ARCTIC VOL. 35, NO. 4 (DECEMBER 1982) P. 485-503 Relative Contributions of Ice , , and Benthic Microalgae to in Nearshore Regions of the Beaufort Sea RITA HORNER’ andG.C. SCHRADER * ABSTRACT. Phytoplankton, ice algae, and benthic microalgae are the three sources of primary production in the western Beaufort Sea in winter and spring. Phytoplankton levels in winter are low with chlorophyll a levels near the limit of detection. Microflagellates are the most abundant organisms present in the water column along with a few diatoms. Low chlorophyll a, standing stock, and primary productivity continue into June when the ice breaks up. Cells are present in from the time it forms in the fall and are generally scattered throughout the ice thickness. Microflagellatesare the most abundant organisms, but some diatoms, mostly pennate species, are also present. Cells concentrate in the bottom few cm of ice during March-April in response to increasing light levels. Growth continues until late May-early June when maximum production and standing stock occur. Benthic microalgal production was barely detectable in spring although chlorophyll a levels were high, perhaps left from the previous production season. Light is apparently the major factor controlling production in the spring, with the ice algae being able to take advantage of increasing light levels early in spring. This community shades both the water column and benthos so that production in those habitats does not increase until after the ice algae disappear in early June, but the ice community may be inhibited by layers of sediment in the ice. During this study, the ice algae provided about two-thirds and the phytoplankton one-third of the spring primary production; the benthic community contribution was negligible.

Key words: western Beaufort Sea, phytoplsnkton, ice algae, benthic microalgae, primary productivity, chlorophyll a, standing stock, species present, environmental factors

RÉSUMÉ. Le phytoplancton, les algues glaciales et les microalgues benthiques sont les trois sourcesde production primaire dans l’ouest de la mer deBeaufort en hiver et au printemps. Le niveau dela chlorophylle a ttant pres de la limite de dttection. Lesmicroflagellts sont les organismes les plus abondants dans la colonne d’eau, avec quelques diatomtes. Le niveau peu tlevt de chlorophylle a, la ptnurie de biomasse et une productivité primaire basse continuentjusqu’enjuin, lors de la ptriode dedtglacement. Des cellules sont prtsentes dans la glace marine dès sa formation B l’automne et sont gtnéralement tparpilltes dans toute I’tpaisseur de la glace. Les microflagellts sont les organismes les plus abondants, mais certaines diatomées, surtout les espèces penntes, sont aussi prtsentes. Les cellules se concentrent vers les quelques centimètres inftrieurs de la glace au cours de mars et d’avril, en rtponse au niveau augmentant de la lumiere. La croissance continue jusqu’à la fin-mai et le dtbut-juin, la production et la biomasse atteignant leur point maximalàce temps. La production de microalgues benthiques pouvait à peine être discernte au printemps, bien que le niveau de chlorophylle a ttait élevt,peut-être en tant que vestige de la saison anttrieure de production. La lumiere semble être le facteur principal contrôlant la production au printemps, les algues glacialespouvant profiter de l’augmentation du niveau de la lumière durant cette saison. On trouve cette communautt dansla co- lonne d’eau et aussi dans le benthos, desorte que la production dans ces habitats n’augmente qu’aprks la disparition des algues glaciales en debut-juin, mais la communautt glaciale peut être arrêtte par des couches de stdimentsdans la glace. Au cours de cetteetude, les algues glaciales fournissent environ deux tiers, et le phytoplancton environ un tier de la production primaire au printemps; la contribution de la communautt benthique est ntgligeable.

Mots clts: l’ouest de la mer de Beaufort, phytoplancton, algues glaciales, microalgues benthiques, productivitt primaire, chlorophylle a, biomasse prtsente, facteurs du milieu Traduit pour le journal par Maurice Guibord.

INTRODUCTION The benthic microalgae, primarilypennate diatoms, live The sources of primary production that support the ecosys- on and among sand grains on the sea floor. This commu- tem in the nearshore western Beaufort Sea are not well nityis probably present in summer, although solitary, known. Three components are apparently available: ice motile pennate diatoms may be present in spring, some- algae, phytoplankton, and benthic microalgae. Of these, times forming brownish patches in the lee of sediment thephytoplankton is perhapsthe best known. This ripples. In the Chukchi Sea, a dense mat of filamentous community, composed of diatoms, , and diatoms may form in someareas in summer (Matheke and microflagellates, occurs in the water column from about Horner, 1974). The benthic microalgal community has not the time of ice breakup through the summer. been studied in the nearshore Beaufort Sea in summer. The ice algal community lives and in on the underside of Our objectives were to assess the winter density distri- sea ice and is present primarily during the spring, usually bution and environmental requirements of phytoplankton April through earlyJune, but cells are also present in the in the nearshore Beaufort Sea and to undertake an inte- ice throughoutthe winter and there are reports of a layer of grated study of ice algae, phytoplankton, andbenthic healthy, active cells in the ice in November(Hsiao, 1980; microalgaeproduction to providecomparisons among these Schell, pers. comm.). This community is composed prima-habitats and allow us to determine the relative importance rily of pennate diatoms and microflagellates, but centric of these communities during the spring growing season. diatoms and dinoflagellates mayalso be present, usually in Sampling was done f6r3-4 day periods in November 1978 low numbers. and February, March, andMay 1979 in Stefansson Sound

‘4211 N.E. 88 Street, Seattle, Washington 98115, U.S.A. 220027 - 13 Drive S.E., Bothell, Washington 98011, U.S.A. 486 R. HORNER and G.C. SCHRADER

