Cellular and Genetic Tracers of Transport Time in Groundwater Systems Under the Direct Influence of Surface Water Bodies

The Problem

Cranberry Lake, New Jersey.

Intrusion of surface water into ground water systems surrounding a small recreational lake was determined during water quality investigations. Biological materials, including algae (specifically diatoms) and plant fragments, were found by microscopic examination of unfiltered ground water samples taken from domestic wells. Artificially maintained water levels within the lake and stresses placed upon the aquifer by well withdrawals facilitate movement of water from the lake into the local ground water system, potentially allowing contaminants to enter the aquifer from the lake. This raises national concern because similar lakeside settings exist throughout the United States.

Objectives

Develop a method of quantifying GWUDISW by identifying diatom proteins using various biochemical and immunological techniques. Diatoms from both surface and ground waters will be identified, counted, and proteins will be extracted from common diatom species and purified. These proteins will be used to develop monoclonal antibodies and accompanying enzyme immunoassays (Walker, 1996) that will facilitate the identification and quantification of the proteins in ground water and hence GWUDISW. Development of this method will mark the first use of these advanced cellular, biochemical, and immunological techniques in the study of ground water/surface water interaction.

Diatom image of the species Cymbella tumida.

Methodology

The siliceous portion (cell walls) of diatoms has been identified in water samples from wells near Cranberry Lake, New Jersey. The proteins that form other structures within the diatom have been detected in suspension or dissolved in the water column. These proteins will be identified at the molecular level using biochemical (Hecky et al., 1973, Dauwe and Middleburg, 1998) and genetic methods (Xu and Tabita, 1996) already proven to be successful with some microorganisms.

Samples were collected weekly from April to September 2001 by WRDNJ. The diatom species in samples have been identified and counted at CRRL. Archived samples of ground and lake water from 1999 have been examined to evaluate changes in the diatom community over time. Aulacoseira granulata and Fragilaria crotonensis are dominant species through most of the year and have also

Immunoassay to detect diatoms using a plate spectrophotometer.

been identified in ground water samples. Aulacoseira granulata, Fragilaria crotonensis, and Nitzschia palea were selected as our target species based on their occurrence in ground water and prevalence in lake samples. They are mass-cultured in small batches at CRRL to produce quantities sufficient for protein extraction. Cell wall proteins have been extracted from theses cultures and were sent to the NFHL to develop antibodies. Also, cultures were grown for kill experiments and protein profiles and ratios were calculated from the timed kills to determine travel time of target species from surface to groundwater.

Highlights and Key Findings

Algal cultures grown in the laboratory. The center carboy contains diatoms.

A polyclonal antibody was developed from Nitzschia cell wall preps at NFHL.

An ELISA was developed that allows detection of diatoms at the 5,000 cells/mL level using this antibody at 1/50 dilutions or less.

A kill experiment was completed on Aulacoseira granulata, which included analysis for total protein, chlorophyll a, and protein profiles.

Where Are We Headed In 2003

1. Determine sensitivity and specificity of enzyme-linked immunosorbent assays to concentrations of diatom proteins found in domestic wells.

2. Determine travel times of diatoms from surface to ground water using changes in protein profiles and light harvesting protein concentrations.

3. Field test method with ground water samples from a controlled setting where lake-water intrusion has been documented (Cranberry Lake) and additional group of lakeside communities in diverse environmental settings where GWUDISW is anticipated.

4. Establish standard methods for sampling and detection of surface to ground water in lakes and neighboring domestic wells using the biochemical and immunological methods associated with diatom proteins.

Project Contact

Alec Maule
U.S. Geological Survey
Western Fisheries Research Center
Columbia River Research Laboratory
5501-A Cook-Underwood Rd.
Cook, WA 98605-9717

Email: alec_maule@usgs.gov
Phone: 509-538-2299
Fax: 509-538-2843

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