U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications NOAA-NWFSC Tech Memo-1: Bioindicators of Contaminant Exposure in Winter Flounder DISCUSSIONBioindicators of Contaminant Exposure
In general, concentrations of PCBs in tissues and FACs in bile tended to be higher in winter flounder from contaminated sites in Boston Harbor and Raritan Bay than in flounder from other embayments, although exceptions were found for some tissue contaminants at selected sampling times. Moreover, levels of contaminants in bile and tissues were generally correlated with other biological indicators of exposure such as xenobiotic-DNA adducts in liver and the presence of hepatic lesions. The only measure that showed no relationship with sediment contaminant levels or concentrations of contaminants in tissues or fluids of winter flounder was hepatic AHH activity. Hepatic AHH activity was significantly depressed in gonadally maturing female winter flounder, even in animals collected in October which were in early stages of vitellogenesis, presumably because of the strong suppressive influence of estradiol on CYP1A in female winter flounder (Snowberger Gray et al. 1991). These findings suggest that hepatic AHH activity is not a reliable indicator of contaminant exposure in vitellogenic winter flounder and would dictate the employment of other measurements to assess chemical contamination in flounder undergoing reproductive development. 

Results show that levels of selected contaminants in tissues and bile of winter flounder varied with the time of sampling. This was particularly noticeable with levels of PCBs in ovary and liver. Between October and December, PCB concentrations in liver declined, while concentrations in ovaries increased. This suggests mobilization of PCBs from liver to ovaries in conjunction with the transfer of lipids to the developing gonads. This same phenomenon has been described in other fish species (Pizza and O'Conner 1983). Levels of PCBs in brain, however, remained constant throughout the reproductive season. This suggests that levels of PCBs in brain may be a more stable measure of the body burden of PCBs than levels in liver or ovary. At the same time, however, brain PCB concentrations showed little correlation with liver pathology, although both ovarian and liver PCB concentrations were positively correlated with prevalences of hydropic vacuolation and proliferative liver lesions. Moreover, intersite differences in brain PCB concentrations were less marked than differences in liver or ovary PCB concentrations. We are continuing to evaluate the utility of brain PCB concentrations as an indicator of long-term PCB exposure and to examine relationships between pathological effects in fish and PCB concentrations in different tissue compartments.
Fish Pathology 
Results of the present study indicate that winter flounder residing in contaminated areas are likely to exhibit a variety of suspected toxicopathic liver lesions, including unique degenerative or proliferative conditions. Both the proliferative lesions and hydropic vacuolation were significantly elevated in vitellogenic flounder from sites within Boston Harbor and Raritan Bay in comparison to prevalences in flounder from reference sites. Of all toxicant-associated lesions, the most commonly observed was hydropic vacuolation of hepatocytes and biliary epithelial cells, which was found in fish from all 11 sampling sites at prevalences ranging from 3 to 60%. In addition to winter flounder, hydropic vacuolation has been observed in several other flatfish species in association with exposure to contaminants (Stehr 1990, Stehr et al. 1991, Myers et al. in press). Hepatic neoplasms were rarely observed in winter flounder sampled in this study; only one case was found in a fish from the Mystic River site in Boston Harbor. Foci of cellular alteration (FCA), which are putatively preneoplastic lesions (Frith and Ward 1980, Squire and Levitt 1975), were found in fish from several sites within and in the vicinity of Boston Harbor and Raritan Bay at prevalences ranging from 2 to 13%. However, they were also found at low prevalences at some of the less-contaminated embayments, including Duxbury Bay, Narragansett Bay, and Niantic Bay. 