(70"19'N, 147"34.4'W), and intensively from early April solution. The samples were incubated in situ for 3-4 hr in through mid-June 1980 in the Beaufort Sea just north of clear plastic tubes suspended from the bottom of the ice. Narwhal Island (70"24'N, 147'31.1'W) (Fig. 1). Dark bottles were incubated in a darkened plastic tube suspended at 0 m. Following incubation andretrieval, the samples were placed in a black box in an ice chest until they were filtered on shore. Primary productivity of the ice algae was measured using a combination incubation chamber-sampler (Clasby et al., 1973). Two light and one dark chamber wereplaced inthe ice by SCUBA divers and the chambers were inoculated with ca. 5 pCi Na2HI4CO3 solution. The dark chamber was removed from the ice immediately after inoculation, capped, and suspended from an ice pitonattached to the underside of the ice. Aftera 3-4 hr incubation period, a heavy metal spatula was used to chip away the ice from around the chamber and sever the top of the core. The sample wasretained in the chamber by a core cap. Theice cores were transferred to 250-ml glass jars and preserved with 5 ml 4% buffered formaldehydeto prevent further uptake of isotope by the algae. Additional ice cores were collected for standing stock, FIG. 1. Location of study sites in Stefansson Sound (1978-1979)and off plant pigment, nutrient, and salinity determinations. All Narwhal Island (spring 1980). cores were transferred to 250-ml glass jars and the stand- ing stock sample was immediatelypreserved with 5 ml 4% buffered formaldehyde. The other cores were placed in an METHODS ice chest for return to shore. During this study, we have determined primary produc- At the shore laboratory, the water and ice productivity tivity, plant pigments, standing stock (cell numbers), and samples were filtered through 25 mm, 0.45 pm Millipore species composition of the ice algae, phytoplankton, and filters, rinsed with 5 ml 0.01 N HCl and 5 ml filtered sea- benthic microalgae; we have also measured environmen- water, and placed in labeled scintillation vials. Water and tal parameters including light,temperature, salinity, nutri- ice samples to be used for plant pigment determinations ent concentrations, and snow cover, but not allparameters were filtered as above. Before the MgC03 and filtered were determined during each sampling period. We include seawater were added, filtration was stopped and the fil- an extensive description of our methods particularly for trate was poured into two 125 ml polyethylene bottles for the ice algae because of the difficulties encountered in nutrient and salinity determinations. The nutrient sample studying this community and because the wide variety of was frozen immediately. methods used inthe past has made comparisons between areas difficult. Narwhal Island Water samples were collected as previously described, Stefansson Sound except that depths were just below the ice (0 m) and 1 m Water samples from near the bottom of the ice (0 m) and above the bottom (7 m). Primary productivity experiments from near the sea floor (4.5 m) were collectedby lowering were done as in May 1979. The remainder of the water plastic water sampling bottles through holes cut in the ice. samples, usually 2 1, was kept in a darkened ice chest and Subsamples for phytoplankton standing stock determina- returned to the shore laboratory where it was thoroughly tions were poured into 250-ml glass jars and immediately shaken. We preserved250 ml with 10 ml4% buffedformal- preserved with10 ml4% formaldehyde buffered with sodiumdehyde for standing stock analysis. One literof water from acetate. Theremainder of the sample waskept cool until it each sampling depth was filtered through a 47 mm, 0.45 could befiltered on shore. One totwo liters of water were pm Millipore filter for plant pigment,nutrient, andsalinity filtered through 47 mm, 0.45 pm Millipore filters for plant analysis as described above. pigment determinations. Three drops of a saturated solu- The ice algae were collected usinga re-designed sampler- tion of MgC03 wereadded near the end of the filtration incubation chamber (Schrader et al., 1982).Following process and the filter tower was rinsed with filtered seawater.incubation, the samples were immediately transferred to The filters were folded and frozen in a desiccator. 250-ml opaque glass jars and two drops of 0.4% HgC12 In May 1979, primary productivity was determined on were added to kill the cells and prevent further uptake of ice andwater samples. Subsamples of water in 60-mlglass the isotope. Four additional ice cores were collected for reagent bottles, two light and one dark bottle for each determination of standing stock, plant pigments, nutrient depth, wereinoculated with ca. 5 pCi Na2HI4C03 concentrations, and salinity. All cores were transferred to PRIMARY PRODUCTION INTHE NEARSHORE BEAUFORT SEA 487

250-ml glass jars and kept inthe dark in an ice chest until Downers Grove, IL) with Aquasol(New England Nuclear, processing on shore, usually within 2-3 hr. The additional Boston, MA) as the scintillation cocktail. Carbon uptake cores were taken after the 14C incubation period to mini- was calculated using the equation in Strickland and Par- mize the time between collecting and processing. sons (1972). Chlorophylla and pheopigments were deter- Primary productivity and plant pigment cores were filteredmined using the fluorometric technique (Strickland and as before except that animals > 1 mm were removed from Parsons, 1972). Nutrient samples wereanalyzed using the filter. The ice core to be used for standing stock deter- autoanalyzer techniques; salinity was determined with a mination was preserved with 10 ml 4% formaldehyde salinity bridge (Pavlou, 1972). buffered with sodium acetate. Standing stock samples were analyzed using a Zeiss Phytoplankton and ice algae primaryproductivity sam- phase-contrast inverted microscope and Zeiss counting ples werecounted using a PackardTri-Carb Liquid Scintil- chambers following the method of Utermohl (1931). In latibn Spectrometer (Packard Instrument Company, Inc., addition, portions of some ice algae samples were acid-

TABLE 1. Standing stock, plant pigment, primary productivity, nutrient, and salinity data from Stefansson Sound, Nov 1978-May 1979

Nutrient Concentrations Depth Standing Stock Chl a Pheo Prim Prod NO3 NOZ NH3 PO4 Si04 Salinity Date (m) (ce1ls.T'C.m-3.hr") X (mgIO4) (mg.m-3) (mg.m-3) (pg-atar') (%O)

8 Nov 78 0 2.6 0.06 0.07 4 1.4 9 0 2.4 0.02 0.12 4 1.8 0.02 0.12 10 0 0.06 0.06 4 0.06 0.08 11 0 0.05 0.04 4 0.05 0.05 12 0 0.06 0.07 4 0.04 0.06 13 0 0.06 0.05 4 0.04 0.06 14 0 0.07 0.05 4 0.04 0.05 15 0 0.05 0.06 4 0.06 0.06 16 0 4.6 0.06 0.05 4 4.6 0.06 0.05 15 Feb 79 0 3.6 0.02 0.07 4 2.2 0.01 0.04 12 Mar 79 0 4.6 0.01 0.03 4 3.4 0.00 0.02 13 0 0.00 0.02 4 0.01 0.03 14 ice* 1.5 x 10' 0.00 0.03 0 0.01 0.03 15 0 0.01 0.03 4 0.01 0.03 16 0 6.0 0.01 0.03 4 8.2 0.01 0.03 15 May 79 ice 2.87 4.32 1SO 1.35 0.14 2.68 1.38 19.90 18 ice 2.70 3.36 1.42 1.19 0.06 2.85 0.74 15.3 20.62 0 16.2 0.42 1.13 0.16 1.55 0.04 1.07 0.20 18.324.06 4 3.8 0.17 0.24 0.12 4.69 0.17 0.84 1.42 35.213.34 19 ice 2.53 2.83 0.31 1.24 0.05 1.87 0.50 21.02 15.9 0 0.67 1.OS 0.16 1.57 0.16 1.68 0.39 26.27 18.3 4 0.24 0.43 0.80 4.72 0.06 0.24 0.95 35.213.23 20 ice 8.9 3.01 1.99 1.42 0.76 0.06 2.66 0.46 14.120.56 0 20.8 1.19 0.89 0.11 1.01 0.05 1.04 0.24 16.6 24.53 4 3.6 0.23 0.33 0.26 4.46 0.16 0.79 0.91 34.813.43

*Standing stock, plant pigments, and primary productivity from the ice are given on a m-' basis. P m TABLE 2.Standing stock, plant pigment,primary productivity, nutrient, salinity, and light data from Narwhal Island, Apr-Jun 1980 m

