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Potential for Pathogen Growth, Fecal Indicator Growth and Phosphorus Release under Clam Removal Barriers in the Lake Tahoe Basin

Proposal [pdf]

Progress Report [pdf]

Lead Researchers:

Stefan Wuertz, Dept of Civil and Environmental Engineering, University of California-Davis, Geoffrey Schladow, Tahoe Environmental Research Center, University of California-Davis


The project seeks to measure the impact of clam barriers –rubber sheets that are spread on the bottom of Lake Tahoe to create anaerobic conditions to kill Asian clams – on the survival and re-growth of fecal indicator bacteria (FIB) and potential bacterial pathogens, and the release of soluble reactive phosphorus (SRP) from the anaerobic sediments that are produced through the treatment. The project is motivated by recent in-lake pilot experiments that demonstrated that barriers, when properly designed and installed, are effective at killing Asian clams in near-shore areas but that the anaerobic, relatively warm, and nutrient-rich conditions that are produced under the barriers may result in undesirable water quality impacts. Experiments testing the hypothesis that elevated FIB levels observed in preliminary experiments at Marla Bay and Lakeside Marina are due to bacterial re-growth and not actual contamination with fecal waste of human or non-human origin will be conducted in laboratory-based microcosms designed to mimic environmental conditions at the bottom of the lake. The simultaneous SRP measurements are intended to quantify release rates of phosphorus under anaerobic conditions (internal nutrient loading). The goals of the project are to (1) establish if FIB can re-grow under low oxygen conditions underneath clam barriers positioned in the lake, (2) perform spiking experiments with fecal material to track the fate of FIB and two relevant bacterial pathogens, Campylobacter jejuni and Salmonella enterica, and (3) quantify the release rates of phosphorus from the sediments associated with Asian clam growth in Lake Tahoe. This information is critical to helping agencies make an informed decision about both the benefits and risks of using bottom barriers to contain the spread of priority invasive species, and will be required as part of permitting associated with large-scale deployments of this technology.

Relation to Other SNPLMA Projects

The proposed project builds on the research that has been conducted in the area of control of Asian clams in the last 18 months at Lake Tahoe, including the Round 9 SNPLMA science project, "Development of a risk model to determine the expansion and potential environmental impacts of Asian clams in Lake Tahoe".  Additionally, the project will be coordinated with the SNPLMA Round 10 science project, "Natural and human limitations to Asian clam distribution and recolonization—factors that impact the management and control in Lake Tahoe".

Expected date of final products:

May 2011

Last Modified: Mar 28, 2013 02:52:07 PM