Bioenhancement of cadmium transfer along a multi-level food chain

Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus.     

Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific

A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.     

The sea as a source of atmospheric phosphorus

The geochemical fractionation of phosphorus on the drop produced by bubbles bursting in seawater has been studied using a field sampling system called the Bubble Interfacial Microlayer Sampler (BIMS). The droplets from bursting bubbles were collected on filter samples in Narragansett Bay, Rhode Island during the summer of 1975. Phosphorus was found to be fractionated by the bubble-bursting process. The enrichment factor ranged from 4 to 170. Enrichment was found to increase with decreasing phosphorus concentration at 20 cm depth while it decreases with increasing wind velocity. Enrichment was independent of bubbling depth. Together these facts suggest that the sea-surface microlayer is the source of the phosphorus on the ejected drops. Organic phosphorus on the filter samples was found to be enriched relative to surface-water phosphorus by factors of 100–200, while reactive phosphorus was enriched by factors of only 6–8. This suggests that surface-active organic phosphorus compounds are the source phosphorus in the microlayer.The organic phosphorus content of samples of atmospheric particulates collected over the phosphate-rich upwelling waters near the Peru coast was found to correlate significantly with sea-salt sodium. Enrichments calculated using the average phosphorus concentration of the surface water in this area agree well with the results of the BIMS study. Thus it appears that phosphorus fractionation does occur in nature and may be important in supplying this nutrient to some coastal regions of the world.     

The role of overwash in the evolution of mixing zone morphology within barrier islands

Overwash is a major controlling factor in the morphology of the mixing zone of coastal aquifers. Conceptual models of the mixing zone describe an interface controlled by tidal oscillations, wave run-up, and other factors; however, few describe the influence of large storm events. In August 1993, Hatteras Island, North Carolina, USA, experienced a 3-m storm surge due to Hurricane Emily. Sound-side flooding infiltrated a wellfield, causing a dramatic increase in TDS levels that persisted for more than 3 years. Two-dimensional simulations with SUTRA, the USGS finite-element model, are calibrated to the TDS breakthrough data of this storm to infer model dispersivity values. Simulations using the calibrated dispersivity values, predicted flooding levels, and 54 years of hurricane records to determine the influence of the overwash events suggest that it is rare for the mixing zone to approximate the conceptual morphology. Even during quiescent periods such as between 1965 and 1975, TDS levels do not return to theoretical levels before being elevated by a subsequent storm event. Thus, while tidal oscillations and other factors are important to mixing zone development, basic wind events and more severe storm events may have more influence and lasting effect on the morphology of the mixing zone.     

Lidar observations of turbulent vortex shedding by an isolated topographic feature

Scanning measurements by a single wavelength lidar (1.06 m) were made downwind of the Pt. Sur rock, an isolated hill (height 110 m) along the California coast. Turbulent eddies (approximate diameter 50 m) were observed detaching from a stationary aerosol feature above the rock and moving downwind. Under conditions with a high Froude number [1.8], the Strouhal number [0.22] of vortex shedding was close to that observed in tank experiments with a Reynolds number of 200.