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Diatoms and silicoflagellates insuspension and floor sediments ofthe Pacific OceanO.G. Kozlova & V.V. MukhinaPublished online: 20 Sep 2010.

To cite this article: O.G. Kozlova & V.V. Mukhina (1967) Diatoms and silicoflagellates insuspension and floor sediments of the Pacific Ocean, International Geology Review, 9:10,1322-1342, DOI: 10.1080/00206816709474561

To link to this article: http://dx.doi.org/10.1080/00206816709474561

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Diatoms and silicoflagellates in suspension and

floor sediments of the Pacific Ocean

0.G. Kozlova and V.V. Mukhina

ABSTRACT: In the eight climatic zones of the Pacific, a direct spatial-geographical correspondenceis proved between density of diatom populations (together with the quantitatively unimportant associ-ated silicoflagellates) and the relative abundance of their siliceous relics in sediments on the oce-anic floor. This correspondence is almost ideal in the Subantarctic zone, demonstrable in the Sub-arctic zone and the equatorial belt, but is complicated (beyond recognition, in places) by terrigenicand other diluent materials and/or by the high solubility of the shells of certain species which neverreach the ocean floor. There is no evidence of any significant drift of diatom relics during theirsedimentation; the practical absence of diatoms, as in the Southern Subtropical zone, has its clearexpression in the absence of their relics in the zonal sediments. -- IGR Staff.

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(2), and both in suspension and sediments (3).

Internat. Geology Rev. v .9, no .10

Our problem is to ascer-tain the quantitative role ofdiatoms and silicoflagellatesin accumulations of siliceoussediments in the PacificOcean. A concurrent studyof these two organisms wasundertaken accordingly fromthe active layer to the sedi-ments on the ocean floor.The aqueous suspension wasthe original test materialcollected directly in the stir-ficial layer of the ocean andin the surficial layer of thefloor sediments (fig. 1). Sus-pended substance was segre-gated on the membrane filtersand also by the separator (Li-sitsyn, 1955, 1959) and hasmade possible the determina-tion of formation paths of di-atomaceous sediments in thePacific Ocean.

From the shores of Ant-arctica to Anadyr Bay, Ber-ing Sea, and in every one ofthe geographical zones of theocean, representative datawere obtained on populationsand species-compositions ofdiatoms and silicoflagellates

IGR Staff 'translation of IDiatomo-vyye i silikoflagellaty,vo vzvesii v donnykh osadkalch Tikhogookeana, Nauka Press, Moscow,1966, p. 192-218. From Geo-khimiya Kremnezema [GEO-CHEMISTRY OF SILICA]: NK65-12(51). The introduction andtable of contents of the book ap-peared in the January issue ofIGR, 1967 (v. 9, no. 1).

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O.G. KOZLOVA AND V.V. MUKHIN4

in suspension and floor sediments.

Our studies have made it possible to accountfor the noncoincidence of areas, containing largepopulations of diatoms in surface waters withthose in which the diatomaceous silts are beingformed.

MATERIALS AND METHODS

Suspensions collected on the membrane filtersor by the separator and samples of sediments_from the surface of the ocean floor were-utilizedin our work. The test materials, residues onthe membrane filters, were obtained on two me-ridional traverses through the Pacific, from theAntarctic shores to the northern limits of theocean.

The first traverse follows the 140° W merid-ian in the northern pa,rt and the 109 ° W in thesouthern part of the ocean (fig. 2). The secondtraverse begins in Anadyr Bay, follows the.174 °W, and is supplemented by the 160°W traversein the southern part of the ocean (fig. 3).

The suspension was sampled during the 10th,26th, 29th, and 34th sailings 'Of the -"Vityaz'and the 3rd sailing of the "Oh'.'

Every sample of the suspension-on the mem-brane filters represented 1 to 4 liters of sea water.

The tissue of a membrane filter must be de-colorized in liquid Canada balsam prior toexam-ination for diatoms and silicoflagellates. Good'visibility of diatom structures is-so attained.The filters were examined under biological mi-croscope, using Ocular 7 and the'immersionlens 90. Depending on numbers of: .the organo --,genic relics, one-half or one-quarter of the fil-ter's surface was examined. Cells of diatomsand silicoflagellates were counted, per 1 ma;and their species in the sample identified. Inall, 646 filters were examined, representing 68stations on both traverses.

Diatom populations of waters in the SouthernOcean were determined also in 38 samples of thesuspension collected by the separator. ' Everyone of the samples represented 100 to 200 m3of water from the 0-7 m layer. Numbers of dia-toms were calculated as per 1 g of sirspension.

All separator samples were treated with con-centrated nitric acid, in order to wash the algaefrom their organic contents.

The diatom content of sediments from the stir-face of the ocean floor was determined at 79 sta-tione on three meridional traverses (fig. 1).Counts of diatom cells and silicoflagellates,weremade per 1 g of dry sediment.'

1 A11 samples were processed by one and the same meth-od adopted by the Division of Marine Geology, Instituteof Oceanology, Academy of Sciences, USSR. Samplesof the suspension were examined by 0.G. Kozlova.V .v. Mulchina participated in the research on sedi-ments from the Pacific Ocean.

QUANTITATIVE DISTRIBUTION OF SILI-CEOUS ALGAE IN WATERS AND

SEDIMENTS OF THEPACIFIC OCEAN

The results of our investigations should bereasonably 'considered by the geographical zonesof, the Pacific Ocean.

The Antarctic zone lies south of the zone ofthe Antarctic diversion (70-66 °S). 5

Samples were collected in the fall of 1958,during the third sailing of the "Ob' 'in the south-ern Pacific Ocean.' -

During that time, the temperature of surfacewaters of the Western Drift was from -1.4 to1.78° C.

The diatom count v,vas, 40.3 million cells/m 3in the surficial layer, 0`to 25 m, of the ocean.The count decreased to 23.5 million cells/m 3 ,and less in the 50 to 100 m layer. The highestcount of diatoms was recorded at the surface ofthe ocean, in the Station 383 area, where it was69.2 million cells/m3. The high diatom count atthat station, in the suspension, is paralleled bymore than 307 arnorphouS silica [in the suspen-sion; dry weight basis?-- transl. J.

The numbers of diatoms decrease progres-sively at increasing depth, as diatoms sink from•

the surface layer to deeper horizons. An abruptbreak is recorded at the 300 m. The diatomcount between 500 and 3000 m is only 5.6 to 0.06%of the count at the surface.

In sediments of the Antarctic zone, in the areaof Stations 381 and 382, 2.2-2.9 million cells/-1 g were recorded. Proceeding from data on thedistribution of diatoms, from the surface to theocean floor, one may conclude that not over 5%of diatoms counted in the 0-100 m layer enterthe sediments. This conclusion is based on com-_parison of the number of diatom cells per 1 m 3water surface and per 1 g sediment.

In order to facilitate this comparison, the di-atoms. were counted also in the suspension ob-tained by the separatOr (as cells/gram of sus-

,pension).

From 10Q to 380 million cells/gram werecounted in the suspension ip coastal waters ofthe Antarctic zone collected by the separator,with the zonal average of 218.2 million cells/-,gram. The diatom count per 1 g of iceberg sed-iments was, on the average, 1.06% of the countper 1 g of separator susPension.

2 The limits of the Antarctic zone and all the others aregiven as coordinates of the stations.

3 The population counts are averages.

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INTERNATIONALGEOLOGY REVIEW

The small numbers of diatoms in iceberg sed-iments, as against"their numbers in the suspen-sion collected on membrane filters or by the sep-arator, may be due to the low resistance of theweakly silicified Antarctic diatoms to solubilityand to their strong dilution by terrigenic mate-rials in sediments of the coastal areas of Antarc-tica.

The abundant growth of diatoms in the surface,waters of Antarctica is assured by the ample sup.ply of nutrients. At the time when samples weretaken, the waters contained, in milligrams percubic meter, 56.5 to 57.5 phosphates, 2.64 to 4nitrates, 680 to 1350 silica. The silica contentwas found to be twice as high as in the Subantarc- -tic zone lying north of the Antarctic Divetgeirce -and, incidentally, higher than anywhere in thePacific Ocean.*

Counts of silicoflagellates show their num-bers are tens of times as small as the numbersof diatoms, both in suspension and sediments.Only 0.12 million Cells/m 3 were counted in the50-75 m layer and 0.002 million cells/m 3 at the1000 m depth. In Sediments of the same region,silicoflagellate counts are 0.06-0:19 Million cells/gram.

The numbers of silicoflagellates in suspen-sion and sediments were found to be smaller --than diatoms by two and three orderSVef magni-tude, respectively.

Numbers of diatoms in suspension and sedi-ments of the southern Pacific were comparedwith corresponding numbers in the Indian Oceansector of Antarctica (three traverses: 20 ° , 77° ,97° E).

On the average, 68.7 million cells/rn3 werecounted in the 0-25,m layer, dedreasing to 18.1million cells/M3 towards the 50-100 m layer insuspension in the Indian Ocean Sector'ef Antarc-tica (summer seaSon). - Tiflis the diatorri &buntsin the Indian Ocean were 1.5 times as high as inthe Pacific Ocean. This is explainable by thesummer stage of the phytoplankton in the IndianOcean sector and by its fall-winter stage in thePacific.

