Product Citations and Abstracts

In 1991, experimental transplantings of Vallisneria americana (tapegrass, vallisneria, or wildcelery) were initiated at selected sites which lacked grass beds along the north shore of Perdido Bay, located on the Alabama-Florida border. Abatement of organic and color-staining components had been implemented to improve the water quality of effluent discharged by a pulp mill into the headwaters of Elevenmile Creek, a stream entering this low salinity estuary. This study was designed to assess whether previous in situ habitat conditions (e.g., light exclusion, water or sediment toxicity) had prevented natural recruitment of aquatic grasses or if other factors, (e.g. propagule transport) existed which might limit or delay Vallisneria colonization or growth. Different experimental transplanting configurations were employed in order to observe success in establishment of beds and assess our ability to measure plant growth among the varying micro-habitats and substrates. The initial transplanting, in 1991, consisted of two plants each, spaced at 40 cm centers in four 6 x 1 m parallel row-plots. These plants subsequently spread rapidly by runners merging the rows into a continuously expanding grass bed. Second and third trials conducted in 1995, were planted in a cross-shaped configuration, which has emerged as our preferred design. The growth of these transplants indicated Vallisneria grass beds were recruitment limited, rather than constrained by prevailing conditions of water quality/toxicity, light reduction or unsuitable substrate during the study period. Our experience may represent a fundamental method for routine utilization of the responses of submerged aquatic vegetation (SAV) to assess a broad range of questions concerning habitat and water quality of potential sites for habitat restoration.

Davis, W.P., B.S. Hester, R.L. Yoakum and R.G. Domey. 1977. Marine Ecosystem Testing Units: Design for Assessment of Benthic Organism Responses to Low-Level Pollutants. Helgol. Wiss. Meeresunters. 30:673-681. (ERL,GB 321).

"Marine Ecosystem Testing Units" (METU) is an experimental design for integrating responses of communities of marine organisms to low level pollutants under natural conditions of temperature, weather, season, precipitation, sunlight, etc. Ninety-six testing units are arranged in a regimen for pollutant exposure and systematic sampling. Organisms harvested are sorted and enumerated first to major taxa, subsequently to species level. Data are subjected to multi-variate statistical analysis to elucidate relative effects of pollutant, duration of test (harvest), season, and type of organism. Sampling is replicated in time and space. The first year of operation has demonstrated distinct responses to chlorination at levels below chemical detectability.

Davis, W.P., D.P. Middaugh, J.H. Carpenter, G.R. Helz and M.H. Roberts, Jr. 1977. Chemistry and Ecological Effects of Chlorination of Seawater: A Summary of EPA Research Projects. In: Program Review Proceedings of Environmental Effects of Energy Related Activities on Marine/Estuarine Ecosystems. EPA-600/7-77-111. U.S. Environmental Protection Agency, Office of Energy, Minerals and Industry, Washington, DC. Pp. 175-186. (ERL,GB 330).

The use of chlorination to disinfect for bacterial control or control biological fouling is a widespread process unique to the United States. Many countries, including Sweden, Norway, West Germany, Great Britain, and France, have been very conservative in the use of chlorine for these applications. Recent surveys have linked fish mortalities and possibly shellfish bed recoveries to excessive chlorination or reduction of chlorination, respectively (Virginia State Water Control Board, 1974; Virginia Institute of Marine Science, 1975). Studies by Jolley (1973), Helz (in manuscript), and Carpenter (1976, 1977) reveal that both halogenated and nonhalogenated compounds are produced from chlorination of waters rich in organic compounds from natural productivity. In this paper, we summarize the results of ongoing research projects from 1975. In it, we relate preliminary findings to needs for further investigation of the effects of chlorination on marine ecosystems.

Davis, William P. 1979. Impacts of Oil Spill and Clean-Up on the European Coast: Amoco Cadiz. In: Management of Bottom Sediments Containing Toxic Substances: Proceedings of the Fourth U.S.-Japan Experts' Meeting, October 1978, Tokyo, Japan. EPA-600/3-79-102. Spencer A. Peterson and Karen K. Randolph, Editors. U.S. Environmental Protection Agency, Corvallis Environmental Research Laboratory, Corvallis, OR. Pp. 371-394. (ERL,GB 369).

Accidental release of petroleum or other hazardous substances during transport or transfer from ships will continue to be a major focal point of pollution control and abatement efforts. At the time of this writing the Amoco Cadiz wreck on the Brittany coast of France represents the largest oil spill resulting from man's activities. It occurred on one of the world's most productive sea coasts in a nation where both technological and scientific skills abound. Heavy weather contributed to both the causes for the wreck and the subsequent spread of the petroleum to over 200 linear kilometers of biologically rich, high energy coastal habitats. From the moment the French realized the existence of the impending disaster there was a public mobilization of fishermen, farmers, students, scientists, and clean-up equipment; all attempting to take action appropriate to prepare for the coming of the "black tide" or "maree noire." This report attempts to summarize highlights of impacts, ecological effects, and evolving response efforts of interest to persons living or working along the shores of the world's oceans.

Davis, W.P., G.I. Scott, C.D. Getter, M.O. Hayes and E.R. Gundlach. 1980. Methodology for Environmental Assessments of Oil and Hazardous Substance Spills. Helgol. Meeresunters. 33(1):246-256. (ERL,GB 402).

Scientific assessments of the complex environmental consequences of large spills of oil or other hazardous substances has stimulated development of improved strategies for rapid and valid collection and processing of ecological data. Ecological assessment of oil and hazardous material spills has been divided into three distinct phases: (1) first-order response studies - conducted at the time of the initial spill event, which gather data to document acute impacts and assist decision-makers in prioritization of cleanup efforts and protection of ecologically sensitive habitats (2) second-order response studies - conducted two months to one year post-spill, which document any delayed mortality and attempt to identify potential sublethal impacts in sensitive species, and (3) third-order response studies - conducted one to three years post-spill to document chronic impact (both lethal and sublethal) to specific indicator species. First- and second-order response studies of the "Peck Slip#:" oil spill in Puerto Rico illustrate the usefulness of this method.

Davis, William P. and Morris H. Roberts, Jr. 1985. Water Chlorination: Crossroad of Uncertainties and Decisions. In: Water Chlorination: Chemistry, Environmental Impact and Health Effects, Vol. 5. EPA-600/D-85-027. Robert L. Jolley, Editor. Lewis Publishers, Chelsea, MI. Pp. 3-4. (ERL,GB 525). (Avail. from NTIS, Springfield, VA: PB85-156818)

This overview introduces proceedings of the Fifth Water Chlorination Conference convened to review technical reports on all aspects of the use of chlorination, its by-products and environmental effects. Authors raise the following issues: (1) the need to better detect, analyze, and track carcinogenic and mutagenic by-products; (2) the need to be able to moderate if not minimize chlorination to rates that are realistic for high-use waters and to be able to calculate and analyze what realistic means; (3) the need to assess and to anticipate the potential to produce chlorine resistant pathogens; and (4) the need to examine disinfectant alternatives, especially for municipal and industrial treatment, to minimize or prevent formation of toxic by-products in the chlorination-reactors of treatment plants.

