Adding depth to aquatic data in the Northeast Region

One year ago this month, The Nature Conservancy brought together a committee of experts from ten states and the Environmental Protection Agency to take a hard look at various methods used to classify lakes in hopes that a common approach would rise to the surface.

The result: The Northeast Lakes and Ponds Classification System - a refinement of  the Northeastern Aquatic Habitat Classification System.

The new classification and mapping scheme, funded by the North Atlantic Landscape Conservation Cooperative (LCC), is based upon four key variables that are used to organize aquatic natural communities, and importantly, can be mapped consistently across the Region and United States.

The Key Classification Attributes

1. Water temperature - Water temperature dictates which organisms can live and reproduce in a given body of water. Seasonal variations in temperature can act as cues for reproduction and migration, and determine growth rates and fecundity.

2. Trophic state - Measured by the presence of a type of chlorophyll found in green plants and algae, a water body’s trophic level indicates its overall nourishment and ability to support life forms. But diversity is key. While a eutrophic lake is considered a productive ecosystem, a hypereutrophic lake gives rise to excessive growth - meaning fewer lifeforms dominate the entire system.

3. Alkalinity class - The ability of a water body to resist changes in pH from acidic deposition - also known as its buffering capacity - is a measure of its ecological resilience. The more resistant a lake or pond to changes in acidity, the more reliable it is as habitat for organisms that rely on specific environmental conditions.

4. Light penetration - Differentiating between a lake and a pond largely comes down to depth. For a water body to be considered a pond, light must be able to reach the bottom, allowing photosynthesis to occur throughout. Lakes, by contrast, are deeper and darker.

After agreeing with partners on key variables for characterizing water bodies, The Nature Conservancy compiled regional and national lake survey information from states and the EPA’s National Lake Assessment and New England Lake and Pond Survey to create a comprehensive database of sampled bodies of water in the region.  This surveyed information was combined with modeled information for unsurveyed lakes and ponds to complete the mapping.

So what’s the most common type of lake in the Northeast? Warm and eutrophic, with medium alkalinity.