In general, the types of lesions observed in winter flounder in the present study and their distribution among the common sampling sites are similar to the findings of other investigators (Murchelano and Wolke 1985, 1991; Moore 1991; Carr et al. 1991). However, prevalences of most lesions in the present study were somewhat lower than those reported in other studies, in which both male and female winter flounder were sampled and fish were collected outside of the reproductive season. For example, hydropic vacuolation, the most common toxicant-associated lesion found in the present study, were observed in 23 to 46% of fish examined from sites within Boston Harbor. In contrast, other investigators (Murchelano and Wolke 1985, 1991; Moore 1991; Carr et al. 1991) report prevalences of hydropic vacuolation from 50 to 74% in Boston Harbor winter flounder. In the present study, biliary proliferation was observed in 7 to 12% of Boston Harbor winter flounder, while Moore (1991) reports prevalences of 25%. Prevalences of neoplastic and preneoplastic lesions were also somewhat higher, and preneoplastic lesions were less uniformly distributed in other investigations than in the present study. For example, Wolke et al. (1985) and Murchelano and Wolke (1985, 1991) examined winter flounder from several sites along the northeast coast, and observed preneoplastic and neoplastic lesions in 10-15% of winter flounder sampled at sites within Boston Harbor, approximately 10% of winter flounder from New Haven, and 3% of flounder from Narragansett Bay. In contrast, no neoplasms were found in 93 winter flounder from central and eastern Long Island Sound, Casco Bay in Maine, and George's Bank. Moore (1991) observed neoplasms in approximately 10% of Deer Island winter flounder, but saw none in fish from Cape Cod Bay, Massachusetts Bay, or Georges Bank. 

It is not entirely clear why neoplasm prevalences were so low in winter flounder sampled in this study. However, preliminary data from samplings of winter flounder conducted in spring of 1988 and 1989 in conjunction with NOAA's National Benthic Surveillance Project (NBSP) show that winter flounder which were sampled at heavily contaminated sites in Boston Harbor and Raritan Bay during the spring exhibited higher prevalences of neoplasms and other toxicopathic lesions, including hydropic vacuolation, than females sampled in the present study during the winter spawning season (Johnson et al. 1992). This suggests that the population of flounder sampled in winter for the present study may have included fish that were not normally resident at the sampling sites during the year, but had migrated to these sites from other, less contaminated areas to spawn. This theory is supported by studies on winter flounder migration patterns during the spawning season, which suggest that, for the most part, winter flounder are organized into distinct spawning groups that return to their respective spawning grounds year after year (Black et al. 1988, Saila 1961). Outside of the spawning season, however, many of these fish disperse to offshore waters and the stocks mix (Danila 1989, Black et al. 1988). Consequently, all fish captured in an area during the reproductive season do not necessarily remain there during the rest of the year, although a large proportion may be permanent residents. 

Additionally, because only female flounder were sampled in the present study, it is possible that the lower prevalences of neoplasms in this sampling could be due to gender-associated differences in disease susceptibility. Our data from the NBSP sampling during 1988 and 1989 (Johnson et al. 1992) do suggest that female winter flounder are slightly less likely than male winter flounder to develop neoplasms and cystic degeneration. This finding is somewhat surprising, as other studies have found little or no effect of gender on neoplasm prevalence in winter flounder (Murchelano and Wolke 1991, Moore 1991). Similarly, Rhodes et al. (1987) found that gender did not appear to have any effect on neoplasm prevalence in English sole (Pleuronectes vetulus, formerly Parophrys vetulus). Because the gender-related differences in prevalences for winter flounder sampled in the NBSP were relatively small (e.g., 1% vs. 3%), the possibility that they simply represent sampling error cannot be discounted. However, true gender-associated differences in susceptibility to lesion development could arise as a result of the differences in the migratory behavior of male and female winter flounder. 

In addition to showing elevated prevalences at contaminated sites, hydropic vacuolation and proliferative lesions were positively correlated with levels of FACs in bile and PCBs in tissues of winter flounder. Proliferative lesions were also positively correlated with levels of DNA-xenobiotic adducts in liver. Because both of these lesion types appear to be strongly linked to exposure to multiple classes of chemical contaminants in winter flounder, they represent reliable bioindicators of contaminant exposure. The relationship between PAHs and PCBs and presumably degenerative and regenerative lesions such as hydropic vacuolation and biliary proliferation is not surprising, as a number aromatic and chlorinated hydrocarbons have been shown to have necrogenic effects on the liver (Hodge et al. 1967, Murphy 1986). However, it is difficult to identify the precise etiology of either of these lesion types because of their apparent association with both types of contaminants, namely PAHs and PCBs, which generally co-occur in urban sediments. Laboratory exposure studies with winter flounder may help to clarify the relative roles of PAHs and CHs in the development of lesions such as hydropic vacuolation and biliary proliferation. 

