AMLR program: Photobiological characteristics of phytoplankton ...
during Survey A (3.5 liters vs. 4.0 liters), but the median abundance of 224.7 salps per 1,000 cubic meters was about half of that during the January survey. This difference is probably related to greater proportions of large-sized saips during February and March (Foxton 1966). Relatively large salp concentrations (100 to 1,000 per 1,000 cubic meters) were distributed across much of the survey area. Smaller concentrations generally occurred in the northwest portion, and larger concentrations were primarily located in the southwest and southeast portions (figure 3). The euphausiids T. macrura (larval and postlarval stages; 84 percent of samples, 118.9 per 1,000 cubic meters), Euphausiafrigida (62 percent of samples, 25.9 per 1,000 cubic meters; not shown on table 1), and krill followed salps in overall mean abundance. Copepods and E. frigida were substantially more abundant in Survey D compared to Survey A. The overall hill length frequency distribution and maturity stage composition during the 1994 surveys (table 2; figure 2) reflect low input of individuals from the last two year classes. This is indicated by the relatively minor contributions by juveniles (approximately 25 to 30 mm lengths) and immature stages (approximately 31 to 40 mm lengths) and suggests that there has been poor spawning and/or larval survival during both the 1991-1992 and 1992-1993 seasons. The minor contributions by these two year classes may in part explain the relatively low krill abundance during 1994 (Hewitt and Demer, Antarctic Journal, in this issue). Salp abundance in the Elephant Island area during both 1993 and 1994 was an order of magnitude greater than during 1992 (table 1). The past two summer seasons have been characterized by the widespread distribution of high salp concentrations (greater than 100 per 1,000 cubic meters) across the survey area (figure 3; Loeb and Siegel 1993) and clear dominance of the macrozooplankton by salps. Salps are herbivores
and feed on the same sizes of phytoplankton as bill (Hopkins and Torres 1989); therefore, they are direct competitors of bill for food. It is possible that the high salp concentrations have had an effect on the bill stocks in the Elephant Island area by reducing the food supply and influencing bill swarming and migratory behavior (Loeb and Siegel 1993). It is possible that the poor year class success from the 1992-1993 season is related to the high concentrations of saips during that time. In contrast to these two species, the stocks of the other abundant euphausiid, T. macrura, showed little between-year variation in abundance (table 1). This work was supported by National Oceanic and Atmospheric Administration (NOAA) Cooperative Agreement NA47FR0029. Special thanks go to Alan Young, Mike Force, David Greene, Sue Kruse, Rick Phieger, Jennifer Quan, Aaron Setran, and Brian Walker for their assistance with sample collection and processing.
References Foxton, P. 1966. The distribution and life history of Salpa thompsoni Foxton, with observations on a related species Salpa gerlachei Foxton. Discovery Report, 34, 1-116. Hewitt, R.P., and D.A. Demer. 1994. AMLR program: Distribution and abundance of krill near Elephant Island in the 1993-1994 austral summer. Antarctic Journal of the U.S., 29(5). Hopkins, T.L., and J.J. Torres. 1989. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea. Deep-Sea Research, 36(4), 543-560. Loeb, V., and V. Siegel. 1993. AMLR program: Krill and macrozooplankton in the Elephant Island area, January to March 1993. Antarctic Journal of the U.S., 28(5), 185-188. Makarov, R.R., and C.J.I. Denys. 1981. Stages of sexual maturity of Euphausia superba. In BIOMASS Handbook (Vol. 11). Rosenberg, i.E., R.P. Hewitt, and R.S. Holt. 1994. The U.S. Antarctic Marine Living Resources (AMLR) program: 1993-1994 field season activities. Antarctic Journal of the U.S., 29(5).
