Microzooplankton abundance and distribution in the ice- edge zone
Fryxell, G.A., 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., G.R. Hasle, and S.V. Carty. 1986. Thalassiosira tumida (Janisch) Hasle: Observations from field and clonal cultures. In M. Ricard (Ed.), Proceedings of the 8th Diatom Symposium 1984. Koenigstein, Germany: Koeltz Scientific Books. Garrison, D.L., K.R. Buck, and G.A. Fryxell. 1987. Algal assemblages in antarctic pack ice and in ice-edge plankton. Journal of Phycology,
AMERIEZ 1986: Microzooplankton abundance and distribution in the iceedge zone DAVID L. GARRISON and KURT
R. BUCK
Institute of Marine Sciences University of California Santa Cruz, California 95064
Microzooplankton samples were collected in the Weddell Sea during the austral fall of 1986 as part of the Antarctic Marine Ecosystem Study at the Ice-Edge Zone (AMERIEZ) study (Sullivan and Ainley, Antarctic Journal, this issue). We previously outlined our microzooplankton studies and reported our preliminary observations from this cruise (Garrison et al. 1986). Here we report the biomass, distribution, and composition of microzooplankton along a transect across the ice-edge zone from icecovered stations (USCGC Glacier stations 12-14) into open water (iIv Melville stations 17-24; see Sullivan and Ainley (Antarctic Journal, this issue) for station locations. During AMERIEZ 1986, we found that microzooplankton biomass in the upper 100 meters was low (approximately 50 milligrams of carbon per square meter) at ice-covered stations but increased to 2>300 milligrams of carbon per square meter in open water away from the ice edge (figure 1). Heterotrophic flagellates and ciliates were the most important component of the microzooplankton biomass (figure 2). Radiolarians and foraminiferans were present in low numbers and their biomass was insignificant in comparison to flagellates and ciliates in surface waters. Below 100 meters, however, the abundance of ciliates and flagellates declined markedly and phaeodarian radiolarians may have been the dominant microzooplankton (Gowing et al. 1986). The contribution of microzooplankton biomass to total zooplankton biomass was similar to the contribution by macrozooplankton and the antarctic krill, Euphausia superba (i.e., approximately 200-300 milligrams of carbon per square meter; T. Hopkins and J . Torres, University of South Florida, unpublished data). Heterotrophic flagellates, which are comprised of dinoflagellates, choanoflagellates, and small, naked flagellates, were an important component of the microzooplankton. Small, nonloricate flagellates generally accounted for >50 percent of the heterotrophic flagellate biomass, and these forms, as well as some 1987 REVIEW
23(4), 564-572.
Sullivan, C.W. 1986. Personal communication. Watkins, T.P., and G.A. Fryxell. 1986. Generic consideration of itActinocyclus: Characterization in light of three new species. Diatom Research, 1(2), 291-312,
Wood, A.M., R.S. Lande, and G.A Fryxell. 1987. A quantitative genetic analysis of variation in the valve morphology of the antarctic diatom Thalassiosira tumida (Janisch) Hasle grown at two light intensities. Journal of Phycology, 23, 42-54.