Nutrient Concentrations Depth Light Standing Stockt Chl u Pheo Prim Prod NO3 NO2 PO4 NH3 Si04 Salinity Date (m) (% sfc)(mg~n'~) (cellsd) (mg CTIY~.~~") (pg-atd -I) (%d

10 Apr ice* 1.7 x lo8 1.2 0.1 0.14 10.6 0.13 1 .OS 25 34.50 0 1.2 x 108 0.1 0.1 0.01 10.1 0.07 0.01 1.27 22 35.21 7 0.1 0.0 - 10.6 0.10 0.00 1.30 23 35.71 14 ice 2.4 x lo7 0.05 10.3 0.10 0.75 1.08 24 33.73 0 3.9 x lo6 0.1 0.0 0.01 10.3 0.07 0.00 1.43 23 34.77 7 0.0 0.0 - 10.5 0.08 0.00 , 1.29 23 35.08 sed 0.7 1.5 17 ice 4.6 x lo6 0.4 0.1 0.03 10.6 0.10 1.12 4.06 23 33.83 0 1.4 x 107 0.1 0.0 0.04 10.5 0.06 0.01 1.33 23 34.91 7 0.0 0.0 - 10.6 0.09 0.00 1.32 24 35.26 sed 1.3 x 109 13.3 5.0 <0.01 19 ice 2.5 x lo8 0.4 0.0 0.08 10.3 0.07 0.59 10.50 24 34.02 0 2.2 x lo7 0.1 0.1 0.05 10.2 0.05 0.10 3.31 23 34.75 7 0.0 0.0 0.01 10.8 0.09 0.00 4.55 24 35.53 sed 2.7 x lo8 0.9 1.6 <0.01 24 ice 7.1 x lo8 2.4 0.2 0.07 9.9 0.11 0.69 1.17 23 32.58 0 1.2 x 107 0.1 0.0 0.04 10.2 0.04 0.05 1.63 23 34.24 7 0.1 0.0 0.01 11.0 0.09 0.00 1.49 24 35.31 sed 6.8 3.1 CO.01 29 ice 0.06 4.8 x lo6 0.0 0.0 0.02 10.3 0.13 0.77 1.03 24 31.65 0 0.02 2.8 x lo7 0.2 0.1 0.06 10.3 0.05 0.02 11 32 24 34.33 7 0.08 0.1 0.1 - 10.8 0.08 0.00 3.60 24 35.18 sed 1.4 1.5 - 2 May ice 0.65 5.6 x lo8 8.3 1.2 0.22 9.0 0.23 0.54 4.40 20 33.07 0 0.52 2.9 x lo8 0.2 0.1 0.01 10.0 0.07 0.14 15.63 24 34.38 7 0.21 0.1 0.0 - 10.7 0.08 0.14 25.26 26 35.32 sed 9.0 x lo8 9.5 5.8 - 5 ice 1.37 1.1 x 109 4.3 0.3 0.35 9.0 0.17 0.74 4.94 21 33.05 0 0.87 2.1 x lo7 0.3 0.1 0.01 9.7 0.06 0.06 1.49 23 34.44 7 0.20 0.3 0.2 - 10.8 0.08 0.01 1.39 24 35.59 sed 8.3 4.2 0.01 8 ice 0.81 6.9 x 107 2.2 0.3 0.77 9.6 0.28 0.76 1.13 23 32.63 0 0.49 4.9 x lo7 0.2 0.2 0.05 9.6 0.08 0.09 1.36 23 34.57 sa 7 0.24 0.0 0.0 - 11.0 0.07 0.08 1.49 24 35.71 X sed 3.0 x lo8 1.4 1.8 0.02 % 15 ice 0.64 9.3 x lo6 1.2 0.1 0.11 11.0 0.19 0.81 1.18 22 33.73 mz 0 0.37 2.8 x 108 0.1 0.1 0.07 9.5 0.07 0.21 1.90 22 34.54 P 7 0.13 0.3 0.1 - 10.5 0.08 0.15 1.52 24 35.45 B n sed 2.5 2.5 0.07 P 17 ice 0.74 2.5 0.3 0.24 10.5 0.10 1.48 1.49 23 33.05 - 0.16 1.34 22 34.34 0 0 0.55 2.1 x lo7 0.3 0.1 9.3 0.07 v1 7 0.17 0.1 0.1 0.06 10.1 0.08 0.06 1.36 23 35.05 0 X sed 6.1 3.7 - P 32.65 9 20 ice 1.48 1.6 x lo8 3.9 0.5 0.51 11.9 0.21 0.64 1.27 23 U 0 0.69 9.8 x 107 0.3 0.1 0.07 9.4 0.09 0.12 1.74 23 34.03 m 7 0.24 0.1 0.1 - 10.1 0.10 0.02 1.41 24 34.90 P TABLE 2 continued z Nutrient Concentrations 52 Depth Light Depth Standing Stockt Chi a Pheo Prim Prod No3NH3 NO2 Po4 Si04 Salinity * (% ”) Date (m) sfc) (celkd) (mg.m”) (mgm”) (mg C.m”.hr”) (pg-at.[ (%d w4 sed 0.7 1.o - 22 ice 1 .os 7.9 x lo8 14.4 1.5 0.71 10.7 0.19 0.77 1.36 19 31.60 U 0 C 0.72 1.8 x lo8 0.2 0.1 0.21 9.0 0.08 0.04 1.40 22 33.74 n 7 0.1 0.1 0.09 9.6 0.10 0.00 1.42 23 34.52 sed 3.0 x 109 14.2 7.7 - 3 24 ice 8.2 x lo8 11.1 0.3 0.55 14.0 0.28 1.03 2.06 21 31.02 z 0 8.1 x 107 0.4 0.1 0.13 8.9 0.08 0.02 1.60 22 33.63 52 7 0.1 0.1 0.13 9.6 0.09 0.02 1SO 23 34.33 2 sed 7.2 5.2 - m 26 ice 0.87 1.0 x 109 13.5 1.5 0.38 16.6 0.20 1.52 1.89 22 30.05 3 0 0.36 5.3 x lo7 0.8 0.2 0.09 8.9 0.20 0.00 4.36 22 33.60 > 7 0.20 0.2 0.1 - 9.3 0.08 0.00 3.94 23 33.88 sed 6.1 2.9 - 0 29 ice 1.74 8.5 x lo8 12.7 1.6 2.64 9.6 0.13 0.54 1.46 20 32.32 mrn 0 0.81 7.0 x 107 0.2 0.1 0.06 9.1 0.09 0.00 1.36 23 34.12 m 7 0.59 0.1 0.1 - 9.5 0.09 0.00 1.40 23 34.38 F sed 4.0 x lo8 0.9 0.8 0.02 C 31 ice 2.00 1.2 x 109 26.5 3.2 0.77 17.4 0.32 1.20 1.53 20 32.88 8 0 0.94 6.3 x 107 0.5 0.2 0.04 9.1 0.09 0.03 1.41 23 34.21 2 7 0.27 0.1 0.1 - 9.4 0.09 0.00 1.29 23 34.35 cn sed 16.5 6.0 <0.01 F 2 Jun ice 1.86 8.5 x 10’ 20.4 3.4 0.36 18.0 0.17 0.87 1.68 22 3 1.52 0 0.50 6.3 x lo7 0.3 0.2 0.05 8.7 0.09 0.03 1.33 22 34.03 7 0.19 0.1 0.1 0.03 9.7 0.09 0.01 1.27 23 34.50 sed 10.9 5.6 0.02 5 ice 1.30 6.7 x 10’ 12.0 2.0 0.46 16.1 0.18 1.08 2.28 22 31.66 0 0.56 1.5 x lo8 0.07 8.2 0.09 0.11 1.11 21 33.66 7 0.14 0.2 0.1 0.16 10.4 0.10 0.07 16.95 25 34.78 sed 8.0 x 10’ 28.7 6.6 <0.01 7 ice 4.01 6.6 x 10’ 17.2 2.7 2.60 9.7 0.22 1.85 1.77 22 31.21 0 2.65 2.3 x I@ 0.7 0.7 0.42 8.0 0.10 0.43 1.38 21 32.91 7 0.33 0.2 0.2 - 10.4 0.09 0.00 1.38 24 34.73 sed 17.0 7.9 - 9 ice 1.83 1.1 x 109 18.0 2.9 1.69 7.8 0.21 4.33 1.36 21 26.38 0 0.41 9.5 x lo7 1 .o 1.o - 8.1 0.09 0.64 1.27 20 28.19 7 0.24 0.1 0.1 - 10.2 0.09 0.00 1.22 23 34.54 sed 4.8 2.7 0.01 11 ice 2.80 7.0 x lo6 0.1 0.0 7.1 0.09 2.26 2.86 21 16.39 0 1.51 6.7 x 10’ I .4 0.3 0.01 9.9 0.09 0.64 2.62 23 24.09 7 0.23 0.5 0.1 0.01 6.8 0.16 0.11 0.88 23 33.84 sed 12.2 6.3 -

