlorophyll a, as well as light penetration both significantly declined after 1m.
Light transmission is higher through black ice and lower through ice containing gases and particles, or when ice is covered with snow (Wetzel, 2001, p. 63-64). Other studies confirm that snow removal greatly increases light penetration (Belzile et al., 2001;
Järvinen et al, 2002). This trend was observed in this experiment, however there was a slight increase in light penetration under snow cover at a depth of 3.5m. This may have been due to the movement of clouds or patchiness in snow cover. Belzile et al. (2001) found similar results however the peaks were associated with Schlieren effects related to the mixing of waters with different salinities. Since Chemong Lake is a freshwater lake, it is not likely that these effects were occurring. Light penetration can be compared to measurements taken on the Trent canal in the fall (Figure 5). Light penetration into the water is over twice as great without ice-cover. This increased light penetration deepens the photic zone, which then increases the volume where primary productivity can take place.
Because of the ice barrier in the winter, light penetration has less of an impact on lake temperature. During the ice-free season, light penetration helps to increases surface
11

water temperatures (Wetzel, 2001, p. 56, 72), as was the case in the fall canal measurements (Figure 6). During the ice-cover period, lake temperatures were lowest near the ice, and increased with depth. This type of temperature profile was observed on an ice-covered lake in Montana (Baehr and Degrandpre, 2002), as well as a perennially ice-covered lake in the high arctic (Belzile et al., 2001). Colder water stays at the surface because it is less dense than warmer water (Wetzel, 2001, p. 11).
Colder water also has the capability to hold more oxygen (Baehr and Degrandpre, 2002;
Wetzel, 2001, p. 151). For this reason, it makes sense that the highest DO concentrations occurred at the ice/water interface. The water in this region can be considered saturated with oxygen (Wetzel, 2001, p. 154). High DO concentrations have been related to photosynthetic activity of the algae found in the same region (Belzile et al., 2001; Phillips and Fawley, 2002). According to Figure 7a, there is a relationship in this experiment between these two parameters (r 2 = 0.88).
DO concentrations reached less than 4mg/L under 2.5m. Most fish require DO concentrations to be greater than 4mg/L (Lasenby, 2004). Therefore, since the bottom 3-
4m of the lake has insufficient oxygen to support these organisms, they are required to reside in the shallower parts of the lake. Moreover, the presence of ice also reduces the volume of habitat suitable for fish. Under these circumstances, the DO available to organisms becomes depleted faster than it can be replaced over the ice-cover period
(Phillips and Fawley, 2002). This severe depletion of oxygen can result in the death of many fish. This process is called winterkill (Phillips and Fawley, 2002; Wetzel, 2001, p.
12

64). Further studies are required to assess whether winterkills will occur in Chemong
Lake and what to do to prevent them. In the deepest water measurements, oxygen was virtually absent. Deep-water DO concentrations measured in the Trent canal in the fall were no less than 6.4mg/L. However this was related to the fact that the lake was mixing.
Duration of mixing in the fall regulates the amount of oxygen in the hypolimnion during the ice-cover period (Baehr and Degrandpre, 2002; Järvinen et al, 2002). Comparisons between fall and winter DO concentrations can be seen in Figure 7.
Anoxic environments near the sediment/water interface are responsible for the release of phosphorus from the sediment to the water column (Gibson et al, 2001; Wetzel 2001, p.
246, 250). Highest conductivity values measured in the deep water are likely related to this release of nutrients. Many ions exist at the sediment/water interface due to decomposition (Wetzel, 2001, p. 640). Due to the freeze-out of ions, nutrients and gases during ice formation; higher overall conductivity values can be expected during the icecover period rather than the ice-free period. According to measurements taken in the fall on the Trent canal, lower conductivity values were observed during this ice-free season.
Conductivity values for this fall experiment on the Trent canal can be compared to those of Chemong lake in Figure 8.
The pH of the snow was lower than that of the ice. This difference can be attributed to acid precipitation (Wetzel, 2001, p. 840). Additions of acid to the lake have been found to occur during acid snowmelt (Järvinen et al, 2002). However, this addition should be buffered in Chemong Lake because it is situated on limestone bedrock (Wetzel, 2001, p.
13

