OS31B-0404
Spatial and temporal behavior and acute ecotoxicological effects of Tributyltin (TBT) on coral reef and adjacent ecosystems around Okinawa Island, Japan.
Spatial and temporal behavior of the tributyl tin (TBT) were investigated in the coastal areas around Okinawa Island, Japan. A seasonal monitoring study was conducted between February and October 2006. The effects of TBT on the carbon metabolisms (net production and calcification) on the intact coral-alga association Galaxea fascicularis were also investigated. Mean concentration of TBT (2.45 ng/L) found in the Manko estuary waters have exceeded some international permissible targets of waters quality guideline for TBT (1ng/L). The sediments in Manko estuary sediments can be considered lightly contaminated (0-20 ng/g dw) and Okukubi estuary as uncontaminated (below 3ng/g dw) with TBT. The seasonal concentration pattern of TBT at the Manko estuary was autumn > spring > summer > winter. The acute ecotoxicological results show that the photosynthesis rate and calcification rate were significantly reduced by 78 % and 72 % relative to the control (ANOVA, p<0.001) when corals were exposed to 5000 ng/LTBT, respectively. No significant effects (ANOVA, p>0.05) were observed when corals were exposed to 1000 ng/LTBT. The present study reports the occurrence and continuous input of TBT in the coastal areas around Okinawa Island, even 16 years after legal restriction of TBT usage in coastal waters was implemented by the Japanese Environmental Authorities. However, the nominal sensitive concentration of TBT that causes alteration of carbon metabolisms of coral within 96 hrs exposure are much higher than those recently found in the coral reef waters and adjacent ecosystems.
OS31B-0405
Insights into the problems of communicating tsunami warnings and tsunami awareness education from decision loop analysis of behavior during the 2004 Indian Ocean tsunami
Decision loop analysis allows us to interpret video and photograph evidence of the behavior of people in Sumatra, Thailand and Sri Lanka during the 2004 Indian Ocean earthquake and tsunami, and to identify problems in communication of tsunami warnings to the general population. Decision loop analysis identifies four steps in the response to a threat: observation (of warning signs); orientation (recognition of the significance of those warning signs); decision (on what response to make); action (implementation of that response). In the case of the Indian Ocean tsunami, lack of tsunami awareness generally caused the decision loop to break down at the orientation stage, even where observation of the incoming waves was reinforced by shouted warnings. Where the orientation step was made early, evacuations were often successful. In the zone of strongest felt seismic intensity the population was subject to information overload (even though damage was often limited) and spent the time between the earthquake and the arrival of the tsunami responding to the earthquake: this "blitzkrieg" effect is a significant obstacle to near – source tsunami mitigation. In other cases, the loop broke down at the decision stage: frequently fatal decisions about where to go emphasize the need for clearly signposted tsunami evacuation routes. Decision loop analysis therefore highlights the different components needed in Education for Self Warning and Voluntary Evacuation (ESWAVE) as part of tsunami mitigation. The abundant video and photograph recordings of the 2004 tsunami provide much material for this approach, similar to the films of volcanic eruptions by Maurice and Katia Krafft that have been used to raise awareness of volcanic hazards after the 1985 Armero lahar disaster.
OS31B-0406
Pacific Basin Tsunami Hazards Associated with Mass Flows in the Aleutian Islands of Alaska
The Aleutian Islands are a chain of volcanic islands formed by an intra-oceanic subduction zone. This area consists of a submerged chain of mountains, volcanic islands, and submarine canyons, surrounded by a low- relief continental shelf above about 1000-2000 m water depth. Part of the island chain is fragmented into a series of fault-bounded blocks, tens to hundreds of km in length, and separated from one another by distinctive fault- controlled canyons that are roughly normal to the arc axis. The canyons are geomorphically low areas between the higher relief blocks and are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. The physical setting of the Aleutian Islands indicates that mass flows of unconsolidated debris that originate either as submarine mass flows or as subaerial debris avalanches entering the sea may be potential tsunami sources. Large scale mass-flow deposits have not been identified on the seafloor south of the Aleutian Islands, primarily because the area has never been mapped or examined at the resolution required to identify such features. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. We suggest that tsunamigenic mass flows are a plausible geologic process in the Aleutian Islands and that the tsunamis produced by such flows may be large enough to cross the Pacific Ocean basin. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides. The flows have lengths that range from 40-80 km, maximum thicknesses of 400-800 m, and maximum widths of 10-40 km. Although some of these hypothetical flows are large, they are not unprecedented and flows of similar dimensions are known in other continental slope settings. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible submarine mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large tsunamis. These waves may be several meters in amplitude at distal locations, such as Japan, Hawaii, and along the South American coastline where they would constitute significant hazards.
OS31B-0407
The Role of High Sedimentation Rates on the Development of Pore Pressure and the Consequences for Slope Stability
Mass transport deposits (MTD) and slides are common features of the Earth's continental slopes. The MTDs are often associated with deposition during sea level low stands, especially during the regressive phase of the sea level cycle. These are periods when sediment transport across the shelf to the slope is at a maximum. We will here present the results of numerical models that use geotechnical sediment properties and sedimentation history to predict pore pressure profiles from both areas with recent rapid deposition and areas where rapid deposition occurred during the low sea level stand associated with the last glacial period. We will use these results to show how the sedimentation history can influence the strength of the sediments and consequently the region's slope stability. The models show that deeply buried sediments are influenced by the long term average sedimentation rate, whereas the shallow deposits reflect recent depositional history. Whereas the latter may influence stability of local slopes, the former provides pore pressure gradients that can set up fluid flow on a more regional scale. Such fluid flow in the deeper parts of the Storegga region is thought to have triggered the Storegga Slide. The pressurization can also lead to hole collapse and shallow water flow during drilling operations.
