Greg Masson | USA Federal Government (original) (raw)

Papers by Greg Masson

Waterbirds: The International Journal of Waterbird Biology, 2001

Mercury (Hg) contamination from a variety of point and non-point sources, including alrnospheric ... more Mercury (Hg) contamination from a variety of point and non-point sources, including alrnospheric inputs, is currently considered to be the most serious environmental threat to the well being of fish and wildlife resources in the southeastern United States. Fish consumption advisories have been issued in all ten states comprising the U.S. Fish and Wildlife Service's Southeast Region. Both freshwater and marine species have been affected with levels ranging as high as 7.0 ppm in some individuals. Many other species, including various species of reptiles, birds and mammals (including humans) are also contaminated. Impacts noted range from reproductive impairment to mortality.

Spine title: Uterine vascularity in three oviparous lizards. Thesis (M.S.)--Wichita State Univers... more Spine title: Uterine vascularity in three oviparous lizards. Thesis (M.S.)--Wichita State University, Dept. of Biological Sciences, 1985. Includes bibliographical references (leaves 47-58).

Emerging Topics in Ecotoxicology, 2011

The early morning bicycle ride along the dirt levee threaded between a wide expanse of openwater ... more The early morning bicycle ride along the dirt levee threaded between a wide expanse of openwater lake on one side and shallow marshes on the other. The humid Florida air carried the organic smells of soil and plants coupled with the beating of dragonfly wings, thousands and thousands of them hovering over the pickerelweed. Birds were everywhere-blackbirds and cardinals singing, northern harriers and red-shouldered hawks circling, herons of all kinds wading. A softshell turtle, bigger than my bike's tire, lifted its extra terrestrial head to watch us approach, and then eased back into the lake. An alligator crossed our path, walking high 190 R. Conrow et al.

Journal of Experimental Zoology, 1985

ABSTRACT Juvenile lizards (Eumeces obsoletus) treated with FSH exhibited germ cell proliferation.... more ABSTRACT Juvenile lizards (Eumeces obsoletus) treated with FSH exhibited germ cell proliferation. However, only the first stages of oogenesis or spermatogenesis were elicited. No difference in spermatogenic stage was observed between treatment groups. Vitellogenesis was not observed in treated females although the primary (largest) follicles exhibited a granulosa composed of a single cell type indicative of a follicle just prior to yolking. In addition to gonadal effects, accessory structures which are steroid dependent exhibited changes. Oviductal weight increased significantly with FSH treatment. Histological examination revealed that both oviductal glands and oviductal epithelium increased in size as did epididymal cell heights in males. These structures are steroid dependent in adults. These data suggest that juvenile gonads respond to gonadotropin although not in a typical adult manner. Sexual maturation is not only dependent on gonadal responsiveness but on the maturation of the hypothalamohypophysial axis and thus, on gonadotropin secretion as well. In addition, a critical amount of lipid storage may be required for vitellogenesis and gonadal function.

Water, Air, & Soil Pollution, 1995

General and Comparative Endocrinology, 1992

General and Comparative Endocrinology, 1997

We examined ovarian and oviducal gross morphology and collected blood samples from wild female al... more We examined ovarian and oviducal gross morphology and collected blood samples from wild female alligators in central Florida during most of the year. Females with vitellogenic follicles were observed throughout the year, although ovaries containing follicles larger than 15 mm were seen only during the spring and early summer (March-June). We detected a poor relationship between female body size and the number of vitellogenic follicles whereas body size was significantly correlated with clutch size. Plasma samples were analyzed for (1) estradiol-17␤ (E 2 ), testosterone (T), and corticosterone by specific radioimmunoassays; (2) vitellogenin by onedimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis; and (3) total protein, phosphorus, and calcium by spectrophotometric assays. Reproductively active females showed elevated plasma concentrations of E 2 during the fall (September-November) and spring (March-May) whereas non-reproductively active females exhibited basal levels with no apparent peaks. Vitellogenin was detected in the plasma during the same months that plasma E 2 concentrations were elevated. Elevated plasma vitellogenin and E 2 were not correlated with plasma total protein but were correlated with plasma calcium concentration. During late vitellogenesis, plasma T concentrations were elevated in reproductively active females coincident with a period of intense courtship and mating. Corticosterone plasma concentrations exhibit no significant monthly variation, nor apparent changes during various stages of reproductive activity although plasma concentrations were elevated during late gravidity. Our data suggest that female reproductive activity begins in the fall with an increase in plasma E 2 concentration in September or October and vitellogenesis in October. Ovarian activity slows during winter and reactivates with the onset of spring. 1997 Academic Press During the past 20 years, our knowledge of the biology of the ancient, 200-million-year-old, reptilian order Crocodilia has increased significantly. The reproductive biology of the American alligator (Alligator mississippiensis) has been the focus of extensive research during this time (see . A substantial research effort began in response to an apparent sharp decline in population numbers in the 1960s (see . Although many aspects of the reproductive biology of alligators have been studied, much basic information is still missing or incomplete.

