Phytoplankton photosynthesis- irradiance relationships during austral ...
low the euphotic zone and subsequent transport throughout the water column by grazing zooplankton, with eventual release of some viable spores from fecal matter. Indicators. Coscinodiscus oculoides Karsten, a large-celled diatom (Fryxell and Ashworth, 1988) was the only species in the genus to be common near the pack ice. An austral summer transect (Fryxell, Antarctic Journal, this issue) south from the northern Kerguelen Plateau strengthened previous work on indicator species and varieties. Azpeitia tabularis was seen mainly north of the Antarctic Convergence Zone, as were varieties of Thalassiosira tumida and Eucampia antarctica. Far to the south in Prydz Bay, Antarctica, in an area recently cleared of ice by a gale, the ice-edge varieties of the latter two were seen instead, and are under study. Comparison of the floras, time-averaged in sediment, is very promising and adds a new time scale to work resulting from combined biological and geological sampling. For the first time, a method of making permanent mounts in a water-soluble, methacrylic resin was used aboard ship for quantitative estimates from water samples (Crumpton 1987). A comparative study is underway by Kang. This work was supported in part by National Science Foundation grants DPP 82-18491 and DPP 84-18850, supplemented by Research Experiences for Undergraduates, which are much
appreciated. M. Mann and T.K. Ashworth provided technical assistance with the figures. Figure 3 is credited to B.R. Bogle.
Phytoplankton photosynthesisirradiance relationships during austral winter in the Bransfield Strait region
Water samples were collected onboard the WV Polar Duke during austral winter from the Bransfield Strait region in Antarctica (figure 1). These samples were used to determine chlorophyll a concentrations, biogenic silica, particulate organic carbon and nitrogen concentration, photosynthesis-irradiance responses, and simulated in situ primary productivity (Brightman and Smith unpublished data). Samples were collected at both open-water and ice-covered stations at depths from 0 to 150 meters. A quantum meter was used to determine the depth of the euphotic zone and an expendable-bathythermograph (XBT) was used to detect any thermal stratification within the water column. Incident irradiance was recorded throughout the sampling period. Photosynthesis-irradiance relationships (P-I curves) were determined using short-term incubations (2-4 hours) and 5milliliter samples (procedure adapted from Lewis and Smith 1983). Photosynthetic rates (chlorophyll-specific) were calculated using estimates of carbon-14-uptake measurements over a range of irradiances (10-2,000 microeinsteins per square meter per second). Photosynthetic parameters were derived from the objective curve-fitting procedures of Zimmerman et al. (1987) by fitting the data to the equation of Platt, Gallegos, and Harrison (1980):
Ross I. BRIGHTMAN* and WALKER 0. SMITH, JR. Graduate Program in Ecology University of Tennessee Knoxville, Tennessee 37996
Participation in WINCRUISE II during June and July of 1987 offered an opportunity to study phytoplankton photosynthetic responses during the reduced light and photoperiods of austral winter. Despite significant amounts of light which are present at the northern reaches of the ice-edge in winter, little is known about the productivity and biomass of phytoplankton populations during this period. The objective of this study was to determine the biomass and distribution of phytoplankton during austral winter, the photosynthesis-irradiance relationships of the winter populations, and contributions of any primary productivity during the winter period to the annual carbon cycle in comparison to other seasons and locations.
* Present address: Department of Marine Science, University of South Florida, St. Petersburg, Florida 33701-5016.
1988 REVIEW
References
Bidigare, R.R. 1988. Personal communication. Crumpton, W.G. 1987. A simple and reliable method for making permanent mounts of phytoplankton for light and fluorescence microscopy. Limnology and Oceanography, 32(5), 1154-1159. Fryxell, G.A. In preparation. Marine phytoplankton at the Weddell Sea ice edge: Seasonal changes at the specific level. Fryxell, G.A., and T.K. Ashworth. 1988. The diatom genus Coscinodiscus Ehrenberg: Characters having taxonomic value. Botanica Marina, 31, 359-374.
