are honeycombed with interconnecting pores and channels.There appears to be a labyrinthine system in some floes which isfreely connected to the underlying water column. Krill (Eupha-usia superba) and large decapods (Gennados pp.) were observedto enter the interior regions of the ice through those channels.This behavior by pelagic invertebrates may relate both to use ofthe ice as a refugium and as a grazing area where food isabundant. These floes may act as small island-like ecosystemswhere the biological activities of all trophic levels—algae, bacte-

ria, protozoans, amphipods, decapods, krill, birds, and seals—are concentrated within the pack ice.

We would like to thank Captain Haines and crew on theMelville, Captain Honke and the crew on the Westwind, and ITT

Antarctic Services for their support. The direct field assistanceand untiring efforts of Robert Wilson and Lt. J. Leonard wereparticularly valuable. Support was provided by National Sci-ence Foundation grant DPP 82-18752 and by the National MarineFisheries Service.

Growth rates, distribution, andabundance of bacteria in the ice-edgezone of the Weddell and Scotia Seas,

Antarctica

M.A. MILLER, D.W. KREMPIN,D.T. MANAHAN, and C.W. SULLIVAN

Marine Biology Research SectionDepartment of Biological SciencesUniversity of Southern California

Los Angeles, California 90089-0371

The overall hypothesis of the Antarctic Marine EcosystemResearch at the Ice-Edge Zone (AMERIEZ) project is that themarginal ice zone is associated with an oceanographic frontwhere biomass and biological productivity are enhanced. Ourspecific goal was to examine the hypothesis that bacterial pro-duction contributes significantly to enhanced productivity andbiological activity in the marginal ice zone. To test our hypoth-esis, data were collected on board the iIv Melville and USCGCWestwind from 5 November through 2 December 1983 at 59stations in a 70,000-square-kilometer region of the Weddell andScotia Seas (See Ainley and Sullivan, Antarctic Journal, this is-sue). The vertical and horizontal distribution, activity andgrowth rates (u) of bacteria were examined in the sea ice andwater column. In addition, cores of sea ice were obtained atselected Westwind stations for analysis of nutrients, biomass,and metabolic activities of the sea-ice microbial community. Toassess the levels of potential heterotrophic substrates present,we made measurements of naturally occurring dissolved freeamino acids (DFAA) using newly developed techniques involv-ing high-performance liquid chromatography (HPLC).

The coupling between primary and secondary (bacterial) pro-duction was also examined.

We looked for a correlation between water column fluores-cence and bacterial biomass. In vivo fluorescence at the surfacewas measured during a 3-day synoptic presurvey of the regionto the north of the ice edge. A Turner Designs flow-throughfluorometer calibrated with extracts of discrete phytoplanktonsamples (Strickland and Parsons 1972) taken every 20 kilo-meters along the cruise track was used to generate a chlorophylla surface map of the study area. Surface chlorophyll a con-centrations ranged from 0.03 to 7.49 milligrams per cubic meter

being greater to the west, as well as toward the ice edge to thesouth, as anticipated.

At each station, Niskin bottles were used to obtain discretesamples through the upper 200 meters of the water column forfluorometric analysis of chlorophyll a (See Nelson, Smith, andGordon, Antarctic Journal, this issue). Simultaneously, replicatesamples were taken and preserved for epifluorescence micro-scopy (Hobbie, Daley, and Jasper 1977) to obtain correspondingbacterial cell number and biomass distribution. A four-foldincrease in both bacterial cell numbers and biomass was ob-served along a combined Melville and Westwind transect whichextended from 120 nautical miles into the pack ice to 160 nauticalmiles north of the ice edge. Bacterial cell numbers and biomassintegrated through the water column to a depth of 150 metersranged from an average of 7 x 1012 cells per square meter (100milligrams of carbon per square meter) at the southernmostWestwind stations to an average of 33 x 1012 cells per square (400milligrams of carbon per square meter) to the north.

