Ecology of Skeletal Plankton - Amazon S3 · 2011-05-06 · Ecology of Skeletal Plankton NORMAN S....

used for a 3-day, 200-mile excursion into the Straitof Magellan, where hand trawling yielded a numberof populations. Fishermen from the Punta Arenasarea supplied specimens from depths of 8 to 45fathoms.

Aboard Eltanin, experiments on heat- and flow-rate in brachiopods were unsuccessful because ofdifficulties with the equipment. The engineeringdifficulties are being corrected so that subsequentstudies made in the ship's laboratories are likely tobe successful. Linear measurements of the valveswere made as the brachiopods were collected.

Living animals were shipped, in plastic bags ininsulated ice chests, to the University of Pitts-burgh. Ninety-five percent of the animals survivedthe journey. The brachiopods are kept in circulat-ing seawater at 2°, 40, and 6°C. Some of theanimals show growth around mantle margins. Forexample, individuals of Terebratella dorsata aver-aged three mm. in four months; Magellania venosahave grown two mm. in the same time. Many speci-mens have ripe gonads, allowing study of the re-productive picture. Studies on larval settlementwill be made as the material warrants.

Data have been obtained on rate and rhythmicityof current flow at 2° and 7°C. with the aid of anelectrode flowmeter especially constructed for thisstudy. It is hoped that the principles of construc-tion in this flowmeter can be utilized for flowmeasurements in other filter feeders and for slow-moving water currents.

The populations collected have been analyzedto determine the parameters which reflect environ-mental effects, and those which reflect the inherentgrowth pattern of a species. The most abundantspecies, M. venosa, has shown a distinct changein width-length relation with depth, while the thick-ness-length relation remains constant within statisti-cal limits. Frequency distributions of M. venosaindicate that the species is a seasonal breeder.

Interior of Ma gellania venosa (Solander), .Showing Lop/ia-phore in the Brachial Valve and Mantle Canal SystemContaining Ripe Gonads in the Pedicle Valve. Length ofShell 6.2 cm.

Ecology of Skeletal Plankton

NORMAN S. HILLMANLamont Geological Observatory

Columbia University

The Lamont antarctic plankton program wasinitiated with Eltanin Cruise 8. Daily plankton sta-tions have been attempted. The sampling equip-ment consists of an opening-and-closing MultiplePlankton Sampler (MPS), which collects separateplankton samples at three discrete depths-500-250 meters, 250-100 meters, and 100-0 meters—during an oblique tow. A pressure-sensitive pistoncontrols the opening and closing device. Also usedis a Bathypelagic Plankton Sampler (BPS), similarto the MPS but calibrated to sample from 1,000-500 meters. Beginning with Cruise 15, a secondBPS was added to sample from 2,000-1,000 meters.Vertical and oblique hauls were taken in poorweather with a simpler net when the MPS andBPS could not be used. Surface samples (0-10meters) were also collected. Nanoplankton sampleswere obtained using millipore filter techniques.

Over 1,800 plankton samples have been col-lected from Eltanin Cruises 8 through 21, coveringmost of the southern South Pacific and the ScotiaSea area.

The plankton groups studied by Lamont person-nel are: Foraminifera, A. W. H. Be and C. Chen;Pteropoda, C. Chen; pelagic Ostracoda, N. S. Hill-man; and Coccolithophoridae, A. McIntyre. One-half of each plankton sample has been made avail-able to the Smithsonian Oceanographic SortingCenter for sorting into taxa and distribution tospecialists throughout the world.

It has been found that several species of ant-arctic Foraminifera and Pteropoda may be usedas possible indicators of water masses. These twogroups fall into three natural faunal zones: ant-arctic, transitional, and subantarctic. The transi-tional zone roughly straddles the Antarctic Con-vergence.

The Antarctic Convergence appears to be re-lated to a distributional decline of both antarcticand subantarctic Ostracoda, i.e., several antarcticspecies decline rapidly or begin to decline justnorth of the Convergence, and subantarctic speciesdecline similarly south of the Convergence. Thedepth layer most favorable to large numbers ofostracods is 100-250 meters, although a greater di-versity of species occurs below this depth.

