Clements: “3357_c002” — 2007/11/9 — 18:25 — page 11 — #1 Part II Organismal Ecotoxicology Conventionalities are as bad as impurities. Uncommon Learning (H.D. Thoreau 1851) Organismal ecotoxicology explores toxicant effects to individuals and, where possible, links them to effects to populations and communities. Such exploration has been at the center of ecotoxicology and its predecessors (aquatic, wildlife, and environmental toxicology) since their inceptions. Because of our proclivity toward study of toxicant effects to the soma—the body of the individual organism— much in this section should be comfortably familiar to the professional ecotoxicologist or advanced student. What might not be as familiar will be the focus on fundamental principles and linkage of these effects to those at higher levels of biological organization. The preoccupation of ecotoxicologists with the soma emerges from the historical foundations of our new science. It is obvious during even a cursory examination of the most popular ecotoxicology textbooks (e.g., Cockerham and Shane 1994, Connell et al. 1999, Landis and Yu 1995, Newman 1998, Walker et al. 2001) that many basic concepts and techniques blended into ecotoxicology come from mammalian toxicology, a field with a justifiable emphasis on the individual. Still other concepts and techniques come from classic autecology. Used with balance and insight, this offers several advantages to the field. Ecotoxicologists can draw deeply from the mechanistic knowledge base of classic toxicology, a field focused on individuals. This knowledge is directly useful for charismatic, endangered, or threatened species that are protected by prohibiting the taking of even a single individual. It also provides a firm base at one level of biological organization from which to extend scientific insight upward to the next. The mechanistic andtechnological richness of classic toxicology and autecology comes at a price. The paradigms around which phenomena are explored by ecotoxicologists are often those associ- ated with the soma. Exploration of other important ecotoxicological phenomena are unintentionally addressed with less intensity or quietly dismissed as secondary. The rich technology associated with organismal toxicology naturally draws practitioners to these tools. The result is a rapid enrichment of the field: an enrichment that also maintains the present imbalance. Resolution of this incongru- ity requires application of concepts and technology in a way that does not foster any unintentional © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 12 — #2 12 Ecotoxicology: A Comprehensive Treatment neglect of higher levels of organization and with the intent of producing predictive insight about phenomena at higher levels of organization. That is the intent of this section. REFERENCES Cockerham, L.G., and Shane, B.S., Basic Environmental Toxicology, CRC Press, Boca Raton, FL, 1994. Connell, D., Lam, P., Richardson, B., and Wu, R., Introduction to Ecotoxicology, Blackwell Science Ltd., Oxford, UK, 1999. Landis, W.G., and Yu, M H., Introduction to Environmental Toxicology, CRC Press, Boca Raton, FL, 1995. Newman, M.C., Fundamentals of Ecotoxicology, CRC Press/Lewis, Boca Raton, FL, 1998. Thorean, H.D., Uncommon Learning, Bickman, M. (ed.), Houghton, Mifflin, Co., Boston, 1851. Walker, C.H., Hopkin, S.P., Sibly, R.M., and Peakall, D.B., Principles of Ecotoxicology, Taylor & Francis, New York, 2001. © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 13 — #3 2 The Organismal Ecotoxicology Context 2.1 OVERVIEW The science of ecotoxicology has grown rapidly in 30 years and has brought together a vast body of facts around several explanatory systems. Explanatory systems were borrowed in necessary haste from mammalian toxicology and ecology. The immediacy of our environmental problems required this haste. Required now is coherence among the clusters of explanatory hypotheses that are rapidly coalescing at each level of biological organization. Together, these paradigms form the foundation for ecotoxicological theory. 