Determination of the distribution of shallow-water seagrass and drift algae communities with acoustic seafloor discrimination

The spatial distribution of seagrass and algae communities can be difficult to determine in large, shallow lagoon systems where high turbidity prevents the use of optical methods like aerial photography or satellite imagery. Further complications can arise when algae are not permanently attached to the substratum and drift with tides and currents. A study using acoustic seafloor discrimination was conducted in the Indian River Lagoon (Florida, USA) to determine the extent of drift algae and seagrass. Acoustic surveys using the QTC View V system based on 50 and 200 kHz transducers were conducted near Sebastian Inlet. Results indicate that areas of seagrass can be identified, and are mixed with a high abundance of drift algae. Nearest-neighbor extrapolation was used to fill in spaces between survey lines and thus obtain spatially cohesive maps. These maps were then ground-truthed using data from towed video and compared using confusion matrices, The maps showed a high level of agreement (60%) with the actual distribution of algae, however some confusion existed between bare sand and algae as well as seagrass

Assessing the accuracy of acoustic seabed classification for mapping coral reef environments in South Florida (Broward County, USA)

The Atlantic coast of Broward County, Florida (USA) is paralleled by a series of progressively deeper, shore-parallel coral reef communities. Two of these reef systems are drowned early Holocene coral reefs of 5 ky and 7 ky uncorrected radiocarbon age. Despite the case of access to these reefs, and their major contribution to the local economy, accurate benthic habitat maps of the area are not available. Ecological studies have shown that different benthic communities (i.e. communities composed of different biological taxa) exist along several spatial gradients on all reefs. Since these studies are limited by time and spatial extent, acoustic surveys with the QTCView V bottom classification system based on a 50 kHz transducer were used as an alternative method of producing habitat maps. From the acoustic data of a 3.1 km(2) survey area, spatial prediction maps were created for the area. These were compared with habitat maps interpreted from in situ data and Laser Airborne Depth Sounder (LADS) bathymetry, in order to ground-truth the remotely sensed data. An error matrix was used to quantitatively determine the accuracy of the acoustically derived spatial prediction model against the maps derived from the in situ and LADS data sets. Confusion analysis of 100 random points showed that the system was able to distinguish areas of reef from areas of rubble and sand with an overall accuracy of 61%. When asked to detect more subtle spatial differences, for example, those between distinct reef communities, the classification was only about 40% accurate. We discuss to what degree a synthesis of acoustic and in situ techniques can provide accurate habitat maps in coral reef environments, and conclude that acoustic methods were able to reflect the spatial extent and composition of at least three different biological communities.

Determination of the distribution of shallow-water seagrass and drift algae communities with acoustic seafloor discrimination.

The spatial distribution of seagrass and algae communities can be difficult to determine in large, shallow lagoon systems where high turbidity prevents the use of optical methods like aerial photography or satellite imagery. Further complications can arise when algae are not permanently attached to the substratum and drift with tides and currents. A study using acoustic seafloor discrimination was conducted in the Indian River Lagoon (Florida, USA) to determine the extent of drift algae and seagrass. Acoustic surveys using the QTC View V system based on 50 and 200 kHz transducers were conducted near Sebastian Inlet. Results indicate that areas of seagrass can be identified, and are mixed with a high abundance of drift algae. Nearest-neighbor extrapolation was used to fill in spaces between survey lines and thus obtain spatially cohesive maps. These maps were then ground-truthed using data from towed video and compared using confusion matrices, The maps showed a high level of agreement (60%) with the actual distribution of algae, however some confusion existed between bare sand and algae as well as seagrass.

Specialty competencies for residents in aerospace medicine.

BACKGROUND: The American College of Preventive Medicine (ACPM), with sponsorship from the Health Resources Administration (HRSA), has published core competencies that are common to all preventive medicine residencies-aerospace medicine (ASM), occupational medicine (OM), and general preventive medicine/public health (GPM/PH). Further development of specialty area competencies for ASM residents was addressed by a working group comprised of representatives from each of the four ASM residency programs. METHODS: Representatives from the U.S. Air Force School of Aerospace Medicine, Wright State University, University of Texas Medical Branch-Galveston, and the Naval Operational Medicine Institute convened to develop a set of broad competency statements for ASM residents that would encompass the breadth of ASM residency training as it is currently provided in the U.S. RESULTS: A listing of six ASM resident competencies, with supporting skill sets, are presented. In combination with the ACPM core competencies, the ASM resident competencies represent a refocusing of educational objectives on skills attainment. CONCLUSIONS: The ASM resident competencies identify the capabilities of graduating ASM residents as distinct from OM and GPM/PH residents. At the same time, they are broad enough to permit specific areas of emphasis (e.g., military, civil, or space) to be pursued within the various ASM residencies. This represents the first successful attempt to draft a consolidated statement of educational objectives that has universal acceptance and applicability across all U.S. aerospace medicine residencies.

Canadian experience with civilian pilots allowed to fly following an acute myocardial infarction.

Concern has been expressed about allowing pilots to fly following an acute myocardial infarction. From the beginning of 1967 to the end of 1987, 141 Canadian pilots have been licensed following an acute myocardial infarction, 21 of these for the first time. About 200 pilots did not qualify for relicensure. The mean age (+/- SD) of 127 pilots who experienced symptomatic acute myocardial infarction was 46.8 +/- 8.2 years (range 21 to 70). All but one were males. Of 42 commercial pilots who were relicensed, only 11 returned to commercial flying, seven with a restriction. Of 130 private pilots, all but one returned to unrestricted flying. The mean time from acute myocardial infarction to relicensure was 4.3 +/- 2.6 years (range 0.6 to 14.9). During the years 1977-86 inclusive, for which records are available, there has been no aviation fatality in Canada attributed to a cardiac cause involving pilots licensed post acute myocardial infarction. One relicensed pilot crashed shortly after take-off and, with no evidence for cardiac incapacitation, his death was listed as accidental. Therefore, individuals who satisfy strict medical criteria can be licensed to fly post acute myocardial infarction without compromising air safety.

Pleistocene sea levels from raised coral reefs of haiti.

The elevations and ages of a sequence of three uplifted Pleistocene coral reefs on the Northwest Peninsula of Haiti have been determined. With the assignment of a sea level of +6 meters (relative to the present day) at 130,000 years before present and constant uplift of the reefs, the data indicate that sea level stood -10 and -13 meters at 108,000 and 81,000 years before present, respectively. These results are in substantial agreement with those reported for Barbados and New Guinea and support the hypothesis of constant uplift for each area. Sea level data from raised reefs indicate that the interglacial marine oxygen isotope oscillations during oxygen isotope stage 5 are a result of 30 percent ice volume effects and 70 percent temperature effects.

Aircraft accident survivors as witnesses.

This is a study of the reliability of aircrash survivors as witnesses. Some of their statements are compared to known facts at the time of the crash, including the time of the accident and the weather conditions. Other facts are compared between the survivors, such as the mood of the passengers immediately post-crash. The KLM-Pan Am accident in the Canary Islands is used as the study accident. A suggestion for future use of survivors' statements is tendered.

Safety attitudes of a general aviation pilot population.

Safety attitudes were elicited by forced-choice questionnaire responses obtained from 141 general aviation pilots in Ohio. The developed questionnaire was pretested on experienced pilots. Specific attitudes in five major categories significant to flight safety were surveyed: aerodynamics, meteorology, preflight activities, flight operations, and aeromedical factors. All pilots were active members of the Dayton Pilots Club. Two levels of concern were identified through the study: the first relates to those areas that are of extreme importance to safety; the second covers items that constitute a safety hazard when combined with other factors.