Investigation of the bio-filtration potential of the Pacific Oyster (Crassostrea gigas) to decrease fecal coliform bacterial levels


Project Location, Description, Goals, and Approach:

            Little research has been done on the ability and efficiency of Crassostrea gigas to filter specific particles, such as fecal coliforms, out of the water column.  This basic information is vital for any further studies that utilize the bio-filtration abilities of C. gigas.  The project proposed will be conducted in an outdoor laboratory setting, with the main goal to explore in depth the filtration rates of the Pacific Oyster, with respect to fecal coliforms.


Phase One

            The first phase of the project involves a series of highly controlled laboratory experiments to determine how well Crassostrea gigas can filter out fecal coliforms. 

Oysters will be placed in a circular, recirculating tank of sterile seawater.  A known amount of Escherichia coli will be added to the tank with oysters and an identical control tank with no oysters.  Water samples will be taken at set intervals from both the oyster-containing tank and the control tank.  E. coli levels in each sample will be recorded and plotted to show the rate of decline in bacterial concentrations.  The rate of decline in the oyster-containing tank will be compared to that of the control tank to determine how much bacteria the oysters are filtering out of the water column.  The first phase will be repeated three times to ensure accuracy.



Phase Two

            The second phase of the project strives to simulate a number of environment condition variables that the oysters will face in nature on a routine basis, and determine how filtration rates are affected by these environmental changes.  Environmental conditions that will be explored in phase two are turbidity, substrate, and temperature.  Each of these three conditions will be looked at separately in parts one, two and three.  All experiments will use the same basic tank design as the first phase. 


Part one

Jørgensen showed that bad water quality (turbidity) may cause the bivalve to partially close its shell and subsequently reduce filtration rates.  Phase one of the project deals with a clear water column containing only Escherichia coli.  The water in the bay is significantly more turbid (cloudy) than the water used in phase one of this project.  Given this, it is likely that the filtration rates will change if Crassostrea gigas is placed in water more closely resembling that of the bay.


Part one of phase two entails two experiments, each repeated 3 times, to determine how the filtration rate of Crassostrea gigas changes when placed in water that closely represents the composition of bay water.

The first experiment will use water mixed with sterile particulate matter so that it closely matches the turbidity of the bay.  A known amount of Escherichia coli will be added to the tank with oysters and an identical control tank with no oysters.  The rest of the experiment will be conducted as in phase one.  The second experiment will use actual bay water, rather that the more controlled mixture used in the first experiment. 


Part two

Riisgard and Møhlenberg suggested that the substrate a bivalve is placed on may alter its filtration capacity.  Further investigation to determine if filtration rates do change relative to the substrate that the bivalve is placed in would be useful.


Part two of phase two involves two experiments, each repeated three times, to determine if the filtration rate of Crassostrea gigas is influenced by substrate.

Both experiments will be identical to phase one except for the substrate the oysters are placed on/in.  The first experiment will keep the oysters in suspended net bags.  The second will keep the oysters in sterile sand.  The first phase kept the oysters on the smooth tank bottom, and will be used as a third substrate to compare against.


Part three

The affect of temperature changes on bivalve filtration rates has yet to be explored.  With the generally shallow depth of the bay and the two to five foot tidal changes, water temperature in the shallow mud flat areas does fluctuate considerably.  Affects of this regular temperature change on C. gigas filtration rates should be investigated.


Part three of phase two entails a single experiment, repeated three times, to establish if and to what extent temperature affects the filtration rate of Crassostrea gigas. 

This experiment will be identical to the first phase but with a water temperature closely matching the maximum temperature of the shallow areas of the bay.  The first phase of the project used a water temperature equivalent to the temperature of the bay at high tide, the minimum temperature in the bay.  The difference in bacterial decline rates will illustrate the affect of water temperature on the filtration rate of C. gigas.


CCMP Action Plan Implemented:
            This project was designed as a prerequisite to the CCMP Action Plan BACT–6, which proposes a pilot study designed to test the bio-filtration abilities of Crassostrea gigas under conditions found in Morro Bay.  Very little research has been done with the bivalve C. gigas specifically.  The reaction of C. gigas, with respect to filtration rates, to various environmental conditions that routinely occur in Morro Bay, is virtually unknown.  The project proposed here would provide vital information about the bio-filtration abilities of the Pacific Oyster in conditions similar to Morro Bay.  This comparatively inexpensive, well-controlled series of laboratory experiments would provide much needed data to substantiate the viability of a much larger scale field project such as the one suggestion in BACT-6.


Project Budget:




NEP Cost

Other Funding










 Monterey Bay Aquarium loaned a UV sterilizer

Containment tubs





Pumps & filters





Sample bottles




Donated by Loyola University Chicago

Dilution Bottles




Donated by IDEXX Laboratories, Inc.

Reagent Packets

3 packs of 200



One pack donated by IDEXX Laboratories, Inc.


6 packs of 100



Two packs donated by IDEXX Laboratories, Inc.

Tray Sealer




On loan from  IDEXX Laboratories, Inc





On loan from Morro Bay High School






Misc. Lab supplies













December 9th, 2000            Supplies and equipment for phase one will be gathered by this date.  Lab setup will begin.

December 16th, 2000            Phase one will begin

January 6th, 2001            Phase one will be completed

January 8th, 2001            Supplies and equipment for phase two will be gathered by this date.

January 20th, 2001            Phase two, part one will begin

February 3rd, 2001            Phase two, part one will be completed.  Part two will begin.

February 24th, 2001            Phase two, part two will be completed.  Part three will begin.

March 3rd, 2001                         Phase two, part thee will be completed. 

April 30th, 2001            Final Report will be completed.



Applicant Qualifications and Jurisdictional Authority:

·         Independent researcher

·         Leader of 4H Plankton Monitoring group

·         Participant in California Department of Health Services’ toxic phytoplankton monitoring network

·         Owner of Nerds on Wheels, a computer consulting, tutoring, repair and web development company

·         Trained in microbiology techniques in a micro-marine biology course

·         4th place winner in the California State Science Fair & winner of regional science fairs

·         Trained in fecal coliform level monitoring processes by staff in the water quality control department of Monterey Bay Aquarium at their lab facility

·         In contact with various researchers and agencies, including Loyola University Chicago, Roger Phillips, Applied Research Manager at the Monterey Bay Aquarium, Palmer Landcaster, owner of Aquatic Adventures, and Gregg Langlois, supervisor of the phytoplankton monitoring program at the California Department of Health Services.


Evaluation/Monitoring Methods:

            Escherichia coli levels will be quantified using Colilert® 18 hr MPN method.  Actual filtration rates will be calculated using Hildreth and Crisp’s corrected formula for calculating the filtration rate of bivalve mollusks in a recirculating system.


Permits & Environmental Compliance:



Property Owner Permission:
            The project will be conducted on my personal private property.