MAWSON EXPEDITION.

New Zealand Herald, Volume LXVII, Issue 20623, 23 July 1930, Page 13

MAWSON EXPEDITION.

WORK OF BIOLOGI3TS—

ANTARCTIC ANIMALS

THE STUDY OF MARINE LIFE.

Ny Slit DOUGLAS MAWSON

(All rights reserved.) Xo. A".

The following arc further extracts from the report, of Professor T. Harvey Johnston, professor of zoology. University of Adelaide, and chief biologist to the expedition : Marino algae were abundant in the regions visited, the brown seaweeds being extensively developed. Among the latter in the sub-Antarctic islands were the various species of kelp, the common floating type, macrocystis, growing Upward from rocky surfaces many fathoms below the surface, commonly from depths of 10 fathoms, to form dense patches capable of hindering navigation by small boats. Some species were heavy and straplike, others narrow and greatly branching and these grew near low-tide mark. Green seaweeds were abundant on rocks between tidemarks in sheltered bays in Kerguelen. The so-called led seaweeds were common from low-tide level down to tha kelp zone.

Along the Antarctic coasts visited there was no trace of marine algae between tidemarks but both reel and brown seaweeds were abundant at depths over a fathom, the plants being rooted in the crevices between the rather closely-fitting mosaic of polished stones forming the sea floor there. This was a striking example of the effect of sea ice planing off any plant growth as it moved over the rocks, only such plants as were protected by cracks in the stones, or those growing between closely adjacent rocks being ablo to survive. Various kinds of seaweeds were found in abundance more or less embedded in the ice masses formed of frozen spray along the foreshores, having been detached and thrown up by the heavy gales. The endemic land fauna of the subAntarctic islands visited consisted, apart from the birds which are referred to elsewhere, of snails, insects, spiders, mites and earthworms, together with abundance of microscopic animals living in pools, streams, bogs and wet soil. Brilliant Land Snail,;. Small laud' snails were fairly common on all the islands, as also was a species of spider. Tiny mites, some of them brilliantly coloured, were frequently seen. Earthworms of several species were abundant wherever moisture requirements were suitable, one kind being very common along the beaches below high-tide mark in situations where fresh wa:er drainage entered the sea.

Insect life was of particular interest, as most ot the species wen; flightless. Beetles oi' several kinds were quite common. The flies were very characteristic, some being carnivorous and carrion feeders, others herbivorous ; some capable of flight, but most of them were quite wingless. Springtails, a very primitive group of apterous insects, were common, and one species formed bluish grey masses on the surface of small streams. Xo trace of animal life, apart from birds and seals, was observed, on the Antarctic- rock surfaces. The various mammals introduced into the sub-Antarctic islands, especially Kerguelen, deserve mention. Rats and mice have become very abundant and widely distributed. Rabbits have played havoc i with the vegetation, especially the Kerguelen cabbage, which has become almost, j exterminated, except on ths islands ot I Royal Sound and such other places as are j inaccessible to the rodents. Wild dogs, the progeny of animals let", by the Gams Antarctic Expedition, are now widely d:sIributed. though infrequently seen, and iliev. together with the skin- gulls, probably play a part- in controlling the rabbit. Seals and Whale:;. The marine mammals—seals and whales —inav now be referred to briefly. In the sub-Antarctic islands two kinds of seals were seen, the sea-elephant, and the sealeopard. tho former being ruthlessly hunted by scalers for the sake, of iis blubber. Their skeletons or carcases were observed along many beaches in the throo islands visited, and' a number of living animals were, seen at Heard Island and the Crozcts, but only a few isolated individuals on various beaches at Kcrguelcn, where they are now rather uncommon, whereas they occurred previously in tens of thousands along its beaches during early summer. Since the animals come ashore only for the purpose of breeding, the practice of sealers to kill all animals available irrespective of age or sex must tend toward extermination of the species. It is only on beaches inaccessible to sealers that the species has much opportunity to replenish its numbers. Their stomach contents revealed tho fact that the sea-elephant feeds on cuttlefish, no trace of fish remains being found in any oi^tlieni. The sea-leopard, which occurs as a solitary animal, was seen occasionally at. Kerguelen and Heard Island, as well as in the pack ice. The stomach contents consisted of penguins and parts of young sea-elephants. While the ship was in the pack-ice numerous crab-eating seals and at least two examples of the rare Ross seal were seen. The former species was commonly dozing on the ice, bub sometimes was observed hunting around the foot oil ice floes for its favourite food supply, enphausia, or kril, a shrimp-like crustacean on which the Adelie penguins as well as the large I whales feed.

When wo wore very close to the Antarctic coasts, Weddelt sec.ls were seen lying on the ice or swimming in search of food, fish, in their case. Species of Whales Seen.

Whales constitute a, very impoitant part of <lio sub-Antarctic and Antarctic marine fauna, and were especially looked for during the voyage.- Whaling is undertaken from certain bays an Kcrguclcn as headquarters, the chief whales taken being the blue, the finner, and the humpback', the last being captured in the early part of the. season and the first-named constituting the most important of the three. We saw a few fmuers find killers and a number of Pike whales before entering the pack-ice. The last-named became very abundant in the pack-ice. and at this time the huge blue whale--the largest member of the animal kingdombegan to make its _ appearance- lis occurrence was sporadic, though in some localities such as near Enderby Land thev were very abundant, especially along the'edge of the close pack-ice and 111 tho larger "leads in the pack. .As is well known, the prevalence of blue whales in anv locality depends on the abundance of tho particular kind of crustacean, kr:l, on which it feeds. Small Marine Organisms.

The major part of the biological work of tho expedition was concerned with plankton—that great body of organisms which drift or swim more or less lecbly in the superficial as well as flic dcepei f waters of the ocean. It is not always easy lo diaw a lino of demarcation between plankton and nekton, a term used (o include actively swimming organisms such as fish and cuttlefish which have a much great individual range of movement, and are. not so restricted to a particular environment. The remainder of marine life may bo classed as benthos, a term comprising fixed, sedentary or slowly . moving organisms associated with Ihe sea floor ue livinir between tide marks; sponges.'starfish and most molhiscs and worms tailing under this category.