AMLR program: Rates of primary production around
Acceptability Study for furnishing of essential equipment. Grateful acknowledgment is also made to Aldo Aguilera, Samuel Hormazabal, Sandra Rivera, and Livio Sala for their generous help on board ship. Shipboard personnel included E. Walter Helbling (11 January to 9 February), Patricio Moran (11 January to 15 March), and Osmund Holm-Hansen (14 February to 15 March).
0.16 0
0.14
0
0.12 ID 0 a) 0 0 C 0 CD
References
0.1 0.08 0.06
C ID CD a) Co
Farman, J.C., B.G. Gardiner, and J.D. Shanklin. 1985. Large losses of total ozone in Antarctica reveal seasonal CIO/NO interaction. Nature, 315(6016), 207-210. Rosenberg, J.E., R.P. Hewitt, and R.S. Holt. 1993. The U.S. Antarctic Marine Living Resources (AMLR) program: 1992-1993 field season activities. Antarctic Journal of the U.S., 28(5). Weiler, S., and P. Penhale (Eds.). In press. Ultraviolet Radiation and Biological Research in Antarctica (Antarctic Research Series). Washington, D.C.: American Geophysical Union.
0.04 0.02
0.5 1 1.5 2 2.5 3 3.5
Chlorophyll-a (mg/m3)
Figure 3. Relationship between the diffuse attenuation coefficient K PAR and chlorophyll-a concentration. The line indicates the mean square fit of the data.
AMLR program: Rates of primary production around Elephant Island, Antarctica OSMUND HOLM-HANSEN, VIRGINIA E. VILLAFAIE, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0202 LIVI0 SALA, Universidad Nacional de la Patagonia, Facultad de Ciencias Naturales, Chubut, Argentina
683 nm as a function of depth and downwelling irradiance of PAR. Water samples obtained from eight depths between 5 to 75 m were dispensed into 120-milliliter (mL) borosilicate glass bottles (two light and one dark), which were inoculated with 5.0 microcuries (iCi) of carbon-14 ( 14 C) bicarbonate. The bottles were placed in a shade-free deck incubator, which was cooled with flowing sea water, and incubated for 8-10 hours (h) centered around local apparent noon. Neutral density filters were used to attenuate solar radiation so that the samples were exposed to eight different irradiance regimes, which ranged from 95 percent to 0.5 percent of incident radiation. Incident PAR was continuously recorded (every minute), so that the amount of carbon dioxide (G0 2) fixed during the incubation period could be extrapolated to estimate total daily primary production. Rates of photosynthesis as a function of mean irradiance during the incubation period are shown in figure 1. The photosynthesis-irradiance parameters as calculated by the equation of Platt and Jassby (1976) are as follows: • 1max=27 milligrams of carbon per milligram of chlorophyll-a per hour (mg C mg chl-a' h'); • 'k=945 microeinsteins per square meter per second (tEinst m-2 sec-1); • alpha=0.029 mg C (mg chl-a hour)-' (pEinst m- 2 sec')'. There were no significant differences in photosynthetic
n important goal of the U.S. Antarctic Marine Living esources (AMLR) program is to improve understanding of the temporal and spatial characteristics of primary production in the area around Elephant Island. Villafañe et al. (Antarctic Journal, in this issue) have described various features of the standing stock of phytoplankton throughout the AMLR study area during the period from January to March 1993. In this article, we report the daily rate of primary production in the AMLR study area and discuss various factors that influence rates of phytoplankton photosynthesis. The AMLR survey grid consisted of 91 stations, each of which was sampled once during Leg I and once during Leg II between January and March 1993. The station locations have been described by Rosenberg, Hewitt, and Holt (Antarctic journal, in this issue). Upper water column characteristics and water samples from 11 depths were obtained at every station with an instrumented profiling unit consisting of a rosette containing sensors for depth, temperature, and conductivity; a pulsed in situ fluorometer (Sea Tech); a 25-cm transmissometer (Sea Tech); a solar irradiance sensor (Biospherical Instruments, Inc.,) for photosynthetically available radiation (PAR) between 400 to 700 nanometers (nm); and 1110-liter (L) Niskin bottles equipped with Teflon-covered springs. A profiling PUV-510 unit (Biospherical Instruments, Inc.,) was also deployed at selected stations [surface to 100 meters (m)] to record upwelling radiance at
ANTARCTIC JOURNAL - REVIEW 1993 191
10
Th&I0
0
• 00 • ,0000 o0.
