EPA Contract No. GL985600-01
Joseph V. DePinto
Great Lakes Program Department of Civil,
Structural, and Environmental Engineering
University at Buffalo
Joseph V. DePinto
Victor J. Bierman, Jr.
Timothy J. Feist
Ann Arbor, MI
Unites States Environmental Protection Agency Great Lakes National Program Office
77 W. Jackson Blvd.
Chicago, IL 60604
The information in this document has been funded by the U.S. Environmental Protection Agency’s (EPA) Great Lakes National Program Office. It has been subject to the Agency’s peer and administrative review, and it has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Environmental Protection Agency.
The Effect of Zebra Mussels on Cycling and Potential Bioavailability of PCBs: Case Study of Saginaw Bay
Table of Contents
2.1.1 Conceptual Approach for Multi-stressor Aquatic Ecosystem Model (SAGZM/PCB)
2.1.2 Saginaw Bay Multi-Class Phytoplankton Model
2.1.3 Zebra Mussel Bioenergetics Model
2.1.4 Coupled Phytoplankton Zebra Mussel Model (SAGZM)
2.1.5 Coupled Phytoplankton Zebra Mussel PCB Mass Balance Model
(Multi-Stressor Aquatic Ecosystem Model) - SAGZM/PCB
2.3 Bioaccumulation Model
3.1.1 System Specific Data
3.1.2 Forcing Function, Loadings, Boundary, and Initial Conditions
3.1.3 Process Related Parameters
3.1.4 Chemical Specific Parameters
3.2 Temporal and Spatial Scales
4.1.1 ∑PCB Concentration in Sediments
4.1.2 ∑PCB Concentration in Water Column
4.1.3 ∑PCB Concentration in Zebra Mussels
4.1.4 Zebra Mussels as Biomonitors
4.2 Sensitivity Analysis
4.2.1 Organic Carbon Normalized Octanol Partition Coefficient
188.8.131.52 Effect of Log Kow on Water Column ∑PCB Concentration
184.108.40.206 Effect of Log Kow on SPCB Body Burden of Mussels
220.127.116.11 Effect of Log Kow on Surficial Sediment ∑PCB Concentration
4.2.2 Effect of Phosphorus and PCB Loads and Zebra Mussel Densities
4.2.3 Zebra Mussel Filtration on Different Types of Particles
4.2.4 Lipid Content of Zebra Mussels
5.1.1 System Diagnosis and Interpretation
5.1.2 PCB Mass Stored in Zebra Mussels
5.1.3 Zebra Mussel Impact on Bioaccumulation in the Pelagic Lower Food Chain
18.104.22.168 Effect of Mass Specific Concentration in Various Species
22.214.171.124 Summary of Bioaccumulation Results
List of Figures (PDF 131Kb, 30 pages)
- Table 3.1: PCB Concentration at the Outlet of Saginaw River
- Table 3.2: PCB Concentration in Lake Huron Water
- Table 3.3: Mean Depth, Surface Area, and Water Volume of the Seven Segments of the Saginaw Bay (LTI 1997)
- Table 3.4: Sediment Properties
- Table 4.1: Comparison of Modeled Steady-State ∑PCB Concentration in Surficial Sediments with Data of 1988 (Endicott and Kandt 1994)
- Table 4.2: Annual Average ∑PCB Concentration in Zebra Mussels and Water Column
- Table 4.3: Comparison of ∑PCB concentration in water and sediments in the open water and Near Shore Zones Under Different Conditions of Zebra Mussels Presence and their Filtration on Different Types of Particles
- Table 5.1: Zebra Mussel Wet Weight and Total PCB Concentration in Zebra Mussels
- Table A1: Summary of Parameters Used in Model Calculations (PDF 23Kb, 4 pages)
- Table A2: Summary of Parameters in Model Calculations (PDF 23Kb, 4 pages)
With the introduction of zebra mussels (Dreissena polymorpha), the Great Lakes have experienced many ecological changes. The aim of this work was to understand and quantify the effects of zebra mussels on cycling and bioaccumulation of polychlorinated biphenyls (PCBs) in Saginaw Bay, Lake Huron. The Bay has extensive areas of hard bottom, along with ideal temperature and food regimes suitable for zebra mussel colonization making it as an ideal study area. To accomplish the goal, a screening level multi-stressor aquatic ecosystem model was developed by integrating various processes involving nutrient-phytoplankton-zebra mussels-PCB dynamics.
The developed integrated modeling framework of nutrients and fate and transport of PCBs is unique in determining the effect of Dreissena stressor in an aquatic system. The work has demonstrated that the invasion of mussels has led to a re-direction of the energy and nutrients from the pelagic food chain to the benthic food chain through enhanced removal of particles from the water column to the surface sediments. This additional particle flux is leading also to an increased flux of ∑PCBs to the sediments. Assuming a constant load of ∑PCBs to the system, ∑PCB concentration in the sediments was higher than those in the absence of zebra mussels. This suggests that the introduction of mussels has transferred a portion of the contaminant inventory to the sediments.
The influence of mussels’ filtering activities on PCB concentration in lower pelagic food web was examined with bioaccumulation model. The model forecasts a shift in the pattern of bioaccumulation. The exact shift depends on the dominance of various ecosystem interactions and feedbacks in the system, especially the impacts of whether or not zebra mussels filter herbivorous zooplankton and blue-green algae.
To further study the bioaccumulation of PCBs by zebra mussels, ∑PCB body burden of mussels was calculated. The proximity of mussels to contaminant sources is a significant factor affecting the PCB levels in mussels. The high ∑PCB level in zebra mussels in areas where ∑PCB concentrations were high showed that zebra mussels closely track the environmental conditions. This highlights the use of mussels as biomonitors of contaminants. Also a sensitivity analysis of the selected model parameters indicated that ∑PCB concentration in Dreissena was quite sensitive to Log Kow and lipid content.
presence of mussels has not only impacted the particle dynamics but also
nutrient cycling in the system. So this integrated framework was applied
to investigate the effect of trophic status of the system, which was
simulated by using different external phosphorus loadings to the system.
In modeled scenarios, enhanced production of algae with higher nutrient
loads not only decreased the bioaccumulation of PCBs in the base of the
food chain but also increased PCB concentration in the sediments that will
eventually affect the bioaccumulation in the benthic food chain. It was
found that in response to external phosphorus loadings, the water and
sediment ∑PCB concentration were directly proportional, whereas dissolved
water and ∑PCB concentration in phyptoplankton were inversely
proportional. The developed modeling framework can serve as a foundation
for evaluating the contaminant transport by mussels and to help direct
further research to answer management questions.