Davis, William P. 1986. Role of Rivulus marmoratus in Research on Aquatic Pollutants. J. Am. Killifish Assoc. 19(1):70-80. (ERL,GB 556).

The role of Rivulus marmoratus in research in environmental aquatic research is described. The unique biology of R. marmoratus provides the aquatic toxicologist with the following advantages: 1. Ability to thrive in small volume of water throughout life span; 2. Reproduction through internal self-fertilization; 3. Isogenic clones that allow interclonal and specific intraclonal tissue transplants; 4. Reproductive process in which eggs are laid on a weekly basis throughout the year; 5. Semiamphibious adaptations that contribute to rapid uptake of waterborne and even some airborne compounds.

Davis, William P. 1988. Reproductive and Developmental Responses in the Self-Fertilizing Fish, Rivulus marmoratus, Induced by the Plasticizer, Di-n-Butylphthalate. Environ. Biol. Fishes. 21(2):81-90. (ERL,GB 610). (Avail. from NTIS, Springfield, VA: PB88-219183)

Specialized life history attributes of the cyprinodontiform fish, Rivulus marmoratus, allow continuous life cycle testing to reveal effects of chemicals or environmental stresses upon fertilization, fecundity, egg viability, embryonic development, sex ratios, frequency of growth or skeletal anomalies as well as other biological markers. This study reports responses in fecundity, viability of embryos and skeletal anomalies during and following cessation of exposure of parental fish to 1 and 2 mg/L nominal concentrations of the plasticizer, di-n-butylphthalate (DBP). Skeletal anomalies among offspring were classified as mild, moderate, or severe compared with non-deformed normal offspring. The frequency of skeletal anomalies increased from 4% (all categories combined) in controls, to 10 and 19% of the offspring from adults exposed to 1 and 2 mg/L DBP, respectively. DBP treatment was conducted over a 21 week period, followed by a 9-week post-treatment observation period. During post-treatment frequency of skeletal anomalies decreased to less than 5% in all treatment groups.

Davis, William P., D. Scott Taylor and Bruce J. Turner. 1990. Field Observations of the Ecology and Habits of Mangrove Rivulus (Rivulus marmoratus) in Belize and Florida (Teleostei: Cyprinodontiformes: Rivulidae). EPA/600/J-90/371. Ichthyol. Explor. Freshwaters. 1(2):123-134. (ERL,GB 693). (Avail. from NTIS, Springfield, VA: PB91-163840)

This report provides a synopsis of field studies of Rivulus marmoratus from two population surveys of mangrove islands adjacent to the Belize barrier reef and observations made over fifteen years at several sites in South Florida. This small, cryptically colored killifish is the only known vertebrate selfing hermaphrodite. Florida populations consist nearly exclusively of hermaphrodites (>99%), while the Belize populations contained a significant proportion (10-25%) of males. Our combined observations demonstrate that this species is not "rare" as previously thought, but elusive and highly adapted to microhabitats within mangrove forests. Standard ichthyological collecting techniques are ineffective in this habitat and have previously failed to reveal the strength of the association of R. marmoratus with the mangral ecosystem.

Davis, William P. and Stephen A. Bortone. 1992. Effects of Kraft Mill Effluent (KME) on Sexuality of Fishes: An Environmental Early Warning?. In: Chemically-Induced Alterations in Sexual and Functional Development: The Wildlife/Human Connection. EPA/600/A-93/056. Theo Colborn and Coralie Clement, Editors. Princeton Scientific Publishing Company, Princeton, NJ. Pp. 113-127. (ERL,GB 772). (Avail. from NTIS, Springfield, VA: PB93-168847)

Arrhenoid or masculinized female fish species of the live-bearing family, Poeciliidae, have been observed for over thirteen years in specific southern streams which receive waste effluents from pulping mills. The complex mixture of organic compounds in KME has inhibited specific identification of causal agents(s). However, microbially degraded phytosterols (e.g. sitosterol or stigmastanol) in experimental exposures induce the same intersexual states that characterize affected female poeciliids sampled from KME streams. KME-polluted streams often exhibit a drastic reduction of fish species diversity and degrees of physiological stress, all of which suggests reduced reproduction in surviving forms. A potential ontogenetic or developmental response is demonstrated in American eels captured in one of these streams as well. We examine available information, including laboratory and experimental field exposure, and suggest directions for additional research as well as the need for environmental concern.

Davis, W.P., K.W. Thornton and B. Levinson. 1994. Framework for Assessing Effects of Global Climate Change on Mangrove Ecosystems. EPA/600/J-94/500. Bull. Mar. Sci. 54(3):1045-1058. (ERL,GB 869). (Avail. from NTIS, Springfield, VA: PB95-155198)

Ecological assessment represents a current approach to bridge scientific research and knowledge to the information needs in development of policy and management decisions. Mangrove ecosystems were chosen as a representative community type to examine available knowledge and develop approaches to detection and evaluation of the ecological responses to elements of global climate change. Risk assessments and ecological assessments have some parallel procedures and we briefly compare some common objectives and approaches. The focus of the discussions is in the context of ecological assessment, gathering and evaluating of data most relevant to the south Florida mangroves and associated habitats, and the framework to combine diverse sets of scientific data for the broader or more generalized perspectives and long-term information needs of policy formulation.

Davis, William P. 1997. Evidence for Developmental and Skeletal Responses as Potential Signals of Endocrine-Disrupting Compounds in Fishes. In: Chemically Induced Alterations in Functional Development and Reproduction of Fishes. Rosalind M. Rolland, Michael Gilbertson, and Richard E. Peterson, Editors. SETAC Press, Pensacola, FL. Pp. 61-72. (ERL,GB 992).

Integrated sets of bioindicators and ecological signals would be desirable for rapid detection and assessment of endocrine disruptor syndrome in wild populations of fish and wildlife. Early warning signals would be especially desirable to enable identification before the onset of major reproductive dysfunction or population consequences. Comparison of various research reports in the literature reveals that many of the same compounds that induce developmental, morphological, and/or skeletal anomalies are later identified as endocrine disruptors. Kepone, mirex, polychlorinated biphenyls (PCBs), trifluralin, dibutylphthalate (DBP), kraft-mill effluents (KMEs), and others induce skeletal, developmental, and/or sex-linked morphological abnormalities that become manifest biomarkers among surviving mature fishes. This report examines several specific cases of skeletal and external morphological responses and suggests their relevance as markers signaling the probability of disruption of an endocrine modulated function.