Fryxell, GA., S-H Kang, and M.E. Reap. 1987. AMERIEZ 1986: Phytoplanton at the Weddell Sea ice edge. Antarctic Journal of the U.S., 22(5), 173-175.
Fryxell, GA., and G.A. Kendrick. 1988. Austral spring microalgae across the Weddell Sea ice edge; spatial relationships found along a northward transect during AMERIEZ 83. Deep-Sea Research, 35(1), 1-20.
Fryxell, GA., and Shipboard Party. 1988. Southern Indian Ocean cruise of JOIDES Resolution (Ocean Drilling Program leg 119). 23(5). Jahnke, J., and M.E.M. Baumann. 1987. Differentiation between Phaeocystis pouchetii (Har.) Lagerheim and Phaeocystis globosa Scherffel. Hydrobiology Bulletin, 21(2), 141-147.
pB(J)
= P(1 -e"°) e'
where p' = the photosynthetic rate (milligrams of carbon per milligram of chlorophyll a per hour) at irradiance I (microeinsteins per square meter per second) P = the light-saturated photosynthetic rate (same units as PB) in the absence of photoinhibition, 131
450 W
45°E
61°S
900 W
62°S
630S
64°S
630S
64°S
65°S 67 0 W 66 0 W 65 0 W 64 0 W 63 0 W 62 0 W 61°W 60°W 590W Figure 1. Location of stations occupied in the Bransfield Strait region.
a = the initial light dependent slope of the P-I curve (milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second), and 13 = an index of photoinhibition (same units as a). In addition, the maximum photosynthetic rate attained (P) was calculated using the equation of Platt, Gallegos, and Harrison (1980): P =
P[aI(a + 13)]
[13/(a + I3)]
and the index of photoadaptation (Ik) was estimated from I k = PI()( Chlorophyll a concentrations averaged 0.183 micrograms per liter (±0.09) at the surface and 0.175 micrograms per liter (± 0.14 at 50 meters, slightly less but not significantly different from those of the surface. Particulate organic carbon averaged 66.3 milligrams of carbon per cubic meter (± 51.8) in surface 132
waters and 47.5 milligrams of carbon per cubic meter for 50meter samples. Particulate organic nitrogen averaged 9.9 milligrams of nitrogen per cubic meter (± 8.2) and 8.5 milligrams of nitrogen per cubic meter (±5.1) for surface and 50-meter samples, respectively. Photosynthesis-irradiance parameters within the Bransfield Strait showed little depth-dependent variation within each station (figure 2). Photosynthetic efficiencies (a) were high, averaging 0.21 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (±0.01) for surface waters and 0.31 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (± 0.02) for 50 meters. Assimilation numbers (P) averaged 1.19 milligrams of carbon per milligram of chlorophyll a per hour (±0.58) for surface waters and 1.10 milligrams of carbon per milligram of chlorophyll a per hour (± 0.06) for 50-meter populations. Light intensities required to saturate photosynthesis were low and averaged approximately 45 microeinsteins per square meter per second. Photoinhibition was ANTARCTIC JOURNAL
1.5
1.2
.9
.6
.c C.)
E 0
E
0 0 400 800 1200 1600 2000 2400
1.5
1.2
CL
present in both surface and in 50-meter populations and was initiated at approximately 300 microeinsteins per square meter per second, with 13 values averaging 0.001 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (±0.0001). The large values for photosynthetic efficiencies and the low 'k values indicate that the phytoplankton populations were adapted to low-light conditions (Prezelin 1981). Furthermore, these values were similar to those of ice-algal populations, which grow in low-light conditions (Cota 1985). Absence of vertical variation among photosynthetic parameters within the water column suggests that the time scale of photoadaptation of the phytoplankton populations was less than the time scale of vertical mixing within the water column. We would like to acknowledge P. Boyce and D. Vogelin for field assistance and L. Clotfelter for assistance in sample and data processing. This research was supported by National Science Foundation grant DPP 84-20213 (AMERIEZ). Shiptime was provided by L. Quetin and supported by National Science Foundation grant DPP 85-18872.
