T

TANNINS | a group of refractory dissolved organic carbon compounds that imparts a tea color to water.
THERMAL STRATIFICATION | The formation of layers of different temperatures in a lake or reservoir. Also see stratification.
THERMOCLINE | The middle layer in a thermally stratified lake or reservoir. In this layer there is a rapid decrease in temperature with depth. Also called the metalimnion.
TOTAL LENGTH | Length of a fish from its mouth to the end of its tail.
TOTAL NITROGEN | The sum of all nitrogen forms.
TOTAL PHOSPHORUS | The sum of all phosphorus forms.
TOXIC | Harmful due to poisonous substance.
TROPHIC STATE | State of productivity of a lake (e.g., eutrophic).
TROPHIC STATE INDEX | Measure of the potential for algal or aquatic weed growth. Determined by measuring water clarity, nutrient concentration and algal biomass.
TURBIDITY | Cloudy or murky condition of water, caused by high concentration of suspended solids.
TURNOVER RATE | Flow rate created by a diffuser that allows for the complete circulation of a waterbody. Example: If we use an aerator with a flow rate of 1,500 gpm to circulate a 10 acre-ft pond, we will have a turnover rate of 1.51 circulations (or exchanges) per day.

V

VEGETATIVE FILTER STRIPS | Grass or other vegetation planted to intercept stormwater runoff and remove substantial amounts of sediment, nutrients and contaminants before they enter a body of water

W

WATER COLUMN | The water between the surface and bottom of a lake.
WATER HARDNESS | A measure of the concentration of magnesium and calcium cations in a volume of water.
WATER TABLE | The surface of an aquifer.
WATERSHED | 1. The entire area of land that contributes to or drains into a river or lake. 2. The boundary between two such areas of land.
WETLANDS | An area regularly inundated with water. Characterized by moist soils and a unique community of plants and animals.
WINTERKILL | Fishkill that occurs when a lake is covered with ice and snow and oxygen is depleted due to the elimination of photosynthetic oxygen production and atmospheric oxygen exchange.

Y

YEAR CLASS | All the fish (or other organisms) in a stock born in the same year.
YOY | Young of year; refers to fish (or other organism) that are less than a year old.

Z

ZOOPLANKTON | Small, usually microscopic animals (or protists) found in lakes and rivers. Floating organisms that live suspended in a water body.