AMLR program: Photobiological characteristics of phytoplankton around Elephant Island, Antarctica E. VILLAFANE, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0202
OSMuND HOLM-I-IANSEN, VIRGINIA
ne of the major objectives in the phytoplankton compoO nent of the Antarctic Marine Living Resources (AMLR) program was to study the photobiological characteristics of the antarctic phytoplankton and rates of primary production. Other major portions of our studies were the distribution of phytoplankton in the study area (described in Viilafane et al., Antarctic Journal, in this issue) and the inorganic nutrient concentrations (described in Silva et al., Antarctic Journal, in this issue). This research was performed in a 91-station grid that was occupied two times, once during each leg (Leg I, 12 January to 9 February; Leg II, 14 February to 15 March). The
station locations and cruise track are given in Rosenberg, Hewitt, and Holt, (Antarctic Journal, in this issue). Water samples were obtained at 11 standard depths [from 5 to 750 meters (m)] from the 10-liter Niskin bottles (with Teflon-covered springs) mounted on a rosette (General Oceanics). For obtaining information on the upper water column characteristics, sensors for the following measurements were attached to the rosette: • conductivity-temperature- depth (CTD, Sea Bird, S139), • photosynthetic available radiation (PAR, 400-700 nanometers, Biospherical Instruments),
ANTARCTIC JOURNAL - REVIEW 1994 188
• beam attenuation (25-centimeter pathlength transmissometer, Sea Tech), and • in situ chlorophyll-a (chl-a) fluorescence (pulsed fluorometer, Sea Tech). Continuous measurements at 1-minute intervals of natural solar radiation were also obtained throughout the time of study with a PAR sensor mounted on the ship's superstructure. In addition, when weather allowed, a profiling PIJV-500 unit (Biospherical Instruments) was deployed down to 100 m depth to obtain information on the attenuation of PAR and ultraviolet radiation in the water column, as well as instantaneous rates of primary production (Helbling and HolmHansen, Antarctic Journal, in this issue). Rates of primary production were obtained from the samples obtained at eight depths (from 5 to 75 m); samples were inoculated with 5.0 microcuries (tCi) of carbon-14 (14C) bicarbonate (Steemann Nielsen 1952) and exposed to natural solar radiation. The samples were placed in a shade-free water bath, and the underwater radiation field (95 to 0.5 percent of incident surface irradiance) was simulated by wrapping the tubes that contained the samples with layers of neutral density screen. After 6-10 hours of incubation (centered around local noon), the samples were filtered through a Whatman GF/F glass fiber filter (25 millimeters), and the 14C
Figure 1. Profiles of rates of primary production with depth. A. Survey A (17-28 January 1994). B. Survey D (25 February to 09 March 1994). Symbols are as follows: • denotes samples from stations in Bransfield Strait waters; A denotes samples from stations in Bransfield-Scotia Confluence waters; 0 denotes samples from stations in Drake Passage waters; X denotes samples from stations in Weddell Sea waters.
incorporation was measured by standard liquid scintillation techniques. To estimate the effect of vertical mixing in the upper water column on the photoadaptive state of the cells, samples were taken from two depths within the upper mixed layer (at 5 and 40 m) and incubated as described above, with different light attenuations, to obtain the photosynthesis-irradiance (P1) characteristics of the phytoplankton at these depths. The rates of primary production with depth (figure 1) varied significantly between different water masses. During Leg I (figure 1A), Drake Passage waters showed the lowest rates of primary production. Most values were less than 3 milligrams of carbon per cubic meter per day (mg C rn-3 d-'), and rates decreased slowly with depth. Bransfield Strait waters showed the highest rates of primary production; some values exceeded 40 mg C m-3 d-'. These stations generally showed a small subsurface maximum in rates at 10 m. Intermediate rates of primary production were observed at