485 Effects of Chemicals and Pollution on Seabirds Joanna Burger and Michael Gochfeld CONTENTS 15.1 Introduction 486 15.1.1 Exposure Assessment 487 15.1.2 Statistical Power 487 15.2 Seabirds as Bioindicators 487 15.3 Seabird Vulnerability and Susceptibility 489 15.3.1 Exposure and Food Chain Vulnerabilities 489 15.3.2 Age- and Gender-Related Vulnerabilities 489 15.3.3 Family Vulnerabilities 490 15.3.4 Individuals vs. Populations 490 15.4 Chemicals and Their Effects on Seabirds 492 15.5 Metals 492 15.5.1 Cadmium 493 15.5.2 Lead 494 15.5.2.1 Lead on Midway 494 15.5.2.2 Effects in Larids in the New York–New Jersey Harbor 495 15.5.3 Mercury 498 15.5.4 Selenium 499 15.6 Organochlorine Compounds 500 15.6.1 DDT and Egg-Shell Thinning 502 15.6.2 Other Cyclodiene Pesticides 503 15.6.3 PCB 503 15.6.4 Dioxins and Dieldrin 505 15.6.5 Selected Syndromes 506 15.6.6 Toxic Equivalency Factors 506 15.7 Petroleum Products 507 15.7.1 Polycyclic Aromatic Hydrocarbons 507 15.7.2 Oil Spills and Oiling 507 15.8 Plastics, Floatables, and Artefacts 509 15.9 Investigating Contaminant Effects 511 15.10 Temporal Trends 513 15.11 Future Research Needs and Conclusions 513 Acknowledgments 514 Literature Cited 514 15 © 2002 by CRC Press LLC 486 Biology of Marine Birds 15.1 INTRODUCTION In a world where the use of chemicals is increasing daily, in industry, on farms, and in homes, levels of many chemicals are elevated in marine and coastal environments. There remain many threats from local point-source polluters such as industries, water treatment plants, and sewage outfalls, as well as from nonpoint sources (pollution arising from many locations). Moreover, the threat from long-range atmospheric transport and deposition is increasing as many chemicals from power plants and industries are transported to all regions, including the Arctic and the Antarctic (Houghton et al. 1992). Aquatic and marine environments are particularly at risk because of the rapid movement of contaminants in water, compared to movement in terrestrial environments. Marine birds are exposed to a wide range of chemicals and other forms of pollution because they spend most of their time in aquatic environments where they are exposed by external contact, by inhalation, and particularly by ingestion of food and water (Figure 15.1). The major groups of pollutants of concern are chlorinated hydrocarbons, metals, petroleum products, plastic particles, and artefacts. Recently attention has focused on a much wider range of industrial and agricultural compounds which may be bioactive, including those that interact with the endocrine system. The potential impact of a pollutant occurs both at the individual and the population levels. Whether a pollutant causes an effect depends on intrinsic toxicity and exposure. For exposure to occur, there must be contact to a substance that is readily bioavailable, which must gain access from the external environment to target organ systems, which usually requires absorption into the blood stream. The amount absorbed and the intrinsic toxicity of the substance determine the toxic impact on target organs, and this is in turn modified by the susceptibility of individuals to toxic effects. We distinguish susceptibility (an intrinsic property of the receptor organism based on genetics, nutritional status, and state of health) from vulnerability (whether it is likely to be exposed to a significant dose based on location, ecology, and behavior). However, these terms are often used interchangeably. Since different families of seabirds, and different species within these fam- ilies, have different life cycles, behavior, ecologies, and habitat uses, their vulnerability varies. Further, as with other animals, susceptibility varies with age, reproductive stage, and gender. In this chapter, we review why seabirds are particularly vulnerable, examine why some families are more vulnerable than others, describe the methods of assessing potential effects of pollution, FIGURE 15.1 Pathways of exposure for seabirds in air, soil, water, and food. Contaminations Exposure in Seabirds INHALATION INGESTION INJECTION DERMAL Dust Dust Droplet Aerosols DUST PREENING LEAD SHOT Dust on Food Grit/Lead Shot Drinking All Foods Inadvertent through grit shot or other objects in food Absorption through legs while swimming Air Soil Water Food © 2002 by CRC Press LLC Effects of Chemicals and Pollution on Seabirds 487 describe the types of pollutants with their major effects, discuss exposure and uptake, and examine cases where pollutants affect individual reproductive success, survival, and population levels. Finally, we discuss future research needs and data gaps. Major advances in understanding the concentrations, distribution, and effects of pollutants have occurred since the mid-1970s (Burton and Statham 1990, Beyer et al. 1996). There is a rich literature on pollutants in birds which can be roughly assigned to four major categories: laboratory studies, residue measurements in sick or dead birds, surveys of contaminants in a species, and finally, recently emerging studies in a risk assessment framework. 