* PIantpigmentandprimaryproductivitydatafortheiceandsedimentsaregivenonam-2basis. t Integrated standing stock for the water column is given at 0 m. P 00 - Dark bottle uptake higher than light bottle uptake. W 490 R. HORNER and G. C. SCHRADER

." the line wassecured to thereference post under the ice and the light intensity was measured at the same points before - ICE ALGAE and after removal of the ice algal layer. A"--& PHYTOPLANKTON o-.-.-o BENTHIC MICROALGAE n-0 LIGHT RESULTS o! E 2.5 Stefansson Sound 6 A Phytoplankton levels in Stefansson Soundwere low c during the winter period (Table 1). Unidentified flagel- lates, mostly <6 p,m in diameter, were the most common organisms present in November, Februaryand March. A few diatoms, including spores of Chaetoceros spp. and cells of Navicula spp. and Nitzschia spp., were also present. The diatoms contained chloroplasts, but did not appear to be healthy. Chlorophyll a concentrations were barely detecta- ble. More diatoms were present in March, but chlorophyll a levels were still low. By May, more diatom cells were present in the water column, including species of Chaetoceros, Cylindrotheca, Navicula, and Nitzschia. These were mostly pennate spe- cies and were probably released from the ice as it beganto APRIL MAY JUNE disintegrate. Unidentified small flagellates were abundant. FIG. 2. Primary productivity (mg Cm-2.hr") and incident light inten- Unidentified species ofProtoperidinimand other unidentified sity (pEm-2.sec"), spring 1980. Productivity of the water column was dinoflagellates were present in low numbers. Chlorophyll calculated by integrating productivityat 0 and 7 m. a concentrations increased to near 1 mg-m". An ice core contained >23 x lo6 cells-l", with the dia- cleaned and permanently mounted in euparol to aid in toms Nitzschia frigida and N. cylindrus comprising about identification. 50% of the population. Unidentified small flagellates were Primary productivity and standing stock of the benthic also abundant, as were unidentified cryptomonads; the microalgal communitywere studied using fieldand labora- euglenoids Eutreptiella sp. and Urceolus sp.; and unidenti- tory techniques described by Matheke and Horner (1974), fied dinoflagellates, including Protoperidinium spp. Chy- except that carbon uptake was determined using the wet tridiaceous fungi were found to be parasitizing some of the combustion technique described by Atlas and Hubbard pennatediatoms. Chlorophyll a in theice was near (1974). 2.7 mg-me2. Light intensity was measured with an underwater quan- Primary productivity in the watercolumn waslow, aver- tum sensor and aquantumradiometer-photometer(Models aging ca. 0.15 mg C.m'3.hr". In the ice, primary produc- LI-192s and LI-185A, LI-COR, Inc., Lincoln, NE) that tivity was near 1.5 mg C.m-2.hr". measure light intensity in the photosynthetically active 400-700 nm wave band. Submarine light was measured Narwhal Island immediately after placement of the I4C incubation cham- Ice algal productivity was <0.2 mg C-m-'.hr" during bers and just prior to their retrieval. With the sensor April (Fig. 2, Table 2), but increased to 0.8 mg C.m-'-hr" directed upward, light wasmeasured directly beneath the during the firstweek in May when submarine light levels ice, before and after removal of the ice algal layer. Light increased. After a week of stormy weather with fog and reaching the benthos was measured nearthe bottom, directly blowing snow, light dropped to one-half the previous level above the 14C incubation chambers. Ambient lightoutside and productivity to ca. 0.1 mg C.m'2-hr", increasing to the dive shelter was determined with the sensor held 2.6mg C.rn-'.hr" by the end ofMay in response to vertically ca. 2 m above thesnow surface. increased light. Snow was completely gone from the sur- We also rana series of transects through a semi-permanent face of the ice,and overflow from the Sagavanirktok River snow drift and through the area where most of the ice was first noticed by the divers. Two days later, the soft samples were collected to assess theeffect of snow depth bottom layer of ice containing the ice algae had begunto on light penetration and algal growth. A line marked at dissociate from the ice forming a slush layer loosely associ- 0.5 m intervals was anchored to a reference post placed ated with the undersurface of the ice. Small pieces of the through the ice and visible from both the surface and slush layer clouded the water column. Another peak in underside of the ice. The surface light intensity was recorded productivity occurred in early June, and by mid-June the and snow depth measured at 0.5-1.0 m intervals for a underside of the ice was eroding and the ice algal layer was distance of 25 m. Immediately after the surface transect, no longer visible. PRIMARY PRODUCTION IN THE NEARSHORE BEAUFORT SEA 49 1

