New Jersey School of Conservation
Conveying knowledge of how Earth systems operate and how human actions affect these systems. Conservation is Everyone's Responsibility!
The mission of Montclair State University's School of Conservation is to gather knowledge of Earth systems through research and to communicate this knowledge through education. Our goal is to contribute to the resolution of environmental problems by cultivating environmentally responsible behaviors that will encourage scientists, teachers, students and citizens to promote sustainable practices in their communities.
Winter Wonders of Lake Wapalanne
Our Lake Wapalanne is home to various forms of aquatic life, including plants, algae, fish, reptiles and amphibians. While it is easy to imagine how these organisms thrive during the warm months of the year, the winter months can pose serious threats to their survival. Lake Wapalanne is shallow, and it undergoes various changes as winter approaches and the temperature drops.
As the air temperature cools, so does the water. To a certain point, the density of water increases as temperature decreases. Therefore, as the water in the lake cools, the colder, denser water will sink to the bottom. When the water reaches 4°C it is at its highest possible density. When water continues to cool past the 4°C mark, its density begins to decrease, so water colder than 4°C will be closer to the surface. Water that then cools to 0°C freezes and forms a layer of ice at the surface. This layer of ice can become thicker as more water cools to 0°C and forms more ice.
Water Density vs Temperature
As the water becomes colder it is able to hold more dissolved oxygen. This dissolved oxygen is essential to the survival of the fish, insects, and other aquatic organisms that require oxygen for respiration. While to colder waters can contain more dissolved oxygen, any ice and/or snow that accumulates on top of the lake forms a barrier between the water and the air, preventing the further diffusion of oxygen into the lake. Aquatic plants would normally be able to produce and release oxygen into the water, but the presence of ice and/or snow also limits or prevents sunlight from penetrating into the water for photosynthesis. For the most part, all of the oxygen-dependent organisms in the lake must make it through the winter with the amount of oxygen that is trapped when ice forms on the surface. This has required aquatic organisms to adapt.
When winter sets in and the lake temperature cools, the fish that inhabit the lake (such as the bluegill pictured below) must alter their behavior in order to survive. In order to use less oxygen and require less food, the fish slow their metabolism and heart rate, entering a state of dormancy. Some species of fish will move slowly and appear sluggish, while others will burrow into the sediment and remain still. This allows them to survive through the cold, oxygen-deprived winter months. Oxygen-dependent organisms may also gravitate to parts of the lake that may remain exposed or where melting snow enters as runoff, churning the lake water and incorporating more oxygen.
A special example of adaptation for winter survival exists in the painted turtles (pictured below) that inhabit Lake Wapalanne. These air-breathing turtles hibernate underwater during the winter months, burying themselves into the mud. Similar to the fish that inhabit the lake, painted turtles slow their heart rate and metabolism so that they are barely functioning at all. They do not eat or breathe at all throughout the winter. If conditions allow, however, they may absorb oxygen through specialized skin cells that are located near their tails. They are quite talented turtles!
While a winter lake may appear to be eerie and lifeless, we can enjoy its quiet beauty knowing that the animals beneath the ice are well prepared for the challenges that winter brings.