The march of the seasons is a phenomenon not just confined to the land. Our inland lakes change seasonally, too! Just as our environment and our activities are profoundly influenced by seasonal patterns of temperature change, so are all organisms living in lakes. Sudden algae blooms, increased weed growths, movements and behavior of fish are all due, in part, to the physical properties of water itself–the relationship of the density of the water to its temperature. Density (heaviness) of water is greatest when the temperature is 39.2F (4.0C). Water becomes less dense as it warms and also less dense as it cools to freezing at 32 F (0C). Then it changes to ice which floats because its density is only 0.917. If ice was not less dense than water, then our lakes would freeze to the bottom and aquatic life as we know it would not be able to survive. Only the most shallow ponds ever freeze solid.