20 -.-------
3 2.5 2 1.5 I 0.5 0
0.1
Mg C fixed/m3/day mg C fixed/m3/day I 2 q 4 s R 0 10 20 30 40 50 60
40 60 . 0 0.4 0.8 1.2 1.8 2 24 mg chi-a/m3 mg chl-a/m3 mg C fixed/m3/day mg C fixed/m3/day 0. 01020304050600123456 O t- I I I. I I
0 20 40 60 80 100 0.01! 0 250 500 750 1,000 1,250 1,500 uEIm2Is
Figure 1. Photosynthetic assimilation numbers as a function of the mean irradiance to which the samples were exposed during the incubation period. Clear circles represent data from Leg I, and solid circles are from Leg II. The inset shows photosynthetic response data at only the low irradiance values of less than 100 iEinst rn-2 sec-1.
I
20 40 60
0
Fluorescence (683 nm) Fluorescence (683 tim) 20 40 60 80 0 30 60 90 120 150 0
Figure 2. Profiles of chlorophyll-a distribution (solid circles) and rates of primary production (clear squares) throughout the euphotic zone at representative stations in water masses I, Il-Ill, IV, and V as described by Amos (Antarctic Journal, in this issue). Note change of abscissa scales in the four sets of profiles. A. Station E28 (water mass I). B. Station A48 (water masses II and Ill). C. Station A06 (water mass IV). D. Station E86 (water mass V).
40 60
0)
D 0 0.2 0.4 0.6 0.8 1 1.2 0 0.1 0.2 0.3 0.4 0.5 0.6 mg chi-a/m3 mg chl-a/m3
20
80
'a
0.1 0.2 03 0.4 0 0.3 0.6 0.9 1.2 1.5 mg chi-a/rn3 mg chi-a/m3 Fluorescence (683 nm) Fluorescence (683 nm) 30 60 90 120 1500 20 40 60 80
response between samples from Leg I as compared with Leg II. The assimilation numbers are fairly high (2 to 4) at saturating light levels and show no significant inhibition at the highest irradiance values. The distribution of phytoplankton in the upper water column was quite different in the major water masses described in the AMLR study area by Amos (Antarctic Journal, in this issue), and this was reflected in the profiles of primary production in the euphotic zone (figure 2). Lowest values for chlorophyll-a and primary production are found in water masses I and V. In water mass I, chlorophyll-a values are low (0.1 mg m 3 ) in the upper 50 m and increase significantly between 50 and 100 m (figure 2A). Phytoplankton biomass in water mass V is also low (0.1 mg chlorophyll-a m 3 ) but does not increase with depth in the euphotic zone (figure 2D). Highest chlorophyll-a values, as well as rates of primary production, were found in water masses II, III, and IV (figures 2B and 2C, respectively). The integrated rates of primary production at stations A48 (figure 2B) and A06 (figure 2C were 1,149 and 927 mg C fixed m- 2 per day ( d 1 ), respectively, as compared to values of 75 and 160 for stations E28 (figure 2A) and E86 (figure 2D), respectively. The mean primary production values when integrated for the entire euphotic zone throughout the entire AMLR grid were 716 mg C m-2 d' in Leg I and
20 40 60 1.., 80 '' 0 0.3 0.6 0.9 1.2 1.5 0 0.1 0.2 0.3 0.4 mg chi-a/m3 mg chi-a/m3 Figure 3. Upwelling radiance at 683 nm (dashed line) and chlorophyll-a concentrations (solid circles) in the upper water column at stations representative of different water masses in the AMLR study area. Profiles for each station show chlorophyll-a concentrations at standard depths and relative rates of photosynthesis (not absolute rates) as estimated with the profiling radiance meter. Data on upwelling radiance in the upper 5 m have been deleted at each station because scattered downwelling solar irradiance at 683 nm can be detected down to at least 5 m depth. A. Station E41 (water mass I). B. Station A73 (water mass II). C. Station A34 (water mass IV). D. Station A83 (water mass V).
ANTARCTIC JOURNAL 192
REVIEW 1993
cruise and also Samuel Hormazabal and Sandra Rivera for help on board ship. Shipboard personnel included E. Walter Helbling and Virginia E. Villafafie (11 January to 9 February) and Osmund Holm-Hansen and Uvio Sala (14 February to 15 March).
