acid: substance with pH less than 7.0; acidity is caused by high concentrations of hydrogen ions

acid rain: rainwater carrying acidic atmospheric pollutants (nitrous or sulfuric oxides)

alevin: newly hatched fish with yolk sac attached, larva

alkaline: substance with pH greater than 7.0; alkalinity is caused by high concentrations of hydroxyl ions; basic

anadromous fish: fish that migrate from salt water to fresh water for spawning

aquatic: refers to water aquatic insect: insect species whose larval stages live in water

basic: alkaline

benthic: refers to the bottom of a body of water benthic macroinvertebrates: spineless animals that inhabit the bottom of streams and lakes; visible to the eye; aquatic worms, snails, clams, immature stages of aquatic insects

biochemical oxygen demand(BOD):  the amount of oxygen used up in biological decomposition and chemical oxidation of sediment, water, or effluent

boulders: rocks larger than 30 an (12 inches) in diameter

canopy: upper layer formed by trees

carrying capacity: number of organisms a habitat can support throughout a year without damaging organisms or habitat

coarse particulate organic matter (CPOM): leaf and fine woody debris >1 mm in diameter

cobble: rock from 7 to 30 an (3 to 12 inches) in diameter; rubble

collectors: aquatic invertebrates that feed on fine material

community: the plants and animals that interact in a habitat; the community of people who influence a habitat

coniferous: cone-bearing trees with needles

consumers: organisms that depend on other organisms for their food

cover: vegetation or other features that provide shelter for wildlife

deciduous: trees that shed their leaves in fall

decomposition: breakdown of organic materials

deposition: depositing of material by a stream, generally at points of reduced stream flow

discharge: the amount of water flowing past a given point on a stream; measured in cubic feet or cubic metres per second

dissolved oxygen: oxygen dissolved in water; the amount depends on water temperature, plant photosynthesis, plant and animal respiration, and physical aeration

dissolved solids: solid (generally inorganic) material in solution

diversity: number of species in a particular community or habitat

drainage basin: watershed

ecosystem: the organisms, physical environment, and climate in a given area

effluent: waste liquid from a house, industry, sewage treatment plant, etc.

engulfers: predators that eat their prey whole

ephemeral streams: ones that flow only during and shortly after extreme rainfall or snowmelt

erosion: movement of soil by water and wind

evaporation: conversion of water from liquid to vapour

evapotranspiration: water lost from plants through evaporation and photosynthesis

filtering collectors: aquatic invertebrates that feed by filtering small organic particles from the water

fine particulate organic matter (FPOM): organic material <1 mm in diameter

first-order stream: stream with no tributaries

fish ladder: a stepped fishway with water flowing over it

flood: stream flow greater than the channel can contain

floodplain: area along a stream or river subject to flooding; often the location of human development

freshet: a sharp rise in discharge or a flood event associated with rainfall or snow melt

fry: recently emerged fish, after the yolk sac has been absorbed

functional feeding groups: classification of aquatic invertebrates by their feeding method

gathering collectors: aquatic invertebrates that feed on particles on the bottom of a stream

gradient: degree of slope, or steepness of a geographic feature

gravel: rock 0.5 to 7 cm (0.2 to 3 inches) in diameter

ground water: water that sinks into the soil and collects over impermeable rode; it then flows laterally toward a stream, lake or ocean.

habitat: an area that provides food, water, and shelter for an organism

headwaters: unbranched tributaries of a stream

herbaceous: plants with soft rather than woody stems

humus: decayed organic matter in or on the soil

infiltration: drainage of water through soil

intermittent stream: one that does not flow year-round

invertebrate: an animal without a back bone

ion: an electrically charged atom or molecule

larva: immature stage in a life cycle between egg and adult limiting factors: conditions that establish a population or range of a species

mg/l: milligrams of a substance per litre of water, parts per million (ppm)

midreaches: streams carrying the water from several tributaries

milt: sperm-filled milky substance released by male fish to fertilize eggs

monitor: track a characteristic over time, using uniform methods to evaluate change non-point source pollution: pollutants that enter waterways from broad land areas as a result of the way the land is used (e.g. sedimentation, runoff)

nymph: immature form of insects such as stoneflies and mayflies that do not pupate

perennial streams: ones that flow throughout the year

periphyton: algae growing on surfaces in a stream, lake, or ocean

pH: measure of the hydrogen ion activity; measures the acidity or alkalinity of a solution: the pH scale ranges from 1 (strong add) to 14 (strong base), with 7.0 as neutral

piercers: predators that feed by sucking fluids out of their prey

plankton: microscopic plants and animals suspended in the water

point source pollution: air or water pollutants entering the environment from a specific source

pool: deeper and slower flowing water in a stream or river

population: group of individuals of a specific kind, in a given area, at a given time

ppm: parts per million or milligrams per litre (mg/l)

precipitation: rain, snow, hail, or sleet falling to the ground

predator: an animal that hunts and kills other animals for food

primary production: organic material produced by plants from inorganic material and sunlight

producers: plants that manufacture food from inorganic nutrients

pupa: stage of a life cycle between larva and adult

reach: a stream section with fairly homogenous characteristics

rearing habitat: places in a stream that provide food, resting places, and shelter for young fish

redd: a nest in the streambed in which salmon and trout lay their eggs; the eggs incubate, then hatch in the gravel

riffle: relatively fast flowing, shallow water in a stream

riparian area: the border of the stream above its banks; wet soil areas influenced by the water of a stream, lake, or wetland

riparian area of influence: transition area between riparian area and upland vegetation

riprap: rock covering used to protect stream banks from erosion

river continuum:  a conceptual model explaining changes in composition of aquatic invertebrate communities in streams and rivers

run: a part of the stream with smooth, slow to moderate flow, deeper than a riffle

salmonid: a fish of the Salmonidae family (salmon, trout, char)

scrapers: aquatic invertebrates that feed by scraping the surface of rocks for algae

secondary production: material that is transformed by consumers (eaten or decomposed)

shredders: aquatic invertebrates that feed on leaves or twigs that fall into a stream

silt: tiny, fine particles suspended in or deposited by water

siltation: the process of becoming clogged by fine sediments

smolt: a juvenile anadromous fish that has undergone physical changes to prepare for life in saltwater

spawning: laying and fertilizing eggs spawning habitat: parts of a stream or lake that provide suitable areas for fish to spawn; usually gravel beds

streambed: part of the stream over which water moves; substrate

stream order: a system used to classify (and analyze) streams

stream flow: volume of water carried by a stream

substrate: inorganic material that forms the streambed

suspended sediments: particles carried in water without being dissolved

terrestrial: living on land

turbidity: degree to which light penetration is blocked because water is cloudy; measure of sediment suspended in water

water table: upper level at which the soil is saturated with water

watershed: all the land area that drains into a particular body of water

wildlife: any animal that is not tamed or domesticated