Davis, William P. 1991. Rivers of Florida (Book Review). BioScience. 41(9):643-644. (ERL,GB R236).

'The Rivers of Florida,' an illustrated reference book, is reviewed. The book resulted from a 1989 workshop in Tallahassee sponsored by Florida State University and several state water management agencies. It is a compilation of the existing knowledge of the 'main' drainage systems of Florida and attempts to direct attention to increase understanding and prevent further loss of resources.

Davis, William P. 1998. Fishes of the Continental Waters of Belize (Book Review). Copeia. 1998(2):528. (ERL,GB R609).

Until now, anyone seeking a freshwater fish identification guide for Central America would be forced to create one's own with an assemblage of reprints. In Belize we have been using "unofficial" photocopies of draft manuscript sections of this reference for several years. Therefore, I am delighted to see the publication of this volume. It is hoped that this book establishes a trend to produce more regional guides for other areas and nations of Central and South America to instill awareness in the environmental public of these incredibly rich fish faunas. The authors have wisely chosen the book's coverage to include fishes which inhabit rivers, lagoons, estuaries and mangrove forests, as well as the inland freshwater streams. The broad aquatic coverage makes the book a useful companion for identifying fishes from habitats on the numerous mangrove cays that comprise the Belize coastal system. The authors discuss in their preface the occurrences of various marine fishes that enter coastal water bodies and anticipate that there are and will be discrepancies among species listed in these habitats. The introduction includes a synopsis of Belize geography, coupled with the Pliocene geological configuration which explains current characteristic region specific habitats of the nation. The introduction also integrates a synopsis of the zoogeography of fishes of Central America and the net result is a lucid summary of interest to all students of ichthyology. The first three maps, indicating the location of Belize, geographic names, names of rivers, streams and lagoons, and Pliocene configuration influence on present river drainage patterns, present an effective introduction and reference foundation for the remainder of the volume. Unfortunately, the editors of the publication missed a distracting error labeling the southern border as "Honduras" whereas Guatemala's Atlantic coast should instead have been identified. The book is enriched withover 275 drawings by the senior author which, as explained in the preface, are intended to demonstrate the specific characteristics or key characters of each species. These figures are integrated to rapidly and painlessly guide the reader to one of the appropriate thirty bony fish families where additional keys and descriptions distinguish species. Species are identified by scientific and common names, as well as references to appropriate figures and one of the 68 maps indicating collection sites known to the authors. A short glossary is provided to assist the utility of the keys. The literature cited provides references to a broad range of sources on biology of fishes through 1993. The style of writing and descriptions are equally useful and effective for both novice and trained ichthyological seekers. The book is bound with a North American climate in mind, and in future editions, the publishers should consider strategies for making it suitable for sustained tropical exposure. I took my first copy of the book to Belize and we rapidly identified peociliids from mangrove cays during a recent survey. Our Belizean colleagues were elated to acquire copies. I recommend this as a long needed and awaited edition for students of Central American fish fauna.

Davis, William P. and William F. McIlhenny. 1978. Marine Workshop Summary. In: Water Chlorination: Environmental Impact and Health Effects, Vol. 2. Robert L. Jolley, Hend Gorchev, and Hamilton D. Heyward, Jr., Editors. Ann Arbor Science Publishers, Ann Arbor, MI. Pp. 859-862. (ERL,GB X056).

The invited papers emphasize some of the special aspects of chlorination of marine waters, the rapid release of bromine from naturally occurring bromide salts and subsequent chemical events unique to marine waters and the resulting challenge to chemical analysis. This subject was amplified by reports investigating halogenated by-products in power plant cooling waters, and current results from investigations designed to assess and identify halogenated organics resulting from chlorination of natural sea waters.

Davis, William P. and Douglas P. Middaugh. 1978. Revised Review of the Impact of Chlorination Processes upon Marine Ecosystems: Update 1977. In: Water Chlorination: Environmental Impact and Health Effects, Vol. 1. Robert L. Jolley, Editor. Ann Arbor Science Publishers, Ann Arbor, MI. Pp. 283-310. (ERL,GB X057).

For over 175 years chlorine gas has been used in industrial, biocidal and disinfection applications. The chemistry of chlorine in fresh water is relatively well known, but long-range effects on the organisms and the ecological communities of marine waters have barely been studied. Until recently, the so-called 'chlorine demand' of treated or receiving waters has been considered a desirable feature which assured degradation of actively oxidizing states of chlorine to a nontoxic state. With continuing and increased use of chlorine as an antifouling biocide in powerplants, and as a disinfectant of municipal wastes, concern has arisen that resulting by-products, such as induced halogenated hydrocarbons, could potentially reach environmentally harmful levels. For example, in the state of Maryland the quantity of chlorine used, which subsequently reaches the Chesapeake Bay, would have sterilized that body of water were not chemical/biological degradation processes in effect. But, what are the limits of natural degradation systems? What, for one example, are the known environmental costs of our present rates of chlorine applications on renewable fishery resources? What kind and at what rate are persistent halogenated compounds being produced? Where do these go in natural systems? From partial or complete answers to these questions will come meaningful environmental management criteria. This paper presents a theoretical degradation model of chlorine added to marine waters. Additionally it summarizes literature reporting laboratory or ecological effects of chlorinations. It is revised to attempt incorporation of pertinent literature through 1977.

Davis, William P. and D.P. Middaugh. 1977. Impact of Chlorination Processes on Marine Ecosystems. In: Estuarine Pollution Control and Assessment: Proceedings of a Conference, Vol. 2. EPA-440/1-77-007. U.S. Environmental Protection Agency, Washington, DC. Pp. 415-423. (ERL,GB X104).

The use of chlorine as a disinfectant and antifouling agent is reviewed. Chemical reactions of chlorine in aquatic environments are discussed, with particular emphasis on the formation of halogenated organic constituents in freshwater and marine systems. Studies of the effect of chlorinated sewage effluents and cooling water from generating stations on marine organisms and ecosystems are summarized.