311 mg C rn- 2 d-' in Leg II. The decrease in rates of primary production from Leg I to Leg II reflects the lower standing stock of phytoplankton in Leg II as compared to that in Leg I (Villafafle et at, Antarctic Journal, in this issue), in addition to lower incident irradiance values in February and March as compared with January (see Helbling, Moran, and HolmHansen, Antarctic Journal, in this issue). Profiles of upwelling radiance at 683 nm, which are indicative of in situ rates of photosynthesis (Chamberlin et al. 1990), are shown in figure 3. It is seen that the profile obtained in water mass I (figure 3A) is very different from the other profiles in that there is a deep subsurface maximum in the rate of photosynthesis at approximately 50-m depth. The fluorescence profiles at stations A34 (figure 3C, water mass IV) and A83 (figure 3D, water mass V) are highest in surface waters and decrease rapidly with depth in the upper water column. Station A73 (figure 3B, water mass II) has a small maximum at 22 m, a maximum that corresponded to the bottom of the upper mixed layer where the chlorophyll-a values were also slightly higher than at 10 m. This research was supported by National Oceanic and Atmospheric Administration (NOAA) cooperative agreement number NA3717110001-01. We thank the officers and crew of NOAA ship Surveyor for excellent support during the entire
References Amos, A.F. 1993. AMLR program: Interannual variability in the Elephant Island surface waters in the austral summer. Antarctic Journalof the U.S., 28(5). Chamberlin, W.S., C.R. Booth, D.A. Kiefer, J.H. Morrow, and R.C. Murphy. 1990. Evidence for a simple relationship between natural fluorescence, photosynthesis and chlorophyll in the sea. Deep-Sea Research, 37(6), 951-973. Helbling, E.W., P. Moran, and 0. Holm-Hansen. 1993. AMLR program: Ultraviolet and visible solar irradiance around Elephant Island, Antarctica, January to March 1993. Antarctic Journal of the U.S., 28(5). Platt, T., and A.D. Jassby. 1976. The relationship between photosynthesis and light for natural assemblages of coastal marine phytoplankton. Journal of Phycology, 12(4), 421-430. Rosenberg, I.E., R.P. Hewitt, and R.S. Holt. 1993. The U.S. Antarctic Marine Living Resources (AMLR) program: 1992-1993 field season activities. Antarctic Journal of the U.S., 28(5). Villafafle, V.E., 0. Holm-Hansen, E.W. Helbling, and S.G. Rivera. 1993. AMLR program: Distribution of phytoplankton biomass around Elephant Island, Antarctica, January to March 1993. Antarctic Journal of the U.S., 28(5).
AMLR program: Distribution of phytoplankton biomass around Elephant Island, Antarctica, January to March 1993 VIRGINIA E. VILLAFA1SEE, OSMuND HOLM-HANSEN, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 93093-0202 SANDRA G. RIVERA, Universidad Nacional de la Patagonia, Facultad de Ciencias Naturales, Chubut, Argentina
occupied two times between January and March. The station positions are given in Rosenberg et al. (Antarctic Journal, in this issue). Phytoplankton biomass was estimated by three different methods: • determination of chlorophyll-a concentrations, • direct microscopic counts, with cell measurements, and subsequent calculation of cellular organic carbon, and • estimation of particulate organic carbon (POC) from beam-attenuation coefficients measured with the transmissometer. The total concentration of chlorophyll-a in phytoplankton was determined by filtering 100 milliliters (mL) of unscreened sample onto a GF/F Whatman glass fiber filter and extracting the chlorophyll in 10 mL of absolute methanol (Holm-Hansen and Riemann 1978). The fluorescence of the extract was then measured in a Turner Designs fluorometer, model 10-005R (Holm-Hansen et al. 1965). To determine the chlorophyll-a content of nanoplankton [less than 20 micrometers (tm) in diameter], replicate water samples were first fil-
ne of the major objectives of the phytoplankton compoO nent of the Antarctic Marine Living Resources (AMLR) program is to determine the distribution and abundance of the food reservoir available to herbivorous zooplankton, including the antarctic krill Euphausia superba. In this article, we report on the distribution and biomass of phytoplankton throughout the AMLR study area (see Rosenberg, Hewitt, and Holt, Antarctic Journal, in this issue) and provide data on the relative abundance of nanoplankton and microplankton and the dominant species in the microplankton size category. Using Niskin bottles mounted on a rosette (General Oceanics), we collected water samples at 10 standard depths between 5 and 200 meters (m). In addition to sensors for conductivity, depth, and temperature, the profiling unit, which was deployed at all stations, had attached to it a 25-centimeter (cm) pathlength transmissometer (Sea Tech), a sensor for photosynthetically available radiation [PAR, 400-700 nanometers (nm)], and a pulsed fluorometer (Sea Tech). There were 91 stations in the survey grid, all of which were
ANTARCTIC JOURNAL - REVIEW 1993 193
0.16 0
0.14
0
0.12 ID 0 a) 0 0 C 0 CD
References
0.1 0.08 0.06
C ID CD a) Co
Farman, J.C., B.G. Gardiner, and J.D. Shanklin. 1985. Large losses of total ozone in Antarctica reveal seasonal CIO/NO interaction. Nature, 315(6016), 207-210. Rosenberg, J.E., R.P. Hewitt, and R.S. Holt. 1993. The U.S. Antarctic Marine Living Resources (AMLR) program: 1992-1993 field season activities. Antarctic Journal of the U.S., 28(5). Weiler, S., and P. Penhale (Eds.). In press. Ultraviolet Radiation and Biological Research in Antarctica (Antarctic Research Series). Washington, D.C.: American Geophysical Union.