small autotrophic flagellates, appear to be underestimated in counts made on an inverted microscope as compared with counts made aboard ship by epifluorescence microscopy (see figure 2). Among the ciliates, nonloricate ciliates (e.g., Strombidum spp.) usually predominated, although tintinnids were relatively more abundant in open water and outnumbered naked forms at one open-water station (figure 3). The combined data from two AMERIEZ cruises allow us to make some preliminary comparisons of seasonality in microzooplankton abundance. During AMERIEZ 1983 which was conducted in the austral spring (November and December), we found concentrations of microzooplankton at ice-covered stations similar to those we found in the present study. In the previous study, however, maximum microzooplankton biomass reached >550 milligrams of carbon per square meter in the upper 100 meters in a well-defined maxima in association with an ice-edge plankton bloom (Garrison and Buck 1985). During both AMERIEZ cruises most of the microzooplankton biomass was concentrated in the upper 50 meters and was correlated with phytoplankton abundance suggesting that microzooplankton abundance may be closely coupled to primary production. The range of our biomass estimates from both AMERIEZ cruises falls within the ranges of microzooplankton
E
1 000 900
E
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ci)
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0 0
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If) 11)
300
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C14C13G12M17M19M21 M24 Min Ave Max v. Brockel AMERIEZ 86 Microzooplorikton
Figure 1. Microzooplankton biomass in the upper 100 meters of the water column during AMERIEZ 1986. See Sullivan and Ainley (Antarctic Journal, this issue) for station locations. Average and range of microzooplankton biomass from von Brockel (1981) are included for comparison. ("m" denotes "meter:' "mgC;s, 2" denotes "milligrams of carbon per square meter:')
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M c'c' > I o ° a 5• CD " 0 0 a '-'- CD -t.. -4, -4, Q -i CD CD0 a- a- o 0 0 ()) CD CD .0 0 = = CD (0 0 M Lo g. CD CD '- = CD j-.- a Ci) CD (I) CD w CD Cl,
Figure 2. Composition of microplankton at stations G14, G12, and M24. Bacteria and diatom biomass not available. Biomass estimates of autotrophic and heterotrophic flagellates determined from examining preserved and settled samples vs. (shipboard) counts are compared. ("m" denotes" meter." "mgC;s, 2" denotes milligrams of carbon per square meter:')
biomass that von Brokel (1981) reported during the austral summer of 1978 (see figure 1), so that spatial heterogeneity in microzooplankton abundance appears to be as large as seasonal changes. During 1987 and 1988 we will have the opportunity to examine the abundance of microzooplankton during the austral winter as part of our continuing study. This study was supported by National Science Foundation grant DPP 84-20184 to D.L. Garrison.
AMERIEZ 1986: Acoustic assessment of krill (Euphausia superba, Dana) M.C. MACAULAY
Applied Physics Laboratory University of Washington Seattle, Washington 98105 K.L. DALY, and
B.W. FROST
School of Oceanography University of Washington Seattle, Washington 98105
As a component of the Antarctic Marine Ecosystem Research at the Ice-Edge Zone (AMERIEZ) program, the abundance and distribution of micronekton and nekton at the ice edge was 176
m
C
o 0 -o 0 0
C14 C13 012 M17 M19 M21 M24 AMERIEZ 86
Figure 3. Biomass of cilated protozoans in upper 100 meters during AMERIEZ 1986. ("m" denotes "meter:' "mgC;s, 2" denotes "milligrams of carbon per square meter:')
References Garrison, D.L., M.M. Cowing, K.R. Buck, S.L. Coale, and H.A. Thomsen. 1986. Micro heterotrophs in the ice edge zone: An AMERIEZ study. Antarctic Journal of the U.S., 21(5), 169-171. Garrison, D. L., and K. R. Buck. 1985. Microheterotrophs in the ice edge zone: An AMERIEZ study. Antarctic Journal of the U.S., 20(5), 136-137. Cowing, M.M., D.L. Garrison, S.L. Coale, and K.R. Buck. 1986. Preliminary data on the distribution and trophic ecology of phaeodanan radiolarians from the Weddell Sea: An AMERIEZ study. EOS, 67, 990. Sullivan, C.W., and D. Ainley. 1987. AMERIEZ 1986: A summary of activities on board the iIv Melville and LJSCGC Glacier. Antarctic Journal of the U.S., 22(5). von Brokel, K. 1981. The importance of nanoplankton within the pelagic Antarctic ecosystem. Kieler Meeresforschungen Sonderheit, 5, 6-67.
