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Lakes Glossary
A
Aerobic
Living in the presence of oxygen. Most organisms are aerobic and must have oxygen available in order to survive.
Algae
Single celled nonvascular plants occurring singly or in groups (colonies). They contain chlorophyll-a, used to produce their own food by means of photosynthesis. Algae form the base of the food chain in aquatic environments.
Algae Bloom
Heavy growth of algae in and on a body of water, often a result of high nutrient concentrations.
Alkalinity
The acid neutralizing capacity of a solution, usually related to the amount of carbonates present; buffering capacity.
Anaerobic
Living in the absence of oxygen. Some bacteria can survive and grow without oxygen present.
Anoxic
No oxygen present in the system; see anaerobic.
C
Catchment Basin
See "Watershed"
Chlorophyll
A green pigment in plants which is used to capture light energy and convert it, along with water and carbon dioxide, into food or organic material.
Chlorophyte (algae)
Bright green algae that occur in lakes as plankton, as well as forming tangled masses of filaments coming up from the lake bottom or near shorelines. This group does especially well in warm water and bright light and is usually abundant in summer. The species are very diverse, including several that look more like grassy aquatic plants than algae. Another species, Botryococcus, turns bright orange under certain conditions, but is not toxic like the marine red tides.
Chrysophyte (algae)
Golden algae that are common members of the plankton in small lakes. They can be solitary or make colonies with large numbers of individuals. Some species make a protective silica sheath around the cells or have a covering of siliceous scales that preserve in lake sediments and have been used for reconstruction studies of past lake environments.
Conductivity
The measure of water’s capacity to convey an electric current. Increasing the numbers of dissolved ions also increases the conductivity.
Cyanobacteria
Bacteria living in lakes and streams that make their own food instead of decomposing dead organisms and are very similar to freshwater algae in lake ecosystems. Many cyanobacteria grow especially well in lakes with high phosphorus content and are sometimes used as indicators of change due to human impacts through watershed development. Several species can make toxins dangerous to humans and other mammals if ingested. High concentrations of these cells in the water can result in closure of lakes to recreation or domestic use of water, although this has been relatively rare in occurrence historically. Also called blue-green algae.
D
Diatom (algae)
Golden-brown algae that make intricate siliceous shells, which are found in lake plankton and attached to wood and rocks along shorelines. Many diatoms grow in cool water and low light, and are often abundant in winter and early spring in temperate lakes. Diatoms are nutritious food for planktonic animals and are important components of a healthy food chain in lakes. The shells preserve well in sediments and can be used in studies of lake history.
Dissolved Oxygen
Oxygen gas dissolved in water.
E
Ecosystem
Any complex of living organisms along with all other factors that affect them and are affected by them.
Epilimnion
The warmer, less dense upper layer of lake water that lies above the lower layers (see metalimnion and hypolimnion) during some seasons.
Euglenoid (algae)
Algae often found in ponds and smaller water bodies, particularly in the warm seasons of the year. They may be bright green, orange or brown. Euglenoid algae are mobile, using a whip-like appendage (“flagellum”) to move through the water. Some make an organic shell that encloses the cell, with the flagellum inserted through a pore.
Eutrophic
Waters in which algae grow into large populations and biovolumes, generally related to nutrient supply. Trophic indicator values above 50 are considered eutrophic.
Eutrophication
The physical, chemical, and biological changes associated with enrichment of a body of freshwater due to increases in nutrients and sedimentation.
F
Fall Turnover
The mixing of thermally stratified waters that commonly occurs during early autumn. The sequence of events leading to a turnover includes: cooling of surface waters leading to a density change in surface water that produces convection currents from top to bottom, and circulation of the total water volume by wind action. Turnover generally results in uniformity of the physical and chemical properties of the water.
H
Humic Substances
Organic substances incompletely broken down by decomposers such as bacteria. Humic acids are large molecular organic acids that are present in water, often giving the water a yellow or brown color.
Hypolimnion
The colder, dense, deep water layer in a thermally stratified lake, lying below the metalimnion and removed from surface influences.