Unlike hydropic vacuolation and proliferative lesions, neoplasms and preneoplastic focal lesions were not significantly correlated with bioindicators of contaminant exposure. As noted above, neoplasm prevalences were too low for their relationship with measures of contaminant exposure to be evaluated effectively. However, the lack of correlation between the focal lesions and indicators of PAH exposure (i.e., concentrations of biliary FACs and xenobiotic-DNA adducts in liver) was somewhat surprising, because PAHs are well established as genotoxic carcinogens in mammals (Williams and Weisburger 1986), and administration of PAHs in laboratory studies has led to the development of preneoplastic lesions in several fish species (Schiewe et al. 1991, Metcalfe et al. 1988, Black et al. 1985, Hendricks et al. 1985, Schultz and Schultz 1984, Hawkins et al. 1990). Moreover, several epidemiological studies, including histopathological field surveys of English sole in Puget Sound, show strong correlations between PAH levels in bile and sediments and prevalences of neoplasms and preneoplastic focal lesions (Malins et al. 1984, 1985, Landahl et al. 1990, Myers et al. 1990). 

It is not entirely clear why correlations between PAH exposure and prevalences of FCA in winter flounder were not as strong as correlations observed, for example, in English sole, but several factors may have been involved. First, because winter flounder are relatively mobile, it may have been difficult to obtain an accurate measure of chronic PAH exposure in this species. Levels of metabolites in bile are generally reliable measures of short-term exposure to PAHs (Krahn et al. 1986), but because PAHs are rapidly metabolized (Varanasi et al. 1989b, Stein et al. 1987), biliary FAC levels are unlikely to remain elevated for long periods of time if animals leave contaminated areas. In a species such as winter flounder, which may undergo extensive seasonal migrations, biliary FAC concentrations at the time of capture may not necessarily be an accurate reflection of the level of PAH exposure over the animal's lifetime. Levels of xenobiotic-DNA adducts in liver (Varanasi et al. 1989a) may provide a more reliable measure of chronic PAH exposure than biliary FAC concentrations. However, they were measured in relatively few animals in this study, and perhaps for this reason they showed no clear relationship with prevalences of FCA or neoplasms in winter flounder. 

Another factor that must be considered in evaluating the relationships between chemical contaminants and neoplastic and preneoplastic lesions in winter flounder is that winter flounder may differ somewhat from English sole and other teleost species that have been used as models in carcinogenesis in their pathological response to environmental contaminants. Patterns of liver lesion occurrence in winter flounder from Boston Harbor and Raritan Bay are quite different, for example, from those observed in English sole from urban areas in Puget Sound. Neoplasm prevalences in winter flounder are relatively low (e.g., 7% in sexually mature winter flounder from Deer Island Flats (Moore 1991) compared to prevalences of 36% in sexually mature English sole from a similarly contaminated site in the Duwamish Waterway in Puget Sound, WA (Johnson et al. 1988)). Moreover, a higher proportion of the neoplasms in winter flounder are cholangiocellular in origin than in English sole. In winter flounder, cholangiocellular neoplasms make up 42 to 90% of all liver neoplasms observed (Moore 1991; Murchelano and Wolke 1985, 1991), while in English sole they account for only about 15% of liver neoplasms (Myers et al. 1987). Hepatocellular neoplasms, which are typically associated with PAH exposure in both field (Landahl et al. 1990, Myers et al. 1990, Vogelbein et al. 1990) and laboratory studies (Metcalfe et al. 1988, Black et al. 1985, Hendricks et al. 1985, Schultz and Schultz 1984, Hawkins et al. 1990) with English sole and other fish species, appear to occur less frequently and compose a lower proportion of the neoplasms detected in winter flounder. Putatively preneoplastic focal hepatic lesions, which are commonly observed in English sole (Myers et al. 1987), are far less frequently detected in winter flounder (Moore 1991). 