The number of diatoms at 300-2000 m depthsis 1/16 of what it is in the surface layer. Only0.06% of the latter has been preserved.

The iceberg sediments of the Antarctic zonecontain 0.055-0.7 million cells per gram, i.e.;0.7% of the diatom count in the 0-100 m layer.

Consequently, quantitative relationships inqhe

4 Hydrochemical data.are taken from reports on the 3rdsailing of the "OW" and the 10th, 26th, 29th and 34thsailings of the "Vityaz' ."

distribution of diatoms at the aiirface and in thedepths, as well as their ratios - in sediments andsuspension, are analogou0n-therAntarctic sec-tor of the Pacific to what they are in the Antarc-tic sector of the Indian Ocean.

The Subantarctic zone (66°753°S) lies betweenthe Antarctic Divergence and the Convergencezones.

• The temperature of-surface waters is higherin the Eastern thanin the Western Drift. Withinthe Eastern Drift, it increases from 1 ° C in thesouth to 5° and 7°C in the north.

• _ The suspension was collected in the fall dur-ing the 3rd 'sailing-af the "Ob'." In early Aprilthe diatom count for the-0-100 'in layer was 22.4million cells/m3. It had decreased to 5.2 mil-lion cells/m 3 by the end of the same month be-cause of the-encl - of.the growing season. The di-'atom count in thaf layer is ,one-sixth the count inwaters south of the Antarctic Diversion zone.

Up to 30% amorphous silica was found to bepresent in suspension samples from the Subant-arctic zone of the Pacific Ocean.

Vertically, at the 500-1000 m depth, the dia-tom counts decrease consistently. Within the2000-4000 rn layer, 'however, they increase ap-preciably in relation to counts iii the 500-1000layer. The diatom counts for the 2000-4000 mdepths are 25 to 45% of their numbers at the sur-face of the ocean, at sOme stations

'

but at someothers (more rarely) are almost twice as high asat the surface.

,Thus the decrease in counts, at increasingdepth; has a smoother Character in the Subant-arctic than in the Antarctic zone; moreover,there develops , a relatively significant accumu-latiOn of 'diatoins, at certain dePths, not observedin the Antarctic zone (fig. '4).

The diatom content of floor sediments was de-termined as 39.7 to 46.2 million cells per gram,in the Subantarctic zone, in the area where thesuspension was examined. This number is twiceas large, on the average, as the diatom contentof the suspension collected on membrane filtersfrom the 0-100 m layer. Abundance of diatomsin the zonal sediments is explainable by goodpreservation of the large coarsely-silicified oce-anic species and the insignificance of their ter-rigenic dilution on the ocean' floor.

Data on suspensions collected by the separa-tor may serve also in a characterization of thequantitative distribution of diatoms in surfacewaters Of the zone. From 15 to 120 million cellswere counted per gram Of this suspension, withthe zonal average of 43.3 'Million cells/gram, orone-fifth the count in suspension from the coast-al areas of Antarctica. FlOor sediments of theSubantarct,ic zone contain trice the number of

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O.G. KOZLOVA AND V.V. MUKHINA

higher: 680-1350 mg/m3.

The silicoflagellate count in the sur-face layer (0-100 m) is 0.024 millioncells/m3. They were found at the1000 m depth only at one station (0.002million cells/m3). Their count in thefloor sediments ranges from 0.19 to5.5 million cells/gram.

Comparisons were made betweennumbers of diatoms in the Pacific andin the Indian Ocean. (64 °-50° S) sectorsof the Subantarctic zone. In the Q-100 m layer of the latter, the count .was 12.5 million cells/m,3, i.e., twiceas high as in the same layer in the Pa-cific sector. The difference may bedue to the season: samples in the In-dian Ocean were taken in the summerand Pacific samples in fall-winter.

-1- ' The number: of diatoms .decreasesO.1 slightly at 300-5000 m in the Subant-

- T-t arctic zone of the Indian Ocean and atsome levels may even analogous tothe surficial count. .The_high degreeof preservation of Subantarctic dia-terns in the aqueous body accounts fortheir large numbers in floor sediments.Diatom counts in sediments are about .

_the same as at the surface or even twoto_three times as high.

The Temperate zone is situatednorth of the Antarctic Convergencebetween 56° and 42 °S.

CO0

4-

'

diatoms in suspension collected by the separator.

The ample development of diatoms imthe Sub-antarctic zone has-been favored' by higlyconcen-trations of biogenic elements in the zonatwater,of the nutrients essential to cellgrOwth, as, inmilligrams/m3 : 40.0-57.5 phosphates,' 3.20-4.56 nitrates, 100-680 silica. The nitrate andphosphate content are about the sarne in the Ant-arctic zone, but silica content is appreciably

Here, where the Subantarctic andSubtropical aqueous masses are mix-ing, the surface water is 5 to 15° C inthe fall.

The,diatom count in the suspensionfrom the surface (0-25 m) of the zone

3 — was 0.06 million cells/m 3, increasingto 0.075 million cells/m 3 in the 50-100 m layer. This shift of the peak

Indicates the end of the growing sea-, son and beginning of the settling of dy-ing cells. The peak of the diatomcount in waters of the Temperate zoneis characteristic of the 0-300 m layer.+A certain decrease is generally ob-served at 500 m

'

but the numbers haveincreased again by the 1000-4500 m

depths. Next to the floor, at 3000-4500 m, thediatom counts characteristically increase up to46-53% of their counts at the surface. Absolutenumbers of diatoms in these horizons remainrelativelysmall, however: 0.006 to 0.08 millioncells/m3. ,Diatoms ate found occasionally in theforaminiferal silts and in deep-sea red clays,typical of sediments of the temperate zones.Their surface layer may contain 0.84 to 1.6 mil-lion cells/gram, according to our data.

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INTERNATIONAL GEOLOGY'REVIEW

Numbers of diatoms in surface waters (0-100m) of temperate latitudes, in the Pacific Ocean,prove sinaller by two or three iorderS of magni-tude than in the Subantarctic zone.

In the suspensionfrom surfacewaters of theTemperate zone, cdllected by the separator,counts were 0.058 to 5.7 million cells/gram,with the zonal average of 1.5 million cells/gram.Floor sediments of the zone contained 0.84 mil-lion cells/gram, on the average, or 53.3% of thenumber in the suspension. 'Accumulations of di-atoms in sediments of the Temperate zone arerestricted by their small.poputations , in the sur-face waters, dominated by foraminiferg, and by _their dilution by foranniniferal shells -in - the sedi-ments.

Growth of diatoms in waters.of the temperatelatitudes is limited by the supply of biogenic ele-'merits, by no means as'abundant as gouth of theAntarctic Convergence.Convergence. The silica content ofthese waters is 1/3.5 and the nitrate content ishalf of what they are:in:the Subantaretic : zone.,Impoverishment of diatotn§ as,the result of de.-ficiency of the nutrients is supported ;by studiesboth of plankton and suspension(Naumdva, Zei - -nova, et al., 1962).

An up-welling of deep water rich in biogenicelements is observable in the area of Station 418.There are 10 times as many diatoms insurfacewaters at that station as at Station 420, in itsneighborhood. Even silicoflagellates (0.004-0.008 'million cells/m3) arefound.ati-Station 418, srabsent as they are at the others nearby.

_ -The abundant growth of diatoms in the zone of

the Subantarctic Diversion has its.ekpression al-so in sediments on the ocean floor in 'which thecount i§ 39.9 million cells/gram (Station 419).

On the average, the silicoflagellate count inthe 0-100 m layer of the Ternpdrate Zone is 0.006million cells/m3 ,' one-tenth of the diatom count. -None could be found at the 300-1000 m depth. Sil-icoflagellates reappear at 3000-5000 m, wheretheir number§ are 43% Of those in - the.surfacelayer. Their count is 0:03 to-1 million cells/-gram in sediments of the Temperate zone.

Cysts of chrysourionads,- up to 0:002 millioncells/m3, are also present in the suspension inthe surface waters of the Temperate zone, in ad-dition to diatoms and silicoflagellates.., Quies-cent spOres.of`the dhrysornonad algae are inweakly silicified envelopes.

The Subtropical zonelies between 34 °taficr.1-27° C. Here, in the 'surfaCe.Waters-of the SouthPacific Current, the temperature was found tofluctuate from 16° - to 22° C during the - fall'-s.eason.The suspension:was sampled in May,' 1958;,dur-ing the 3rd sailingof the "Ob . ."?

On the average, the diatom count was 0.014

and 0.009 million cells/m3 in the 0-25 m and 50-100 m layers, respectively. The diatom num-bers were at their peak only in the 0-300 m lay-er. A decrease occurs at the 500 ni level. At2000 m, diatoms were found only at Station 428,where the count was 4.9% of the surface count.