Davis, William P. and Douglas P. Middaugh. 1976. Review of the Impact of Chlorination Processes upon Marine Ecosystems. In: Environmental Impact of Water Chlorination: Proceedings of the Conference on the Environmental Impact of Water Chlorination, Oak Ridge National Laboratory, Oak Ridge, Tennessee, October 22-24, 1975. Robert L. Jolley, Editor. Oak Ridge National Laboratory, Oak Ridge, TN. Pp. 299-325. (ERL,GB X155). (Avail. from NTIS, Springfield, VA: CONF-751096)

For over 175 years chlorine gas has been used in industrial, biocidal and disinfection applications. The chemistry of chlorine in freshwater is relatively well known, but long-range effects on the organisms and the ecological communities of marine waters has barely been studied. Until recently, the so-called 'chlorine demand' of treated or receiving waters has been considered as desirable feature which assured degradation of actively oxidizing states of chlorine to a non-toxic state. With continuing and increased use of chlorine as an antifouling biocide in powerplants, and as a disinfectant of municipal wastes, concern has arisen that resulting byproducts, such as induced halogenated hydrocarbons, could potentially reach environmentally harmful levels. For example in the State of Maryland the quantity of chlorine used, which subsequently reaches the Chesapeake Bay, would have sterilized that body of water were not chemical/biological degradation processes in effect. But, what are the limits of natural degradation systems? What, for one example, are the known environmental costs of our present rates of chlorine applications on renewable fishery resources? What kind and at what rate are persistent halogenated compounds being produced? Where do these go in natural systems? From partial or complete answers to these questions will come meaningful environmental management criteria. This paper presents a theoretical degradation model of chlorine added to marine waters. Additionally it summarizes literature reporting laboratory or ecological effects of chlorine.

Davis, William P., John E. Randall and Donal O. French. 1977. Systematics, Biology and Zoogeography of Ptereleotris heteropterus (Pisces: Gobiidae). In: Proceedings: Third International Coral Reef Symposium, Vol. 1. Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL. 1:261-265. (ERL,GB X211).

The gobiid fish, Ptereleotris heteropterus is redescribed based upon additional material. Range distribution of Ptereleotris heteropterus previously known only from Borneo is extended throughout the Indo-Pacific region: Reunion, Maldives, Solomons, Guam, Hawaii, Samoa, Fanning, Marquesas and Society Islands. Notes on the habitat and certain behavior patterns indicate its life ways in habitats of eroded coral reef substrates.

Davis, W.P. and R.S. Birdsong. 1973. Coral Reef Fishes Which Forage in the Water Column. A Review of Morphology, Behavior, Ecology and Evolutionary Implications. Helgol. Wiss. Meeresunters. 24(3):292-306. (ERL,GB X324).

This paper is a synthesis of the two authors' own observations, together with observations from published works dealing with a common and important resource exploitation in the aquatic environment: foraging in the water column. It brings together the data from food studies, morphology and community structure on coral reefs and demonstrates a way of making a living - a 'mode of existence', 'resource exploitation' or whatever one wishes to call it; this situation should be recognized by the undersea investigator, and is clearly to be seen by even the novice diver. The relevance of this means of existence in the community is emphasized by the number of fish families dwelling about coral reefs, or in analogous environments, from which have evolved species members exhibiting the set of characteristics and specializations of behavior and morphology typifying water-column foragers. This mode of living has been generally accepted, perhaps too glibly, so that details of its significance have not previously been pursued in sufficient depth.

Davis, W.P., D.E. Hoss, G.I. Scott and P.F. Sheridan. 1984. Fisheries Resource Impacts from Spills of Oil or Hazardous Substances. In: Restoration of Habitats Impacted by Oil Spills. John Cairns, Jr. and Arthur L. Buikema, Jr., Editors. Butterworth Publishers, Boston, MA. Pp. 157-172. (ERL,GB X376).

Fisheries is the traditional designation for exploitable aquatic organisms (plants and animals) in fresh, estuarine and marine waters. Exploitation connotes utilization or economic value, but, in terms of species, fisheries also includes organisms of aesthetic or genetic preservation value (e.g., endangered species) as well as commercial species. Major elements of life histories, food webs, habitats and migration routes comprise fisheries ecology. These elements are also involved in fisheries resource assessment. Fisheries resource assessment methods typically apply representative parameters to models in order to estimate population structure, fecundity, and calculated levels of sustainable catch, harvest, renewal, or production. All habitats discussed in this book, with perhaps the exception of the tundra, are specific fisheries resources in considering contamination effects of spillages. Oil pollution is a potential impact to fisheries resources for three reasons; (1) a direct (lethal or sublethal) effect to fisheries stocks may occur, (2) oil may render the fisheries products unacceptable to the consumer, and (3) fishing operations may be directly affected by the presence of oil. These reasons may be extended to other hazardous or toxic materials. Examples have been documented for each of these reasons. High mortalities occurred amongst oysters in the estuaries of Brittany, France during the 1978 Amoco Cadiz spill. Oysters and other fisheries resources elsewhere have acquired hydrocarbon taint from spills or seepages. The vast areas covered by oil released from the Ixtoc I well blow-out near Campeche, Gulf of Mexico in 1979 caused shrimpers and other fishermen to change location of their operations.

Davis, William P. and James A. Fava. 1983. Interaction of Aquatic Ecosystem Components with Chlorination: An Overview. In: Water Chlorination: Environmental Impact and Health Effects, Vol. 4. Robert L. Jolley et al., Editor. Ann Arbor Science Publishers, Ann Arbor, MI. Pp. 791-796. (ERL,GB X377).

The use of tools such as disinfectants, oxidants, or biocides to protect public health remains highly debatable relative to environmental issues, research, and quality of life. Increased public awareness is evidenced by regional conferences (e.g., 'Chlorination: Bane or Benefit'), which address specific stressed systems such as the Chesapeake Bay. That use of chlorination provides benefits to man is not an issue-the questions are how much to use and what risks and costs are involved. Overzealous chlorination can cause ecological damage and disfunction of ecology; control methods such as criteria and regulations are debatable and under challenge. Over the past six or more years, the basic questions about chlorination have not significantly changed; however, the details and data available to us have increased immensely. Two ongoing activities served as the motivating force behind both formal and informal discussions in the session 'Interaction of Aquatic Ecosystem Components with Chlorination' at the Fourth Water Chlorination Conference. These were (1) the recognition that in some areas of the United States, serious consideration has been given to banning all chlorination for disinfection because of the potential for ecological damage; and (2) many scientists, regulators, or environmental managers feel that sufficient research has now been conducted to justify eliminating further funding of chlorination effects studies. This paper examines the salient aspects of the topics discussed during the conference with the hope of addressing the question: Where do we go from here?

Davis, William P. 1982. Major Uses of Chlorination (An Ecologist's Perspective). In: Chlorine - Bane or Benefit?: Proceedings of a Conference on the Uses of Chlorine in Estuaries, May 27-28, 1981, Mary Washington College, Fredericksburg, Virginia. Chesapeake Bay Foundation, Annapolis, MD. Pp. 8-14. (ERL,GB X428).

The goal of municipal water treatment is to prevent spread of human pathogens, as well as to maintain quality of natural receiving waters. With the exception of treatment systems using hyperchlorination, chlorination application in municipal waste treatment occurs after process steps to digest organic wastes, themselves depending on bacterial action. Chlorination is used, therefore, as a prophylaxis to treat discharge waters. Chlorination in municipal treatment is applied by using 'chlorine demand', setting application rates to produce a residual oxidant level. Overchlorination, therefore, can easily occur in response to high supply of wastewaters during floods, rain, plant malfunction/breakdowns, or just over-zealous controllers. In waste treatment plants, the crucial chlorination control point is the operator, and the many pressures affecting this person.

