MICROSCOPIC LIFE IN THE OCEAN.

Hokitika Guardian, 31 May 1924, Page 4

MICROSCOPIC LIFE IN THE OCEAN.

(liy (I. K. Sleggs? lI.Sc. in Daily Mail)

The surface wafers of the sea in all parts of the globe abound in miscroscopic floatin'; life which can he collected by towing a net of close niesli through the water; indeed, it has been said that a man on a raft with a silk liantlßerchief never need starve.

Many of the micro-organisms possess tiny shells of mineral matter, which are often very beautiful on account of their graceful outlines, the sculpturing upon the shell, or the. spines and projections which it bears to lessen the rate of sinking through the water.

Now when the micro-organisms die, their shells, which are imperishable, start upon the long, slow, downward journey. They descend gradually in the warm surface layer of water till they reach the limit of sunlight.

This is usually at a depth of a hundred fathoms, and here the water turns suddenly colder and therefore more viscous. So that the hosts of falling shell-specks are halted in their rate of tumble. This lower limit ol the twilight zone in the sea is called the mud-line, and it is a great feeding ground for the scavengers of the deep.

The myriads of shells, however, pass the mud-line and continue their laborious descent through the waters, now in darkness save for the gleams of phosphorescent light. But while they are falling, fathom after fathom, the sea water is slowly but surely dissolving their substance away. First to go are the calcareous shells (consisting of carbonate of lime). If the sea is not more than -.000 fathoms deep the calcareous shells will reach bottom safely, and, collecting in a layer there, will he preserved from further solution by those that follow.

Thus it comes about that down to a depth of 2,000 fathoms or so the great abyssal plain is covered with a grey-ish-white deposit of chalky mud, known as the globigerina ooze. The name is derived from the organism globigerina, whose shell preponderates in numbers over all others. Observations made in the work of laying and taking up cables in the Atlantic have shown that the rate of deposition of globigerina ooze may be as high as one inch in ten vears.

Then there is the radinlariaii ooze, another very important deep-sea deposit. The radiolarians have shells not of lime hut of silieia. Silieia is the substance of which sand is largely composed, and it is far more resistant to the solvent action of sen-water than is carbonate of lime.

At greater depths than 2,000 fathoms on an average (lie globigerinn shells are all dissolved before they reach the bottom, but tile radiolarians are still sinking and form radiolarian ooze in the deeper paits of the abyss. Even the glassy radiolarians are dissolved in sinking to very much greater depths, and in the deepest region of all the ocean-bed is covered with red clay in which living remains are scanty.

Other deep-sea deposits formed from the sinking of the hard shells of sur-face-living organisms are the pleropod ooze, from shells of the “sea-buTter-llios,” and the diatom ooze. In order to take a sample of the seahot loin it is merely necessary to smear the bottom of the lend with grease before hiking a sounding. Then when the lead comes up a small quantity of the bottom deposit adheres to the tallow.

Dust from deserts, powdered pmniee, volcanic and meteoric dusL, sharks’ teeth, ear-bones of whales, cosmic spherules—all contribute to the ilttslrain in the ocean dentils.