0.04 0.02
0.5 1 1.5 2 2.5 3 3.5
Chlorophyll-a (mg/m3)
Figure 3. Relationship between the diffuse attenuation coefficient K PAR and chlorophyll-a concentration. The line indicates the mean square fit of the data.
AMLR program: Rates of primary production around Elephant Island, Antarctica OSMUND HOLM-HANSEN, VIRGINIA E. VILLAFAIE, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0202 LIVI0 SALA, Universidad Nacional de la Patagonia, Facultad de Ciencias Naturales, Chubut, Argentina
683 nm as a function of depth and downwelling irradiance of PAR. Water samples obtained from eight depths between 5 to 75 m were dispensed into 120-milliliter (mL) borosilicate glass bottles (two light and one dark), which were inoculated with 5.0 microcuries (iCi) of carbon-14 ( 14 C) bicarbonate. The bottles were placed in a shade-free deck incubator, which was cooled with flowing sea water, and incubated for 8-10 hours (h) centered around local apparent noon. Neutral density filters were used to attenuate solar radiation so that the samples were exposed to eight different irradiance regimes, which ranged from 95 percent to 0.5 percent of incident radiation. Incident PAR was continuously recorded (every minute), so that the amount of carbon dioxide (G0 2) fixed during the incubation period could be extrapolated to estimate total daily primary production. Rates of photosynthesis as a function of mean irradiance during the incubation period are shown in figure 1. The photosynthesis-irradiance parameters as calculated by the equation of Platt and Jassby (1976) are as follows: • 1max=27 milligrams of carbon per milligram of chlorophyll-a per hour (mg C mg chl-a' h'); • 'k=945 microeinsteins per square meter per second (tEinst m-2 sec-1); • alpha=0.029 mg C (mg chl-a hour)-' (pEinst m- 2 sec')'. There were no significant differences in photosynthetic
n important goal of the U.S. Antarctic Marine Living esources (AMLR) program is to improve understanding of the temporal and spatial characteristics of primary production in the area around Elephant Island. Villafañe et al. (Antarctic Journal, in this issue) have described various features of the standing stock of phytoplankton throughout the AMLR study area during the period from January to March 1993. In this article, we report the daily rate of primary production in the AMLR study area and discuss various factors that influence rates of phytoplankton photosynthesis. The AMLR survey grid consisted of 91 stations, each of which was sampled once during Leg I and once during Leg II between January and March 1993. The station locations have been described by Rosenberg, Hewitt, and Holt (Antarctic journal, in this issue). Upper water column characteristics and water samples from 11 depths were obtained at every station with an instrumented profiling unit consisting of a rosette containing sensors for depth, temperature, and conductivity; a pulsed in situ fluorometer (Sea Tech); a 25-cm transmissometer (Sea Tech); a solar irradiance sensor (Biospherical Instruments, Inc.,) for photosynthetically available radiation (PAR) between 400 to 700 nanometers (nm); and 1110-liter (L) Niskin bottles equipped with Teflon-covered springs. A profiling PUV-510 unit (Biospherical Instruments, Inc.,) was also deployed at selected stations [surface to 100 meters (m)] to record upwelling radiance at
ANTARCTIC JOURNAL - REVIEW 1993 191
10
Th&I0
0
• 00 • ,0000 o0.
