Monday, January 22, 2018

Episode 404 (1-22-18): Ice on the Pond

CLICK HERE to listen to episode audio (3:57).

Transcript of audio, notes on the audio, images, and additional information follow below.

All Web addresses mentioned were functional as of 1-19-18.


From the Cumberland Gap to the Atlantic Ocean, this is Virginia Water Radio for the week of January 22, 2018.   I’m joined this week by guest host Saalehah Habeebah, the spring 2018 intern at the Virginia Water Resources Research Center.

SOUND – ~5 sec

This week, those mystery sounds open an episode written especially for Virginia science students in upper elementary school and middle school, that is, about grades 4 to 8.  Have another listen to the sounds for about 15 seconds, and see if you can guess where the sounds were recorded.  And here’s a hint: the numbers 32, 0, and 273 are all connected to this answer.

SOUND - ~15 sec
If you guessed a frozen pond, you’re right!  You heard sounds from ice skaters on a pond in Blacksburg, Va., on January 14, 2018.  And if you knew that the freezing point of water is 32 degrees on the Fahrenheit scale, 0 on the Celsius scale, and 273 on the Kelvin scale, you’re a water-temperature expert!  Water temperature remaining below that freezing point, leading to ice cover on ponds and lakes, is a wintertime fact of life in northern states and Canada.  But even in Virginia, many water bodies typically ice-over during some part of the winter.  The ice remains over the water because ice is less dense than liquid water—the same property is involved when ice cubes float in a glass and when icebergs float in the ocean.

Under an ice layer, aquatic organisms carry out various winter-survival strategies.  Burrowed in the bottom may be inactive fish, frogs, turtles, insects, worms, and the eggs of various animals, while certain kinds of fish and other animals continue to be active.  All of those creatures depend on there being enough oxygen dissolved in the ice-covered water.  In warm weather, the water in lakes and ponds can mix with the air above it and be replenished with oxygen; that can’t happen when ice covers the water.  Oxygen does get added to ice-covered water when algae or plants under the ice can get enough light to continue photosynthesis.  Sometimes, though, dissolved oxygen gets so low that a winterkill of fish takes place.  This typically happens in shallow water bodies, or under snow or thick ice that keeps out the light needed for photosynthesis.

While skaters have fun on a slick frozen track – SOUND ~4 sec – life goes on beneath the ice, where the biology of living things interacts with water’s chemical and physical properties.


For more Virginia water sounds, music, and information, visit us online at, or call us at (540) 231-5463.  Virginia Water Radio is produced by the Virginia Water Resources Research Center, part of Virginia Tech’s College of Natural Resources and Environment.  Thanks to Ben Cosgrove for his version of “Shenandoah” to open and close the show.  In Blacksburg, I’m Alan Raflo, thanking you for listening, and wishing you health, wisdom, and good water.


This Virginia Water Radio episode updates and replaces Episode 144 (1-14-13).

The sounds of ice skaters were recorded on a pond at Heritage Park in Blacksburg, Va., on January 14, 2018.  Thanks to skaters Jeff and Kaiden for participating in this episode.

Click here if you’d like to hear the full version (2 min./22 sec.) of the “Shenandoah” arrangement/performance by Ben Cosgrove that opens and closes this episode.   More information about Mr. Cosgrove is available online at

Skating marks from ice skating on the pond in Heritage Park in Blacksburg, Va., where the skaters heard in this Virginia Water Radio episode were recorded, January 14, 2018.
Ice on a stormwater pond on the Virginia Tech campus in Blacksburg, January 19, 2018.
Ice on Claytor Lake (at the Sloan Branch inlet) near Draper, Va. (Pulaski County), January 6, 2018.


On the density of ice, From the U.S. Geological Survey, Water Science School, “Density,” online at
“The best way to visualize how water can have different densities is to look at the frozen form of water.  Ice actually has a very different structure than liquid water, in that the molecules align themselves in a regular lattice rather than more randomly as in the liquid form.   It happens that the lattice arrangement allows water molecules to be more spread out than in a liquid, and, thus, ice is less dense than water.   Again, lucky for us, as we would not hear that delightful tinkle of ice cubes against the side of a glass if the ice in our ice tea sank to the bottom.  The density of ice is about 90 percent that of water, but that can vary because ice can contain air, too.  That means that about 10 percent of an ice cube (or iceberg) will be above the water line.

“This property of water is critical for all life on earth.  Since water at about 39°F (4°C) is more dense than water at 32°F (0°C), in lakes and other water bodies the denser water sinks below less-dense water.  If water was most dense at the freezing point, then in winter the very cold water at the surface of lakes would sink, the lake could freeze from the bottom up, and all life in them would be killed.  And, with water being such a good insulator (due to its heat capacity), some frozen lakes might not totally thaw in summer.

“The real-world explanation of water density is actually more complicated, as the density of water also varies with the amount of material that is dissolved in it.  Water in nature contains minerals, gasses, salts, and even pesticides and bacteria, some of which are dissolved.  As more material is dissolved in a gallon of water then that gallon will weigh more and be more dense—ocean water is denser than pure water.”

On dissolved oxygen and winterkill of fish, from the Michigan Department of Natural Resources, “Fish Kills,” undated, online at,4570,7-153-10364_52259-119822--,00.html.

“…[S]pecies of fish vary in their tolerance of low oxygen.  Trout are most sensitive; walleye, bass, and bluegill have intermediate sensitivity; and northern pike, yellow perch, and pumpkinseed are relatively tolerant.  Bullheads and certain minnows are very tolerant.   Lakes prone to periodic winterkill can often be detected from the composition of their fish populations—tolerant species predominate, sensitive species are rare, and prey greatly outnumber predators.  Fortunately, usually enough fish survive, either in the lake or in connecting waters, to repopulate the lake in a couple of years.  Only for extreme die-offs is fish restocking necessary.