214 ANTARCTIC JOURNAL

In a belt extending from the Convergence to 3-5latitude degrees south of the Convergence, there isa monospecific flora of Coccolithus huxleyi. Insubantarctic waters, the flora grades from two speciesnear the Convergence (C. huxleyi and C. leptoporus)to a more diverse flora representing warmer watertypes.

Biological Productivityof Antarctic and Subantarctic Waters

SAYED Z. EL-SAYEDDepartment of Oceanography

Texas A &M University

A program to study the biological productivityof subantarctic and antarctic waters in the At-lantic sector was initiated a few years ago byTexas A&M University with the cooperation ofthe Argentine Navy. In the course of this investiga -tion, primary organic production and standingcrop of phytoplankton were estimated during ninecruises along the Argentine continental shelf southof Tierra del Fuego, the Drake Passage, the Brans-field and Gerlache Straits, and the Weddell andBellingshausen Seas. In 1965, a similar programwas undertaken in the Pacific sector of Antarcticafrom aboard USNS Eltanin. Stations occupiedduring a total of 13 cruises are shown in fig. 1.

'ANTARCTIC ;/ JCRUISE CRUISE2 ., ..',....CRUISE 3 ..CRUISE

.CRUISE 5CRUISE 6• CRUISE7 .... ,. .CRUISE 8 .: •

• CRUISE9 . .. .,..

ELTANIN .....-..CRUISEIS -... ..CRUISE 19CRUISE 20.. ,CRUISE21..

S

I(''I+

Fig. 1.

The main objectives of this investigation are tomeasure primary production (by the C 14 uptakemethod) and the standing crop of phytoplankton(using chlorophyll-a) at different depths; studythe distribution and concentration of soluble andparticulate organic carbon in antarctic and sub-

antarctic waters; measure the amount of incidentsolar radiation throughout the cruises, as well assubmarine light intensity at stations occupied atlocal apparent noon; study the species of phyto-plankton which contribute to the bulk of the plantbiomass; investigate the effect of certain chemicaland physical parameters on phytoplankton produc-tion in antarctic and subantarctic waters, with spe-cial attention to the distribution and concentrationof the nutrient salts; and collect zooplanktonsamples at surface and subsurface levels in orderto study the phytoplankton-zooplankton relation-ship in the study areas.

Analysis of the data collected aboard Eltaninis still under way. Productivity data collectedfrom the Atlantic sector of Antarctica show con-spicuous regional as well as seasonal variations.Productivity values off the Argentine coast ex-hibit a high degree of variability related to thecomplexity of the different water masses in thatregion. High productivity of the waters off north-ern Argentina is related to the phenomenon ofupwelling.

Discernible latitudinal variations in productivityoccur in the Atlantic sector of Antarctica, withthe regions between 40°-45°S. and 600650S. show-ing the richest phytoplankton of all the areas in-vestigated.

Striking differences in the productivity valueshave been found between the coastal (inshore)and open, oceanic regions (offshore). In the ant-arctic waters, the chlorophyll—a content and C14

uptake in surface water samples are five timesas high for the inshore as for the offshore waters.The integrated values of chhrophyll and carbon fixa-tion in the euphotic zone are two to three times higherin the inshore than the offshore regions. Similarresults have been obtained for the inshore and off -shore waters in the subantarctic regions.

Surface antarctic waters are richer than surfacesubantarctic waters in pigment content: 1.27 mg./rn. 3 compared to 0.78 mg./m." In terms of sur-face C 14 uptake, however, the mean values of allthe stations occupied north and south of the Ant-arctic Convergence are about the same (5.14 mg.C/h/rn. 3 and 4.19 mg. C/h/rn. 3 , respectively). Theintegrated C 14 uptake in the euphotic zone also showssimilar results in both regions (about 0.9 g. C/rn.2/day).

A study of the main factors which influencephytoplankton production in the Antarctic(nutrient salts, stabilization of surface water, tem-perature, grazing, and light) show that light, tur-bulence, and grazing are the most important factorsgoverning phytoplankton production in antarcticwaters.

September-October, 1966 215