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Home > Volume 20, Number 2 > Pulling the Mussels > A Dynamic Water Body

A Dynamic Water Body

Hyde’s Quarry thermally stratifies into three distinct layers during the summer. How it functions in winter is less clear; it may either act as a warm monomictic lake, which remains ice-free, allowing the water column to mix, or as a dimictic lake, becoming inversely stratified, with colder water above denser water of 4°C. In either case, the mixing of water—called lake turnover, which is activated by changing temperatures and the energy of wind pushing water around—is critically important to replenish oxygen in the deepest layers and to promote nutrient cycling through the lake.
Illustriative graph showing the different temperature zones in the water column of Hyde’s Quarry. Starting at the top warmest zone, the Epilimnion averages 70 degrees fahrenheit, it has a depth of 15 feet. The zone below that is the Metalimnion, ranging 50-70 degrees fahrenheit, and has a depth of 15 to 45 feet. Within this zone is the Thermocline, which varies it's depth regularly. The deepest zone is the Hypolimnion zone, which ranges in depth from 45 to 60 feet, and has a temperature of 45 to 50 degrees.

Epilimnion

This top layer receives the most sunlight, warmth, and oxygen. Zebra mussels are common in this area, because their shell shape and byssal thread production let them attach firmly to hard surfaces and endure the motion of wind and waves.

Metalimnion

In this middle layer, cooler water mixes upward, and warmer water mixes downward. The thermocline—the point delineating the greatest temperature and density difference—resides here, moving up and down as the seasons and water temperatures change. In Hyde’s Quarry, the contractor injected potassium chloride directly into the lower layers after the thermocline initially blocked it from diffusing through the water column.

Hypolimnion

This bottom layer holds the coldest, darkest, most dense water. With low dissolved oxygen, it can become anoxic when the water body stratifies strongly in summer. Unlike zebra mussels, which prefer to attach to hard substrate, quaggas can settle in soft sediment here.

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