1 If these paradigms are not made mutually supportive, the foundation of ecotoxicology will not be adequate to support further knowledge accumulation and organization. The field will break into semi-isolated scientific disciplines. Conceptual consilience is not an intellectual nicety: it is vital to the health of any science. Without consistency among theories and facts, there is no way for the ecotoxicologist to choose from among many the explanation providing the best foundation for predicting pollutant effects. The requirement of consistency will be appreciated if one realizes that a self-contradictory system is uninformative. It is so because any conclusion we please can be derived from it. Thus no statement is singled out, either as incompatible or as derivative since all are derivable. A consistent system, on the other hand, divides the set of all possible statements into two: those which it contradicts and those with which it is compatible . This is why consistency is the most general requirement for a [scientific] system if it is to be of any use at all. (Popper 1959) As articulated by Popper, sciences lacking self-consistency are not viable. Ecotoxicological explanations need to be consistent among all levels of organization or the science of ecotoxicology will eventually fail to be useful. Beyond this, efforts spent finding consistency have another desirable effect relative to scientific logic. It can identify common causes for phenomena described at different levels of biological organization. The identification of a common cause allows the overall number of theories to be reduced. Why have two distinct theories to explain the same thing? The parsimony resulting from theory reduction—that is, intertheoretical reduction (Rosenberg 2000)—enhances any science and is particularly warranted in ecological sciences (Loehle 1988). A final reason exists for the emphasis on integrating explanatory systems from different levels of biological organization. Not doing so allows the current condition to remain in which an ecotox- icologist trying to describe and solve a particular environmental problem may present and defend findings based on contradictory explanations. This diminishes the legal defensibility of arguments 1 Definitions of Rosenberg (2000) are being used in this discussion. A set of explanatory principles or paradigms comprise the established scientific theory of a discipline, for example, evolutionary theory contains many explanatory principles such as genetic drift or natural selection. The paradigms have withstood rigorous testing and currently provide the best causal explanation of natural phenomena, for example, evolution theory explains genetic change in a population exposed to a toxicant. 13 © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 14 — #4 14 Ecotoxicology: A Comprehensive Treatment calling for costly remediation. It also increases the risk of pathological science, science practiced with an excess loss of objectivity (Langmuir 1989, Rousseau 1992). It is a fault which can be observed in most disputes, that, truth being mid-way between the two opinions that are held, each side departs the further from it the greater his passion for contradiction. (Descartes, translated by Sutcliffe 1968) Integration, combined with differentiation, is a major theme here because it fosters the identifica- tion of causal mechanisms that are consistent among levels of organization, is logically necessary in any healthy science, fosters resolution of environmental issues, and decreases the tendency toward pathological science. 2.2 ORGANISMAL ECOTOXICOLOGY DEFINED 2.2.1 W HAT IS ORGANISMAL ECOTOXICOLOGY? Every species of plant is a law unto itself, the distribution of which in space depends upon its individual peculiarities of migration and environmental requirements. It grows in the company with any other species of similar environmental requirements, irrespective of their normal associational affiliations. (Gleason 1926) The scope of ecotoxicology is so necessarily encompassing that an ecotoxicologist can study fate or effect of toxicants from the molecular to the biospheric scales. This book attempts to discuss this wide range of topics. The focus of attention in this particular section is organismal ecotoxicology, the science of contaminants in the biosphere and their direct effects on individual organisms. The prominence of the organismal context is so long-standing and familiar to ecologists that it has its own name, autecology. Autecology is the study of the individual organism or species, and its relationships to its physical, chemical, and biological environment. The quote above from Gleason’s classic paper articulates the autecological framework. The boundaries of autecology are often vague. Since its origins, autecology has been described as either distinct from (e.g., Emmel 1973) or synonymous with (e.g., Reid 1961) population ecology. In reality, it overlaps with population ecology but tends to characteristically emphasize species requirements, physiological tolerances, means of adaptation, and life history traits, and how these influence success or failure in certain environs. It emphasizes the soma and how it manages