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Prospector II: Towards a knowledge base for mineral deposits

What began in the mid-seventies as a research effort in designing an expert system to aid geologists in exploring for hidden mineral deposits has in the late eighties become a full-sized knowledge-based system to aid geologists in conducting regional mineral resource assessments. Prospector II, the successor to Prospector, is interactive-graphics oriented, flexible in its representation of mineral deposit models, and suited to regional mineral resource assessment. In Prospector II, the geologist enters the findings for an area, selects the deposit models or examples of mineral deposits for consideration, and the program compares the findings with the models or the examples selected, noting the similarities, differences, and missing information. The models or the examples selected are ranked according to scores that are based on the comparisons with the findings. Findings can be reassessed and the process repeated if necessary. The results provide the geologist with a rationale for identifying those mineral deposit types that the geology of an area permits. In future, Prospector II can assist in the creation of new models used in regional mineral resource assessment and in striving toward an ultimate classification of mineral deposits. ?? 1994 International Association for Mathematical Geology.

Mathematical Geology

Windrow composting as an effective method to dispose of large numbers of fish

During July 1998, at the USGS Leetown Science Center, Kearneysville, West Virginia, an epizootic occurred in 16-month-old Atlantic salmon (Salmo salar). The cause ofmortality was diagnosed as furunculosis, a serious disease in salmonid fishes caused by the bacterium Aeromonas salmonicida. The fish were being maintained as part ofongoing research and were held in uncovered 30-m-Iong concrete raceways, each supplied with about 757 L per minute of 12 ?C pathogen-free spring water. The means by which the fish became infected could not be determined, and there was no recent history offurunculosis in the hatchery system.

Biological Information and Technology Notes

Handbook to the partners in flight population estimates database, version 3.0

This document describes the content of Version 3.0 of the Partners in Flight (PIF) Population Estimates Database, which provides population estimates for breeding USA/Canada landbirds at several geographic scales following the Partners in Flight approach described initially in Rich et al. (2004) and by Rosenberg and Blancher (2005) and most recently refined by Stanton et al. (2019). The Handbook also provides details about how the estimates were derived, information on limitations and caveats, a guide to using the estimates, and future desired directions for improving the estimates. This version of the database is intended as a companion to the Partners in Flight Landbird Conservation Plan: 2016 Revision for Canada and Continental United States (Rosenberg et al. 2016), although estimates for most species included in the database have been updated from those used in the 2016 Plan. Most of the estimates in the database are based on North American Breeding Bird Survey (BBS) data for landbirds from the decade 2006–2015. The information in this 2019 Version of the Handbook, for Version 3.0 of the database, describes all changes that have been made to the database since 2007 (Version 1.0, cf. Blancher et al. 2007)—including the additions documented in the Handbook for Version 2.0 (Blancher et al. 2013)—and therefore serves as a single source document describing the current database. Version 3.0 of the database addresses some of the recommendations suggested by Thogmartin et al. (2006) but does not yet fully address other limitations noted by Thogmartin et al. (2006), Blancher et al. (2007), Thogmartin (2010), Matsuoka et al. (2012), and Twedt (2015). By far, the most substantial change to the database comprises the incorporation of quantitative uncertainty bounds around population estimates for most species (see Stanton et al. 2019 for details). PIF Science anticipates that future versions of the database will occur in stages: first, improving elements of the basic PIF approach (e.g., incorporating more recent BBS data, updating Time of Day Adjustments, and refining Pair Adjustments); next, addressing additional concerns inherent in the PIF approach (e.g., replacing average maximum detection distance bins with research-derived species-specific effective detection radii); and later, perhaps replacing the sample-based PIF approach with a spatially-explicit, model-based (pixel-based) approach that more deliberately incorporates habitat and road biases and the proportion of birds available but not detected by current sampling methodology. This current Version 3.1 of the Handbook updates citations in the Literature Cited and incorporates relatively minor improvements in text clarity over the previous 3.0 version. The content of the Population Estimates Database itself remains the same except for changes to the global and USA/Canada estimates for Northern Bobwhite and Black Vulture.

