Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Gas Transport in the Marsh Grass, Spartina alterniflora

Abstract: Spartina plants have continuous gas spaces from the leaves to the tips of the roots. Oxygen values in the roots are as low as 3 per cent and increase toward the stem. Carbon dioxide values are highest in the rhizome and decrease up the stem and toward the root tips. Oxygen and carbon dioxide moved through the plants at equal rates for equal gradients, and these rates agree with measurements made on plants in the marsh. Calculated oxygen and carbon dioxide fluxes for the observed gradients in the observed gas spaces agreed with measured fluxes. We conclude that gases move in and out of Spartina roots by diffusion through uninter rupted gas spaces within the plant.

Biosonar performance of foraging beaked whales (Mesoplodon densirostris).

Abstract: SUMMARY Toothed whales ( Cetacea, odontoceti ) emit sound pulses to probe their surroundings by active echolocation. Non-invasive, acoustic Dtags were placed on deep-diving Blainville9s beaked whales ( Mesoplodon densirostris ) to record their ultrasonic clicks and the returning echoes from prey items, providing a unique view on how a whale operates its biosonar during foraging in the wild. The process of echolocation during prey capture in this species can be divided into search, approach and terminal phases, as in echolocating bats. The approach phase, defined by the onset of detectable echoes recorded on the tag for click sequences terminated by a buzz, has interclick intervals (ICI) of 300-400 ms. These ICIs are more than a magnitude longer than the decreasing two-way travel time to the targets, showing that ICIs are not given by the two-way-travel times plus a fixed, short lag time. During the approach phase, the received echo energy increases by 10.4(±2) dB when the target range is halved, demonstrating that the whales do not employ range-compensating gain control of the transmitter, as has been implicated for some bats and dolphins. The terminal/buzz phase with ICIs of around 10 ms is initiated when one or more targets are within approximately a body length of the whale (2-5 m), so that strong echo returns in the approach phase are traded for rapid updates in the terminal phase. It is suggested that stable ICIs in the search and approach phases facilitate auditory scene analysis in a complex multi-target environment, and that a concomitant low click rate allows the whales to maintain high sound pressure outputs for prey detection and discrimination with a pneumatically driven, bi-modal sound generator.

Advances in Estuarine Physics

Abstract: Recent advances in our understanding of estuarine circulation and salinity structure are reviewed. We focus on well- and partially mixed systems that are long relative to the tidal excursion. Dynamics of the coupled system of width- and tidally averaged momentum and salt equations are now better understood owing to the development of simple numerical solution techniques. These have led to a greater appreciation of the key role played by the time dependency of the length of the salt intrusion. Improved realism in simplified tidally averaged physics has been driven by simultaneous advances in our understanding of the detailed dynamics within the tidal cycle and across irregular channel cross-sections. The complex interactions of turbulence, stratification, and advection are now understood well enough to motivate a new generation of physically plausible mixing parameterizations for the tidally averaged equations.