15.1.1 EXPOSURE ASSESSMENT An important aspect of pollutant effects on seabirds lies in exposure assessment. The pathway from source to environmental fate and transport, food chain bioamplification, contact, intake, bioavail- ability and absorption, metabolism, transport, and excretion and distribution within the body ultimately determines the dose delivered to a target organ. Since many of the contaminants discussed in this chapter are taken up and stored in tissues, tissue levels can be used as biomarkers of exposure and of possible effects on the seabirds themselves (Peakall 1992, Nisbet 1994). The time frame of exposure is important. Exposures can be acute or chronic. Acute exposure to a contaminant will have a different impact than chronic ingestion of small quantities, even when the same total dose is achieved. The effects of contaminants may also be acute and short-lived such that once exposure has ended, there is no further risk (e.g., organophosphates). Or the substance may accumulate or produce a cumulative effect so that the impact may not be apparent until long after the exposure has begun, or in some cases, even after it has terminated (e.g., organochlorines, some heavy metals). Once exposure has ended, and there are no effects apparent, the likelihood of subsequent effects begins to decline (see Eaton and Klaasen 1996, Gochfeld 1998). 15.1.2 S TATISTICAL P OWER Most studies that consider statistically significant differences in contaminant residues from among localities, species, tissues, age classes, or sexes, rely on the traditional alpha = 0.05 level. There is no a priori basis for relying on this particular value. In many cases, studies involving a few individuals lack the statistical power to identify differences that may be real. Conversely, differences that are statistically different may represent sampling artefacts. Both phenomena should be con- sidered in interpreting research or planning new studies. The National Research Council (NRC 1993) has encouraged reliance on a weight-of-evidence approach, which recognizes that although each study may have some problems, it is prudent to examine the totality of evidence from a meta-analysis approach. For example, if a dozen studies of a substance all show an excess of a particular endpoint, the weight of evidence approach supports a relationship even if none achieved “statistical significance.” 15.2 SEABIRDS AS BIOINDICATORS A few groups of birds, raptors, waterfowl, and seabirds, dominate the contaminant literature. Seabirds offer the advantage of being large, wide ranging, conspicuous, long lived, easily observed, and important to people. They are often at the top of the food chain where they can be exposed to relatively high levels of contaminants in their prey. Since many species of seabirds are philopatric, returning to the same nest site and colony site for years, contaminant loads of individuals can be studied (Burger 1993). Although many seabird populations are already threatened or endangered through habitat loss, exploitation, overfishing, and other anthropogenic impacts (Croxall et al. 1984; Chapters 8, 16, 17), populations of many species are robust, and the collecting of limited individuals does not pose a conservation problem. © 2002 by CRC Press LLC 488 Biology of Marine Birds While contaminant levels can be examined in seabirds as an indication of potential harm to the seabirds themselves, seabirds have also been used as bioindicators of coastal and marine pollution (Hays and Risebrough 1972, Gochfeld 1980b, Walsh 1990, Peakall 1992, Furness 1993, Furness and Camphuysen 1997). They have been used to assess pollution over local, regional, or wide-scale geographical areas as well to determine whether levels of contaminants have changed over time (Walsh 1990). Feathers in museum collections have been used to examine changes in mercury levels over centuries (Berge et al. 1966, Thompson et al. 1992). Seabirds are bioindicators for local, regional, and global scales, and can integrate over both spatial and temporal scales. Seabirds have proven particularly useful as bioindicators for contamination in the Great Lakes (Fox 1976, Mineau et al. 1984, Weseloh et al. 1995, Pekarik and Weseloh 1998). Like any bioindicator, there are advantages and disadvantages of using seabirds. Seabirds are excellent bioindicators because they are sensitive to chemical and radiological hazards and are widespread over the world in coastal and marine habitats where pollution is often