The small numbers of diatoms in the suspen-sion at great depths, in the Subtropical zone, ac-count for their scarcity and even absence in thezonal carbonate sediments. No diatoms could befound in the sediments at four of the stations (427,428, 429, 430) examined in the Pacific Ocean.;

In the 0-100 m layer of the Subtropical zone,the numbers of diatoms are only a fifth of whatthey are in the Temperate zone. This is under-standable, if we consider the impoverishment ofthese waters with regard to biogenic elements —phosphates and nitrates — in relation to waters attemperate latitudes. Subtropical surficial wa-ters contain, in milligrams per cubic meter, 3.5to 10.5 phosphate and 0.1 nitrate, as against 14.4-50 and 0.7-3.2, resPectively, present [in thelcor-responding layer] at temperate latitudes. -

No silicoflagellates could be found in the Sci8:tropical zone.

'Farther north, between 20 ° and 7° S, lies thetropical zone within the Southern Trade Wind T.'Current, where the temperature of the surfacewaters was foUnd to fluctuate from 25° to 29° C.The suspension was sampled in the fall-winterseason, during the 26th and 34th sailings of the"Vityaz'." The average diatom count in the 0-25 m layer was 0.005 million cells/m3; it waS,down to 0.003 million cells/m 3 at the 50-100 md.epths; no diatoms were found between the 150 mand 300 m levels. Diatoms reappeared at 500 niand persisted to the 6000 m depth. Between3000 and 6000 m, small as their numbers were,they still attained 32-50% of their numbers at thesurface,of the ocean.

Counts at deep levels show that only smallnumbers of diatoms enter the floor sedimentsof the zone, in keeping with their scarcity in, theactive layer of the ocean (fig. 5). The minimumand maximum counts in the surface layer of thezonal sediments were 0.015 and 1 million cells/-gram, respectively. They corresponded to 2.5%of the counts at the ocean surface, on the aver-age: The zonal foraminiferal silts and deep-seared . claYs arepraetically devoid of any relics ofdiatoms.

Diatom numbers in the 0-100 m layer of theTropical.zone.provedto be almost onerhalf theirnumbers, irCthe Equatorial zone, as a consequenceof the;deficiency'of-Tropical:waters. in-phosphates,silicates, ,abthother -nutrient;:salts. essential; for-plant growth; ;.;; ; ;11.-",, , \;,!.

Silicoflagellateso-werer encountered' as rs,carcean their 'count was 0.001 million

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thousanek10 Scells/m3

thousandcells/m3. ,

10 30 40 50 601,90

180

1000

FIGURE , 5.. Quantitativedistribution of diatomsin suspension from Trop-ical zone of SouthernHemisphere over car-bOnate sediments.

401111

FIGURE 6. Quantitative dis-tribution of diatoms in sus-pension from the Equatorialzone over radiolarian andforaminiferal sediments.Stations:

1 - 5105; 2 - 5107.

KOZLONA :AND: VN.:.i"IIIIJKHINA

cells/m3 at the depth of 100 m. They were justas scarce in the zonal floor sediments: 0.06 mil-lion cells/gram.

The Equatorial zone is between 5 ° S and 6° N..

The zonal suspension was sampled in the fall-winter season; during the 26ttrancl 34th 'sailingsof the "Vityaz'." Water temperature at the sur-face was 26° to 29° C.

The average diatom count was 0.007 millioncells/m3 for the 0-25 m layer. The count in-creased to 0.008 million cells/TO at 'the. 50-100 m depths; two to three times as high asthe same depths in the Tropical zone oflthe South-ern Hemisphere. The peak (19,500 ,cells/m3),wasrecorded in surface waters at Station 5094 on theequator. There were five times as many dia-toms in the area of that station as in the othersand counts remained high throughout' the 0-300 mlayer (fig. 6). The diatom peak at Station ‘5094corresponds to the high phosphate content of thesurface waters, higher than at the other stations.

Amorphous silica content of the, suspension in-creases at increasing diatom numbersin equa-torial parts of the ocean.

Large phytoplanktonic populations (collectionby nets) are reported by G. 1. Semina (1960) in thearea of the equatorial divergence '(0 ° datitude).

Stations:- 5082; 2 - 5004; 3 - 5098.

The number of phytoplanktonic cells , in the equa-torial waters was 2.5 times their number in thezone of the northern subtropical convergence(22°N). The largest biomass was recorded byN. M. Voronina'between lo° - 12° N and 5° -19° S.G. liasle.(1959) 'points. out the abundance of dia-toms,,'silicoflagéllateg, - coccolitines; and.peri-:dinieae in plankton of the Equatorial zone -of thePacific Ocean (00°01'-2°00'7"N, 145°05'6"W).

The high productivity of equatorial waters isexplainable, by the presence of .a mighty diver-gence by whichthe deep waters, rich in biogenicsubstances, are brought close to the surface.

The abundance of diatoms and other algae inthe Equatorial zone, as indicated by studies ofthe suspension; is typical principally of the sur-ficiallayer,_ 0-150 tn. At greater depths thesuspension likewise proved rich in diatoms (fig. ,6), wherein 'lies the difference between this zoneand the tropical areas in the southern Pacific -Ocean. The diatom count at 3000-4000 m depthsremains relatively high, 15-64% of the surfacecount, over the zone of foraminiferal silts aswell as over the zone of the siliceous-carbonatesediments, in the equatorial region.

The diatom count was 7.8-20.0 million cells/.-gram in the surface layer of the sediments close

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to the lower limit of their numbers in the oce-anic diatomaceous silts of Antarctica.

Numbers of diatoms in the surface layer of theEquatorial zone of the Pacific Ocean are largerthan in the tropical waters of both hemispheres,due to the abundance of mineral nutrients in theequatorial waters (twice as much silica, 10 timesas much phosphate as in the tropical zones).

The equatorial surface waters differ fromtropical waters by their relatively high numbersof silicoflagellates; 0.003 to 0.006 million cells/-m3 .

At depths of 3000-4000 m in the equatorial wa-ters, silicoflagellates were found at only one sta-tion, where the count was 0.0003 to 0.005 millioncells/m3. Members of the warm-water genusDictyocha were the predominant groups.

The silicoflagellate count in floor sedimentsof the Equatorial zone was 0.56 fo 1.35 millioncells/gram.

The Tropical zone in the northern PacificOcean is between 10° and 16° N.

Temperatures of surface waters in the North-ern Trade Wind .Current were 25.9 °-26.8 °C in thefall season of 1961 (34th sailing of the "Vityaz ").The suspension was sampled (hiring that season.

Diatom counts were 0.046 million cells/m 3 inthe 0-25 m layer and 0.005 million cells/m3 inthe 50-100 m layer. The number of diatoms de-creased abruptly in the 200-500 m layer, butcreased somewhat at the 1000 in depth and de-creased again at the 2000-4000 m depth. ,Nextto the ocean floor, at 4084-4779,rn depths, thediatom count wasas high as 30% and aslow as0.4% of their count in the 2000-4000 m'layer.The count was only 0.9-5.94 million 'cells/gramin the sediments in the deep-sea clays of thetropical zone.

Silicoflagellates were counted as 0.0003-0.002million cells/m3 at 0-100 m depths; 0.03 to 0.42million cells/gram were found in the sediments.

The Subtropical zone is situated between 20 °and 40° N.

The 1958-1959 winter temperatures imthe zoneof the northern Subtropical Convergence*, and -north of the zone, ranged from 15.7 to 22.6 °C(29th sailing of the "Vityaz' "). The suspensionwas sampled at five stations.

Only diatom algae were fOund in the suspensioncollected on the membrane filters.

In the northern part of the zone (40° -25° N), inthe 0-25 m layer, the number of diatoms variedfrom 0.001 to 0:004 Million cells/m3;. the rangewas 0.001 to 0.012 million cells/m 3 at 50-100 m

depths. Counts were even lower in the southernpart of the zone (20°-25N). The frequency-oc-currence of diatoms at the 0 and 75 m levels doesnot exceed 0.001 million cells/m3, i.e., is simi-lar to their numbers at 75 m and 100 m levels inthe northern part of the tropical zone.

The diatom peak is in the 0-100 m layer bothin the Subtropical and Tropical' zones. Below,the suspension proved to be devoid of diatoms atfour of the station sites. Only at Station 4293were they found, at the depth of 2000 m, 0.001million cells/m3, i.e., the same number as inthe surface layer.

The scarcity of diatoms both at the surfaceand in the depths of the subtropical waters affectstheir numbers in the surface layer of the sedi-ments. The count does not exceed 0.42-5.79 mil-lion cells/gram and is nil at Station 4245.

On the whole, subtropical waters are extreme-ly poor in diatoms, both in the northern and south-ern parts of the ocean; their spread is confinedto the 0-100 m layer and their numbers are 1/15of what they are in the Subarctic waters farthernorth.

Silicoflagellates were entirely absent in theaqueous body, and were encountered in sedi-ments at only one station, as 0.24 million cells/-gram.

The Temperate zone lies between 40° and 56°-30N.

The zonal suspension was sampled at ten sta-tions in the northern Pacific Ocean (fall of 1958,29t1i sailing of-the !Tityaz' "), and in the south-ern deep-water part of the Bering Sea. Temper-ature- of stilace ,water in the northern part of theocean was 7 ° to- 11°C. during the sampling.

