Eutrophic lakes are relatively rich in nutrients; generally more nutrient rich than oligotrophic or mesotrophic lakes; they have high concentrations of plant nutrients, such as nitrogen and phosphorus, and support high plant productivity. Dimictic lakes turn over twice a year, during the spring and the fall. This remixes dissolved oxygen and nutrients, needed by plants and animals in the lake. In the fall, the surface water becomes cooler and denser than the bottom waters. This cooler water sinks to the bottom, mixing the lake water. In the winter as temperatures drop further, ice forms on top of the lake and stops any further mixing. During the spring, the lake is heated by the sun and the cooler, less dense water floats to the top and the warmer, denser water extends to the bottom. As summer progresses, the temperature and density differences between upper and lower water layers become more distinct. These lakes generally become physically stratified into three identifiable layers in the summer and winter.
There are a few hundred occurrences statewide and currently includes bays and coves of larger lakes, such as Hyde Bay and Blackbird Bay in Otsego Lake. Very few occurrences are presumed to have good viability and are protected on public land or private conservation land. This community has statewide distribution, and includes several large, high quality examples. The current trend of this community is probably stable for actively protected/managed lakes, or declining slightly elsewhere due to moderate threats related to watershed development, invasive aquatic species, and alteration to the natural hydrology.
The numbers and acreage of eutrophic dimictic lakes in New York have probably remained stable in recent decades as a result of wetland protection regulations. However, the condition of some of these lakes may have declined slightly to moderately due to the spread of invasive aquatic species. There may be a few cases of slight decline due to alteration of hydrology (e.g., ditching and impoundments) and reduced water quality from nutrient input from surrounding developed uplands.
The numbers and acreage of eutrophic dimictic lakes in New York have probably declined moderately from historical numbers likely correlated to alteration of hydrology (e.g., ditching and impoundments) and reduced water quality from nutrient input from surrounding developed uplands (e.g., excessive stormwater input, siltation, pollution).
Where practical, establish and maintain a lakeshore buffer to reduce storm-water, pollution, and nutrient run-off, while simultaneously capturing sediments before they reach the lake. Buffer width should take into account the erodibility of the surrounding soils, slope steepness, and current land use. If possible, minimize the number and size of impervious surfaces in the surrounding landscape. Avoid habitat alteration within the lake and surrounding landscape. For example, roads should not be routed through the lakeshore buffer area. If a lake must be crossed, then bridges and boardwalks are preferred over filling and culverts. Restore lakes that have been affected by unnatural disturbance (e.g., remove obsolete impoundments and ditches in order to restore the natural hydrology). Prevent the spread of invasive exotic species into the lake through appropriate direct management, and by minimizing potential dispersal corridors.
Eutrophic dimictic lakes are threatened by shoreline development and its associated run-off (e.g., residential, commercial, agricultural, and roads), recreational overuse (e.g., powerboats, intensive fish stocking and removal), and habitat alteration in the adjacent landscape (e.g., excessive land clearing, pollution run-off, and increased impervious surfaces within the watershed). Many of these lakes are threatened by the spread of aquatic invasive species, such as alewife (Alosa pseudoharengus), mud bithynia (Bithynia tentaculata), goldfish (Carassius auratus), fishhook waterflea (Cercopagis pengoi), common carp (Cyprinus carpio), quagga mussel (Dreissena bugensis), zebra mussel (Dreissena polymorpha), Eurasian watermilfoil (Myriophyllum spicatum), round goby (Neogobius melanostomus), starry stonewort (Nitellopsis obtusa), rusty crayfish (Orconectes rusticus), curly leafed pondweed (Potamogeton crispus), and water chestnut (Trapa natans).
Where practical, establish and maintain a lake shore buffer to reduce storm-water, pollution, and nutrient run-off, while simultaneously capturing sediments before they reach the lake. Buffer width should take into account the erodibility of the surrounding soils, slope steepness, and current land use. If possible, minimize the number and size of impervious surfaces in the surrounding landscape. Avoid habitat alteration within the lake and surrounding landscape. For example, roads should not be routed through the lake shore buffer area. If portions of a lake must be crossed, then bridges and boardwalks are preferred over filling and culverts. Restore lakes that have been affected by unnatural disturbance (e.g., remove obsolete impoundments and ditches in order to restore the natural hydrology). Prevent the spread of invasive exotic species into the lake through appropriate direct management, and by minimizing potential dispersal corridors.
When considering road construction and other development activities, minimize actions that will change what water carries and how water travels to this lake community, both on the surface and underground. Water traveling over-the-ground as run-off usually carries an abundance of silt, clay, and other particulates during (and often after) a construction project. While still suspended in the water, these particulates make it difficult for aquatic animals to find food; after settling to the bottom of the lake, these particulates bury small plants and animals and alter the natural functions of the community in many other ways. Thus, road construction and development activities near this lake type should strive to minimize particulate-laden run-off into this community. Water traveling on the ground or seeping through the ground also carries dissolved minerals and chemicals. Road salt, for example, is becoming an increasing problem both to natural communities and as a contaminant in household wells. Fertilizers, detergents, and other chemicals that increase the nutrient levels in lakes cause algae blooms and eventually an oxygen-depleted environment where few animals can live. Herbicides and pesticides often travel far from where they are applied and have lasting effects on the quality of the natural community. So, road construction and other development activities should strive to consider: 1. how water moves through the ground, 2. the types of dissolved substances these development activities may release, and 3. how to minimize the potential for these dissolved substances to reach this natural community.