great and where contaminants are transported rapidly through aquatic systems and within food chains. They “inte- grate” contamination over time and space (Walsh 1990, Burger 1993). Since seabirds travel over substantial distances to obtain food, they sample prey from different regions, and the resultant levels in their tissues are an indication of contamination over that area. Sampling contaminants in seabirds is often more cost effective than sampling water, sediment, or invertebrates, because those samples represent only the small number of points or locations sampled. To sample a large bay or estuary, many points are required to obtain a picture of pollutant levels, with serial samples needed to capture seasonal fluctuations. However, by sampling only a few seabirds, it is possible to determine whether there is a problem in the bay generally. The advantage of using seabirds to integrate over space and time, however, is also a disadvan- tage. If high levels of any contaminant are discovered in seabirds, then it is necessary to understand the life cycle, migration routes, prey base, foraging range, and habitat of the seabird. Knowing contaminant loads in a seabird will not normally identify the exact location of point-source pollution; further sampling of other bioindicators is required. With an understanding of the prey consumed by seabirds, it is possible to determine where they might have foraged, thus identifying potential sites of high contamination. Finally, it is important to understand the migratory behavior of seabirds before interpreting contaminant levels. Sedentary species reflect local levels of pollution, but for migratory species it is essential to know how long the seabirds have been in the local area. Some of the disadvantages discussed above can be ameliorated by using eggs or young seabirds as bioindicators. Coastal-nesting species of seabirds often arrive at the breeding colony a month or more before laying eggs, and the contaminant loads in eggs largely reflect local exposure. Species that nest on oceanic islands, however, may arrive only a few days before egg laying, and thus levels in their eggs do not reflect local exposure. Young birds that have not yet fledged have obtained all of their food from their parents, who usually obtained it from the local area. Exceptions are albatrosses and some petrels that might have traveled several hundred kilometers to obtain food (Fisher and Fisher 1969, Weimerskirch 1997). Studies of contaminants in seabirds have examined the internal tissues (liver, brain, kidney, and muscle) of adult and young birds, eggs (both viable and nonviable), and young chicks. Each kind of tissue addresses different questions. Since feathers have been used so often to examine levels of metals, we will describe briefly why they work for metals and not for other substances. Feathers are rich in disulfide bonds that are readily reduced to sulfhydryl groups that bind to metals. As feather protein is laid down, it becomes a chelator that binds and removes metals from the blood supply. Metal levels in a feather reflect circulating blood levels during the 3- to 4-week period when a feather is forming (Bearhop et al. 2000). Thereafter, the blood supply atrophies, leaving the feather as a permanent record of blood levels, for many years or centuries if specimens are in permanent collections. The blood levels of heavy metals are a result of current exposure and metals mobilized from other internal tissues (Burger 1993). Thus the molt cycle and the location of seabirds during feather © 2002 by CRC Press LLC Effects of Chemicals and Pollution on Seabirds 489 formation must be known before feather levels can be interpreted. Using feathers from prefledging seabirds is a useful method of ascertaining local levels since parents obtained the food within foraging distance of the colony. The utility of feathers hinges on the high affinity of metals for the sulfhydryl group of the structural protein melanin. Organic pollutants do not have this same affinity, and do not concentrate in feathers. An issue with feathers is whether the metals in the feather have been delivered by the blood supply (a reflection of internal exposure) or deposited superficially from atmospherically transported contamination. Vigorous washing will remove loosely adherent contamination but not necessarily metals bound to the protein (regardless of their origin). When individuals in the same population exposed to similar atmospheric deposition show great differences in feather levels of a metal, we infer that the difference is largely due to internal rather than external deposition. 