On the average, diatom counts in suspensionwere 0.063 million cells/m 3 in the 0-25 m layerand 0.022"million cells/m 3 in the 50-100 m depths

The peak of diatoms in waters of the Temper-ate zone was recorded in the 0-100 m layer (fig.7). Counts decreased to 75.8-0.7% of the num-bers at the surface when the 300-1000 m depthswere reached.

In the north of the region, in Subarctic watersover the zone of terrigenic sediments, in sam-ples collected deeper than 1000 m, diatoms areeither absent or 0.7 to 27% of their numbers atthe surface.

Distribution of diatoms in deep water horizons,over the weakly siliceous sediments in the cen-tral part of the zone, and also in its southernpart over the red clays, differs from their dis-tribution in the northern part by its relativelyhigh diatom counts at depths exceeding 1000 m:up to 76.5-100% of their counts at the surface of

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the ocean. This is explainable by the preponder-ance of thin-shelled diatoms in the north, mostof which dissolve within the 50-100 m layer,whereas it is the large coarselr-silicified oce-anic species that form the bulk Of Populations inareas far away from the shores . capable ofreaching the ocean floor with only minor loSses.

The diatom count in sediments of the southern

cc

czz) E?„,3 2cza

, ,"•-a

part of the temperate belt was 20 million cells/-gram.

On the whole, number of diatoms in the sur-face layer of Subarctic waters of the PacificOcean is hundreds of times as low as in the Sub-arctic (coastal) zone of the Bering Sea.

Silicoflagellates are numerically subordinate

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to diatoms, in the 0-100 m layer, as usual; theircounts are 0.002 to 0.025 million cells/m 3 (4.2-67.5% of diatom counts in the 0-100 m layer). At500-3000 m depths-, they are encountered as0.006-0.009 million cells/m3 and in the floor sed-iments — 0.1 to 0.4 million cells/gram.

The Subarctic zone includes Anadyr Bay of theBering Sea. The test stations lie between 63 ° 30'and 64° N. The numbers-distribution of diatomsand silicoflagellates- was determined in the sus-pension at five stations, at three of which onlythe surface layer was sampled and at two (Sta-tions 1547, 1545)— also the layer next to thefloor.

The concentration of diatoms in the surfacelayer of Anadyr Bay was as high as 52.4-167 Mil-lion cells/m3 ; with the average of 73 millioncells/m3 . We found no such high concentrationsin the northern areas of' thePacific Ocean. Thenext-to-the-floor layer at Station 1545 (200 m)preserved only 1 million cells/m3 or 1% oft thenumber of diatoms at the surface.

Diatom content of the surface layer of sedi-ments in the area of Station 1545 is 5 millioncells/gram (G. S. Koroleva's communication).These data show that only 5.4% of the diatoms 1growing at the sea surface are buried in the Ana-dyr Bay sediments, 'in the area of Station 1545.

The surface waters are richest in diatoms,as a rule, because of their high concentrationsof biogenic elements. Their phosphate was de-termined as 20-60 mg/m3 and their silica 5 'as500 mg/m3 in May, 1952, at the time of sam-pling of the suspension (Mokiyevskay,a, ;1959).

1In Subarctic waters of the Bering Sea, in, the

0-100 m layer, the average diatom count is:million cells/m 3, as against 40.3 million cellsy-m3 at the same depths in Suhantarctic waters.It appears here that the difference is due td theseason. The northWestern part of the Bering Seawas sampled in the summer, but the Antarcticwaters, from fall through winter. The smallnumbers of diatoms in floor sediments of AnadyrBay (2-5 million cells/gram) and he Antarcticzone (2.2-2.9 million cella/gram) .are duetdently to terrigenic dilutions, as well as to , small-ness of the accessions of diatom shells from thesurface layer. In deeper horizonS;Of„AnadYrand in the coastal areas of Antarctica, 'diatom -counts [in the sediments? -- trans1.]correspondto 1.1-1% and 0.06-5.6%, respectively, of their --;counts at the surface. Low concentrations of di-atoms in deep horizons of 'these areas are 'plainable by solution of the bulk of thin-shelledneritic diatoms during their settling through theaqueouS bddy orito -theflcior.'

6 "Silicon" in the original: apparently a misprint. --Transl.

In waters of Anadyr Bay, in the 0-100 m layer,silicoflagellates were encountered, as many as0.002-0.035 million cells/m3 , feWer by three or-ders of magnitude cells than the diatoms at thesame depths.

The distribution data on diatoms and silico-flagellates in the Pacific Ocean,. in the suspen-sion collected on the membrane filters, as wellas by the separator, allow us to draw the follow-ing conclusions:

1. The numerical peak of diatoms occurs insurface waters of the Antarctie.zone and the north-ern part of the Bering Sea in the Subarctic zone.Diatom and silicoflagellate numbers decrease ontransition from high to low latitudes, both in thesouthern and northern hemispheres, alongsideimpoverishment of the biogenic nutrients in thesurface waters (fig. 8). Only, in the Equatorialzone, where surface waters are relatively highin biogenic elements, is there an increase in thenumbers of siliceous algae in the waters and [oftheir relics] in the corresponding sediments.

2. Certain features in the quantitative distri-bution of diatoms at the surfaCe' and in the,depthsare common to both southern 'arid northern partsof the Pacific Ocean. The 0-100,m layer is rich-est in diatoms, both in the Subaretic zone of theBering Sea, over the terrigenic sediments of Ana-dyr Bay and in the Antarctic Zone, over the ice-berg sediments of the Ross Sea. Waters deeperthan 100 m, in both these areas; are radicallyimpoverished in diatoms. Orily a small portionof the diatoms at the surface (from 0.06 to 5.6%)is able to reach the next-to-the-floor horizons inthe Antarctic regions. In the Bering Sea the Ana-dyr Bay pattern is analogous; according to ourfindings, because of the low stability of neriticspecies inhabiting the coastal waters. Data onthe species-composition of diatoms in sedimentsof the Antarctic regions and the Bering Sea showthat about 65-70%i of the neritic Species, in highlatitudes of the Pacific Ocean, dissolve complete-ly in the surface.waters after the end of the grow-ing season.

3. In open-sea parts of Subantarctica and inSubarctic waters of the-Pacific Ocean, the deep(2000-4500 m), , suspension is rich in diatoms, un-like that iticoastal areas of Antarctica and theBering..Sed:'' The reason for this is the sparsesolubility of oceanic diatoms, enabling them to

° reach the floor where they are buried in the sed-iments. The difference in -solubility between oce-anic and neriiic spebies rernains consistent inall zones of the Pacific Ocean.

SilieOflagellates accumulate mainly in the0-100 ;ni'laYer.'theit"-vertical distribution [i.e.,relatiVe'dbiindanee the depths in dif-ferent zone's is the same as at the'correspondinsurface of the ocean. - Silicoflagellates arecountered . 'cloWn to 5000 m, in their characteris-tically high state' Of Preaervatien; However, inthe Antarctic zone their numbers decrease down-Ward, to the 1000 it level, to tenths Of their num-

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8.0241812630

g 20a: a

600

6400Zag -

ZOO

150100

I

50

56' 60 54 43 45 36 30 24 12 6 0' 6Coordinates

24 30 36 42 48 54'N

▪ 0.545

• 04a20

O.G. KOZLOVA AND V.V. MUKHINA

FIGURE 8. Quantitative distribution of diatoms in suspension from the0 to 25 m layer (I - million cel I s/m3), in sediments (2 - millioncells/g of sediment), biogenic elements (Si, P), temperature ° C,

and pH. Traverse I.

bers at the surface. The silicoflagellate countsin suspension and sediments are appreciably low-er than the diatom counts, because of their smallpopulations inithe plankton of the ocean.

COMPARISON OF QUANTITATIVE DIS-TRIBUTION OF DIATOMS IN SUS-

PENSION AND SEDIMENTS

Distribution characteristics of diatoms in thesuspension collected from different ,depths of theaqueous body enable us to understand their func-tion,in.the,sedirnentation of the Pacific Ocean.Information is now available on every type of sed-iment whose development is obviously related togeographical zonation, so that the causes of suchsedimentation are understandable to a certaindegree.

Data on the role of the more or less siliceousdiatoms in the accumulation of siliceous sedi-ments are summarized in Figure 9.

1. The diatom, count was 0.05 to 5.4 millioncells/gram in iceberg sediments on the Antarc-tic Shelf (by the King George V Coast, Oates

Coast, Victoria Land, and farther east — in theseas of Ross, Amundsen, Bellingshausen, in theDrake Straits and at Adelie Land). The predom=inant species are neritic-Antarctic: Flagilariop-sis curta Flust., Fr. sublinearis 'Held., Eucam-pia balaustium Cast.

The silicoflagellate content of the iceberg sed-iments was 0.06 to 0.19 million cells/gram.

Alongside diatoms and silicoflagellates, cystsof chryson-ionads in their weakly silicified enve-lopes were also found in these sediments (0.06-0109 million cells/gram).