to survive. For example, a wildlife manager concerned with a specific game bird species might take an autecological vantage to managing that particular species. Another example of an autecological topic might be how the physiological tolerances of an estuarine crab relative to salinity and temperature influence its spatial distribution within an estuary. Astudy by Costlow et al. (1960) is a classic one of this sort (Box 2.1) in which tests of the physiological limits of individuals were used to suggest that salinity confines the spatial distribution of an estuarine crab. The emphasis is plainly on qualities of individuals, not complex interactions among species or even the interactions among individuals in populations of this crab species. 2 Several fundamental laws of ecology emerge from this context. Liebig’s law of the minimum (Liebig 1840), first formulated to explain how nutrients limit plant standing crop, states that the factor in the shortest supply of all required factors will limit the number or amount of individuals that a 2 In contrast to autecology, the subdiscipline of ecology focused on the integrated interactions of groups of individuals within an environment is called synecology. Conventional topics of synecology are discussed principally in the last sections of this book. The population ecotoxicology section is the boundary between autecology and synecology, and covers a blend of autecology with some synecology. © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 15 — #5 The Organismal Ecotoxicology Context 15 Box 2.1 Autecology of a Crab: Physiological Tolerances Determine Adult Distribution Costlow et al. (1960) reared larvae of the estuarine crab, Sesarma cinereum, at different combin- ations of salinity and temperature, hoping to gather enough information to explain the observed distribution of adult crabs in estuaries. The assumption was simple: the physiological tolerances of the larval stages, as reflected in survival rates, will determine the most likely part of the estu- ary in which the larvae will survive to become adults. Salinity stronglyinfluenced survival anddevelopment timefor alllarval stages. Forexample, the first zoea withstood higher salinities much better than lower salinities (Figure 2.1). Eggs hatched at all tested salinity and temperature combinations. However, close to 100% mortality occurred at low (<12.5‰) and high (>31.1‰) salinities for most larval stages. This suggested that those larvae of any stage that were brought into intermediate salinity (and temperature) conditions would have the highest chances of survival. Those hatching and staying in the low- est or highest salinity waters would have the poorest survival probability. The optimum salinity and temperature for each larval stage were the following: Optimal Optimal Larval Stage Salinity (‰) Temperature ( ◦ C) Zoeal Stage 1 27.9 23.5 Zoeal Stage 2 12.4 25.0 Zoeal Stage 3 24.1 26.0 Zoeal Stage 4 No maximum or minimum Megalops No maximum or minimum Zoeal Stage 1 Megalops Zoeal Stage 4 Zoeal Stage 3 20 35 30 5 25 Salinity (parts per thousand) 15 10 15 20 25 30 35 40 Temperature (°C) The shaded area is that in which mortality is approximately 25% or less Zoeal Stage 2 FIGURE 2.1 Salinity and temperature tolerances of Sesarma cinereum larvae. The 25% mortality contours were arbitrarily chosen to show the differ- ences in tolerances among stages. (Modified from Figures 8–12 of Costlow et al. 1960 and larval drawings rendered from Figures 1–5 in Costlow and Bookhout 1960.) © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 16 — #6 16 Ecotoxicology: A Comprehensive Treatment In contrast to the first and third zoea, the second zoea had high tolerances of salinity and temperature. The first and second zoea had best survival at 21–31 ◦ C and 23–28‰. The last zoeal stage showed an increase in temperature tolerance (to 35 ◦ C) and a salinity tolerance down to 3‰. The megalops, the stage reached just before settling to the bottom, showed wide tolerances. The authors concluded that completion of this crab’s life cycle to the adult depended primarily on the fourth zoea and that “the survival and molting to the megalops can only occur in estuarine waters.” Any earlier stage larvae that were transported by water movements outside of the estuarine conditions had very low probabilities of producing megalops. Survival was less dependent on temperature or salinity once the megalops stage was reached. So, the tolerances of the larval stages determined the estuarine region in which the life cycle of this crab will be successfully completed. The weak links in the life cycle were the earlier larval