Composition,export and faunal utilization of drift vegetation in the salt river submarine canyon

Submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water. We studied the composition, export, and faunal utilization of shallow, nearshore benthic vegetation as it was transported to offshore areas via the Salt River submarine canyon on the island of St Croix, U.S. Virgin Islands. The study was conducted using a saturation diving system (NULS-1: Hydrolab) during two missions in April and August, 1980. Using bottom drifters deployed in Salt River Bay and the submarine canyon, we recorded net benthic current flow up to 2 cm s^?1 moving out of the lagoon and down the canyon to deeper water. Using bottom nets set up at the canyon head and at the 29 m isobar, and from transect surveys and drift clump samples, we determined drift plant export rates and drift clump biomass and species composition. The dominant drift plants were Thalassia testudinum and Syringodium filiforme and algae in the genera Dictyota, Dictyopterus, and Diloplus. During the second mission, the seagrass Halophila decipiens became more abundant, both in the drift and in large patches along the canyon floor. In both missions, more drift was collected in the nets during high wind conditions than during calmer days. Calculated turnover times ranged from 0·01 to 4·4 days for algae in the order Dictyotales and 4·4 to 18 days for Thalassia blades. Total exported biomass of drift vegetation varied between 1·4 to 65·1 kg wet wt day^?1. Samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes, but in relatively low numbers. Faunal numbers were most strongly related to rate of drift movement.     

New techniques in rock mass classification: application to welded tuffs at the Nevada Yucca Mountain

Summary Many rock mass classification systems exist to assist the engineer in assessing the rock support requirements for underground design. On-going research in this area is directed at attempting to utilize the fractal dimension and the acoustic emission response of the tuffs at the Nevada Yucca Mountain to further aid in rock mass classification. Acoustic emission response is shown to be correlated with the porosity of the sample. Engineering behaviour of the rock varies dramatically with porosity; events and peak amplitude offer a means to distinguish between fracture porosity and pore porosity and consequently the engineering behaviour of the rock. Fractal dimension is used to characterize the roughness of fracture surfaces. Two fractal dimension calculation methods, one based on the semi-variogram for the surface and the other based on the use of dividers, are applied for this purpose. The divider method is shown to resolve deviation from a straight line; the semi-variogram method is shown to identify statistical similarity to various types of noise.Nomenclature D fractal dimension - AE acoustic emission - b b-value determined from log(frequency) against log(amplitude) plots - (h) semi-variogram function - h lag distance for semi-variogram function - H an exponent term related to fractal dimension asD=2 –H     

Freshwater inflow: Science, policy, management

The papers in this special issue were presented in a special session during the 2001 biennial conference of the Estuarine Research Federation held in St. Pete Beach, Florida. The session, “Freshwater inflow: Science, policy and management,” was focused on issues related to reduced freshwater inflow to estuaries. The session brought together scientists, managers, and regulators, and included presentations on the estimation of freshwater input to estuaries, development of ecological indicators to assess changes in inflow, management strategies used to set freshwater requirements, and experiences with the reintroduction of freshwater to restore inflow.     

Real-Time GPS Data Transmission Using VSAT Technology

The University NAVSTAR Consortium (UNAVCO) Boulder Facility is assessing Very Small Aperture Terminal (VSAT) technology for near real-time transmission of GPS data from a remote receiver to a central processing facility. The study is motivated by the need for a robust, cost-effective data communications solutions to transfer GPS data from remote sites where no other communication alternatives exist. Future large-scale plate boundary deformation initiatives using spatially dense networks of GPS will require receivers to be located where the science dictates, and not the power or communications infrastructure. For other applications, such as determining rapid GPS orbits and time transfer, there is a push toward reducing the latency in GPS data used to produce GPS data products and differential corrections (Talaya & Bosch, 1999; Jackson, Meertens, & Rocken, 2000; Muellerschoen, Bar-Sever, Bertiger, & Stowers, 2001), and to support upcoming Low Earth Orbiting (LEO) missions requiring low latency, 1-s GPS data. In this paper we evaluate two Ku-band systems, the Nanometrics Libra VSAT and the StarBand 2-way satellite Internet VSAT. The Nanometrics system test results show that continuous, 1-s GPS data can be streamed from multiple remote stations within the VSAT footprint, quality checked, and delivered for processing with a <2.5-s latency (mean 1.2 s) and a 99.8% reliability. Benefits of the Nanometrics system include global coverage, control of bandwidth allocation and data hub, and the low power draw of the system. Negatives include the cost of hub and remote infrastructure and the need to negotiate landing rights issues on a country-by-country basis. The UNAVCO Facility currently operates a Nanometrics hub and three remote VSAT systems. The StarBand system showed 98.9% reliability with a maximum latency of 10.2 s (mean latency 1.7 s) for 1-Hz GPS data and an average uplink speed of 31.7 kbps. Benefits of the StarBand system include the cost and small profile of the remote antenna. Negatives include coverage limited to coterminous United States and the high power draw of remote systems. ? 2002 Wiley Periodicals, Inc.     

Ocean dumping of seafood wastes in the United States

In the United States fish wastes can be ocean dumped without an Ocean Dumping Permit if the wastes contain no additives (flocculating or preserving agents, etc.). Fish wastes are currently ocean dumped off American Samoa, Louisiana and Puerto Rico. Fish wastes are characteristically high in proteins, fats, dissolved and suspended organic materials. Water quality parameters affected by these wastes are biochemical oxygen demand, total dissolved solids, chemical oxygen demand, oil and grease, pH, and turbidity. Other key factors include organic and nutrient enrichment, the attractant of undesirable predator species (i.e. sharks) and the natural oxygen regeneration processes.     

The organochlorine contamination history of the Mersey estuary, UK, revealed by analysis of sediment cores from salt marshes

Sediment profiles in the Banks, Ince and Widnes Warth salt marshes in Northwest England contain a mappable record of historic pollution. For persistent organochlorine compounds this stretches back over 90 years. The PCB and HCH profiles can be successfully rationalised by dating methods, and they can be related to the dates of initial production and subsequent withdrawal from use of these chemicals as a result of restrictive environmental legislation. HCB has a more complex pollution profile as it has been manufactured in Northwest England, both deliberately as a pesticide and accidentally as a by-product of several chlorination processes, dating back to the start of the 20th century. The concentrations of degradation products of DDT are relatively constant through the sediment profile and are dominated by op'- and pp'-DDD with only minor contributions from the most toxic species, pp'-DDT. The quantities of these compounds resident in the reservoir of pollutants under these marshes have been calculated, and have fallen progressively in the last 30-50 years.