References
0 0 400 800 1200 1600 2000 2400
Irradiance (PE n'i•2 s) Figure 2. Photosynthesis as a function of irradiance at 0 and 50 meters at station 112 (total depth 150 meters). (Irradiance is measured In mlcroeinsteins per square meter per second. pB is measured In milligrams of carbon per milligram of chlorophyll a per hour.)
Lipid biochemistry of antarctic zooplankton: Overwintering strategies and trophic relationships W. HAGEN* and
E.S. VAN VLEET
University of South Florida Department of Marine Science St. Petersburg, Florida 33701
Lipids are the major energy store for many marine animals in polar regions, classic examples being the whales, seals, and * Also affiliated with Inst it ut für Polarokologie, Kiel University, Kiel, Fed eral Republic of Germany.
1988 REVIEW
Cota, G.F. 1985. Photoadaptation of high Arctic ice algae. Nature, 315, 219-222. Lewis, M. R., and J. C. Smith. 1983. A small volume, short incubationtime method for measurement of photosynthesis as a function of incident irradiance. Marine Ecology Progress Series, 13, 99-102. Platt, T., C.L. Gallegos, and W.G. Harrison, 1980. Photoinhibition of the photosynthesis in the natural assemblages of the marine phytoplankton. Journal of Marine Research, 38, 687-701. Prezelin, B.B. 1981. In T. Platt (Ed.), Physiological bases of phytoplankton ecology. Canadian Journal of Fisheries and Aquatic Sciences, 210, 1-43. Zimmerman, R.C., J.B. SooHoo, J.M. Kremer, and D.Z. D'Argenio. 1987. An evaluation of variance approximation techniques for nonlinear photosynthesis-irradiance models. Marine Biology, 95, 209215.
penguins. Previous biochemical studies on polar plankton organisms have focused on lipids to elucidate the significance of these compounds in relation to the marked seasonality of the polar light and ice regime. Due to the absence of light, phytoplankton is absent during the wintertime, and one major question concerning the functioning of the marine antarctic ecosystem is how the zooplankton, especially the herbivorous species (krill, copepods, etc.), survive during this extended period of food scarcity. There are a number of hypotheses suggesting different overwintering strategies, one of which is the use of high-energy compounds such as lipids during starvation periods. Previous investigations of the lipid biochemistry of antarctic plankton communities have been carried out for the first time by Reinhardt and Van Vleet (1986a, 1986b) and Hagen (1988) on spring and summer samples from the Antarctic Peninsula and the southern Weddell Sea. Results show high accumulation of lipid stores in many plankton organisms, particularly in crustaceans and fish; however, due to severe ice and weather conditions, very few lipid data are available from plankton 133
appreciated. M. Mann and T.K. Ashworth provided technical assistance with the figures. Figure 3 is credited to B.R. Bogle.
Phytoplankton photosynthesisirradiance relationships during austral winter in the Bransfield Strait region
Water samples were collected onboard the WV Polar Duke during austral winter from the Bransfield Strait region in Antarctica (figure 1). These samples were used to determine chlorophyll a concentrations, biogenic silica, particulate organic carbon and nitrogen concentration, photosynthesis-irradiance responses, and simulated in situ primary productivity (Brightman and Smith unpublished data). Samples were collected at both open-water and ice-covered stations at depths from 0 to 150 meters. A quantum meter was used to determine the depth of the euphotic zone and an expendable-bathythermograph (XBT) was used to detect any thermal stratification within the water column. Incident irradiance was recorded throughout the sampling period. Photosynthesis-irradiance relationships (P-I curves) were determined using short-term incubations (2-4 hours) and 5milliliter samples (procedure adapted from Lewis and Smith 1983). Photosynthetic rates (chlorophyll-specific) were calculated using estimates of carbon-14-uptake measurements over a range of irradiances (10-2,000 microeinsteins per square meter per second). Photosynthetic parameters were derived from the objective curve-fitting procedures of Zimmerman et al. (1987) by fitting the data to the equation of Platt, Gallegos, and Harrison (1980):
Ross I. BRIGHTMAN* and WALKER 0. SMITH, JR. Graduate Program in Ecology University of Tennessee Knoxville, Tennessee 37996
Participation in WINCRUISE II during June and July of 1987 offered an opportunity to study phytoplankton photosynthetic responses during the reduced light and photoperiods of austral winter. Despite significant amounts of light which are present at the northern reaches of the ice-edge in winter, little is known about the productivity and biomass of phytoplankton populations during this period. The objective of this study was to determine the biomass and distribution of phytoplankton during austral winter, the photosynthesis-irradiance relationships of the winter populations, and contributions of any primary productivity during the winter period to the annual carbon cycle in comparison to other seasons and locations.