OS31B-0408
The Dispersal and Persistence of Invasive Marine Species
The spread of invasive marine species is a continuing problem throughout the world, though not entirely understood. Why do some species invade more easily than the rest? How are the range limits of these species set? Recent research (Byers & Pringle 2006, Pringle & Wares 2007) has produced retention criteria that determine whether a coastal species with a benthic adult stage and planktonic larvae can be retained within its range and invade in the direction opposite that of the mean current experienced by the larvae (i.e. upstream). These results however, are only accurate for Gaussian dispersal kernels. For kernels whose kurtosis differs from a Gaussian's, the retention criteria becomes increasingly inaccurate as the mean current increases. Using recent results of Lutscher (2006), we find an improved retention criterion which is much more accurate for non- Gaussian dispersal kernels. The importance of considering non-Gaussian kernels is illustrated for a number of commonly used dispersal kernels, and the relevance of these calculations is illustrated by considering the northward limit of invasion of Hemigrapsus sanguineus, an important invader in the Gulf of Maine.
OS31B-0409
Small Scale Characterization of the Presence of the Explosive Octahydro-1,3,5,7-tetranitro- 1,3,5,7 tetrazocine (HMX) Near Former Naval Sites on Vieques Island, Puerto Rico
Octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (HMX) is a synthetic energetic compounds that has been commonly used in military munitions. The presence and movement of HMX through the environment is of growing concern because of potential civilian exposure and impacts on human health. HMX remains in the environment unreactive with little degradation. It can be transported great distances in water thus having the possibility for migrating into groundwater. The former naval sites in Vieques were used for weapons training and housed several disposal sites. Previous studies around these sites indicate the presence of radioactive materials produced through thermal fission, such as Cs-137. Since HMX was primarily used to implode fissionable materials in nuclear devices, evaluating the release of HMX and consequent movement through the environment at these sites is essential. Surface water and soil samples as well as core and pore water samples were collected from two sites in Vieques; Kiani Lagoon and Mosquito Bay. All samples were extracted using EPA method 8330 and analyzed using RP-HPLC analysis with a C-18 column. HMX was undetected in samples collected from both Kiani Lagoon and Mosquito Bay. The development of a model that studies the flow rates and fate of water runoff in these areas of interest, coupled with data on groundwater testing inside the actual former naval facilities, is being explored for further sample collection and analysis.
OS31B-0410
Field Characterization for Remediation of Trinitrotoluene in Sediment and Water from Vieques, Puerto Rico
2,4,6-Trinitrotoluene (TNT) is an explosive used in military shells, bombs, and grenades, industrial applications, and underwater blasting. The explosive itself, some of its degradation and transformation products, and any manufacturing impurities or by-products are all considered serious environmental contaminants with potential harmful and toxic effects on animals, plants and humans. In Vieques, Puerto Rico, The Atlantic Fleet Weapons Training Area consists of areas and nearby waters that have become contaminated primarily by United States Department of Defense (DoD) activities. Known areas of concern include waters influenced by target practice off the eastern shores of Vieques, areas where ships were anchored north of Vieques, and waters near the western side of Vieques, including Mosquito Pier. Detection and remediation of TNT in these areas is necessary to protect the health and welfare of the present and future Vieques residents and visitors. This work examines the distribution of TNT at specific locations in Vieques. Samples were collected from Mosquito Bay which is located in the watershed between the residential and naval sections of Vieques and also in a northern section of the island at Kiani Lagoon. In addition to Vieques sediment studies, the use of zero-valent iron (ZVI) to degrade trinitrotoluene was examined. The ultimate focus is on emulsifying ZVI particles that are capable of promoting rapid and complete degradation of TNT molecules. ZVI has demonstrated effective degradation of TNT, however, these particles by themselves have significant problems in treating sorbed phase TNT. Results from these studies will be presented.
OS31B-0411
Climatic and Tectonic Signals in Turbidite Systems off Western North America
Turbidite systems (deep-sea channels, submarine fans, base-of-slope aprons) in the northern Cascadia Basin contain a synchronous Holocene (past 10,000 cal. yr. BP.) record of ~18 turbidites. These turbidites were triggered with an average frequency of 550 yr by great earthquakes (8-9 Mw) on the Cascadia Subduction Zone. Greater magnitude of events is shown by thicker turbidites. Similarly, along the northern California continental margin, Holocene turbidites have been triggered every 200 yr on average by great earthquakes (ca. 8 Mw) associated with the San Andreas Fault. The paleoseismic turbidite record on both margins proves the dominant tectonic control for triggering turbidity currents on these active margins. In contrast, the control of turbidite system growth by climatic change and lower sea level during the late Pleistocene is shown in Cascadia Basin by 1) the order of magnitude greater average sedimentation rates (100 plus cm/ka Pleistocene, 2) bypassing of sediment to outer fan unconfined depocenters, 3) high sand:shale ratios (1:1 to 3:1 Pleistocene), and thick sand turbidites (ca. 10-40 cm Pleistocene). After a rapid deglaciation and sea level rise from ca.13-14,000 yr B.P., turbidites became finer-grained silt and mud beds that were mainly confined to channels, whereas other Cascadia Basin interchannel areas were covered by a hemipelagic sediment drape with a basal age of 12,750 cal yr BP.