Judging by analyses of the suspension, the lowdiatom. content of the sediments is explainable bythe relative instability of neritic diatom shells,most of which pass into solution before they reachthe floor. Despite their large numbers at thesurface of the ocean, only a few, 0.06-5.4% ofthe original total, can settle down to the greaterdepths, so serious are the losses in transit.

In the fine aleuritic fraction of coastal areas,

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MIlloon 1111111111 IDA0-97,1: :i

MI11111 11

INTERNATIONAL 'GEOLOGY REVIEW

FIGURE 9. Number= of diatom cells per grbm of sediment from era.surface of the floor of the Pacific Ocean (millFon-cel s).

tion. Not over 6% of the diatoms ofthe surface layer enter the clayey,diatomaceous silts of the shelf, evenas In the case of the iceberg sedi-ments, i.e., only a minor part ofthe primary crop reaches the floor.However, even this part is largeenough for the accumulation of sili-ceous sediments, under certain fa-vorable conditions relating to terri-genic ,dilutions4 as in the area of theBalleny Islands, for "example.

2. The diatom content of the typ-ical zonal diatomaceous silts devel-oping on the continental slope andon the ocean bed, in the Pacific sec-tor of Antarctica, is 43 to 221 mil-lion cells/gram. This number de-creases to 40 million (Station 385)and even 19 million (Station 384) on-ly on the surface of the South PacificSubmarine Uplift, because of wash-ing,of shella off the high ground and-*deposition in deeper parts of the

iiia.',calmer hydrodynamic en-vironment.'

In the northern part of the zoneof oceanic diatomaceous silts, thediatom count is at its minimum, 12.7million cells/gram. This decrease

'contingent upon two factors: lim-ited growth of diatoms within theoceanic plankton and their dilutionin sediments by shells of foraminif-,

the share of diatom's is 2-3% (communication byG. S. Koroleva, G.-A. , Nagayeva).- According toA. P. Lisitsyn's data, the iceberg sediments con-tain not over 4.06-11.6% amorphous silica.

However, sediments are also found in placeson the Antarctic Shelf, containing large numbersof diatoms. For example, at the Balleny Islands,2400-2700 m down, there are clayey diatomaceoussilts (Lisitsyn, 1960) with 6.7 to 32.1 millioncells/gram. Diatoms in the fine-aleurite,frac-don of the sediment from the zone of clayey dia-tomaceous silts constitute 40% [of the particles?of the fraction? -- trans1.1 on the average, with[corresponding to? - transl. ] .12. 14 - 6%!arrior -phous silica. The Antarctic, neritic diatoms arepredominant here, even as they are in the ice-berg sediments. -

The deep-sea suspension over the zone of clay-ey diatomaceous silts is poor in diatoms (0.9r6%of their numbers at thel surface of the-ocean).Consequently the accumulation of clayey diatoma-ceous silts on the shelf requires special eXplana-

Diatoms constitute 67% of the finealeurite fraction, on the average,in the zone of diatomaceous silts.According to A. P. Lisitsyn's oral

communication, amorphous silica content. of theAntarctic deep-sea diatomaceous silts variesfrom 25.7.to 55.8%. There is a close correspond-ence between the number of diatoms in the sedi-ment and the amorphous silica content.. The high-est concentrations of Si02 amorph . , 51 to 58.5%,correspond to the highest diatom count, 160 to206 million cells/gram.

• .Diatomaceous silts are made up of oceanicSubantarceic diatoms. The principal constitu-ents are the .valves of the Fragilariopsis antarc-tica Hust. (up to 60-70% of the total count), as arule:. The combined share of the Coscinodiscus.lentiginosus Ianish and Thalassothrix antarcticaCl. et Grun. is 10-15%. The following species -are subordinate with regard to development ofthe silts: Schirnperiella antarctica Karst., Cos-cinosira arnarctica Koz1.,.Coscinodiscus tabu-lar's Grun., Asteromphalus hookeri Ehr.

Silicoflagellates.,. 0.9 to 5.5 million cells/gram,were recorded in the oceanic diatomaceous silts,a much higher connt than in iceberg sediments.

1 - none; 2 - 0.05 to 5; 3 - 5 to 20; 4— 20 to 60;5 - 60 to 180; 6 - > 180 (highest count: 220).

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But what do we obtain in studies of the suspen-sion, to help us understancttlie accumulation ofdiatomaceous silts in the open-sea deepwater Sub-antarctic regions?

It has been proved, first "of all, that diatomcounts are appreciably higher horizOnsnext to the floor, than in the Antaretic zone. Asmany as 28-40% of their numbers at the surfacewere counted at several stations, down to greatdepths, and counts were so,, high at some othersas to show 1.5-2 times as many diatoms as in theactive layer.

These facts indi-cate a 'high - state- of- preSer va-don of oceanic species inhabiting open-sea re-gions of the ocean. At Station 385, for example,the suspension counts of Fragilariopsis antarc-tica, ,typical of the oceanic ,diatomaceous silts,were praCtically the same at all depths, fromthe surface to the ocean floor. Fr. antarctiea constituted 50% of total diatorns 67.n the 0-100 mlayer; 47% — at the deeper levels, 300-1000 rn,-,but up fo"76% in the 2000 rri•orizon, nearest thefloor. Fr. antarctica often'accounts for 60-80%of total diatoms in the diatomaceous silts at Sta-tion 385.

Because of their high state -of preservation, alarge share of the SubantarCtie oceanic speciesparticipates in the accumulation of diatomaceoussilts. The negligible terrigenie dilution, in theopen regions of the ocean, far-away from theshores,, undoubtedly plays an itti09.1taat.Part inthe deyelOpment of such silts. 'Otir" -data.on, thenumbers andspecies i ,eomposition of iatoms inthe sediments dn„the:Cdntinental slope - Ow thatthis is'defirikely-the- -eaSe. te_ib,"tlie largewell-preserved oceaniespecies , are predominant .,although their 'concentrations in the sediments areeight times as dilute as on the ocean floOr, be-cause of the large terrigenic accessions. .

3. In the TemPerate,,,,Subtropical, and Tropi-cal zones of the southern Pacific. Ocean,,wherethe sediments are uniformly poor in diatoms, on-ly relatively small quantities of test materialswere exaniined. "FOr" that teason,Weare givinghere only an over-all charaCterilatiOn.,Ofall threezones, with regard to the ,diatom distribution insediments of different types.

From 0.84 to 2.4 million cells/gram werecounted in the red deep-sea clays and in forami-niferal silts. The counts fell to 0.04 million andlower (0.01 million -at the lowest) in northernareas of the Tropical zone.. No diatoms couldbe found in sediments at certain stations .(3812,420, 423, 424, 427, 429, and 430) in the zone ofred deep-sea -clays and foraminiferal silts.

The diatom content of the fine aleurite frac-tion, in typical carbonate sediments, is not over2-69

As of the total number of diatoms in 0-100, 300-1000,2000 m layers, respectively.

The scarcity of diatoms in the plankton of allthree zones explains, their lbw cOunts and occa-sional'absence in carbonate Sediments and in reddeep-sea clays. The diatom numbers in the sur-ficial-layer (0-100 m) are smaller here by threeor four orders of magnitude than in the Subantarc-tic zone and their numbers in the depths are thatmuch smaller.

, 4. The average dia.tom , count is 7.8 millioncells/gram in the siliceous-carbonate sedimentsof the Equatorial zone, with the peak of up to 20Million•cells. Amorphous silica content of thesediments here is about 6% on the average, i.e.,almost 3.5 times as high as irisediments of theTropical zone.

The silicoflagellate count in the zonal forami-niferal silts and the red deep-sea clays was 0.06to 0.3 milliOn cells/gram.

The high diatom content of the zonal sedimentsis evidence of their , ample accession from theocean surface. Their count in the suspension •from the 3000-4000 m depths is also high:'64% of the surface count.

Thus it is possible to visualize the role of di-atoms in zonal sedimentation by the character oftheir relatively high count in the aqueous body ofthe Equatorial zone.

5. In the northern part of the Pacific Ocean,in the area on the red deep-sea clays of the Trop-ical zone, ,diatotns are S`care indeed.: The Si02-amoili. content

,

P°t.e'-ceed Tl.84%:' t-lighest diatorn -dblints were 0.033million 'cetIs/gralti at Stations' 5128 and 4347, andnone Was encOutitered in sediments - at Station4245.--Consequently, a cOnclusion is forced tothe effect-that sediments-pf - the-tropical!regions'north 9f the eqUatOrare - especially poor in dia-toms, - in relation-to their distribution traverse,,from"the''sliores Of'‘Aritarctica to 22 °N. :Asa mat-ter of 'fact aside from the occaSionally encoun-tered' individual cells the zonal sediments maybe conSidered diatom-free. The same applies tosilicoflagellates; for practically, none , are foundin the typical red clays:'

Data on the suspension,indicate an exceptionalscarcity of both diatoms and : silicoflagellates inthe tropical waters, from the surface to the floor,although the species who live_ here are distin-guisheckby their high state of preservation.