Partners in Flight Technical Publication

HiRISE observations of fractured mounds: Possible Martian pingos

Early images from the High Resolution Imaging Science Experiment (HiRISE) camera have revealed small fractured mounds in the Martian mid‐latitudes. HiRISE resolves fractures on the mound surfaces, indicating uplift, and shows that the mound surface material resembles that of the surrounding landscape. Analysis of Mars Orbiter Camera (MOC) images shows that in Utopia Planitia the mounds lie almost exclusively between 35–45°N. This range coincides with the peak‐abundance latitudes of several landforms attributed to ground water or ice, including gullies, and suggests a ground ice‐related origin. The best terrestrial analogues for the observed mound morphology are pingos, although some differences are noted. The presence of uncollapsed pingos would indicate the presence of near‐surface ground ice in the Martian mid‐latitudes, at depths greater than the ∼1 meter sampled by orbital spectrometers. Pingo formation may require near‐surface liquid water, which is consistent with a shallow groundwater model for the origin of gullies.

Geophysical Research Letters

Leaf optical property changes associated with the occurrence of Spartina alterniflora dieback in Coastal Louisiana related to remote sensing mapping

In order to provide a remote sensing solution that would detect both the initial onset and monitor the early, as well as, the later stages of impact progression, changes in live leaf optical properties were compared along transects spanning impacted coastal Louisiana marsh sites. Green and red edge reflectance trends generally represented the early stages and fairly well the later stages of dieback progression, while blue and red reflectance and absorption trends represented the later stages of marsh impact that were most closely related to visible signs of marsh impact. Leaf reflectance in the near infrared (NIR) was not compatible with visual reflectance trends and did not co-vary with derived indicators of leaf water content, and thereby, water stress. Predicted from reflectance ratios, carotene tended to remain constant or increase relative to chlorophyll following noted changes in stressed plants at the two least impacted sites, while the pigments co-varied at the two most impacted sites. As an operational solution most amenable for satellite remote sensing, the NIR /red ratio followed blue and red reflectance trends while the NIR /green ratio mimicked the green and red edge reflectance trends indicating impact onset and progression, as well as, generally portraying blue and red reflectance trends indicating later stages of impact. The NIR/ green ratio magnitude and range generally increased from the most to least impacted site providing a convenient method to detect dieback onset and monitor dieback progression. This research demonstrated that remote sensing mapping at these sites could offer a more accurate perception of dieback severity distribution than offered by determinations relying on visible indicators of marsh changes.

Louisiana

Environmental issues associated with fossil fuel resources; an evaluation of research opportunities for the U.S. Geological Survey's Energy Resources Program

Fossil fuel consumption in the United States has nearly tripled within the last 50 years (fig. 1), and is expected to continue increasing. As our knowledge and awareness of environmental consequences related to fossil fuel extraction and use grow, we as a nation, face the challenge of balancing our energy requirements with a desire for environmentally cleaner fuel. To help meet this challenge, the Energy Resources Program (ERP) of the Geologic Division (GD), U.S. Geological Survey (USGS) sponsored three internal workshops and a World Wide Web (WWW) workshop. The primary goal of these workshops was to identify those environmental issues that are related to fossil fuels, are national in scope, and are within the purview of the USGS as an earth-science government agency. Those issues so identified will be prioritized according to ERP's future research plan and according to the extent they provide an environmental framework for ERP's petroleum and coal assessments. The purpose of this paper is to provide the results of the internal and WWW workshops as proposed topics of research for future ERP work, delineate studies to answer the questions related to each proposed research area, and link the studies to the seven science goals of the Geologic Division. The information provided herein will be used in preparing the USGS Geologic Division's FY2000 prospectus and ERP's next five-year strategic plan. Acknowledgements. The authors wish to acknowledge information on ERP environmental projects provided by Les Magoon, Paul Lillis, Keith Kvenvolden, Tom Lorenson, and Bob Rosenbauer. Peter Schweitzer was instrumental in providing the software for the WWW workshop, Cheryl Adkisson for constructing the workshop web pages, and Laura Friedrich for constructing the web pages summarizing the internal workshops. Stan Mroczkowski, Jim Otton, Donna Read, and Dorothy Tanti provided notes of or logistical assistance for the internal workshops. This report reflects the collective input of numerous USGS managers and scientists their participation in the workshops is greatly appreciated.

