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This glossary is courtesy of http://pearl.maine.edu- a GIS searchable database on Maine lakes and other environmental resources of the great State of Maine. PEARL was created by the University of Maine, and is maintained by the Senator George J. Mitchell Center for Environmental and Watershed Research at the University of Maine in collaboration with UMaine Fogler Library, James Sewall Company of Old Town, Dept of Spatial Engineering, and the Maine Lakes Conservancy Institute. Funders include the Mitchell Center, Maine Department of Environmental Proection, the Maine Drinking Water Program, Maine Volunteer Lake Monitoring Program, State Planning Office, National Science Foundation, and other state and federal partners. A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z ALGAE: Algae are microscopic plants either suspended in water or attached to rocks and other surfaces. Alga abundance, in open waters, can influence the lake transparency (water clarity). Algae are an essential part of the lake ecosystem and provide the food base for most lake organisms, including fish. ALGAL BLOOM: An algal bloom occurs when certain species of algae reproduce rapidly, reducing the visibility of the lake water to less than 2 meters (6.6 feet). The lake appears very green or blue-green. As the algae die off, scums can be formed that smell and add a bad taste to the lake water, but are not necessarily toxic or harmful to humans. Fish may die as a result of an algal bloom that lowers the oxygen concentration in the water. ALKALINITY: Alkalinity is a measure of the capacity of water to neutralize acids and is also known as the buffering capacity. It is due primarily to the presence of naturally available bicarbonate, carbonate, and hydroxide ions. APPARENT COLOR: The amount of "color" in a lake refers to the concentration of natural dissolved organic acids such as tannins and lignins, which give the water a tea color. Tannins and lignin’s usually come from aquatic plants that live in the lake or in the drainage to the lake. They are not considered harmful. Apparent color is measured by comparing an unfiltered water sample to Standard Platinum Units (SPU). AQUATIC INVERTEBRATES: Aquatic invertebrates are animals without an internal skeletal structure such as insects, mollusks, and crayfish. Common invertebrates in lakes include mayfly larvae, snails, and freshwater mussels (clams) etc. AZIDE: A compound containing the group N3 combined with an element or radical. BASIN: Most lakes only have one basin but in a few cases a lake may have more than one deep area scoured out creating distinct basin areas in the same lake. Although basins within the same lake often have similar water quality they can be quite different depending on shape, immediate watershed characteristics and hydrology (movement of water). BOTTOM GRAB SAMPLE (BG): A sample of water is taken at a specific depth or location in the water column. A bottom grab sample is usually taken 1 to 2 meter(s) [3.2 to 6.6ft.] above the bottom of the lake. CHL A: See Chlorophyll a CHLOROPHYLL A: CHLOROPHYLL A (Chla) is a measurement of the green pigment found in all plants including microscopic plants such as algae. It is used as an estimate of algal biomass of algae. COLDWATER FISH: These species of fish need well oxygenated, coldwater found in the deep waters of lakes and occasionally by stream mouths and spring holes, in order to survive during the summer months. When an abundance of decomposing algae or other dead material uses the limited oxygen in the deep waters, the coldwater fishery could be stressed or eliminated. Examples of coldwater fish include salmon, lake trout, and brook trout. COLOR: See apparent color. CONDUCTIVITY: Conductivity is a measure of the ability of water to carry an electrical current and is directly related to the dissolved ions (charged particles) present in waters. Conductivity will often increase if there is an increase in pollutants entering the lake or pond. CORE: A core sample is a vertical sample of the water column obtained by using flexible plastic tubing, usually ½ inch in diameter. The tubing is lowered to the desired depth, clamped at the water’s surface, raised, and then the sample is decanted into a collection jug. This water sample may be tested for Chlorophyll, Total Phosphorus, pH, conductance, color and alkalinity. DIRECT DRAINAGE BASIN: The direct drainage basin (area) is the land over which water runs on its way to one lake. DISSOLVED OXYGEN: The amount of oxygen measured in the water. Used by aquatic organisms for respiration. The higher the temperature the less oxygen the water can hold. Oxygen will naturally decline during the summer months as water temperatures rise. The late summer temperature and dissolved oxygen profiles represent the lake's most stressed period. DRAINAGE BASIN: The total drainage basin (area) includes both the direct drainage basin and the area draining to upstream lake(s). EPILIMNETIC CORE SAMPLE (EPI Core): epilimnion (top layer of water). See Core sample. EPILIMNION: The epilimnion is the top layer of lake water that is directly affected by seasonal air temperature and wind. This layer is well oxygenated by wind and wave action except times when the lake is covered by ice. EUPHOTIC ZONE: When humans pollute the lake they speed up the natural evolution of the lake decreasing the water quality, resulting in less biodiversity, high levels of phosphorus, algal blooms, loss of cold water fish and Secchi disk transparencies of 4.0 m or less. FLUSHING RATE: The Flushing rate refers to how often the water in the entire lake water is replaced. The ratio of drainage area runoff to lake volume determines the flushing rate. A lake with a fast flushing