Water column productivity was <0.2 mg C.m-3.hr" during April andthe firsthalf of May, but increased during - ICEALGAE late May and early June. Two productivity peaks were PHYTOPLANKTON evident, 22 May and 7 June, coinciding with periods of BENTHICMICROALGAE high ice algal productivity. Thehighest water column pro- ductivity occurred on 7 June and probably resulted from I the disintegrating ice algal layer. Productivity in the water column was primarilyat 0 m, withproductivity at 7 m near the limitof detection throughout the sampling period. Surface and 7 m water column productivity were inte- grated for comparison with ice algal and benthic microal- gal communities (Fig. 2). Benthic productivity remained near the limit of detec- tion, ca. 0.01 mg C.m-2-hr", throughout the study. Light reaching the benthos was ca. 0.2% of surface values and this probably limited growth. Although light levels at the ice-water interface increased as the snow melted, shading from the growing ice algallayer preventedan increase in light at depth. " 1 Total productivity for the threecommunities during the IO 16 24 2 IO 18 26 3 I1 course of the sampling period was calculated by multiply- APRIL MAY JUNE ing the hourly rate by the day lengthin hours and integrat- FIG. 3. Chlorophyll a (mg.m-*), spring 1980. Chlorophyll a of the ice ing the daily rates over the study period. The ice algal algae is the averageof three replicatecores; chlorophyll a of the benthic community contributed 688 mg C.m-*, or ca. two-thirds microalgae is from one core; chlorophyll a of the water column was of the measured primary production; the phytoplankton calculated by integrating values from0 and 7 m. 380 mg C-rnm2, or one-third;and the benthic community, a negligible 12 mg C.me2. Chlorophyll a in the ice algae followeda patternsimilar to thatshown for primary productivity. Levelswere rela- tively low duringApril, ca. 1 mg.m'2, increasing to >26 mg.m-2 during the latter part of May and dropping to near zero by the end of the bloom period in mid-June (Fig. 3). Pigment concentrations in the water column remained low throughout most of the study period, rising slightly near the end of the ice . Chlorophylla concen- trations at7 m were fairly constant, ranging from

APr May Jun Nov Taxon 2 29 24 19 17 14 10 5 8 15 2026 24 22 29 31 257911 9

Pennate Diatoms Achnanthes taeniata Grunow P 00 P ox00 P Amphiprora alata (Ehrenberg) Kiitzing P Amphiprora kjellmanii Cleve PP P P Amphiprora paludosa v. hyperborea (Grunow) Cleve PPPPPP P P Amphora ocellata Donkin 0 XPOXXOOPOOO Cylindrorheca closterium (Ehrenberg) Reimann & Lewin P A P PPPPooooxx oxxoo P Eunotia sp. P 0 Fragilaria sp. P P 0 0 P P Gomphonema exiguwn v. arctica Grunow 00x00 PPPOPPPPPPOPPOO P Gyrosigmafmciola (Ehrenberg) Cleve P PPPPP PP Gyrosigma-Pleurosigmaspp. OP 00 PPPPPOOOPPPPPPP P Licmophora spp. ox 000 PPPOPPPPPPPPO Navicula bolleana (Grunow) Cleve cf. POOPO PPPO PP P OOPOO Navicula directa (W. Smith) Ralfs in Pritchard P POOOOOXOOXOAXAO P Navicula kjellmanii Cleve P Navicula maculosa Donkin P P PPPPPP Navicula marina Ralfs PXOPP PPPPPPPP P PPPP Navicula pelagica Cleve P P Navicula spicula (Hickie) Cleve 0 000 AOOOXOAAAA OXO00 P Navicula transitans Cleve POPPPOOOOXAO OOOXX P Navicula trigonocephala Cleve POOPPPP POPP P PPPP Navicula valida v. minuta Cleve 0 P P OPPPPP PPPPO Navicula sp. A P P P P Nitzschia angularis W.Smith PPOP P Nitzschia cylindrus (Grunow) Hade AAXAAX AAAAAAAAAA AXOXA A Nitzschiajiigida Grunow A0 PAAXAXAX 000 AOAA P Nitzschia seriataCleve 0 Nitzschia sigma (Kiitzing) W. Smith cf. P P P P TABLE 3 continued

APr May Jun Nov Taxon 19 17 10 14 29 24 2 5 8 15 20 22 24 26 29 31 257911 9

Nitzschiu sigmoideu Nitzschiu (Nitzsch) W. Smith P PPPPP P P P Nitzschiu sp. A 00000P P P P Nitzschiu sp. B 0 PPOOP P P P PP Pinnuluriu quudrutureu Pinnuluriu (A. Schmidt) Cleve PP P PPP 2 Pinnuluriu quadraturea v. kerguelensis (Cleve & m Grunow) Cleve P 0000 OPPOO P Pinnuluriu quudrutureu Pinnuluriu v. theelii (Cleve) Cleve PP Pseudonihschia delicutissimu (Cleve) Heiden P PPPPOPPPP 0 Stuuroneis quudripedis (Cleve-Euler) Hendey PPPPP P Synedru spp. 0 PO0 0000 P Thulussiothrix spp. P P PPOPOPPPP Tropidoneis sp. P Unidentified pennate diatoms AOAAXAAXOAXAXAAA AAAAA P Centric Diatoms Chuetoceros Schiitt gracilis P Chuetoceros septentrionulis Gstrup P P Chuetoceros spp. ox P Thuhsiosiru gruvidn Cleve P PP P 000 P 0 P Dinoflagellates Amphidinium sp. P P PPP P PPP P Gymnodinium sp. P P Protoperidinium grenlundicum (Woloszynska) Balech P Unidentified dinoflagellates PPPPPPPO0 PPP P P P Flagellates Cryptomonad spp. P P PP P PPP Dinemutomonus litoruleDinemutomonus (Perty) Silva P P PPPPPPPPP Eutreptiellu sp. PPPPPPPPP PP P Urceolus sp. P Unidentified euglenoid sp. PPPPPPPP Plutymonus spp. OP 0 OPPPP unidentified flagellates (< 6 Fm) OAPOOO AXXXXAAAAA AXAXA P

P = present (lo%) 494 R. HORNER and G. C. SCHRADER

6 - FLAGELLATES (om) I Fifty-five taxa, including 39 species or genera of pennate diatoms, four centric diatoms, three dinoflagellates, and six flagellates, were identified from ice cores (Table 3). The ice algal community was dominated by pennate dia- toms with Nitzschia cylindrus accounting for 47% of all diatoms. Other numerically important pennate diatoms included Amphora ocellata, Cylindrotheca closterium, Navic- ula directa, N. transitans, and Nitzschia frigida. Centric dia- toms were represented by few species and in low numbers. Thalassiosira gravidawas most common, occurring in one- third of the samples.Chaetoceros septentrionaliswas found once and other small Chaetoceros spp.,

