Bioaccumulation of PCBs in Striped Bass in Jamaica Bay
Mohammed A. Nasher (Undergraduate Student), Dr. Megan Wiley (Assistant Professor)
Department of Civil Engineering, City College of New York
BACKGROUND INFORMATION OF PCBs
Bioaccumulation is a process by which the concentration of a chemical increases over time in a biological organism compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted. PCBs (Polychlorinated Biphenyl) for example, a category or family of chemical compound formed by the addition of chlorine to biphenyl, bioaccumulate in fishes, which can then be eaten by humans. PCBs have been shown to cause cancer, brain damage, and liver defects. Even though the use of PCBs has been prohibited since 1977, existing PCBs continue to pose a problem, finding various pathways to travel through the ecosystem to humans.
HOW DOES THE ECOSYSTEM WORK
The PCB food chain begins when PCBs bind to sediment particles suspended in water and eventually settle to the rivers, streams, estuaries, or lake-bottom where they accumulate. These contaminated sediments eventually mix into the bottom mud during turbulence created by storms, river currents, and passing boats. Benthic or bottom-dwelling organisms are tiny animals, such as mayfly and dragonfly larvae, that live in sediments (1). As they burrow, benthic organisms absorb PCBs. This begins the process of biomagnification. (Source: www.lakemichigan.org/elimination/sheboygan05.asp)
BIOMAGNIFICATION OF PCBS
Fishes that are low on the food chain eat these benthic organisms, along with the PCBs they absorbed. Consumption and digestion are the primary means of exposure to and bioaccumulation of PCBs (1). For example, walleye have higher levels of PCBs than perch because they eat perch and absorb PCBs with every contaminated fish they eat. Therefore, even sediment barely contaminated with PCBs can result in high concentrations in both water and land-based life, including humans, which is shown in Figure 1. Moreover, PCBs have a high affinity for organic substances, such as fat molecules. In other words, PCBs accumulate in fat, making women, who on average have a higher body-fat content than men, and the children they bear more vulnerable to these toxic substances
The pathway of PCBs through food chain.
Source:www3.gov.ab.ca/srd/ fw/watch/invert_chains.html
STRIPED BASS IN JAMAICA BAY
In this study, we are focusing on historical records of PCB concentration in Striped Bass in Jamaica Bay. The reason this species has been chosen is that Striped Bass had been prohibited to eat for 7 years (April 1985 through April 1992) in New York Harbor. The Department of Conservation in the Division of Fish, Wildlife and Marine Resources has been collecting fish samples from Jamaica Bay since 1987. The following graphs show these data.
Figure 1: PCBs concentration in Striped Bass in different seasons
Based on Figure 1, the concentration of PCBs in summer is higher than that of fall. This may be caused by higher temperatures at the upper surface of water, which force fishes to the bottom layer. As previously discussed, PCBs concentrations are higher at this location.
Figure 2: PCBs in Striped Bass in different years in fall
Based on Figure 2, as the time goes on, the concentration of PCBs get smaller. The reason behind is the usages of PCBs have been prohibited since 1976. Therefore, we can predict that if we don’t discharge the PCBs in the estuary anymore, most likely we will be able to reduce the PCBs in fishes in time. However, that mean concentration in 1998 was slightly higher than 1997.
Figure 3: PCBs in different sizes of Striped Bass in fall 1993
Based on the Figure 3, bigger fishes are more contaminated by PCBs. The reason is bigger fishes have more lipid and fat compare to small fishes. The contaminated chemicals such as PCBs accumulate more in the fat or lipid part than other part of a fish body. Also the bigger fishes are at the upper level of food chain (shown in Figure 1) which accumulate higher concentration of PCBs.
In our study, we have used bioaccumulation model developed by Dr. Kevin J. farley of Manhattan College which helps us to find out the PCBs level in fishes. These are the following important results which have been found executing the model.
PCBs concentration of 2 years old fish in terms of few amount of lipid in fish body
PCBs concentration of 2 years old fish in terms of comparable higher amount of lipid in fish body
ON GOING ACTIVITIES AND FUTURE WORK
While we have qualitative explanations explaining the trends, the next step in the study is to quantify these relationships by correlating trends in PCB levels with environmental parameters such as dissolved and partitioned PCB concentrations and temperature. We plan to test the sensitivity of these environmental factors along with fish parameters including gill uptake rate, back diffusion rate, excretion rate, food ingestion rate, food assimilation efficiency, growth rate, lipid amounts and migration patterns to determine which processes govern PCB accumulation in this case. This understanding will aid policy decisions aimed at reducing PCB levels in Striped Bass.
ACKNOWLEDGEMENTS
I would like to express my deepest appreciation to National Oceanic and Atmospheric Administration who has provided funds of this research work. Thank to Kevin J. Farley ( Manhattan College, Environmental Engineering Department) who has provided the bioaccumulation model with its back ground information. In addition, I also would like to thank Lawrence Skinner, (New York State Department of Conservation in the Division of Fish, Wildlife and Marine Resources) who has provided the raw data. Finally, the guidance advice and persistent help of Dr. Megan Wiley is gratefully acknowledged. Without her contribution, this work would not have been possible.
REFERENCE
Skinner Lawrence, Jackling Samuel, Kimber George, Waldman John, Shastay Joseph, Newell Arthur 1996: New York State Department of Conservation. Chemical In Fish, Shellfish And Crustaceans From The New York-New Jersey harbor Estuary. PCB, Organ chlorine Pesticides and Mercury. Division of Fish, Wildlife & Marine Resources.
Skinner Lawrence, 2001: New York State Department of Conservation. Organic Chemical and Mercury In Selected Fish Species Taken From The New York Harbor. Division of Fish, Wildlife & Marine Resources.