* Present address: Department of Marine Science, University of South Florida, St. Petersburg, Florida 33701-5016.
1988 REVIEW
References
Bidigare, R.R. 1988. Personal communication. Crumpton, W.G. 1987. A simple and reliable method for making permanent mounts of phytoplankton for light and fluorescence microscopy. Limnology and Oceanography, 32(5), 1154-1159. Fryxell, G.A. In preparation. Marine phytoplankton at the Weddell Sea ice edge: Seasonal changes at the specific level. Fryxell, G.A., and T.K. Ashworth. 1988. The diatom genus Coscinodiscus Ehrenberg: Characters having taxonomic value. Botanica Marina, 31, 359-374.
Fryxell, GA., S-H Kang, and M.E. Reap. 1987. AMERIEZ 1986: Phytoplanton at the Weddell Sea ice edge. Antarctic Journal of the U.S., 22(5), 173-175.
Fryxell, GA., and G.A. Kendrick. 1988. Austral spring microalgae across the Weddell Sea ice edge; spatial relationships found along a northward transect during AMERIEZ 83. Deep-Sea Research, 35(1), 1-20.
Fryxell, GA., and Shipboard Party. 1988. Southern Indian Ocean cruise of JOIDES Resolution (Ocean Drilling Program leg 119). 23(5). Jahnke, J., and M.E.M. Baumann. 1987. Differentiation between Phaeocystis pouchetii (Har.) Lagerheim and Phaeocystis globosa Scherffel. Hydrobiology Bulletin, 21(2), 141-147.
pB(J)
= P(1 -e"°) e'
where p' = the photosynthetic rate (milligrams of carbon per milligram of chlorophyll a per hour) at irradiance I (microeinsteins per square meter per second) P = the light-saturated photosynthetic rate (same units as PB) in the absence of photoinhibition, 131
450 W
45°E
61°S
900 W
62°S
630S
64°S
630S
64°S
65°S 67 0 W 66 0 W 65 0 W 64 0 W 63 0 W 62 0 W 61°W 60°W 590W Figure 1. Location of stations occupied in the Bransfield Strait region.
a = the initial light dependent slope of the P-I curve (milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second), and 13 = an index of photoinhibition (same units as a). In addition, the maximum photosynthetic rate attained (P) was calculated using the equation of Platt, Gallegos, and Harrison (1980): P =
P[aI(a + 13)]
[13/(a + I3)]
and the index of photoadaptation (Ik) was estimated from I k = PI()( Chlorophyll a concentrations averaged 0.183 micrograms per liter (±0.09) at the surface and 0.175 micrograms per liter (± 0.14 at 50 meters, slightly less but not significantly different from those of the surface. Particulate organic carbon averaged 66.3 milligrams of carbon per cubic meter (± 51.8) in surface 132
waters and 47.5 milligrams of carbon per cubic meter for 50meter samples. Particulate organic nitrogen averaged 9.9 milligrams of nitrogen per cubic meter (± 8.2) and 8.5 milligrams of nitrogen per cubic meter (±5.1) for surface and 50-meter samples, respectively. Photosynthesis-irradiance parameters within the Bransfield Strait showed little depth-dependent variation within each station (figure 2). Photosynthetic efficiencies (a) were high, averaging 0.21 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (±0.01) for surface waters and 0.31 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (± 0.02) for 50 meters. Assimilation numbers (P) averaged 1.19 milligrams of carbon per milligram of chlorophyll a per hour (±0.58) for surface waters and 1.10 milligrams of carbon per milligram of chlorophyll a per hour (± 0.06) for 50-meter populations. Light intensities required to saturate photosynthesis were low and averaged approximately 45 microeinsteins per square meter per second. Photoinhibition was ANTARCTIC JOURNAL
1.5
1.2
.9
.6
.c C.)