840). Trent canal pH measured in the fall at 9.1 demonstrated the alkaline properties of the water system on limestone bedrock.
Zooplankton found under the ice in Chemong Lake were predominantly calanoid copepods. Their average peak density was 17 zooplankton/L at a depth of 3m. These results are considerably different to those found in the Trent Canal in the fall where greatest density consisted of 3.4 Bosmina / L at a depth of 1m. This coincides with the
PEG-model that identifies typical seasonal succession of zooplankton (Sommer et al.,
1986). As the model predicts, large crustaceans are dominant in the spring. These large crustaceans are then replaced by small cladocerans and rotifers in late summer due to fish predation in early spring (Yoshida et al, 2001). This succession was partly observed in this experiment by the abundance of Bosmina in the Trent canal measured in the late summer, early fall, changing to an abundance of calanoid copepods close to spring. As in this experiment, Yoshida et al. (2001) observed an increase in zooplankton biomass prior to spring phytoplankton blooms. This mid-winter increase is contrary to the PEG-model
(Yoshida et al., 2001). This increase was related to strong water mixing that resuspended organic matter. This is unlikely to be the case in this experiment, since the lake was covered with ice. However, it is possible that rivers flowing into Chemong
Lake have stirred up sediments containing nutrients. The abundance of zooplankton at
3m corresponds with the steep decline in chlorophyll a measurements, illustrating the herbivore behavior of calanoid copepods (Wetzel, 2001, p. 417-418), as well as their grazing capabilities on large phytoplankton (Yoshida et al., 2001). Calanoid copepods were also found to be the most abundance zooplankton in both this experiment and the
14

experiment on Lake Biwa by Yoshida et al. (2001). This may be due to fact that they appear to be more dominant swimmers (Yoshida et al., 2001), and can evade predation better than slow moving cladocerans (Browman, 1990; Lochhead, 1977). Further studies are essential to assess whether this statement is actually true.
Benthos in Chemong Lake was depleted in abundance and diversity when compared to fall measurements in the Trent canal. In the fall, 9 different types of benthic fauna were observed, including greatest abundance in Chironomids. The reduced number of benthic organisms in the winter is likely related to the anoxic conditions near and probably in the sediments. Kajak (1997) reported similar conclusions on reduced numbers of
Chironomus . Extremely low DO concentrations are probably responsible for the absence of other organisms likely found in the benthic community. Additional studies are required to further understand the benthic community found in Chemong Lake.
15

List of References
Baehr, M.M. and M.D. Degrandpre. 2002. Under-ice CO2 and O2 in a freshwater lake.
Biogeochemistry 61: 95-113.
Belzile C., W. F. Vincent, J.A.E. Gibson and P. Van Hove. 2001. Bio-optical characteristics of the snow, ice and water column of a perennially ice-covered lake in the High Arctic. Can. J. Fish. Aquat. Sci. 58: 2405-2418.
Browman, H.I. 1990. Behavioral ecology of foraging in a zooplanktivorous fish,
Pomoxis annularis, and a predaceous invertebrate, Leptodora kindti: Ontogenetic and neuroethological perspectives. Diss. Abst. Int. Pt. B - Sci. & Eng. 51: no. 4 p.
205
Delgadillo-Hinojosa, F., G. Gaxiola-Castro, J.A. Segavia-Zavala, A. Munoz-Barbosa and
M.V. Orozco-Borbon. 1997. The effect of vertical migration on primary production in a bay of the Gulf of California. Est. Coast. Shf. Sc. 45: 135-148.
Gibson, C.E., G. Wang, R.H. Foy and S.D. Lennox. 2001. The importance of catchment and lake processes in the phosphorus budget of a large lake. Chemosphere 42:
215-220.
Järvinen, M., M. Rask, J. Ruuhijärvi and L. Arvola. 2002. Temporal coherence in water temperature and chemistry under the ice of boreal lakes. Water Research 36:
3949-3956.
Lasenby, D. BIOL 305 - 2003/2004 information from lectures at Trent University,
Peterborough, ON.
Lochhead, J.H. 1977. Unsolved problems of interest in the locomotion of Crustacea.
Conference - Presented at: Symposium on scale effects in animal locomotion,
Cambridge, UK, Sep 1975. Scale effects in animal locomotion. Pedley, T.J. (ed.)
Publ. by: Academic Press, London (UK) 1977 p. 257-268
Phillips, K.A. and M. W. Fawley. 2002. Winter phytoplankton blooms under ice associated with elevated oxygen levels. J. Phycol. 38: 1068-1073.
Shammon, T.M. and R.G. Hartnoll. 2002. The winter and summer partitioning of dissolved nitrogen and phosphorus. Observations across the Irish Sea during
1997 and 1998. Hydrobiologia 475/476: 173-184.
Wetzel, G, 2001. Limnology; lake and river ecosystems, third edition. Academic Press,
San Diego, California.
16

Yoshida, T., M. Kagami, T. B. Gurung and J. Urabe. 2001. Seasonal succession of zooplankton in the north basin of Lake Biwa. Aquatic Ecology 35: 19-29.
Yoshida, T., M. Kagami, T. B. Gurung and J. Urabe. 2001. Contrasting effects of a cladoceran ( Daphnia galeata ) and a calanoid copepod ( Eodiaptomus japonicus ) on algal and microbial plankton in a Japanese lake, Lake Biwa. Oecologia 129:
602-610.
17