investigated by acoustic and net sampling methods in the western Weddell Sea during late austral summer 1986. During field operations, hydroacoustic measurements and net samples were taken 7 March to 29 March 1986. The data were obtained using two frequencies (50 kilohertz and 200 kilohertz) echo sounders operating simultaneously on Melville and one frequency (120 kilohertz) on Glacier. The transducers were mounted in a 1.2-meter V-fin depressor and towed behind the ship on Melville and deployed by float (on station only) on Glacier. In conjunction with the acoustic program on Glacier, vertical plummet net tows were made at every station for target identification, life-history stages, and length-frequency information. Similar data were collected from samples taken by other components aboard Melville. Data analysis. Data collection and analysis have been described earlier (Macaulay, English, and Mathisen 1984; Daly and Macaulay in press). All recorded data were analyzed by echointegration methods to produce estimates of biomass (where acoustic targets were identified) or mean-volume-backscattering-strength (where uncertain or unknown targets were presANTARCTIC JOURNAL
AMERIEZ 1986: Microzooplankton abundance and distribution in the iceedge zone DAVID L. GARRISON and KURT
R. BUCK
Institute of Marine Sciences University of California Santa Cruz, California 95064
Microzooplankton samples were collected in the Weddell Sea during the austral fall of 1986 as part of the Antarctic Marine Ecosystem Study at the Ice-Edge Zone (AMERIEZ) study (Sullivan and Ainley, Antarctic Journal, this issue). We previously outlined our microzooplankton studies and reported our preliminary observations from this cruise (Garrison et al. 1986). Here we report the biomass, distribution, and composition of microzooplankton along a transect across the ice-edge zone from icecovered stations (USCGC Glacier stations 12-14) into open water (iIv Melville stations 17-24; see Sullivan and Ainley (Antarctic Journal, this issue) for station locations. During AMERIEZ 1986, we found that microzooplankton biomass in the upper 100 meters was low (approximately 50 milligrams of carbon per square meter) at ice-covered stations but increased to 2>300 milligrams of carbon per square meter in open water away from the ice edge (figure 1). Heterotrophic flagellates and ciliates were the most important component of the microzooplankton biomass (figure 2). Radiolarians and foraminiferans were present in low numbers and their biomass was insignificant in comparison to flagellates and ciliates in surface waters. Below 100 meters, however, the abundance of ciliates and flagellates declined markedly and phaeodarian radiolarians may have been the dominant microzooplankton (Gowing et al. 1986). The contribution of microzooplankton biomass to total zooplankton biomass was similar to the contribution by macrozooplankton and the antarctic krill, Euphausia superba (i.e., approximately 200-300 milligrams of carbon per square meter; T. Hopkins and J . Torres, University of South Florida, unpublished data). Heterotrophic flagellates, which are comprised of dinoflagellates, choanoflagellates, and small, naked flagellates, were an important component of the microzooplankton. Small, nonloricate flagellates generally accounted for >50 percent of the heterotrophic flagellate biomass, and these forms, as well as some 1987 REVIEW
23(4), 564-572.
Sullivan, C.W. 1986. Personal communication. Watkins, T.P., and G.A. Fryxell. 1986. Generic consideration of itActinocyclus: Characterization in light of three new species. Diatom Research, 1(2), 291-312,
Wood, A.M., R.S. Lande, and G.A Fryxell. 1987. A quantitative genetic analysis of variation in the valve morphology of the antarctic diatom Thalassiosira tumida (Janisch) Hasle grown at two light intensities. Journal of Phycology, 23, 42-54.
small autotrophic flagellates, appear to be underestimated in counts made on an inverted microscope as compared with counts made aboard ship by epifluorescence microscopy (see figure 2). Among the ciliates, nonloricate ciliates (e.g., Strombidum spp.) usually predominated, although tintinnids were relatively more abundant in open water and outnumbered naked forms at one open-water station (figure 3). The combined data from two AMERIEZ cruises allow us to make some preliminary comparisons of seasonality in microzooplankton abundance. During AMERIEZ 1983 which was conducted in the austral spring (November and December), we found concentrations of microzooplankton at ice-covered stations similar to those we found in the present study. In the previous study, however, maximum microzooplankton biomass reached >550 milligrams of carbon per square meter in the upper 100 meters in a well-defined maxima in association with an ice-edge plankton bloom (Garrison and Buck 1985). During both AMERIEZ cruises most of the microzooplankton biomass was concentrated in the upper 50 meters and was correlated with phytoplankton abundance suggesting that microzooplankton abundance may be closely coupled to primary production. The range of our biomass estimates from both AMERIEZ cruises falls within the ranges of microzooplankton