15.3 SEABIRD VULNERABILITY AND SUSCEPTIBILITY Different seabirds are affected by pollutants in different ways depending upon breeding schedules, foraging methods, geographical ranges, and life history strategies (see Chapter 8). Species, such as seabirds, that are long lived have longer to accumulate toxics than do shorter-lived species. Further, seabirds that lay fewer eggs may well deposit higher levels in their one egg. All seabirds are not equally vulnerable to contaminants even when exposed to the same levels in their food or water because they do not eat the same proportions of any given prey and they have varying abilities to excrete, metabolize, or sequester xenobiotics. Understanding the relative role of each of these differences requires controlled laboratory experiments on toxicodynamics (the movement of chem- icals between and among organs and compartments of an animal), as well as extensive field studies. Toxicodynamic studies have been conducted for mercury (Braune 1987, Lewis and Furness 1991), organochlorines (Clark et al. 1987), and plastic particles (Ryan 1988a, b). Burger (1993) provides a table of the ratio of metal levels among tissues for seabirds, which can be used to assess which tissues concentrate which metals. There are other vulnerabilities that include differences in expo- sure, location on the food chain, age, or gender. 15.3.1 EXPOSURE AND FOOD CHAIN VULNERABILITIES Since seabirds have a patchy distribution over a wide range of spatial and temporal scales (Schneider et al. 1988), exposures can vary widely. Levels in tissues are a function of uptake and absorption and how and where each pollutant is stored in different tissues. Uptake is a function of exposure and intake rates. For contaminants to be taken in, they have to be bioavailable to the organisms, otherwise they are excreted and are not absorbed into the bloodstream nor distributed to the tissues. If the contaminant is not bioavailable it will not be incorporated into the tissues, and thus high levels in soil or water may not be biologically relevant. Once contaminants are in aquatic systems, they enter the food chain where some are biomag- nified at each transfer from prey to predator (Hahn et al. 1993). At every step, organisms take in more of a substance than they excrete, resulting in a net increase in the concentration of that substance in their tissues during their lifetime. Top-level carnivores and piscivores can have much higher levels of contaminants than organisms that are lower on the food chain (Hunter and Johnson 1982, van Strallen and Ernst 1991). Ideally, food-chain effects should be examined by evaluating the levels of contaminants in known food chains, which might include water, invertebrates, small fish, squid, large fish, and seabirds. Alternatively, food chain effects can be examined by measuring contaminant levels in a range of seabirds that represent different trophic levels. 15.3.2 AGE- AND GENDER-RELATED VULNERABILITIES Young seabirds usually have lower levels of contaminants than adults. A summary of metal levels in feathers (Burger 1993) showed that adults had significantly higher concentrations than young © 2002 by CRC Press LLC 490 Biology of Marine Birds for mercury (20 of 21 studies), lead (4 of 7), cadmium (3 of 5), manganese (5 of 5), and selenium (3 of 3), with chromium showing less of a difference (only 1 of 4 studies). Since then, age-related differences in some metals were found for other species (Thompson et al. 1993, Gochfeld et al. 1996, 1999, Burger 1996, Stewart et al. 1997, Burger and Gochfeld 1997a, b, Burger and Gochfeld 2000a, b). Differences between adults and young depend on the contaminant and the species being studied. Age-related differences are not consistent for cadmium or manganese, and generally do not occur for chromium (Burger 1993). Few studies have examined differences in metal levels of internal tissues as a function of age. Furness and Hutton (1980) reported that cadmium levels in liver increased with age in Great Skua (Catharacta skua). In Laughing Gulls (Larus atricilla) from the New York City area, Gochfeld et al. (1996) reported that selenium and mercury decreased with adult age, and cadmium levels increased with age. In Franklin’s Gull (Larus pipixcan) from northern Minnesota, chicks generally had lower levels of metals in tissues than adults (Burger and Gochfeld 1999). Young might be exposed to higher levels of certain metals if adults feed different food to their offspring than they eat themselves. Adult Laysan Albatrosses (Diomedea immutabilis) from Midway Atoll in the northern Pacific Ocean had higher levels of cadmium, selenium, and mercury in most tissues (Burger and Gochfeld 2000a). However, chicks had higher concentrations of manganese in liver and arsenic in salt glands, than did adults. Lock et al. (1992) examined cadmium, lead, and mercury in the feathers, liver, kidney, and bone of adults and juveniles of some seabirds, including