Open-File Report

Toxicological responses to sublethal anticoagulant rodenticide exposure in free-flying hawks

An important component of assessing the hazards of anticoagulant rodenticides to non-target wildlife is observations in exposed free-ranging individuals. The objective of this study was to determine whether environmentally realistic, sublethal first-generation anticoagulant rodenticide (FGAR) exposures via prey can result in direct or indirect adverse effects to free-flying raptors. We offered black-tailed prairie dogs ( Cynomys ludovicianus ) that had fed on Rozol® Prairie Dog Bait (Rozol, 0.005% active ingredient chlorophacinone, CPN) to six wild-caught red-tailed hawks (RTHA, Buteo jamaicensis ), and also offered black-tailed prairie dogs that were not exposed to Rozol to another two wild-caught RTHAs for 7 days. On day 6, blood was collected to determine CPN’s effects on blood clotting time. On day 7, seven of the eight RTHAs were fitted with VHF radio telemetry transmitters and the RTHAs were released the following day and were monitored for 33 days. Prothrombin time (PT) and Russell’s viper venom time confirmed that the CPN-exposed RTHAs were exposed to and were adversely affected by CPN. Four of the six CPN-exposed RTHAs exhibited ptiloerection, an indication of thermoregulatory dysfunction due to CPN toxicity, but no signs of intoxication were observed in the reference hawk or the remaining two CPN-exposed RTHAs. Of note is that PT values were associated with ptiloerection duration and frequency; therefore, sublethal CPN exposure can directly or indirectly evoke adverse effects in wild birds. Although our sample sizes were small, this study is a first to relate coagulation times to adverse clinical signs in free-ranging birds.

Colorado

National Park Service staff perspectives on how climate change affects visitor use

1. Many public lands, including those managed by the U.S. National Park Service(NPS), have the purpose of conserving natural and cultural resources and providing opportunities for visitors to recreate in and enjoy these areas. Achieving this mission becomes more challenging as drought, flooding, increasing temperatures and other climatic change effects are impacting NPS lands and visitors and affecting factors such as visitation, recreation access and health and safety among other aspects of park operations. 2. However, the literature lacks insights from staff dealing with on-the-ground climate impacts to visitor use. To address this gap, we held semi-structured interviews with 63 staff from 31 NPS units across the United States (U.S.) to better understand the effects of climate change on visitor use. We qualitatively analysed the interviews using both deductive and inductive methods to identify key themes. 3. Interview participants consistently noted that climate change is already affecting visitor use at their parks. For instance, increasing temperatures are negatively affecting both staff and visitor safety at parks nationwide, whereas all coastal parks within our sample are already experiencing impacts from sea-level rise or more frequent and severe coastal storms and hurricanes. Other impacts include reduced recreational access, damaged infrastructure and cultural resources and diminished visitor experiences due to fire and smoke. 4. Similarly, concerns about future impacts often revolved around the health and safety of visitors and staff—particularly related to wildfire and smoke, water quality and availability, and increased heat—and climate change forever altering parks. 5. Our research shows staff in parks and protected areas are noticing effects of climate change on visitor use; some of these impacts have not been previously documented in the scientific literature. Study results highlight future visitor use management research needs and key topics to consider for visitor use planning processes.

People and Nature

One thousand years of fires: Integrating proxy and model data

The current fires raging across Indonesia are emitting more carbon than the annual fossil fuel emissions of Germany or Japan, and the fires are still consuming vast tracts of rainforest and peatlands. The National Interagency Fire Center (www.nifc.gov) notes that 2015 is one worst fire years on record in the U.S., where more than 9 million acres burned -- equivalent to the combined size of Massachusetts and New Jersey. The U.S. and Indonesian fires have already displaced tens of thousands of people, and their impacts on ecosystems are still unclear. In the case of Indonesia, the burning peat is destroying much of the existing soil, with unknown implications for the type of vegetation regrowth. Such large fires result from a combination of fire management practices, increasing anthropogenic land use, and a changing climate. The expected increase in fire activity in the upcoming decades has led to a surge in research trying to understand their causes, the factors that may have influenced similar times of fire activity in the past, and the implications of such fire activity in the future. Multiple types of complementary data provide information on the impacts of current fires and the extent of past fires. The wide array of data encompasses different spatial and temporal resolutions (Figure 1) and includes fire proxy information such as charcoal and tree ring fire scars, observational records, satellite products, modern emissions data, fire models within global land cover and vegetation models, and sociodemographic data for modeling past human land use and ignition frequency. Any single data type is more powerful when combined with another source of information. Merging model and proxy data enables analyses of how fire activity modifies vegetation distribution, air and water quality, and proximity to cities; these analyses in turn support land management decisions relating to conservation and development.

