Deep Sea Research (1953)最新文献

The Costeau's ‘diving saucer’ is now ready for diving down to 900ft. The first scientific dive in Ajaccio Bays has given the opportunity of a short account on the vertical distribution of animals and algae, both on rocky and soft bottoms from 15 fathoms down to 100 fathoms deep. The engine seems easy to drive and allows observations on substratum at a very short distance if necessary; its speed is adequate for a quick survey of a large area of bottom where the flora and fauna are well known. The diving saucer seems less adequate for plankton investigations.

Chemical and hydrographic observations were made on five north-south sections along the Caribbean coast of Venezuela in October and November, 1958. In addition, 15 stations were occupied in the Gulf of Cariaco. Chemical determinations included dissolved oxygen, total and inorganic phosphorus, nitrate, silicate and, in the anaeric waters of the Gulf of Cariaco and the Cariaco Trench, hydrogen sulphide.

Except for some low-salinity near-surface water, these waters frrm a single mass, on the basis of the temperature-salinity diagram, in agreement with the findings of Parr (1937). Minimu salinities are found at 700–800 m and can be attributed to Antarctic Intermediate sources. Maximum salinities are in the upper 200 m, at depths which increase to the north.

Near the coats, isopleths of salinity, temperature, density and the nutrient ions generally slope upward toward the south, particularly in the eastern sections. This is interpreted as evidence of upwelling along this coast, a phenomenon which appears to be the only important source of nutrients in the photic zone, and which accounts for the high biological productivity of the region.

The Gulf of Cariaco was filled with nearly isohaline water having the same temperature correlations as the Caribbean water outside at the time of the observations. Upwelling at the eastern end of the Gulf is clearly evident from the temperature, oxygen and nutrient distributions. The water deeper than about 54 m is isolated from, and is colder than, water at equal depths outside. Past observations indicate that this deep water may be renewed some (and possibly all) years, in February. These deep waters are isolated, vertically, by a sharp temperature gradient, as stagnant, and contain sulphides. The upwelling in the east results in high biological productivity in the region, which is evident from the rich flora and fauna.

An estimate of the productivity of the region has been made from the fixation of phosphate-phosphorous which upwells near the coast, north of Puerto La Cruz. The calculation indicates a production of 0·14 gm C/m²/day, a figur which is consistent with estimates made in the region by other methods. An estimate made in the Gulf of Cariaco, also on the basis of the fixation of inorganic phosphate, indicated a daily production of 2·8 to 5·7 gm C/m².

An elongated seamount rising to 678 fathoms was surveyed by echo-sounding, dredging, photography, magnetic and seismic methods, the results of which are described. The feature appears to be the result of volcanic extrusion along a fault running obliquely across a broad rise.

A system of channels connecting the Biscay and Iberia plains was discovered in 1958. Two main channels cut through the sill and join after 20 miles. The total length between plains is 50 miles and the width of the channels varies from 2 to 10 miles. The change of level between plains occurs where the channel first leaves the upper plain. The channel shows a meander formation similar to a subaerial river. Cores show that turbidity currents have been active in the past. Small feeding channels on the Biscay plain converge on the interplain channels.

It is concluded that turbidity currents initiated on the continental shelves and flowing across the Biscay plain can be rejuvenated by the increase in gradient and lateral constriction, and flow through to the Iberia plain where they finally deposit their load.

This report describes a deep, telemetering hydrophone which transmits its information acoustically through the water to a surface vessel. The instrument has the advantage of requiring no electrical cable to the ship and, being self-contained, may be quickly hung on any suitable supporting line or wire. Alternatively, any type of inexpensive single-conductor cable of sufficient strength, such as oil-well logging cable, may be used to replace the acoustic link for some purposes if desired.