several albatrosses, in New Zealand. There were significant age differences, with adults having higher levels of cadmium and mercury in the liver than did young birds. For the metals and tissues examined at both New Zealand and Midway, the concentrations of cadmium were similar, but mercury levels were up to three times higher in the New Zealand albatrosses. The New Zealand and Midway data suggest that albatrosses may be less sensitive to mercury than smaller species of birds that show reproductive effects at liver concentrations of 2 ppm in laboratory studies (Scheuhammer 1987). These two studies on albatrosses indicate the value of data on contaminants in the same species from different parts of the world. Less is understood about gender-related differences in contaminant levels and effects, largely because birds collected outside the breeding season are difficult to sex (gonads have recrudesced); sexually monomorphic species (i.e., most seabirds) are often not possible to sex. Comparing contaminant levels in females and males is very important, however, since females have an addi- tional route of excretion (to the eggs) that males do not have, which constitutes a major reproductive vulnerability. There does not seem to be any clear pattern, at least in metal levels in feathers, although this requires more study with more species (Burger 1993). 15.3.3 FAMILY VULNERABILITIES Some families of seabirds are more vulnerable to pollution than others because of their foraging method, prey, or nesting habitat. Most gulls, most cormorants, and some terns and alcids are exposed to high levels of pollutants because they nest near shore in close proximity to sources of industrial or agricultural pollution (Mailman 1980, Fowler 1990). Within families, species may differ in their ability to rid themselves of contaminants, as Henriksen et al.(2000) suggested for Glaucous Gulls (Larus hyperboreus) compared with Herring Gulls (Larus argentatus). 15.3.4 I NDIVIDUALS VS . P OPULATIONS The focus of early studies of the effects of pollutants on birds centered on direct mortality (Bellrose 1959), although recent work has demonstrated a wide range of sublethal effects on development, physiology, and behavior of individuals. Sublethal effects of pollutants on seabirds include repro- ductive deficits (Ashley et al. 1981), teratogenicity and embryotoxicity (Hoffman 1990), eggshell © 2002 by CRC Press LLC Effects of Chemicals and Pollution on Seabirds 491 thinning (Risebrough 1986), enzyme induction (Fossi et al. 1989, Ronis et al. 1989), effects on endocrine function (Peakall et al. 1973, Peakall 1992), and behavioral abnormalities of adults and young (Burger and Gochfeld 1985, 2000c, Burger 1990). These sublethal effects on overall repro- duction, survival, and population dynamics are not well understood, and effects, particularly if localized, do not necessarily lead to population declines. It is difficult to assess the toxic effects of contaminants on seabird populations because seabirds are long-lived and a population is made up of many overlapping generations. Even the dramatic losses due to a massive oil spill that might eliminate an entire age cohort of young birds may not be obvious if such losses are compensated by improved reproduction and survival of remaining birds, enhanced recruitment from a pool of nonbreeders, or immigration from birds nesting in nearby colonies. Establishing cause-and-effect requires a series of discrete steps in a chain involving both laboratory tests and field observations (Gilbertson 1990, Fox 1991; Figure 15.2). It involves identifying the hazard (types of effects or endpoints), determining exposure and bioavailability of the chemical, estimating dose–response relationship for each endpoint, and examining overall effects on individuals and populations. Establishing these links cannot be done without both laboratory and field experimentation. In 1991 Fox applied the Bradford Hill postulates (Hill 1965) used by epidemiologists to establish causal relationships for humans to ecotoxicology. These criteria for evaluating the relationship between a contaminant and an observed health effect include the strength and consistency of the association between an outcome and its putative cause, the temporal relationship (exposure must precede effect), the biological plausibility based on knowledge of toxicology and biology, the ability to replicate the relationship, and its predictability (does the endpoint occur in other situations where the exposure occurs). Toxicologists establish the links between cause and effect, but seldom examine the overall ecological relevance of these effects. Seabird biologists, on the other hand, must examine a wide range of sublethal effects on reproduction and survival of populations (Figure 15.3). This