E
1 000 900
E
800
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700
ci)
500
0 0
ci
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If) 11)
300
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200
m
100
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0 0 C-)
C14C13G12M17M19M21 M24 Min Ave Max v. Brockel AMERIEZ 86 Microzooplorikton
Figure 1. Microzooplankton biomass in the upper 100 meters of the water column during AMERIEZ 1986. See Sullivan and Ainley (Antarctic Journal, this issue) for station locations. Average and range of microzooplankton biomass from von Brockel (1981) are included for comparison. ("m" denotes "meter:' "mgC;s, 2" denotes "milligrams of carbon per square meter:')
175
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M c'c' > I o ° a 5• CD " 0 0 a '-'- CD -t.. -4, -4, Q -i CD CD0 a- a- o 0 0 ()) CD CD .0 0 = = CD (0 0 M Lo g. CD CD '- = CD j-.- a Ci) CD (I) CD w CD Cl,
Figure 2. Composition of microplankton at stations G14, G12, and M24. Bacteria and diatom biomass not available. Biomass estimates of autotrophic and heterotrophic flagellates determined from examining preserved and settled samples vs. (shipboard) counts are compared. ("m" denotes" meter." "mgC;s, 2" denotes milligrams of carbon per square meter:')
biomass that von Brokel (1981) reported during the austral summer of 1978 (see figure 1), so that spatial heterogeneity in microzooplankton abundance appears to be as large as seasonal changes. During 1987 and 1988 we will have the opportunity to examine the abundance of microzooplankton during the austral winter as part of our continuing study. This study was supported by National Science Foundation grant DPP 84-20184 to D.L. Garrison.
AMERIEZ 1986: Acoustic assessment of krill (Euphausia superba, Dana) M.C. MACAULAY
Applied Physics Laboratory University of Washington Seattle, Washington 98105 K.L. DALY, and
B.W. FROST
School of Oceanography University of Washington Seattle, Washington 98105
As a component of the Antarctic Marine Ecosystem Research at the Ice-Edge Zone (AMERIEZ) program, the abundance and distribution of micronekton and nekton at the ice edge was 176
m
C
o 0 -o 0 0
C14 C13 012 M17 M19 M21 M24 AMERIEZ 86
Figure 3. Biomass of cilated protozoans in upper 100 meters during AMERIEZ 1986. ("m" denotes "meter:' "mgC;s, 2" denotes "milligrams of carbon per square meter:')
References Garrison, D.L., M.M. Cowing, K.R. Buck, S.L. Coale, and H.A. Thomsen. 1986. Micro heterotrophs in the ice edge zone: An AMERIEZ study. Antarctic Journal of the U.S., 21(5), 169-171. Garrison, D. L., and K. R. Buck. 1985. Microheterotrophs in the ice edge zone: An AMERIEZ study. Antarctic Journal of the U.S., 20(5), 136-137. Cowing, M.M., D.L. Garrison, S.L. Coale, and K.R. Buck. 1986. Preliminary data on the distribution and trophic ecology of phaeodanan radiolarians from the Weddell Sea: An AMERIEZ study. EOS, 67, 990. Sullivan, C.W., and D. Ainley. 1987. AMERIEZ 1986: A summary of activities on board the iIv Melville and LJSCGC Glacier. Antarctic Journal of the U.S., 22(5). von Brokel, K. 1981. The importance of nanoplankton within the pelagic Antarctic ecosystem. Kieler Meeresforschungen Sonderheit, 5, 6-67.
investigated by acoustic and net sampling methods in the western Weddell Sea during late austral summer 1986. During field operations, hydroacoustic measurements and net samples were taken 7 March to 29 March 1986. The data were obtained using two frequencies (50 kilohertz and 200 kilohertz) echo sounders operating simultaneously on Melville and one frequency (120 kilohertz) on Glacier. The transducers were mounted in a 1.2-meter V-fin depressor and towed behind the ship on Melville and deployed by float (on station only) on Glacier. In conjunction with the acoustic program on Glacier, vertical plummet net tows were made at every station for target identification, life-history stages, and length-frequency information. Similar data were collected from samples taken by other components aboard Melville. Data analysis. Data collection and analysis have been described earlier (Macaulay, English, and Mathisen 1984; Daly and Macaulay in press). All recorded data were analyzed by echointegration methods to produce estimates of biomass (where acoustic targets were identified) or mean-volume-backscattering-strength (where uncertain or unknown targets were presANTARCTIC JOURNAL