stations in BransfieldScotia Confluence waters and Weddell Sea waters. During Leg II (figure 1B), a general increase in the rates of primary production was observed. Stations reached values of 70-120 mg C rn-3 d-' and 4-15 mg C m- 3 d-' in Bransfield Strait and Drake Passage waters, respectively. These differences between Leg I and Leg II could be related not only to an increase in phytoplankton biomass, as observed from Leg I to Leg II but also to a change in the species composition, as described in Villafafle et al. (Antarctic Journal, in this issue). Mean integrated values of primary production in Drake Passage waters were 81.8 [standard deviation (SD) 67.71 mg C m-2 d-' and 118 (SD 81) mg C m-2 d' for Legs I and II, respectively. Mean integrated values for Bransfield Strait waters were 704 (SD 175) mg C rn-2 and 2,340 (SD 370) mg C m 2 d-' for Legs I and II, respectively. Rates of carbon fixation per unit chlorophyll per hour (mg C/mg chi-a/hr) as a function of mean irradiance in rnicroeinstein per square meter per second (iE/m2 Is) for Legs I and II are shown in figure 2. The P-I parameters as calculated using the equations of Platt and Jassby (1976) are as follows: • Pmax (units in mg C/mg chl-a/hr) = 2.64 (Leg I) and 2.52 (Leg II); 2 /S) =56 (Leg I) and 54.7 (Leg II); and • 'k (units in [tE/M • a [units in (mg C/mg chl-a hr 1)/(tE/m2 /s)I = 0.047 (Leg I) and 0.046 (Leg II). The 'k values obtained in this study were slightly lower than data obtained in previous years in the same area during the same season (Heibling, Villafañe, and Holm-Hansen in press). This could indicate increased "dark" adaptation of the phytoplankton cells during 1994 as the mean monthly irradiances were also much lower (320 and 278 pE/m2 /s for Legs I and II, respectively) than the overall mean value of 550 1E/m2/s obtained for previous years. A comparison of the P-I characteristics from cells from 5 m and 40 m (the pycnocline was deeper at these stations) during Leg I (figure 3) shows that there were no significant differences between samples from these two depths, suggesting relatively rapid mixing between these depths. This indication
ANTARCTIC JOURNAL - REVIEW 1994 189
4 3.5 - 3 2.5 0
0)2 E -. 1.5 0 0)1 E 0.5
•: ., ••%•• %•
3.5
I. • S •
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E 1.5 () 01 I E 0 200 400 600 800 1,000
0.5
micro Einstein per square meter per second
3.5 Ce
0
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..
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I I
A
A A
V
v
A17-5m 0 A58-40m A17-40m A A66-5m A66-40m A35-40m V A74-5m V 0 A58-5m A74-40m 0 A35-5m A
100 200 300 400 500 600
micro Einstein per square meter per second
B
Figure 3. P-I characteristics of phytoplankton samples collected at 5 m and at 40 m within the upper mixed layer at five stations during Leg I. Open symbols indicate samples at 5 m; filled symbols indicate samples from 40 m.
•.% 11¼•. •b
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-
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. . . . . . . . . . . . . . . . . .
0 200 400 600 800 1,000
References
micro Einstein per square meter per second
Figure 2. Photosynthetic assimilation numbers as a function of the mean irradiance to which the samples were exposed during the incubation period. A. Leg I. B. Leg II. of strong mixing within the upper mixed layer was also suggested by the profiles of chl-a, which generally showed a fairly uniform distribution throughout the upper mixed layer. This research was supported by National Oceanic and Atmospheric Administration (NOAA) Cooperative Agreement number NA47FR0030. We thank the officers and crew of NOAA ship Surveyor for excellent support during field operations. Grateful acknowledgment is also made to Marcel Ramos (Universidad Católica de Valparaiso, Chile), Humberto Dfaz (Universidad de Valparaiso, Chile), Pedro Baron (Universidad Nacional de la Patagonia, Argentina), and Christian Bonert (Servicio Hidrografico de la Armada, Chile) for their generous help onboard ship. Shipboard personnel included E. Walter Helbling (12 January to 9 February), Virginia Villafañe (12 January to 9 February), and Osmund Holm-Hansen (14 February to 15 March).