Seventeen taxa, including 10 species, were identified May, possibly because of overflow from the Sagavanirk- from the benthos (Table 5). An additional 12 taxa with tok River. The water column became stratified with a eight species were identified from empty frustules. Prob- 10%0difference between the surfaceand 7 m in June when ably more species were present, but were not identified. the ice started to melt. Salinity in the ice was variable, The benthic microalgal communityconsisted almost exclu- probably because of melting ice in the core samples. sively of pennate diatoms. A single resting spore of Chaeto- Light penetrating the ice and reaching the top of the ceros sp. was the only centric diatom and Dinematomonas algal layer fluctuated between 0.5 and 1.5% of surface litorale was the only flagellate identified. light, or about 5 and 18 pE.m-2.sec", during the period Although we were unable to identify the majority of the of snow cover. Light levels increased sharply, fluctuating species present, they were clearly not the same species between 1.4 and 4% of surface values (6 and 19 pE.m'* found in the ice or water column. Cylindrotheca closterium, Ssec") after the snow cover melted on 29 May. Light Navicula cancellata, N. directa, N. spicula, N. transitans var. beneath the ice did not generally increase in response to derasa, Nitzschia angularis, and N. cylindrus occurred in decreasing snow cover becauseof the shading effect of the both the ice andsediments, but comprised a small fraction growing ice algal layer. Light reaching the benthos was of the cells present in the sediments. Nitzschia cylindrus, low, remaining near 0.2% of the surface value, or ca. the dominant species of the ice and water column, was 2 p,E.m-2.sec". represented by a single pair of cells near theend of the ice algal bloom.They appeared tobe unhealthy and had prob- ably fallen from the ice, All of the taxa represented by empty frustules were members of the ice algal community DISCUSSION and probably originated there. The annual cycle of ice algae, phytoplankton, and ben- The concentrations of inorganic plant nutrients aregiven thic microalgae isshown in Figure 7. Microalgae are pres- in Table 2. Data from ice cores should be considered as ent in the ice as soon as it forms in the fall. Microflagellates minimum values because they were obtained from melted are usually the most abundant organisms, but a few pen- cores that were diluted by an unknown amount from the nate diatoms may also be present (Homer, 1976). The melting ice. origin of the cells is not known. Few species of ice algae Nitrate in the water column was near10 pg-at? through- are members of the fall phytoplankton community, which out the study period. This is comparable to levels found is dominated by centric diatoms (Homer, 1969), rather during the winter near Barrow (Matheke, 1973) and near than the flagellates and pennatediatoms found in the ice. It Prudhoe Bay (Homer et ai., 1974), but is considerably is possible that ice algae species are presentin the water higher than in samples collected in Stefansson Sound in column in lownumbers and are not collected by conven- May 1979 where values ranged from 1.5 kg-at.1" at the tional sampling techniques, but once trapped in the ice, surface to 4.5 pg-at.1" at 4 m. natural selection favours species adapted toice thehabitat. Nitrate concentrations in the ice were approximately Newly formed sea icemay be seeded from ice algae still equal to surface waterlevels from April to mid-May. The associated with drifting pack ice that persists throughout concentration increased to 15-20 pg-atvt' for two weeks the summer, but it is not known if cells remain viablein the during the peak of the ice algal bloom, and then declined to drifting pack ice as late as freeze-up. Another possible previous levels. The source of this nitrate is not known, source of seed stock maybe sediments that become but may have resulted from brine drainage or microbial resuspended during the fall storms in nearshore areas. activity (Schell, 1974). Although somespecies arecommon to both habitats, many Nitrite concentrations were low and remained nearly species found in the ice, including the most abundant ice constant throughout the study period. Ammonia was highestspecies, are not found in the sediments (Matheke and in the ice, ca.1.2 pg-atst', and lowest in water from 7 m, Horner, 1974) although they may be rare or not detected. 0.03 Kg-at.1". The ammonia concentration increased in Growth of the diatoms in the ice in fall probably con- the ice during the peak of the bloom with high values, tinues until mid-November when light becomes limiting, 4.33 pg-at@, near theend of the bloom. although few reports are available to confirm this. In the Phosphate concentrationsin the ice and water column Eskimo Lakes region of arctic Canada,in late November, were generally ca. 1.5 pg-at-t', which is similar to winter Hsiao (1980) found a layerof ice algae concentrated near levels reported from Barrow (Matheke, 1973) and Prudhoe the bottom of sea ice 50 cm thick that contained ca. 4.9 X Bay (Horner et al., 1974). Several anomalous peaks in ldcell~.m-~(ca. 3.9 x Id cells.m-2). Inthe western Beaufort phosphate concentrationwere seen, but we have no explana- Sea, a core collected in early November from our study tion for them. Silicate concentrations were nearly con- site off Narwhal Island contained a rich algal layer in the stant, averaging 22 p,g-at.t', in the-ice and surface water bottom of the ice (Schell, pers.comm.) with distom con- and slightly higher, 24 p,g-at.T', at 7 m. centrations of 1.8 x 10' cells.mq2,comparable to levels Salinity was near 34.5%0at the surfaceand 35.5%0at 7 m found during the 1980 spring bloom. The cells were healthy (Table 2). Salinity dropped ca. 1%0 during the last half of and the species composition was similar to that found in P TABLE 4. Relative abundanceand distribution through time of phytoplankton speciescollected at 0 and 7 m off NarwhalIsland, spring 1980 Wm

APr May Jun Date 14 10 11 219 29 24 5 8 I5 29 2620 24 22 31 2 5 I 9 11 Taxon Depth Taxon 010707070107 01010707070707010107 0707070107

Pennate Diatoms Achnanthes taeniata Grunow P PP P Achnanthes sp. P P PPPP Amphiprora paludosa v. hyperborea (Grunow) Cleve PP Amphora ocellata Donkin P PP P P PP P P PO P P PPPPP Amphora sp. P P Cylindrotheca closterium (Ehrenberg) Reimann& Lewin PPPP PP P P P P PPPP OPX XP Gomphonema exiguum v. arctica Grunow P PPP PPPPPPP Gomphonema kamtschaticumGrunow P PP P Gyrosigmafasciola (Ehrenberg) Cleve P P P Gyrosigma-Pleurosigmaspp. PP P P P P PPP P P PPPPPPPPP Licmophora spp. P P P P P P PPPPP P Navicula bolleana (Grunow) Cleve cf. P P P PPP P P PPPPPP P P P P PP Navicula directa (W. Smith) Ralfs in Pritchard PPXP P P PPPP P P PPPPPPOPPP Navicula kjellmanii Cleve P Navicula lyroidesHendey P Navicula maculosa Donkin P Navicula marina Ralfs P P PP P PPP Navicula pelagicaCleve PP Navicula spicula (Hickie) Cleve PPP P P PP PPPP PP P PPO PPPP Navicula transitans v. derasg (Grunow) Cleve P PPP P PPPPPPPPP P P P PPPPPPP Navicula trigonocephala Cleve P P P P Navicula valida Cleve PP P Navicula sp. A PP Nitzschia angularis W. Smith P P P Nitzschia cylindrus (Grunow) Hasle P APAXAAAPAPOAPPAA 0 APXOAPAPAA Nitzschiafrigida Grunow P PPP PP P PPO Nitzschia seriataCleve PPP PP PP x P Nitzschia sigma (Kiitzing) W. Smith cf. PP Nitzschia sigmoidea (Nitzsch) W. Smith PO Nitzschia sp. A P P Nitzschia sp. B P PPP P P P PP Pinnularia quadratarea v. kerguelensis (Cleve & GNnOW) Cleve PP P P PPP P P P PP Pinnularia quadratarea v. theelii (Cleve) Cleve P PP P Pseudonitzschia delicatissima(Cleve) Heiden P P PPPPP P P P OP Rhoiconeis sp. P Stauroneis quadripedis (Cleve-Euler) Hendey P PP Stauroneis sp. A Thalassiothrix spp. P PPP P PP P PP Unidentified pennate diatoms PPP PPPPPPAO PPPP PPPP XXPP PPPP APOPPXXPPA Centric Diatoms Chaetoceros Schiitt gracilis P Chaetoceros gstrup septentrionalis 0 PRIMARY PRODUCTION IN THENEARSHORE BEAUFORT SEA 498 R. 498 HORNER and G.C. SCHRADER