model, developed for lead (Burger 1995), shows how reproduction and survival can be affected by a substance, leading to declines in populations. While it is possible to establish an effect of pollutants on local populations, it is more difficult to demonstrate that these effects have led to regional or FIGURE 15.2 Methods to establish cause-and-effect relationship of chemicals and adverse outcomes in seabirds. This is an ecological risk-assessment methodology. Links to Determine Effects Hazard Identification Exposure Assessment Bioavailability DOSE - Response Effects on Individuals & Populations © 2002 by CRC Press LLC 492 Biology of Marine Birds worldwide declines in a species. We do not, however, believe that it is necessary to prove this last link because seabirds, like other animals, have evolved mechanisms to deal with such perturbations, and unless the level of pollution is similar worldwide, worldwide effects would not be expected. 15.4 CHEMICALS AND THEIR EFFECTS ON SEABIRDS The major categories of pollutants that we deal with in this chapter are metals and metalloids, organochlorine compounds, polyaromatic hydrocarbons and petroleum products, plastics, and float- ables (Table 15.1). We do not deal with substances that are primarily acutely toxic such as the organophosphate pesticides. Space also precludes our dealing with radionuclides, although there is a growing literature on various radioisotopes in seabirds as analytic techniques become available. Seabirds can acquire radionuclides from discharges from fuel reprocessing plants (Woodhead 1986) or from nuclear testing fallout (Noshkin et al. 1994). For a review of the effects of radionuclides on birds see Brisbin (1991). 15.5 METALS Cadmium, lead, and mercury are the primary metals of concern for oceanic and estuarine environ- ments (Fowler 1990), and thus for seabirds, while selenium is of concern for those seabirds that nest inland (Ohlendorf et al. 1986). Other elements such as arsenic bioaccumulate as organic compounds with apparently relatively low toxicity. Metals are present naturally in the earth’s crust and in seawater (Wong et al. 1983), but the contributions from anthropogenic sources are increasing (Schaule and Patterson 1981). For seabirds that breed along coasts, local anthropogenic sources of FIGURE 15.3 Model for establishing toxicity for contaminants. Shown are links (arrows) where sublethal and lethal effects can be demonstrated, leading to population declines if the effects are severe enough. (After Burger 1995.) Prey Base Habitat Adults Reproduction Survival Recruitment to Breeding Adult Population Stability Fledging Success Chick Behavior Chick Growth Nestling Mortality/ Abnormalities Hatching Rate Embryo Mortality Clutch & Egg Size Behavior Physiology Foraging Behavior Other Behavior Survival & Future Reproduction © 2002 by CRC Press LLC Effects of Chemicals and Pollution on Seabirds 493 lead, cadmium, and mercury are a substantial part of their exposure. While other metals, such as chromium (Eisler 1986), are potentially problematic for seabirds, we discuss only cadmium, lead, mercury, and selenium in detail here. 15.5.1 CADMIUM Cadmium is a nonessential metal that can come from a variety of anthropogenic sources such as smelters and from the manufacture and disposal of commercial products such as batteries, paints, and plastic stabilizers (Burger 1993, Furness 1996). It is a relatively rare element in the environment (Wren et al. 1995), and in most of the earth’s crust it is present at levels below 1 ppm (usually less than 0.2 ppm, Farnsworth 1980). Volcanic action is the major natural source of atmospheric cadmium; other natural sources include ocean spray, forest fires, and the releases of particles from terrestrial vegetation (Hutton 1987). Compared to other organisms, cadmium levels are often relatively high in marine organisms, including seabirds (Bull et al. 1977, Furness 1996). Levels seem to be higher among squid-eating seabirds than among those that eat primarily fish (Muirhead and Furness 1988, Thompson 1990) or crustaceans (Monteiro et al. 1998), and this will probably apply to consumption of other molluscs as well (Furness 1996). Cadmium causes sublethal and behavioral effects at lower concentrations than mercury or lead, and causes kidney toxicity in vertebrates and is an animal carcinogen (Eisler 1985a), although little work has been done on seabirds. Effects also include altered behavior, suppression of egg production, egg-shell thinning, and testicular damage (Furness 1996). Stock et al. (1989) suggested that cadmium is regulated metabolically in adult birds, thus cadmium levels do not increase with age. Eisler (1985a) estimated that a kidney concentration of about 10 ppm (wet weight) was associated with adverse effects, based on laboratory