rate is less sensitive to changes in its nutrient loading than one with a slow flushing rate. Slow flushing rates give nutrients a chance to settle to the bottom and be recycled within the water column. GRAB SAMPLE: Grab samples are taken just below the surface or with a depth sampler at a specified depth or location in the water column (i.e. grab samples might be taken at 1 meter intervals in the epilimnion of the lake or at 10 meters 20 meters depending on how deep the lake is). GREAT PONDS: Defined in Maine law as natural lakes more than 10 acres in size or human-made impoundments more than 30 acres in size. HECTARE (HA): Hectare is a metric unit of land area. It equals 10,000 square meters (m2 ) or 2.47 acres. HOMOTHERMOUS LAKE: The entire lake is the same temperature from top to bottom. In deep lakes, homothermous water occurs in spring and fall. Many shallow lakes are homothermous all the time except when the surface is covered with ice. HYDROLOGIC CYCLE: The sequence of conditions through which water passes from vapor in the atmosphere through precipitation upon land or water surfaces and ultimately back into the atmosphere as a result of evaporation and transpiration. HYDROLOGY: Science dealing with the properties, distribution, and circulation of water on and below the earth's surface and in the atmosphere. HYPOLIMNION: Refers to the deepest, coldest, most dense layer of water in a stratified lake (layers of water differing in temperature and density). This layer may contain less Dissolved Oxygen (D.O.), especially in late summer. I J KILOMETERS (KM2): A metric land measurement that is equal to one million square meters (m2 ), 100 hectares (ha) or 0.39 square miles. LAKE: A permanent, inland body of standing water with no sustained directional flow detectable to the naked eye. In general, a lake has sufficient depth that light does not penetrate all the way to the bottom in the deepest parts of the lake and often stratifies into three distinct layers of water during the summer. Ponds by contrast, have light penetration throughout the body of water and will have only one or two layers during stratification. In Maine, this general rule of distinguishing lakes from ponds was not used in naming the bodies of water. LIMITING FACTOR: The nutrient or condition in shortest supply usually referring to growth. Plants will grow until stopped by this limitation; for example, phosphorus is typically limiting in summer and temperature or light is limiting in fall or winter. LIMNOLOGY: Limnology is the study of the geological, biological, chemical, and physical characteristic of fresh water. MACROPHYTES: Macrophytes are rooted plants or higher (multi-celled) plants that grow in or near water. Macrophytes are beneficial to lakes because they produce oxygen and provide habitat for fish, reptiles, aquatic insects and other animals. Macrophytes can grow to nuisance levels under conditions of high siltation (filling in with fine soil particles) from erosion, excessive nutrient levels or introductions of exotic, aggressive species. MEROMICTIC: Meromictic describes a lake (usually extremely deep, or deep and well protected from wind) which is permanently stratified (having layers of water of different densities). The water in this type of lake does not circulate completely at any time during the year. MESOTROPHIC: The term mesotrophic describes a middle stage between oligotrophic (low productivity) and eutrophic(very productive). This type of lake has intermediate levels of phosphorus and chlorophyll, and Secchi disk transparencies of 4m to 8m (13.3 to 26.5 ft.). METALIMNION: The metalimnion or middle layer of the water column, separates the epilimnion (top layer) from the bottom layer (hypolimnion). This layer is the zone of temperature change from warm surface waters to cooler bottom waters. MIDAS NUMBER: A four-digit code assigned to uniquely identify each lake in Maine. MORPHOMETRY: Morphometry refers to the physical characteristics of a lake such as size and shape of a lake basin, mean depth, maximum depth, volume, drainage area, and flushing rate. NONPOINT SOURCE (NPS): NPS describes a type of pollution that comes from many small sources, such as rain flowing over a lawn. NPS is a source of unwanted nutrients to a lake or other water body. Examples are agricultural and urban runoff, malfunctioning septic tanks, and erosion from forestry, agriculture and development (including individual homes and lawns around lakeshores). NUTRIENTS: Chemical elements, such as phosphorus and nitrogen, necessary to the growth and survival of lake plants and algae. OLIGOTROPHIC:: Refers to a class of lakes that exhibit low productivity, low levels of phosphorus and Chla, few rooted aquatic plants and algae, deep transparency readings [ 8.0 m (26.5 ft) or greater] and usually high dissolved oxygen levels throughout the water column. These lakes are considered to have excellent water quality. PARTS PER BILLION (PPB): µl= micro grams per liter: Is a unit of measurement of a substance in the water. For example if you are talking abut 10 ppb phosphorus in a lake that means in one billion "drops" or parts of water, there are 10 "drops" or parts of phosphorus. PARTS PER MILLION (PPM): mg= milligram per liter: Is a unit of measurement of a substance in the water. For example, if you are talking about 8 ppm dissolved oxygen in a lake, that means in one million "drops" or parts of water there are 8 "drops" or parts of oxygen. pH: The pH of a lake describes either how acidic or basic the water is and helps influence which plant and animal species are present. The measure of the acidity, is on a scale of 1-14, with 7 being neutral, below 7 is considered acidic, and above 7 is alkaline. PHAEOPHYTIN: A non-photosynthetic accesory pigment