![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20081102160618im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
EPA Contract No. GL985600-01
November, 2000
Prepared by:
Joseph V. DePinto
Jagjit
Kaur
Great
Lakes Program
Department of Civil,
Structural, and Environmental Engineering
University at Buffalo
Joseph V. DePinto
Victor J. Bierman, Jr.
Timothy J. Feist
Limno-Tech,
Inc.
Ann Arbor, MI
Prepared
for:
Unites States Environmental Protection Agency
Great Lakes National Program Office
77 W. Jackson Blvd.
Chicago, IL 60604
about pdf files
DISCLAIMER
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.
Invasive Species
The Effect of Zebra Mussels on Cycling and Potential
Bioavailability of PCBs: Case Study of Saginaw Bay
FINAL COPY
Table of Contents
1.1 INTRODUCTION
1.2 BACKGROUND
1.3 GOALS AND OBJECTIVES
2.1
MODEL
DEVELOPMENT
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
2.2
Partitioning
2.3
Bioaccumulation Model
3.1 INPUT
DATA
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
Screening Level
Calibration
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
4.2.1.1
Effect of Log Kow on Water Column
∑PCB Concentration
4.2.1.2
Effect of Log Kow on SPCB Body Burden of Mussels
4.2.1.3
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 SAGZM/PCB
Application
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
5.1.3.1
Effect of Mass Specific Concentration in Various Species
5.1.3.2
Summary of Bioaccumulation Results
6.1
Conclusions and Recommendations
6.1.1 Conclusions
6.1.2
Recommendations
6.1.3
Model
Limitations
7.1
References
Appendix (PDF
69Kb 26 pages)
List of Figures (PDF 131Kb 30 pages)
List of Tables
- 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)
Summary
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.
The
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.