Along this same transect 3 tritiated-thymidine incorporationrates suggested maximum bacterial growth rates (Fuhrman andAzam 1980, 1982) in the upper 50 meters of the water column inthe region most recently uncovered by the receding ice, justnorth of the ice-edge zone (figure 1). The thymidine incorpora-

STATION NO.1514 16 171819202136 37 383940414243

50

I

0- 1000

150

200 400 600DISTANCE (KM)

Figure 1. Oceanographic section of western transect in AMERIEZstudy area. Isopleths indicate bacterial cell production rates in unitsof 106 cells per liter per day. Distance is along the combined West-wind/Melvilecruise track north of 62°43.0". (See Ainley and Sullivan,Antarctic Journal, this issue, for station map.) ("M" denotes meter;"KM" denotes kilometer.)

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lion rates steadily declined by two orders of magnitude to thesouth and by one order of magnitude to the north of the ice-edge zone. Growth rates ranged from 0.02 per day deep withinthe pack ice to 0.4 per day just north of the ice-edge zone,declining to 0.03 per day further north in the Drake Passage.These growth rate estimates fit within the range calculated forother southern ocean regions (Fuhrman and Azam 1980; Hans-on et al. 1983:0.001-0.45 per day, mean growth rate was 0.09 perday for 21 samples).

Surface DFAA concentrations along this north-south transectwere low (about 10 nanomoles total). HPLC tracings from threestations demonstrate the maximum differences that were ob-served among all samples (figure 2). Westwind station 22, justnorth of the ice edge region in an area of high phytoplanktonbiomass (see Nelson, Smith, and Gordon, Antarctic Journal, thisissue), had the highest DFAA concentrations found at any sta-tion. Glutamic acid and an unidentified peak (labelled "?") werecharacteristic of the bloom region and did not appear in otherareas. The low DFAA concentrations encountered could be theresult either of low DFAA production rates, or rapid DFAA uptakeby heterotrophs.

Epifluorescence microscopy of samples prepared from sevensea ice cores revealed a unique vertical distribution of bacterialnumbers, biomass, and cell size frequency for each ice floe(figure 3). These results will be compared to a variety of otherphysical, chemical and biological measurements to investigatethe cause of such variation. The range of bacterial biomasspresent in 1-2 meters of sea ice is from 6.15-99.6 milligrams ofcarbon per square meter ice, the range of bacterial biomass inthe 100 meters of the water column below the ice is from 24 to97.5 milligrams of carbon per square meter. Thus the sea ice is ahabitat for a highly concentrated microbial community. We pro-pose that a Microheterotroph-based food web is associated withthe Weddell Sea pack ice similar to that proposed for McMurdoSound (Sullivan and Palmisano 1984). This proposition is basedon the abundance of bacteria within sea ice and ice pore water,and the observation of large numbers of bactivorous protozoanssuch as flagellates and ciliates, which are present in the sea-icemicrobial community (see Garrison, Buck, and Silver, AntarcticJournal, this issue).

The authors would like to thank L. Geoff Graue, JohnDmohowski, and the captains, crew, and resident techniciansof the it/v Melville and USCGC Westwind. Their assistancethroughout was invaluable in making the cruise a success.

This research was supported by National Science Foundationgrant DPP 82-18752.

Hanson, R.B., H.K. Lowery, D. Shafer, R. Sorocco, and D.H. Pope.1983. Microbes in Antarctic waters of the Drake Passage: Verticalpatterns of substrate uptake, productivity and biomass in January1980. Polar Biology, 2, 179-188.

Hobbie, J.E., R.J. Daley, and S. Jasper. 1977. Use of Nuclepore filters forcounting bacteria by fluorescence microscopy. Applied and Environ-mental Microbiology, 33, 1225-1228.

Nelson, D.M., W.O. Smith, and L.I. Gordon. 1984. Phytoplanktondynamics of the marginal ice zone of the Weddell Sea: November andDecember 1983. Antarctic Journal of the U.S., 19(5).

Strickland, J.D.H., and T.R. Parsons. 1972. A practical handbook of sea-water analysis (2nd ed.). (Bulletin 167.) Ottawa: Fisheries ResearchBoard of Canada.