studies (Table 15.2). Unlike mercury and most metals where the feather concentration exceeds the kidney concentration, virtually all studies of cadmium have shown kidney:feather ratios substantially greater than 1. The ratios exceed 100:1 in some species of shearwaters (Osborn et al. 1979), while levels in terns range from 5:1 to 10:1 (Burger 1993). Cadmium levels are usually undetectable or very low in seabird eggs, while relatively high cadmium levels have been reported in kidneys and livers of pelagic species, such as petrels, fulmars, prions, albatrosses, penguins, skuas, and alcids, compared to coastal and inshore species (Nisbet 1994). This suggests a natural, oceanic source of cadmium. Furness (1996) suggested that the threshold level above which adverse effects occur in pelagic TABLE 15.1 Major Chemicals and Pollutants of Concern for Seabirds Metals and metalloids Many metals have potent effects on development and the nervous system, including mercury, lead, cadmium, manganese, and selenium. Organochlorine insecticides Many of the chlorinated pesticides or their breakdown products are highly persistent in the environment and in the body (DDT). Polychlorinated di-aromatic compounds (PCB, dioxins) These are highly persistent chemicals, which vary greatly in their toxicity. Effects on the nervous system of some of these compounds are secondary. Organophosphates Organophosphates exert mainly acute nervous-system toxicity by interfering with acetylcholinesterase. There is some evidence of prolonged and even delayed neurotoxicity in survivors; they may break down quickly in the environment and the body. Petroleum products These are complex mixtures of aliphatic and organic compounds. Solvents Of particular concern are short-chain chlorinated aliphatics such as trichloroethylene, tetrachloroethylene, and formerly carbon tetrachloride. Also of concern are aromatic solvents such as toluene and xylene. Plastics and floatables Plastic material and others that float on the ocean surface are of concern. © 2002 by CRC Press LLC 494 Biology of Marine Birds seabirds may be higher than for other birds, and that no adverse cadmium effects have been documented in wild seabirds. 15.5.2 LEAD Lead average concentration in the Earth’s crust is 19 ppm, making it a relatively rare metal (EPA 1980, Pain 1995). Lead also comes from industrial processes, burning of leaded gasoline, storm- water runoff, agricultural practices, eroded lead paint, and to some degree from natural processes such as erosion and volcanism (Eisler 1988, Prater 1995). Lead contamination is ubiquitous; there are no longer natural environmental concentrations because of widespread atmospheric deposition (Pain 1995) and runoff, with contamination of nearshore environments. Lead affects all body systems; organolead compounds are more toxic than inorganic lead compounds, and young animals are more sensitive than older animals (Eisler 1988). In vertebrates, lead poisoning can be chronic or acute, and there is no “no effect” level since the lowest measurable levels affect some biological systems (Franson 1996), although specific effects on seabirds have been studied in only a few species. Lead levels are considered elevated if liver levels are above about 7 ppm (dry weight, Eisler 1988). Lead exposure can cause direct mortality, as well as sublethal effects (Eisler 1988). Early studies focused on waterfowl exposed directly by shooting or indirectly from ingesting lead shot as grit or with food items (Bellrose 1959). Symptoms of lead poisoning include drooped wings, loss of appetite, lethargy, weakness, tremors, impaired locomotion, balance and depth perception, and other neurobehavioral effects (Sileo and Fefer 1987, Eisler 1988, Burger and Gochfeld 1994, 1997a). 15.5.2.1 Lead on Midway In the mid-1980s, lead poisoning due to ingestion of lead paint from buildings was reported for Laysan Albatross chicks from Midway Atoll (Sileo and Fefer 1987, Sileo et al. 1990, Work and Smith 1996). Some chicks that hatched near buildings exhibited symptoms that included drooping wings, weight loss, and death (Figure 15.4). Sileo and Fefer (1987) reported that paint chips with up to 144,000 ppm lead were found in the proventriculus of affected chicks. Acid-fast intranuclear inclusion bodies were present in the kidneys, and degenerative lesions were present in the myelin of some brachial nerves in affected chicks. Further, in 1997, albatross chicks near buildings that exhibited droop-wings (some of which died), had mean lead levels of 4.7 ppm wet weight in the TABLE 15.2 Levels (ppm, dry weight) of Metals Associated with Adverse and Toxic Effects Liver Kidney Feathers Source Cadmium >5 10 ? b Eisler 1985 Lead >5 a >15 4 a Custer and Hohman 1994 Burger and Gochfeld 2000c Ohlendorf 1993 Mercury >6 >6 5 Ohlendorf 1993 Eisler 1987 Selenium 9 >10 ? b Heinz 1996 Ohlendorf 1993 a For seabirds. b Unknown. © 2002 by CRC Press LLC [...]