The Effects of Watershed and Stream Liming on Mercury Dynamics at Honnedaga Lake Active

Problem

The Adirondack region of New York has 128 lakes that are listed as impaired by acidity under section 303(d) of the Clean Water Act. Acidity can limit the survival and reproduction of native fishes such as brook trout (Salvelinus fontinalis). Chronic and episodic acidification also stresses fish, aquatic macroinvertebrates, and other biota of inflowing tributaries of these and many additional lakes. Acidification of these tributaries can also affect the health of fish populations in receiving lakes, by limiting suitable spawning and nursery habitat.

Although many Adirondack lakes have shown decreased acidity resulting from decreases in atmospheric sulfur and nitrogen emissions, the ecological improvements thus far have not matched those observed in atmospheric deposition. A recent analysis of the potential recovery of Adirondack lakes indicates that approximately 30% of impaired lakes will fail to recover even under a scenario of a 100% decrease in anthropogenic sulfur and nitrogen deposition. These unrecoverable lakes are either naturally acidic and/or are highly sensitive to acidic deposition, and the soils within their watersheds have been acidified to the extent that recovery of acid buffering capacity above a target criterion will not be achieved within a reasonable period. Another fraction of impaired lakes in the Adirondacks is anticipated to eventually recover enough to support healthy brook trout populations, but this recovery is expected to take a very long time (decades to centuries) to occur. As a result of the slow response of Adirondack lakes to decreases in acidic deposition, strategies such as liming (base addition) are being considered to accelerate recovery from acidification.

 In addition to acid deposition, the Adirondacks are highly sensitive to and impacted by atmospheric mercury deposition. Fish consumption advisories have been issued for 64 specific water bodies in the Adirondacks, and broad regional fish consumption advisories are in effect as well. Elevated fish mercury concentrations also pose a risk to fish-eating birds and other wildlife. Fish mercury contamination is linked to acidic deposition because of several factors, including the role of sulfate and nitrate inputs in stimulating or limiting methylmercury production, the effect of pH on methymercury biomagnification through food webs, the critical role of dissolved organic carbon in the transport and bioavailability of total mercury and methylmercury, and shifts in the base of the food web from detrital to algal sources.

 Honnedaga Lake is one of only seven lakes remaining in the Adirondacks that support a heritage brook trout fishery. The lake has been acidified by acidic deposition. The population density of brook trout is low and reproduction in some lake tributaries appears limited by acidification. The application of lime, either directly to tributaries or to their watersheds, is being studied as an approach to restoring and improving brook trout recruitment to the lake. Two tributaries were limed in 2012 and 2013, a tributary watershed was limed in fall 2013, and tributary liming is planned again for 2014.

Project Overview

The goal of this project is to characterize and improve understanding of the transport, transformations and trophic transfer of mercury in forest-surface water ecosystems in response to tributary and watershed liming. To achieve this goal, the U.S. Geological Survey (USGS), in collaboration with Syracuse University, is cooperating with the New York State Energy Research and Development Authority, to study the effects of liming on mercury cycling in the Honnedaga Lake watershed. Mercury is being measured in the water column, in aquatic macroinvertebrates, and in brook trout in tributary streams and in the lake. A specific project focus is the extent to which liming increases the mobilization of dissolved organic carbon, a transport agent for mercury, and the implications of increasing organic carbon concentrations on mercury movement through aquatic food webs. A separate but linked investigation led by the Biodiversity Research Institute is studying the effects of liming on mercury movement into the terrestrial ecosystem with a specific focus on birds.

This project is closely related to another USGS-led project of the effects of liming on soils, stream chemistry, forest vegetation, and terrestrial invertebrates (Whole-Ecosystem Restoration through Liming of Honnedaga Lake Tributary Watersheds), which includes collaborators from Cornell University and the SUNY College of Environmental Science and Forestry. The investigators from all three of these projects are working together in cooperation with the New York Energy Research and Development Authority to better understand the complex interactions that are likely to occur when liming is used as a method to accelerate ecosystem recovery from acidification. 

Project
Location by County

Herkimer County, NY