Frontiers of Biogeography

Resource inventory of marine and estuarine fishes of the West Coast and Alaska: A checklist of North Pacific and Arctic Ocean species from Baja California to the Alaska - Yukon border

This is a comprehensive inventory of the fish species recorded in marine and estuarine waters between the Alaska–Yukon Territory border in the Beaufort Sea and Cabo San Lucas at the southern end of Baja California and out about 300 miles from shore. Our westernmost range includes the eastern Bering Sea and Aleutian Islands. In addition, we have also included our best impressions of the species that might reasonably be expected to be members of the West Coast ichthyofauna but have not yet been captured or reported within our study area. These species are marked with an asterisk (*) and have been reported (1) in the western Bering Sea; (2) off Canada’s Yukon Territory and adjacent portions of the Northwest Territories; (3) along the southern-eastern tip (non-Pacific side) of Baja California; and (4) in waters somewhat beyond 300 miles from shore. Although the term West Coast usually refers to the coast of the continuous western states, our usage herein means the entire study area. The West Coast inventory within this range encompasses fish fauna from 44 orders, 232 families, and a minimum of 1,450 species. Please note that introduced and invasive fish species are marked by double asterisks (**) and that their scientific names are highlighted in gray. We have compiled this document because the most geographically inclusive previous inventories (Jordan and Evermann 1896a, Jordan et al. 1930) are largely of historical interest and are out of date. More recent lists and compilations have either focused on relatively narrow taxonomic groups (e. g., Kramer et al. 1995, Love et al. 2002), are regional in scope (e. g., Hart 1973, Hubbs et al. 1979, Mecklenburg et al. 2002), or focus on commonly observed species (e. g., Miller and Lea 1972, Eschmeyer and Herald 1983). With the explosion of coastal research and environmental assessments, beginning in the 1970s, and more recently, renewed scientific interest in biodiversity (e.g., effects of global climate change), our own studies on related subjects regarding fish populations, assemblages, and biological habitats, suggested this was the appropriate time to update and summarize our knowledge.

Report

Albert H. Munsell: A sense of color at the interface of art and science

The color theory conceived and commercialized by Albert H. Munsell (1858-1918) has become a universal part of the lexicon of soil science. An American painter noted for his seascapes and portraits, he had a long-standing interest in the description of color. Munsell began studies aimed at standardizing color description, using hue, value, and chroma scales, around 1898. His landmark treatise, "A Color Notation," was published in 1905. Munsell died about 30 years before his color charts came into wide-spread use in soil survey programs in the United States. Dorothy Nickerson, who began her career as secretary and laboratory assistant to Munsell's son, and later spent 37 years at USDA as a color-science specialist, did much to adapt the Munsell Color System to soil-color usage. The legacy of color research pioneered by A.H. Munsell is honored today by the Munsell Color Science Laboratory established in 1983 at the Rochester Institute of Technology.

Soil Science

Landsat Science Team meeting: Winter 2015

The summer meeting of the joint U.S. Geological Survey (USGS)–NASA Landsat Science Team (LST) was held at the USGS’s Earth Resources Observation and Science (EROS) Center July 7-9, 2015, in Sioux Falls, SD. The LST co-chairs, Tom Loveland [EROS—Senior Scientist] and Jim Irons [NASA’s Goddard Space Flight Center (GSFC)—Landsat 8 Project Scientist], opened the three-day meeting on an upbeat note following the recent successful launch of the European Space Agency’s Sentinel-2 mission on June 23, 2015 (see image on page 14), and the news that work on Landsat 9 has begun, with a projected launch date of 2023. With over 60 participants in attendance, this was the largest LST meeting ever held. Meeting topics on the first day included Sustainable Land Imaging and Landsat 9 development, Landsat 7 and 8 operations and data archiving, the Landsat 8 Thermal Infrared Sensor (TIRS) stray-light issue, and the successful Sentinel-2 launch. In addition, on days two and three the LST members presented updates on their Landsat science and applications research. All presentations are available at landsat.usgs.gov/science_LST_Team_ Meetings.php.