20 -.-------
3 2.5 2 1.5 I 0.5 0
0.1
Mg C fixed/m3/day mg C fixed/m3/day I 2 q 4 s R 0 10 20 30 40 50 60
40 60 . 0 0.4 0.8 1.2 1.8 2 24 mg chi-a/m3 mg chl-a/m3 mg C fixed/m3/day mg C fixed/m3/day 0. 01020304050600123456 O t- I I I. I I
0 20 40 60 80 100 0.01! 0 250 500 750 1,000 1,250 1,500 uEIm2Is
Figure 1. Photosynthetic assimilation numbers as a function of the mean irradiance to which the samples were exposed during the incubation period. Clear circles represent data from Leg I, and solid circles are from Leg II. The inset shows photosynthetic response data at only the low irradiance values of less than 100 iEinst rn-2 sec-1.
I
20 40 60
0
Fluorescence (683 nm) Fluorescence (683 tim) 20 40 60 80 0 30 60 90 120 150 0
Figure 2. Profiles of chlorophyll-a distribution (solid circles) and rates of primary production (clear squares) throughout the euphotic zone at representative stations in water masses I, Il-Ill, IV, and V as described by Amos (Antarctic Journal, in this issue). Note change of abscissa scales in the four sets of profiles. A. Station E28 (water mass I). B. Station A48 (water masses II and Ill). C. Station A06 (water mass IV). D. Station E86 (water mass V).
40 60
0)
D 0 0.2 0.4 0.6 0.8 1 1.2 0 0.1 0.2 0.3 0.4 0.5 0.6 mg chi-a/m3 mg chl-a/m3
20
80
'a
0.1 0.2 03 0.4 0 0.3 0.6 0.9 1.2 1.5 mg chi-a/rn3 mg chi-a/m3 Fluorescence (683 nm) Fluorescence (683 nm) 30 60 90 120 1500 20 40 60 80
response between samples from Leg I as compared with Leg II. The assimilation numbers are fairly high (2 to 4) at saturating light levels and show no significant inhibition at the highest irradiance values. The distribution of phytoplankton in the upper water column was quite different in the major water masses described in the AMLR study area by Amos (Antarctic Journal, in this issue), and this was reflected in the profiles of primary production in the euphotic zone (figure 2). Lowest values for chlorophyll-a and primary production are found in water masses I and V. In water mass I, chlorophyll-a values are low (0.1 mg m 3 ) in the upper 50 m and increase significantly between 50 and 100 m (figure 2A). Phytoplankton biomass in water mass V is also low (0.1 mg chlorophyll-a m 3 ) but does not increase with depth in the euphotic zone (figure 2D). Highest chlorophyll-a values, as well as rates of primary production, were found in water masses II, III, and IV (figures 2B and 2C, respectively). The integrated rates of primary production at stations A48 (figure 2B) and A06 (figure 2C were 1,149 and 927 mg C fixed m- 2 per day ( d 1 ), respectively, as compared to values of 75 and 160 for stations E28 (figure 2A) and E86 (figure 2D), respectively. The mean primary production values when integrated for the entire euphotic zone throughout the entire AMLR grid were 716 mg C m-2 d' in Leg I and
20 40 60 1.., 80 '' 0 0.3 0.6 0.9 1.2 1.5 0 0.1 0.2 0.3 0.4 mg chi-a/m3 mg chi-a/m3 Figure 3. Upwelling radiance at 683 nm (dashed line) and chlorophyll-a concentrations (solid circles) in the upper water column at stations representative of different water masses in the AMLR study area. Profiles for each station show chlorophyll-a concentrations at standard depths and relative rates of photosynthesis (not absolute rates) as estimated with the profiling radiance meter. Data on upwelling radiance in the upper 5 m have been deleted at each station because scattered downwelling solar irradiance at 683 nm can be detected down to at least 5 m depth. A. Station E41 (water mass I). B. Station A73 (water mass II). C. Station A34 (water mass IV). D. Station A83 (water mass V).
ANTARCTIC JOURNAL 192
REVIEW 1993
cruise and also Samuel Hormazabal and Sandra Rivera for help on board ship. Shipboard personnel included E. Walter Helbling and Virginia E. Villafafie (11 January to 9 February) and Osmund Holm-Hansen and Uvio Sala (14 February to 15 March).