TABLE 5. Relative abundance and distribution through timeof benthic microalgae species from seven sediment cores collected off Narwhal Island, spring 1980

AP r May APr Jun Taxon 29 24 19 1710 14 2 5 8 1529 20 2622 24 31 2 5 7 9 1 Pennate Diatoms Achnanrhes sp. XP 0 Amphora sp. P Cylindrotheca closterium (Ehrenberg) Reimann & Lewin P D iploneis smithii Diploneis (de Brkbisson) Cleve X 0 0 Diploneis sp. 0 *Gomphonema exiguumv. arctica Grunow *Gomphonema kamtscharicum Grunow *Gyrosigma fasciola (Ehrenberg) Cleve *Gyrosigma-Pleurosigma spp. N avicula cancellata Navicula Donkin AhA0 X A A Navicula cancellafa v. skaldensis Van Heurck P P 0 0 Naviculadirecta (W. Smith) Ralfsin Pritchard P *Navicula gracilis Kiitzing *Navicula peregrina (Ehrenberg) Kiitzing Navicula spicula (Hickie) Cleve A Naviculatransitans v. derasa (Grunow) Cleve PP P 0 P N irzschia angularis Nirzschia W. Smith P P Nirzschia cylindrus (Grunow) Hasle P *Nirzschiafrigida Grunow *Pinnularia quadratarea (A. Schmidt) Cleve sp. P Srauroneis sp. Synedra spp. P P Unidentified tube-forming species A Unidentified pennate diatoms AA AA A A A Centric diatoms *Chaetoceros spp. Chaeroceros sp.P resting spore *Coscinodiscus radiatus Ehrenberg *Thalassiosira sp. Flagellates D inemaromonas lirorale Dinemaromonas (Perty) Silva P