6. In the Subtropical zone (20-40°N), in thered. deep7sea clays and' terrigenic sediments, thediatem coUnt is -0.003-2.2 million cells/gram'andthe silicoflagellate count is 0.36 million cells/-gram, on the average. Such poverty may be un-derstOod, were we to analyze the diatom and sil-icoflagellate counts in the suspension at the sur-face as well as in the depths. The diatom peakin the suspension was recorded in the 0-100 mlayer, but there were practically no diatoms ingreater depths.

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7. The terrigenic sediments lie in the Bo-real Region, north of 40-45 ° N, along the mar -gins of the ocean, and next to them, on theouter seaward]— weakly sili-ceous diatomaceous-silts. The not too wide-spread redclays are found in central parts of

711 -2 `8 2:67.63% and the corresponding diatom count is rt4:11,r4 oi) •11.23 million cells/gram.. The minimum

° 40count, in the terrigenic sediments, is 4.5 mil- J,

lion cells/gram and the maximum, in the CA' u 0weakly siliceous diatomaceous silts —26.39million cells/gram. The most common -torn count is 10 million cells/gram. Diatomcontent in the North Pacific sedimenta is high -erby almost 4million cells than in` t'he Equa-torial zone (11.23 vs. 7.8 million cells).

-The average Si02 amorph . content of the

surface layer of the regional sediments , is

Low concentrations or -absence of diatoms'in suspension from the depths over the terri-genic sediments, 'along the northern marginsof the:ocean,' are indicateclby our 'reaultS.' Onthe other hand, there is an abundance of dia-toms in such suspension over the clayey-dia-tomaceous silts: - up to 75-100% , of the num-bers countedat the' su ,rface of the ocean. Theample accession .of diatoms onto the 'floorleads to a development of clayey-diatomaceoussilts in northern parts of the region, remotefrom the shores.

_ .The northertiboreal diat onn species ore tni-

meric0:13'..-,13,t01.90-nOli.a.rnOig the .others,sediments Ofin'eB4Orseal Zone. Theft'tions are "from72 to 97,4% The:following ati'eparticularly abundant (70.13 , 97.4%): Dp.ntictiAa,seminae, Simonsen et ICanaya,' COseinodiscUs,'marginattis Ehr.,.C. curvatuluaGrta, cyclus divisas -„Kiss., RhizoSolenia hebetata:Gran., Tholassiothr ix lOngissifna Cl.Chaetoceroaspp. (spore). - IA,se_climehts in the*north of theregion

7 small riutribers: of the Arc-'

tic-Boreal neritic -species are alse found (0.5to 18.2%):, thalossiesiragroVida Cl., .Th. nor:-denskioldu Cl,„clus ochotensis Joksc., Bacteroaira fragilisGran., Porosira gracialis JOrg.

Numbers of silicoflagellates encounteredin sediments aretharacteristically'subject toappreciable variation. None at all were found atStation '4209, burgenerally' their. concentrationsare definable as 0.18-0.42 million cells/grarth •

-,%) 50

50

5 405

;.•

FIGURE 10. Average-numbers of diatoms and silico-f I agella tes and percentages of- amorphous silica

in,sediments of the Pacific Ocean.

I - iceberg gidiments;2 - clayey-diatomaceous silts;3 - ter`rigenic-Organcigenic sediments;

2+ - oceanic diatomaceous silts;5 - forannnilfera,1 silts;6 red deep-sea clay;7, - sediments of modern volcanic areas;8 - radiolarian silts;9 - wealchi-siliceous diatomaceous silts;

10 - terrigenic sediments.

8. The diatom content of the Bering Sea sedi-ments is 1.7-6 million cells/grarp;,whiCh corre -sponds to 5 to 1% and less, of their nurnlierthe surface of the sea. Exanainations äf suspen:-sion at the surface -and from the depths showedthat 1% and less of the surface diatoms maketheir way to the ocean floor.

The relationship between the type of sedimentand the numerical distribution of diatoms, silico-flagellates and amorphous silica, is representedin Figure 10 (all data are averages).

4

5 1110

In iceberg:sediments on the Antarctic Shelf,where the average diatom count'is .2.2 million -cells/grain, the average amorphOus silica is7.29%. As numbers 'of diatoms increase, in si-liceous-diatomaceous silts, amorphous silica al-so increases up to 11.6%, on the average.

In the intermediate zone of terrigenic-organo-genic sediments, on the continental slope of Ant-arctica ; the.numbers of diatoms are 1.7 timesas high as. in iceberg sediments, but only halfwhat they are in the clayey-diatomaceous siltsof the shelf. However, the Si02 amorph . con-tent of both is the same. This is explainable bydifferences in the thanatocoenoses of the diatoms:the preponderance of neritic species in clayey-

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diatomaceous silts .pfrthe ,Shelf and Oceanic spe.7 : .,cieS -dn'terrigertic-organogehic sediments of,thecontinental -

The average diatom content of diatomaceous •silts in the southern part of the-Pacific Ocean,..101.6 million cells/gram, corresponds, to the av7erage Sj-02 amorph: content: 39.3%.

The numbers of 'diatoms and , silicoflagellatesdecrease abruptly in sediments of the Temperateand Subtropical zones.

In carbonate sediments of the Subtropical •zone, the diatom count attains 2.57 million cells/-gram and the SiO2 ainorph. -- 3.4%. 'The count ishigher in the red deep-sea clays than in forami-niferal silts. In Ted deep-sea clays, the diatomcount is higher than in foraminiferal silts, 3.95million cells/gram, on the average, and theSi02 , s moroy. Content is higher too.-

In volcanogenic sediments lying at the , bound-ary'between the' Subantarctic and Subtropicalzones, diatom content is 0.04 million -cells/gram.No silicoflagellates could be found. The Si02-arriorph. content proved to be even lower than intypical terrigenic sediments.

In the radiolarian silts, diatom numbers in-crease to 11.4 million cells/gram and silicofla ,gellates - to '0.69 million cells/gram. The amor-phous silica content goes up to 7.44%.

The highest diatom count, 22.9 million cells/-gram and the [zonal? transl.] peak of Si02-amorph: (9 . 62 D are typical of-weakly' siliceousdiatomaceous silts. widespread in the -northeast-ern Pacific Ocean, andyet the diatom count in .these sediments is 1/4.5 of that in typical diato-maceous; silts of the Subantarctic zone.

In terrigenic sediments of continental and in-sular shallows in the northern Pacific Ocean, thediatom count is 8.59 million cells/gram and theSiO2 amorph. content is 5.39%. Such sedimentsmay be termed appropriately as weakly-weakly"-siliceous diatomaceous silts.

In concluding our characterization of-the dis-tribution:of diatoms andrsilicoflagellates in thefloor sediments-of the eight zones of the :Pacific -Ocean, we should emphasize the following.

It is:evident that concentrations of diatoms insediments depend on population•nurnberS'of 'di-a-toms, in plankton; in the •aCtive;layer of the .oceanHowever,: thia ,direetqlependetice is effective drifYin areas-i6 which , the' higliedte- ,Of ;preS erVat ionof the diatom valyea.accOnnpaineS Itegligibleter-rigeniCrdiIutionsiofthe edimetits].;:..The idealcage is recorded in the ,Subantaretic zonePacific Ocean,. in the deVeloprnent of 'typical dia-rtomacepaa silts. .Asq0 the-Antarctic zone ; theveryhigh'crbp yie1cIs of -diatOrna in Stirfaceters are not conducive to development of diatd-

rnaceous silts, asra rule. The relationship.is in-hibited:partly by the high: solubility of 60770% of,the cliatorn_species,- partly by the terrigenic dilu-tionfof the remainder] on the ocean floor.

The situation is the same on the Bering Seasheff,.;

Siliceous sediments do not develop in the trop-ical region, With the exception of the, Equatorialbelt, simpybecauSe there are not enough_clia-toms in the active layer of the ocean, althoughterrigenic dilution is, often negligible. Such en-vironment is characteristic of areas in which thered de-sea clays andforarniniferal silts areformedi'aithough ter.rigenic dilution is appreci-able in the latter.

The deep-sea sediments of the Boreal regionare in arrintermediate position. Abundance ofdiatoms- in the planktorrheré is conducive to theiraccumulation in thesedirnents, 75Wof theorigi.-nal number of the species is preserved, and theterrigenic accessions are relatively moderate.

QUALITATIVE CHARACTERISTICS OF- DIATOMS IN DIFFERENT ZONES OF

THE PACIFIC OCEAN

Seven, complexes- of diatoms, typical' of differ-ent zones of 'the' a.rerecognizable on thebasis ,- of our data obtained in studies of the sus-pension on the•two traverses across. the Pacific.These:complexes are distinguished,. each by itsown species-composition' and'also.b3i. its type ofdistribution within the aqueous body.

The-Antarctic neritic:complex, inthe 07100 m layer, includes 34 species. Fragi-lariopsis, curta Hust. and Fr. cylindrus Helmckeet Krieger are predominant., :Thalassiosira gra.-cilis Hust. and Fr. rhombi -cal-lust. are subdomi-nant.

Small . nunabers of the oceanic species, Fra.-.gilariopsis antarctica Thalassiothrix ant-arctica Cl. et Grun., are as a rule found in thesuspension, alongside the.neritic species.