stages. If the fourth zoeal larvae emerged under the appropriate salinity–temperature conditions, the relatively tolerant megalops would be produced, resulting in adults in that particular part of the estuary. particular habitat can sustain. As an example, phosphorus might limit the standing crop of a nuisance blue-green algalspecies ina freshwaterlake and, based on Liebig’slaw, lakemanagers mightfocus on controlling phosphorus input to the lake. Shelford’s law of tolerances (the tolerance of individuals of a species over one or more environmental gradients determines the species’geographical distribution or abundance) (Shelford 1911, 1913) is another such law that is neatly illustrated by the Costlow et al. (1960) study. The ecological niche concept was formulated originally with emphasis on individual tolerances and requirements, and only later was enlarged to include biotic factors. In fact, the niche concept theorizes that the organism occupies a realized niche in the presence of other species that is only a portion of itsfundamental niche asdefined by its organismal tolerancesand requirements.As a classic example, the realized niche of the intertidal barnacle, Chthamalus stellatus, is strongly influenced by desiccation at one extreme and interspecific competition for space with Balanus balanoides at the other (Connell 1961). In ecotoxicology, an autecological study might be conducted of the effects of a pollutant on individuals of a protected or threatened species. An autecological approach might also be used if synecological aspects of a species’ niche occupation were thought to be unimportant or secondary. Such an approach isalso taken reluctantly if there was an absence of sound synecologicalinformation available relative to contamination. Much of ecotoxicology is done within an autecological context and is justified by the indisputable success of classic autecology (Calow and Sibly 1990). As successful as this approach might be for many situations, the autecological approach is often applied in ecotoxicology for situations in which a moment of introspection might reveal that crucial synecological factors are unjustifiably ignored. 3 Reflecting the stage of ecology almost half a century ago, Costlow et al. (1960) described how the physicochemical tolerances of a crab species contributed to its distribution in the coastal systems. Twenty-five years later, when the understanding of contaminant effects became more and more essential, they approached the ecotoxicological consequences of drilling fluid discharge in the same way, implying whether populations would remain viable based on acute assays on the notionally most sensitive stages of a species’ life cycle (Box 2.2). This approach drew on a well-established autecological approach and, in this case, produced a reasonable conclusion. They also adopted, with minimal adaptation, a technological paradigm from mammaliam toxicology—the LC50/LD50 3 Staying with a coastal marine theme, see Harger (1972) for further discussion of the importance of species interactions in determining intertidal species distributions. © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 17 — #7 The Organismal Ecotoxicology Context 17 Box 2.2 Crab Autecotoxicology: Do Chromium Tolerances of Larvae Determine Adult Fate? Twenty-four years after the study described in Box 2.1, these researchers (Bookhout et al. 1984) again described crab larval survival relative to environmental conditions. In keeping with the emerging concern about anthropogenic chemicals, they focused on a pollutant this time. 4 The intent was very similarto that of their first paper—to determine the tolerancesof the larval stages to an environmental quality and, in doing so, to predict the likelihood of life cycle completion in the presence of a specified intensity of that quality. They studied chromium used in drilling fluids to thin mud as it becomes dense. Added as ferrochrome or chrome lignosulfonate, chromium was discharged during and after the drilling. At the time of this study, there was little information on whether its use was harmful to mar- ine species. To explore the potential hazard, Bookhout et al. (1984) exposed decapod larva to different concentrations of hexavalent chromium (as Na 2 CrO 4 ). Results for mud crab, Rhithro- panopeus harrisii, larvae are described here. Figure 2.2 summarizes the cumulative mortality experienced at different larval stages exposed to 0–58 µg/L of sodium chromate. Sodium chro- mate concentrations from 7 to 29 µg/L were considered to be sublethal concentrations because 10% or more of exposed larvae reached the first crab stage. The