The early degenerative and proliferative changes found in the livers of winter flounder and English sole after exposure to toxicants are also markedly different. In winter flounder, the most common early toxicopathic lesion is hydropic vacuolation (Murchelano and Wolke, 1985, Moore et al. 1989), a condition which is not found in English sole (Myers et al. in press). Instead, English sole develop a unique degenerative condition, megalocytic hepatosis (Myers et al. 1987), which is only rarely observed in winter flounder (Johnson et al. 1992). Because of these differences in patterns of lesion occurrence, it has been suggested (Moore 1991) that the histogenesis of hepatic neoplasms, as well as the roles that various classes of contaminants play in their development, may be somewhat different in winter flounder than in species such as English sole or killifish, which have comparatively high prevalences of hepatocellular neoplasms in PAH-contaminated areas. 

Additionally, it should be remembered that only a limited number of samples were available for the analyses of relationships between contaminant exposure and lesion prevalences, and the number of neoplastic and preneoplastic lesions was relatively low at all sites sampled. With a larger data base a more comprehensive assessment of the relationships between contaminants and neoplastic and preneoplastic lesion in winter flounder may be possible. 
Reproductive Success
The results of this study suggest that winter flounder sampled from contaminated estuaries may exhibit declines in egg weight and an increased probability of ovarian atresia, although the magnitude of these effects appears to be relatively small. These findings corroborate reports by other researchers of reduced egg or larval size in winter flounder from contaminated sites in Boston Harbor and Long Island Sound (Black et al. 1988, NOAA 1990). Contaminant-associated declines in egg weight have also been noted in other species, including white croaker (Genyonemus lineatus) (Cross and Hose 1988) and kelp bass (Paralabrax clathratus) (Cross and Hose 1989) from southern California, and striped bass (Morone saxatilis) from the San Francisco area (Whipple et al. 1987a). Atresia of both immature and vitellogenic oocytes in conjunction with exposure to aromatic and chlorinated organic compounds has been reported in several other fish species as well (Saxena and Garg 1978, Cross et al. 1984, Nagler et al. 1986, Whipple et al. 1987b, Cross and Hose 1988). 

The present results show, however, that mean steroid hormone levels, ovarian development, and fecundity were not depressed in winter flounder from heavily contaminated sites in Boston Harbor and Raritan Bay. Moreover, on an individual fish basis, these reproductive parameters showed little correlation with any of the indicators of contaminant exposure which we measured, even though concentrations of PCBs in tissues and FACs in bile were elevated in a relatively large proportion of sampled animals. In fact, Raritan Bay flounder, which exhibited high frequencies of hepatic lesions as well as elevated levels of PCBs in tissues and FACs in bile, showed the greatest degree of reproductive development of all groups of animals sampled. Variations in steroid hormone levels, ovarian growth, and fecundity were most closely associated with biological or ecological factors, such as fish age or size, sampling time, and the geographical area from which the fish were sampled. Perhaps the most marked influence was the clinal difference in the timing and probability of gonadal maturation between fish from areas north and south of Cape Cod. This geographical variation in the timing of reproduction has also been noted by other investigators (Pearcy 1962). 

The finding that exposure to marine pollutants such as PAHs and PCBs, which were used as general indicators of anthropogenic contamination, had little apparent effect on ovarian development or steroid levels in winter flounder was quite surprising. Alterations in both of these reproductive parameters have been described in other fish species collected from areas contaminated with these types of xenobiotic compounds (Johnson et al. 1988, Stott et al. 1983, Munkittrick et al. 1991). The reasons for the apparent resistance of winter flounder to contaminant-associated reproductive impairment are not clear. However, a number of factors could influence its susceptibility to the effects of reproductive toxicants in the environment, including the level of exposure, the duration and timing of exposure, and species-specific pathways of uptake, metabolism, and detoxication of contaminants. 