Davis, W.P. and R. Fricke. 1990. Callionymidae. In: Check-list of the Fishes of the Eastern Tropical Atlantic (Clofeta): Vol. II. J.C. Quero et al., Editor. JNICT, Lisbon, Portugal. Pp. 921-924. (ERL,GB X741).

This book chapter describes habitat and distribution of Callionymidae in the Eastern Tropical Atlantic as recorded in scientific literature.

Davis, William P., D. Scott Taylor and Bruce J. Turner. 1995. Does the Autecology of the Mangrove Rivulus Fish (Rivulus marmoratus) Reflect a Paradigm for Mangrove Ecosystem Sensitivity?. EPA/600/J-95/458. Bull. Mar. Sci. 57(1):208-214. (ERL,GB X810).

The killifish Rivulus marmoratus, mangrove rivulus, represents the one of the two potentially truly 'mangrove dependent' fish species in western Atlantic mangrove ecosystems. The distribution of this species closely parallels the range of red mangroves. These plants and fish exhibit parallel ecological and physiological tolerances to the wide ranges of tropical temperatures and salinities, as well as substrate and hydrological conditions of mangrove habitats. The mangrove rivulus, R. marmoratus is, as well, the only truly marine representative of a speciose genus of otherwise freshwater fish species. Many of the biological specializations of this species characterize the specific challenges to survival in mangrove forest conditions. As recent studies report, this fish species, once considered 'rare,' has been shown to be very abundant in specific substrate microhabitats of the mangal. Among the unique specializations of this fish are amphibious emersion from water, survival in moist detrital substrate during periods of low water or drought, and reproduction through internal self-fertilization producing homozygous clones. The autecology of this species provides fascinating insights and generates a wealth of questions regarding evolution of specific adaptations for distribution, dispersal, colonization, population genetics and the interrelationships between adaptation and specialization. The Indian River Lagoon (IRL) represents both the site of rediscovery of the fish as well as the northern frontier of the species distribution range, habitat, and ecosystem. This suggests close interrelationships and parallels in the parameters to which the species has adapted, perhaps representing a commonage, of ecological association. These aspects are discussed with respect to details and insight needed to develop strategies for the management of unique communities and ecosystems, especially along their natural distributional borders. The topic raises such questions as: Are some 'exotic species' actually examples of newly arrived colonizers, representing dynamic biotic responses to climate change and/or anthropogenic habitat modification?

The fishes of the Pelican Cays, Belize, were sampled using a combination of small rotenone stations and visual censuses. Records from the Pelican Cays are compared with lists of species known from the adjacent Rhomboidal Cays, the inshore coastline of Belize, the outer margin of the Belize Barrier Reef and the off-shore banks. At least three species are known only from the Pelican Cays (and nearby Rhomboidal and Wee-Wee Cays).

Fisher, William S., Deborah L. Santavy, William P. Davis and Lee A. Courtney. 2006. Regional Monitoring of Coral Condition in the Florida Keys. In: USDA Forest Service Proceedings RMRS-P-42CD. 2006. Proceedings of the Monitoring Science and Technology Symposium: Unifying Knowledge for Sustainability in the Western Hemisphere, held 20-24 September 2004, Denver, CO. Aguirre-Bravo, Celedonio, et al., Editor. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO. Pp. 304-311. (ERL,GB 1219).

Tropical reef corals have experienced unprecedented levels of bleaching and disease during the last three decades. Declining health has been attributed to several stressors, including exposures to elevated water temperature, increased solar radiation, and degraded water quality. Consequences of coral bleaching and disease vary; some recover, while others lose tissue, die and succumb to algal overgrowth. In 2000, a regional monitoring project documented disease prevalence and bleaching across 41 km2 of coral reefs in the Florida Keys. Thirty sites were randomly selected from a spatially-balanced grid. A radial belt transect (113 m2) was surveyed at each site and 100-300 colonies were encountered in each transect. The coral species and health status were recorded for each colony. No site had greater than 13% disease prevalence and approximately 80% of the reef area had <5% disease prevalence. The survey will be repeated in 2005, but with additional measurements to estimate colony size, percent living tissue, and living surface area. These added endpoints are expected to provide information on the consequences of bleaching, disease, and other stressors on coral communities. Data will be compiled to characterize community composition, abundance, age class structure, and survival of different species across the Florida Keys reef tract. During a pilot study in 2003, living coral tissue on large colonies of elkhorn coral Acropora palmata was considerably less than on small colonies, possibly indicating a major mortality event (e.g., hurricane or bleaching) that occurred prior to recruitment of the smaller colonies.

Courtney, Lee A., William P. Davis and William S. Fisher. 2007. Estimating 3-Dimensional Surface Area of Field Corals. J. Exp. Mar. Biol. Ecol. 351(1-2):234-242. (ERL,GB 1257).

In situ measurement of scleractinian coral size and structural complexity in has been elusive. Three-dimensional (3D) colony surface area has been measured in the laboratory but the techniques are inappropriate for underwater field surveys. Recent field studies have demonstrated the potential of 3D colony surface area measurements for evaluating coral condition. This potential would be enhanced by an ability to accurately estimate 3D coral surface area from rapid underwater field measurements. Here we apply non-destructive photographic methods to document size and structure of corals in the field. Multiple images of a single colony were used to generate a scaled 3D computer reconstruction of colony morphology that can be accurately measured for colony dimensions and 3D surface area. Methods were applied to 23 colonies of two stony coral species, Diploria clivosa and D. strigosa, photographed in situ at the Florida Keys and Dry Tortugas. Accuracy of the technique was examined by comparison with a laser-scanned laboratory colony, and precision was documented through repetitive model construction. Surface areas and volumes calculated from digitally reconstructed corals were compared to colony dimensions and to size classes assigned in the field. These comparisons provided a means to estimate coral surface area and volume from simple field measurements and demonstrated that surface area of Diploria colonies closely approximated hemispheric surface area. Further application of this technique to additional coral taxa will advance methodology for assessment of coral and coral reef condition as well as for understanding surface-related physiological processes of coral.

Block, Ronald M., George R. Helz and William P. Davis. 1977. Fate and Effects of Chlorine in Coastal Waters: Summary and Recommendations. Chesapeake Sci. 18(1):97-101. (ERL,GB 344).