• Thenumber of diatoms at 300-2000 m depthsis reduced to -one-third. Fragilariopsis curta,Fr. rhoinbica, and Thalassiosira gracilis remainnumerically predominant. •

Fragilariopsis curta, Eucarnpfa balaustium are predominant 'in sedinnents derived from ne-ritie diatoms. Oceanic species, Fragilariopsis antarctica;Thalassiothrix antarctica, are en- -countered among flora in the sediments along-side the neritic species. The two together ac-count for hot over 10-20% of the total , diatomnumbers in the sediments we examined.

% of diatoms recorded in the. 0-100 mlayevils.".preserVed in floor ;sediments: of the Ant7arctiC-zbrie..

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The Subantarctic complex of diatomsin the Slispension from the, 0-100 m horizon in-cludes 41 species. The oceanic Fragila.riopsis antarctica Hust. is predominant, accountineorup to 65% of the total number of cells. Coscino-discus lentigonosus Ianish, Thalassiothrix ant-arctica Cl. et Grun., and Dactyliosolen antarc-ticus Castr. are found in smaller numbers.

The number of species is reduced to 20 dur-ing their settling, within the 300-500 m range ofthe depths, the result of solution of thinly silici-fied [thin-shelled? -- transl.] species of .Chaeto-ceros, Nitzschia, and Tropicioneia genera. Thereis no change in the number of species at 1000-4500 m, as against their number,at 300-500Only the thickly silicified [thickshelled?trans1.] species, Fragilariopsis antarctica, Tha-lassiosira gracilis Thalassiothrix antarctica,Coscinodiscus lentiginosus, and -.Schimperiella antarctica endure in the suspension at great .depths, and these species do reach the floor sed-iments.

There is a resemblance accordingly betweenthe species-composition of diatoms in floor sedi-ments and in the suspension in great depths. Six-ty to seventy percent of the number of speciesfound in the 0-100 m layer of the Subantarcticzone is found also in the [zonal] sediments onthe oceanic floor. Twice as many species as inthe Antarctic zone are able to reach the floorhere and remain buried-in the sediments. Thisis explainable by the good preservation of dia-toms inhabiting the Subantarctic : zone.

A mixed comp lex of diatoms character-izes the intermediate zone between the Subant-arctic and Subtropical aqueous masses. It in- •

eludes 54 species. The increase in number ofspecies idareas where the-waters mix is due tothe appearance of-several ecological complexes,in which the Subantarctic and Subtropical corn-plexes are preponderant. Among the Subantarc-tic diatoms, the principal ones are Fragilariop-sis antarctica and Thdlassiothrix antarctica.

The number of diatom species is reduced- to22 on reaching the 300-500 m layer. Membersof Rhizosolenia, Chaetoceros, and Nitzschia van-ish in the 300-500 111 layer. Subantarctic oce-anic species are numerically preponderant at500-4500 m depths.

It is difficult to form an opinion on the diatomcomplex in the Tropical zone of the southern Pa-cific Ocean. Very little suspension from that-zone was available to us and this was practicallydevoid of diatoms.

In the complex of diatoms fromthe Equatorial zone, 23 species werecounted, with the following characteristic rep-resentatives of the tropics: Thalassiothrix,fraun-feldii Grun., Coscinodiscus nodulifer A. Schmidt,Asteromphalus diminutus Mann, Rhizosolenia

calcar-avis Schulze, Rh. bergonii H. Perag.Alongside the tropical, .subtropical species werealso present: . Thalassionema nitzschioides Grun.,Nitzschia bicapitata Cl. N. oceanica Cl., N. de -licatissima Cl., and others. The number of dia-tom species is reduced to one-half to one-fifth at300-500 m. At the stations where thinly-silici-fied species of Nitzschia genus were predomi-nant, percentages of diatoms reaching the floorwere smaller than at stations where coarsely-silicified Coscinodiscus were the principal forms.

There is no reduction in numbers of speciesbelow the 500 m depth, within the 100074993 mrange. The following were found in ,the suspen-sion at great depths: Planktoniella sol.Rhizosolenia bergonii H. Perag., Pseudoeunotia doliolus Grun., Roperia tesselata Rop. Coscino-discus nodulifer A. Schmidt.

All species preserved down to 1000-4993 mwere encountered also in floor sediments. Thevariety of diatom species in sediments of theEquatorial zone is wider than in the correspond-ing 0-100 m layer.

The Tropical complex of diatomsin the northern Pacific Ocean includes 19 speciesin the 0-100 m layer; 20% of the diatom popula-tion consists of Sceletonema costatum Cl., andeuryhalitic and eurythermal species. Tropical-species are also present here: Planktoniella sol.;as well as subtropical: Nitzschia bicapitata, N.delicatissima, and Pseudoeunotia doliolus.

The number of species is reduced to practi-cally one-half-at 300-500 m levels. The thinnest[thin-shelled] species drop out: Sceletonema co-statum and Nitzschia bicapitata, predominant inthe suspension from the 0-100 m layer. The300-500 m depths-are dominated by the thick si-liceous species: Thalassiothrix delicatula, Th.fraunfeldii, Planktoniella sol., Roperia tesselata,Thalassionema nitzschioides. According to ourdata there is no change in species-compositionof diatoms within the 300-4749 m depths. Thesurface layer of floor sediments is practicallyanalogous to that horizon, with regard to its spe-cies-composition. In the sediments, however,many other species were also found, in additionto the species in the suspension at 4779 [4749?]m depths.

The Boreal complex of diatoms in the0-100 m layer includes 34 species (suspensionfrom Subarctic waters it1 the northern PacificOcean and southern part of the Bering Sea).North-boreal and south-boreal species are dis-tinguished therein. The north-boreal complexis dominated by Deriticula seminae Simonsen etKanaya; smaller numbers of Asteromphalus ro-bustus Castr., Thalasslothrix iongissirna Cl. etGrun. are also found. The ,south,-boreal groupcontainsCoscinocliscns,radiatus Ehr., Chaeto-ceros messanen,sis Castr., Ch. concavicornis Mangin.

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The number of species decreases radically,beginning at 300 m. At 300-500 m and 1000-2000 m, this number is one-eighth of what it is •

in the surface layer. In deeper, horizons (300-2000 m) the diatoms are mainly north-borealDenticula serninae and Thalassiothrix longissirna.The south-boreal Thalassionema nitzschioides and Pseudoeunotia doliolus are found togetherwith them. There are more diatom species insediments than in suspension, although it wouldseem that the radical decrease in their numberin deeper horizons ought to be reflected in thesediments. A possible explanation here is inthe relatively short span of time represented bythe sample of diatom flora in suspension.

The Subarctic complex of diatoms asrepresented by the suspension sampled in Ana-dyr Bay includes 13 species. The dominants areArctic-boreal: Thalassiosira nordenskiOldii Cl.,Fragilaria oceanica Cl., Fr. cylindrus Grun.,Chaetoceros subsecundus Hust., the total ofwhich accounts for 60-70% of the total numberin the suspension from the surface horizon.

Up to 50% of species known to be present inthe surface horizon are preserved in the surfacelayer of seafloor sediments and in the water lay-er next to the floor, indicating a poor state ofpreservation of diatoms inhabiting costal watersof the Bering Sea.

The participation of diatoms in the formationof sediments is contingent upon the resistance ofdifferent species to the solvent action of the wa-ters. Some species are dissolved soon aftertheir death, but others reach the floor undis-solved. Two fundamental complexes of dia-toms are recognizable on the basis of theirresistance to solution: the neritic and oce-anic complexes.

The neritic complex of diatoms is agrouping of species distinguished mainly 133i apoor state of preservation. Their thin weaklysilicified valves are easily soluble. Their popu-lation peaks belong in the 0-100 m layer in Ant-arctic and Subarctic zones inhabited by neriticdiatoms. Their numbers in the depths are one-third of those found at the surface. To.some,ex-tent it is for that reason that sediments in Ana-dyr Bay and coastal areas of Antarctica containfew diatoms.

The oceanic complex of diatoms is agrouping of species characterized by a high de-gree of preservation, with their losses duringsettling not more than 30%. The numbers of oce-anic species found in the sediments are analo-gous to such numbers at the surface, or evenlarger.

New data supplement the earlier view with re-gard to the state of preservation of diatoms be-longing to different groups, a subject very im-portant for understanding the role of differentdiatoms in accumulation of siliceous sediments.It is known that the size and degree of silicifica-tion are smaller in neritic than in oceanic spe-cies. Consequently the former are not as im-portant as the latter in accumulation of siliceoussediments. Table 1 is presented here by way ofconfirmation of this statement, although it refersto the Indian Ocean sector of Antarctica.

The diatom count in the clayey-diatomaceoussediments on the shelf, in Olaf Prydz Bay, ishigher by 3.5-24.3 million cells/gram than inthe deepwater diatomaceous silts, in open ocean.However, amorphous silica content of the latterproved 1.5-3 times as high as of the clayey-dia-tomaceous silts. Dependence of amorphous sil-ica content of the sediments on the size and de-

TABLE 1. Participation of certain oceanic and neritic diatoms in accumulation of amorphous

silica in floor sediments

Coastal Areas of Ocean Open Areas of Ocean

StationNo. andcoordi-nates

Type of.sedi-ment

cn"E m0 4 -.

