Plankton Sampling

It Starts with the Plankton  – ESLA Seeks Food Chain Answers

Plankton SamplingTo know why trout or bass or perch or bluegills are longer, shorter, fatter, skinnier, fewer or more abundant, you must understand the food chain in ESLA waters. It starts with the tiny (stuff you need a microscope to see) plant and animal life. That’s why ESLA invested some of your much-appreciated dues support in a first-time study of plankton populations in 2023 and will continue the program in 2024.

Plankton is the bottom of the food web and critical to fish and plant life. Plankton sampling had not been done before in our lakes and will help us compare our waters to lakes in the area and changes in our own lakes over time.  It may provide insight into issues such as the decrease in the whitefish population, disappearance of the planted brown trout, decrease in Hex mayfly hatches, impact of abnormal concentrations such as E. coli and golden brown algae, etc.

ESLA pursued the research after questions arose about the impact that invasive quagga and zebra mussels — voracious plankton feeders — are having on plankton abundance and, consequently, the entire food chain. Quaggas were confirmed for the first time in Elk Lake in 2022 when staff and students from Northwestern Michigan College’s Great Lakes Water Studies Institute, probing Elk’s depths with their sophisticated sonar at the urging of ESLA, found a large bed of quaggas.

That helped lead to the 2023 summer’s research being conducted by the ESLA board’s “Fish Guy” Ken Krentz and ESLA’s lake biologist Samantha Ogle. They collected and had a local lab analyze the relative abundance of phytoplankton (microscopic plant life) and zooplankton (microscopic animal life). Zooplankton is the food that small fish, like minnows, as well as other tiny organisms eat. They, in turn, get eaten by larger fish and other animals.

As a result, the abundance of plankton determines faster or slower growth rates and numbers of our prized game fish. ESLA’s study entails collecting samples from various locations in ESLA waters and analyzing them in a laboratory under a microscope.

A fine mesh conical net is lowered through the water column, then retrieved to filter and collect the plankton. In the spring of 2023, the first of three scheduled collections occurred. Samples were obtained from 10 locations on Elk Lake, Lake Skegemog, and the Torch River. Water depths ranged from shallow to 120 feet. The plan is to repeat sampling midsummer and again in the fall.  The 2023 analysis is a baseline for comparisons to other lakes and future plankton collection and analysis in ESLA waters.