In the present study, the results show that a substantial proportion of gravid female winter flounder sampled had high levels of contaminants in their tissues and body fluids, at least at the time of collection. Some of these contaminants, such as PCBs, are not extensively metabolized or eliminated, and tend to build up in tissues over time (Lieb et al. 1974, Pizza and O'Conner 1983, Stein et al. 1987). Consequently, there is a high probability that PCBs which were present in winter flounder tissues at the time of collection were in the body at similar concentrations prior to and throughout gonadal development. If winter flounder from contaminated areas on the northeast coast have elevated levels of PCBs in the body throughout ovarian recrudescence, yet show no signs of reproductive dysfunction, it would appear that PCBs have little effect on early reproductive development in winter flounder. 

The finding that winter flounder with high concentrations of PCBs in tissue do not show altered ovarian development is not entirely unexpected, because in English sole, little relationship was found between tissue PCB levels and this particular type of reproductive dysfunction (Johnson et al. 1988). Moreover, although other fish species with tissue PCB concentrations comparable to those measured in winter flounder (e.g., ovarian PCB concentrations of 200 to 300 ng/g wet weight and above) have exhibited various types of reproductive impairment in field studies (Cross et al. 1984, Cross and Hose 1989, von Westernhagen et al. 1981), the types of impairment reported in these studies, such as impaired spawning or decreased larval viability, involve relatively late stages of the reproductive cycle. In contrast, inhibited ovarian development and altered plasma steroid levels manifest themselves during early gonadal recrudescence. While further research is needed, our observations on both winter flounder and English sole suggest that PCBs may be more toxic during later stages of reproductive development (e.g., affect egg and larval viability), than during early vitellogenesis in fish. 

Like winter flounder with elevated tissue PCB concentrations, flounder with elevated biliary FAC concentrations showed no discernible impairment in gonadal development or alteration in plasma estradiol levels. This was surprising, because PAH exposure appears to be closely correlated with impairment of the early phases of the reproductive cycle in English sole. For example, English sole from PAH-contaminated areas showed impaired gonadal development, decreased estradiol levels in plasma, and reduced ovarian estradiol production. These types of impairment were statistically correlated with elevated concentrations of FACs in bile (Johnson et al. 1988, in press). Moreover, in laboratory studies, gravid English sole exposed to extracts of creosote-contaminated sediments showed reduced plasma estradiol concentrations and an increased rate of excretion of metabolites of estradiol (Stein et al. 1991). Preliminary studies indicate that rock sole and flathead sole show similar changes in plasma estradiol concentrations and ovarian estradiol production when exposed to PAHs (Johnson et al. in press). In contrast, winter flounder from sites within Boston Harbor had biliary FAC levels two to three times as high as those associated with reproductive impairment in English sole, but they exhibited no adverse effects on ovarian development. 

Unlike PCBs, however, biliary FAC concentrations are an indicator of relatively short-term exposure; so, as noted earlier, high FAC concentrations at the time of sampling are not necessarily an indication of chronic exposure to PAHs. Previous studies show that after a single exposure to PAHs, biliary concentrations of FACs decline substantially within 3 weeks (Collier and Varanasi 1991). Consequently, seasonal migrations or similar factors affecting the duration and timing of short-term exposure to PAHs could have a marked impact on tissue concentrations of PAHs and their metabolites. Studies of migration patterns of winter flounder during the reproductive season (Black et al. 1988, Valdez 1989, Danila 1989) indicate that while female flounder may move into highly contaminated urban estuaries in the winter to spawn, in summer they spend extended periods in less contaminated areas offshore (Valdez 1989, Danila 1989). Because of these migration patterns, flounder captured within Boston Harbor or Raritan Bay in late fall or early winter may not be resident at these PAH-contaminated sites during critical early stages of vitellogenesis, and so they may not be exposed to appreciable PAHs when contaminant-associated alterations in steroid production or metabolism could have a significant impact on ovarian development. In contrast, English sole, which show a high prevalence of inhibited ovarian development in association with PAH exposure, remain in contaminated estuaries for most of their life cycle, including the period when they are undergoing vitellogenesis, and migrate to deeper, less contaminated areas offshore for a brief period in winter to spawn (Johnson et al. 1991, Day 1976). Laboratory exposure studies with English sole and winter flounder are necessary to test the hypothesis that limited PAH exposure at critical phases of the reproductive cycle could at least partially account for the apparent resistance of winter flounder to early reproductive impairment. 