“The dissolved oxygen content of water depends primarily on three variables.  These are the amount of mixing with the air above the lake, the rate of oxygen production by plants, and the rate of oxygen consumption (respiration) by living aquatic organisms.   During periods of prolonged ice cover, the lake is sealed off from the atmosphere and cannot be recharged with oxygenated air.  Furthermore, ice and snow reduce the amount of sunlight reaching aquatic plants, thereby reducing photosynthesis and oxygen production.  (During photosynthesis, living plants use sunlight energy and carbon dioxide to make plant tissue and dissolved oxygen).  Meanwhile, on-going consumption of oxygen depletes the supply of oxygen stored in the lake when the lake froze over.  Shallow, productive lakes are at a disadvantage because they have a low storage capacity and high rates of oxygen-consuming decomposition.

“February is usually a critical period and is the best time to check the oxygen content of lakes prone to winterkill.  A good midwinter thaw about then often recharges the lake's oxygen supply by means of photosynthesis and melt water.  Conversely, a prolonged winter, with continuous snow cover and late ice-out, increases the chance of winterkill.”


M. W. Buck, Where They Go in Winter, Abingdon Press, Nashville, Tenn., 1968.

G. A. Cole, Textbook of Limnology, 2nd Edition, C.V. Mosby Company, St. Louis, Mo., 1979., “Kelvin Temperature Scale,” online at

B. S. Martof, et al., Amphibians and Reptiles of the Carolinas and Virginia, University of North Carolina Press, Chapel Hill, N.C., 1980.

Michigan Department of Natural Resources, “Fish Kills,” undated, online at,4570,7-153-10364_52259-119822--,00.html.

Minnesota Department of Natural Resources, “Winterkill & Other Fish Die-Offs,” undated, online at

National Oceanic and Atmospheric Administation/National Ocean Service, “Where do fish go when it freezes outside?”, undated, online at

Alisa Santiesteban, “A cold world with an icy ceiling,” Wisconsin Natural Resources Magazine, December 2009, online at

R. G. Wetzel, Limnology, 2nd Edition, Saunders College Publishing, Philadelphia, Penn., 1983.

J. R. Voshell, Jr., Guide to Common Freshwater Invertebrates of North America, McDonald and Woodward Publishing Company, Blacksburg, Va., 2002.

All Water Radio episodes are listed by category at the Index link above (  See the “Science” subject category for episodes on physical states of water, and the “Weather” subject category for episodes on frost, ice, or snow.

This week’s episode is the second in a series in 2018 on freezing water, designed for specific grade levels of Virginia science students. The episodes in the series are as follows:
Episode 403, 1-15-18 – on freezing and ice, for kindergarten through 3rd grade;
Episode 404, 1-22-18 – on ice on ponds and lakes, for 4th grade through 8th grade;
Episode 406, 2-5-18 – on ice on rivers, for middle school;
Episode 407, 2-12-18 – on snow chemistry and physics, for high school.

Following are links to previous Water Radio episodes (various topics) designed especially for certain K-12 grade levels:
Episode 250 (1-26-15) – on boiling, for kindergarten through 3rd grade;
Episode 255 (3-2-15) – on density, for 5th and 6th grade;
Episode 282 (9-21-15) – on living vs. non-living, for kindergarten;
Episode 309 (3-28-16) – on temperature regulation in animals, for kindergarten through 12th grade;
Episode 332 (9-12-16) – on dissolved gases, especially dissolved oxygen in aquatic habitats, for 5th grade.
Episode 403 (1-15-18) – on freezing and ice, for kindergarten through 3rd grade;


This episode targets the following Virginia 2010 Science SOLs for grades 4 to 6, plus the Life Science and Physical Science courses:

Grades K-6 Earth Resources Theme
4.9 – Va. natural resources, including watersheds, water resources, and organisms.

Grades K-6 Interrelationships in Earth/Space Systems Theme
4.6 – weather conditions, phenomena, and measurements.

Grades K-6 Living Systems Theme
6.7 – natural processes and human interactions that affect watershed systems; Va. watersheds, water bodies, and wetlands; health and safety issues; and water monitoring.

Grades K-6 Matter Theme
6.5 – properties and characteristics of water.

Life Science Course
LS.9 – adaptations for particular ecosystems’ biotic and abiotic factors, including characteristics of land, marine, and freshwater environments.

Physical Science Course
PS.7 – temperature, heat, and thermal energy transfer, including phase changes, melting point, etc.

Following are Science SOLs for other grades that may also be supported by this episode:

Grades K-6 Earth Patterns, Cycles, and Change Theme
1.7 – changes in temperature, light, and precipitation affect plants and animals, including humans.
2.7 – weather and seasonal changes affecting plants and animals.

Grades K-6 Life Processes Theme
3.4 – behavioral and physiological adaptations.

Grades K-6 Matter Theme
K.5 – water properties, including flowing, objects floating or sinking, and water occurring in different phases.
2.3 – properties of solids, liquids, and gases.

Biology Course
BIO.2 – water chemistry and its impact on life processes.
BIO.8 – dynamic equilibria and interactions within populations, communities, and ecosystems; including nutrient cycling, succession, effects of natural events and human activities, and analysis of the flora, fauna, and microorganisms of Virginia ecosystems.

Physics Course
PH.4 – applications of physics to the real word, including roles of science and technology.

Virginia’s SOLs are available from the Virginia Department of Education, online at