The Earth Observer

The North American carbon budget: Past, present, and future

This chapter nicely summarizes and synthesizes the latest scientific information on the North American carbon budget by incorporating terrestrial, anthropogenic, aquatic, and coastal margin CO 2 and CH 4 dynamics. Starting with a historical context, the chapter summarizes current understanding of the magnitudes and trends of carbon stocks and fluxes at the continental scale. It also provides a regional context by stratifying the continent to countries and climate assessment regions and discusses the societal drivers, impacts, and carbon management decisions. Knowledge gaps and research needs are also identified. This chapter is well-written and clearly organized, and provides a broad context beyond individual chapters. Some of the main ways the chapter can be improved include the following: some work is needed on the Key Findings (discussed below); the goals and objectives should be explicitly described; critical content areas missing from the chapter are interannual variability of carbon fluxes and impacts of severe and extended droughts; indicators and feedbacks are missing from Section 2.4; consistent use of units is recommended; numbers with 3-4 significant digits over-state the confidence the reader should have, and all numbers should include uncertainties. And one broader concern to note: This chapter follows the global overview in Chapter 1, where “sinks” are sinks in the cycle perturbed by anthropogenic CO 2 and CH 4 , and the assumption is that globally, the net unperturbed background sinks are zero summed across all reservoirs. Yet in this chapter, “sinks” are net fluxes out of the atmosphere, background + perturbation. For the coastal ocean, inland waters, etc.—where lateral transport is significant—these sources and sinks include background/pre-industrial fluxes that are balanced by fluxes elsewhere. These distinctions must be made clear so that the reader is not given an impression of a greater or lesser sink for anthropogenic CO 2 than is there (e.g., P74, lines 4-6).

Book chapter

Archive of Sidescan Sonar and Swath Bathymetry Data Collected During USGS Cruise 13CCT04 Offshore of Petit Bois Island, Gulf Islands National Seashore, Mississippi, August 2013

In August of 2013, the U.S. Geological Survey conducted a geophysical survey offshore of Petit Bois Island, Mississippi. This effort was part of the U.S. Geological Survey Gulf of Mexico Science Coordination partnership with the U.S. Army Corps of Engineers to assist the Mississippi Coastal Improvements Program and the Northern Gulf of Mexico Ecosystem Change and Hazards Susceptibility Project, by mapping the shallow geologic stratigraphic framework of the Mississippi Barrier Island Complex. This geophysical survey will provide additional data necessary for scientists to define, interpret, and provide baseline bathymetry and seafloor habitat for this area, and to aid scientists in predicting future geomorphological changes of the islands with respect to climate change, storm impact, and sea-level rise. Furthermore, these data will provide information for barrier island restoration, particularly in Camille Cut, and protection for the historical Fort Massachusetts on Ship Island, Mississippi. The geophysical data were collected during one cruise ( USGS Field Activity Numbers 13CCT04 ) aboard the Research Vessel Tommy Munro offshore along the gulf side of Petit Bois Island, Gulf Islands National Seashore, Mississippi. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATH plus interferometric sonar (468 kilohertz (kHz)), an EdgeTech 424 (4-24 kHz), an EdgeTech 525i chirp subbottom profiling system, and a Klein 3900 sidescan sonar system. This report serves as an archive of the processed interferometric swath bathymetry and sidescan sonar data. Geographic information system data products include an interpolated digital elevation model, an acoustic backscatter mosaic, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. NOTE: These data are scientific in nature and are not to be used for navigation. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Mississippi

The effects of swimming exercise and dissolved oxygen on growth performance, fin condition and precocious maturation of early-rearing Atlantic salmon Salmo salar

Swimming exercise, typically measured in body-lengths per second (BL/s), and dissolved oxygen (DO), are important environmental variables in fish culture. While there is an obvious physiological association between these two parameters, their interaction has not been adequately studied in Atlantic salmon Salmo salar . Because exercise and DO are variables that can be easily manipulated in modern aquaculture systems, we sought to assess the impact of these parameters, alone and in combination, on the performance, health and welfare of juvenile Atlantic salmon. In our study, Atlantic salmon fry were stocked into 12 circular 0.5 m 3 tanks in a flow-through system and exposed to either high (1.5–2 BL/s) or low (<0.5 BL/s) swimming speeding and high (100% saturation) or low (70% saturation) DO while being raised from 10 g to approximately 350 g in weight. Throughout the study period, we assessed the impacts of exercise and DO concentration on growth, feed conversion, survival and fin condition. By study's end, both increased swimming speed and higher DO were independently associated with a statistically significant increase in growth performance ( p < .05); however, no significant differences were noted in survival and feed conversion. Caudal fin damage was associated with low DO, while right pectoral fin damage was associated with higher swimming speed. Finally, precocious male sexual maturation was associated with low swimming speed. These results suggest that providing exercise and dissolved oxygen at saturation during Atlantic salmon early rearing can result in improved growth performance and a lower incidence of precocious parr.