present in algae. PHOSPHORUS: Total Phosphorus (TP) is one of the major nutrients needed for plant growth. It is generally present in small amounts and limits the plant growth in lakes. Generally, as phosphorus increases, the amount of algae also increases. PHOSPHORUS EPILIMNECTIC CORE (PEC): A core sample taken for in the epilimnion (upper layer of water) to measure the Total Phosphorus in the water. (See epilimnetic Core Sample). PHYTOPLANKTON: Phytoplankton are floating or weakly mobile microscopic aquatic plants (algae). POINT SOURCE (POINT SOURCE POLLUTION): Point sources or point source pollution are direct pollutant discharges of wastewater to lakes or other water bodies that can be specifically identified such as a pipe discharge. Examples of point discharges are industries, mills, Laundromats, fish hatcheries, and sewage outfalls. POND: A permanent, inland body of standing water with no sustained directional flow detectable to the naked eye. Ponds have light penetration all the way across the body of water and will have only one or two layers during summer stratification. Lakes by contrast, have sufficient depth that light does not penetrate all the way to the bottom in the deepest parts of the lake and often stratifies into three distinct layers of water during the summer. In Maine, this general rule of distinguishing lakes from ponds was not used in naming the bodies of water. Therefore some ponds are called lakes and some lakes are called ponds. PROFILE GRAB SAMPLES: A series of samples, which are taken at, specified depths from top to bottom at a sampling location. PROFILE OF GRAB SAMPLES: Samples are taken at specified depths then mixed to obtain a composite sample. Usually done in the epilimnion of the lake. Q R SAMPLE STATION: Location where water quality readings and samples are taken. Some of the larger lakes or basins are sampled at more than one location, resulting in multiple station numbers. In lakes with more than one basin, at least one station is usually located in each basin. SECCHI DISK: A Secchi disk is a weighted circular plate, 8 inches in diameter with opposing black and white quarters painted on the surface and black on the bottom. It is used to determine the clarity or transparency of the water. It is attached to a line that is marked in meters and is lowered until it disappears from sight. The Secchi depth is the distance from the surface of the lake to the point the disk disappears. SECCHI DISK TRANSPARENCY: Secchi disk transparency is a measure of the water clarity, or transparency, of the lake. At this site on the web, Secchi disk readings are reported in meters [1 meter (m) = 3.28 feet]. Factors that reduce clarity include algae, zooplankton, watercolor and particles such as silt. Since algae have the greatest effect on clarity, measuring transparency indirectly measures the algal productivity. Secchi disk readings can be used to track changes in water quality over time. Transparency values in Maine vary from 0.4 m (1.5 ft) to 20.0 m (67 ft), with the average being 4.9 m ( 16 ft). SEDIMENTS: Lake-bottom sediments are the minerals and partially decayed organic materials that accumulate on lake bottoms. Much of these materials washes into the lakes from erosion in the lake watershed or are the remains of algae produced in the lake. STANDARD PLATINUM UNIT (SPU): SPU is a unit of measurement used to determine the color of lake water. Lake water with 30 SPU color will look slightly brown or tea-colored. STRATIFICATION: In Maine lakes, during warm weather, two or three horizontal layers will develop in most lakes from top to bottom. These layers will have different characteristics such as temperature and density. The top layer or epilimnion, is the least dense and warmest, the bottom layer or hypolimnion is the most dense and coolest, and the middle layer or metalimnion is the layer of transition in the middle. During the summer months these layers do not mix unless a strong, prolonged wind occurs. THERMOCLINE: The thermocline is the uppermost point in the water column where the temperature drops at least a degree Celsius per meter of depth. It usually defines the upper point of the metalimnion. TOTAL DRAINAGE AREA (BASIN) OR TOTAL WATERSHED:: See Drainage Area TROPHIC: Trophic State Index: (TSI or TS) is a scale from 0 to 100+, which ranks lakes for productivity. The low (zero) end of the scale supports very little algae, has excellent water quality (oligotrophic) and the high end 100+ is eutrophic and very productive. TSI can be calculated from the Secchi disk, Chla or total phosphorus results and requires at least five months of data per year. Lakes with TSI values greater than 65 may support algal blooms while values over 100 indicate extreme productivity and annual algae blooms. TSI values can be used to compare lakes with similar water color and track water quality trends within a lake. TRUE COLOR: The amount of "color" in a lake refers to the concentration of natural dissolved organic acids such as tannins and lignin’s, which give the water a tea color. True color is measured by comparing a filtered water sample to Standard Platinum Units (SPU). TS: See Trophic State Index TSI: See Trophic State Index TURNOVER: Turnover is a thorough mixing of stratified layers of lake water, usually in the spring and fall, when temperatures become uniform throughout the lake. U V WARMWATER FISH: Species of fish that do not require deep cool waters of lakes to survive summer heat. Examples are bass, perch, pike, and pickerel. These species are often found in mesotrophic and eutrophic lakes in Maine. WATERSHED: See also: Drainage Basin. How a Watershed Works ZOOPLANKTON: Zooplankton are floating or weakly mobile microscopic or barely visible aquatic animals that eat algae.