Environmental Health Perspectives, 1994

The reproductive development of alligators from a contaminated and a control Lake in central Flor... more The reproductive development of alligators from a contaminated and a control Lake in central Florida was cmmined. Lake Apopka is adjacent to an EPA Sue d ste listed due to an pensive spill of dicofol and DDT or its m elites. These compounds can act as estrogns. Contminants in the lake also have derived m extensive a.gicul activities around the lake that continue today and a sewage treatment facility associated with the city of Winter Garden, Flori We examined t hypothis that an estrogen conAm has caused the current lure in recruitment of alligators on Lk Apopka. Supporting data include the following, At 6 months of age, mae lligaton fiom La Apopka had plasma esradiol-170.

Wildlife …, 2011

... Lake Apopka is situated between two of the state's oldest sand dune ridge systems and ha... more ... Lake Apopka is situated between two of the state's oldest sand dune ridge systems and has ... The HQs for DDTx (DDD + DDE + DDT), chlor-dane, dieldrin, and toxaphene were summed to ... The MOU also provided for SJRWMD to pay past costs incurred by the Department of the ...

Archives of Environmental Contamination and Toxicology, 2002

The effect of contamination on eggshell mineralization has been studied for clapper rails (Rallus... more The effect of contamination on eggshell mineralization has been studied for clapper rails (Rallus longirostris) inhabiting a contaminated salt marsh in coastal Georgia. To assess the impact of contaminants, the thickness, microstructure (crystal orientation), mineral composition, and chemistry of shell material were analyzed from a contaminated site and a nearby reference site using optical microscopy, X-ray diffraction, inductively coupled plasma mass spectrometry, and gas chromatography with electron capture detector. Eggshells from the contaminated site were generally thinner than those from the reference site. Also, eggshells from the contaminated site were abnormally brittle and contained anomalous microstructural attributes. The combination of reduced shell thickness and anomalous microstructure resulted in weaker eggshells, which in turn could pose a significant threat to the reproductive success of the affected population. PCB concentrations in eggshells were at background levels in both sites. Eggshells from the contaminated site had higher concentrations of heavy metals, specifically mercury, than the reference site. The structural changes observed in eggshells may be related to the concentration of specific metals (e.g., Mg, Cu, Zn, Pb, and Hg) in shell, however, statistical analyses indicated that metals only explained a small portion of the observed variation in properties (i.e., thickness, crystal orientation). Further analysis is required to better constrain the factors leading to unusually weak eggshells in the contaminated site.

In the United States (U.S.), oil spill response planning, preparedness, and response requirements... more In the United States (U.S.), oil spill response planning, preparedness, and response requirements are dictated primarily by the National Oil and Hazardous Substances Pollution Contingency Plan, a regulation that implements the Oil Pollution Act of 1990, the Clean Water Act, and the Comprehensive Environmental Response, Compensation and Liability Act. At the planning stage, these regulations require the development of national, regional, and local response capabilities and promote overall coordination among responders. During a spill, these capabilities are utilized by the Federal On-Scene Coordinator (FOSC) to analyze whether response actions are likely to impact protected resources. The consultation process required under Federal statutes, charges the FOSC to consult with Federal, state, Tribal entities, and other Federal agencies to determine potential effects of response actions during an incident and to develop strategies to avoid, minimize, and mitigate those effects (40 CFR 30...