Aquaculture Research

National energy research seismic library; Powder River basin, Montana-Wyoming; surface reflection and vertical seismic profile data used in seismic-stratigraphic investigations for ground-water aquifers and hydrocarbon traps

This Digital Data Series publication contains both raw and processed seismic data recorded during the period 1975 through 1978 by several geophysical service companies under contract to the USGS in the following study areas of the Powder River Basin, Montana and Wyoming: 1. Powder River and Custer Counties, MT (T. 1 S., T. 1-2 N., R. 53-54 E.) 2. Carter County, MT (T. 57-58 N., R. 65 W.) and Crook County, WY (T. 9 S., R.57-58 E.) 3. Powder River and Carter Counties, MT (T. 8 S., R. 53-55 E.) 4. Niobrara County, WY (T. 36-38 N., R. 61-62 W.) and Weston County, WY (T. 45 N., R. 61 W.) Four multichannel Vibroseis seismic lines, six Vertical Seismic Profiles (VSP's), and associated support material (observer's notes, X-Y coordinates, elevations of source and receivers, for example) are included. The raw (unprocessed) field data and a processed version of each surface profile and VSP are contained in standard SEG-Y format files; support material are in ASCII format text files. The processed surface data are versions which were reprocessed by the USGS in 1995 using state-of-the-art seismic data processing software.

Data Series

Seismic wave triggering of nonvolcanic tremor, episodic tremor and slip, and earthquakes on Vancouver Island

[1] We explore the physical conditions that enable triggering of nonvolcanic tremor and earthquakes by considering local seismic activity on Vancouver Island, British Columbia during and immediately after the arrival of large-amplitude seismic waves from 30 teleseismic and 17 regional or local earthquakes. We identify tremor triggered by four of the teleseismic earthquakes. The close temporal and spatial proximity of triggered tremor to ambient tremor and aseismic slip indicates that when a fault is close to or undergoing failure, it is particularly susceptible to triggering of further events. The amplitude of the triggering waves also influences the likelihood of triggering both tremor and earthquakes such that large amplitude waves triggered tremor in the absence of detectable aseismic slip or ambient tremor. Tremor and energy radiated from regional/local earthquakes share the same frequency passband so that tremor cannot be identified during these smaller, more frequent events. We confidently identify triggered local earthquakes following only one teleseism, that with the largest amplitude, and four regional or local events that generated vigorous aftershock sequences in their immediate vicinity. Earthquakes tend to be triggered in regions different from tremor and with high ambient seismicity rates. We also note an interesting possible correlation between large teleseismic events and episodic tremor and slip (ETS) episodes, whereby ETS events that are “late” and have built up more stress than normal are susceptible to triggering by the slight nudge of the shaking from a large, distant event, while ETS events that are “early” or “on time” are not.

Vancouver Island

Habitat impacts of offshore drilling, eastern Gulf of Mexico

In this survey six offshore exploratory drill sites in a variety of environments and water depths were examined using a small research submersible. Sites varied from locations off northwest Florida to as far west as offshore Alabama. Water depths ranged from 21 m (70 ft) to 149 m (489 ft), and bottom sediments ranged from carbonate mud to Shelly quartz sand and silt to hard limestone. The age of the sites (the time between cessation of drilling activities and our observations) ranged from 15 months to 17 years . In a previous MMS-funded study, Shinn et al. (1989) and Dustan et al . (1991) examined eight sites off South Florida, where the age of the sites ranged from 2 to 29 years. The study documented repeatedly variability of impact from site to site . In the present study, we note a similar wide divergence of impacts . Using the concentration of barium (the major component of drill mud), cuttings, and trace metals as a basis, we found that time is the single most important factor determining the nature of habitat recovery. Older sites, particularly the 17-year-old site, were relatively pristine. At a 7-year-old site, two hurricanes did far more damage than drilling . At other sites, we documented a significant amount of discarded debris, and at two 5-year-old sites, large concentrations of barium and cuttings. Impacts, such as the extent of debris and cuttings, affected the bottom ranging in area from almost negligible (17-year-old site) to as much as 3 acres (4-year-old site) . As suspected, those sites with the most debris and/or open boreholes attracted the most abundant and diverse fish fauna.

Open-File Report