Finally, it is possible that winter flounder may be less sensitive than English sole to the effects of reproductive toxicants because of species-specific differences in contaminant metabolism in recrudescent females. Interspecific differences in toxicant metabolism do exist in flatfish species; starry flounder (Platichthys stellatus), for example, appear to have an greater ability to conjugate and detoxicate PAH metabolites than English sole (Varanasi et al. 1986, 1987; Collier et al. in press). Moreover, starry flounder, somewhat like winter flounder, exhibit a substantially lower prevalence of hepatocellular neoplasms than English sole exposed to similar levels of contaminants at polluted sites (Myers and Rhodes 1988, Myers et al. in press). These findings, combined with the fact that PAHs are strongly correlated with the prevalence of neoplasms in English sole and other fish species (Myers et al. 1990), suggest that differences in toxicant metabolism may affect susceptibility to liver disease. It is possible, therefore, that differences in toxicant metabolism may affect susceptibility to reproductive impairment as well, although this is yet to be established. 

In addition to exhibiting differences in their pathologic responses to contaminants, winter flounder and English sole also show differences in the impact of the reproductive cycle on CYP1A dependent activity. In English sole, hepatic AHH activity changes relatively little until just before spawning (Johnson et al. 1988). However, in winter flounder, as this and other investigations show (Snowberger and Stegeman 1987, Snowberger Gray et al. 1991), CYP1A-dependent activity declines markedly in early vitellogenesis. Changes in activity of xenobiotic metabolizing enzymes during this phase of the reproductive cycle may alter the disposition of toxicants in the liver and in extrahepatic tissues such as ovary and, consequently, alter the effects of exposure to PAHs and similar compounds on winter flounder. 

Further study is clearly needed to establish the effects of behavioral and physiological factors on the fate and effects of PAHs and similar compounds in winter flounder. Most critical are laboratory studies examining the impact of reproductive toxins on all phases of the reproductive cycle, to determine whether the apparent resistance of winter flounder to the effects of these compounds is due to a lower sensitivity to the chemicals, or to migration patterns that limit exposure at critical phases of the reproductive cycle. Additionally, it should be kept in mind that in the natural environment winter flounder is simultaneously exposed to a wide array of different classes of contaminants, which could have widely divergent effects on reproductive function. In fact, certain compounds, including the heavy metal cadmium, appear to stimulate rather than inhibit reproductive development (Thomas 1989). Interpretation of the present findings may be complicated by interactive effects of these various chemicals. Such questions can best be clarified through laboratory studies. 

In summary, the present results indicate that, in general, winter flounder from heavily contaminated sites within Boston Harbor and Raritan Bay had higher concentrations of PCBs in tissues, FACs in bile, and xenobiotic-DNA adducts in liver, as well as higher prevalences of toxicopathic liver lesions, than winter flounder from nearby, less urbanized embayments. However, ovarian growth and estradiol concentrations in plasma were not depressed in flounder from the contaminated areas, or in flounder with high concentrations of PCBs in tissues or FACs in bile. It is not clear why these contaminants, which have been shown to cause reproductive impairment in other fish species, have little apparent effect on gonadal development in winter flounder. However, migratory patterns that limit exposure to known reproductive toxicants (e.g., PAHs) at critical phases of the reproductive cycle, and differences in metabolism of or sensitivity to these toxicants, could be contributing factors. 