Sullivan, C.W., and A.C. Palmisano. 1984. Sea ice microbial commu-nities: distribution, abundance and diversity of ice bacteria inMcMurdo Sound, Antarctica, in 1980. Applied and Environmental Mi-crobiology, 47(4), 788-795.

)G-11 u 4Jk#19

References

Ainley, D. G., and C. W. Sullivan. 1984. AMERIEZ 1983: A summary ofactivities on board n/v Melville and USCGC Westwind. Antarctic Journalof the U. S., 19(5).

Fuhrman, J. A., and F. Azam. 1980. Bacterioplankton secondary produc-tion estimates for coastal waters of British Columbia, Antarctica, andCalifornia. Applied and Environmental Microbiology, 39(6), 1085-1095.

Fuhrman, J. A., and F. Azam. 1982. Thymidine incorporation as a meas-ure of heterotrophic bacterioplankton production in marine surfacewaters: Evaluation and field results. Marine Biology, 66, 109-120.

Garrison, D. L., K. R. Buck, and M. W. Silver. 1984. Microheterotrophs inthe ice-edge zone. Antarctic Journal of the U.S., 19(5).

BLANK

NH

Figure 2. High-performance liquid chromatographic analyses ofamino acids and ammonia in samples taken from three stations.Each analysis Is of 400 microliters of 0.2-micrometer-filtered sea-water taken from a surface hydrocast. The bottom tracing (Blank) isan analysis of 400 microliters of HPLc-grade distilled water. The highlevels of contamination seen in this tracing are due to the fact thatsolvents, etc., had to be prepared and placed aboard ship severalmonths prior to their use. ("Glu" denotes glutamic acid; "nM' de-notes nanomole; "NH" denotes ammonium.)

104 ANTARCTIC JOURNAL

CORE H COREICE

SURFACE

0-13

13-28I

28-47Ui

LiJ47-710C.)71-89

89-114

51010" BACTERIA / M3

15 3010" BACTERIA /M3

0-20

29-620

62-98I-a.98-118Ui

118-144UiCr 144-1620

162- 180

0-13

13-28I

28-42LU0

47-TI0o71-89

89-114

ICESURFACE

0-20

29-62

62-98

a.I-

98-1180

118-144cro 144-1620

162-180

510 50100150

mgC/M3mgC/M3

Figure 3. Vertical profiles Indicating bacterial cell numbers and biomass concentrations and standing crops for two sea ice core samples. Icecores H and K were collected at Westwind stations 8 and 13, respectively (see Ainley and Sullivan, Antarctic Journal, this issue, for station map).("MgC/M 2" denotes milligrams of carbon per square meter; "mgC/M 3" denotes milligrams of carbon per cubic meter.)

Phytoplankton dynamics of themarginal ice zone of the Weddell Sea,

November and December 1983D. M. NELSON and L. I. GORDON

College of OceanographyOregon State UniversityCorvallis, Oregon 97331

W. 0. SMITH

Graduate Program in EcologyUniversity of Tennessee

Knoxville, Tennessee 37996

During November and early December of 1983 we conducteda coordinated two-ship study of the phytoplankton and nu-trient dynamics of the marginal ice zone of the Weddell Seaaboard the oceanographic research vessel! RIv Melville and theUSCGC Westwind. This work was performed in connection withthe National-Science-Foundation-supported Antarctic MarineEcosystem Research at the Ice-Edge Zone (AMERIEZ). TheMelville, with the larger scientific party and greater samplingcapabilities, directed its efforts at the open-water areas to thenorth of the ice edge, while the icebreaker Westwind workedprimarily in areas of significant ice cover. Data collected at everystation included nutrients (nitrate, nitrite, ammonium, silicicacid, and phosphate), chlorophyll, particulate carbon and nitro-gen, and biogenic and mineral particulate silica. At most sta-tions carbon-14, nitrogen-15, and silicon-30 tracer experimentswere performed to measure rates of production of biogenic

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