P = present (

TABLE 6. Annual ice algal productivity determined from the ice the preceding spring. It isnot knownwhether this is I4C uptake experiments and chlorophyll a concentrations a regular occurrence, how long this bloom might last, or how productive it is. An autumnal bloom has been reported

~~~ to be a normal event in the Antarctic sea ice (Hoshiai, Annual Productivity 1977). Location (mg Cd) Source Heterotrophy has been suggested as a mechanism by which algae survive the prolonged darkness of the arctic Davis Strait 0.15 Andersen (1977) winter (Rodhe, 1955; Wilce, 1967; Allen, 1971), but exper- Barrow, Alaska 5.0 Alexander et al. (1974) iments using a variety of labeled organic substrates failed Stefansson Sound 0.9 Homer (1980) to show heterotrophic growth in the dark for Antarctic Simpson Lagoon 0.18* Schell(1980b) Stefansson Sound 1.4* Schell(1980b) (Bunt and Lee, 1972) or Arctic (Horner and Alexander, Offshore Beaufort Sea 1.7* Schell(198Ob) 1972) ice algae. Antia (1976) has shown that many algal Narwhal Island 0.7 This study species maintain viability for 5-6 moin media free of

~~ organic substrates at temperatures ranging from 2-20°C. *Estimated from chlorophyll a concentrations Benthic species, i.e. pennatediatoms, weremore resistant, PRIMARY PRODUCTION IN THE NEARSHORE THE IN PRODUCTION PRIMARY SEA BEAUFORT 499

,00..00000000I 0 N D J F M A M J J A C

0 B'

FIG. 7. Schematic representationof the annual cycles of ice algae,phytoplankton, and benthic microalgae thein nearshore areaof the Beaufort Sea and Stefansson Sound. with some remaining viable for over one year and a few tivity began to increase when the light level was 7.7 species for three years of darkness. We expect that ice kE.m-2.sec'1. algae, adapted to low temperatures, would easily beable Light may be severely limited by sediments trapped in to survive the 4-5 mo period of winter darkness. the ice in nearshore areas.One or more layers of sediment Cells are scatteredthroughout the ice in winter (Horner, were present in a series of ice cores collected in Stefansson 1976; Hsiao, 1980), but by mid-March the algae become Sound in early April 1980 and no algallayer was detected. concentrated at thebottom of the ice.It is not known how In mid-May, we sampled Stefansson Sound againand the cells become concentrated, but it may be a result of found only a trace amount of chlorophyll Q at a time when brine drainageand the active migration of algalcells through productivity was high at Narwhal Island. This is in con- brine channels that move downward through the ice by trast to 1979 when the algal layer in the same area was diffusion andgravity. Brine drainage becomes more rapid well-developed, though patchy. Light attenuation by tur- as theice warms in spring which mayaccelerate the trans- bid ice isthe factorcontrolling the development of the ice port of the algae. The algae may actively migrate as well, algal communityin Stefansson Sound,according to Schell because many pennate diatoms are able to move with a (1980a, b). In shallow areas, the extent of the ice algal slow, gliding movement. layer, and thus spring productivity of the lagoon, is appar- Light is apparently the major factor controlling the ently determined by the distribution of sediments in the distribution, development, andproduction of the ice algal ice. community withgrowth of the ice algae beginningin spring Where ice does not contain sediment,light attenuation in response to increasing light. In the Chukchi Sea near because of snow isthe prime factor controllingthe distribu- Barrow, productivity remained <0.1 mg C.m-2.hr" until tion and productivity of ice algae. The light-attenuating a threshold light level was reached (Alexander etal., 1974). property of snow is very high compared with that of clear Above this level, 2.3 and 9.3 pE.m-*.sec" in successive sea ice (Thomas, 1%3). We found that ca. 2% of surface years, production was rapid. Off Narwhal Island, produc- light reached the algal layer when no snow was present, 500 R. HORNER and G.C. SCHRADER but 3-4 cm of snow reduced light to 1%; 6 cm to

About 200 diatom species have been identified from tic because few measurements have been made and methods arctic sea ice,but onlya few species have been reported as generally have been different. Only the Barrow (Alexander dominant. Of 55 species enumeratedin our samples,only et al., 1974), Stefansson Sound,and Narwhal Island stud- six species ever accounted formore than 10% of the cells ies have used similar in situ techniques. Andersen (1977) counted. Hornerand Alexander (1972) found that Nitzschia used a modified in situ method in the Davis Strait area and frigida was usually the most abundant species at Barrow, Schell(1980a, b) estimatedproductivity from chlorophyll but Meguro et al. (1966, 1967) apparently did not find it a measurements in Simpson Lagoon, Stefansson Sound, farther offshdre. Itwas often important in the community and offshore in the Beaufort Sea (Table 6). The highest off Narwhal Island, in Stefansson Sound,and in the Cana- production was from Barrow and the lowest from Davis dian Arctic (Dunbar and Acreman, 1980; Hsiao, 1980). Strait. Only the Barrow and Narwhal Island studies were Navicula marina was also aprominent member of the com- done throughout the whole cycle of the ice algal bloom munity at Barrow and was often the most abundant spe- from April or earlier to June. cies (Alexander et d., 1974), but it wasnever abundant off It should bestressed thatprimary productivity measure- Narwhal Island. ments of ice algaeare probably minimum values. We feel Changes in community structure accompanied the devel- that while our methods (Clasby et al., 1973; Schrader et al., opment of the bloom off Narwhal Island. During April and 1982) were the most appropriate and the best available at early May, the community was strongly dominated by the time, there are several sourcesof error thatlead to an Nitzschia cylindrus, but in mid-May this species became underestimate of productivity. Because the ice algallayer less healthy and empty frustules were common in the ice is formed of a matrix of ice crystals, it is difficultto ensure and water column. As the relative numbers of N. cylindrus adequate mixing ofthe isotopethroughout the sample,and declined, other diatom and flagellate species that had been due to theporous nature of the ice,an unknown amountof rare ornot previously identified became common andthe label may diffuse upward into the ice and be lost during diversity of the community increased. An increase in stand- incubation. These and other problems undoubtedly lead to ing stock (chlorophyll a)accompanied this shift in commu- an underestimate of primary productivity by the ice algae. nity structure. The productivity of this community is therefore probably greater than our measurements indicate. Environmental factors may have contributed to these Phytoplankton was present in low numbers during the species changes. Light inhibition has been suggested as a winter, with unidentified flagellates, mostly

I GRANT, W.S. and HORNER, R. 1976. Growth responses to salinity RODHE, W. 1955. Can plankton production proceed during winter variation in four arctic ice diatoms. Journal of Phycology12: 180-185. darkness in subarctic lakes? Verhandlungen der internationalen HAMEEDI, M.J. 1978. Aspects of water column primary productivity in Vereinigung f& theoretische und angewandte Limnologie12: 117-122. the Chukchi Sea during summer. Marine Biology 48:37-46. SAITO, K. and TANIGUCHI, A. 1978. Phytoplankton communities in HORNER, R. 1969. Phytoplanktonin coastal waters near Barrow, Alaska. the Bering Sea and adjacent seas. 11. Spring and summer communities Unpublished Ph.D. thesis, Department of Botany, University of in seasonally ice-covered areas. Astarte 11:27-35.

Washington, Seattle, Washington. ~ SCHANDELMEIER, L. and ALEXANDER, V. 1981. An analysis of -. 1976. Sea ice organisms. Oceanography and Marine Biology the influence of ice on spring phytoplankton population structure in Annual Review 14:167-182. the southeast Bering Sea. Limnology and Oceanography 26:935-943. -and ALEXANDER, V. 1972. Algal populations in arctic sea ice: SCHELL, D.M. 1974. Regeneration of nitrogenous nutrients in Arctic an investigation of heterotrophy. Limnology and Oceanography Alaskan estuarine waters. In: Reed, J.C., and J.E. Sater. (eds.). The 17:454-458. Coast and Shelf of the Beaufort Sea. Arlington, Virginia: The Arctic -, COYLE, K.O. and REDBURN, D.R. 1974. Ecology of the Institute of North America. 649-664. plankton of Prudhoe Bay, Alaska. Institute of Marine Science, Uni- -. 1980a. Chemical overview of biological-physical process inter- versity of Alaska, Report R74-2; Sea Grant Report 73-15. 78 p. actions. Outer continental Shelf EnvironmentalAssessment Program, HOSHIAI, T. 1977. Seasonal changes of ice communities in the sea ice Arctic Project Bulletin 29:25-31. nearSyowaStation,.In:Dunbar,M.J.(ed.).PolarOceans. -. 1980b. Foodweb and nutrient dynamics studies in nearshore Calgary, Alberta: The Arctic Institute of North America. 307-317. Alaskan Beaufort Sea waters. Environmental Assessment of the HSIAO, S.I.C. 1980. Quantitative composition, distribution, community Alaskan Continental Shelf, Annual Reports 2:467-513. structure and standing stock of sea ice microalgae in the Canadian SCHRADER, G.C., HORNER, R. and SMITH, G.F. 1982. An improved Arctic. Arctic 33:768-793. chamber for in situ measurement of primary productivity of Arctic MATHEKE, G.E.M. 1973. The ecology ofthe benthic microalgae inthe sea ice algae. Canadian Journal of Fisheries and Aquatic Science sublittoralzoneoftheChukchiSeanearBarrow,Alaska. Unpublished 39~522-524. M.S. thesis, Institute of Marine Science, University of Alaska, STRICKLAND, J.D.H. and PARSONS, T.R. 1972. A Practical Hand- Fairbanks, Alaska. book of Seawater Analysis. Bulletin of the Fisheries Research Board -and HORNER, R. 1974. Primary productivity of the benthic of Canada 167. 310 p. microalgae in the Chukchi Sea near Barrow, Alaska. Journal of the THOMAS, C.W. 1963. On the transfer of visible radiation through sea Fisheries Research Board of Canada 31:1779-1786. ice and snow. Journal of Glaciology 4:481-484. MEGURO, H., ITO, K. and FUKUSHIMA, H. 1966. Diatoms and the UTERMOHL, H. 1931. Neue Wege in der quantitativen Erfassung des ecological conditions of their growth in sea-ice in the . Planktons. Verhandlungen der internationalen Vereinigung fur Science 152:1089-1090. theoretische und angewandte Limnologie 5567-596. -. 1967. Ice flora (bottom type): a mechanism of primary produc- WILCE, R.T. 1967. Heterotrophy in arctic sublittoral seaweeds. Botanica tion in polarseas and the growth of diatoms in sea ice. Arctic 20: 114- 133. Marina 10:185-197. PAVLOU, S.P. 1972. Phytoplankton growth dynamics: chemostat meth- odology and chemical analysis. Department of Oceanography, Uni- versity of Washington Special Report No. 52. 130 p.