E 0
E
0 0 400 800 1200 1600 2000 2400
1.5
1.2
CL
present in both surface and in 50-meter populations and was initiated at approximately 300 microeinsteins per square meter per second, with 13 values averaging 0.001 milligrams of carbon per milligram of chlorophyll a per hour per microeinstein per square meter per second (±0.0001). The large values for photosynthetic efficiencies and the low 'k values indicate that the phytoplankton populations were adapted to low-light conditions (Prezelin 1981). Furthermore, these values were similar to those of ice-algal populations, which grow in low-light conditions (Cota 1985). Absence of vertical variation among photosynthetic parameters within the water column suggests that the time scale of photoadaptation of the phytoplankton populations was less than the time scale of vertical mixing within the water column. We would like to acknowledge P. Boyce and D. Vogelin for field assistance and L. Clotfelter for assistance in sample and data processing. This research was supported by National Science Foundation grant DPP 84-20213 (AMERIEZ). Shiptime was provided by L. Quetin and supported by National Science Foundation grant DPP 85-18872.
References
0 0 400 800 1200 1600 2000 2400
Irradiance (PE n'i•2 s) Figure 2. Photosynthesis as a function of irradiance at 0 and 50 meters at station 112 (total depth 150 meters). (Irradiance is measured In mlcroeinsteins per square meter per second. pB is measured In milligrams of carbon per milligram of chlorophyll a per hour.)
Lipid biochemistry of antarctic zooplankton: Overwintering strategies and trophic relationships W. HAGEN* and
E.S. VAN VLEET
University of South Florida Department of Marine Science St. Petersburg, Florida 33701
Lipids are the major energy store for many marine animals in polar regions, classic examples being the whales, seals, and * Also affiliated with Inst it ut für Polarokologie, Kiel University, Kiel, Fed eral Republic of Germany.
1988 REVIEW
Cota, G.F. 1985. Photoadaptation of high Arctic ice algae. Nature, 315, 219-222. Lewis, M. R., and J. C. Smith. 1983. A small volume, short incubationtime method for measurement of photosynthesis as a function of incident irradiance. Marine Ecology Progress Series, 13, 99-102. Platt, T., C.L. Gallegos, and W.G. Harrison, 1980. Photoinhibition of the photosynthesis in the natural assemblages of the marine phytoplankton. Journal of Marine Research, 38, 687-701. Prezelin, B.B. 1981. In T. Platt (Ed.), Physiological bases of phytoplankton ecology. Canadian Journal of Fisheries and Aquatic Sciences, 210, 1-43. Zimmerman, R.C., J.B. SooHoo, J.M. Kremer, and D.Z. D'Argenio. 1987. An evaluation of variance approximation techniques for nonlinear photosynthesis-irradiance models. Marine Biology, 95, 209215.
penguins. Previous biochemical studies on polar plankton organisms have focused on lipids to elucidate the significance of these compounds in relation to the marked seasonality of the polar light and ice regime. Due to the absence of light, phytoplankton is absent during the wintertime, and one major question concerning the functioning of the marine antarctic ecosystem is how the zooplankton, especially the herbivorous species (krill, copepods, etc.), survive during this extended period of food scarcity. There are a number of hypotheses suggesting different overwintering strategies, one of which is the use of high-energy compounds such as lipids during starvation periods. Previous investigations of the lipid biochemistry of antarctic plankton communities have been carried out for the first time by Reinhardt and Van Vleet (1986a, 1986b) and Hagen (1988) on spring and summer samples from the Antarctic Peninsula and the southern Weddell Sea. Results show high accumulation of lipid stores in many plankton organisms, particularly in crustaceans and fish; however, due to severe ice and weather conditions, very few lipid data are available from plankton 133
