Conservation and Management
Oligotrophic 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 spiny water flea (Bythotrephes longimanus), Chinese mystery snail (Cipangopaludina chinensis), Asian clam (Corbicula fluminea), zebra mussel (Dreissena polymorpha), Chinese mitten crab (Eriocheir sinensis), Eurasian watermilfoil (Myriophyllum spicatum), brittle naiad (Najas minor), virile crayfish (Orconectes virilis), curly leafed pondweed (Potamogeton crispus), European fingernail clam (Sphaerium corneum), and banded mystery snail (Viviparus georgianus). In addition, alteration to the natural hydrology (e.g., impoundments, dredging) and reduction in water quality (e.g., siltation, trash, turbidity, septic/nutrient run-off) are threats to oligotrophic dimictic lakes. Atmospheric deposition of pollutants (e.g., acid rain and heavy metals) is a particular threat to some oligotrophic dimictic lakes, especially in the Adirondack Mountains (Jenkins et al. 2005). Although most lakes are recovering from historical DDT impacts, there is the potential threat that the proposed use of herbicides to control exotic plants (e.g., SONAR) may affect non-target native species.
Conservation Strategies and Management Practices
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.
Development and Mitigation Considerations
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 oligotrophic dimictic lakes. A statewide review of oligotrophic 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 oligotrophic dimictic lakes statewide in order to characterize variations. Continued research is needed on the impacts that atmospheric deposition has on this community. Four to seven ecoregional variants are suspected to differ in dominant and characteristic vascular plants, fishes, mollusks, and insects. More data on regional variants are needed.
- Aeshna clepsydra (Mottled Darner)
- Apalone spinifera (Spiny Softshell)
- Gavia immer (Common Loon)
- Hippuris vulgaris (Mare's Tail)
- Isoetes riparia (Riverbank Quillwort)
- Notropis bifrenatus (Bridle Shiner)
- Notropis heterodon (Blackchin Shiner)
- Potamogeton alpinus (Red Pondweed)
- Potamogeton pulcher (Spotted Pondweed)
- Rhionaeschna mutata (Spatterdock Darner)
- Valvata sincera (Mossy Valvata)