lethal range was above 29 µg/L. The LC50 for the complete hatch → zoea → first crab life stages was 13.7 µg/L. 5 After integrating this information with knowledge about drilling fluid distributions around points of discharge, the authors concluded that “it is probable that Cr in drilling fluids, whether Cr 3+ or Cr 6+ , is notlikely to reducethe populationof crab larvae and otherplanktonic organisms in the area around oil wells except possibly in the immediate vicinity of the discharge pipes.” Implied from these acute lethality tests on individual larvae was that the persistence of the mud crabs population was not jeopardized, except in the immediate vicinity of a discharge. This reasoning was adapted from that used to define the fundamental niche, that is, application of the law of tolerances to predict the habitat that a species could occupy. However, other aspects of the niche concept, such as interspecies competition, predation, and disease, were ignored. This expedient neglect seems understandable in this particular application but is not always justified. 58 µg/L 46 µ g/L 41 µ g/ L 29 µ g/ L 15 µ g/ L 7 µ g/ L 100 0 25 75 Mud crab larval stage 1 2 Zoea 3 4 Megalops Cumulative mortality (%) 50 1 µ g/ L 0 µ g/ L FIGURE 2.2 Cumulative mortality of mud crab larvae resulting from hexavalent chromium exposure. (Modified from Figure 4 in Bookhout et al. 1984.) 4 The research described in Box 2.1 was published 2 years prior to Rachel Carson’s watershed book, Silent Spring (Carson 1962). As evidenced by the shift in Costlow et al.’s research, Carson’s book mandated that our research efforts become more focused on ecotoxicological questions. 5 Note that this last metric, the LC50, was borrowed from the mammalian toxicology literature to measure toxic effects here but was absent in the temperature–salinity study described in Box 2.1. © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 18 — #8 18 Ecotoxicology: A Comprehensive Treatment approach. The approach taken by these authors and many others dominates ecotoxicology to this day. (See Chapter 9 for details.) It is sufficient in many cases or useful in others for quickly identifying gross problems associated with contamination. Despite its utility in such cases, this autecotoxicolo- gical approach is insufficient in many others and a synecotoxicological context is needed. The key to successful prediction of ecotoxicological consequences is being able to accurately discriminate between situations requiring autecological or synecological vantages, and being able to integrate information from both vantages into reliable predictions of exposure consequences. 2.3 THE VALUE OF ORGANISMAL ECOTOXICOLOGY VANTAGE If the modes of action of toxicants are better understood, we could more accurately predict their effects as pollutants; much knowledge already exists in medical sciences, and could be transferred. (Sprague 1971) Although this discussion may appear hostile to single species toxicity testing efforts, it is not intended to be. Single species tests are exceedingly useful and are presently the major and only reliable means of estimating probable damage from anthropogenic stress. Furthermore, a substantial majority, perhaps everyone in this meeting is certainly aware of the need for community and system level toxicity testing. How then does one account for the difference between awareness and performance? (Cairns 1984) Just as autecology is an essential component of ecology, organismal ecotoxicology— autecotoxicology, if you will—is an essential component of ecotoxicology. Unfortunately, as exemplified in the quote by Cairns above, organismal ecotoxicology tends to overshadow equally crucial investigative vantages. In the remainder of this chapter, the many appropriate and essential applications of organismal ecotoxicology will be highlighted. 2.3.1 TRACTABILITY AND DISCRETENESS Organismal effects are generally the most discrete and tractable of ecotoxicological effects. Few ecotoxicologists would disagree with this statement. After agreeing, a good number of ecotoxico- logists would immediately identify this truism as a sad statement about the field, or point out that this condition may simply be a matter of the historical amounts of effort and thought that have gone into autecotoxicology and synecotoxicology. Here, the follow-up to this statement will simply be to demonstrate the important advantages of drawing on our comprehensive knowledge of organis- mal effects. The ease with which organismal effects or exposure can be assessed will be described first. Next, the relatively effective extrapolation among individuals will be detailed. Organismal information also contributes to our abilities to do reasoned extrapolations of effect to populations and communities, and to predict toxicant transfer within communities. 