Heibling, E.W., and 0. Holm-Hansen. 1994. AMLR program: Distribu tion of phytoplankton in the upper water column in relation to different water masses. Antarctic Journal of the U.S., 29(5). Heibling, E.W., V.E. Vilafañe, and 0. Holm-Hansen. In press. Variability of phytoplankton distribution and primary production around Elephant Island, Antarctica, during 1990-1993. Polar Biology. Platt, T., and A.D. Jassby. 1976. The relationship between photosyn thesis and light for natural assemblages of coastal marine phytoplankton. Journal of Phycology, 12(4),421-430. Rosenberg, J.E., R.P. Hewitt, and R.S. Holt. 1994. The U.S. Antarctic Marine Living Resources (AMLR) program: 1993-1994 field season activities. Antarctic Journal of the US., 29(5). Silva S., N., M. Ramos, E.W. Helbling, and 0. Holm-Hansen. 1994. AMLR program: Depletion of inorganic nutrients in the area around Elephant Island, Antarctica. Antarctic Journal of the U.S., 29(5). Steemann Nielsen, E. 1952. The use of radiocarbon ( 14 C) for measuring organic production in the sea. Journal du Conseil International pour l'Exploration de laMer, 18(2), 117-140. Villafane, V.E., E.W. Helbling, 0. Holm-Hansen, and H. DIaz. 1994. AMLR program: Phytoplankton distribution and species composition around Elephant Island, Antarctica, January to March 1994. Antarctic Journal of the U.S., 29(5).
ANTARCTIC JOURNAL - REVIEW 1994 190
and feed on the same sizes of phytoplankton as bill (Hopkins and Torres 1989); therefore, they are direct competitors of bill for food. It is possible that the high salp concentrations have had an effect on the bill stocks in the Elephant Island area by reducing the food supply and influencing bill swarming and migratory behavior (Loeb and Siegel 1993). It is possible that the poor year class success from the 1992-1993 season is related to the high concentrations of saips during that time. In contrast to these two species, the stocks of the other abundant euphausiid, T. macrura, showed little between-year variation in abundance (table 1). This work was supported by National Oceanic and Atmospheric Administration (NOAA) Cooperative Agreement NA47FR0029. Special thanks go to Alan Young, Mike Force, David Greene, Sue Kruse, Rick Phieger, Jennifer Quan, Aaron Setran, and Brian Walker for their assistance with sample collection and processing.
References Foxton, P. 1966. The distribution and life history of Salpa thompsoni Foxton, with observations on a related species Salpa gerlachei Foxton. Discovery Report, 34, 1-116. Hewitt, R.P., and D.A. Demer. 1994. AMLR program: Distribution and abundance of krill near Elephant Island in the 1993-1994 austral summer. Antarctic Journal of the U.S., 29(5). Hopkins, T.L., and J.J. Torres. 1989. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea. Deep-Sea Research, 36(4), 543-560. Loeb, V., and V. Siegel. 1993. AMLR program: Krill and macrozooplankton in the Elephant Island area, January to March 1993. Antarctic Journal of the U.S., 28(5), 185-188. Makarov, R.R., and C.J.I. Denys. 1981. Stages of sexual maturity of Euphausia superba. In BIOMASS Handbook (Vol. 11). Rosenberg, i.E., R.P. Hewitt, and R.S. Holt. 1994. The U.S. Antarctic Marine Living Resources (AMLR) program: 1993-1994 field season activities. Antarctic Journal of the U.S., 29(5).
AMLR program: Photobiological characteristics of phytoplankton around Elephant Island, Antarctica E. VILLAFANE, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0202
OSMuND HOLM-I-IANSEN, VIRGINIA
ne of the major objectives in the phytoplankton compoO nent of the Antarctic Marine Living Resources (AMLR) program was to study the photobiological characteristics of the antarctic phytoplankton and rates of primary production. Other major portions of our studies were the distribution of phytoplankton in the study area (described in Viilafane et al., Antarctic Journal, in this issue) and the inorganic nutrient concentrations (described in Silva et al., Antarctic Journal, in this issue). This research was performed in a 91-station grid that was occupied two times, once during each leg (Leg I, 12 January to 9 February; Leg II, 14 February to 15 March). The
station locations and cruise track are given in Rosenberg, Hewitt, and Holt, (Antarctic Journal, in this issue). Water samples were obtained at 11 standard depths [from 5 to 750 meters (m)] from the 10-liter Niskin bottles (with Teflon-covered springs) mounted on a rosette (General Oceanics). For obtaining information on the upper water column characteristics, sensors for the following measurements were attached to the rosette: • conductivity-temperature- depth (CTD, Sea Bird, S139), • photosynthetic available radiation (PAR, 400-700 nanometers, Biospherical Instruments),
ANTARCTIC JOURNAL - REVIEW 1994 188
