Project ID: 2005ID50B

Title: Seasonal variation in anthropogenic nutrient additions and food web response in a large deep lake (Lake Crescent, Olympic National Park)

Project Type: Research

Focus Categories: Water Quality, Surface Water, Non Point Pollution

Keywords: periphyton, lakeshore development, food web structure, stable isotope analysis

Start Date: 03/01/2005

End Date: 02/28/2006

Federal Funds: $20,000

Non-Federal Matching Funds: $40,000

Congressional District: 01

Principal Investigator:
Stephanie Hampton

Abstract

Shoreline development is known to degrade water quality and nearshore habitat for lake biota. Deep nutrient-poor lakes ¡V particularly prized for their fisheries and beauty in the Pacific Northwest ¡V may be especially sensitive to shoreline development that affects nearshore habitat. Shallow nearshore water in a steep-sided basin comprises relatively little of the total volume and surface area, but may provide the most crucial breeding habitat for fishes and, potentially, the primary feeding habitat. Even if pollutants entering at the shore are not sufficient to change open water conditions, nearshore communities may exhibit biomass and compositional changes that have disproportionately large impacts on food webs dependent on these shallow waters.
In Olympic National Park, Washington, Lake Crescent has modest residential development, and nuisance filamentous algal mats are now regularly observed at developed sites. At least one of the endemic salmonids appears to be avoiding breeding sites in areas with lush algal growth ¡V this salmonid uses a very restricted breeding area that overlaps with the highest density of residential development on the lake. If the Lake Crescent fishes also depend mainly on nearshore resources for feeding, shoreline development may further impact fish populations.

Here I propose to examine nearshore productivity differences between developed and undeveloped sites at Lake Crescent, in terms of composition and biomass of algal and macroinvertebrate communities. I will also use stable isotope analysis to infer the origin of nutrient pollution at each site ¡V human sewage can be differentiated from other sources using ƒÔ15N. In addition, I can assess the contribution of nearshore (versus open water) resources to the food web by examining ƒÔ13C signatures of algae, invertebrates and fish. Pilot data suggest the following patterns: developed sites support filamentous green algae, a human isotope signature is apparent at developed sites, and the food web is skewed toward nearshore feeding. Funding requested from the USGS will be used to 1) quantify the algal changes, 2) provide more conclusive evidence that the algal growth is fueled by human sewage, and 3) assess dependence of upper trophic levels on nearshore resources. These results will help managers focus their monitoring and pollution prevention efforts at Lake Crescent, and will be relevant to other large steep-sided basins of the Pacific Northwest. This work will form the foundation for later work on Lake Crescent and other large deep lakes, for which I am actively seeking further funding.

Progress/Completion Report, PDF