... Effects of Chemicals and Pollution on Seabirds 499 2100 White Tern Bonin Petrel Christmas Shearwater Young - Midway Red-tailed Tropicbird Laysan Albatross Black-footed Albatross Common Tern Roseate Tern Young - Azores Yellow Legged Gull Cory's Shearwater Black Skimmer - Barnagat - West - Tow Roseate Tern - Cedar '91 - Cedar '92 Young - NY Bight - Cedar Common Tern - Pettit Herring Gull Adverse Effects -. .. behavior, embryotoxicity, or a combination of the two Mora et al (1993) reported that nest-site tenacity of Caspian Terns (Hydroprogne caspia) in the North American Great Lakes was inversely associated with concentrations of PCB in the blood of the © 2002 by CRC Press LLC 504 Biology of Marine Birds TABLE 15. 4 Seabirds in Which Certain Effects of Endocrine-Disrupting Chemicals such as PCB from the... Natural Offshore Transport Seeps Production Tanker Coastal Tanker Operations Facilities Accidents FIGURE 15. 14 Sources of oil into marine waters Note that the highest percentage of oil comes from runoff from rivers into oceans, but tanker operations are second (After Burger 1997.) © 2002 by CRC Press LLC 508 Biology of Marine Birds FIGURE 15. 15 Laysan Albatross on Midway with a small patch of oil on... Rev Report EPS-3-EC-82L), Ottawa BULL, K R., R K MURTON, D OSBORN, AND P WARD 1977 High levels of cadmium in Atlantic seabirds and sea-skaters Nature 269: 507–509 BURGER, A E., AND D M FRY 1993 Effects of oil pollution on seabirds in the northeast Pacific Pp 254–263 in The Status, Ecology, and Conservation of Marine Birds of the North Pacific (K Vermeer, K T Briggs, K H Morgan, and D Siegel-Causey, Eds.)... Taxa of Marine Birds Albatross lead levels include individuals with evidence of lead poisoning Otherwise highest mean is 3.1 501 © 2002 by CRC Press LLC 502 Biology of Marine Birds Gilbertson 1989, Gilbertson et al 1991) Recent studies have demonstrated that some isomers of PCB, PCDF, and PCDD are up to 1000 times more toxic than others (Safe 1990) In addition to the well-documented effect on egg-shell... effects of organochlorines on thyroid hormone have profound effects on neurological function, © 2002 by CRC Press LLC 506 Biology of Marine Birds which are similar to the endocrine disruption mechanism for the observed behavioral changes in birds (Porterfield 1994) However, little experimental evidence is present for birds, and none exists for seabirds (Janz and Bellward 1996) Finally, the difficulty of assessing... concentrations of certain PCB congeners (co-planar isomers) are associated with both embryo lethality and greater rates of congenital deformities (Giesy et al 1994a, b; Table 15. 4), including chicks born with extra legs, a variety of craniofacial abnormalities such as crossbill (Hoffman et al 1987, Figures 15. 10 and 15. 11) Similar deformities, as well as feather abnormalities, eggshell thinning, cross-bills,... account for the lowered reproductive success and survival of rehabilitated, oiled birds (Morant et al 1981) The best-studied example of the long-term effects of oil is the Exxon Valdez Analyses of marine bird surveys conducted in Prince William Sound in 1972 before this spill, and in 1989, 1990, 1991, and 1993 indicated that several marine birds that eat fish declined, while those that fed on benthic... (2) comparison of field levels known to cause adverse effects in the laboratory, albeit in nonseabirds In Table 15. 3 we give the mean levels of several metals in the feathers of several seabirds, and compare them to those in some other nonseabirds (Burger 1993) Although such a table could be produced for other tissues, there are far fewer data because of the difficulties of collecting seabirds for tissue... exceed the effects level (Monteiro et al 1998) Terns had some of the lowest levels The levels of mercury in young seabirds from the east coast of North America (bottom of Figure 15. 8) are not as high generally as those from the more pelagic sites 15. 5.6 SELENIUM Relatively high concentrations of selenium in the kidneys and liver of dying waterbirds are associated with symptoms such as hepatic lesions, . Skimmer - Barnagat - West - Cedar '91 - Cedar '92 - Cedar - Captree '90 - Captree '92 - Captree '93 - Pettit - Tow © 2002 by CRC Press LLC 500 Biology of Marine Birds adult. LLC 490 Biology of Marine Birds for mercury (20 of 21 studies), lead (4 of 7), cadmium (3 of 5), manganese (5 of 5), and selenium (3 of 3), with chromium showing less of a difference (only 1 of 4. LLC Effects of Chemicals and Pollution on Seabirds 501 TABLE 15. 3 Metal Levels by Major Taxa of Marine Birds Mercury Cadmium Lead Range of Means Median of Means No. of Data Sets Range of Means Median of Means No.