This workshop was a logical extension of the conference "Environmental Impact of Water Chlorination" sponsored by EPA/ERDA and Oak Ridge National Laboratory 22-24 October, 1975. At Oak Ridge, engineers, environmentalists, biological and chemical researchers, and public health specialists came together and reviewed all aspects of chlorination of water. Among presentations at Oak Ridge were clear signals that chlorination of marine waters is unique and not analogous to chlorination of fresh waters. In effect this was reinforcement of research strategies of several federal, institutional and industrial groups. This workshop was therefore a chance for researchers to air, examine and criticize research activity underway, not to report conclusions per se. It constituted a forum where researchers could compare techniques, hypotheses, observations and make plans for continued pursuit of elusive insights into the dynamics of powerful oxidants such as chlorine in complex environments, such as living marine ecosystems.

Abel, Daniel C., Christopher C. Koenig and William P. Davis. 1987. Emersion in the Mangrove Forest Fish Rivulus marmoratus: A Unique Response to Hydrogen Sulfide. EPA/600/J-87/061. Environ. Biol. Fishes. 18(1):67-72. (ERL,GB 554). (Avail. from NTIS, Springfield, VA: PB87-212932)

The mangrove forest fish Rivulus marmoratus (Cyprinodontidae) has frequently been observed out of water, a phenomenon generally attributed to habitat drying. We tested the hypothesis that hydrogen sulfide, a substance characteristically found in their environment, can serve as a stimulus for emersion. In the field we found R. marmoratus in water with low to moderate levels (<250 ppb) of H2S. In the laboratory, R. marmoratus leaped from water contaminated with H2S at ecologically relevant concentrations (median response at 123 ppb). Aquatic hypoxia did not induce emersion, but prey capture did. Oxygen consumption by both juveniles and adults decreased significantly in air (27 and 25%, respectively). Our results suggest that avoidance of H2S and the ability to survive terrestrial conditions enable this species to permanently occupy an area of the forest unavailable to other fishes. Furthermore, because a variety of stimuli lead to emersion in R. marmoratus, terrestriality in this species is likely a generalized response to environmental stress as well as a means of exploiting terrestrial resources.

Ritchie, Scott A. and William P. Davis. 1986. Evidence for Embryonic Diapause in Rivulus marmoratus: Laboratory and Field Observations. J. Am. Killifish Assoc. 19(1):103-108. (ERL,GB 567).

Among North American killifish species, diapause, or arrested embryonic development, has been infrequently noted. Harrington (1959) describes delayed hatching in eggs of Fundulus confluentus and recovery of larvae from marsh sods inundated in the laboratory with tap water. These sods were sampled from natural vegetated swales which become pools during rainy periods. Sod samples yielded hatched F. confluentus 15-30 minutes after immersion in the laboratory following 2-3 months of no inundation in the field. Aware of this research, the senior author has been carrying out time-series observations on sites used by the Collier County (Florida) Mosquito Control District to monitor larval mosquito hatches. The uniform size of the fry collected from the test site, and the brevity of immersion (November 1984-April 1985) before onset of rainy season, mitigate against the survival of previously hatched fish, and argue in favor of embryonic diapause.

Bortone, Stephen A., William P. Davis and Charles M. Bundrick. 1989. Morphological and Behavioral Characters in Mosquitofish as Potential Bioindication of Exposure to Kraft Mill Effluent. EPA/600/J-89/537. Bull. Environ. Contam. Toxicol. 43(3):370-377. (ERL,GB 659). (Avail. from NTIS, Springfield, VA: PB91-199893)

Although the specific chemicals or factors actually responsible for induction of arrhenoidy among mosquitofish have not yet been identified, it is known that a wide variety of potential compounds occur as by-products from the processing of wood pulp (Keith 1976). Purpose of study was to investigate the morphological and behavioral responses of mosquitofish environmentally exposed to kraft mill effluent (KME) and to evaluate the potential of these responses as bioassay endpoints. A method to quantify the morphological or behavioral responses of mosquitofish should provide an in situ bioindicator to assess impact of KME discharge on receiving water biota.

Turner, Bruce J., John F. Elder, Jr., Thomas F. Laughlin, William P. Davis and D. Scott Taylor. 1992. Extreme Clonal Diversity and Divergence in Populations of a Selfing Hermaphroditic Fish. EPA/600/J-93/067. Proc. Natl. Acad. Sci. U.S.A. 89(22):10643-10647. (ERL,GB 814). (Avail. from NTIS, Springfield, VA: PB93-169019)

Recombination is unknown in natural populations of Rivulus marmoratus, a selfing hermaphrodite, and genetic variation is likely due to mutation alone. DNA fingerprinting with an array of microsatellite [e.g., (CT)9] and minisatellite (e.g., the 33.15 core sequence) probes reveals very high clonal diversity within samples of seven Floridian populations; five contain about as many clones as there are individuals. There are 42 clones among 58 individuals surveyed (mean = 1.4 individuals/clone), a level of genetic diversity unprecedented among clonal animals. Moreover, all of the probes recognize the same clones even though, at high hybridization stringencies, there is little overlap in the fingerprint patterns they generate. This suggests that most sympatric clones differ by multiple and independent mutational steps. In one population studied in detail, the average number of mutational steps separating two clones is estimated at about 9-10 and may be substantially higher. The mutational discontinuities among sympatric clones make it unlikely that they evolved by the accumulation of neutral mutations in populations that are otherwise genetically uniform. The data argue that the mixing of unrelated individuals from different local populations occurs to an extent previously unappreciated and/or that divergence of clones is mediated by natural selection. If confirmed, the latter would be a serious challenge to current ideas on the predominant role of recombination in promoting the evolution of biological novelty.

Heath, Alan G., Bruce J. Turner and William P. Davis. 1993. Temperature Preferences and Tolerances of Three Fish Species Inhabiting Hyperthermal Ponds on Mangrove Islands. EPA/600/J-93/388. Hydrobiologia. 259:47-55. (ERL,GB 829). (Avail. from NTIS, Springfield, VA: PB93-236263)

The fish species Cyprinidon artifrons, Floridichthys carpio, and Gambusia yucatana inhabit shallow mangrove ponds off the coast of Belize. Portions of these ponds experience a diurnal temperature change from 26°C at night to 40°C and above during midday. Repeated field observations indicate Cyprinidon prefer the warmer (and much larger) portions of the ponds whereas the other two species stay in the cooler areas. The hypothesis that temperature is serving as a cue for partitioning within the ponds was supported by laboratory thermal gradient tests in which Cyprinidon clearly preferred temperatures higher than the other two species. The critical thermal maximum (CTM) was determined for the three species using members that had been acclimated to either a daily cycling temperature similar to that for the ponds, or to the mean of the 24-hour cycle (30°C). Cyprinidon, acclimated to the cycling temperature, had a CTM of 45.5°C, which apparently sets a new record for fish CTM. Acclimation to a constant 30°C lowered the CTM to 43.7°C for those acclimated to 30°C. All three species appear to have the ability to tolerate the high temperatures throughout the ponds but only Cyprinidon utilizes the whole pond during the day. This may help to explain the large populations of Cyprinodon found in these mangrove ponds compared to the other species.

