Aquatic macroinvertebrates are water bugs that do not have a backbone and that we can see with our naked eye. They include insects, crustaceans, clams, mussels, and snails. They vary in shape and size, but all live in the water for at least a portion of their life cycle, so their survival depends on water quality. They are also a crucial part of the food chain which makes them an important part of the aquatic ecosystem. Different types of macroinvertebrates have varying sensitivities to water pollution. Therefore, by examining the abundance and types of macroinvertebrates present in a stream, we can get a general idea of the water quality or health of that stream. Most macroinvertebrates live in the stream bottom among rocks, under logs or in leaf packs, making them relatively easy collect with a dip net. It’s also inexpensive to collect and process macroinvertebrates and something that is easily done with the help of volunteers. The MACC partners with the Outdoor Discovery Center Macatawa Greenway to monitor macroinvertebrate populations at 7 locations in the Macatawa Watershed twice a year. Our monitoring program started in the Fall of 2012 and we intend to continue well into the future. If you are interested in volunteering to collect and process macroinvertebrates, contact Kelly at email@example.com and we will add you to our volunteer list. Below is a summary of the data collected over the last 2 years:
Since this graph represents only a short time period, it is too soon to draw any conclusions from the data. What we can see from the data is that there is a lot of variability within a site over time and across sites for any given event. Some of this is natural due to seasonality (sampling occurs in spring and fall to capture different species during aquatic life cycle stages), weather conditions or streamflow.
During the spring of 2011 the Macatawa Watershed Project began working in conjunction with Hope College and the Outdoor Discovery Center Macatawa Greenway to collect samples of suspended sediment at 43 locations throughout the watershed. The intensive monitoring project was funded in part by the Michigan Department of Environmental Quality and in part by private donations and allowed us to construct our own sampling equipment (pictured at right). Sediment enters our local waterways via streambank erosion and surface runoff during rain events. It is important to study sediment because phosphorus is often attached to sediment and Lake Macatawa suffers from excessive levels of phosphorus. The monitoring allows us to measure how much sediment is coming from different parts of the watershed so we are better able to target remediation activities. The data collected was used to rank the subwatersheds from worst to best in terms of how much sediment was collected in each tributary. In the map below, the 8 major subwatersheds are numbered 1-8, 1 indicating the most amount of sediment and 8 indicating the least. The pink dots represent the relative amount of sediment collected based on the amount of contributing area.
Each year through the spring and summer months, several volunteers collect water transparency data using an 8-inch, circular, black and white metal plate attached to a calibrated rope. This tool is called a Secchi disk. Volunteers take secchi readings at a designated locations in Lake Macatawa about once a week during open water season. The volunteer lowers the disk into the water until it is no longer visible and notes that depth from the markings on the rope. The disk is then lowered a little further and then raised back up until it is just visible. This second depth reading is averaged with the first, and the final number is recorded on a data sheet.
This measure estimates the clarity of the water. Water transparency is a quick and easy measurement that tells scientists a lot about a lake’s water quality. First, it indicates the amount of light penetration into a lake. Second, Secchi transparency provides an indirect measure of the amount of suspended material in the water. Changes in transparency over time can be an important indicator that a change in water quality is occurring.
Secchi disk measurements provide objective means to evaluate water clarity versus subjective statements such as “It is clear,” or “It is muddy.” One person’s clear water may be another person’s muddy water.
We’d like to have additional help! Contact the MACC to learn more about becoming a part of the volunteer monitoring program.
Click here to see the MACC’s Secchi data through 2013 that is collected at 4 locations weekly throughout the spring and summer months by our local volunteers.
The graph below summarizes the annual average Secchi depth from 2002 through 2013 at four locations in Lake Macatawa. The overall trend seems to indicate that the Secchi depth is decreasing, meaning that the clarity of the lake is decreasing. Increasing Secchi depth would indicate improved water clarity.