Modeling acoustic propagation of airgun array pulses recorded on tagged sperm whales (Physeter macrocephalus)

Author Posting. © Acoustical Society of America, 2006. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 120 (2006): 4100-4114, doi:10.1121/1.2359705.In 2002 and 2003, tagged sperm whales (Physeter macrocephalus) were experimentally exposed to airgun pulses in the Gulf of Mexico, with the tags providing acoustic recordings at measured ranges and depths. Ray trace and parabolic equation (PE) models provided information about sound propagation paths and accurately predicted time of arrival differences between multipath arrivals. With adequate environmental information, a broadband acoustic PE model predicted the relative levels of multipath arrivals recorded on the tagged whales. However, lack of array source signature data limited modeling of absolute received levels. Airguns produce energy primarily below 250 Hz, with spectrum levels about 20–40 dB lower at 1 kHz. Some arrivals recorded near the surface in 2002 had energy predominantly above 500 Hz; a surface duct in the 2002 sound speed profile helps explain this effect, and the beampattern of the source array also indicates an increased proportion of high-frequency sound at near-horizontal launch angles. These findings indicate that airguns sometimes expose animals to measurable sound energy above 250 Hz, and demonstrate the influences of source and environmental parameters on characteristics of received airgun pulses. The study also illustrates that on-axis source levels and simple geometric spreading inadequately describe airgun pulse propagation and the extent of exposure zones.Funding for this work was provided by the Office of Naval Research, the U.S. Department of the Interior Minerals Management Service Cooperative Agreements Nos. 1435-01-02- CA-85186 and NA87RJ0445, and the Industry Research Funding Coalition. S.L.D.R. was supported by a National Science Foundation Graduate Research Fellowship

Red Tides In the Gulf of Mexico: Where, When, and Why?

Independent data from the Gulf of Mexico are used to develop and test the hypothesis that the same sequence of physical and ecological events each year allows the toxic dinoflagellate Karenia brevis to become dominant. A phosphorus-rich nutrient supply initiates phytoplankton succession, once deposition events of Saharan iron-rich dust allow Trichodesmium blooms to utilize ubiquitous dissolved nitrogen gas within otherwise nitrogen-poor sea water. They and the co-occurring K. brevis are positioned within the bottom Ekman layers, as a consequence of their similar diel vertical migration patterns on the middle shelf. Upon onshore upwelling of these near-bottom seed populations to CDOM-rich surface waters of coastal regions, light-inhibition of the small red tide of similar to 1 ug chl l(-1) of ichthytoxic K. brevis is alleviated. Thence, dead fish serve as a supplementary nutrient source, yielding large, self-shaded red tides of similar to 10 ug chl l(-1). The source of phosphorus is mainly of fossil origin off west Florida, where past nutrient additions from the eutrophied Lake Okeechobee had minimal impact. In contrast, the P-sources are of mainly anthropogenic origin off Texas, since both the nutrient loadings of Mississippi River and the spatial extent of the downstream red tides have increased over the last 100 years. During the past century and particularly within the last decade, previously cryptic Karenia spp. have caused toxic red tides in similar coastal habitats of other western boundary currents off Japan, China, New Zealand, Australia, and South Africa, downstream of the Gobi, Simpson, Great Western, and Kalahari Deserts, in a global response to both desertification and eutrophication

Biosynthetic Gene Cluster for the Cladoniamides, Bis-Indoles with a Rearranged Scaffold

The cladoniamides are bis-indole alkaloids isolated from Streptomyces uncialis, a lichen-associated actinomycete strain. The cladoniamides have an unusual, indenotryptoline structure rarely observed among bis-indole alkaloids. I report here the isolation, sequencing, and annotation of the cladoniamide biosynthetic gene cluster and compare it to the recently published gene cluster for BE-54017, a closely related indenotryptoline natural product. The cladoniamide gene cluster differs from the BE-54017 gene cluster in gene organization and in the absence of one N-methyltransferase gene but otherwise contains close homologs to all genes in the BE-54017 cluster. Both gene clusters encode enzymes needed for the construction of an indolocarbazole core, as well as flavin-dependent enzymes putatively involved in generating the indenotryptoline scaffold from an indolocarbazole. These two bis-indolic gene clusters exemplify the diversity of biosynthetic routes that begin from the oxidative dimerization of two molecules of l-tryptophan, highlight enzymes for further study, and provide new opportunities for combinatorial engineering

Estimation of Lower and Upper Bounds on the Power Consumption from Scheduled Data Flow Graphs

In this paper, we present an approach for the calculation of lower and upper bounds on the power consumption of data path resources like functional units, registers, I/O ports, and busses from scheduled data flow graphs executing a specified input data stream. The low power allocation and binding problem is formulated. First, it is shown that this problem without constraining the number of resources can be relaxed to the bipartite weighted matching problem which is solvable in O(n)/sup 3/. n is the number of arithmetic operations, variables, I/O-access or bus-access operations which have to be bound to data path resources. In a second step we demonstrate that the relaxation can be efficiently extended by including Lagrange multipliers in the problem formulation to handle a resource constraint. The estimated bounds take into account the effects of resource sharing. The technique can be used, for example, to prune the design space in high-level synthesis for low power before the allocation and binding of the resources. The application of the technique on benchmarks with real application input data shows the tightness of the bounds

Texas-Louisiana Shelf Circulation and Transport Processes Study: Synthesis Report, Volume 2. Appendices

A report presenting the results of Study Unit A of the Texas-Louisiana Shelf Circulation and Transport Processes Study

Texas-Louisiana Shelf Circulation and Transport Processes Study: Synthesis Report, Volume 1. Technical Report

A report presenting the results of Study Unit A of the Texas-Louisiana Shelf Circulation and Transport Processes Study

Eddy Forced Variations in On-And Off-Margin Summertime Circulation along the 1000-M Isobath of the Northern Gulf of Mexico, 2000-2003, and Links with Sperm Whale Distributions along the Middle Slope

In summers 2000-2003, NOAA Ship Gordon Gunter and TAMU R/V Gyre dropped XBTs and logged ADCP data while carrying out visual and passiveacoustic surveys for sperm whales along the 1000-m isobath of the northern Gulf of Mexico. The ships also made CTD casts, particularly when/where the XBT and ADCP data indicated the ships were passing into or out of anticyclonic and/or cyclonic slope eddies. The fine-scale resolution of the ship surveys, when combined with the meso-scale resolution of remote sensing surveys of sea surface height and ocean color, document the summer-to-summer variability in the intensity and geographic location of Loop Current eddies, warm slope eddies, and areas of cyclonic circulation over this middle slope region of the northern Gulf of Mexico. These variations forced striking year-to-year differences in the locations along the 1000-m isobath where there was on-margin and off-margin flow, and in locations where sperm whales were encountered along the 1000-m isobath. For example, when there was on-margin flow into the Mississippi Canyon region in early summer 2003, sperm whales were very rarely seen or heard there. In contrast, later that summer and during other summers when flow was along-margin or off-margin there, sperm whales were locally abundant. In this report we describe how eddy-forced variations in on-margin and off-margin flow changed the meso-scale circulation along the 1000-m isobath, and we show that most sperm whales were encountered in regions of negative SSH and/or higher-than-average surface chlorophyll