2.3.2 INFERRING EFFECTS TO OR EXPOSURE OF ORGANISMS WITH SUBORGANISMAL METRICS Sprague, as quoted above, stated correctly that knowledge of suborganismal modes of action greatly improves predictions of toxicant effects to individuals. A current example is endocrine system mod- ulation by xenobiotics. Our newfound understanding of this mode of action for diverse classes of xenobiotics, such as 17β-estradiol from oral contraceptives, 4-nonylphenols, and polychlorinated biphenyls (PCB), improves prediction of similar effects of new chemicals or from new sources of existing xenobiotics (Brown et al. 2001, Hale and La Guardia 2002, Schultz 2003). Knowledge of the © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 19 — #9 The Organismal Ecotoxicology Context 19 suborganismal mode of action also provides a means by which diverse phenomena can be linked by a common thread. As an example, Bard (2000) opined that multixenobiotic resistance in aquatic organ- isms can be explored in the context of the multidrug resistance phenomena. The important insight is that aquatic toxicologists could greatly advance their understanding of multixenobiotic resistance in exposed populations by exploring the extensive literature on the role of P-glycoprotein overex- pression in determining antitumor drug resistance of cancer cells. Transmembrane P-glycoproteins tend to inhibit the transport of xenobiotics into cells, reducing the concentration of xenobiotics at intracellular sites of action. The same is true whether the xenobiotic is a cancer drug or a contamin- ant. Environmental xenobiotic resistance and anticancer drug resistance share a common theme of adaptation by P-glycoprotein overexpression. Suborganismal qualities also provide evidence of contaminant exposure or effects. As a sur- prising example, mesopelagic fish sampled at 300–1500-m depth in the open Atlantic Ocean show evidence of exposure to aryl hydrocarbon receptor antagonists, e.g., polynuclear aromatic hydro- carbons (PAHs) and coplanar-halogenated aromatic hydrocarbons (Stegemen et al. 2001). Elevated cytochrome P450 1A also suggests exposure at considerable distance from coastal sources of aryl hydrocarbon receptor antagonists. 2.3.3 EXTRAPOLATING AMONG INDIVIDUALS:SPECIES,SIZE,SEX, AND OTHER KEY QUALITIES Often predictions require extrapolation from data in hand to some less well-defined situation. 6 Suter (1998) describes two typical examples: extrapolation from LC50 values of Salmoniformes to those for Perciformes, and prediction of carbamate pesticide LD50 based on a test species weight. Ellersieck et al. (2003) provide a computational means for extrapolation of toxicant effects among species. Although challenging and error prone, interpolation among individuals within a species is perhaps the most credible of ecotoxicological interpolations. As an example, Newman (1995) describes interpolation among mosquitofish sexes, genotypes, and sizes relative to survival during acute mercury exposure. 2.3.4 I NFERRING POPULATION EFFECTS FROM ORGANISMAL EFFECTS Sound inference about population effects is possible based on effects on individuals as has already been discussed in our treatment of autecology. The population ecotoxicology section of this book also explores many instances of such reasoning. These instances can be rendered as the following general statements: Population Genetics. (1) Genotypic and phenotypic qualities of individuals sampled from a study population can be used to document population consequences of toxicant exposure. (2) Tox- icants can influence the germ line of a population and, in so doing, influence the phenotypes present in the population. (3) Differences in individual genotypes’ fitnesses in critical life stages can be used to suggest key selection components acted on by toxicants. Population Demographics. (1) Vital rates derived by sampling individuals from populations can be used to document current or to project future conditions of a population. These vital rates include rates of mortality, growth, natality, and migration. (2) Toxicants that lower an individual’s fitness can influence the demographics of an exposed population. Metapopulation Biology. (1) Differences in vital rates of individuals occupying habitat patches that differ in their capacity to maintain the species can produce differences in metapopulation 6 See Suter (1998) for a general discussion of ecotoxicological extrapolation. © 2008 by Taylor & Francis Group, LLC