Bortone, Stephen A. and William P. Davis. 1994. Fish Intersexuality as Indicator of Environmental Stress. EPA/600/J-94/283. BioScience. 44(3):165-172. (ERL,GB 876). (Avail. from NTIS, Springfield, VA: PB94-191095)

Intersexuality in the form of masculinization has been observed among poeciliid fishes (i.e., mosquitofish, least killifish, and sailfin molly) from streams receiving paper mill effluent (i.e., kraft mill effluent). The degree of masculinization is related to the relative concentration and duration of exposure to KME. Compounds associated with KME apparently act as endocrine disruptors to the normal expression of secondary sex characters. Monitoring intersexuality in these fishes may serve as a useful sentinel to detect endocrine disruptors in the environment.

Carpenter, James H., Roger M. Bean, Walter J. Blogoslawski, William P. Davis and Robert L. Jolley. 1979. Chlorination Products. In: Proceedings of a Workshop on Scientific Problems Relating to Ocean Pollution, Estes Park, CO., July 10-14, 1978. U.S. National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Boulder, CO. Pp. 23-34. (ERL,GB X030).

These studies, together with investigations of fresh water and marine waters describe a broad spectrum of effects of chlorination on biota. However, only recently have investigators attempted to distinguish between the effects of oxidative compounds and the effects of other chlorination by-products. A substantially increased research effort comprehensively integrating biological and chemical studies is needed to evaluate recent findings.

Orlando, Edward F., William P. Davis and Louis J. Guillette, Jr. 2002. Aromatase Activity in the Ovary and Brain of the Eastern Mosquitofish (Gambusia holbrooki) Exposed to Paper Mill Effluent. EPA/600/J-02/342. Environ. Health Perspect. 110(Suppl 3):429-433. (ERL,GB X1020).

Studies have shown that female mosquitofish living downstream of a paper mill located on the Fenholloway River, Florida, have masculinized secondary sex characteristics, including altered anal fin development and reproductive behavior. Masculinization can be caused by exposure to androgens in the water or from an alteration in aromatase activity in the fish. We hypothesized that aromatase activity would be inhibited by a component(s) of the paper mill effluent. Aromatase inhibition could masculinize the hormonal profile and, subsequently, secondary sex characteristics of the exposed females. Therefore, we predicted that ovarian and brain aromatase activity would be lower in the female mosquitofish from the Fenholloway River compared with the reference site, the Econfina River. Adult females were collected and standard length, body mass, anal fin length, and segment number were measured. Ovarian and brain aromatase activity were determined using a tritiated water assay. Fenholloway females had masculinized anal fin development as indicated by an increase in the number of segments in the longest anal fin ray (p < 0.0001), yet the length of the ray did not differ between sites (p ± 0.95). Fenholloway females exhibited higher ovarian (p = 0.0039) and brain (p = 0.0003) aromatase activity compared with reference site fish. These data do not support aromatase inhibition as the mechanism for masculinization, suggesting that the masculinization of the Fenholloway female mosquitofish is due to androgenic contaminants. Future studies should examine the relationship between aromatase enzyme activity and exposure to environmental androgens.

Orlando, Edward F., Danielle E. Bass, Lisa M. Caltabiano, William P. Davis, L. Earl Gray Jr and Louis J. Guillette Jr. 2007. Altered Development and Reproduction in Mosquitofish Exposed to Pulp and Paper Mill Effluent in the Fenholloway River, Florida USA. Aquat. Toxicol. 84(4):399-405. (ERL,GB X1100).

Female mosquitofish exposed to pulp and paper mill effluent (PME) in the Fenholloway River, Florida, USA have masculinized secondary sex characteristics and altered aromatase enzyme activity. We and others have shown that the Fenholloway River PME contains androgenic and progestogenic substance(s). The present study was designed to test the hypothesis that the development and reproductive health of PME-exposed Fenholloway River mosquitofish are altered compared to mosquitofish living in Econfina River, which is the reference site. Fish were collected on a single day from both sites in June and August 1999 and January and June 2000. We compared standard length, anal fin length and segment number; body, liver, and gonad mass; and number of eggs and embryos from Fenholloway and Econfina River mosquitofish. The data were analyzed collectively for generalized site effect, for site effects during reproductive and nonreproductive seasons, and for repeatability of site effects between years. Mosquitofish exposed to PME in the Fenholloway River were generally smaller in length and mass, anal fin segment number was greater, and the number of embryos, but not oocytes, was significantly decreased compared to the reference site fish. Anal fin length and segment number and liver and testis masses were generally greater in Fenholloway compared to the Econfina River males. The importance of this study is that we have documented masculinized development and decreased embryo production in PME-exposed mosquitofish and that these site effects are generally consistent across seasons and between year

Brungs, William A., William P. Davis, James A. Fava, D. Heyward Hamilton, Jr., Jack S. Mattice, Richard J. Ruane and Robert B. Samworth. 1980. Reaction Products and Ecological Effects of Aqueous Chlorination. In: Water Chlorination: Environmental Impact and Health Effects, Vol. 3. Robert L. Jolley, William A. Brungs, and Robert B. Cumming, Editors. Ann Arbor Science Publishers, Ann Arbor, MI. Pp. 1127-1139. (ERL,GB X164).

As demonstrated by the programs of the three conferences on water chlorination, studies of environmental impact have changed significantly during the past several years. Whereas much of the earliest program related to continuous discharges of chlorinated effluent from sewage treatment plants, a preponderance of the studies reported at the 1979 conference involved intermittent or short-term exposures that simulate chlorinated effluents from power generating stations, which require chlorination to control biofouling organisms. The trend has shifted from general or review papers that were prepared to educate many of us on the basics of chlorine toxicity to very (or, even ultra-)specific papers dealing with very precise exposures or effects. Another trend relating to the aqueous chemistry of chlorine has also developed. Initially, many of us may have been content to view chlorine in surface waters as total residual chlorine on the assumption that observed effects could be explained by a simplistic conglomeration of toxic chlorine products that happen to be detected by a standard analytical procedure. However, studies reported at this conference demonstrate differences in toxicity between monochloramines and dichloramines. In the area of chlorine chemistry in estuarine and marine waters, there may ultimately be a need for even finer chemical differentiation. Finally, there has been a trend from a preponderence of data collection in freswater systems to a majority of testing in various saltwater systems. Hopefully, these trends are indicative of progressive evolution that reflects a solution of some problems and a willingness to accept more difficult challenges, including attempts to use the available data to develop more scientifically sound regulatory programs. The following summary of the oral and poster session papers on the aquatic ecological impacts of water chlorination is organized under the headings of 1. Toxicity of continuously chlorinated waters; 2. Chlorine chemistry and toxicity of chlorinated cooling waters; 3. Formation and implications of halogenated compounds in surface waters; 4. Toxicological methods development for aquatic species; 5. Hazard evaluation and use of toxicological data in criteria and standards development for the protection of aquatic life.