311 mg C rn- 2 d-' in Leg II. The decrease in rates of primary production from Leg I to Leg II reflects the lower standing stock of phytoplankton in Leg II as compared to that in Leg I (Villafafle et at, Antarctic Journal, in this issue), in addition to lower incident irradiance values in February and March as compared with January (see Helbling, Moran, and HolmHansen, Antarctic Journal, in this issue). Profiles of upwelling radiance at 683 nm, which are indicative of in situ rates of photosynthesis (Chamberlin et al. 1990), are shown in figure 3. It is seen that the profile obtained in water mass I (figure 3A) is very different from the other profiles in that there is a deep subsurface maximum in the rate of photosynthesis at approximately 50-m depth. The fluorescence profiles at stations A34 (figure 3C, water mass IV) and A83 (figure 3D, water mass V) are highest in surface waters and decrease rapidly with depth in the upper water column. Station A73 (figure 3B, water mass II) has a small maximum at 22 m, a maximum that corresponded to the bottom of the upper mixed layer where the chlorophyll-a values were also slightly higher than at 10 m. This research was supported by National Oceanic and Atmospheric Administration (NOAA) cooperative agreement number NA3717110001-01. We thank the officers and crew of NOAA ship Surveyor for excellent support during the entire
References Amos, A.F. 1993. AMLR program: Interannual variability in the Elephant Island surface waters in the austral summer. Antarctic Journalof the U.S., 28(5). Chamberlin, W.S., C.R. Booth, D.A. Kiefer, J.H. Morrow, and R.C. Murphy. 1990. Evidence for a simple relationship between natural fluorescence, photosynthesis and chlorophyll in the sea. Deep-Sea Research, 37(6), 951-973. Helbling, E.W., P. Moran, and 0. Holm-Hansen. 1993. AMLR program: Ultraviolet and visible solar irradiance around Elephant Island, Antarctica, January to March 1993. Antarctic Journal of the U.S., 28(5). Platt, T., and A.D. Jassby. 1976. The relationship between photosynthesis and light for natural assemblages of coastal marine phytoplankton. Journal of Phycology, 12(4), 421-430. Rosenberg, I.E., R.P. Hewitt, and R.S. Holt. 1993. The U.S. Antarctic Marine Living Resources (AMLR) program: 1992-1993 field season activities. Antarctic Journal of the U.S., 28(5). Villafafle, V.E., 0. Holm-Hansen, E.W. Helbling, and S.G. Rivera. 1993. AMLR program: Distribution of phytoplankton biomass around Elephant Island, Antarctica, January to March 1993. Antarctic Journal of the U.S., 28(5).
AMLR program: Distribution of phytoplankton biomass around Elephant Island, Antarctica, January to March 1993 VIRGINIA E. VILLAFA1SEE, OSMuND HOLM-HANSEN, and E. WALTER HELBLING, Polar Research Program, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 93093-0202 SANDRA G. RIVERA, Universidad Nacional de la Patagonia, Facultad de Ciencias Naturales, Chubut, Argentina
occupied two times between January and March. The station positions are given in Rosenberg et al. (Antarctic Journal, in this issue). Phytoplankton biomass was estimated by three different methods: • determination of chlorophyll-a concentrations, • direct microscopic counts, with cell measurements, and subsequent calculation of cellular organic carbon, and • estimation of particulate organic carbon (POC) from beam-attenuation coefficients measured with the transmissometer. The total concentration of chlorophyll-a in phytoplankton was determined by filtering 100 milliliters (mL) of unscreened sample onto a GF/F Whatman glass fiber filter and extracting the chlorophyll in 10 mL of absolute methanol (Holm-Hansen and Riemann 1978). The fluorescence of the extract was then measured in a Turner Designs fluorometer, model 10-005R (Holm-Hansen et al. 1965). To determine the chlorophyll-a content of nanoplankton [less than 20 micrometers (tm) in diameter], replicate water samples were first fil-
ne of the major objectives of the phytoplankton compoO nent of the Antarctic Marine Living Resources (AMLR) program is to determine the distribution and abundance of the food reservoir available to herbivorous zooplankton, including the antarctic krill Euphausia superba. In this article, we report on the distribution and biomass of phytoplankton throughout the AMLR study area (see Rosenberg, Hewitt, and Holt, Antarctic Journal, in this issue) and provide data on the relative abundance of nanoplankton and microplankton and the dominant species in the microplankton size category. Using Niskin bottles mounted on a rosette (General Oceanics), we collected water samples at 10 standard depths between 5 and 200 meters (m). In addition to sensors for conductivity, depth, and temperature, the profiling unit, which was deployed at all stations, had attached to it a 25-centimeter (cm) pathlength transmissometer (Sea Tech), a sensor for photosynthetically available radiation [PAR, 400-700 nanometers (nm)], and a pulsed fluorometer (Sea Tech). There were 91 stations in the survey grid, all of which were
ANTARCTIC JOURNAL - REVIEW 1993 193