Clements: “3357_c002” — 2007/11/9 — 18:25 — page 20 — #10 20 Ecotoxicology: A Comprehensive Treatment dynamics and persistence. (2) Spatial distributions of individuals relative to the distribution of toxicant in habitat patches will influence metapopulation dynamics and vitality. Epidemiology. (1) Disease prevalence, incidence, and distribution in a population can be defined by measuring disease state in sampled individuals. (2) Causal knowledge derived from the suborganismal or organismal levels reinforce epidemiological inferences. Life History. (1) In the presence of phenotypic plasticity, an organism will experience a shift in its life history traits if stressed. Ideally, such a trade-off in life history traits will optimize the individual’s Darwinian fitness under the environmental conditions it finds itself. (2) Toxicants can change the life history traits of individuals in predictable ways and, in so doing, also influence the population demographics of exposed populations. (3) Phenotypic expression by individuals can involve reaction norms or polyphenisms. It is also true that the abundance of individual-based data tempts intelligent and well-intended ecotoxicologists to make flawed inferences about population consequences from individual-based effects data. As an important example, Newman and Unger (2003) identify the weakest link incon- gruity: the inappropriate prediction of the most sensitive quality relative to population persistence based on the most sensitive life stage of an individual. Often, toxicity testing is done for all life stages of a species and the most sensitive life stage is identified as that stage with the lowest NOEC or LC50. The incorrect extension of such an approach is to falsely infer from this that the most sensitive life stage relative to individual fitness (i.e., survival, growth, or reproduction) is also the most crucial or sensitive relative to population persistence or vitality. Although there are cases in which this approach is adequate, it would be inconsistent with the foundation concepts of popula- tion ecology (Hopkin 1993) to assume that it is always adequate. It is demonstrably false in some cases (e.g., Kammenga et al. 1996, Petersen and Petersen 1988). Another important example is the assumption that individual-derived effect metrics are accurate, albeit conservative, predictors of concentrations that will adversely affect important population qualities. Forbes and Calow (2003) found that this was sometimes the case, but in general, individual-based metrics of adverse effect were not reliable predictors of concentrations adversely impacting populations. More information was needed to accurately infer population effects. 2.3.5 INFERRING COMMUNITY EFFECTS FROM ORGANISMAL EFFECTS If done cautiously, potentially useful inferences about community consequences can be made from the effects of contaminants on individuals. These are detailed in the community ecotoxicology section. A quick review of that section reveals that many community metrics are generated with counts of individuals for the community of interest. Presence of individuals of key or indicator species is also crucial to many of the community-oriented methods. Species-specific sensitivity of individuals to toxicants can be used to develop biotic indices for implying toxicant effect to communities. Colonization or succession theory draws on individual life history qualities for its causal foundation. The autecologically oriented laws of Liebig and Shelford are used to describe the transition in community types along environmental gradients. Rapoport’s rule relating species richness and latitude (or elevation) is also based on individual species’ tolerances. Ambiguously useful applications of individual-based metrics to predictions of community-level consequences are also present in ecotoxicology.Acurrent example is the emerging species sensitivity distribution method. The LC50 (or NOEC) values are collected for all relevant species and used to produce a curve that describes the distribution of toxicant sensitivities of the tested species. The curve is used to compute the LC50 or NOEC concentration associated with only the lowest 5% (or 10%) of species. Only the most sensitive 5% of test species would have an LC50 (or NOEC) at or below that concentration. This HC p is then used to imply a concentration below which all but a small percentage of species in a community will be protected from the adverse effects of the © 2008 by Taylor & Francis Group, LLC [...]