Resurvey known occurrences and search for new occurrences statewide to advance documentation and classification of eutrophic dimictic lakes. A statewide review of eutrophic dimictic lakes is desirable. Continue searching for large lakes in good condition (A- to AB-ranked). Review and incorporate data on occurrences in NY gathered by the Adirondack Lakes Survey Corporation, the Adirondack Park Invasive Plant Program, and the New York State Federation of Lake Associations, Inc.
There is a need to research the composition of eutrophic dimictic lakes statewide in order to characterize variations. Three to six ecoregional variants are suspected to differ in dominant and characteristic fishes, mollusks, and insects. More data on aquatic macrophytes and macroinvertebrates, as well as regional variants, are needed. Research is needed to inform the classification of the eutrophic bays along the margins of larger oligotrophic dimictic lakes (e.g., Hyde Bay and Blackbird Bay in Otsego Lake).
This community is sparsely scattered, but widespread throughout New York State, usually at low elevations and includes the following lakes: Canandarago Lake, Otsego County; Honeoye Lake, Ontario County; Onondaga Lake, Onondaga County; Saratoga Lake, Saratoga County; Streeter Lake, St. Lawrence County; Chodikee Lake, Ulster County.
This broadly-defined community may be worldwide. Examples with the greatest biotic affinities to New York occurrences are suspected to span north to southern Canada, west to Minnesota, southwest to Indiana and Tennessee and southeast to North Carolina.
The aquatic community of a nutrient-rich lake that occurs in a broad, shallow basin. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall); they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter. A name change and slight conceptual change to alkaline dimictic lake is being evaluated. Profundal and pelagic species assemblages are usually well developed. Usually there are many species of fish, especially minnows (Cyprinidae). Characteristic fishes are warmwater fishes such as yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides), chain pickerel (Esox niger), bluegill (Lepomis macrochirus), pumpkinseed (L. gibbosus), yellow bullhead (Ictalurus natalis), brown bullhead (I. nebulosus), white sucker (Catostomus commersoni), golden shiner (Notemigonus crysoleucas), common shiner (Luxilus cornutus), northern redbelly dace (Phoxinus eos) and stocked white perch (Morone americana). Two additional species that are characteristic of eutrophic lakes on Long Island are eastern mudminnow (Umbra pygmaea) and pirate perch (Aphredoderus sayanus). The abundant profundal benthos is poor in species, including only species tolerant of low oxygen; characteristic profundal invertebrates are oligochaetes (Oligochaeta), larvae of midges (Chironomus spp.), and phantom midges (Chaoborus spp.). Phytoplankton and zooplankton are usually abundant, but there are only a few species present; characteristic phytoplankton are cyanobacteria (blue-green algae); other characteristic plankton may include the phytoplankton Ceolosphaerium, Dinobryon, and Asterionella, and the zooplankton Bosmina, Keratella, Diaptomus, and Daphnia dubia. Aquatic macrophytes are abundant in shallow water, and there are many species present, but species diversity is generally lower than in mesotrophic lakes. Characteristic plants include tapegrass (Vallisneria americana), pondweeds (Potamogeton spp.), bur-reeds (Sparganium spp.), and the floating aquatic plants white water-lily (Nymphaea spp.), yellow pond-lily (Nuphar luteum), and water-shield (Brasenia schreberi). Typically these are the lakes with nuisance problems of exotic plants such as Eurasian water milfoil (Myriophyllum spicatum), water chestnut (Trapa natans), and pondweed (Potamogeton crispus).
Characteristic features of a eutrophic lake include the following: yellow, green, or brownish-green water that is murky, with low transparency (Secchi disk depths typically less than 2.5 m, but up to 4 m in some cases); water rich in plant nutrients (especially high in phosphorus, nitrogen and calcium); high primary productivity (inorganic carbon fixed = 75 to 250 g/m2/yr); lake sediments that are rich in organic matter (usually consisting of a fine organic silt or copropel); water that is well-oxygenated above the summer thermocline, but oxygen-depleted below the summer thermocline or under ice; epilimnion volume that is relatively large compared with hypolimnion; and a weedy shoreline. Alkalinity is typically high (greater than 12.5 mg/l calcium carbonate).
Known examples of this community have been found at elevations between 1,469 feet and 1,487 feet.
Eutrophic dimictic lakes can be easily observed from the shoreline where there is public access, or by boat in mid- to late summer when fragrant white water lily and spatter dock are in bloom in the shallow areas.
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Cole, G.A. 1979. Textbook of limnology. The C.V. Mosby Co., Saint Louis, MO.
Edinger, G. J., D. J. Evans, S. Gebauer, T. G. Howard, D. M. Hunt, and A. M. Olivero (editors). 2014. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke’s Ecological Communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation, Albany, NY. https://www.nynhp.org/ecological-communities/
Maitland, P.S. 1978. Biology of fresh waters. John Wiley, and Sons, New York.
New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.
Nichols, W. F. 2015. Natural Freshwater Lakes and Ponds in New Hampshire: Draft Classification. NH Natural Heritage Bureau, Concord, NH.
Olivero-Sheldon, A. and M.G. Anderson. 2016. Northeast Lake and Pond Classification. The Nature Conservancy, Eastern Conservation Science, Eastern Regional Office. Boston, MA.
Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.
This guide was authored by: Gregory J. Edinger
Information for this guide was last updated on: June 23, 2023
Please cite this page as:
New York Natural Heritage Program. 2023.
Online Conservation Guide for
Eutrophic dimictic lake.
Available from: https://guides.nynhp.org/eutrophic-dimictic-lake/.
Accessed October 3, 2023.