Diamond Lake Study
By: Heather Pearson
My advanced biology class has been studying water habitats for the past few weeks. We have learned about the plant, animal and insect life that are apart of the shoreline environment. We have even started to learn about the different chemical and other tests that many people perform to study the lake/pond water. On September 22, 2003 the ACGC advanced biology class was able to go to Diamond Lake (on a grant) and study the lake water and surrounding environment.
When we first arrived at Diamond Lake we were taken into a garage, which was greatly appreciated, and were told what was all going to happen. Mr. Roger Ramthun of the Minnesota Pollution Control Agency told about each test we would perform and how we would accomplish it. Roger goes to different lakes and tests them for different chemicals and substances.
We learned that Diamond Lake is in the North Central Hardwood forest ecosystem. By using the secchi disk twice a month from May-September, we see that in an average spring you can see down 16 feet, and by fall you can only see down about 2.5 feet. Because Diamond Lake is so shallow, the "soup" or substrate at the bottom of the lakes tends to mix easily with the movement of the waves with the rest of the water. This combined with the algae causes the lake to become murky.
Roger also told us about the surrounding environment. The outlets and streams are extremely important to the lake health. The streams often bring in large amounts of sediment in the lake. The terrestrial plants along the lakes shores help to keep runoff to a minimal and help prevent erosion of the lake shores. The emergent and submergent plants help provide a shelter for fish and filter the water. For example, lily pads often provide shade for perch. They reflect the suns hot rays and keep the water cooler. This not only is nice for the fish, but for humans too. By keeping the water cool, the algae don't overproduce and make the water an undesirable green color.
We will be studying the streams by finding the velocity of the water current. We will do this by using a flow meter. We must always make sure not to touch the transducer. The oils on our hands will make it more waterproof and give us less accurate results. We take readings from one point in the stream and move over one foot at a time until we have crossed the stream.
It's at this point that our class split into two groups. I went with Mrs. Aagesen to study the stream/outlet while the other group went out on the pontoons. Since I was not able to wear the waders I wasn't able to use the flow meter to find the velocity of the stream current. Instead I took water samples from the stream. I used old peanut butter jars and scooped different water samples from various pools, then had them labeled.
The water seemed very dirty. There seemed to be an oily film on the top of most of the water. Other pools of water were an ishy rust color. I would guess that this is caused by all of the dead and decaying carp that litter the pools and surrounding banks. The stream must have recently dried up, and the fish ran out of food and oxygen. We then moved back to the docks where the pontoons left from and took soil samples from the surrounding lawns. By studying the soil we can often find out what is affecting the lake water. We took small samples of soil, placed them in zip-lock bags and labeled them.
When the pontoons arrived back at the docks my group was able to take our turn studying the water. After arriving at the marked locations on the lake, we first studied the water turbidity, or clarity. We did this by using the secchi desk. A secchi disk is basically a round metal plate tied to a rope that is marked off in 6 inch and foot increments. We found that the lake turbidity was 1.75 1.8 feet.
The next test we performed was a core composite sampler. It is a 2 meter long pvc pipe. Roger washed it out twice, and then in a new spot (so it isn't contaminated) filled it up with water. This water was from the middle part of the lake, not surface, not bottom. From this sample we poured some water into a brown bottle to be sent in for chlorophyll testing. The reason for the brown bottle is so that no sun can get to it and cause more chlorophyll growth. Water was also poured into other bottles to be tested for dissolved oxygen, conductivity and ph levels. These bottles will be sent into a lab to be studied. By using the plankton net Roger was also able to find daphnia or zooplankton. He poured some into a bottle so that we were able to see them.
While on the pontoons, our group also took the temperature of the water. We found that the water was about 16.8 degrees Celsius throughout the lake. It is the same temperature because Diamond Lake is so shallow. The last thing that we did while on the pontoons was using a khemmer bottom sampler to collect water from the bottom of the lake. The water we send in will be tested for phosphorus.
After the study was over, our class was able to go to a shelter in the campgrounds by Diamond Lake and eat our lunches. Ironically it is at this time that the rain decided to stop and the sun came out. Roger gave an overview of why we did this. It turns out that he really just wants us to be aware of lake health. He hopes that maybe by educating us, he can help to change peoples' habits around the lake or any body of water.
During this study I learned that the lake health is not just the water, it includes the surrounding environments like the lakeshores and outlets and inlets. Before the Diamond Lake study, I had no idea that people even tested the water in the lakes. I learned about the different tests that are performed on the lakes and what they mean. Because of the information I received during the lake study I now look at the lake in a whole new way, and I hope that those who live on the lake try to care of it.