L
Lake
An area permanently inundated by water in excess of two meters (7 ft) deep and greater than twenty acres in size as measured at the ordinary high-water mark.
Lake Level
Water level of a lake in centimeters relative to a given point established when the first King County lake level gauge was installed at the lake.
Level I Lake Stewardship Sampling
An annual volunteer monitoring program managed by the King County Lake Stewardship Program. The program involves daily measurements of precipitation and lake level, as well as weekly measurements of surface water temperature and water clarity, and observations on aquatic plant growth, lake use, and numbers of geese throughout the year.
Level II Lake Stewardship Sampling
A seasonal volunteer monitoring program managed by the King County Lake Stewardship Program. The program involves biweekly measurements of surface water temperature and water clarity, collecting water samples for laboratory analysis, and observations on aquatic plant growth, lake use and numbers of geese from late April through October.
Limnology
The study of lakes and inland waters as ecosystems.
Littoral
Loading
The total amount of material (sediment or nutrients) entering a water body via streams, overland flow, precipitation, direct discharge, or other means over time (usually considered annually). Recycling of nutrients among sediment, organisms and water is sometimes referred to as “internal loading.”
M
Mesotrophic
Waters that promote algae growth at rates intermediate between eutrophy and oligotrophy. Trophic state indicators between 40 and 50 are classified as mesotrophic.
Metalimnion
The layer of water in a lake between the epilimnion and hypolimnion in which the temperature, and thus density, change rapidly over a short distance.
Metals
Elements, such as mercury, lead, nickel, zinc, and cadmium, which are of environmental concern because they do not degrade over time. Although many are necessary nutrients, they are sometimes magnified in the food chain, and they can be toxic to life in high enough concentrations. They are also referred to as heavy metals.
Monomictic
A water pattern of lakes in which thermal mixing and stable stratification alternate once per year.
N
Nitrate, Nitrite (NO3, NO2)
Two types of nitrogen compounds. These nutrients are forms of nitrogen that algae may use for growth.
Nitrification
The biochemical oxidation process by which ammonia is changed first to nitrites and then to nitrates by bacterial action, consuming oxygen in the water.
Nitrogen
One of the elements essential as a nutrient for growth of organisms.
Nitrogen—available
Usually ammonium, nitrite, and nitrate ions, and certain simple amines available for plant growth. A small fraction of organic or total nitrogen in the soil is available at any time.
Non-point source pollution
Pollution from diverse sources difficult to pinpoint as separate entities and thus more complicated to control or manage. Examples of “nonpoint sources” include area-wide erosion (as opposed to landslides or mass wasting), widespread failure of septic systems, certain farming practices or forestry practices, and residential/urban land uses (such as fertilizing or landscaping).
Noxious weeds
A legal definition of by the State of Washington that lists specific non-native, invasive plants known to destroy habitat for other plants or animals, or documented as having caused serious agricultural problems. A list of names is published each year by the Department of Ecology which lists the level of threat posed by the plants and the legal responsibilities of owners who find them growing on their properties. Individual counties may modify the list to fit specific distributions within the county.
NPDES
National Pollutant Discharge Elimination System. The part of the Clean Water Act which requires point source discharges to obtain permits. These permits, referred to as NPDES permits, are administered by the Washington State Department of Ecology.
Nutrients
Essential chemicals needed by plants or animals for growth. Excessive amounts of nutrients can lead to degradation of water quality and algal blooms.
P
pH
The negative logarithm of the hydrogen ion concentration in a solution. This is a measure of acidity. pH decreases as acidity increases. Values below 7 are considered acidic.
Precipitation
Rain or snow. Volunteer lake monitors record daily rain in millimeters (or snow measured in millimeters of water equivalent)..
Pheophytin
A pigment compound resulting from the degradation of chlorophyll a, usually found in algal remains, suspended organic matter, or bottom sediments.
Phosphorus
One of the elements essential for growth and reproduction. Phosphorus is often the limiting or least available nutrient for plant growth in temperate freshwater ecosystems. The primary original source of phosphorus is from the earth in the form of phosphate rocks.