• beam attenuation (25-centimeter pathlength transmissometer, Sea Tech), and • in situ chlorophyll-a (chl-a) fluorescence (pulsed fluorometer, Sea Tech). Continuous measurements at 1-minute intervals of natural solar radiation were also obtained throughout the time of study with a PAR sensor mounted on the ship's superstructure. In addition, when weather allowed, a profiling PIJV-500 unit (Biospherical Instruments) was deployed down to 100 m depth to obtain information on the attenuation of PAR and ultraviolet radiation in the water column, as well as instantaneous rates of primary production (Helbling and HolmHansen, Antarctic Journal, in this issue). Rates of primary production were obtained from the samples obtained at eight depths (from 5 to 75 m); samples were inoculated with 5.0 microcuries (tCi) of carbon-14 (14C) bicarbonate (Steemann Nielsen 1952) and exposed to natural solar radiation. The samples were placed in a shade-free water bath, and the underwater radiation field (95 to 0.5 percent of incident surface irradiance) was simulated by wrapping the tubes that contained the samples with layers of neutral density screen. After 6-10 hours of incubation (centered around local noon), the samples were filtered through a Whatman GF/F glass fiber filter (25 millimeters), and the 14C
Figure 1. Profiles of rates of primary production with depth. A. Survey A (17-28 January 1994). B. Survey D (25 February to 09 March 1994). Symbols are as follows: • denotes samples from stations in Bransfield Strait waters; A denotes samples from stations in Bransfield-Scotia Confluence waters; 0 denotes samples from stations in Drake Passage waters; X denotes samples from stations in Weddell Sea waters.
incorporation was measured by standard liquid scintillation techniques. To estimate the effect of vertical mixing in the upper water column on the photoadaptive state of the cells, samples were taken from two depths within the upper mixed layer (at 5 and 40 m) and incubated as described above, with different light attenuations, to obtain the photosynthesis-irradiance (P1) characteristics of the phytoplankton at these depths. The rates of primary production with depth (figure 1) varied significantly between different water masses. During Leg I (figure 1A), Drake Passage waters showed the lowest rates of primary production. Most values were less than 3 milligrams of carbon per cubic meter per day (mg C rn-3 d-'), and rates decreased slowly with depth. Bransfield Strait waters showed the highest rates of primary production; some values exceeded 40 mg C m-3 d-'. These stations generally showed a small subsurface maximum in rates at 10 m. Intermediate rates of primary production were observed at stations in BransfieldScotia Confluence waters and Weddell Sea waters. During Leg II (figure 1B), a general increase in the rates of primary production was observed. Stations reached values of 70-120 mg C rn-3 d-' and 4-15 mg C m- 3 d-' in Bransfield Strait and Drake Passage waters, respectively. These differences between Leg I and Leg II could be related not only to an increase in phytoplankton biomass, as observed from Leg I to Leg II but also to a change in the species composition, as described in Villafafle et al. (Antarctic Journal, in this issue). Mean integrated values of primary production in Drake Passage waters were 81.8 [standard deviation (SD) 67.71 mg C m-2 d-' and 118 (SD 81) mg C m-2 d' for Legs I and II, respectively. Mean integrated values for Bransfield Strait waters were 704 (SD 175) mg C rn-2 and 2,340 (SD 370) mg C m 2 d-' for Legs I and II, respectively. Rates of carbon fixation per unit chlorophyll per hour (mg C/mg chi-a/hr) as a function of mean irradiance in rnicroeinstein per square meter per second (iE/m2 Is) for Legs I and II are shown in figure 2. The P-I parameters as calculated using the equations of Platt and Jassby (1976) are as follows: • Pmax (units in mg C/mg chl-a/hr) = 2.64 (Leg I) and 2.52 (Leg II); 2 /S) =56 (Leg I) and 54.7 (Leg II); and • 'k (units in [tE/M • a [units in (mg C/mg chl-a hr 1)/(tE/m2 /s)I = 0.047 (Leg I) and 0.046 (Leg II). The 'k values obtained in this study were slightly lower than data obtained in previous years in the same area during the same season (Heibling, Villafañe, and Holm-Hansen in press). This could indicate increased "dark" adaptation of the phytoplankton cells during 1994 as the mean monthly irradiances were also much lower (320 and 278 pE/m2 /s for Legs I and II, respectively) than the overall mean value of 550 1E/m2/s obtained for previous years. A comparison of the P-I characteristics from cells from 5 m and 40 m (the pycnocline was deeper at these stations) during Leg I (figure 3) shows that there were no significant differences between samples from these two depths, suggesting relatively rapid mixing between these depths. This indication
ANTARCTIC JOURNAL - REVIEW 1994 189
4 3.5 - 3 2.5 0
0)2 E -. 1.5 0 0)1 E 0.5
•: ., ••%•• %•
3.5
I. • S •
3 - 2.5
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E 1.5 () 01 I E 0 200 400 600 800 1,000
0.5
micro Einstein per square meter per second
3.5 Ce
0
3 2.5
..