Gundlach, Erich R., Jacqueline Michel, Geoffrey I. Scott, Miles O. Hayes, Charles D. Getter and William P. Davis. 1979. Ecological Assessment of the Peck Slip (19 December 1978) Oil Spill in Eastern Puerto Rico. In: Proceedings: Ecological Damage Assessment Conference. Society of Petroleum Industry Biologists, Arlington, VA. Pp. 303-317. (ERL,GB X179).

The barge PECK SLIP broke up in the Pasaje de San Juan (P.R.) on 19 December 1978. Between 440-460,000 gallons of Bunker C were discharged into the open water as the barge was towed to Port Yabucoa. During the next few days, slicks came ashore between Punta San Agustin and Yabucoa, oiling approximately 26 km of shoreline. At request of the Scientific Support Coordinator, combined ecological/geological field studies of four environments (sand beaches-46 stations; gravel/cobble beaches-3 stations; mangroves-18 transects; and shallow lagoons and coral reefs-12 stations) were conducted between 22 December 1978 and 6 January 1979. A followup survey was conducted between 28 March and 4 April 1979 at selected sand beach and mangrove stations. At the sand beach sites, biological impact was observed in three subenvironments during the first few days of the spill: 1) supratidal beach grasses, 2) intertidal wrack (mortaliy of amphipods), and 3) subtidal grass beds. After three months, all areas had completely recovered except for the supratidal grasses, which were decimated in some areas (particularly Ipomea pes-caprae and Salicornia sp.). A number of snails (four species) and crabs (two species) died on heavily oiled gravel/cobble beaches. These areas were not revisted during the followup studies. Mangroves were by far the most sensitive environment to oil impact. Two acres of mangroves were heavily oiled (less than 20 cm oiling of prop roots) while 2.6 acres were lightly to moderately oiled. By the time of the followup survey, approximately one-half acre was defoliated. Crabs (Aratus pisonii), snails (Littorina), and epiphytes within the heavily oiled zone were greatly reduced in number. The shallow lagoons offshore of a heavily oiled, high wave-energy shoreline showed very light sheens within the bottom sediment; however, there was no visible impact on lagoonal flora of fauna, nor adjacent coral reef communities.

Scott, Geoffrey I., William P. Davis, J. Michael Marcus, Thomas G. Ballous and Jeffrey A. Dahlin. 1990. Acute Toxicity, Sublethal Effects, and Bioconcentration of Chlorination Products, Viruses, and Bacteria in Edible Shellfish: A Review. In: Water Chlorination: Chemistry, Environmental Impact, and Health Effects. Robert L. Jolley et al., Editor. Lewis Publishers, Chelsea, MI. Pp. 491-518. (ERL,GB X607). (Avail. from NTIS, Springfield, VA: PB89-142699)

This report identifies, synthesizes, and summarizes published scientific data concerning toxicity, sublethal physiological effects, and uptake/depuration rates of chlorine, viruses, and bacteria in edible marine shellfish of the United States. This summary may provide environmental managers with information related to coastal zone issues, such as point-source pollution permits, hazardous materials, material spills, and non-point-source runoff regulations.

Turner, Bruce J., John F. Elder, Jr., Thomas F. Laughlin and William P. Davis. 1990. Genetic Variation in Clonal Vertebrates Detected by Simple-Sequence DNA Fingerprinting. EPA/600/J-90/384. Proc. Natl. Acad. Sci. U.S.A. 87(15):5653-5657. (ERL,GB X682). (Avail. from NTIS, Springfield, VA: PB91-163972)

The measurement of clonal heterogeneity is central to understanding the evolutionary and population genetics of the roughly 50 species of vertebrates which lack effective genetic recombination. Simple-sequence DNA fingerprinting with oligonucleotide probes (CAG)5 and (GACA)4 is a sensitive and efficient means of detecting this heterogeneity in natural populations of two clonal fishes, Poecilia formosa, an apomictic unisexual, and Rivulus marmoratus, a selfing hermaphrodite. The fingerprints are clonally stable for at least three generations. The technique clearly differentiates allozymically identical laboratory lines of R. marmoratus that were previously distinguishable only by histocompatibility analysis. The technique also reveals the first documented cases of apparent clonal turnover in a natural population of each species. Clonal variation in most natural populations is quite high. For example, a sample of 19 specimens of P. formosa from one station on the Rio Soto la Marina contained 16 clones (average clonal frequency .07). This level of clonal diversity implies that mutation, subsequent to the founding of clonal lineages, is an important source of variation in these populations. It also suggests that chance (sampling error) has a major role in determining the clonal composition of populations even though some of the clones may be divergent in biologically significant features.

Taylor, D. Scott, William P. Davis and Bruce J. Turner. 1995. Rivulus marmoratus: Ecology of Distributional Patterns in Florida and the Central Indian River Lagoon. EPA/600/J-95/459. Bull. Mar. Sci. 57(1):202-207. (ERL,GB X811).

The Neotropical killifish Rivulus marmoratus is widely distributed, but locally rare, throughout much of coastal south and central Florida. Habitat alteration has affected the species throughout the state, especially on the east coast (Indian River Lagoon) where the destruction of mangroves and impounding of high marsh for mosquito control has altered and fragmented suitable habitat. Within tropical salt-marsh and mangrove forests, R. marmoratus seems best adapted to certain micro-habitats, specifically those precluding the survival/establishment of competing fishes. On the east coast of Florida, this microhabitat preference is the land crab (Cardisoma guanhumi) burrow. In south Florida and the west coast, R. marmoratus is most often captured in stagnant pools and old mosquito ditches in mangrove forests. Populations of R. marmoratus in Florida consist of arrays of homozygous clones. Can habitat fragmentation, with its possible effects on clonal diversity, affect the continued success of this species? Are certain clones better-adapted to specific environmental conditions? Isolated populations consisting of only a single clone could persist indefinitely. Association with habitat type may answer some of these questions. Some degree of plasticity is apparent, as northern clones 'transplanted' from crab burrows survive well and achive high population levels in isolated pools more typical of south Florida habitats. However, the appearance of male fish in these pools, a phenomenon unknown in natural populations from burrows, suggests aberrant population structure. While general questions remain about the adaptive significance of clonal diversity, the mere presence of this novel fish in salt marsh/mangrove habitats may indicate that other aspects of biodiversity are in good 'order.'