It should be noted that although winter flounder appear to be relatively resistant to the effects of reproductive toxicants during early phases of gonadal development, this does not rule out the possibility that exposure to environmental contaminants may lead to impairment in later phases of the winter flounder reproductive cycle. Because winter flounder often spawn in contaminated inshore estuaries, and have demersal eggs, there is a particular risk that egg and larval development may be affected by contact with contaminated sediments. In fact, preliminary studies indicate that environmental disturbances, such as dredging, or exposure to contaminants in sediments or sewage effluents may decrease hatching success and impair the growth and development of winter flounder larvae (Weis et al. 1989, Monooch 1988, NOAA 1990). 

The contrasting effects of exposure to contaminants on ovarian development in winter flounder and English sole point to the need for both field and laboratory studies on a variety of fish species to increase our understanding of the behavioral and physiological characteristics that influence an animal's sensitivity to toxicants which may affect reproductive processes. Such research is extremely important to evaluate the potential impact of degradation of marine estuaries on marine fish populations (Chambers in press). Studies that will enhance our ability to identify species which may be at risk for contaminant-induced reproductive impairment are critical to successful conservation and management of marine fish populations. 
CONCLUSIONS- In general, winter flounder from sites within Boston Harbor and Raritan   Bay showed greater evidence of contaminant exposure than winter flounder from   nearby, less urbanized embayments, based on levels of FACs in bile,   concentrations of PCBs in tissues, levels of xenobiotic-DNA adducts in the   liver, and prevalences of hepatic lesions.       
- Hepatic AHH activity was significantly depressed in gonadally maturing   female winter flounder, even in animals collected in October which were in   early stages of vitellogenesis. Because of the strong influence of   reproductive status on AHH activity, it showed little correlation with other   indicators of contaminant exposure and was not elevated in winter flounder   from Boston Harbor or Raritan Bay sites. This finding suggests that hepatic   AHH activity is not a reliable indicator of contaminant exposure in   vitellogenic winter flounder.       
- Significant relationships were observed between several classes of   idiopathic liver lesions in winter flounder and indicators of exposure to   contaminants in the environment. Pathological conditions were most likely to   occur in fish from sites in urban estuaries where concentrations of aromatic   and chlorinated hydrocarbons in sediment were high. Moreover, prevalences of   two of these conditions (hydropic vacuolation and proliferative liver lesions)   showed significant associations with bioindicators of contaminant exposure,   such as PCBs in tissues, biliary FACs, and levels of xenobiotic-DNA adducts in   liver. Because different classes of contaminants tend to occur together in   sediments, and animals are exposed to a mixture of agents simultaneously, it   is difficult to evaluate the roles that these compounds might play in the   etiology of liver disease on the basis of epidemiological data alone. However,   the associations between tissue contaminant levels and liver pathology   observed in this study provide evidence for the involvement of environmental   contaminants in the development of hepatic lesions, and clearly demonstrate   the utility of these lesions as bioindicators of contaminant exposure in feral   fish.       
- Winter flounder from Boston Harbor and Raritan Bay showed little evidence   of contaminant-associated reproductive impairment. Ovarian growth and   estradiol concentrations in plasma were not depressed in flounder from the   contaminated areas or in flounder with high concentrations of PCBs in tissues   or FACs in bile. It is not clear why these contaminants, which have been shown   to cause reproductive impairment in other fish species, have little apparent   effect on gonadal development in winter flounder. However, migratory patterns   that limit exposure to known reproductive toxicants (e.g., PAHs) at critical   phases of the reproductive cycle, and differences in metabolism of or   sensitivity to these toxicants, could be contributing factors.     
ACKNOWLEDGMENTS
We thank Sin-Lam Chan, Ed Long, and Doug Wolfe for reviewing the manuscript, and Sharon Giese for editorial comments and assistance. These studies were partially supported by the NOAA Coastal Ocean Program and by the Office of Ocean Resources Conservation and Assessment (NOAA National Ocean Services), as part of the National Status and Trends Program. 
Table of Contents