0
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A
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V
v
A17-5m 0 A58-40m A17-40m A A66-5m A66-40m A35-40m V A74-5m V 0 A58-5m A74-40m 0 A35-5m A
100 200 300 400 500 600
micro Einstein per square meter per second
B
Figure 3. P-I characteristics of phytoplankton samples collected at 5 m and at 40 m within the upper mixed layer at five stations during Leg I. Open symbols indicate samples at 5 m; filled symbols indicate samples from 40 m.
•.% 11¼•. •b
c2 E 1.5 C) 0)1 E 0.5 F . 0
-
01 0
4 C -
2
0 A
•0 A
. . . . . . . . . . . . . . . . . .
0 200 400 600 800 1,000
References
micro Einstein per square meter per second
Figure 2. Photosynthetic assimilation numbers as a function of the mean irradiance to which the samples were exposed during the incubation period. A. Leg I. B. Leg II. of strong mixing within the upper mixed layer was also suggested by the profiles of chl-a, which generally showed a fairly uniform distribution throughout the upper mixed layer. This research was supported by National Oceanic and Atmospheric Administration (NOAA) Cooperative Agreement number NA47FR0030. We thank the officers and crew of NOAA ship Surveyor for excellent support during field operations. Grateful acknowledgment is also made to Marcel Ramos (Universidad Católica de Valparaiso, Chile), Humberto Dfaz (Universidad de Valparaiso, Chile), Pedro Baron (Universidad Nacional de la Patagonia, Argentina), and Christian Bonert (Servicio Hidrografico de la Armada, Chile) for their generous help onboard ship. Shipboard personnel included E. Walter Helbling (12 January to 9 February), Virginia Villafañe (12 January to 9 February), and Osmund Holm-Hansen (14 February to 15 March).
Heibling, E.W., and 0. Holm-Hansen. 1994. AMLR program: Distribu tion of phytoplankton in the upper water column in relation to different water masses. Antarctic Journal of the U.S., 29(5). Heibling, E.W., V.E. Vilafañe, and 0. Holm-Hansen. In press. Variability of phytoplankton distribution and primary production around Elephant Island, Antarctica, during 1990-1993. Polar Biology. Platt, T., and A.D. Jassby. 1976. The relationship between photosyn thesis and light for natural assemblages of coastal marine phytoplankton. Journal of Phycology, 12(4),421-430. Rosenberg, J.E., R.P. Hewitt, and R.S. Holt. 1994. The U.S. Antarctic Marine Living Resources (AMLR) program: 1993-1994 field season activities. Antarctic Journal of the US., 29(5). Silva S., N., M. Ramos, E.W. Helbling, and 0. Holm-Hansen. 1994. AMLR program: Depletion of inorganic nutrients in the area around Elephant Island, Antarctica. Antarctic Journal of the U.S., 29(5). Steemann Nielsen, E. 1952. The use of radiocarbon ( 14 C) for measuring organic production in the sea. Journal du Conseil International pour l'Exploration de laMer, 18(2), 117-140. Villafane, V.E., E.W. Helbling, 0. Holm-Hansen, and H. DIaz. 1994. AMLR program: Phytoplankton distribution and species composition around Elephant Island, Antarctica, January to March 1994. Antarctic Journal of the U.S., 29(5).
ANTARCTIC JOURNAL - REVIEW 1994 190
