Biochemical oxygen demand (or biological oxygen demand) – amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage; measures water pollution
Dissolved oxygen – amount of oxygen in fresh water such as a stream or freshwater lake
Emergent plant – a plant rooted in shallow water with much of the stem and most of the leaves above water
Euphotic zone – zone of water in a sea or lake where sufficient light penetrates to allow photosynthesis; zone depth is limited by water clarity
Eutrophic lakes –rich in plant nutrients and thus produces high numbers of phytoplankton (suspended algae) which often cloud the water so that poor Secchi disk readings (average about 8 feet) are expected; also produces high numbers of zooplankton and minnows and other small fish that feed on the zooplankton
Limnetic zone – open water of a pond or lake supporting plankton growth; shallower in turbid water than in clear and a more prominent feature of lakes than ponds; dominated by floating microorganisms called plankton and actively swimming animals called nekton
Littoral zone – portion of a fresh water body extending from the shoreline outward to the limit of occupancy of rooted plants; also the strip of land along the shoreline between the high and low water levels
Oligotrophic lakes – possess low nutrient concentrations and low plant growth; phytoplankton, zooplankton, attached algae, aquatic weeds, bacteria and fish are small populations
pH scale – measure of a liquid’s or solid’s alkalinity, represented on a scale of 0 to 14 with 7 being a neutral state, 0 the most acidic and 14 the most alkaline
Submerged plant – grow underwater, rooted in the bottom and have stems that grow toward the surface