... V.E and Calow, P., Contaminant effects on population demographics, In Fundamentals of Ecotoxicology, 2nd ed., Newman, M.C and Unger, M .A (eds.), CRC Press/Lewis Publishers, Boca Raton, FL, 20 03, pp 22 1 22 4 Gleason, H .A. , The individualistic concept of the plant association, Bull Torrey Bot Club, 53, 7 26 , 1 926 Hale, R.C and La Guardia, M.J., Emerging contaminants of concern in coastal and estuarine... accumulation of a contaminant in (and occasionally also on) an individual organism Models and associated concepts applied to toxicant bioaccumulation in individuals establish the foundation on which many community trophic transfer models are built (e.g., Mason et al 1994, Simon and Boudou 20 01) An explicit example of such a model is provided by Laskowski (1991) Consequently, knowledge of contaminant uptake,... G., Acute-to-chronic estimation (ACE v 2. 0) with time–concentration–effect models Use Manual and Software, EPA/600/R-03/107, U.S EPA, Washington, D.C., 20 03 Emmel, T.C., An Introduction to Ecology & Population Biology, W.W Norton & Co., Inc., New York, 1973 © 20 08 by Taylor & Francis Group, LLC Clements: “3357_c0 02 — 20 07/11/9 — 18 :25 — page 21 — #11 Ecotoxicology: A Comprehensive Treatment 22 Forbes,... contaminant uptake, transformation, and elimination by individuals is useful in predicting transfer of contaminants within food webs 2. 4 SUMMARY • The organismal focus in mammalian toxicology and early ecology (i.e., autecology) contributed to an organismal bias in the new science of ecotoxicology • Although resulting in an imbalance in ecotoxicological research, the organismal bias does have positive consequences... E.M., and Guiney, P.D., A critical review of the scientific literature on potential endocrine-mediated effects in fish and wildlife, Ecotoxicol Environ Saf., 49, 17 25 , 20 01 Cairns, J., Jr., Are single species toxicity tests alone adequate for estimating environmental hazard? Environ Monitor Assess., 4, 25 9 27 3, 1984 Calow, P and Sibly, R.M., A physiological basis of population processes: Ecotoxicological... of organization • Careful application of bioaccumulation data enhances our ability to predict trophic transfer of toxicants in food webs REFERENCES Bookhout, C.G., Monroe, R.J., Forward, R.B., Jr and Costlow, J.D., Jr., Effects of hexavalent chromium on development of crabs, Rhithropanopeus harrisii and Callinectes sapidus, Water Air Soil Pollut., 21 , 199 21 6, 1984 Brown, R.P., Greer, R.D., Mihaich,... (1) transfer of new technologies rapidly into ecotoxicology, (2) providing mechanisms for effects seen at higher levels of organization, (3) providing sensitive indicators of exposure or effect, and (4) providing a highly discrete and tractable approach to any ecotoxicological questions • Careful interpretation of organismal data enhances our ability to predict consequences at the population and, sometimes,... FL, 20 03, pp 156–160 Shelford, V.E., Physiological animal geography, J Morphol., 22 , 551–618, 1911 Shelford, V.E., Animal Communities in Temperate America, University of Chicago Press, Chicago, IL, 1913 Simon, O and Boudou, A. , Direct and trophic contamination of herbivorous carp Ctenopharyngodon idella by inorganic mercury and methylmercury, Ecotox Environ Saf., 50, 48–59, 20 01 Sprague, J.B., Measurement... pollutant toxicity to fish—III Sublethal effects and “safe” concentrations, Water Res., 5, 24 5 26 6, 1971 Suter, G.W., Jr., Ecotoxicological effects extrapolation models, In Risk Assessment Logic and Measurement, Newman, M.C and Strojan, C.J (eds.), CRC Press/Lewis Publishers (originally Ann Arbor Press), Boca Raton, FL, 1988, pp 167–185 © 20 08 by Taylor & Francis Group, LLC Clements: “3357_c0 02 — 20 07/11/9... Coastal and Estuarine Risk Assessment, Newman, M.C., Roberts, M.H., Jr., and Hale, R.C (eds.), CRC Press/Lewis Publishers, Boca Raton, FL, 20 02, pp 41– 72 Harger, J.R.E., Competitive coexistence among intertidal invertebrates, Am Sci., 60, 600–607, 19 72 Hopkin, S.P., Ecological implications of “95% protection levels” for metals in soils, OIKOS, 66, 137–141, 1993 Kammenga, J.E., Busschers, M., van Straalen, . ( ◦ C) Zoeal Stage 1 27 .9 23 .5 Zoeal Stage 2 12. 4 25 .0 Zoeal Stage 3 24 .1 26 .0 Zoeal Stage 4 No maximum or minimum Megalops No maximum or minimum Zoeal Stage 1 Megalops Zoeal Stage 4 Zoeal Stage 3 20 35 30 5 25 Salinity. in adults in that particular part of the estuary. particular habitat can sustain. As an example, phosphorus might limit the standing crop of a nuisance blue-green algalspecies ina freshwaterlake. well-established autecological approach and, in this case, produced a reasonable conclusion. They also adopted, with minimal adaptation, a technological paradigm from mammaliam toxicology—the LC50/LD50 3 Staying