- ----. a..)as4 5--' .-'' 0 9io u C.

-.1 z a,o 0 ■•■-+

....,

••

f:,•5E be.t,cv0Cl)

Neriticflora

-

Size ofdia -dia -toms, i.t

4--, bDStation

andcoordi-nates

Type of

mse

ednit-

QCm

2 t'o 5as ----. a>'5 4' 59., ,.,Tj ;€3.c_, ?,

.2 't

._ d•a.'65 b,&,

c,

p

Oceanicflora

Size ofdia-

toms, 1.1

Z Z

189(69°17'S75.45,0

'

Clayey-diatoma-

ceoussilts

41. 6 13.9 89* 3-25177

(60°02'S,77°211E)

Diato-maceous

silts38. 1 40. 14 86% 50-82

190(68°42'S74°02'E)

Clayey-diatoma-

ceoussilts

111. 0 44.1 9-25211

(58° 16'S56°54'0

Diato-maceous

silts85.7 70.8 73.8% 50-82

*% of total diatom count in sample

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gree of silicification of the diatom shells is evi-dent accordingly.

LATERAL DRIFT OF DIATOMS DURINGSETTLING TO OCEAN FLOOR'

The extent of lateral drift of the valves ofdead diatoms during their settling to floor -sedi-ments may be appraised in suspension collectedat the surface and also from different depths.

The question may be answered only by thor-ough analysis of the species-composition of dia-toms in surface suspension and at differentdepths. It was in this very way that species-composition of diatoms was investigated in Ana-dyr Bay, Ross Sea, and in deepwater areas ofthe southern and northern parts of the PacificOcean. In cross-comparison of the results, itshould be borne in mind that neritic species. arenot as well preserved as oceanic species. S.orrieof the neritic species known to exist in the upperhorizons may not be found in the floor sediments.,

On the Bering Sea shelf, in the area of Sta-tions 1545, 1547 , (fig. 11), the plankton is domi-nated by neritic species: Thalassiosira norden-skihldii Cl., Fragilaria oceanica. Cl., and Chae ,-,tocetoS Subseturidua Hust. The same specieswere dominant also at the 100 m level. The dia-tom content at the 100 m level, .Station 1547, Waseven larger than at the surface because of accu-mulation of settling Spores Of Chaetoceros fur-cellatus Bail.- arid Ch. subsecundus Hust.

According to A. P. Zhuze's data (1957, 1960),the 'species here enumerated were found in abun-dance in sediments Of Anadyr Bay —"proof' that,in sediments of the Bering Sea shelf; diatoms'are buried not far away from where they live inthe plankton.

Oceanic diatoms are the planktonic dominantsin the deepwater part of the Bering Sea, Station1468, 3750 m depth (fig: . 12): Denticula.seminae,Asterornphalus robustus-Castr., Thatassiosira'excetitrica'Cl:, Thpaeifica Jonsei. CosdinodiS4cLis margingus Ehr.; Thalassiothrixlongissirn' aCl. et Grim. -Arnong . theneritic species,. Chaeto -

ceros furcellatus Bail., Fragilaria oceanica Cl.,and ThalassiosiranordenskiOldii 'Cl. were noted.As a whole; nerItie species accounted for 35% ofthe total diatom tount. 'However, none at allwere found between 500 m and 2000 ,rri. The 3000-3600 m layer was dominated by the Same oceanicdiatoms typical of surface waters.

In the oceanic zone of the southern PacificOcean, Station 385 (2320m depth); in the 0'25 mlayer (fig. 13) in line with the. diatomaCeous silts,the dominants were the oceanic species: Fra-gila.riaPSig..a.ntketica.'HI.I.t.-(45'47%); .Coscino.,discus Dactyliosolen'antarc-ticus Castr., , Thalassidsira gracilis, Hust.,'Thalassiothrix antarcticd CL et Grun. Their sumaccounted - for:92-95% of the total diatom count.In the depths, the species-composition corre-sponded to the diatom flora at the ocean surface.In floor sediments at the same ,station,- the verysame Fragilatiopsis - antarctica was dominant,with 45-50% share of the total diatom cell counttherein.

In the suspension from deep horizons at sta-tions situated over the shelf, the continentalslope, and over the deepwater areas of the Ber-ing Sea and Pacific Ocean, the species-composi-tion of diatoms retained the same features as inthe active layer of the ocean. No members aliento the given zonal diatom flora of the ocean orsea could be found in'the suspension from thedepths down' to.the horizon nearest the floor.

Our research confirms the earlier conclusion

8

200

••••••

1;3

,%, 13O

cz,L. 0

C.z

7=6 cmis

,

r702 17:'2M6 ..p%2E 4Es=35 =777FIGURE 11. Species and numbers, of d iatoms:: at different depths, continental shelf,

Bering Sea (Station 1545), million cells/a3.

- 0 - 0.01; 2 - 0.01 - 0.1; 3 - 0.1-1; 4 - 1-10; 5 - 10-100;::6 - 100;' -7 7 floor,

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., ,......a.

.! A , c". `'., t%

•

tO 'k' ''''',,,• 14 1.4 411 ;f2 % .k rij'''.4 . 4 ..,4

CA, a L.. - . . ,.,3N ki

•

SI. ,z1 .: .. ■ . Pt, 1 ig... ii 4'im ' . g . z,: z . ,,, - " e.:. . ,., ,. ., . , e 4°—...... -,......_ .. ---. .,......, ...._ _ _ r.. ea csb k e 4 . .4. I z I " . "414 wa .4 t4 .4 .4 .4 of. fy cy fy ,..c...e. .e.: ..ys ..e: ....."e •eZ Ca ,..) r.... C..I C.) 45 e...a ej sy, fyi 1,..z 1.,....-• 4,-:: ,....- 1: --• j: .C.

Mill0 . . .

N urn be r 'of diatoms,thousand cells/m3

0 ZOO 400 OM

0.G. KOZLOVA AND V.V. MUKHINA

FIGURE 12. Species and numbers of diatom,s, in deep,waters of Bering Sea(Station 1468) .

0-0.01; 2 - 0:.01.-0,1;' 3 7 0:1'1; 4 - 1-10; 5 - 10-100; 6 - 100; 7 - floor.

t.t3

.4 .4• ..... V. 1:3 174

.... t.•.., ...... 7....."-• c. lcs .... ICI

Ei % -........ 3.1L. ..

-3 e)....Z3 , C. , b. e. .4 ...... .....,

.".. .c'.3 Ca ta...'-.. 4c, ,......._.. CI

Ls .4 "3 ....%-4 v3 - --,,. F21, cz,

..3 .e 2.-Z c. ez .'::.2-....:,53 '41 2 4' [is,

q., e.,ct ckl -e,, ea -e, ea ea sy y, y Z.-, -.-. ea ey

Y -e -e -e ae.es e. Cm ' t. ,

200300 -

ea

Number of diatoms,4 4 million ce11s/rn 3,

8 5 10.15 20 25 30 35 48

006

?XVFIGURE 13. Species and numbers of diatoms, from surface to depths, in deep-water areas in

southern part of the Pacific Ocean (Station 385).

Key same as in Figure 12.

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of A. P. Zhuze and G. I. Semina (1955), A. P.Zhuze (1957, 1960) with regard to close corre-spondence between species-composition of dia-tom complexes in the plankton and surface layerof sediments of the Bering and Okhotsk' seas.

Determinations of species-composition of di-atoms in suspension along the two traveraes,a1.-low us to conclude that the lateral drift of-dia-toms, from the areas they inhabit [to areas`Wherethey are buried transl.], is relatively small.-The same results were obtained for coastaHoce ,

anic areas of the-Indian Ocean sector of Antarc-tica (Kozlova, 1964).

Our research demonstrates a close relation-ship of the species-composition of diatoms insurface waters, in the depths, and in floor sedi-ments at every station. The differences consistin partial solution of certain thin-shelled andmoderately silicified diatoms, not found eitherin the depths or in the sediments, for that rea-son.

REFERENCES

Hasle, G. R., 1959, QUANTITATIVE STUDY OFPHYTOPLANICTON FROM EQUATORIAL PA-CIFIC: Deep-Sea Research, v. 6.

Kozlova, 0. G., 1964, Diatomovyye vodorosliIndiyskogo i Tikhookeanskogo sektorov Ant-arktiki [DIATOM ALGAE OF INDIAN AND PA-CIFIC OCEAN -SECTORS OF ANTARCTICA]:Izd. Nauka.

L sitsyn A. P., 1955, Nekotoryye dannyye o ras-predelenii vzveshennykh chastits v vodakhKurilo-Kamchatskoy vpadiny [CERTAIN DATAON DISTRIBUTION OF SUSPENDED PARTI-CLES IN WATERS OF KURILES-KAMCHAT-KA DEPRESSION]: Trudy Instituta okeano1O-gii, AN SSSR, v. 12.

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