Photic Zone
The upper water in a lake in which light penetrates enough to enable plants to carry out photosynthesis.
Photosynthesis
The production of organic matter (carbohydrates) from inorganic carbon and water, utilizing the energy of light.
Phytoplankton
Free floating microscopic organisms that photosynthesize (algae and cyanobacteria).
Productivity
The production and accumulation of organic matter, usually measured over a certain period of time.
Pyrrhophyte (algae)
These algae, also called dinoflagellates, are solitary and mobile, with two appendages (“flagella”) that move the cell through water using whiplike motions. In marine waters, certain species are known for making toxic “red tides” that can render shellfish poisonous for humans. Freshwater dinoflagellates are not known to produce toxins and, while they may color the water brown or red when abundant, have never been considered dangerous.
R
Residence Time
The average length of time that water or a chemical within the water, such as phosphate, remains in a lake.
Riparian
Pertaining to the banks of rivers and streams, and sometimes also wetlands, lakes, or tidewater.
Runoff
Water originating from rainfall and other precipitation that ultimately flows into drainage facilities, rivers, streams, springs, seeps, ponds, lakes, and wetlands as well as shallow groundwater.
S
Salmonid
A member of the fish family Salmonidae. In King County salmonid species include Chinook, Coho, chum, sockeye, and pink salmon; cutthroat, rainbow, and brown trout and steelhead; Dolly Varden, brook trout, char, kokanee, and whitefish.
Secchi Disk
A 20-cm (8-inch) diameter disk painted white and black in alternating quadrants. It is used to measure the transparency of the water in lakes.
Sediment
Solid material deposited in the bottom of a lake over time.
Shoreline development
The proposed projects regulated by the Shoreline Management Act. Usually this includes the construction over water or within a shoreline zone (generally 200 feet landward of the water) of structures such as buildings, piers, bulkheads, and breakwaters, including environmental alterations such as dredging and filling, or any project which interferes with public navigational rights on the surface waters.
Stratification
The separation of water into nearly discrete layers caused by differences in temperature and subsequent water density differences.
T
TMDL
A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. Water quality standards identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.
Total dissolved solids
The dissolved salt loading in surface and subsurface waters.
Toxic algae
Cyanobacteria (blue-green algae) that is currently producing and/or releasing toxins that can be harmful to people and animals.
Transparency
Water clarity of a lake as measured with a Secchi disk.
Trophic State
A term used to describe the productivity of a lake ecosystem classifying it as one of three increasing categories based on algal biomass: oligotrophic, mesotrophic, or eutrophic. Trophic state indicators are calculated on the basis of total phosphorus, chlorophyll-a and secchi transparency measurements.
Turbidity
Cloudiness in water caused by the suspension of tiny particles (algae or detritus).
Turnover
The mixing of lake water from top to bottom after a period of stable stratification. This typically occurs in fall and is caused by wind and seasonal cooling of surface waters.
W
Water quality
A term used to describe the chemical, physical, and biological characteristics off water, usually in respect to its suitability for a particular purpose.
Watershed
The geographical area that contributes surface and groundwater flow to a stream, lake, or other body of water. This can also be referred to as the “catchment basin” or “drainage basin.”
Watershed Management
The planning and carrying out of actions, legal requirements and protective measures taken by agencies and citizens to preserve and enhance the natural resources of a drainage basin for the production and protection of water supplies and water-based resources.
Water Year (WY)
A division of the earth year based on the general pattern of annual wet and dry periods rather than by calendar months. The U.S. Geological Survey uses the water year of October 1 through September 30 for data analysis.
WRIA
Water Resource Inventory Area.
Z
Zooplankton
Small animals found in the water of lakes that possess limited powers of locomotion, and which feed on bacteria, algae, smaller animals, and organic detritus present in the water..
Numerical terms
303(d) waterbody
A list of lakes, rivers, and streams that have been designated as impaired or threatened by a pollutant(s) for which one or more TMDL(s) are needed. Impaired means that the water is not meeting state water quality standards.